Sky

Sky From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Sky (disambiguation). Rays of light clouds near the Monument in

shining through Washington Washington D.C.

When seen from from an airplane, varies from pale approaching the

altitude, as here the sky's color to dark at elevations zenith

Turbulent skies The sky's zenith appears centered in this daytime photograph taken looking up though trees Clouds made orange by a

sunset

The sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a deep blue surface because of the air's scattering of [1][2][3][4] sunlight. The sky is sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars. During the day the Sun can be seen in the sky, unless covered by clouds. In the night sky (and to some extent during the day) the moon, planets and stars are visible in the sky. Some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky during storms. On Earth, birds, insects, aircraft, and kites are often considered to fly in the sky. As a result of human activities, smog during the day and light radiance during the night are often seen above large cities (see also light pollution). In the field of astronomy, the sky is also called the celestial sphere. This is an imaginary dome where the sun, stars, planets, and the moon are seen to be travelling. The celestial sphere is divided into regions called constellations.

Contents • • •

1 Sky luminance and colors 2 See also 3 References

•

4 External links

See skies of other planets for descriptions of the skies of various planets and moons in the solar system.

[edit] Sky luminance and colors

The light from the sky is a result of the scattering of sunlight, which results in a blue color perceived by the human eye. On a sunny day Rayleigh Scattering gives the sky a blue gradient — dark in the zenith, light near the horizon. Light that comes in from overhead encounters 1/38th of the air mass that light coming along a horizon path encounters. So, fewer particles scatter the zenith sunbeam, and therefore the light remains a darker blue.[5] The sky can turn a multitude of colors such as red, orange and yellow (especially near sunset or sunrise) and black at night. Scattering effects also partially polarize light from the sky. Sky luminance distribution models have been recommended by the International Commission on Illumination (CIE) for the design of daylighting schemes. Recent developments relate to “all sky models” for modelling sky luminance under weather conditions ranging from clear sky to overcast.[6]

[edit] See also • • • •

Air Diffuse sky radiation Sky brightness skygazing

Earth's atmosphere From Wikipedia, the free encyclopedia

(Redirected from Air) Jump to: navigation, search "Air" redirects here. For other Atmospheric gases scatter blue light more than other wavelengths, giving the Earth a blue halo when seen from space

Components dry air Nitrogen

of (volume)

78.0842%

Oxygen

20.9463%

Argon

0.9342%

Carbon dioxide

0.0384%

Other

0.0020%

Earth's atmosphere From Wikipedia, the free encyclopedia

(Redirected from Air) Jump to: navigation, search "Air" redirects here. For other uses, see Air (disambiguation). Layers of the atmosphere (not to scale) The Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth's gravity. Dry air contains roughly (by molar content – equivalent to volume, for gases) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, and trace amounts of other gases; but air also contains a variable amount of water vapor, on average around 1%. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night.

There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space.

Contents [hide] • • • • • •

• • •

1 Temperature and layers 2 Pressure and thickness 3 Composition o 3.1 Heterosphere 4 Density and mass 5 Opacity 6 Evolution of Earth's Atmosphere o 6.1 Air pollution o 6.2 Kyoto Protocol 7 See also 8 References

[edit] Temperature and layers The temperature of the Earth's atmosphere varies with altitude; the mathematical relationship between temperature and altitude varies among five different atmospheric layers (ordered highest to lowest, the ionosphere is part of the thermosphere): •

Exosphere: from 500 – 1000 km (300 – 600 mi) up to 10,000 km (6,000 mi), free-moving particles that may migrate into and out of the magnetosphere or the solar wind.

exobase boundary

Ionosphere: the part of the atmosphere that is ionized by solar radiation. It plays an important part in 9 External links atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is located in the thermosphere and is responsible for auroras. •

thermopause boundary •

Thermosphere: from 80 – 85 km (265,000 – 285,000 ft) to 640+ km (400+ mi), temperature increasing with height.

mesopause boundary •

Mesosphere: From the Greek word "μέσος" meaning middle. The mesosphere extends from about 50 km (160,000 ft) to the range of 80 to 85 km (265,000 – 285,000 ft), temperature decreasing with height. This is also where most meteors burn up when entering the atmosphere.

stratopause boundary •

Stratosphere: From the Latin word "stratus" meaning a spreading out. The stratosphere extends from the troposphere's 7 to 17 km (23,000 – 60,000 ft) range to about 50 km (160,000 ft). Temperature increases with height. The stratosphere contains the ozone layer, the part of the Earth's atmosphere which contains relatively high concentrations of ozone. "Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 to 35 km (50,000 – 115,000 ft) above Earth's surface, though the thickness varies seasonally and geographically.

tropopause boundary

•

Troposphere: From the Greek word "τρέπω" meaning to turn or change. The troposphere is the lowest layer of the atmosphere; it begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (60,000 ft) at the equator, with some variation due to weather factors. The troposphere has a great deal of vertical mixing because of solar heating at the surface. This heating warms air masses, which makes them less dense so they rise. When an air mass rises, the pressure upon it decreases so it expands, doing work against the opposing pressure of the surrounding air. To do work is to expend energy, so the temperature of the air mass decreases. As the temperature decreases, water vapor in the air mass may condense or solidify, releasing latent heat that further uplifts the air mass. This process determines the maximum rate of decline of temperature with height, called the adiabatic lapse rate. The troposphere contains roughly 80% of the total mass of the atmosphere. Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km of the troposphere.

The average temperature of the atmosphere at the surface of Earth is 15 °C (59 °F).[1][2]

[edit] Pressure and thickness Main article: Atmospheric pressure Barometric Formula: (used for airplane flight) barometric formula One mathematical model: NRLMSISE-00 The average atmospheric pressure, at sea level, is about 101.3 kilopascals (about 14.7 psi); total atmospheric mass is 5.1480×1018 kg [3]. Atmospheric pressure is a direct result of the total weight of the air above the point at which the pressure is measured. This means that air pressure varies with location and time, because the amount (and weight) of air above the earth varies with location and time. However the average mass of the air above a square meter of the earth's surface is known to the same high accuracy as the total air mass of 5148.0 teratonnes and area of the earth of 51007.2 megahectares, namely 5148.0/510.072 = 10.093 metric tonnes per square meter or 14.356 lbs (mass) per square inch. This is about 2.5% below the officially standardized unit atmosphere (1 atm) of 101.325 kPa or 14.696 psi, and corresponds to the mean pressure not at sea level but at the mean base of the atmosphere as contoured by the earth's terrain. Were atmospheric density to remain constant with height the atmosphere would terminate abruptly at 7.81 km (25,600 ft). Instead it decreases with height, dropping by 50% at an altitude of about 5.6 km (18,000 ft). For comparison: the highest mountain, Mount Everest, is higher, at 8.8 km, which is why it is so difficult to climb without supplemental oxygen. This pressure drop is approximately exponential, so that pressure decreases by approximately half every 5.6 km (whence about 50% of the total atmospheric mass is within the lowest 5.6 km) and by 63.2 % (1 − 1 / e = 1 − 0.368 = 0.632) every 7.64 km, the average scale height of Earth's atmosphere below 70 km. However, because of changes in temperature, average molecular weight, and gravity throughout the atmospheric column, the dependence of atmospheric pressure on altitude is modeled by separate equations for each of the layers listed above. Even in the exosphere, the atmosphere is still present (as can be seen for example by the effects of atmospheric drag on satellites). The equations of pressure by altitude in the above references can be used directly to estimate atmospheric thickness. However, the following published data are given for reference: [4] •

50% of the atmosphere by mass is below an altitude of 5.6 km.

• •

90% of the atmosphere by mass is below an altitude of 16 km. The common altitude of commercial airliners is about 10 km. 99.99997% of the atmosphere by mass is below 100 km. The highest X-15 plane flight in 1963 reached an altitude of 354,300 ft (108.0 km).

Therefore, most of the atmosphere (99.9997%) is below 100 km, although in the rarefied region above this there are auroras and other atmospheric effects.

[edit] Composition Filtered air includes at least trace amounts of ten (or more) of the chemical elements. Substantial amounts of argon, nitrogen, and oxygen are present as elementary gases, as well as hydrogen (and additional oxygen) in water vapor (H2O). Much smaller or trace amounts of elementary helium, hydrogen, iodine, krypton, neon, and xenon are also present, as well as carbon in carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO). Many additional elements from natural sources may be present in tiny amounts in an unfiltered air sample, including contributions from dust, pollen and spores, sea spray, vulcanism, and meteoroids. Various industrial pollutants are also now present in the air, such as chlorine (elementary or in compounds), fluorine (in compounds), elementary mercury, and sulfur (in compounds such as sulfur dioxide [SO2]).

Composition of Earth's atmosphere as of Dec. 1987. The lower pie represents the least common gases that compose 0.038% of the atmosphere. Values normalized for illustration. Mean atmospheric water vapor Composition dry atmosphere, by volume[5] ppmv: parts per million by volume

Gas

Volume

Nitrogen 780,840 ppmv (78.084%) (N2) Oxygen (O2)

209,460 ppmv (20.946%)

Argon (Ar)

9,340 ppmv (0.9340%)

of

Carbon dioxide (CO2)

383 ppmv (0.0383%)

Neon (Ne)

18.18 ppmv (0.001818%)

Helium (He)

5.24 ppmv (0.000524%)

Methane 1.745 ppmv (0.0001745%) (CH4) Krypton 1.14 ppmv (0.000114%) (Kr) Hydrogen 0.55 ppmv (0.000055%) (H2) Not included in above dry atmosphere: Water vapor (H2O)

~0.40% over full atmosphere, typically 1% to 4% near surface

Minor components of air not listed above include[citation needed] Gas

Volume

nitrous oxide

0.3 ppmv (0.00003%)

xenon

0.09 ppmv (9x10-6%)

ozone

0.0 to 0.07 ppmv (0%-7x10-6%)

nitrogen 0.02 ppmv (2x10-6%) dioxide iodine

0.01 ppmv (1x10-6%)

carbon trace monoxide ammonia trace ppmv The composition figures above are by volume-fraction (V%), which for ideal gases is equal to mole-fraction (that is, the fraction of total molecules). Although the atmosphere is not an ideal gas, nonetheless the atmosphere behaves enough like an ideal gas that the volume-fraction is the same as the mole-fraction for the precision given. By contrast, mass-fraction abundances of gases will differ from the volume values. The mean molar mass of air is 28.97 g/mol, while the molar mass of helium is 4.00, and krypton is 83.80. Thus helium is 5.2 ppm by volume-fraction, but 0.72 ppm by mass-fraction ([4/29] × 5.2 = 0.72), and krypton is 1.1 ppm by volume-fraction, but 3.2 ppm by mass-fraction ([84/29] × 1.1 = 3.2).

[edit] Heterosphere Below the turbopause at an altitude of about 100 km (not far from the mesopause), the Earth's atmosphere has a more-or-less uniform composition (apart from water vapor) as described above; this constitutes the homosphere.[6] However, above about 100 km, the Earth's atmosphere begins to have a composition which varies with altitude. This is essentially because, in the absence of mixing, the density of a gas falls off exponentially with increasing altitude but at a rate which depends on the molar mass. Thus higher mass constituents, such as oxygen and nitrogen, fall off more quickly than lighter constituents such as helium, molecular hydrogen, and atomic hydrogen. Thus there is a layer, called the heterosphere, in which the earth's atmosphere has varying composition. As the altitude increases, the atmosphere is dominated successively by helium, molecular hydrogen, and atomic hydrogen. The precise altitude of the heterosphere and the layers it contains varies significantly with temperature. In pre-history, the Sun's radiation caused a loss of the hydrogen, helium and other hydrogen-containing gases from early Earth, and Earth was devoid of an atmosphere. The first atmosphere was formed by outgassing of gases trapped in the interior of the early Earth, which still goes on today in volcanoes.[7]

[edit] Density and mass Earth's atmosphere from space

Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model The density of air at sea level is about 1.2 kg/m3 (1.2 g/L). Natural variations of the barometric pressure occur at any one altitude as a consequence of weather. This variation is relatively small for inhabited altitudes but much more pronounced in the outer atmosphere and space because of variable solar radiation. The atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used by meteorologists and space agencies to predict weather and orbital decay of satellites. The average mass of the atmosphere is about 5 quadrillion metric tons or 1/1,200,000 the mass of Earth. According to the National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg."

[edit] Opacity Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light The atmosphere has "windows" of low opacity, allowing the transmission of electromagnetic radiation. The optical window runs from around 300 nanometers (ultraviolet-C) at the short end up into the range the eye can use, the visible spectrum at roughly 400–700 nm, and continues up through the visual infrared to around 1100 nm, which is thermal infrared. There are also infrared and radio windows that transmit some infrared and radio waves. The radio window runs from about one centimeter to about eleven-meter waves.

[edit] Evolution of Earth's Atmosphere See also: History of Earth and Gaia hypothesis The history of the Earth's atmosphere prior to one billion years ago is poorly understood and an active area of scientific research. The following discussion presents a plausible scenario. The modern atmosphere is sometimes referred to as Earth's "third atmosphere", in order to distinguish the current chemical composition from two notably different previous compositions. The original atmosphere was primarily helium and hydrogen. Heat from the still-molten crust, and the sun, plus a probably enhanced solar wind, dissipated this atmosphere. About 4.4 billion years ago, the surface had cooled enough to form a crust, still heavily populated with volcanoes which released steam, carbon dioxide, and ammonia. This led to the early "second atmosphere", which was primarily carbon dioxide and water vapor, with some nitrogen but virtually no oxygen. This second atmosphere had approximately 100 times as much gas as the current atmosphere, but

as it cooled much of the carbon dioxide was dissolved in the seas and precipitated out as carbonates. The later "second atmosphere" contained largely nitrogen and carbon dioxide. However, simulations run at the University of Waterloo and University of Colorado in 2005 suggest that it may have had up to 40% hydrogen.[8] It is generally believed that the greenhouse effect, caused by high levels of carbon dioxide and methane, kept the Earth from freezing. One of the earliest types of bacteria was the cyanobacteria. Fossil evidence indicates that bacteria shaped like these existed approximately 3.3 billion years ago and were the first oxygen-producing evolving phototropic organisms. They were responsible for the initial conversion of the earth's atmosphere from an anoxic state to an oxic state (that is, from a state without oxygen to a state with oxygen) during the period 2.7 to 2.2 billion years ago. Being the first to carry out oxygenic photosynthesis, they were able to produce oxygen while sequestering carbon dioxide in organic molecules, playing a major role in oxygenating the atmosphere. Photosynthesising plants later evolved and continued releasing oxygen and sequestering carbon dioxide. Over time, excess carbon became locked in fossil fuels, sedimentary rocks (notably limestone), and animal shells. As oxygen was released, it reacted with ammonia to release nitrogen; in addition, bacteria would also convert ammonia into nitrogen. But most of the nitrogen currently present in the atmosphere results from sunlight-powered photolysis of ammonia released steadily over the aeons from volcanoes. As more plants appeared, the levels of oxygen increased significantly, while carbon dioxide levels dropped. At first the oxygen combined with various elements (such as iron), but eventually oxygen accumulated in the atmosphere, contributing to Cambrian explosion and further evolution. With the appearance of an ozone layer (ozone is an allotrope of oxygen) lifeforms were better protected from ultraviolet radiation. This oxygen-nitrogen atmosphere is the "third atmosphere". Between 200 and 250 million years ago, up to 35% of the atmosphere was oxygen (as found in bubbles of ancient atmosphere preserved in amber). This modern atmosphere has a composition which is enforced by oceanic blue-green algae as well as geological processes. O2 does not remain naturally free in an atmosphere but tends to be consumed (by inorganic chemical reactions, and by animals, bacteria, and even land plants at night), and CO 2 tends to be produced by respiration and decomposition and oxidation of organic matter. Oxygen would vanish within a few million years by chemical reactions, and CO2 dissolves easily in water and would be gone in millennia if not replaced. Both are maintained by biological productivity and geological forces seemingly working hand-in-hand to maintain reasonably steady levels over millions of years. Currently, anthropogenic greenhouse gases are increasing in the atmosphere and this is a causative factor in global warming.[9]

[edit] Air pollution

Before desulfurization filters were installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide. Main article: Air pollution Air pollution is the human introduction into the atmosphere of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the environment.[10] Stratospheric ozone depletion is believed to be caused by air pollution (chiefly from chlorofluorocarbons)

Worldwide air pollution is responsible for large numbers of deaths and cases of respiratory disease. Enforced air quality standards, like the Clean Air Act in the United States, have reduced the presence of some pollutants. While major stationary sources are often identified with air pollution, the greatest source of emissions is actually mobile sources, principally the automobile[citation needed]. Gases such as carbon dioxide, methane, and fluorocarbons contribute to global warming, and these gases, or excess amounts of some emitted from fossil fuel burning, have recently been identified by the United States and many other countries as pollutants.[citation needed]

[edit] Kyoto Protocol

Participation in the Kyoto Protocol, where dark green indicates countries that have signed and ratified the treaty, yellow is signed, but not yet ratified, grey is not yet decided and red is no intention of ratifying. As of April 2008, 178 states have signed and ratified the Kyoto Protocol to the United Nations Framework Convention on Climate Change, aimed at combating global warming. The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing greenhouse gases in an effort to prevent anthropogenic climate change. It was adopted for use on 11 December 1997 by the 3rd Conference of the Parties, which was meeting in Kyoto, and it entered into force on 16 February 2005. As of May 2008, 182 parties have ratified the protocol.[11] Of these, 36 developed C.G. countries (plus the EU as a party in its own right) are required to reduce greenhouse gas emissions to the levels specified for each of them in the treaty (representing over 61.6% of emissions from Annex I countries),[11][12] with three more countries intending to participate.[13] One hundred thirty-seven (137) developing countries have ratified the protocol, including Brazil, China and India, but have no obligation beyond monitoring and reporting emissions. The United States is the only developed and industrialized western country that has not ratified the treaty but it is one of the significant greenhouse gas emitters.

[edit] See also Atmosphere portal • • • • • • • • • • • • • • • •

Aerial perspective Air glow Airshed Atmosphere (for information on atmospheres in general) Atmospheric chemistry Atmospheric dispersion modeling Atmospheric electricity Atmospheric models Atmospheric Radiation Measurement (ARM) (in the U.S.) Atmospheric stratification Aviation Biosphere Compressed air Global dimming Historical temperature record Hydrosphere

• • •

Intergovernmental Panel on Climate Change Lithosphere US Standard Atmosphere

Star From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the astronomical object. For other uses, see Star (disambiguation). The Pleiades, an open cluster of stars in the constellation of Taurus. NASA photo A star is a massive, luminous ball of plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. For most of its life, a star shines due to thermonuclear fusion in its core releasing energy that traverses the star's interior and then radiates into outer space. Almost all elements heavier than hydrogen and helium were created by fusion processes in stars.

Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including the diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung-Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined. A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion.[1] The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, those stars having at least 0.4 times the mass of the Sun[2] expand to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of the matter into the interstellar environment, where it will form a new generation of stars with a higher proportion of heavy elements.[3] Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution.[4] Stars can form part of a much larger gravitationally bound structure, such as a cluster or a galaxy.

Contents [hide] • • • • • • • • • • • • • •

1 Observation history 2 Star designations 3 Units of measurement 4 Formation and evolution 5 Distribution 6 Characteristics 7 Radiation 8 Classification 9 Variable stars 10 Structure 11 Nuclear fusion reaction pathways 12 See also 13 References 14 Further reading

Observation history Historically, stars have been important to civilizations throughout the world. They have been used in religious practices and for celestial navigation and orientation. Many ancient astronomers believed that stars were permanently affixed to a heavenly sphere, and that they were immutable. By convention, astronomers grouped stars into constellations and used them to track the motions of the planets and the inferred position of the Sun.[5] The motion of the Sun against the background stars (and the horizon) was used to create calendars, which could be used to regulate agricultural practices.[6] The Gregorian calendar, currently used nearly everywhere in the world, is a solar calendar based on the angle of the Earth's rotational axis relative to the nearest star, the Sun.

The oldest accurately dated star chart appeared in Ancient Egypt in 1,534 BCE.[7] Islamic astronomers gave to many stars Arabic names which are still used today, and they • 15 External links invented numerous astronomical instruments which could compute the positions of the stars. In the 11th century, Abū Rayhān al-Bīrūnī described the Milky Way galaxy as multitude of fragments having the properties of nebulous stars, and also gave the latitudes of various stars during a lunar eclipse in 1019.[8] In spite of the apparent immutability of the heavens, Chinese astronomers were aware that new stars could appear.[9] Early European astronomers such as Tycho Brahe identified new stars in the night sky (later termed novae), suggesting that the heavens were not immutable. In 1584 Giordano Bruno suggested that the stars were actually other suns, and may have other planets, possibly even Earth-like, in orbit around

them,[10] an idea that had been suggested earlier by such ancient Greek philosophers as Democritus and Epicurus.[11] By the following century the idea of the stars as distant suns was reaching a consensus among astronomers. To explain why these stars exerted no net gravitational pull on the solar system, Isaac Newton suggested that the stars were equally distributed in every direction, an idea prompted by the theologian Richard Bentley.[12] The Italian astronomer Geminiano Montanari recorded observing variations in luminosity of the star Algol in 1667. Edmond Halley published the first measurements of the proper motion of a pair of nearby "fixed" stars, demonstrating that they had changed positions from the time of the ancient Greek astronomers Ptolemy and Hipparchus. The first direct measurement of the distance to a star (61 Cygni at 11.4 light-years) was made in 1838 by Friedrich Bessel using the parallax technique. Parallax measurements demonstrated the vast separation of the stars in the heavens.[10] William Herschel was the first astronomer to attempt to determine the distribution of stars in the sky. During the 1780s, he performed a series of gauges in 600 directions, and counted the stars observed along each line of sight. From this he deduced that the number of stars steadily increased toward one side of the sky, in the direction of the Milky Way core. His son John Herschel repeated this study in the southern hemisphere and found a corresponding increase in the same direction.[13] In addition to his other accomplishments, William Herschel is also noted for his discovery that some stars do not merely lie along the same line of sight, but are also physical companions that form binary star systems. The science of stellar spectroscopy was pioneered by Joseph von Fraunhofer and Angelo Secchi. By comparing the spectra of stars such as Sirius to the Sun, they found differences in the strength and number of their absorption lines—the dark lines in a stellar spectra due to the absorption of specific frequencies by the atmosphere. In 1865 Secchi began classifying stars into spectral types.[14] However, the modern version of the stellar classification scheme was developed by Annie J. Cannon during the 1900s. Observation of double stars gained increasing importance during the 19th century. In 1834, Friedrich Bessel observed changes in the proper motion of the star Sirius, and inferred a hidden companion. Edward Pickering discovered the first spectroscopic binary in 1899 when he observed the periodic splitting of the spectral lines of the star Mizar in a 104 day period. Detailed observations of many binary star systems were collected by astronomers such as William Struve and S. W. Burnham, allowing the masses of stars to be determined from computation of the orbital elements. The first solution to the problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827.[15] The twentieth century saw increasingly rapid advances in the scientific study of stars. The photograph became a valuable astronomical tool. Karl Schwarzschild discovered that the color of a star, and hence its temperature, could be determined by comparing the visual magnitude against the photographic magnitude. The development of the photoelectric photometer allowed very precise measurements of magnitude at multiple wavelength intervals. In 1921 Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope.[16] Important conceptual work on the physical basis of stars occurred during the first decades of the twentieth century. In 1913, the Hertzsprung-Russell diagram was developed, propelling the astrophysical study of stars. Successful models were developed to explain the interiors of stars and stellar evolution. The spectra of stars were also successfully explained through advances in quantum physics. This allowed the chemical composition of the stellar atmosphere to be determined.[17] With the exception of supernovae, individual stars have primarily been observed in our Local Group of galaxies,[18] and especially in the visible part of the Milky Way (as demonstrated by the detailed star catalogues available for our galaxy[19]). But some stars have been observed in the M100 galaxy of the Virgo Cluster, about 100 million light years from the Earth.[20] In the Local Supercluster it is possible to

see star clusters, and current telescopes could in principle observe faint individual stars in the Local Cluster—the most distant stars resolved have up to hundred million light years away[21] (see Cepheids). However, outside the Local Supercluster of galaxies, neither individual stars nor clusters of stars have been observed. The only exception is a faint image of a large star cluster containing hundreds of thousands of stars located one billion light years away[22]—ten times the distance of the most distant star cluster previously observed.

Star designations Main articles: Star designation, Astronomical naming conventions, and Star catalogue The concept of the constellation was known to exist during the Babylonian period. Ancient sky watchers imagined that prominent arrangements of stars formed patterns, and they associated these with particular aspects of nature or their myths. Twelve of these formations lay along the band of the ecliptic and these became the basis of astrology. Many of the more prominent individual stars were also given names, particularly with Arabic or Latin designations. As well as certain constellations and the Sun itself, stars as a whole have their own myths.[23] They were thought to be the souls of the dead or gods. An example is the star Algol, which was thought to represent the eye of the Gorgon Medusa. To the Ancient Greeks, some "stars," known as planets (Greek πλανήτης (planētēs), meaning "wanderer"), represented various important deities, from which the names of the planets Mercury, Venus, Mars, Jupiter and Saturn were taken.[23] (Uranus and Neptune were also Greek and Roman gods, but neither planet was known in Antiquity because of their low brightness. Their names were assigned by later astronomers). Circa 1600, the names of the constellations were used to name the stars in the corresponding regions of the sky. The German astronomer Johann Bayer created a series of star maps and applied Greek letters as designations to the stars in each constellation. Later the English astronomer John Flamsteed came up with a system using numbers, which would later be known as the Flamsteed designation. Numerous additional systems have since been created as star catalogues have appeared. The only body which has been recognized by the scientific community as having the authority to name stars or other celestial bodies is the International Astronomical Union (IAU).[24] A number of private companies (for instance, the "International Star Registry") purport to sell names to stars; however, these names are neither recognized by the scientific community nor used by them, [24] and many in the astronomy community view these organizations as frauds preying on people ignorant of star naming procedure.[25]

Units of measurement Most stellar parameters are expressed in SI units by convention, but CGS units are also used (e.g., expressing luminosity in ergs per second). Mass, luminosity, and radii are usually given in solar units, based on the characteristics of the Sun: solar mass: kg[26] solar luminosity: watts[26] solar radius: m[27]

Large lengths, such as the radius of a giant star or the semi-major axis of a binary star system, are often expressed in terms of the astronomical unit (AU)—approximately the mean distance between the Earth and the Sun (150 million km or 93 million miles).

Formation and evolution Main article: Stellar evolution Stars are formed within extended regions of higher density in the interstellar medium, although the density is still lower than the inside of an earthly vacuum chamber. These regions are called molecular clouds and consist mostly of hydrogen, with about 23–28% helium and a few percent heavier elements. One example of such a star-forming region is the Orion Nebula.[28] As massive stars are formed from molecular clouds, they powerfully illuminate those clouds. They also ionize the hydrogen, creating an H II region.

Protostar formation Main article: Star formation The formation of a star begins with a gravitational instability inside a molecular cloud, often triggered by shockwaves from supernovae (massive stellar explosions) or the collision of two galaxies (as in a starburst galaxy). Once a region reaches a sufficient density of matter to satisfy the criteria for Jeans Instability it begins to collapse under its own gravitational force.

Artist's conception of the birth of a star within a dense molecular cloud. NASA image As the cloud collapses, individual conglomerations of dense dust and gas form what are known as Bok globules. These can contain up to 50 solar masses of material. As a globule collapses and the density increases, the gravitational energy is converted into heat and the temperature rises. When the protostellar cloud has approximately reached the stable condition of hydrostatic equilibrium, a protostar forms at the core.[29] These pre-main sequence stars are often surrounded by a protoplanetary disk. The period of gravitational contraction lasts for about 10–15 million years. Early stars of less than 2 solar masses are called T Tauri stars, while those with greater mass are Herbig Ae/Be stars. These newly born stars emit jets of gas along their axis of rotation, producing small patches of nebulosity known as Herbig-Haro objects.[30]

Main sequence Main article: Main sequence Stars spend about 90% of their lifetime fusing hydrogen to produce helium in high-temperature and high-pressure reactions near the core. Such stars are said to be on the main sequence and are called dwarf stars. Starting at zeroage main sequence, the proportion of helium in a star's core will steadily increase. As a consequence, in order to

maintain the required rate of nuclear fusion at the core, the star will slowly increase in temperature and luminosity.[31] The Sun, for example, is estimated to have increased in luminosity by about 40% since it reached the main sequence 4.6 billion years ago.[32] Every star generates a stellar wind of particles that causes a continual outflow of gas into space. For most stars, the amount of mass lost is negligible. The Sun loses 10−14 solar masses every year,[33] or about 0.01% of its total mass over its entire lifespan. However very massive stars can lose 10 −7 to 10−5 solar masses each year, significantly affecting their evolution.[34] Stars that begin with more than 50 solar masses can lose over half their total mass while they remain on the main sequence.[35]

An example of a Hertzsprung-Russell diagram for a set of stars that includes the Sun (center). (See "Classification" below.) The duration that a star spends on the main sequence depends primarily on the amount of fuel it has to fuse and the rate at which it fuses that fuel. In other words, its initial mass and its luminosity. For the Sun, this is estimated to be about 1010 years. Large stars consume their fuel very rapidly and are short-lived. Small stars (called red dwarfs) consume their fuel very slowly and last tens to hundreds of billions of years. At the end of their lives, they simply become dimmer and dimmer. [2] However, since the lifespan of such stars is greater than the current age of the universe (13.7 billion years), no such stars are expected to exist yet. Besides mass, the portion of elements heavier than helium can play a significant role in the evolution of stars. In astronomy all elements heavier than helium are considered a "metal", and the chemical concentration of these elements is called the metallicity. The metallicity can influence the duration that a star will burn its fuel, control the formation of magnetic fields[36] and modify the strength of the stellar wind.[37] Older, population II stars have substantially less metallicity than the younger, population I stars due to the composition of the molecular clouds from which they formed. (Over time these clouds become increasingly enriched in heavier elements as older stars die and shed portions of their atmospheres.)

Post-main sequence As stars of at least 0.4 solar masses[2] exhaust their supply of hydrogen at their core, their outer layers expand greatly and cool to form a red giant. For example, in about 5 billion years, when the Sun is a red giant, it will expand out to a maximum radius of roughly 1 AU (150,000,000 km), 250 times its present size. As a giant, the Sun will lose roughly 30% of its current mass.[32][38] In a red giant of up to 2.25 solar masses, hydrogen fusion proceeds in a shell-layer surrounding the core. [39] Eventually the core is compressed enough to start helium fusion, and the star now gradually shrinks in radius and increases its surface temperature. For larger stars, the core region transitions directly from fusing hydrogen to fusing helium.[40] After the star has consumed the helium at the core, fusion continues in a shell around a hot core of carbon and oxygen. The star then follows an evolutionary path that parallels the original red giant phase, but at a higher surface temperature. Massive stars

Betelgeuse is a red supergiant star approaching the end of its life cycle During their helium-burning phase, very high mass stars with more than nine solar masses expand to form red supergiants. Once this fuel is exhausted at the core, they can continue to fuse elements heavier than helium. The core contracts until the temperature and pressure are sufficient to fuse carbon (see carbon burning process). This process continues, with the successive stages being fueled by neon (see neon burning process), oxygen (see oxygen burning process), and silicon (see silicon burning process). Near the end of the star's life, fusion can occur along a series of onion-layer shells within the star. Each shell fuses a different element, with the outermost shell fusing hydrogen; the next shell fusing helium, and so forth.[41] The final stage is reached when the star begins producing iron. Since iron nuclei are more tightly bound than any heavier nuclei, if they are fused they do not release energy—the process would, on the contrary, consume energy. Likewise, since they are more tightly bound than all lighter nuclei, energy cannot be released by fission.[39] In relatively old, very massive stars, a large core of inert iron will accumulate in the center of the star. The heavier elements in these stars can work their way up to the surface, forming evolved objects known as Wolf-Rayet stars that have a dense stellar wind which sheds the outer atmosphere. Collapse An evolved, average-size star will now shed its outer layers as a planetary nebula. If what remains after the outer atmosphere has been shed is less than 1.4 solar masses, it shrinks to a relatively tiny object (about the size of Earth) that is not massive enough for further compression to take place, known as a white dwarf.[42] The electron-degenerate matter inside a white dwarf is no longer a plasma, even though stars are generally referred to as being spheres of plasma. White dwarfs will eventually fade into black dwarfs over a very long stretch of time.

The Crab Nebula, remnants of a supernova that was first observed around 1050 AD In larger stars, fusion continues until the iron core has grown so large (more than 1.4 solar masses) that it can no longer support its own mass. This core will suddenly collapse as its electrons are driven into its protons, forming neutrons and neutrinos in a burst of inverse beta decay, or electron capture. The shockwave formed by this sudden collapse causes the rest of the star to explode in a supernova. Supernovae are so bright that they may briefly outshine the star's entire home galaxy. When they occur within the Milky Way, supernovae have historically been observed by naked-eye observers as "new stars" where none existed before.[43] Most of the matter in the star is blown away by the supernovae explosion (forming nebulae such as the Crab Nebula[43]) and what remains will be a neutron star (which sometimes manifests itself as a pulsar or X-ray burster) or, in the case of the largest stars (large enough to leave a stellar remnant greater than roughly 4 solar masses), a black hole.[44] In a neutron star the matter is in a state known as neutrondegenerate matter, with a more exotic form of degenerate matter, QCD matter, possibly present in the core. Within a black hole the matter is in a state that is not currently understood.

The blown-off outer layers of dying stars include heavy elements which may be recycled during new star formation. These heavy elements allow the formation of rocky planets. The outflow from supernovae and the stellar wind of large stars play an important part in shaping the interstellar medium.[43]

Distribution A white dwarf star in orbit around Sirius (artist's impression). NASA image In addition to isolated stars, a multi-star system can consist of two or more gravitationally bound stars that orbit around each other. The most common multi-star system is a binary star, but systems of three or more stars are also found. For reasons of orbital stability, such multi-star systems are often organized into hierarchical sets of co-orbiting binary stars.[45] Larger groups called star clusters also exist. These range from loose stellar associations with only a few stars, up to enormous globular clusters with hundreds of thousands of stars. It has been a long-held assumption that the majority of stars occur in gravitationally bound, multiple-star systems. This is particularly true for very massive O and B class stars, where 80% of the systems are believed to be multiple. However the portion of single star systems increases for smaller stars, so that only 25% of red dwarfs are known to have stellar companions. As 85% of all stars are red dwarfs, most stars in the Milky Way are likely single from birth.[46] Stars are not spread uniformly across the universe, but are normally grouped into galaxies along with interstellar gas and dust. A typical galaxy contains hundreds of billions of stars, and there are more than 100 billion (1011) galaxies in the observable universe.[47] While it is often believed that stars only exist within galaxies, intergalactic stars have been discovered.[48] Astronomers estimate that there are at least 70 sextillion (7×1022) stars in the observable universe.[49] The nearest star to the Earth, apart from the Sun, is Proxima Centauri, which is 39.9 trillion (1012) kilometres, or 4.2 light-years away. Light from Proxima Centauri takes 4.2 years to reach Earth. Travelling at the orbital speed of the Space Shuttle (5 miles per second—almost 30,000 kilometres per hour), it would take about 150,000 years to get there.[50] Distances like this are typical inside galactic discs, including in the vicinity of the solar system.[51] Stars can be much closer to each other in the centres of galaxies and in globular clusters, or much farther apart in galactic halos. Due to the relatively vast distances between stars outside the galactic nucleus, collisions between stars are thought to be rare. In denser regions such as the core of globular clusters or the galactic center, collisions can be more common.[52] Such collisions can produce what are known as blue stragglers. These abnormal stars have a higher surface temperature than the other main sequence stars with the same luminosity in the cluster .[53]

Characteristics The Sun is the nearest star to Earth

Almost everything about a star is determined by its initial mass, including essential characteristics such as luminosity and size, as well as the star's evolution, lifespan, and eventual fate.

Age Most stars are between 1 billion and 10 billion years old. Some stars may even be close to 13.7 billion years old—the observed age of the universe. The oldest star yet discovered, HE 1523-0901, is an estimated 13.2 billion years old.[54] The more massive the star, the shorter its lifespan, primarily because massive stars have greater pressure on their cores, causing them to burn hydrogen more rapidly. The most massive stars last an average of about one million years, while stars of minimum mass (red dwarfs) burn their fuel very slowly and last tens to hundreds of billions of years.[55][56]

Chemical composition See also: Metallicity When stars form they are composed of about 70% hydrogen and 28% helium, as measured by mass, with a small fraction of heavier elements. Typically the portion of heavy elements is measured in terms of the iron content of the stellar atmosphere, as iron is a common element and its absorption lines are relatively easy to measure. Because the molecular clouds where stars form are steadily enriched by heavier elements from supernovae explosions, a measurement of the chemical composition of a star can be used to infer its age.[57] The portion of heavier elements may also be an indicator of the likelihood that the star has a planetary system.[58] The star with the lowest iron content ever measured is the dwarf HE1327-2326, with only 1/200,000th the iron content of the Sun.[59] By contrast, the super-metal-rich star μ Leonis has nearly double the abundance of iron as the Sun, while the planet-bearing star 14 Herculis has nearly triple the iron.[60] There also exist chemically peculiar stars that show unusual abundances of certain elements in their spectrum; especially chromium and rare earth elements.[61]

Diameter Due to their great distance from the Earth, all stars except the Sun appear to the human eye as shining points in the night sky that twinkle because of the effect of the Earth's atmosphere. The Sun is also a star, but it is close enough to the Earth to appear as a disk instead, and to provide daylight. Other than the Sun, the star with the largest apparent size is R Doradus, with an angular diameter of only 0.057 arcseconds.[62] The disks of most stars are much too small in angular size to be observed with current ground-based optical telescopes, and so interferometer telescopes are required in order to produce images of these objects. Another technique for measuring the angular size of stars is through occultation. By precisely measuring the drop in brightness of a star as it is occulted by the Moon (or the rise in brightness when it reappears), the star's angular diameter can be computed.[63] Stars range in size from neutron stars, which vary anywhere from 20 to 40 km in diameter, to supergiants like Betelgeuse in the Orion constellation, which has a diameter approximately 650 times larger than the Sun—about 0.9 billion kilometres. However, Betelgeuse has a much lower density than the Sun.[64]

Kinematics

Main article: Stellar kinematics The motion of a star relative to the Sun can provide useful information about the origin and age of a star, as well as the structure and evolution of the surrounding galaxy. The components of motion of a star consist of the radial velocity toward or away from the Sun, and the traverse angular movement, which is called its proper motion. Radial velocity is measured by the doppler shift of the star's spectral lines, and is given in units of km/s. The proper motion of a star is determined by precise astrometric measurements in units of milli-arc seconds (mas) per year. By determining the parallax of a star, the proper motion can then be converted into units of velocity. Stars with high rates of proper motion are likely to be relatively close to the Sun, making them good candidates for parallax measurements.[65] Once both rates of movement are known, the space velocity of the star relative to the Sun or the galaxy can be computed. Among nearby stars, it has been found that population I stars have generally lower velocities than older, population II stars. The latter have elliptical orbits that are inclined to the plane of the galaxy.[66] Comparison of the kinematics of nearby stars has also led to the identification of stellar associations. These are most likely groups of stars that share a common point of origin in giant molecular clouds. [67]

Magnetic field Main article: Stellar magnetic field Surface magnetic field of SU Aur (a young star of T Tauri type), reconstructed by means of Zeeman-Doppler imaging The magnetic field of a star is generated within regions of the interior where convective circulation occurs. This movement of conductive plasma functions like a dynamo, generating magnetic fields that extend throughout the star. The strength of the magnetic field varies with the mass and composition of the star, and the amount of magnetic surface activity depends upon the star's rate of rotation. This surface activity produces starspots, which are regions of strong magnetic fields and lower than normal surface temperatures. Coronal loops are arching magnetic fields that reach out into the corona from active regions. Stellar flares are bursts of high-energy particles that are emitted due to the same magnetic activity.[68] Young, rapidly rotating stars tend to have high levels of surface activity because of their magnetic field. The magnetic field can act upon a star's stellar wind, however, functioning as a brake to gradually slow the rate of rotation as the star grows older. Thus, older stars such as the Sun have a much slower rate of rotation and a lower level of surface activity. The activity levels of slowly rotating stars tend to vary in a cyclical manner and can shut down altogether for periods.[69] During the Maunder minimum, for example, the Sun underwent a 70-year period with almost no sunspot activity.

Mass

One of the most massive stars known is Eta Carinae,[70] with 100–150 times as much mass as the Sun; its lifespan is very short—only several million years at most. A recent study of the Arches cluster suggests that 150 solar masses is the upper limit for stars in the current era of the universe.[71] The reason for this limit is not precisely known, but it is partially due to the Eddington luminosity which defines the maximum amount of luminosity that can pass through the atmosphere of a star without ejecting the gases into space.

The reflection nebula NGC 1999 is brilliantly illuminated by V380 Orionis (center), a variable star with about 3.5 times the mass of the Sun. NASA image The first stars to form after the Big Bang may have been larger, up to 300 solar masses or more,[72] due to the complete absence of elements heavier than lithium in their composition. This generation of supermassive, population III stars is long extinct, however, and currently only theoretical. With a mass only 93 times that of Jupiter, AB Doradus C, a companion to AB Doradus A, is the smallest known star undergoing nuclear fusion in its core.[73] For stars with similar metallicity to the Sun, the theoretical minimum mass the star can have, and still undergo fusion at the core, is estimated to be about 75 times the mass of Jupiter.[74][75] When the metallicity is very low, however, a recent study of the faintest stars found that the minimum star size seems to be about 8.3% of the solar mass, or about 87 times the mass of Jupiter.[76][75] Smaller bodies are called brown dwarfs, which occupy a poorly defined grey area between stars and gas giants. The combination of the radius and the mass of a star determines the surface gravity. Giant stars have a much lower surface gravity than main sequence stars, while the opposite is the case for degenerate, compact stars such as white dwarfs. The surface gravity can influence the appearance of a star's spectrum, with higher gravity causing a broadening of the absorption lines.[17]

Rotation Main article: Stellar rotation The rotation rate of stars can be approximated through spectroscopic measurement, or more exactly determined by tracking the rotation rate of starspots. Young stars can have a rapid rate of rotation greater than 100 km/s at the equator. The B-class star Achernar, for example, has an equatorial rotation velocity of about 225 km/s or greater, giving it an equatorial diameter that is more than 50% larger than the distance between the poles. This rate of rotation is just below the critical velocity of 300 km/s where the star would break apart.[77] By contrast, the Sun only rotates once every 25 – 35 days, with an equatorial velocity of 1.994 km/s. The star's magnetic field and the stellar wind serve to slow down a main sequence star's rate of rotation by a significant amount as it evolves on the main sequence.[78] Degenerate stars have contracted into a compact mass, resulting in a rapid rate of rotation. However they have relatively low rates of rotation compared to what would be expected by conservation of angular momentum—the tendency of a rotating body to compensate for a contraction in size by increasing its rate of spin. A large portion of the star's angular momentum is dissipated as a result of mass loss through the stellar wind.[79] In spite of this, the rate of rotation for a pulsar can be very rapid. The pulsar at the heart of

the Crab nebula, for example, rotates 30 times per second.[80] The rotation rate of the pulsar will gradually slow due to the emission of radiation.

Temperature The surface temperature of a main sequence star is determined by the rate of energy production at the core and the radius of the star and is often estimated from the star's color index.[81] It is normally given as the effective temperature, which is the temperature of an idealized black body that radiates its energy at the same luminosity per surface area as the star. Note that the effective temperature is only a representative value, however, as stars actually have a temperature gradient that decreases with increasing distance from the core.[82] The temperature in the core region of a star is several million kelvins.[83] The stellar temperature will determine the rate of energization or ionization of different elements, resulting in characteristic absorption lines in the spectrum. The surface temperature of a star, along with its visual absolute magnitude and absorption features, is used to classify a star (see classification below). [17]

Massive main sequence stars can have surface temperatures of 50,000 K. Smaller stars such as the Sun have surface temperatures of a few thousand degrees. Red giants have relatively low surface temperatures of about 3,600 K, but they also have a high luminosity due to their large exterior surface area.[84]

Radiation The energy produced by stars, as a by-product of nuclear fusion, radiates into space as both electromagnetic radiation and particle radiation. The particle radiation emitted by a star is manifested as the stellar wind[85] (which exists as a steady stream of electrically charged particles, such as free protons, alpha particles, and beta particles, emanating from the star’s outer layers) and as a steady stream of neutrinos emanating from the star’s core. The production of energy at the core is the reason why stars shine so brightly: every time two or more atomic nuclei of one element fuse together to form an atomic nucleus of a new heavier element, gamma ray photons are released from the nuclear fusion reaction. This energy is converted to other forms of electromagnetic energy, including visible light, by the time it reaches the star’s outer layers. The color of a star, as determined by the peak frequency of the visible light, depends on the temperature of the star’s outer layers, including its photosphere.[86] Besides visible light, stars also emit forms of electromagnetic radiation that are invisible to the human eye. In fact, stellar electromagnetic radiation spans the entire electromagnetic spectrum, from the longest wavelengths of radio waves and infrared to the shortest wavelengths of ultraviolet, X-rays, and gamma rays. All components of stellar electromagnetic radiation, both visible and invisible, are typically significant. Using the stellar spectrum, astronomers can also determine the surface temperature, surface gravity, metallicity and rotational velocity of a star. If the distance of the star is known, such as by measuring the parallax, then the luminosity of the star can be derived. The mass, radius, surface gravity, and rotation period can then be estimated based on stellar models. (Mass can be measured directly for stars in binary systems. The technique of gravitational microlensing will also yield the mass of a star.[87]) With these parameters, astronomers can also estimate the age of the star.[88]

Luminosity

In astronomy, luminosity is the amount of light, and other forms of radiant energy, a star radiates per unit of time. The luminosity of a star is determined by the radius and the surface temperature. However, many stars do not radiate a uniform flux—the amount of energy radiated per unit area—across their entire surface. The rapidly rotating star Vega, for example, has a higher energy flux at its poles than along its equator.[89] Surface patches with a lower temperature and luminosity than average are known as starspots. Small, dwarf stars such as the Sun generally have essentially featureless disks with only small starspots. Larger, giant stars have much bigger, much more obvious starspots,[90] and they also exhibit strong stellar limb darkening. That is, the brightness decreases towards the edge of the stellar disk.[91] Red dwarf flare stars such as UV Ceti may also possess prominent starspot features.[92]

Magnitude Main articles: Apparent magnitude and Absolute magnitude The apparent brightness of a star is measured by its apparent magnitude, which is the brightness of a star with respect to the star’s luminosity, distance from Earth, and the altering of the star’s light as it passes through Earth’s atmosphere. Intrinsic or absolute magnitude is what the apparent magnitude a star would be if the distance between the Earth and the star were 10 parsecs (32.6 light-years), and it is directly related to a star’s luminosity. Number of magnitude

stars

brighter

Apparent magnitude

Number of Stars[93]

0

4

1

15

2

48

3

171

4

513

5

1,602

6

4,800

7

14,000

than

Both the apparent and absolute magnitude scales are logarithmic units: one whole number difference in magnitude is equal to a brightness variation of about 2.5 times[94] (the 5th root of 100 or approximately 2.512). This means that a first magnitude (+1.00) star is about 2.5 times brighter than a second magnitude (+2.00) star, and approximately 100 times brighter than a sixth magnitude (+6.00) star. The faintest stars visible to the naked eye under good seeing conditions are about magnitude +6. On both apparent and absolute magnitude scales, the smaller the magnitude number, the brighter the star; the larger the magnitude number, the fainter. The brightest stars, on either scale, have negative magnitude numbers. The variation in brightness between two stars is calculated by subtracting the magnitude number of the brighter star (mb) from the magnitude number of the fainter star (mf), then using the difference as an exponent for the base number 2.512; that is to say: Δm = mf − mb 2.512Δm = variation in brightness Relative to both luminosity and distance from Earth, absolute magnitude (M) and apparent magnitude (m) are not equivalent for an individual star;[94] for example, the bright star Sirius has an apparent magnitude of −1.44, but it has an absolute magnitude of +1.41.

The Sun has an apparent magnitude of −26.7, but its absolute magnitude is only +4.83. Sirius, the brightest star in the night sky as seen from Earth, is approximately 23 times more luminous than the Sun, while Canopus, the second brightest star in the night sky with an absolute magnitude of −5.53, is approximately 14,000 times more luminous than the Sun. Despite Canopus being vastly more luminous than Sirius, however, Sirius appears brighter than Canopus. This is because Sirius is merely 8.6 lightyears from the Earth, while Canopus is much farther away at a distance of 310 light-years. As of 2006, the star with the highest known absolute magnitude is LBV 1806-20, with a magnitude of −14.2. This star is at least 5,000,000 times more luminous than the Sun.[95] The least luminous stars that are currently known are located in the NGC 6397 cluster. The faintest red dwarfs in the cluster were magnitude 26, while a 28th magnitude white dwarf was also discovered. These faint stars are so dim that their light is as bright as a birthday candle on the Moon when viewed from the Earth.[96]

Classification Main article: Stellar classification Surface Temperature Ranges Different Stellar Classes[97] Class Temperature

Sample star

O

33,000 K or more Zeta Ophiuchi

B

10,500–30,000 K Rigel

A

7,500–10,000 K

Altair

F

6,000–7,200 K

Procyon A

G

5,500–6,000 K

Sun

K

4,000–5,250 K

Epsilon Indi

for The current stellar classification system originated in the early 20th century, when stars were classified from A to Q based on the strength of the hydrogen line.[98] It was not known at the time that the major influence on the line strength was temperature; the hydrogen line strength reaches a peak at around 9000 K, and is weaker at both hotter and cooler temperatures. When the classifications were reordered by temperature, it more closely resembled the modern scheme.[99] There are different single-letter classifications of stars according to their spectra, ranging from type O, which are very hot, to M, which are so cool that molecules may form in their atmospheres. The main classifications in order of decreasing surface temperature are: O, B, A, F, G, K, and M. A variety of rare spectral types have special classifications. The most common of these are types L and T, which classify the coldest low-mass stars and brown dwarfs. Each letter has 10 sub-divisions, numbered from 0 to 9, in order of decreasing temperature. However, this system breaks down at extreme high temperatures: class O0 and O1 stars may not exist.[100]

In addition, stars may be classified by the luminosity effects found in their spectral lines, which correspond to M 2,600–3,850 K Proxima Centauri their spatial size and is determined by the surface gravity. These range from 0 (hypergiants) through III (giants) to V (main sequence dwarfs) and VII (white dwarfs). Most stars belong to the main sequence, which consists of ordinary hydrogen-burning stars. These fall along a narrow, diagonal band when graphed according to their absolute magnitude and spectral type.[100] Our Sun is a main sequence G2V yellow dwarf, being of intermediate temperature and ordinary size.

Additional nomenclature, in the form of lower-case letters, can follow the spectral type to indicate peculiar features of the spectrum. For example, an "e" can indicate the presence of emission lines; "m" represents unusually strong levels of metals, and "var" can mean variations in the spectral type.[100] White dwarf stars have their own class that begins with the letter D. This is further sub-divided into the classes DA, DB, DC, DO, DZ, and DQ, depending on the types of prominent lines found in the spectrum. This is followed by a numerical value that indicates the temperature index.[101]

Variable stars Main article: Variable star The asymmetrical appearance of Mira, an oscillating variable star. NASA HST image Variable stars have periodic or random changes in luminosity because of intrinsic or extrinsic properties. Of the intrinsically variable stars, the primary types can be subdivided into three principal groups. During their stellar evolution, some stars pass through phases where they can become pulsating variables. Pulsating variable stars vary in radius and luminosity over time, expanding and contracting with periods ranging from minutes to years, depending on the size of the star. This category includes Cepheid and cepheid-like stars, and long-period variables such as Mira.[102] Eruptive variables are stars that experience sudden increases in luminosity because of flares or mass ejection events.[102] This group includes protostars, Wolf-Rayet stars, and Flare stars, as well as giant and supergiant stars. Cataclysmic or explosive variables undergo a dramatic change in their properties. This group includes novae and supernovae. A binary star system that includes a nearby white dwarf can produce certain types of these spectacular stellar explosions, including the nova and a Type 1a supernova.[4] The explosion is created when the white dwarf accretes hydrogen from the companion star, building up mass until the hydrogen undergoes fusion.[103] Some novae are also recurrent, having periodic outbursts of moderate amplitude.[102] Stars can also vary in luminosity because of extrinsic factors, such as eclipsing binaries, as well as rotating stars that produce extreme starspots.[102] A notable example of an eclipsing binary is Algol, which regularly varies in magnitude from 2.3 to 3.5 over a period of 2.87 days.

Structure Main article: Stellar structure The interior of a stable star is in a state of hydrostatic equilibrium: the forces on any small volume almost exactly counterbalance each other. The balanced forces are inward gravitational force and an outward force due to the pressure gradient within the star. The pressure gradient is established by the temperature gradient of the plasma; the outer part of the star is cooler than the core. The temperature at the core of a main sequence or giant star is at least on the order of 107 K. The resulting temperature and pressure at the hydrogen-burning core of a main sequence star are sufficient for nuclear fusion to occur and for sufficient energy to be produced to prevent further collapse of the star.[104][105]

As atomic nuclei are fused in the core, they emit energy in the form of gamma rays. These photons interact with the surrounding plasma, adding to the thermal energy at the core. Stars on the main sequence convert hydrogen into helium, creating a slowly but steadily increasing proportion of helium in the core. Eventually the helium content becomes predominant and energy production ceases at the core. Instead, for stars of more than 0.4 solar masses, fusion occurs in a slowly expanding shell around the degenerate helium core.[106] In addition to hydrostatic equilibrium, the interior of a stable star will also maintain an energy balance of thermal equilibrium. There is a radial temperature gradient throughout the interior that results in a flux of energy flowing toward the exterior. The outgoing flux of energy leaving any layer within the star will exactly match the incoming flux from below.

This diagram shows a cross-section of a solar-type star. NASA image The radiation zone is the region within the stellar interior where radiative transfer is sufficiently efficient to maintain the flux of energy. In this region the plasma will not be perturbed and any mass motions will die out. If this is not the case, however, then the plasma becomes unstable and convection will occur, forming a convection zone. This can occur, for example, in regions where very high energy fluxes occur, such as near the core or in areas with high opacity as in the outer envelope.[105] The occurrence of convection in the outer envelope of a main sequence star depends on the mass. Stars with several times the mass of the Sun have a convection zone deep within the interior and a radiative zone in the outer layers. Smaller stars such as the Sun are just the opposite, with the convective zone located in the outer layers.[107] Red dwarf stars with less than 0.4 solar masses are convective throughout, which prevents the accumulation of a helium core.[2] For most stars the convective zones will also vary over time as the star ages and the constitution of the interior is modified.[105] The portion of a star that is visible to an observer is called the photosphere. This is the layer at which the plasma of the star becomes transparent to photons of light. From here, the energy generated at the core becomes free to propagate out into space. It is within the photosphere that sun spots, or regions of lower than average temperature, appear. Above the level of the photosphere is the stellar atmosphere. In a main sequence star such as the Sun, the lowest level of the atmosphere is the thin chromosphere region, where spicules appear and stellar flares begin. This is surrounded by a transition region, where the temperature rapidly increases within a distance of only 100 km. Beyond this is the corona, a volume of super-heated plasma that can extend outward to several million kilometres.[108] The existence of a corona appears to be dependent on a convective zone in the outer layers of the star.[107] Despite its high temperature, the corona emits very little light. The corona region of the Sun is normally only visible during a solar eclipse. From the corona, a stellar wind of plasma particles expands outward from the star, propagating until it interacts with the interstellar medium. For the Sun, the influence of its solar wind extends throughout the bubble-shaped region of the heliosphere.[109]

Nuclear fusion reaction pathways Main article: Stellar nucleosynthesis Overview of the proton-proton chain The carbon-nitrogen-oxygen cycle A variety of different nuclear fusion reactions take place inside the cores of stars, depending upon their mass and composition, as part of stellar nucleosynthesis. The net mass of the fused atomic nuclei is smaller than the sum of the constituents. This lost mass is converted into energy, according to the massenergy equivalence relationship E = mc².[1] The hydrogen fusion process is temperature-sensitive, so a moderate increase in the core temperature will result in a significant increase in the fusion rate. As a result the core temperature of main sequence stars only varies from 4 million K for a small M-class star to 40 million K for a massive O-class star.[83] In the Sun, with a 10 million K core, hydrogen fuses to form helium in the proton-proton chain reaction: [110]

41H → 22H + 2e+ + 2νe (4.0 MeV + 1.0 MeV) 21H + 22H → 23He + 2γ (5.5 MeV) 23He → 4He + 21H (12.9 MeV) These reactions result in the overall reaction: 41H → 4He + 2e+ + 2γ + 2νe (26.7 MeV) where e+ is a positron, γ is a gamma ray photon, νe is a neutrino, and H and He are isotopes of hydrogen and helium, respectively. The energy released by this reaction is in millions of electron volts, which is actually only a tiny amount of energy. However enormous numbers of these reactions occur constantly, producing all the energy necessary to sustain the star's Minimum stellar mass required for fusion radiation output.

Element

Solar masses

Hydrogen

0.01

Helium

0.4

Carbon

5[111]

In more massive stars, helium is produced in a cycle of reactions catalyzed by carbon—the carbon-nitrogenoxygen cycle.[110] In evolved stars with cores at 100 million K and masses between 0.5 and 10 solar masses, helium can be transformed into carbon in the triple-alpha process that uses the intermediate element beryllium:[110] 4

He + 4He + 92 keV → 8*Be 4 He + 8*Be + 67 keV → 12*C 12* C → 12C + γ + 7.4 MeV For an overall reaction of:

Neon

8

34He → 12C + γ + 7.2 MeV In massive stars, heavier elements can also be burned in a contracting core through the neon burning process and oxygen burning process. The final stage in the stellar nucleosynthesis process is the silicon burning process that results in the production of the stable isotope iron-56. Fusion can not proceed any further except through an endothermic process, and so further energy can only be produced through gravitational collapse.[110] The example below shows the amount of time required for a star of 20 solar masses to consume all of its nuclear fuel. As an O-class main sequence star, it would be 8 times the solar radius and 62,000 times the Sun's luminosity.[112]

See also

Fuel Temperature Density Burn duration material (million kelvins) (kg/cm³) (τ in years) General topics • Constellations • Stellar astronomy • Lists of stars H 37 0.0045 8.1 million • Timeline of stellar astronomy • Star count Types of stars He • Blue 188straggler 0.97 1.2 million • Main sequence star • Bright giant • Neutron star • Carbon star • Red dwarf C • Giant 870 star 170 976 • Red giant • High-velocity star • Runaway star • Hypergiant • Supergiant Ne 1,570 3,100 0.6 • Hypervelocity star • Wolf-Rayet star Types of former stars Hole • Magnetar O • Black 1,980 5,550 1.25 • Brown dwarf • Neutron star S/Si• •

Hypernova 3,340

33,400

0.0315[113]

White dwarf Types of hypothetical stars •

Black dwarf

Time and navigation • • •

Sidereal clock Star clocks Stellar navigation

Other •

Nursery rhyme Twinkle twinkle little star

•

Stars and planetary systems in fiction

•

Stars in astrology

References

History of the Earth From Wikipedia, the free encyclopedia

(Redirected from History of Earth) Jump to: navigation, search For the history of modern humans, see History of the world. Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earth's history. The history of the Earth covers approximately 4.5 billion years (4,540,000,000 years),[1] from Earth’s formation out of the solar nebula to the present. This article presents a broad overview, summarizing the leading, most current scientific theories.

Contents [hide] • • • • • • • • • • • • • •

1 Origin 2 Moon 3 The Hadean eon 4 Life 5 Cells 6 Photosynthesis and oxygen 7 Endosymbiosis and the three domains of life 8 Multicellularity 9 Colonization of land 10 Humanity 11 Civilization 12 Recent events 13 See also 14 References

•

15 External links

[edit] Origin An artist's

impression of protoplanetary disk. Main article: Formation and evolution of the Solar System The Earth formed as part of the birth of the Solar System: what eventually became the solar system

initially existed as a large, rotating cloud of dust, rocks, and gas. It was composed of hydrogen and helium produced in the Big Bang, as well as heavier elements ejected by supernovas. Then, as one theory suggests, about 4.6 billion years ago a nearby star was destroyed in a supernova and the explosion sent a shock wave through the solar nebula, causing it to gain angular momentum. As the cloud began to accelerate its rotation, gravity and inertia flattened it into a protoplanetary disk oriented perpendicularly to its axis of rotation. Most of the mass concentrated in the middle and began to heat up, but small perturbations due to collisions and the angular momentum of other large debris created the means by which protoplanets began to form. The infall of material, increase in rotational speed and the crush of gravity created an enormous amount of kinetic heat at the center. Its inability to transfer that energy away through any other process at a rate capable of relieving the build-up resulted in the disk's center heating up. Ultimately, nuclear fusion of hydrogen into helium began, and eventually, after contraction, a T Tauri star ignited to create the Sun. Meanwhile, as gravity caused matter to condense around the previously perturbed objects outside of the new sun's gravity grasp, dust particles and the rest of the protoplanetary disk began separating into rings. Successively larger fragments collided with one another and became larger objects, ultimately destined to become protoplanets.[2] These included one collection approximately 150 million kilometers from the center: Earth. The planet formed about 4.54 billion years ago (within an uncertainty of 1%),[3][4][5][6] and the planet was largely completed within 10–20 million years.[7] The solar wind of the newly formed T Tauri star cleared out most of the material in the disk that had not already condensed into larger bodies.

[edit] Moon Animation (not to scale) of Theia forming in Earth’s L5 point and then, perturbed by gravity, colliding to help form the moon. The animation progresses in one-year steps making Earth appear not to move. The view is of the south pole. Main articles: Origin and geologic evolution and Giant impact hypothesis The origin of the Moon is still uncertain, although much evidence exists for the giant impact hypothesis. Earth may not have been the only planet forming 150 million kilometers from the Sun. It is hypothesized that another collection occurred 150 million kilometers from both the Sun and the Earth, at their fourth or fifth Lagrangian point. This planet, named Theia, is thought to have been smaller than the current Earth, probably about the size and mass of Mars. Its orbit may at first have been stable, but destabilized as Earth increased its mass by the accretion of more and more material. Theia swung back and forth relative to Earth until, finally, an estimated 4.533 billion years ago,[8] it collided at a low, oblique angle. The low speed and angle were not enough to destroy Earth, but a large portion of its crust was ejected into space. Heavier elements from Theia sank to Earth’s core, while the remaining material and ejecta condensed into a single body within a couple of weeks. Under the influence of its own gravity, this became a more spherical body: the Moon. [9] The impact is also thought to have changed Earth’s axis to produce the large 23.5° axial tilt that is responsible for Earth’s seasons. (A simple, ideal model of the planets’ origins would have axial tilts of 0° with no recognizable seasons.) It may also have sped up Earth’s rotation and initiated the planet’s plate tectonics.

[edit] The Hadean eon Main article: Hadean

Volcanic eruptions would have been common in Earth's early days. The early Earth, during the very early Hadean eon, was very different from the world known today. There were no oceans and no oxygen in the atmosphere. It was bombarded by planetoids and other material left over from the formation of the solar system. This bombardment, combined with heat from radioactive breakdown, residual heat, and heat from the pressure of contraction, caused the planet at this stage to be fully molten. During the iron catastrophe heavier elements sank to the center while lighter ones rose to the surface producing the layered structure of the Earth and also setting up the formation of Earth's magnetic field. Earth's early atmosphere would have comprised surrounding material from the solar nebula, especially light gases such as hydrogen and helium, but the solar wind and Earth's own heat would have driven off this atmosphere. This changed when Earth was about 40% its present radius, and gravitational attraction allowed the retention of an atmosphere which included water. Temperatures plummeted and the crust of the planet was accumulated on a solid surface, with areas melted by large impacts on the scale of decades to hundreds of years between impacts. Large impacts would have caused localized melting and partial differentiation, with some lighter elements on the surface or released to the moist atmosphere.[10] The surface cooled quickly, forming the solid crust within 150 million years;[11] although new research[12] suggests that the actual number is 100 million years based on the level of hafnium found in the geology at Jack Hills in Western Australia. From 4 to 3.8 billion years ago, Earth underwent a period of heavy asteroidal bombardment.[13] Steam escaped from the crust while more gases were released by volcanoes, completing the second atmosphere. Additional water was imported by bolide collisions, probably from asteroids ejected from the outer asteroid belt under the influence of Jupiter's gravity. The planet cooled. Clouds formed. Rain gave rise to the oceans within 750 million years (3.8 billion years ago), but probably earlier. Recent evidence suggests the oceans may have begun forming by 4.2 billion years ago[14].[15] The new atmosphere probably contained ammonia, methane, water vapor, carbon dioxide, and nitrogen, as well as smaller amounts of other gases. Any free oxygen would have been bound by hydrogen or minerals on the surface. Volcanic activity was intense and, without an ozone layer to hinder its entry, ultraviolet radiation flooded the surface.

[edit] Life The replicator in virtually all known life is deoxyribonucleic acid. DNA is far more complex than the original replicator and its replication systems are highly elaborate. Main article: Origin of life The details of the origin of life are unknown though the broad principles have been established. Two schools of thought regarding the origin of life have been proposed. The first suggests that organic components may have arrived on Earth from space (see “Panspermia”), while the other argues for terrestrial origins. The mechanisms by which life would initially arise are nevertheless held to be similar. [16] If life arose on Earth, the timing of this event is highly speculative—perhaps it arose around 4 billion years ago.[17] In the energetic chemistry of early Earth, a molecule (or even something else) gained the ability to make copies of itself–the replicator. The nature of this molecule is unknown, its function having long since been superseded by life’s current replicator, DNA. In making copies of itself, the replicator did not always perform accurately: some copies contained an “error.” If the change destroyed the copying ability of the molecule, there could be no more copies, and the line would “die out.” On the other hand, a few rare changes might make the molecule replicate faster or better: those “strains” would become more

numerous and “successful.” As choice raw materials (“food”) became depleted, strains which could exploit different materials, or perhaps halt the progress of other strains and steal their resources, became more numerous.[18] Several different models have been proposed explaining how a replicator might have developed. Different replicators have been posited, including organic chemicals such as modern proteins, nucleic acids, phospholipids, crystals,[19] or even quantum systems.[20] There is currently no method of determining which of these models, if any, closely fits the origin of life on Earth. One of the older theories, and one which has been worked out in some detail, will serve as an example of how this might occur. The high energy from volcanoes, lightning, and ultraviolet radiation could help drive chemical reactions producing more complex molecules from simple compounds such as methane and ammonia.[21] Among these were many of the relatively simple organic compounds that are the building blocks of life. As the amount of this “organic soup” increased, different molecules reacted with one another. Sometimes more complex molecules would result—perhaps clay provided a framework to collect and concentrate organic material. [22] The presence of certain molecules could speed up a chemical reaction. All this continued for a very long time, with reactions occurring more or less at random, until by chance there arose a new molecule: the replicator. This had the bizarre property of promoting the chemical reactions which produced a copy of itself, and evolution began properly. Other theories posit a different replicator. In any case, DNA took over the function of the replicator at some point; all known life (with the exception of some viruses and prions) use DNA as their replicator, in an almost identical manner (see genetic code).

[edit] Cells A small section of a cell membrane. This modern cell membrane is far more sophisticated than the original simple phospholipid bilayer (the small blue spheres with two tails). Proteins and carbohydrates serve various functions in regulating the passage of material through the membrane and in reacting to the environment. Modern life has its replicating material packaged neatly inside a cellular membrane. It is easier to understand the origin of the cell membrane than the origin of the replicator, since the phospholipid molecules that make up a cell membrane will often form a bilayer spontaneously when placed in water. Under certain conditions, many such spheres can be formed (see “The bubble theory”).[23] It is not known whether this process preceded or succeeded the origin of the replicator (or perhaps it was the replicator). The prevailing theory is that the replicator, perhaps RNA by this point (the RNA world hypothesis), along with its replicating apparatus and maybe other biomolecules, had already evolved. Initial protocells may have simply burst when they grew too large; the scattered contents may then have recolonized other “bubbles.” Proteins that stabilized the membrane, or that later assisted in an orderly division, would have promoted the proliferation of those cell lines. RNA is a likely candidate for an early replicator since it can both store genetic information and catalyze reactions. At some point DNA took over the genetic storage role from RNA, and proteins known as enzymes took over the catalysis role, leaving RNA to transfer information and modulate the process. There is increasing belief that these early cells may have evolved in association with underwater volcanic vents known as “black smokers”.[24] or even hot, deep rocks.[25] However, it is believed that out of this multiplicity of cells, or protocells, only one survived. Current evidence suggests that the last universal common ancestor lived during the early Archean eon, perhaps roughly 3.5 billion years ago or earlier.[26],[27] This “LUCA” cell is the ancestor of all cells and hence all life on Earth. It was probably a prokaryote, possessing a cell membrane and probably ribosomes, but lacking a nucleus or membrane-bound organelles such as mitochondria or chloroplasts. Like all modern cells, it used DNA as its genetic code, RNA for information transfer and protein synthesis, and enzymes

to catalyze reactions. Some scientists believe that instead of a single organism being the last universal common ancestor, there were populations of organisms exchanging genes in lateral gene transfer.[26]

[edit] Photosynthesis and oxygen The harnessing of the sun’s energy led to several major changes in life on Earth. It is likely that the initial cells were all heterotrophs, using surrounding organic molecules (including those from other cells) as raw material and an energy source.[28] As the food supply diminished, a new strategy evolved in some cells. Instead of relying on the diminishing amounts of free-existing organic molecules, these cells adopted sunlight as an energy source. Estimates vary, but by about 3 billion years ago[29], something similar to modern photosynthesis had probably developed. This made the sun’s energy available not only to autotrophs but also to the heterotrophs that consumed them. Photosynthesis used the plentiful carbon dioxide and water as raw materials and, with the energy of sunlight, produced energy-rich organic molecules (carbohydrates). Moreover, oxygen was produced as a waste product of photosynthesis. At first it became bound up with limestone, iron, and other minerals. There is substantial proof of this in iron-oxide rich layers in geological strata that correspond with this time period. The oceans would have turned to a green color while oxygen was reacting with minerals. When the reactions stopped, oxygen could finally enter the atmosphere. Though each cell only produced a minute amount of oxygen, the combined metabolism of many cells over a vast period of time transformed Earth’s atmosphere to its current state.[30] Among the oldest examples of oxygen-producing lifeforms are fossil Stromatolites. This, then, is Earth’s third atmosphere. Some of the oxygen was stimulated by incoming ultraviolet radiation to form ozone, which collected in a layer near the upper part of the atmosphere. The ozone layer absorbed, and still absorbs, a significant amount of the ultraviolet radiation that once had passed through the atmosphere. It allowed cells to colonize the surface of the ocean and ultimately the land: [31] without the ozone layer, ultraviolet radiation bombarding the surface would have caused unsustainable levels of mutation in exposed cells. Besides making large amounts of energy available to life-forms and blocking ultraviolet radiation, the effects of photosynthesis had a third, major, and world-changing impact. Oxygen was toxic; probably much life on Earth died out as its levels rose (the “Oxygen Catastrophe”).[31] Resistant forms survived and thrived, and some developed the ability to use oxygen to enhance their metabolism and derive more energy from the same food.

[edit] Endosymbiosis and the three domains of life Main article: Endosymbiotic theory Some of the pathways by which the various endosymbionts might have arisen. Modern taxonomy classifies life into three domains. The time of the origin of these domains are speculative. The Bacteria domain probably first split off from the other forms of life (sometimes called Neomura), but this supposition is controversial. Soon after this, by 2 billion years ago, [32] the Neomura split into the Archaea and the Eukarya. Eukaryotic cells (Eukarya) are larger and more complex than prokaryotic cells (Bacteria and Archaea), and the origin of that complexity is only now coming to light.

Around this time period a bacterial cell related to today’s Rickettsia[33] entered a larger prokaryotic cell. Perhaps the large cell attempted to ingest the smaller one but failed (maybe due to the evolution of prey defenses). Perhaps the smaller cell attempted to parasitize the larger one. In any case, the smaller cell survived inside the larger cell. Using oxygen, it was able to metabolize the larger cell’s waste products and derive more energy. Some of this surplus energy was returned to the host. The smaller cell replicated inside the larger one, and soon a stable symbiotic relationship developed. Over time the host cell acquired some of the genes of the smaller cells, and the two kinds became dependent on each other: the larger cell could not survive without the energy produced by the smaller ones, and these in turn could not survive without the raw materials provided by the larger cell. Symbiosis developed between the larger cell and the population of smaller cells inside it to the extent that they are considered to have become a single organism, the smaller cells being classified as organelles called mitochondria. A similar event took place with photosynthetic cyanobacteria[34] entering larger heterotrophic cells and becoming chloroplasts.[35],[36] Probably as a result of these changes, a line of cells capable of photosynthesis split off from the other eukaryotes some time before one billion years ago. There were probably several such inclusion events, as the figure at right suggests. Besides the well-established endosymbiotic theory of the cellular origin of mitochondria and chloroplasts, it has been suggested that cells gave rise to peroxisomes, spirochetes gave rise to cilia and flagella, and that perhaps a DNA virus gave rise to the cell nucleus,[37],[38] though none of these theories are generally accepted.[39] During this period, the supercontinent Columbia is believed to have existed, probably from around 1.8 to 1.5 billion years ago; it is the oldest hypothesized supercontinent.[40]

[edit] Multicellularity Volvox aureus is believed to be similar to the first multicellular plants. Archaeans, bacteria, and eukaryotes continued to diversify and to become more sophisticated and better adapted to their environments. Each domain repeatedly split into multiple lineages, although little is known about the history of the archaea and bacteria. Around 1.1 billion years ago, the supercontinent Rodinia was assembling.[41] The plant, animal, and fungi lines had all split, though they still existed as solitary cells. Some of these lived in colonies, and gradually some division of labor began to take place; for instance, cells on the periphery might have started to assume different roles from those in the interior. Although the division between a colony with specialized cells and a multicellular organism is not always clear, around 1 billion years ago,[42] the first multicellular plants emerged, probably green algae.[43] Possibly by around 900 million years ago,[44] true multicellularity had also evolved in animals. At first it probably somewhat resembled that of today’s sponges, where all cells were totipotent and a disrupted organism could reassemble itself.[45] As the division of labor became more complete in all lines of multicellular organisms, cells became more specialized and more dependent on each other; isolated cells would die. Many scientists believe that a very severe ice age began around 770 million years ago, so severe that the surface of all the oceans completely froze (Snowball Earth). Eventually, after 20 million years, enough carbon dioxide escaped through volcanic outgassing that the resulting greenhouse effect raised global temperatures.[46] By around the same time, 750 million years ago,[47] Rodinia began to break up.

[edit] Colonization of land

For most of Earth’s history, there were no multicellular organisms on land. Parts of the surface may have vaguely resembled this view of Mars, one of Earth’s neighboring planets.[citation needed] Oxygen accumulation from photosynthesis resulted in the formation of an ozone layer that absorbed much of Sun’s ultraviolet radiation, meaning unicellular organisms that reached land were less likely to die, and prokaryotes began to multiply and become better adapted to survival out of the water. Prokaryotes had likely colonized the land as early as 2.6 billion years ago[48] even before the origin of the eukaryotes. For a long time, the land remained barren of multicellular organisms. The supercontinent Pannotia formed around 600 million years ago and then broke apart a short 50 million years later. [49] Fish, the earliest vertebrates, evolved in the oceans around 530 million years ago.[50] A major extinction event occurred near the end of the Cambrian period,[51] which ended 488 million years ago[52]. Several hundred million years ago, plants (probably resembling algae) and fungi started growing at the edges of the water, and then out of it.[53] The oldest fossils of land fungi and plants date to 480–460 million years ago, though molecular evidence suggests the fungi may have colonized the land as early as 1000 million years ago and the plants 700 million years ago.[54] Initially remaining close to the water’s edge, mutations and variations resulted in further colonization of this new environment. The timing of the first animals to leave the oceans is not precisely known: the oldest clear evidence is of arthropods on land around 450 million years ago[55], perhaps thriving and becoming better adapted due to the vast food source provided by the terrestrial plants. There is also some unconfirmed evidence that arthropods may have appeared on land as early as 530 million years ago[56]. At the end of the Ordovician period, 440 million years ago, additional extinction events occurred, perhaps due to a concurrent ice age.[57] Around 380 to 375 million years ago, the first tetrapods evolved from fish.[58] It is thought that perhaps fins evolved to become limbs which allowed the first tetrapods to lift their heads out of the water to breathe air. This would let them survive in oxygen-poor water or pursue small prey in shallow water.[58] They may have later ventured on land for brief periods. Eventually, some of them became so well adapted to terrestrial life that they spent their adult lives on land, although they hatched in the water and returned to lay their eggs. This was the origin of the amphibians. About 365 million years ago, another period of extinction occurred, perhaps as a result of global cooling.[59] Plants evolved seeds, which dramatically accelerated their spread on land, around this time (by approximately 360 million years ago).[60],[61]

Pangaea, the most recent supercontinent, existed from 300 to 180 million years ago. The outlines of the modern continents and other land masses are indicated on this map. Some 20 million years later (340 million years ago[62]), the amniotic egg evolved, which could be laid on land, giving a survival advantage to tetrapod embryos. This resulted in the divergence of amniotes from amphibians. Another 30 million years (310 million years ago[63]) saw the divergence of the synapsids (including mammals) from the sauropsids (including birds and non-avian, non-mammalian reptiles). Other groups of organisms continued to evolve and lines diverged—in fish, insects, bacteria, and so on— but less is known of the details. 300 million years ago, the most recent hypothesized supercontinent formed, called Pangaea. The most severe extinction event to date took place 250 million years ago, at the boundary of the Permian and Triassic periods; 95% of life on Earth died out,[64] possibly due to the Siberian Traps volcanic event. The discovery of the Wilkes Land crater in Antarctica may suggest a connection with the Permian-Triassic extinction, but the age of that crater is not known. [65] But life persevered, and around 230 million years ago [66], dinosaurs split off from their reptilian ancestors. An extinction event between the Triassic and Jurassic periods 200 million years ago spared many of the dinosaurs,[67] and they soon became dominant among the vertebrates. Though some of the mammalian lines began to separate during this period, existing mammals were probably all small animals resembling shrews.[68] By 180 million years ago, Pangaea broke up into Laurasia and Gondwana. The boundary between avian and non-avian dinosaurs is not clear, but Archaeopteryx, traditionally considered one of the

first birds, lived around 150 million years ago.[69] The earliest evidence for the angiosperms evolving flowers is during the Cretaceous period, some 20 million years later (132 million years ago) [70] Competition with birds drove many pterosaurs to extinction, and the dinosaurs were probably already in decline for various reasons[71] when, 65 million years ago, a 10-kilometer meteorite likely struck Earth just off the Yucatán Peninsula, ejecting vast quantities of particulate matter and vapor into the air that occluded sunlight, inhibiting photosynthesis. Most large animals, including the non-avian dinosaurs, became extinct.[72] marking the end of the Cretaceous period and Mesozoic era. Thereafter, in the Paleocene epoch, mammals rapidly diversified, grew larger, and became the dominant vertebrates. Perhaps a couple of million years later (around 63 million years ago), the last common ancestor of primates lived.[73] By the late Eocene epoch, 34 million years ago, some terrestrial mammals had returned to the oceans to become animals such as Basilosaurus which later gave rise to dolphins and whales.[74]

[edit] Humanity Australopithecus africanus, an early hominid. Main article: Human evolution A small African ape living around six million years ago was the last animal whose descendants would include both modern humans and their closest relatives, the bonobos, and chimpanzees.[75] Only two branches of its family tree have surviving descendants. Very soon after the split, for reasons that are still debated, apes in one branch developed the ability to walk upright.[76] Brain size increased rapidly, and by 2 million years ago, the very first animals classified in the genus Homo had appeared.[77] Of course, the line between different species or even genera is rather arbitrary as organisms continuously change over generations. Around the same time, the other branch split into the ancestors of the common chimpanzee and the ancestors of the bonobo as evolution continued simultaneously in all life forms.[75] The ability to control fire likely began in Homo erectus (or Homo ergaster), probably at least 790,000 years ago[78] but perhaps as early as 1.5 million years ago.[79] In addition it has sometimes suggested that the use and discovery of controlled fire may even predate Homo erectus. Fire was possibly used by the early Lower Paleolithic (Oldowan) hominid Homo habilis and/or by robust australopithecines such as Paranthropus.[80] However it is more difficult to establish the origin of language; it is unclear whether Homo erectus could speak or if that capability had not begun until Homo sapiens.[81] As brain size increased, babies were born sooner, before their heads grew too large to pass through the pelvis. As a result, they exhibited more plasticity, and thus possessed an increased capacity to learn and required a longer period of dependence. Social skills became more complex, language became more advanced, and tools became more elaborate. This contributed to further cooperation and brain development.[82] Anatomically modern humans — Homo sapiens — are believed to have originated somewhere around 200,000 years ago or earlier in Africa; the oldest fossils date back to around 160,000 years ago.[83] The first humans to show evidence of spirituality are the Neanderthals (usually classified as a separate species with no surviving descendants); they buried their dead, often apparently with food or tools.[84] However, evidence of more sophisticated beliefs, such as the early Cro-Magnon cave paintings (probably with magical or religious significance)[85] did not appear until some 32,000 years ago.[86] Cro-Magnons also left behind stone figurines such as Venus of Willendorf, probably also signifying religious belief.[85] By 11,000 years ago, Homo sapiens had reached the southern tip of South America, the last of the uninhabited continents (except for Antartica, which remained undiscovered until 1820 AD) .[87] Tool use and language continued to improve; interpersonal relationships became more complex.

[edit] Civilization

Main article: History of the world Vitruvian Man by Leonardo da Vinci epitomizes the advances in art and science seen during the Renaissance. Throughout more than 90% of its history, Homo sapiens lived in small bands as nomadic hunter-gatherers.[88] As language became more complex, the ability to remember and transmit information resulted in a new sort of replicator: the meme.[89] Ideas could be rapidly exchanged and passed down the generations. Cultural evolution quickly outpaced biological evolution, and history proper began. Somewhere between 8500 and 7000 BC, humans in the Fertile Crescent in Middle East began the systematic husbandry of plants and animals: agriculture.[90] This spread to neighboring regions, and also developed independently elsewhere, until most Homo sapiens lived sedentary lives in permanent settlements as farmers. Not all societies abandoned nomadism, especially those in isolated areas of the globe poor in domesticable plant species, such as Australia.[91] However, among those civilizations that did adopt agriculture, the relative security and increased productivity provided by farming allowed the population to expand. Agriculture had a major impact; humans began to affect the environment as never before. Surplus food allowed a priestly or governing class to arise, followed by increasing division of labor. This led to Earth’s first civilization at Sumer in the Middle East, between 4000 and 3000 BC.[92] Additional civilizations quickly arose in ancient Egypt, at the Indus River valley and in China. Starting around 3000 BC, Hinduism, one of the oldest religions still practiced today, began to take form. [93] Others soon followed. The invention of writing enabled complex societies to arise: record-keeping and libraries served as a storehouse of knowledge and increased the cultural transmission of information. Humans no longer had to spend all their time working for survival—curiosity and education drove the pursuit of knowledge and wisdom. Various disciplines, including science (in a primitive form), arose. New civilizations sprang up, traded with one another, and engaged in war for territory and resources: empires began to form. By around 500 BC, there were empires in the Middle East, Iran, India, China, and Greece, approximately on equal footing; at times one empire expanded, only to decline or be driven back later.[94] In the fourteenth century, the Renaissance began in Italy with advances in religion, art, and science.[95] Starting around 1500, European civilization began to undergo changes leading to the scientific and industrial revolutions: that continent began to exert political and cultural dominance over human societies around the planet.[96] From 1914 to 1918 and 1939 to 1945, nations around the world were embroiled in world wars. Established following World War I, the League of Nations was a first step in establishing international institutions to resolve disputes peacefully; after its failure to prevent World War II and the subsequent end of the conflict it was replaced by the United Nations. In 1992, several European nations joined together in the European Union. As transportation and communication improved, the economies and political affairs of nations around the world have become increasingly intertwined. This globalization has often produced discord, although increased collaboration has resulted as well. Further information: History Antarctica, and History of Eurasia

[edit] Recent events Main article: Modern era

of

Africa, History

of

the

Americas, History

of

Four and a half billion years after the planet's formation, one of Earth’s life forms broke free of the biosphere. For the first time in history, Earth was viewed first hand from the vantage of space. Change has continued at a rapid pace from the mid-1940s to today. Technological developments include nuclear weapons, computers, genetic engineering, and nanotechnology. Economic globalization spurred by advances in communication and transportation technology has influenced everyday life in many parts of the world. Cultural and institutional forms such as democracy, capitalism, and environmentalism have increased influence. Major concerns and problems such as disease, war, poverty, violent radicalism, and more recently, global warming have risen as the world population increases. In 1957, the Soviet Union launched the first artificial satellite into orbit and, soon afterward, Yuri Gagarin became the first human in space. Neil Armstrong, an American, was the first to set foot on another astronomical object, the Earth's Moon. Unmanned probes have been sent to all the major planets in the solar system, with some (such as Voyager) having left the solar system. The Soviet Union and the United States of America were the primary early leaders in space exploration in the 20th Century. Five space agencies, representing over fifteen countries,[97] have worked together to build the International Space Station. Aboard it, there has been a continuous human presence in space since 2000.[98] See also: Modernity and Future

[edit] See also • • • • • • • • •

Timeline of the Big Bang Geologic time scale Timeline of evolution Detailed logarithmic timeline Natural history History of the world End of civilization Timetable of the Precambrian Geological history of Earth

[edit] References

Organism

From Wikipedia, the free encyclopedia

Jump to: navigation, search "Life on Earth" redirects here. For other uses, see Life on Earth (TV series). See also: Organism (philosophy) This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2007) Life

on

Earth

Fossil range: Late Hadean - Recent These Escherichia coli cells provide an example of a prokaryotic microorganism

Scientific classification (unranked): Life on Earth (Gaeabionta) Domains and Kingdoms • Cellular life o Bacteria o Neomura  Archaea  Eukarya  Bikonta  Rhizaria  Excavata  Chromalveolata  Plantae  Unikonta  Amoebozoa  Fungi  Animalia •

Non-cellular life (viruses) **

In biology, an organism is a living thing (such as animal, plant, fungus, or micro-organism). In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many billions of cells grouped into specialized tissues and organs. The term multicellular (many-celled) describes any organism made up of more than one cell. The term "organism" (Greek ὀργανισμός - organismos, from Ancient Greek ὄργανον - organon "organ, instrument, tool") first appeared in the English language in 1701 and took on its current definition by 1834 (Oxford English Dictionary).

Organisms may be divided into the prokaryotic and eukaryotic groups. The prokaryotes represent two separate domains, the Bacteria and Archaea.[1] All fungi, animals and plants are eukaryotes. The word "organism" may broadly be defined as an assembly of molecules that function as a more or less stable whole and has the properties of life. However, many sources propose definitions that exclude viruses and theoretically-possible man-made non-organic life forms.[2] Viruses are dependent on the biochemical machinery of a host cell for reproduction. Chambers Online Reference provides a broad definition: "any living structure, such as a plant, animal, fungus or bacterium, capable of growth and reproduction"[3]. In multicellular life the word "organism" usually describes the whole hierarchical assemblage of systems (for example circulatory, digestive, or reproductive) themselves collections of organs; these are, in turn, collections of tissues, which are themselves made of cells. In some plants and the nematode Caenorhabditis elegans, individual cells are totipotent.

A polypore mushroom has relationship with its host

parasitic

An ericoid mycorrhizal fungus Herpes simplex virus

Contents [hide]

[edit] Viruses

Viruses are not typically considered to be organisms because they are incapable of "independent" reproduction or metabolism. This controversy is problematic, though, since some • parasites and endosymbionts are also incapable of independent life. • Although viruses have a few enzymes • and molecules characteristic of living organisms, they are incapable of reproducing outside a host cell and • most of their metabolic processes require a host and its 'genetic • 9 External links machinery' such as organelles in eukaryotic hosts and the assemblage of ready-made enzymes (which the virus cannot make by itself) in prokaryotic hosts. While viruses sustain no independent metabolism, and thus are usually not accounted organisms, they do have their own genes and they do evolve by the same mechanisms by which organisms evolve. • • • •

1 Viruses 2 Superorganism 3 Organizational terminology 4 Chemistry o 4.1 Macromolecules 5 Structure o 5.1 The cell 6 Life span 7 Evolution o 7.1 History of life o 7.2 Horizontal gene transfer, and the history of life 8 References

[edit] Superorganism

Main article: Superorganism A superorganism is an organism consisting of many organisms. This is usually meant to be a social unit of eusocial animals, where division of labor is highly specialized and where individuals are not able to survive by themselves for extended periods of time. Ants are the most well known example of such a superorganism. Thermoregulation, a feature usually exhibited by individual organisms, does not occur in individuals or small groups of honeybees of the species Apis mellifera. When these bees pack together in clusters of between 5000 and 40000, the colony can thermoregulate. [4] James Lovelock, with his "Gaia Theory" has paralleled the work of Vladimir Vernadsky, who suggested the whole of the biosphere in some respects can be considered as a superorganism.

A sea sponge is a very simple type of multicellular organism The concept of superorganism is under dispute, as many biologists maintain that in order for a social unit to be considered an organism by itself, the individuals should be in permanent physical connection to each other, and its evolution should be governed by selection to the whole society instead of individuals. While it's generally accepted that the society of eusocial animals is a unit of natural selection to at least some extent, most evolutionists claim that the individuals are still the primary units of selection. The question remains "What is to be considered the individual?". Darwinians like Richard Dawkins suggest that the individual selected is the "Selfish Gene". Others believe it is the whole genome of an organism. E.O. Wilson has shown that with ant-colonies and other social insects it is the breeding entity of the colony that is selected, and not its individual members. This could apply to the bacterial members of a stromatolite, which, because of genetic sharing, in some way comprise a single gene pool. Gaian theorists like Lynn Margulis would argue this applies equally to the symbiogenesis of the bacterial underpinnings of the whole of the Earth. It would appear, from computer simulations like Daisyworld that biological selection occurs at multiple levels simultaneously. It is also argued that humans are actually a superorganism that includes microorganisms such as bacteria. It is estimated that "the human intestinal microbiota is composed of 1013 to 1014 microorganisms whose collective genome ("microbiome") contains at least 100 times as many genes as our own[...] Our microbiome has significantly enriched metabolism of glycans, amino acids, and xenobiotics; methanogenesis; and 2-methyl-D-erythritol 4-phosphate pathway–mediated biosynthesis of vitamins and isoprenoids. Thus, humans are superorganisms whose metabolism represents an amalgamation of microbial and human attributes." [5]. An NIH-coordinated and -funded effort is currently in progress to characterize the human microbiome.

[edit] Organizational terminology All organisms are classified by the science of alpha taxonomy into either taxa or clades. Taxa are ranked groups of organisms which run from the general (domain) to the specific (species). A broad scheme of ranks in hierarchical order is:

• • • • • • • •

Domain Kingdom Phylum Class Order Family Genus Species

To give an example, Homo sapiens is the Latin binomial equating to modern humans. All members of the species sapiens are, at least in theory, genetically able to interbreed. Several species may belong to a genus, but the members of different species within a genus are unable to interbreed to produce fertile offspring. Homo, however, only has one surviving species (sapiens); Homo erectus, Homo neanderthalensis, &c. having become extinct thousands of years ago. Several genera belong to the same family and so on up the hierarchy. Eventually, the relevant kingdom (Animalia, in the case of humans) is placed into one of the three domains depending upon certain genetic and structural characteristics. All living organisms known to science are given classification by this system such that the species within a particular family are more closely related and genetically similar than the species within a particular phylum.

A crab is an example of an organism.

[edit] Chemistry Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival. The molecular phenomena of chemistry are fundamental in understanding organisms, but it is a philosophical error (reductionism) to reduce organismal biology to mere chemistry. It is generally the phenomena of entire organisms that determine their fitness to an environment and therefore the survivability of their DNA based genes. Organisms clearly owe their origin, metabolism, and many other internal functions to chemical phenomena, especially the chemistry of large organic molecules. Organisms are complex systems of chemical compounds which, through interaction with each other and the environment, play a wide variety of roles. Organisms are semi-closed chemical systems. Although they are individual units of life (as the definition requires) they are not closed to the environment around them. To operate they constantly take in and release energy. Autotrophs produce usable energy (in the form of organic compounds) using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment. The primary chemical element in these compounds is carbon. The physical properties of this element such as its great affinity for bonding with other small atoms, including other carbon atoms, and its small size makes it capable of forming multiple bonds, make it ideal as the basis of organic life. It is able to form small compounds containing three atoms (such as carbon dioxide) as well as large chains of many thousands of atoms which are able to store data (nucleic acids), hold cells together and transmit information (protein).

[edit] Macromolecules The compounds which make up organisms may be divided into macromolecules and other, smaller molecules. The four groups of macromolecule are nucleic acids, proteins, carbohydrates and lipids. Nucleic acids (specifically deoxyribonucleic acid, or DNA) store genetic data as a sequence of nucleotides. The particular sequence of the four different types of nucleotides (adenine, cytosine, guanine, and thymine) dictate the many characteristics which constitute the organism. The sequence is divided up into codons, each of which is a particular sequence of three nucleotides and corresponds to a particular amino acid. Thus a sequence of DNA codes for a particular protein which, due to the chemical properties of the amino acids of which it is made, folds in a particular manner and so performs a particular function. The following functions of protein have been recognized: 1. 2. 3. 4. 5.

Enzymes, which catalyze all of the reactions of metabolism; Structural proteins, such as tubulin, or collagen; Regulatory proteins, such as transcription factors or cyclins that regulate the cell cycle; Signaling molecules or their receptors such as some hormones and their receptors; Defensive proteins, which can include everything from antibodies of the immune system, to toxins (e.g., dendrotoxins of snakes), to proteins that include unusual amino acids like canavanine.

Lipids make up the membrane of cells which constitutes a barrier, containing everything within the cell and preventing compounds from freely passing into, and out of, the cell. In some multi-cellular organisms they serve to store energy and mediate communication between cells. Carbohydrates also store and transport energy in some organisms, but are more easily broken down than lipids.

[edit] Structure All organisms consist of monomeric units called cells; some contain a single cell (unicellular) and others contain many units (multicellular). Multicellular organisms are able to specialize cells to perform specific functions, a group of such cells is tissue the four basic types of which are epithelium, nervous tissue, muscle tissue and connective tissue. Several types of tissue work together in the form of an organ to produce a particular function (such as the pumping of the blood by the heart, or as a barrier to the environment as the skin). This pattern continues to a higher level with several organs functioning as an organ system to allow for reproduction, digestion, &c. Many multicelled organisms comprise of several organ systems which coordinate to allow for life.

[edit] The cell The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells; all cells come from preexisting cells; all vital functions of an organism occur within cells, and cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. There are two types of cells, eukaryotic and prokaryotic. Prokaryotic cells are usually singletons, while eukaryotic cells are usually found in multi-cellular organisms. Prokaryotic cells lack a nuclear membrane so DNA is unbound within the cell, eukaryotic cells have nuclear membranes. All cells, whether prokaryotic or eukaryotic, have a membrane, which envelopes the cell, separates its interior from its environment, regulates what moves in and out, and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the

hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. All cells share several abilities[6]: • • •

• •

Reproduction by cell division (binary fission, mitosis or meiosis). Use of enzymes and other proteins coded for by DNA genes and made via messenger RNA intermediates and ribosomes. Metabolism, including taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is derived from metabolic pathways. Response to external and internal stimuli such as changes in temperature, pH or nutrient levels. Cell contents are contained within a cell surface membrane that contains proteins and a lipid bilayer.

[edit] Life span One of the basic parameters of organism is its life span. Some organisms live as short as one day, while some plants can live thousands of years. Aging is important when determining life span of most organisms, bacterium, a virus or even a prion.[citation needed]

[edit] Evolution See also: Common descent and Origin of life A hypothetical phylogenetic tree of all extant organisms, based on 16S rRNA gene sequence data, showing the evolutionary history of the three domains of life, bacteria, archaea and eukaryotes. Originally proposed by Carl Woese. In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool.

Modern eukaryotic taxonomy. Evidence for common descent may be found in traits shared between all living organisms. In Darwin's day, the evidence of shared traits was based solely on visible observation of morphologic similarities, such as the fact that all birds have wings, even those which do not fly. Today, there is strong evidence from genetics that all organisms have a common ancestor. For example, every living cell makes use of nucleic acids as its genetic material, and uses the same twenty amino acids as the building blocks for proteins. The universality of these traits strongly suggests common ancestry. The "Last Universal Ancestor" is the name given to the hypothetical single cellular organism or single cell that gave rise to all life on Earth 3.9 to 4.1 billion years ago; however, this hypothesis has since been refuted on many grounds.[citation needed] For example, it was once thought that the genetic code was universal (see: universal genetic code), but differences in the genetic code and differences in how each organism

translates nucleic acid sequences into proteins, provide support that there never was any "last universal common ancestor."[citation needed] Back in the early 1970s, evolutionary biologists thought that a given piece of DNA specified the same protein subunit in every living thing, and that the genetic code was thus universal. Since this is something unlikely to happen by chance, it was interpreted as evidence that every organism had inherited its genetic code from a single common ancestor, aka., the "Last Universal Ancestor." In 1979, however, exceptions to the code were found in mitochondria, [citation needed] the tiny energy factories inside cells. Biologists subsequently found exceptions in bacteria and in the nuclei of algae and single-celled animals.[citation needed] It is now clear that the genetic code is not the same in all living things, and that it does not provide powerful evidence that all living things evolved on a single tree of life. [7] Further support that there is no "Last Universal Ancestor" has been provided over the years by Lateral gene transfer in both prokaryote and eukaryote single cell organisms. This is why phylogenetic trees cannot be rooted, why almost all phylogenetic trees have different branching structures, particularly near the base of the tree, and why many organisms have been found with codons and sections of their DNA sequence that are unrelated to any other species.[citation needed] Information about the early development of life includes input from the fields of geology and planetary science. These sciences provide information about the history of the Earth and the changes produced by life. However, a great deal of information about the early Earth has been destroyed by geological processes over the course of time.

[edit] History of life Main article: Timeline of evolution The chemical evolution from self-catalytic chemical reactions to life (see Origin of life) is not a part of biological evolution, but it is unclear at which point such increasingly complex sets of reactions became what we would consider, today, to be living organisms.

Precambrian stromatolites in the Siyeh Formation, Glacier National Park. In 2002, William Schopf of UCLA published a controversial paper in the journal Nature arguing that formations such as this possess 3.5 billion year old fossilized algae microbes. If true, they would be the earliest known life on earth. Not much is known about the earliest developments in life. However, all existing organisms share certain traits, including cellular structure and genetic code. Most scientists interpret this to mean all existing organisms share a common ancestor, which had already developed the most fundamental cellular processes, but there is no scientific consensus on the relationship of the three domains of life (Archaea, Bacteria, Eukaryota) or the origin of life. Attempts to shed light on the earliest history of life generally focus on the behavior of macromolecules, particularly RNA, and the behavior of complex systems. The emergence of oxygenic photosynthesis (around 3 billion years ago) and the subsequent emergence of an oxygen-rich, non-reducing atmosphere can be traced through the formation of banded iron deposits, and later red beds of iron oxides. This was a necessary prerequisite for the development of aerobic cellular respiration, believed to have emerged around 2 billion years ago.

In the last billion years, simple multicellular plants and animals began to appear in the oceans. Soon after the emergence of the first animals, the Cambrian explosion (a period of unrivaled and remarkable, but brief, organismal diversity documented in the fossils found at the Burgess Shale) saw the creation of all the major body plans, or phyla, of modern animals. This event is now believed to have been triggered by the development of the Hox genes. About 500 million years ago, plants and fungi colonized the land, and were soon followed by arthropods and other animals, leading to the development of land ecosystems with which we are familiar. The evolutionary process may be exceedingly slow. Fossil evidence indicates that the diversity and complexity of modern life has developed over much of the history of the earth. Geological evidence indicates that the Earth is approximately 4.6 billion years old. Studies on guppies by David Reznick at the University of California, Riverside, however, have shown that the rate of evolution through natural selection can proceed 10 thousand to 10 million times faster than what is indicated in the fossil record. [8]. Such comparative studies however are invariably biased by disparities in the time scales over which evolutionary change is measured in the laboratory, field experiments, and the fossil record.

[edit] Horizontal gene transfer, and the history of life The ancestry of living organisms has traditionally been reconstructed from morphology, but is increasingly supplemented with phylogenetics - the reconstruction of phylogenies by the comparison of genetic (DNA) sequence. "Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic 'domains'. Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes." [9] Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research", therefore "biologists [should] use the metaphor of a mosaic to describe the different histories combined in individual genomes and use [the] metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes." [10]

[edit] References

Animal From Wikipedia, the free encyclopedia

Jump to: navigation, search

"Animalia" redirects here. For other uses, see Animalia (disambiguation). For other uses, see Animal (disambiguation). Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. Animals are also heterotrophs, meaning they must ingest other organisms for sustenance. Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago.

Contents [hide] • •

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• • • •

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1 Etymology 2 Characteristics o 2.1 Structure o 2.2 Reproduction and development 3 Origin and fossil record 4 Groups of animals o 4.1 Deuterostomes o 4.2 Ecdysozoa o 4.3 Platyzoa o 4.4 Lophotrochozoa 5 Model organisms 6 History of classification 7 See also 8 References o 8.1 Notes o 8.2 Bibliography 9 External links

Etymology The word "animal" comes from the Latin word animale, neuter of animalis, and is derived from anima, meaning vital breath or soul. In everyday colloquial usage, the word usually refers to non-human animals. The biological definition of the word refers to all members of the Kingdom Animalia, including humans.[1]

Characteristics Animals have several characteristics that set them apart from other living things. Animals are eukaryotic and usually multicellular[2] (although see Myxozoa), which separates them from bacteria and most protists. They are heterotrophic,[3] generally digesting food in an internal chamber, which separates

them from plants and algae (some sponges are capable of photosynthesis and nitrogen fixation though).[4] They are also distinguished from plants, algae, and fungi by lacking cell walls.[5] All animals are motile,[6] if only at certain life stages. In most animals, embryos pass through a blastula stage, which is a characteristic excluhttp://en.wikipedia.org/wiki/Evolutionary_history_of_plantssive to animals.

Structure With a few exceptions, most notably the sponges (Phylum Porifera) and Placozoa, animals have bodies differentiated into separate tissues. These include muscles, which are able to contract and control locomotion, and nerve tissue, which sends and processes signals. There is also typically an internal digestive chamber, with one or two openings. Animals with this sort of organization are called metazoans, or eumetazoans when the former is used for animals in general.

and fungi have cells held in place by develop by progressive growth. Also, cells are the following intercellular junctions, gap junctions, and

All animals have eukaryotic cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones, and spicules. During development it forms a relatively flexible framework upon which cells can move about and be reorganized, making complex structures possible. In contrast, other multicellular organisms like plants cell walls, and so unique to animal junctions: tight desmosomes.

Reproduction and development Nearly all animals undergo some form reproduction. Adults are diploid or a few specialized reproductive cells, meiosis to produce smaller motile non-motile ova. These fuse to form develop into new individuals.

of sexual polyploid. They have which undergo spermatozoa or larger zygotes, which

A newt lung cell stained with fluorescent dyes undergoing mitosis, specifically early anaphase. Many animals are also capable of asexual reproduction. This may take place through parthenogenesis, where fertile eggs are produced without mating, or in some cases through fragmentation. A zygote initially develops into a hollow sphere, called a blastula, which undergoes rearrangement and differentiation. In sponges, blastula larvae swim to a new location and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first invaginates to form a gastrula with a digestive chamber, and two separate germ layers - an external ectoderm and an internal endoderm. In most cases, a mesoderm also develops between them. These germ layers then differentiate to form tissues and organs. Most animals grow by indirectly using the energy of sunlight. Plants use this energy to convert sunlight into simple sugars using a process known as photosynthesis. Starting with the molecules carbon dioxide (CO2) and water (H2O), photosynthesis converts the energy of sunlight into chemical energy stored in the bonds of glucose (C6H12O6) and releases oxygen (O2). These sugars are then used as the building blocks which allow the plant to grow. When animals eat these plants (or eat other animals which have eaten plants), the sugars produced by the plant are used by the animal. They are either used directly to help the animal grow, or broken down, releasing stored solar energy, and giving the animal the energy required for motion. This process is known as glycolysis. Animals who live close to hydrothermal vents and cold seeps on the ocean floor are not dependent on the energy of sunlight. Instead, chemosynthetic archaea and bacteria form the base of the food chain.

Origin and fossil record Animals are generally considered to have evolved from a flagellated eukaryote. Their closest known living relatives are the choanoflagellates, collared flagellates that have a morphology similar to the choanocytes of certain sponges. Molecular studies place animals in a supergroup called the opisthokonts, which also include the choanoflagellates, fungi and a few small parasitic protists. The name comes from the posterior location of

the flagellum in motile cells, such as most animal spermatozoa, whereas other eukaryotes tend to have anterior flagella.

Dunkleosteus was a gigantic, 10 meter (33 ft) long prehistoric fish.[7] The first fossils that might represent animals appear towards the end of the Precambrian, around 610 million years ago, and are known as the Ediacaran or Vendian biota. These are difficult to relate to later fossils, however. Some may represent precursors of modern phyla, but they may be separate groups, and it is possible they are not really animals at all. Aside from them, most known animal phyla make a more or less simultaneous appearance during the Cambrian period, about 542 million years ago. It is still disputed whether this event, called the Cambrian explosion, represents a rapid divergence between different groups or a change in conditions that made fossilization possible. However some paleontologists and geologists would suggest that animals appeared much earlier than previously thought, possibly even as early as 1 billion years ago. Trace fossils such as tracks and burrows found in Tonian era strata in India indicate the presence of triploblastic worm like metazoans roughly as large (about 5 mm wide) and complex as earthworms.[8] In addition during the beginning of the Tonian period around 1 billion years ago (roughly the same time that the trace fossils previously discussed in this article date back to) there was a decrease in Stromatolite diversity which may indicate the appearance of grazing animals during this time as Stromatolites also increased in diversity shortly after the end-Ordovician and end-Permian rendered large amounts of grazing marine animals extinct and decreased shortly after their populations recovered. However some other scientists doubt that these fossils are authentic and have suggested these trace fossils are just the result of natural processes such as erosion.[citation needed] The discovery that tracks very similar to these early trace fossils are produced today by the giant single-celled protist Gromia sphaerica casts further doubt on their interpretation as evidence of early animal evolution.[9][10]

Groups of animals Orange elephant ear sponge, Agelas clathrodes, in foreground. Two corals in the background: a sea fan, Iciligorgia schrammi, and a sea rod, Plexaurella nutans. The sponges (Porifera) were long thought to have diverged from other animals early. As mentioned above, they lack the complex organization found in most other phyla. Their cells are differentiated, but in most cases not organized into distinct tissues. Sponges are sessile and typically feed by drawing in water through pores. Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum. However, a phylogenomic study in 2008 of 150 genes in 21 genera[11] revealed that it is the Ctenophora or comb jellies which are the basal lineage of animals, at least among those 21 phyla. The authors speculate that sponges—or at least those lines of sponges they investigated—are not so primitive, but may instead be secondarily simplified. Among the other phyla, the Ctenophora and the Cnidaria, which includes sea anemones, corals, and jellyfish, are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus. Both have distinct tissues, but they are not organized into organs. There are only

two main germ layers, the ectoderm and endoderm, with only scattered cells between them. As such, these animals are sometimes called diploblastic. The tiny Placozoans are similar, but they do not have a permanent digestive chamber. The remaining animals form a monophyletic group called the Bilateria. For the most part, they are bilaterally symmetric, and often have a specialized head with feeding and sensory organs. The body is triploblastic, i.e. all three germ layers are well-developed, and tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is also an internal body cavity called a coelom or pseudocoelom. There are exceptions to each of these characteristics, however - for instance adult echinoderms are radially symmetric, and certain parasitic worms have extremely simplified body structures. Genetic studies have considerably changed our understanding of the relationships within the Bilateria. Most appear to belong to two major lineages: the Deuterostomes and Protostomes, which includes the Ecdysozoa, Platyzoa, and Lophotrochozoa. In addition, there are a few small groups of bilaterians with relatively similar structure that appear to have diverged before these major groups. These include the Acoelomorpha, Rhombozoa, and Orthonectida. The Myxozoa, single-celled parasites that were originally considered Protozoa, are now believed to have developed from the Bilateria as well.

Deuterostomes

Superb Fairy-wren, Malurus cyaneus Deuterostomes differ from the other Bilateria, called protostomes, in several ways. In both cases there is a complete digestive tract. However, in protostomes the initial opening (the archenteron) develops into the mouth, and an anus forms separately. In deuterostomes this is reversed. In most protostomes, cells simply fill in the interior of the gastrula to form the mesoderm, called schizocoelous development, but in deuterostomes it forms through invagination of the endoderm, called enterocoelic pouching. Deuterostomes also have a dorsal, rather than a ventral, nerve chord and their embryos undergo different cleavage. All this suggests the deuterostomes and protostomes are separate, monophyletic lineages. The main phyla of deuterostomes are the Echinodermata and Chordata. The former are radially symmetric and exclusively marine, such as starfish, sea urchins, and sea cucumbers. The latter are dominated by the vertebrates, animals with backbones. These include fish, amphibians, reptiles, birds, and mammals. In addition to these, the deuterostomes also include the Hemichordata or acorn worms. Although they are not especially prominent today, the important fossil graptolites may belong to this group. The Chaetognatha or arrow worms may also be deuterostomes, but more recent studies suggest protostome affinities.

Ecdysozoa

Yellow-winged Darter, Sympetrum flaveolum

The Ecdysozoa are protostomes, named after the common trait of growth by moulting or ecdysis. The largest animal phylum belongs here, the Arthropoda, including insects, spiders, crabs, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. Two smaller phyla, the Onychophora and Tardigrada, are close relatives of the arthropods and share these traits. The ecdysozoans also include the Nematoda or roundworms, the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the Nematomorpha or horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera. These groups have a reduced coelom, called a pseudocoelom. The remaining two groups of protostomes are sometimes grouped together as the Spiralia, since in both embryos develop with spiral cleavage.

Platyzoa

Bedford's flatworm, Pseudobiceros bedfordi The Platyzoa include the phylum Platyhelminthes, the flatworms. These were originally considered some of the most primitive Bilateria, but it now appears they developed from more complex ancestors.[12] A number of parasites are included in this group, such as the flukes and tapeworms. Flatworms are acoelomates, lacking a body cavity, as are their closest relatives, the microscopic Gastrotricha.[13] The other platyzoan phyla are mostly microscopic and pseudocoelomate. The most prominent are the Rotifera or rotifers, which are common in aqueous environments. They also include the Acanthocephala or spiny-headed worms, the Gnathostomulida, Micrognathozoa, and possibly the Cycliophora.[14] These groups share the presence of complex jaws, from which they are called the Gnathifera.

Lophotrochozoa

Roman snail, Helix pomatia The Lophotrochozoa include two of the most successful animal phyla, the Mollusca and Annelida.[15][16] The former, which is the second-largest animal phylum, includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such as earthworms and leeches. These two groups have long been considered close relatives because of the common presence of trochophore larvae, but the annelids were considered closer to the arthropods,[17] because they are both segmented. Now this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla.[18]

The Lophotrochozoa also include the Nemertea or ribbon worms, the Sipuncula, and several phyla that have a fan of cilia around the mouth, called a lophophore.[19] These were traditionally grouped together as the lophophorates.[20] but it now appears they are paraphyletic,[21] some closer to the Nemertea and some to the Mollusca and Annelida.[22][23] They include the Brachiopoda or lamp shells, which are prominent in the fossil record, the Entoprocta, the Phoronida, and possibly the Bryozoa or moss animals.[24]

Model organisms Main articles: Model organism and Animal testing Because of the great diversity found in animals, it is more economical for scientists to study a small number of chosen species so that connections can be drawn from their work and conclusions extrapolated about how animals function in general. Because they are easy to keep and breed, the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans have long been the most intensively studied metazoan model organisms, and were among the first lifeforms to be genetically sequenced. This was facilitated by the severely reduced state of their genomes, but the double-edged sword here is that with many genes, introns and linkages lost, these ecdysozoans can teach us little about the origins of animals in general. The extent of this type of evolution within the superphylum will be revealed by the crustacean, annelid, and molluscan genome projects currently in progress. Analysis of the starlet sea anemone genome has emphasised the importance of sponges, placozoans, and choanoflagellates, also being sequenced, in explaining the arrival of 1500 ancestral genes unique to the Eumetazoa.[25] An analysis of the homoscleromorph sponge Oscarella carmela also suggests that the last common ancestor of sponges and the eumetazoan animals was more complex than previously assumed.[26] Other model organisms belonging to the animal kingdom include the mouse (Mus musculus) and zebrafish (Danio rerio}.

History of classification

Carolus Linnaeus known as the father of modern taxonomy Aristotle divided the living world between animals and plants, and this was followed by Carolus Linnaeus (Carl von Linné), in the first hierarchical classification. Since then biologists have begun emphasizing evolutionary relationships, and so these groups have been restricted somewhat. For instance, microscopic protozoa were originally considered animals because they move, but are now treated separately. In Linnaeus's original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata, whereas the various other forms have been separated out. The above

lists represent our current understanding of the group, though there is some variation from source to source.

See also • • • • • •

Plant Fauna List of animal names Animal behavior Animal rights List of animals by number of neurons

References

Society From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Society (disambiguation).

Young people interacting within an ethnically diverse society. Society portal

A society is a population of humans characterized by patterns of relationships between individuals that share a distinctive culture and/or institutions. More broadly, a society is an economic, social and industrial infrastructure, in which a varied multitude of people are a part of. Members of a society may be from different ethnic groups. A society may be a particular people, such as the Saxons, a nation state, such as Bhutan, or a broader cultural group, such as a Western society. The word society may also refer to an organized voluntary association of people for religious, benevolent, cultural, scientific, political, patriotic, or other purpose. Sociology is the scientific, or academic, study of society and human behavior.

Contents [hide]

• • •

1 Origin and usage 2 Evolution of societies 3 Characteristics of society 4 Social networks 5 Organization of society o 5.1 Shared belief or common goal 6 Ontology 7 Notes 8 References

•

9 External links

• • • • •

[edit] Origin and usage The English word "society" emerged in the 15th century and is derived from the French société. The French word, in turn, had its origin in the Latin societas, a "friendly association with others," from socius meaning "companion, associate, comrade or business partner." The Latin word is probably related to the verb sequi, "to follow", and thus originally may have meant "follower". In political science, the term is often used to mean the totality of human relationships, generally in contrast to the State, i.e., the apparatus of rule or government within a territory: I mean by it [the State] that summation of privileges and dominating positions which are brought into being by extra-economic power... I mean by Society, the totality of concepts of all purely natural relations and institutions between man and man...[1]

In the social sciences such as sociology, society has been used[citation needed]to mean a group of people that form a semi-closed social system, in which most interactions are with other individuals belonging to the group. Society is sometimes contrasted with culture. For example, Clifford Geertz has suggested that society is the actual arrangement of social relations while culture is made up of beliefs and symbolic forms. According to sociologist Richard Jenkins, the term addresses a number of important existential issues facing people: 1. How humans think and exchange information – the sensory world makes up only a fraction of human experience. In order to understand the world, we have to conceive of human interaction in the abstract (i.e., society). 2. Many phenomena cannot be reduced to individual behavior. 3. Collectives often endure beyond the lifespan of individual members. 4. The human condition has always meant going beyond the evidence of our senses; every aspect of our lives is tied to the collective.[2]

[edit] Evolution of societies

A half-section of the 12th century Song Dynasty version of Night Revels of Han Xizai, original by Gu Hongzhong; the painting, which is a masterpiece of the era's artwork, portrays servants, musicians, monks, children, guests, hosts all in a single societal environment, serves as an in-depth look into 10th-century Chinese social structure.

According to anthropologist Maurice Godelier, one critical novelty in human society, in contrast to humanity's closest biological relatives (chimpanzees and bonobo), is the parental role assumed by the males, which were unaware of their "father" connection[clarification needed].[3][4] Gerhard Lenski, a sociologist, differentiates societies based on their level of technology, communication and economy: (1) hunters and gatherers, (2) simple agricultural, (3) advanced agricultural, (4) industrial.[5] and now (5) virtual. This is somewhat similar to the system earlier developed by anthropologists Morton H. Fried, a conflict theorist, and Elman Service, an integration theorist, who have produced a system of classification for societies in all human cultures based on the evolution of social inequality and the role of the state. This system of classification contains four categories: • • • •

Hunter-gatherer bands, which are generally egalitarian. Tribal societies in which there are some limited instances of social rank and prestige. Stratified structures led by chieftains. Civilizations, with complex social hierarchies and organized, institutional governments.

In addition to this there are: • •

Humanity, mankind, that upon which rest all the elements of society, including society's beliefs. Virtual-society is a society based on online identity, which is evolving in the information age.

Over time, some cultures have progressed toward more-complex forms of organization and control. This cultural evolution has a profound effect on patterns of community. Hunter-gatherer tribes settled around seasonal foodstocks to become agrarian villages. Villages grew to become towns and cities. Cities turned into city-states and nation-states.[6] Today, anthropologists and many social scientists vigorously oppose the notion of cultural evolution and rigid "stages" such as these. In fact, much anthropological data has suggested that complexity (civilization, population growth and density, specialization, etc.) does not always take the form of hierarchical social organization or stratification. Also, cultural relativism as a widespread approach/ethic has largely replaced notions of "primitive," better/worse, or "progress" in relation to cultures (including their material culture/technology and social organization).

[edit] Characteristics of society The following three components are common to all definitions of society: • •

Social networks Criteria for membership, and

•

Characteristic patterns of organization

Each of these will be explored further in the following sections.

[edit] Social networks Main article: Social network Social networks are maps of the relationships between people. Structural features such as proximity, frequency of contact and type of relationship (e.g., relative, friend, colleague) define various social networks.

[edit] Organization of society Main article: Social organization Human societies are often organized according to their primary means of subsistence. As noted in the section on "Evolution of societies", above, social scientists identify hunter-gatherer societies, nomadic pastoral societies, horticulturalist or simple farming societies, and intensive agricultural societies, also called civilizations. Some consider industrial and post-industrial societies to be qualitatively different from traditional agricultural societies. One common theme for societies in general is that they serve to aid individuals in a time of crisis. Traditionally, when an individual requires aid, for example at birth, death, sickness, or disaster, members of that society will rally others to render aid, in some form—symbolic, linguistic, physical, mental, emotional, financial, medical, or religious. Many societies will distribute largess, at the behest of some individual or some larger group of people. This type of generosity can be seen in all known cultures; typically, prestige accrues to the generous individual or group. Conversely, members of a society may also shun or scapegoat members of the society who violate its norms. Mechanisms such as gift-giving and scapegoating, which may be seen in various types of human groupings, tend to be institutionalized within a society. Social evolution as a phenomenon carries with itself certain elements that could be detrimental to the population it serves. Some societies will bestow status on an individual or group of people, when that individual or group performs an admired or desired action. This type of recognition is bestowed by members of that society on the individual or group in the form of a name, title, manner of dress, or monetary reward. Males, in many societies, are particularly susceptible to this type of action and subsequent reward, even at the risk of their lives. Action by an individual or larger group in behalf of some cultural ideal is seen in all societies. The phenomena of community action, shunning, scapegoating, generosity, and shared risk and reward occur in subsistence-based societies and in more technology-based civilizations. Societies may also be organized according to their political structure. In order of increasing size and complexity, there are bands, tribes, chiefdoms, and state societies. These structures may have varying degrees of political power, depending on the cultural geographical, and historical environments that these societies must contend with. Thus, a more isolated society with the same level of technology and culture as other societies is more likely to survive than one in closer proximity to others that may encroach on their resources (see history for examples}. A society that is unable to offer an effective response to other societies it competes with will usually be subsumed into the culture of the competing society (see technology for examples).

[edit] Shared belief or common goal People of many nations united by common political and cultural traditions, beliefs, or values are sometimes also said to be a society (such as Judeo-Christian, Eastern, and Western). When used in this context, the term is employed as a means of contrasting two or more "societies" whose members represent alternative conflicting and competing worldviews (see Secret Societies). Some academic, learned and scholarly associations describe themselves as societies (for example, the American Mathematical Society). More commonly, professional organizations often refer to themselves as societies (e.g., the American Society of Civil Engineers, American Chemical Society). In the United Kingdom and the United States, learned societies are normally nonprofit and have charitable status. In science, they range in size to include national scientific societies (i.e., the Royal Society) to regional natural history societies. Academic societies may have interest in a wide range of subjects, including the arts, humanities and science. In some countries (for example the United States and France), the term "society" is used in commerce to denote a partnership between investors or the start of a business. In the United Kingdom, partnerships are not called societies, but cooperatives or mutuals are often known as societies (such as friendly societies and building societies). In Latin America, the term society may be used in commerce denoting a partnership between investors, or anonymous investors; for example: "Proveedor Industrial Anahuac S.A." where S.A. stands for Anonymous Society (Sociedad Anónima); however in Mexico in other type of partnership it would be declared as S.A. de C.V. or S.A. de R.L., indicating the level of commitment of capital and the responsibilities from each member towards their own association and towards the society in general and supervised by the corresponding jurisdictional civil and judicial authorities.

[edit] Ontology As a related note, there is still an ongoing debate in sociological and anthropological circles as to whether there exists an entity we could call society. Some Marxist theorists, like Louis Althusser, Ernesto Laclau and Slavoj Zizek, have argued that society is nothing more than an effect of the ruling ideology of a certain class system, and shouldn't be used as a sociological notion. Marx's concept of society as the sum total of social relations among members of a community contrasts with interpretations from the perspective of methodological individualism where society is simply the sum total of individuals in a territory. In 1987 Margaret Thatcher famously said "There is no such thing as society".[7]

[edit] Notes 1. 2. 3. 4. 5. 6. 7.

^ "The State by Franz Oppenheimer". Retrieved on 15 August, 2008. ^ Jenkins, R. 2002. Foundations of Sociology. ^ Maurice Godelier, Métamorphoses de la parenté, 2004 ^ "New Left Review - Jack Goody: The Labyrinth of Kinship". Retrieved on 2007-07-24. ^ Lenski, G. 1974. Human Societies: An Introduction to Macrosociology. ^ Effland, R. 1998. The Cultural Evolution of Civilizations. ^ There is no such thing as society - Margaret Thatcher

[edit] References

Behavior From Wikipedia, the free encyclopedia

Jump to: navigation, search It has been suggested that human behavior be merged into this article or section. (Discuss) This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (May 2007) For other uses, see Behavior (disambiguation). Behavior or behaviour (see spelling differences) refers to the actions or reactions of an object or organism, usually in relation to the environment. Behavior can be conscious or unconscious, overt or covert, and voluntary or involuntary.

Contents [hide] • • •

1 In animals 2 In psychology 3 Outside psychology

•

4 See also

[edit] In animals In animals, behavior is controlled by the endocrine system and the nervous system. The complexity of the behavior of an organism is related to the complexity of its nervous system. Generally, organisms with complex nervous systems have a greater capacity to learn new responses and thus adjust their behavior. Behaviors can be either innate or learned.

[edit] In psychology Human behavior (and that of other organisms and mechanisms) can be common, unusual, acceptable, or unacceptable. Humans evaluate the acceptability of behavior using social norms and regulate behavior by means of social control. In sociology, behavior is considered as having no meaning, being not directed at other people and thus is the most basic human action. Animal behavior is studied in comparative psychology, ethology, behavioral ecology and sociobiology. Behavior became an important construct in early 20th century Psychology with the advent of the paradigm known subsequently as "behaviorism." Behaviorism was a reaction against so-called "faculty" psychology which purported to see into or understand the mind without the benefit of scientific testing. Behaviorism insisted on working only with what can be seen or manipulated and in the early views of

John B. Watson, a founder of the field, nothing was inferred as to the nature of the entity that produced the behavior. Subsequent modifications of Watson's perspective and that of so-called "classical conditioning" (see under Ivan Pavlov) led to the rise of Operant Conditioning, a theory advocated by B.F. Skinner, which took over the academic establishment up through the 1950s and was synonymous with "behaviorism" for many. For studies on behavior ethograms are used.

[edit] Outside psychology Behavior as used in computer science is an anthropomorphic construct that assigns “life” to the activities carried out by a computer, computer application, or computer code in response to stimuli, such as user input. Also, "a behavior" is a reusable block of computer code or script that, when applied to an object (computer science), especially a graphical one, causes it to respond to user input in meaningful patterns or to operate independently, as if alive. In environmental modeling and especially in hydrology, a behavioral model means a model that is acceptably consistent with observed natural processes, i.e. that simulates well, for example, observed river discharge. It is a key concept of the so-called Generalized Likelihood Uncertainty Estimation (GLUE) methodology to quantify how uncertain environmental predictions are.

[edit] See also • • • • • • • • • • • • • • • • • • •

Animal behavior Applied behavior analysis Behavioral bias Behavioral economics Behaviorism Experimental analysis of behavior Forms of activity and interpersonal relations Human behavior Human sexual behavior Instinct Motive Normal (behavior) Psychology Radical behaviorism Reasoning Rebellion Taboo Theories of political behavior Work behavior

This psychology-related article is a stub. You can help Wikipedia by expanding it. Retrieved from "http://en.wikipedia.org/wiki/Behavior" Categories: Behavior | Psychology | Education-related terms | Human behavior | Psychology stubs Hidden categories: Articles to be merged since March 2008 | All articles to be merged | Articles lacking sources from May 2007 | All articles lacking sources

Nature From Wikipedia, the free encyclopedia

(Redirected from Natural) Jump to: navigation, search This article is about the physical universe. For other uses, see Nature (disambiguation). "Natural" redirects here. For other uses, see Natural (disambiguation).

Lightning strikes during the eruption of the Galunggung volcano in 1982

Much attention has been given to preserving the natural characteristics of Hopetoun Falls, Australia, while allowing ample access for visitors.

Bachalpsee in the Swiss Alps; generally mountainous areas are less affected by human activity. Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. "Nature" refers to the phenomena of the physical world, and also to life in general. Manufactured objects and human interaction generally are not considered part of nature unless qualified in ways such as "human nature" or "the whole of nature". Nature is generally distinguished from the supernatural. It ranges in scale from the subatomic to the galactic. The word nature is derived from the Latin word natura, or "the course of things, natural character."[1] Natura was a Latin translation of the Greek word physis (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of their own accord.[2] This is shown in the first written use of the word φύσις, in connection with a plant.[3] The concept of nature as a whole, the physical universe, is one of several expansions of the original notion; it began with certain core applications of the word φύσις by pre-Socratic philosophers, and has steadily gained currency ever since. This usage was confirmed during the advent of modern scientific method in the last several centuries.[4][5]

Within the various uses of the word today, "nature" may refer to the general realm of various types of living plants and animals, and in some cases to the processes associated with inanimate objects – the way that particular types of things exist and change of their own accord, such as the weather and geology of the Earth, and the matter and energy of which all these things are composed. It is often taken to mean the "natural environment" or wilderness – wild animals, rocks, forest, beaches, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. This more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, with the latter being understood as that which has been brought into being by a human consciousness or a human mind.

Contents [hide]

• • •

1 Etymology 2 Earth o 2.1 Historical perspective o 2.2 Atmosphere, climate and weather 3 Life o 3.1 Evolution o 3.2 Microbes o 3.3 Plants and animals o 3.4 Ecosystems 4 Human interrelationship o 4.1 Wilderness o 4.2 Beauty in nature 5 Matter and energy 6 Nature beyond Earth 7 See also

•

8 Notes and references

• •

•

•

[edit] Etymology Newton's Principia Mathematica (1687) used "nature" as a synonym for the physical universe. The word nature means the universe, with all its phenomena.[6] Natura was a Latin translation of the Greek word physis (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of their own accord.[7] The word φύσις occurs very early in Greek philosophy, generally in similar senses to those of the modern English word nature.[8] This is shown in the first written use of the word φύσις, in connection with a plant by Homer.[9] The concept of nature as a whole, the physical universe, is one of several expansions of the original notion. This usage was confirmed during the advent of modern scientific method. Isaac Newton's Philosophiae Naturalis Principia Mathematica (1687), for example, is translated "Mathematical Principles of Natural Philosophy". The etymology of the word "physical" shows its use as a synonym for "natural" in about the mid-15th century.[10]

[edit] Earth

View of the home planet, taken in 1972 by the Apollo 17 crew. This image is the only photograph of its kind to date, showing a fully sunlit hemisphere of the Earth. Main articles: Earth, Earth science, structure of the Earth, plate tectonics, and geology Earth (or, "the earth") is the only planet known to support life, and as such, its natural features are the subject of many fields of scientific research. Within the solar system, it is third nearest to the sun; it is the largest terrestrial planet and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region. [11] Precipitation varies widely with location, from several metres of water per year to less than a millimetre. About 70 percent of the surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several gradually migrating tectonic plates, which have changed relatively quickly several times. The interior remains active, with a thick layer of molten mantle and an iron-filled core that generates a magnetic field. The atmospheric conditions have been significantly altered from the original conditions by the presence of lifeforms,[12] which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods,[13] and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.[14][15]

[edit] Historical perspective Main article: History of Earth

Phylum Pediastrumboryanum. Plankton have existed on Earth for at least 2 billion years.[16] Earth is estimated to have formed 4.55 billion years ago from the solar nebula, along with the Sun and other planets.[17] The moon formed roughly 20 million years later. Initially molten, the outer layer of the planet cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial

atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources.[18] The highly energetic chemistry is believed to have produced a selfreplicating molecule around 4 billion years ago.[19] Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a supercontinent. Roughly 750 million years ago, the earliest known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia which broke apart about 540 million years ago, then finally Pangaea, which broke apart about 180 million years ago.[20]

Land-based plants and fungi have been part of nature on Earth for about the past 400 million years. These have needed to adapt and move many times as the continents and climates changed.[21][22] There is significant evidence, still being discussed among scientists, that a severe glacial action during the Neoproterozoic era covered much of the planet in a sheet of ice. This hypothesis has been termed the "Snowball Earth", and it is of particular interest as it precedes the Cambrian explosion in which multicellular life forms began to proliferate about 530–540 million years ago.[23] Since the Cambrian explosion there have been five distinctly identifiable mass extinctions.[24] The last mass extinction occurred some 65 million years ago, when a meteorite collision probably triggered the extinction of the non-avian dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life diversified.[25] Several million years ago, a species of small African ape gained the ability to stand upright.[26] The subsequent advent of human life, and the development of agriculture and further civilization allowed humans to affect the Earth more rapidly than any previous life form, affecting both the nature and quantity of other organisms as well as global climate. By comparison, the Oxygen Catastrophe, produced by the proliferation of algae during the Siderian period, required about 300 million years to culminate.) The present era is classified as part of a mass extinction event, the Holocene extinction event, the fastest ever to have occurred.[27][28] Some, such as E. O. Wilson of Harvard University, predict that human destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years.[29] The extent of the current extinction event is still being researched, debated and calculated by biologists.[30]

[edit] Atmosphere, climate and weather Main articles: Earth's atmosphere, climate, and weather The atmosphere of the Earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelops the Earth is held in place by the planet's gravity. Dry air consists of 78% nitrogen, 21% oxygen, 1% argon and other inert gases, carbon dioxide, etc.; but air also contains a variable amount of water vapor. The atmospheric pressure declines steadily with altitude, and has a scale height of about 8 kilometres at the Earth's surface: the height at which the atmospheric pressure has declined by a factor of

e (a mathematical constant equal to 2.71...).[31][32] The ozone layer of the Earth's atmosphere plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.

A supercell thunderstorm Terrestrial weather occurs almost exclusively in the lower part of the atmosphere, and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.

A tornado in central Oklahoma. Weather can have both beneficial and harmful effects. Extremes in weather, such as tornadoes or hurricanes and cyclones, can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals dependent on its growth for their food. The planetary climate is a measure of the long-term trends in the weather. Various factors are known to influence the climate, including ocean currents, surface albedo, greenhouse gases, variations in the solar luminosity, and changes to the planet's orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including ice ages. The climate of a region depends on a number of factors, especially latitude. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the tropical climate at the equator to the polar climate in the northern and southern extremes. Weather is also influenced by the seasons, which result from the Earth's axis being tilted relative to its orbital plane. Thus, at any given time during the summer or winter, one part of the planet is more directly exposed to the rays of the sun. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the northern and southern hemispheres experience opposite seasons.

Weather is a chaotic system that is readily modified by small changes to the environment, so accurate weather forecasting is currently limited to only a few days. Overall, two things are currently happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.[33]

[edit] Life

Female mallard and ducklings - reproduction is essential for continuing life Main articles: Life and Biosphere Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli and reproduction.[34] Life may also be said to be simply the characteristic state of organisms. Properties common to terrestrial organisms (plants, animals, fungi, protists, archaea and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having a metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made analogs of life may also be considered to be life. The biosphere is the part of Earth's outer shell – including air, land, surface rocks and water – within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air). Currently the entire Earth contains over 75 billion tons (150 trillion pounds or about 6.8 x 1013 kilograms) of biomass (life), which lives within various environments within the biosphere.[35] Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence.[36] More than 2 million species of plant and animal life have been identified to date,[37] and estimates of the actual number of existing species range from several million to well over 50 million.[38][39] [40] The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis.[41][42] The total number of species is presently in rapid decline.[43][44][45]

[edit] Evolution Main article: Evolution Life, as it is currently understood, is only known to exist on the planet Earth. The origin of life is still a poorly understood process, but it is thought to have occurred about 3.9 to 3.5 billion years ago during the hadean or archean eons on a primordial earth that had a substantially different environment than is found at present.[46] These life forms possessed the basic traits of self-replication and inheritable traits. Once life

had appeared, the process of evolution by natural selection resulted in the formation of ever-more diverse life forms. Species that were unable to adapt to the changing environment and competition from other life forms became extinct. However, the fossil record retains evidence of many of these older species. Current fossil and DNA evidence shows that all existing species can trace a continual ancestry back to the first primitive life forms.[46] The advent of photosynthesis in very basic forms of plant life worldwide allowed the sun's energy to be harvested to create conditions allowing for more complex life. The resultant oxygen accumulated in the atmosphere and gave rise to the ozone layer. The incorporation of smaller cells within larger ones resulted in the development of yet more complex cells called eukaryotes.[47] Cells within colonies became increasingly specialized, resulting in true multicellular organisms. With the ozone layer absorbing harmful ultraviolet radiation, life colonized the surface of Earth.

[edit] Microbes Main article: Microbe The first form of life to develop on the Earth were microbes, and they remained the only form of life on the planet until about a billion years ago when multi-cellular organisms began to appear.[48] Microorganisms are single-celled organisms that are generally smaller than the human eye can see. They include Bacteria, Fungi, Archaea and Protista. These life forms are found in almost every location on the Earth where there is liquid water, including the interior of rocks within the planet.[49] Their reproduction is both rapid and profuse. The combination of a high mutation rate and a horizontal gene transfer[50] ability makes them highly adaptable, and able to survive in new environments, including outer space.[51] They form an essential part of the planetary ecosystem. However some microorganisms are pathogenic and can post health risk to other organisms.

[edit] Plants and animals

A confluence of "natural" and a "made" environment. The distinction between plant and animal life is not sharply drawn, with some categories of life that stand between or across the two. Originally Aristotle divided all living things between plants, which generally do not move, and animals. In Linnaeus' system, these became the kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora,[52][53] and some classifications use the term bacterial flora separately from plant flora. Among the many ways of classifying plants are by regional floras, which, depending on the purpose of study, can also include fossil flora, remnants of plant life from a previous era. People in many regions and

countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and terrain. Regional floras commonly are divided into categories such as native flora and agricultural and garden flora, the latter of which are intentionally grown and cultivated. Some types of "native flora" actually have been introduced centuries ago by people migrating from one region or continent to another, and become an integral part of the native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature can blur the boundary of what is considered nature. Another category of plant has historically been carved out for weeds. Though the term has fallen into disfavor among botanists as a formal way to categorize "useless" plants, the informal use of the word "weeds" to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek to alter or shape the course of nature. Similarly, animals are often categorized in ways such as domestic, farm animals, wild animals, pests, etc. according to their relationship to human life.

Wildebeest in Ngorongoro Conservation Area, Tanzania. Note the tendency to congregate, one of nature's displays of what is sometimes called the herding instinct or herd behavior. Animals as a category have several characteristics that generally set them apart from other living things, though not traced by scientists to having legs or wings instead of roots and leaves. Animals are eukaryotic and usually multicellular (although see Myxozoa), which separates them from bacteria, archaea and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. With a few exceptions, most notably the sponges (Phylum Porifera), animals have bodies differentiated into separate tissues. These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestive chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones, and spicules, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility. See also: plants, botany, fauna, animal, and biology

[edit] Ecosystems

Loch Lomond in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained unchanged over a very long period.[54] Main articles: Ecology and Ecosystem All forms of life interact with the environment in which they exist, and also with other life forms. In the 20th century this premise gave rise to the concept of ecosystems, which can be defined as any situation where there is interaction between organisms and their environment. Ecosystems are composed of a variety of abiotic and biotic components that function in an interrelated way.[55] The structure and composition is determined by various environmental factors that are interrelated. Variations of these factors will initiate dynamic modifications to the ecosystem. Some of the more important components are: soil, atmosphere, radiation from the sun, water, and living organisms. Each living organism has a continual relationship with every other element that makes up its environment. Within the ecosystem, species are connected and dependent upon one another in the food chain, and exchange energy and matter between themselves as well as with their environment.[56]

An aerial view of a human ecosystem. Pictured is the city of Chicago Every species has limits of tolerance to factors that affect its survival, reproductive success and ability to continue to thrive and interact sustainably with the rest of its environment, which in turn may have effects on these factors for many other species or even on the whole of life.[57] The concept of an ecosystem is thus an important subject of study, as such study provides information needed to make decisions about how human life may interact in a way that allows the various ecosystems to be sustained for future use rather than used up or otherwise rendered ineffective. For the purpose of such study, a unit of smaller size is called a microecosystem. For example, an ecosystem can be a stone and all the life under it. A macroecosystem might involve a whole ecoregion, with its drainage basin.[58] The following ecosystems are examples of the kinds currently under intensive study: • • •

"continental ecosystems", such as "forest ecosystems", "meadow ecosystems" such as steppes or savannas), or agro-ecosystems, systems in inland waters, such as lentic ecosystem"s such as lakes or ponds; or lotic ecosystems such as rivers, oceanic ecosystems.

Another classification can be made by reference to its communities, such as in the case of a human ecosystem. Regional groupings of distinctive plant and animals best adapted to the region's physical natural environment, latitude, altitude, and terrain are known as biomes. The broadest classification, today under wide study and analysis, and also subject to widespread arguments about its nature and validity, is that of the entire sum of life seen as analogous to a self-sustaining organism; a theory studied as earth system science (less formally known as Gaia theory).[59][60]

[edit] Human interrelationship

Despite their apparent natural beauty, the secluded valleys along the Na Pali Coast in Hawaii are heavily modified by introduced invasive species such as She-oak. Although humans currently comprise only about one-half of one percent of the total living biomass on Earth,[61] the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what we regard as nature and "made environments" is not clear cut except at the extremes. Even at the extremes, the amount of natural environment that is free of discernible human influence is presently diminishing at an increasingly rapid pace, or, according to some, has already disappeared. The development of technology by the human race has allowed the greater exploitation of natural resources and has helped to alleviate some of the risk from natural hazards. In spite of this progress, however, the fate of human civilization remains closely linked to changes in the environment. There exists a highly complex feedback-loop between the use of advanced technology and changes to the environment that are only slowly becoming understood.[62] Manmade threats to the Earth's natural environment include pollution, deforestation, and disasters such as oil spills. Humans have contributed to the extinction of many plants and animals. Humans employ nature for both leisure and economic activities. The acquisition of natural resources for industrial use remains the primary component of the world's economic system. Some activities, such as hunting and fishing, are used for both sustenance and leisure, often by different people. Agriculture was first adopted around the 9th millennium BCE. Ranging from food production to energy, nature influences economic wealth. Although early humans gathered uncultivated plant materials for food and employed the medicinal properties of vegetation for healing,[63] most modern human use of plants is through agriculture. The clearance of large tracts of land for crop growth has led to a significant reduction in the amount available of forestation and wetlands, resulting in the loss of habitat for many plant and animal species as well as increased erosion.[64]

[edit] Wilderness

The Daintree Rainforest, a wilderness area in Queensland, Australia Main articles: Wilderness and Natural environment Wilderness is generally defined as a natural environment on Earth that has not been directly modified by human activity. Ecologists consider wilderness areas to be an integral part of the planet's self-sustaining natural ecosystem (the biosphere). The word, "wilderness", derives from the notion of wildness; in other words that which is not controllable by humans. The word's etymology is from the Old English wildeornes, which in turn derives from wildeor meaning wild beast (wild + deor = beast, deer).[65] From this point of view, it is the wildness of a place that makes it a wilderness. The mere presence or activity of people does not disqualify an area from being "wilderness." Many ecosystems that are, or have been, inhabited or influenced by activities of people may still be considered "wild." This way of looking at wilderness includes areas within which natural processes operate without very noticeable human interference.

[edit] Beauty in nature

Salmon fry hatching. The root of the Latin "natura" {"nature") is "natus," from "nasci" ("to be born").[66]

Painting by Song Dynasty artist Fan Kuan (c. 970–1020) Beauty in nature has long been a common theme in life and in art, and books emphasizing beauty in nature fill large sections of libraries and bookstores. That nature has been depicted and celebrated by so much art, photography, poetry and other literature shows the strength with which many people associate

nature and beauty. Why this association exists, and what the association consists of, is studied by the branch of philosophy called aesthetics. Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless.[67] Looked at through the lens of the visual arts, nature and wildness have been important subjects in various epochs of world history. An early tradition of landscape art began in China during the Tang Dynasty (618-907). The tradition of representing nature as it is became one of the aims of Chinese painting and was a significant influence in Asian art. Artists learned to depict mountains and rivers "from the perspective of nature as a whole and on the basis of their understanding of the laws of nature ... as if seen through the eyes of a bird." In the 13th century, the Song Dynasty artist Shi Erji listed "scenes lacking any places made inaccessible by nature," as one of the 12 things to avoid in painting.[68] In the Western world the idea of wilderness having intrinsic value emerged in the 1800s, especially in the works of the Romantic movement. British artists John Constable and JMW Turner turned their attention to capturing the beauty of the natural world in their paintings. Before that, paintings had been primarily of religious scenes or of human beings. William Wordsworth’s poetry described the wonder of the natural world, which had formerly been viewed as a threatening place. Increasingly the valuing of nature became an aspect of Western culture.[69] This artistic movement also coincided with the Transcendentalist movement in the Western world. Many scientists, who study nature in more specific and organized ways, also share the conviction that nature is beautiful; the French mathematician, Jules Henri Poincaré (1854–1912) said: The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, and if nature were not worth knowing, life would not be worth living. Of course I do not here speak of that beauty which strikes the senses, the beauty of qualities and of appearance; not that I undervalue such beauty, far from it, but it has nothing to do with science; I mean that profounder beauty which comes from the harmonious order of the parts and which a pure intelligence can grasp.[70]

A common classical idea of beautiful art involves the word mimesis, the imitation of nature. Also in the realm of ideas about beauty in nature is that the perfect is implied through symmetry, equal division, and other perfect mathematical forms and notions.

[edit] Matter and energy Main articles: Matter and Energy The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density Some fields of science see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "physics" – the name for which is still recognizable as meaning that it is the study of nature. Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe. The visible components of the universe are now believed to compose only 4 percent of the total mass. The remainder is believed to consist of 23 percent cold dark matter and 73 percent dark energy.[71] The exact nature of these components is still unknown and is currently under intensive investigation by physicists.

The behavior of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants[72] that appear to be static across the observable universe.[73] The values of these constants have been carefully measured, but the reason for their specific values remains a mystery. See also: Chemistry and Physics

[edit] Nature beyond Earth

NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant.

The deepest visible-light image of the universe, the Hubble Ultra Deep Field, contains an estimated 10,000 galaxies in a patch of sky just one-tenth the diameter of the full moon. Image Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF team. Main articles: Outer space and Universe Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between the Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the solar system is called interplanetary space, which passes over into interstellar space at what is known as the heliopause. Outer space is certainly spacious, but it is far from empty. Outer space is sparsely filled with several dozen types of organic molecules discovered to date by microwave spectroscopy, blackbody radiation left over from the big bang and the origin of the universe, and cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is also some gas, plasma and dust, and small meteors. Additionally, there are signs of human life in outer space today, such as material left over from previous manned and unmanned launches which are a potential hazard to spacecraft. Some of this debris re-enters the atmosphere periodically.

Although the planet Earth is currently the only known body within the solar system to support life, current evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface. [74] For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.[75] Conditions on the other terrestrial planets, Mercury and Venus, appear to be too harsh to support life as we know it. But it has been conjectured that Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life.[76] Recently, the team of Stéphane Udry have discovered a new planet named Gliese 581 c, which is an extrasolar planet orbiting the red dwarf star Gliese 581. Gliese 581 c appears to lie in the habitable zone of space surrounding the star, and therefore could possibly host life as we know it. See also: Extraterrestrial life

[edit] See also Science: • • •

Natural history Natural philosophy Natural science

Philosophy: • • •

•

Nature (philosophy) Mother Nature Naturalism (philosophy): any of several philosophical stances, typically those descended from Materialism and Pragmatism that do not distinguish the supernatural from nature. This includes the methodological naturalism of natural science, which makes the methodological assumption that observable events in nature are explained only by natural causes, without assuming either the existence or non-existence of the supernatural. Balance of nature: A discredited concept of natural equilibrium in predator:prey dynamics.

Media: • • • •

Nature, by Ralph Waldo Emerson Nature, a prominent scientific journal Natural History, by Pliny the Elder Nature (TV series)

Organizations: • •

The Nature Conservancy Nature Detectives

[edit] Notes and references

Politics This article is part of the Politics series

Politics •

List of politics topics

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Consent of the governed

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Politics by country

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Politics by subdivision

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Political economy

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Political history

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Political philosophy

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Political science

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International relations (theory)

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Political scientists

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Comparative politics

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Public administration Bureaucracy (street-level)

From Wikipedia, the free encyclopedia

(Redirected from Political) Jump to: navigation, search For other uses, see Politics (disambiguation). "Politic" redirects here. For the political magazine, see The Politic. Politics is the process by which groups of people make decisions. The term is generally applied to behavior within civil governments, but politics has been observed in all human group interactions, including corporate, academic, and religious institutions. It consists of "social relations involving authority or power"[1] and refers to the regulation of a political unit,[2] and to the methods and tactics used to formulate and apply policy.[3] Political science (also political studies) is the study of political behavior, and examines the acquisition and application of power. Related areas of study include political philosophy, which seeks a rationale for politics and an ethic of public behavior, and public administration, which examines the practices of governance.

Contents • Separation of powers [hide] •

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Legislature Executive 1 Source of Power Judiciary o 1.1 Pragmatic view of power o 1.2 Authority and legitimacy • Sovereignty  1.2.1 Traditional authority  1.2.2 Charismatic authority 1.2.3 Legal-rational authority • Theoriesof political behavior o 1.3 Sovereignty

2 Political philosophies Subseries o 2.1 Confucius • Elections o 2.2 Plato o 2.3 Aristotle Electoral systems Machiavelli o 2.4 Niccolò Voting o 2.5 More Extreme Forms o 2.6 Thomas Hobbes o 2.7 John Locke • Federalism o 2.8ofJean-Jacques • Forms government Rousseau o 2.9 John Stuart Mill • Ideology o 2.10 Karl Marx • Political campaigning o 2.11 Ayn Rand o 2.12 Austrian school •3 Political Politicalspectra parties o 3.1 Left-Right politics Politics portal v•d•e

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o 3.2 Authoritarian-Libertarian 4 Philosophical Constructs o 4.1 Normative faces of power debate o 4.2 Postmodern challenge of normative views of power 5 See also o 5.1 Lists o 5.2 Related topics

6 References

[edit] Source of Power [edit] Pragmatic view of power Samuel Gompers' maxim, often paraphrased as,"Reward your friends and punish your enemies,"[4] hints at two of the five types of power recognized by social psychologists: incentive power (the power to reward) and coercive power (the power to punish). Arguably the other three grow out of these two: Legitimate power, the power of the policeman or the referee, is the power given to an individual by a recognized authority to enforce standards of behavior. Legitimate power is similar to coercive power in that unacceptable behavior is punished by fine or penalty. Referent power is bestowed upon individuals by virtue of accomplishment or attitude. Fulfillment of the desire to feel similar to a celebrity or a hero is the reward for obedience. This is an example of incentive power as one rewards oneself. Expert power springs from education or experience. Following the lead of an expert is often rewarded with success. Note that expert power is conditional to circumstances (for example, if leaky pipes need to be repaired, a brain surgeon's advice probably would not carry as much weight as a plumber's).

[edit] Authority and legitimacy Main article: Tripartite classification of authority Authority, in a political sense, is different from political power in that it implies legitimacy and acceptance; it implies that the person or state exercising power has a perceived right to do so (ex: Mr. Hentze).[5] Legitimacy is an attribute of government gained through the acquisition and application of power in accordance with recognized or accepted standards or principles. Max Weber identified three sources of legitimacy for authority, known as the tripartite classification of authority.[6] He proposed three reasons why people follow the orders of those who give them: [edit] Traditional authority Traditional authorities receive loyalty because they continue and support the preservation of existing values, the status quo. Weber called this "the authority of the eternal yesterday".[6]Patriarchal (and more rarely matriarchal) societies gave rise to hereditary monarchies where authority was given to descendants of previous leaders. Followers submit to this authority because "we've always done it that way." Examples of traditional authoritarians include absolute monarchs.

[edit] Charismatic authority Charismatic authority grows out of the personal charm or the strength of an individual personality (see cult of personality for the most extreme version). Charismatic regimes are often short-lived, seldom outliving the charismatic figure that leads them. For a charismatic regime to survive the rule of the individual personality, it must transform its legitimacy into a different form of authority. An example of this would be Augustus' efforts to create the position of the Roman principate and establish a ruling dynasty, which could be viewed as a shift to a traditional form of authority, in the form of the principate that would exist in Rome for more than 400 years after his death. [edit] Legal-rational authority Legal-rational authorities receive their ability to compel behavior by virtue of the office that they hold. It is the authority that demands obedience to the office rather than the office holder; Weber identified "rationally-created rules"[6] as the central feature of this form of authority. Modern democracies are examples of legal-rational regimes. People also abide by legal-rational authority because it makes sense to do so for their own good, as well as for the greater good of society.[citation needed]

[edit] Sovereignty Main article: Sovereignty Sovereignty is the ability of a government to exert control over its sphere of influence free from outside interference.

[edit] Political philosophies Main article: Political philosophy

[edit] Confucius The Chinese philosopher Confucius (551-471 BCE) was one of the first thinkers to adopt a distinct approach to political philosophy. His philosophy was "rooted in his belief that a ruler should learn selfdiscipline, should govern his subjects by his own example, and should treat them with love and concern."[7] His political beliefs were strongly linked to personal ethics and morality, believing that only a morally upright ruler who possessed "de", or virtue, should be able to exercise power, and that the behavior of an individual ought to be consistent with their rank in society. He stated that "Good government consists in the ruler being a ruler, the minister being a minister, the father being a father, and the son being a son."[8]

[edit] Plato The Greek philosopher Plato(428-348 BC), in his book The Republic, argued that all conventional political systems (democracy, monarchy, oligarchy and timarchy) were inherently corrupt, and that the state ought to be governed by an elite class of educated philosopher-rulers, who would be trained from birth and selected on the basis of aptitude: "those who have the greatest skill in watching over the community."[9] This has been characterised as authoritarian and elitist by some later scholars, notably Karl Popper in his book The Open Society and its Enemies, who described Plato's schemes as essentially totalitarian and criticised his apparent advocacy of censorship.[10] The Republic has also been labeled as communist, due to its advocacy of abolishing private property and the family among the ruling classes; however, this view has been discounted by many scholars, as there are implications in the text that this

will extend only to the ruling classes, and that ordinary citizens "will have enough private property to make the regulation of wealth and poverty a concern.."[11]

[edit] Aristotle

Aristotle In his book Politics, the Greek philosopher Aristotle(384–322BC) asserted that man is, by nature, a political animal. He argued that ethics and politics are closely linked, and that a truly ethical life can only be lived by someone who participates in politics.[12] Like Plato, Aristotle identified a number of different forms of government, and argued that each "correct" form of government may devolve into a "deviant" form of government, in which its institutions were corrupted. According to Aristotle, kingship, with one ruler, devolves into tyranny; aristocracy, with a small group of rulers, devolves into oligarchy; and polity, with collective rule by many citizens, devolves into democracy.[13] In this sense, Aristotle does not use the word "democracy" in its modern sense, carrying positive connotations, but in its literal sense of rule by the demos, or common people.[13] A more accurate view of Aristotle denouncing democracy was that it was described as mob rule, or ochlocracy.

[edit] Niccolò Machiavelli From the name of the Renaissance thinker Niccolò Machiavelli has been derived the term "Machiavellian," referring to an amoral person who employs subterfuge, along with brutal and manipulative methods to attain and retain power.

[edit] More Extreme Forms Machiavelli's works have been studied and his theories practiced in categorically more extreme forms by totalitarians such as Benito Mussolini, Adolf Hitler, many of whom used chaos and brutality for purposes of state security.[14] However, many scholars have questioned this view of Machiavelli's theory, arguing that "Machiavelli did not invent 'Machiavellianism' and may not even have been a 'Machiavellian' in the sense often ascribed to him."[15] Instead, Machiavelli considered the stability of the state to be the most important goal, and argued that qualities traditionally considered morally desirable, such as generosity, were undesirable in a ruler and would lead to the loss of power.

[edit] Thomas Hobbes

In 1651, Thomas Hobbes published his most famous work, Leviathan, in which he proposed a model of early human development to justify the creation of polities, i.e. governed bodies. Hobbes described an ideal state of nature wherein every person had equal right to every resource in nature and was free to use any means to acquire those resources. He claimed that such an arrangement created a “war of all against all” (bellum omnium contra omnes). The book has been interpreted by scholars as posing two "stark alternatives"; total obedience to an absolute ruler, or "a state of nature, which closely resembles civil war...where all have reason to fear a violent death".[16] Hobbes' view can therefore be interpreted as a defense of absolutism, arguing that human beings enter into a social contract for their protection and agree to obey the dictates of the sovereign; in Hobbes' worldview, "the sovereign is nothing more than the personal embodiment of orderly government."[17] Hobbes himself argued "The final cause, end, or design of men (who naturally love liberty, and dominion over others) in the introduction of that restraint upon themselves, in which we see them live in Commonwealths, is the foresight of their own preservation, and of a more contented life thereby."[18]

[edit] John Locke Main article: John Locke In the Two Treatise of Government, Locke refutes the theory of the Divine Right of Kings as put forward by Robert Filmer; he "minutely examines key Biblical passages"[19] and concludes that absolute monarchy is not supported by Christian theology. "Locke singles out Filmer's contention that men are not 'naturally free' as the key issue, for that is the 'ground'...on which Filmer erects his argument for the claim that all 'legitimate' government is 'absolute monarchy'."[19] In the Second Treatise of Government, Locke examines the concept of the social contract put forward by other theorists such as Thomas Hobbes, but reaches a different conclusion. Although he agreed with Hobbes on the concept of a state of nature before existing forms of government arose, he challenged Hobbes' view that the state of nature was equivalent to a state of war, instead arguing that there were certain natural rights belonging to all human beings, which continued even after a political authority was established. "The state of nature has a law of nature to govern it, which obliges everyone...being all equal and independent, no one ought to harm another in his life, liberty, health or possessions".[20] According to one scholar, the basis of Locke's thought in the Second Treatise is that "contract or consent is the ground of government and fixes its limits...behind [this] doctrine lies the idea of the independence of the individual person."[21] In other words, Locke's view was different from Hobbes' in that he interpreted the idea of the "state of nature" differently, and he argued that people's natural rights were not necessarily eliminated by their consent to be governed by a political authority.

[edit] Jean-Jacques Rousseau The 18th century French philosopher Jean-Jacques Rousseau, in his book The Social Contract, put forward a system of political thought which was closely related to those of Hobbes and Locke, but different in important respects. In the opening sentence of the book, Rousseau argued that "...man was born free, but he is everywhere in chains"[22] He defined political authority and legitimacy as stemming from the "general will", or volonté generale; for Rousseau, "true Sovereignty is directed always at the public good".[23] This concept of the general will implicitly "allows for individual diversity and freedom... [but] also encourages the well-being of the whole, and therefore can conflict with the particular interests of individuals."[23] As such, Rousseau also argues that the people may need a "lawgiver" to draw up a constitution and system of laws, because the general will, "while always morally sound, is sometimes mistaken".[22]

Rousseau's thought has been seen by some scholars as contradictory and inconsistent, and as not addressing the fundamental contradiction between individual freedom and subordination to the needs of society, "the tension that seems to exist between liberalism and communitarianism".[23] As one Catholic scholar argues, "that it [The Social Contract] contains serious contradictions is undeniable...its fundamental principles--the origin of society, absolute freedom and absolute equality of all--are false and unnatural."[24] The Catholic Encyclopedia further argues that Rousseau's concept of the general will would inevitably lead to "the suppression of personality, the reign of force and caprice, the tyranny of the multitude, the despotism of the crowd", i.e. the subordination of the individual to society as a whole.[24]

John Stuart Mill

[edit] John Stuart Mill In the 19th century, John Stuart Mill pioneered the liberal conception of politics. He saw democracy as the major political development of his era[25] and, in his book On Liberty, advocated stronger protection for individual rights against government and the rule of the majority. He argued that liberty was the most important right of human beings, and that the only just cause for interfering with the liberty of another person was self-protection.[26] One commentator refers to On Liberty as "the strongest and most eloquent defense of liberalism that we have."[26] Mill also emphasised the importance of freedom of speech, claiming that "we can never be sure that the opinion we are attempting to stifle is a false opinion, and if we were sure, stifling it would be an evil still."[27]

[edit] Karl Marx Marx's theories, collectively termed Marxism, were critical of capitalism and argued that in the due course of history, there would be an "inevitable breakdown of capitalism for economic reasons, to be replaced by communism."[28] He defined history in terms of the class struggle between the bourgeoisie, or propertyowning classes, and the proletariat, or workers, a struggle intensified by industrialization: "The development of Modern Industry, therefore, cuts from under its feet the very foundation on which the bourgeoisie produces and appropriates products. What the bourgeoisie therefore produces, above all, are its own grave-diggers. Its fall and the victory of the proletariat are equally inevitable.[29] Utopia for Marx was the classless society in which the state and the church would be very weak or nonexistent. The workers ultimately would own the means of production, state ownership would be a mere transition period, therefore the people would be free. Because the state as Marx knew it would practically disappear over time, there would be no need for borders so individuals would be free to move from nation to nation without prosecution. This latter idea of internationalism is the direct opposition to the Nazi utopia of the Master race and national socialism. Although Marxism is mostly associated with the Soviet Union for obvious reasons, one may also see in the European Union many but not all of Marx's ideas such as universal health care, open border and the free movement of people, and less economic inequality.

Many subsequent political movements have based themselves on Marx's thought, offering widely differing interpretations of communism; these include Marxism-Leninism and libertarian Marxism. Possibly the most influential interpreter of Marxist theory was Lenin, founder of the Soviet Union, who created a revolutionary theory founded on Marxist thinking. However, libertarian Marxist thinkers have challenged Lenin's interpretation of Marx; Cornelius Castoriadis, for instance, described the Soviet Union's system as a form of "bureaucratic capitalism" rather than true communism.[30] The multiple notions of political power that are put forth range from conventional views that simply revolve around the actions of politicians to those who view political power as an insidious form of institutionalized social control - most notably "anarchists" and "radical capitalists". The main views of political power revolve around normative, post-modern, and pragmatic perspectives.

[edit] Ayn Rand Objectivism is a philosophy[31][32] developed by Ayn Rand in the 20th century. It's associated with rightwing politics. Objectivism holds that reality exists independent from consciousness; that individual persons are in contact with this reality through sensory perception; that human beings can gain objective knowledge from perception through the process of concept formation; that the proper moral purpose of one's life is the pursuit of one's own happiness through acting in one's "rational self-interest"; that the only social system consistent with this morality is full respect for individual rights, embodied in pure, consensual laissez-faire capitalism; and that the role of art in human life is to transform man's widest metaphysical ideas, by selective reproduction of reality, into a physical form—a work of art—that one can comprehend and respond to.

[edit] Austrian school The Austrian School, also known as the “Vienna School” or the “Psychological School”, is a heterodox[33] school of economics that advocates adherence to strict methodological individualism. Proponents of the Austrian School hold that the only valid economic theory is logically derived from basic principles of human action. Alongside the formal approach to theory, often called praxeology, the school has traditionally advocated an interpretive approach to history. Proponents of praxeological method hold that it allows for the discovery of economic laws valid for all human action, while the interpretive approach addresses specific historical events. Critics of the Austrian school contend that its methods consist of post-hoc analysis, do not generate testable implications and, so, fail falsifiability.[34][35]

[edit] Political spectra [edit] Left-Right politics Main article: Left-Right politics Most political analysts and politicians divide politics into left wing and right wing politics, often also using the idea of center politics as a middle path of policy between the right and left. This classification is comparatively recent (it was not used by Aristotle or Hobbes, for instance), and dates from the French Revolution era, when those members of the National Assembly who opposed the monarchy sat on the left, while those who supported it sat on the right.[36] The original meaning disappeared quickly. A particularly influential event was the publication of the Communist Manifesto by Karl Marx and Frederick Engels in 1848. The Manifesto suggested a course of action for a proletarian revolution to overthrow the bourgeois society and abolish private property, in the belief that this would lead to a classless and stateless society. The left would refer to people seeking socialist state or communist state.

The meaning of left-wing and right-wing varies considerably between different countries and at different times, but generally speaking, it can be said that the right wing often values tradition and free markets while the left wing often values equalitarianism. According to Norberto Bobbio, one of the major exponents of this distinction, the Left believes in attempting to eradicate social inequality, while the Right regards most social inequality as the result of ineradicable natural inequalities, and sees attempts to enforce social equality as utopian or authoritarian.[37] Some ideologies, notably Christian Democracy, claim to combine left and right wing politics; according to Geoffrey K. Roberts and Patricia Hogwood, "In terms of ideology, Christian Democracy has incorporated many of the views held by liberals, conservatives and socialists within a wider framework of moral and Christian principles."[38] Movements which claim or formerly claimed to be above the left-right divide include Gaullism in France, Peronism in Argentina, and National Action Politics in Mexico.

[edit] Authoritarian-Libertarian Authoritarianism and libertarianism refer to the amount of individual freedom each person possesses in that society relative to the state. One author describes authoritarian political systems as those where "individual rights and goals are subjugated to group goals, expectations and conformities",[39] while a libertarian political system is one in which individual rights and civil liberties are paramount. More extreme than libertarians are anarchists, who argue for the total abolition of government, while the most extreme authoritarians are totalitarians who support state control over all aspects of society. For instance, classical liberalism (also known as laissez-faire liberalism[40], or, in much of the world, simply liberalism) is a doctrine stressing individual freedom and limited government. This includes the importance of human rationality, individual property rights, free markets, natural rights, the protection of civil liberties, constitutional limitation of government, and individual freedom from restraint as exemplified in the writings of John Locke, Adam Smith, David Hume, David Ricardo, Voltaire, Montesquieu and others. According to the libertarian Institute for Humane Studies, "the libertarian, or 'classical liberal,' perspective is that individual well-being, prosperity, and social harmony are fostered by 'as much liberty as possible' and 'as little government as necessary.'"[41]

[edit] Philosophical Constructs [edit] Normative faces of power debate The faces of power debate has coalesced into a viable conception of three dimensions of power including decision-making, agenda-setting, and preference-shaping. The decision-making dimension was first put forth by Robert Dahl, who advocated the notion that political power is based in the formal political arena and is measured through voting patterns and the decisions made by politicians.[42] This view has been criticised by many as simplistic, notably by the sociologist G. William Domhoff,[43] who argues that political and economic power is monopolised by the "elite classes". A second dimension to the notion of political power was added by academics Peter Bachrach and Morton Baratz involving "agenda-setting". Bachrach and Baratz viewed power as involving both the formal political arena and behind the scenes agenda-setting by elite groups who could be either politicians and/or others (such as industrialists, campaign contributors, special interest groups and so on), often with a hidden agenda that most of the public may not be aware of. The third dimension of power was added by British academic Steven Lukes who felt that even with this second dimension, some other traits of political power needed to be addressed through the concept of 'preference-shaping'. Lukes developed the

concept of the "Three faces of power" - decision-making power, non-decision-making power, and ideological power.[44] This third dimension is inspired by many Neo-Gramscian views such as cultural hegemony and deals with how civil society and the general public have their preferences shaped for them by those in power through the use of propaganda or the media. Ultimately, this third dimension holds that the general public may not be aware of what decisions are actually in their interest due to the invisible power of elites who work to distort their perceptions. Critics of this view claim that such notions are themselves elitist, which Lukes then clearly admits as one problem of this view and yet clarifies that as long as those who make claims that preferences are being shaped explain their own interests etc., there is room for more transparency.

[edit] Postmodern challenge of normative views of power Some within the postmodern and post-structuralist field claim that power is something that is not in the hands of the few and is rather dispersed throughout society in various ways. As one academic writes, "...postmodernists have argued that due to a variety of inherent biases in the standards by which ”valid“ knowledge has been evaluated...modernist science has tended to reproduce ideological justifications for the perpetuation of long-standing forms of inequality. Thus, it is the strategy of postmodern science...to identify and, thereby, attack the ”deceiving“ power of universalizing scientific epistemologies."[45]

[edit] See also Politics portal

Find more about Politics on Wikipedia's sister projects: Dictionary definitions Textbooks Quotations Source texts Images and media News stories Learning resources

[edit] Lists • • •

List of basic political topics List of politics by country articles List of years in politics

[edit] Related topics •

Food politics

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Government simulation game Music and politics Official statistics Political activism Political compass Political corruption Political criticism Political economy Political fiction Political game Political labels Political movement Political parties of the world Political party Political philosophy Political psychology Political science Political simulation Political sociology Political spectrum Politics in fiction Strategic planning

[edit] References

Childhood From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the phase of human development known as childhood. For the Michael Jackson song, see Childhood (song). For the episode of Robin Hood, see Childhood (Robin Hood episode). It has been suggested that Childhood and migration be merged into this article or section. (Discuss)

It has been suggested that this article or section be merged with Child development. (Discuss) The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

Childhood (being a child) is a broad term usually applied to the phase of development in humans between infancy and adulthood.

Contents [hide] • • • • • •

1 Age definition of a child 2 Research in social sciences 3 Background and History 4 See also 5 Footnotes 6 Further reading

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7 External links

[edit] Age definition of a child In many countries there is an age of majority when childhood ends and a person legally becomes an adult. The age can range anywhere from 12 to 21, with 18 being the most common.

[edit] Research in social sciences In recent years there has been a rapid growth of interest in the sociological study of childhood. Reaching on a large body of contemporary sociological and anthropological research, people have developed key links between the study of childhood and social theory, exploring its historical, political, and cultural dimensions. in ethiopia

[edit] Background and History

Playing Children, by Song Dynasty Chinese artist Su Hanchen, c. 1150 AD. Philippe Ariès, an important French medievalist and historian, published a study in 1961 of paintings, gravestones, furniture, and school records. He found that before the seventeenth century, children were represented as mini-adults. Since then historians have increasingly researched childhood in past times. Before Ariès, George Boas had published The Cult of Childhood. Several historical events and periods are discussed as relevant to the history of childhood in the West. One such event is the life of Jesus Christ[1] Christ taught that children were to be loved and revered, a departure from the ancients' attitude to children which was to be propagated in the Roman Empire during the next 400 years with the introduction of Christianity.[citation needed] During the Renaissance, artistic depictions of children increased dramatically in Europe. This did not impact the social attitude to children much, however -- see the article on child labour. The Victorian Era has been described as a source of the modern institution of childhood. Ironically, the Industrial Revolution during this era led to an increase in child labour, but due to the campaigning of the Evangelicals, and efforts of author Charles Dickens and others, child labour was gradually reduced and halted in England via the Factory Acts of 1802-1878. The Victorians concomitantly emphasized the role of the family and the sanctity of the child, and broadly speaking, this attitude has remained dominant in Western societies since then. In the contemporary era Joe L. Kincheloe and Shirley R. Steinberg have constructed a critical theory of childhood and childhood education that they have labeled kinderculture. Here Kincheloe and Steinberg make use of multiple research and theoretical discourses (the bricolage) to study childhood from diverse perspectives—historiography, ethnography, cognitive research, media studies, cultural studies, political economic analysis, hermeneutics, semiotics, content analysis, etc. Based on this multiperspectival inquiry, Kincheloe and Steinberg contend that new times have ushered in a new era of childhood. Evidence of this dramatic cultural change is omnipresent, but many individuals in the late twentieth and early twenty-first centuries have not yet noticed it. When Steinberg and Kincheloe wrote the first edition of Kinderculture:

The Corporate Construction of Childhood in 1997 (second edition, 2004) many people who made their living studying, teaching, or caring for children were not yet aware of the nature of the changes in childhood that they encountered daily. In the domains of psychology, education, and to a lesser degree sociology and cultural studies few observers before kinderculture had studied the ways that the information explosion so characteristic of our contemporary era (hyperreality) had operated to undermine traditional notions of childhood and change the terrain of childhood education. Those who have shaped, directed and employed contemporary information technology have played an exaggerated role in the reformulation of childhood. Of course, information technology alone, Kincheloe and Steinberg maintain, has not produced a new era of childhood. Obviously, numerous social, cultural, and political economic factors have operated to produce such changes. The central purpose of kinderculture is to socially, culturally, politically, and economically situate the changing historical status of childhood and to specifically interroge the ways diverse media have helped construct what Kincheloe and Steinberg call "the new childhood." Kinderculture understands that childhood is an ever-changing social and historical artifact—not simply a biological entity. Because many psychologists have argued that childhood is a natural phase of growing up, of becoming an adult, Kincheloe and Steinberg coming from an educational context saw kinderculture as a corrective to such a "psychologization" of childhood.

[edit] See also • • •

List of child related articles Childhood and migration Early childhood

[edit] Footnotes 1. ^ Wilde, Oscar. De profundis. Dover Publications New York, 1996.

[edit] Further reading

Adult

From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the human developmental stage. For the adult insect stage, see Imago. For the band, see ADULT.. For the 2008 British film by Noel Clarke see Adulthood (film). The term adult has three distinct meanings. It indicates a grown person. It may also mean a plant or animal that has reached full growth, or one who is legally of age; as opposed to a minor. Adulthood can be defined in biology, psychological adult development, law, personal character, or social status. These different aspects of adulthood are often inconsistent and contradictory. A person may be biologically an adult, and have adult behavioral but still be treated as a child if they are under the legal age of majority. Conversely one may legally be an adult but possess none of the maturity and responsibility that define adult character. Coming of age is the event; passing a series of tests to demonstrate the child is prepared for adulthood; or reaching a specified age, sometimes in conjunction with demonstrating preparation. Most modern societies determine legal adulthood based on reaching a legally-specified age without requiring a demonstration of physical maturity or preparation for adulthood. Adult, especially in the sense of entertainment or other diversion, frequently appears as a euphemism for being related to sexual behaviour. Adult toys and adult games—which terms refer to games and toys that are closely related to sex, do not generally refer only to games or toys with which children are simply incompatible—are in this category, for example. This usage does indicate unsuitability for children, but the more immediate meaning is closer to "not legal for children." Adult education, however, does simply mean education for adults, especially for those past the usual age for either high school or university. Some propose that moving into adulthood involves an emotional structuring of denial. This process becomes necessary to cope with one's own behavior, especially in uncomfortable situations, and also the behavior of others.

Contents [hide] • • • • •

1 Biological adulthood 2 Legal adulthood 3 Personal characteristics 4 See also 5 References

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6 External links

[edit] Biological adulthood Adulthood is generally understood as the time when physical maturation is complete. This usually occurs anywhere between 19 and 21. They reach their maximum height and secondary sex characteristics in the form of body hair and maturing of the larynx, as well as ovulating monthly for women. Natural sleep patterns change in adulthood, as adults typically require less sleep than during adolescence and childhood.

At this point, such individuals usually become independent and therefore able to care for others as well as themselves. There are exceptions to this rule however.

[edit] Legal adulthood Main article: Age of majority Legally it means that one can engage in a contract. The same or a different minimum age may be applicable to, for example, parents losing parenting rights and duties regarding the person concerned, parents losing financial responsibility, marriage, voting, having a job, being a soldier, buying/possessing firearms (if legal at all), driving, traveling abroad, involvement with alcoholic beverages (if legal at all), smoking, sex, gambling (both lottery and casino) being a prostitute or a client of a prostitute (if legal at all), being a model or actor in pornography, etc. Admission of a young person to a place may be restricted because of danger for that person, and/or because of the risk that the young person causes damage (for example, at an exhibition of fragile items). One can distinguish the legality of acts of a young person, and of enabling a young person to carry out that act, by selling, renting out, showing, permitting entrance, participating, etc. There may be distinction between commercially and socially enabling. Sometimes there is the requirement of supervision by a legal guardian, or just by an adult. Sometimes there is no requirement, but just a recommendation. With regard to pornography one can distinguish: • • • • •

being allowed inside an adult establishment being allowed to purchase pornography being allowed to possess pornography another person being allowed to sell, rent out, or show the young person pornography, see disseminating pornography to a minor being a model or actor in pornography: rules for the young person, and for other people, regarding production, possession, etc. (see child pornography)

With regard to films with violence, etc.: •

another person being allowed to sell, rent out, or show the young person the film, a cinema being allowed to let the young person (under 17) enter

The legal definition of entering adulthood usually varies between ages 15–21, depending on the region in question. Some cultures in Africa define adult at age 13. According to Jewish tradition, adulthood is reached at age 13 (the age of the Bar Mitzvah), for Jewish boys, for example, were expected to demonstrate preparation for adulthood by learning the Torah and other Jewish practices. The Christian Bible and Jewish scripture has no age requirement for adulthood or marrying, which includes engaging in sexual activity. According to The Disappearance of Childhood by Neil Postman, the Christian Church of the Middle Ages considered the age of accountability, when a person could be tried and even executed as an adult, to be age 7 . In most of the world, including the United States, parts of the United Kingdom (England, Northern Ireland, Wales), India and China, the legal adult age is 18, with some exceptions: 1. Iran and Singapore (21) 2. Indonesia and Japan (20)

3. South Korea & British Columbia, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Nunavut, Yukon Territory in Canada (19) 4. the United Kingdom: Scotland (16)

[edit] Personal characteristics There are some qualities that symbolize adultness in most cultures. There is not always a correlation between the qualities and the physical age of the person. The adult character comprises: Self-control - restraint, emotional control. Stability - stable personality, strength. Independence - ability to self-regulate. Seriousness - ability to deal with life in a serious manner. Responsibility - accountability, commitment and reliability. Method/Tact - ability to think ahead and plan for the future, patience. Endurance - ability and willingness to cope with difficulties that present themselves. Experience - breadth of mind, understanding. Objectivity - perspective and realism. Decision making capability - as all of the above correspond to making proper decisions. Priorities - Ability to determine what is necessary at that place and time.

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[edit] See also Adolescence Adult development Child Watershed (television) Age of consent Manhood Womanhood Motion picture rating system Adultism

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[edit] References [edit] External links Table 8. Age of Independence US and UK legal age guide.

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It does not cite any references or sources. Please help improve it by citing reliable sources. Tagged since December 2007.

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Warfare

[hide] v•d•e

Human development: biological - psychological - Overview table Military history

Pre- and Prenatal development • Pre- and perinatal psychology Eras[show] perinatal Prehistoric Ancient Infant and child development (stages) • Infancy Infancy Medieval GunpowderChild development (stages) Childhood IndustrialToddlerhood • Preadolescence Modern Battlespace Adolescence[show] Youth development • Puberty Air InformationEarly adulthood • Middle adulthood • Late adulthood • Ageing & Senescence Adulthood Land Sea Theorists-theories John Bowlby-attachment • Urie Bronfenbrenner-ecological systems • Erik Space Erikson-psychosocial • Sigmund Freud-psychosexual • Lawrence KohlbergWeapons[show] moral • Jean Piaget-cognitive • Lev Vygotsky-cultural-historical Armor Retrieved from "http://en.wikipedia.org/wiki/Adult" Artillery Categories: Biology | Human development Biological Hidden categories: Articles lacking sources from December 2007 | Cavalry All articles lacking sources | Cleanup from October 2007 | All pages Chemical needing cleanup | Articles that may contain original research since Electronic October 2007 Infantry Nuclear Psychological Tactics[show] Attrition From Wikipedia, the free encyclopedia Guerilla Maneuver Jump to: navigation, search Siege This article needs additional citations for verification. Please help improve this article by adding Total war reliable references. Unsourced material may be challenged and removed. (August 2007) Trench For other uses, see Weapon (disambiguation). See military Strategy[show] technology and equipment for a comprehensive list of weapons and Economic doctrines. Grand Operational A weapon is a tool used to apply or threaten to apply force for the Organization[show] purpose of hunting, attack or defense in combat, subduing enemy Formations personnel, or to destroy enemy weapons, equipment and defensive Ranks structures. A weapon is therefore a device that changes the direction Units or magnitude of a force.[1] In general, they can be defined as the Logistics[show] simplest mechanisms that use mechanical advantage (also called Equipment leverage) to multiply force.[2] Material Supply line In attack, weapons may be used to threaten by direct contact or by Lists[show] use of projectiles. Weapons can be as simple as a club, or as Battles complex as an intercontinental ballistic missile. Metaphorically Commanders speaking, anything capable of causing damage, even Operations psychologically, can be referred to as a weapon. More recently, Sieges Theorists Wars

Weapon

non-lethal weapons have been developed for para-military, security and even combat use, designed to incapacitate personnel and reduce collateral damage to property and environment.[3]

Contents [hide]

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1 History o 1.1 Prehistoric weapons o 1.2 Ancient world weapons o 1.3 Weapons of the Middle Ages o 1.4 Early modern period weapons o 1.5 Modern weapons o 1.6 Weapon development since the Second World War 2 Classification of weapons 3 See also 4 Citations and notes 5 References

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6 External links

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[edit] History [edit] Prehistoric weapons

An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools. Very simple weapon use has been seen in some communities of chimpanzees.[4] Craig Stanford, a primatologist and professor of anthropology at the University of Southern California, has suggested that the discovery of spear use by chimpanzees probably means that early humans used wooden spears as well, perhaps five million years ago.[5] The earliest and most primitive weapons were the by-products of early human hunting – claws, teeth and horns of hunted animals, shaped or adapted for use as weapons. Stone axes were used as weapons very early in human history as personal weapons of direct attack, and as a particular type of simple tool that made up for comparative lack of natural weapons, such as claws, horns and teeth, in the human physiology. The first human use of weapons is not easy to date, as these would probably have been wooden clubs, spears and unshaped stones thrown at prey or enemy—and none of these would leave an unambiguous record.

The earliest examples found are a cache of eight wooden throwing spears, the Schöninger Speere, which have been dated as 400,000 years ago.[6] By 250,000 years ago wooden spears were made with fire-hardened points. From 80,000 years ago humans began to make complex stone blades, which were used as spear points. Bows and arrows may have been used by 60,000 years ago[7]

[edit] Ancient world weapons

A four-wheeled ballista drawn by armored horses, c. 400. Ancient weapons were in many ways qualitative improvements of the late prehistoric versions, with significant improvement in materials and techniques used, that created the first revolutions in military technology. Light, horse-drawn chariots for use in battle appeared with the invention of the spoked wheel. The earliest spoke-wheeled chariots date to ca. 2000 BC and their usage peaked around 1300 BC (see Battle of Kadesh). Chariots ceased to have military importance in the 4th century BC, as horses were bred to support the weight of a man, and chariotry (the part of a military force that fought from chariots) gave way to cavalry.[8]

[edit] Weapons of the Middle Ages

Ancient Chinese cannon displayed in the Tower of London. The Medieval period, including the Western Middle Ages, was characterized by two iconic Medieval weapons: knights, heavily-armored horsemen, and the rudimentary siege artillery to negate the increased use of castles, fortified dwellings which proliferated throughout Europe and the near east. While knights were an evolutionary development of the earlier historical cavalry such as the Roman and Persian cataphracts, siege artillery used to breach castle walls triggered quite revolutionary advances, including increasingly sophisticated siegecraft using gunpowder weapons, the cannon.

[edit] Early modern period weapons The Renaissance marked the beginning of the implementation of firearms in warfare, with the introduction of guns and rockets to the battlefield.

Firearms are qualitatively different from earlier weapons because they store energy in a combustible propellant such as gunpowder, rather than in a weight or spring. This energy is released quite rapidly, and can be restored without much effort by the user, so that even early firearms such as the arquebus were much more powerful than human-powered weapons. They became increasingly important and effective during the 16th century to 19th century, with progressive improvements in ignition mechanisms followed by revolutionary changes in ammunition handling and propellant. During the U.S. Civil War various technologies including the machine gun and ironclad warship emerged that would be recognizable and useful military weapons today, particularly in lower-technology conflicts. In the 19th century warship propulsion changed from sail power to fossil fuel-powered steam engines.

The bayonet is used as both knife and polearm. The age of edged weapons ended abruptly just before World War I with rifled artillery, such as howitzers which were able to destroy any masonry fortress, as well as destroy other fortifications. This single invention caused a revolution in military affairs and doctrines that continues to this day. See Technology during World War I for a detailed discussion. An important feature of industrial age warfare was technological escalation - an innovation could, and would, be rapidly matched by copying it, and often with yet another innovation to counter it. The technological escalation during World War I was profound, producing armed aircraft and tanks. This continued in the period between the end of that war and the next, with continuous improvements of all weapons by all major powers. Many modern military weapons, particularly ground-based ones, are relatively minor improvements on those of World War II. See military technology during World War II for a detailed discussion.

[edit] Modern weapons

The Maxim gun and its successor the Vickers (shown here) remained in British military service for 79 consecutive years. From the American Revolution[citation needed] through the beginning of the 20th century, human-powered weapons were finally excluded from the battlefield for the most part. Sometimes referred to as the "Age of Rifles"[9], this period was characterized by the development of firearms for infantry and cannons for support, as well as the beginnings of mechanized weapons such as the machine gun, the tank and above all the wide introduction of aircraft into warfare, including naval warfare with the introduction of the aircraft carriers. World War I marked the entry of fully industrialized warfare, and weapons were developed quickly to meet wartime needs. Above all it promosed to the military commanders the independence from the horse and the resurgence in manoeuvre warfare through extensive use of motor vehicles. The changes that these military technologies underwent before and during the Second World War were evolutionary, but defined the development for the rest of the century. World War II however,

perhaps marked the most frantic period of weapons development in the history of humanity. Massive numbers of new designs and concepts were fielded, and all existing technologies were improved between 1939 and 1945. The most powerful weapon invented during this period was the atomic bomb.

[edit] Weapon development since the Second World War After World War II, with the onset of the Cold War, the constant technological development of new weapons was institutionalized, as participants engaged in a constant race to develop weapons and counterweapons. This constant state of weapons development continues into the modern era, and remains a constant draw on the resources of most nations. The most notable development in weaponry since World War II has been the combination and further development of two weapons first used in it—nuclear weapons and the ballistic missile, leading to its ultimate configuration: the ICBM. The mutual possession of these by the United States and the Soviet Union ensured that either nation could inflict terrible damage on the other; so terrible, in fact, that neither nation was willing to instigate direct, all-out war with the other (a phenomenon known as Mutually Assured Destruction). The indiscriminate nature of the destruction has made nuclear-tipped missiles essentially useless for the smaller wars fought since. However computer-guided weaponry of all kinds, from precision-guided munitions (or "smart bombs") to computer-aimed tank rounds, has greatly increased weaponry's accuracy.

India's Agni-II, a ballistic missile. (Photo: Antônio Milena/ABr) Being able to prepare, maneuver and attack before the enemy can detect the threat and respond can be a decisive advantage. The element of surprise has long been recognized as a tactical advantage. Modern technology can increase this, such as when one side has sophisticated night vision technology allowing maneuvering and combat at night when the enemy, not so equipped, is limited. High tech surveillance and intelligence gathering methods such as pilotless drones can prevent surprise or identify targets. Coordination of forces is necessary in order to utilize separated forces effectively, modern communications, if unjammed and unintercepted are substantial advantages. Even once targets or strategic objectives are identified, it is necessary to prepare detailed plans for individual forces to follow, a time consuming process that modern armies are trying to computerize to achieve an advantage of speed over the enemy.[citation needed] Since interfering with enemy infrastructure, intelligence and communications yields an advantage, and a weapon is defined as something that grants such an advantage, new targets and weapons such as cyberwarfare are becoming possible.

[edit] Classification of weapons There are essentially three facets to classifying weapon systems: who uses it, how it works, and what it targets. The categorisation is also subject to the combat environment in which the weapon, or its platform is used, generally on land, on or in the water, in the atmosphere, or in space. These combat environments

set unique engineering design criteria for user proficiency, system complexity and therefore affordability, and the capability it offers against specific types of threats. Who uses it essentially determines how it can be employed: • • • • • • • • •

Personal weapons (or small arms) are designed to be used by a single person. Infantry support weapons are larger than personal weapons, requiring more than one crew member to operate correctly. Fortification weapons are designed to be mounted in a permanent installation, or used primarily within a fortification. Mountain weapons are designed for use by mountain forces or those operating in difficult terrain and harsh climates. Vehicle weapons are designed to be mounted on any type of military vehicle. Railway weapons are designed to be mounted on railway cars, including armored trains. Aircraft weapons are designed to be carried on and used by some type of aircraft, helicopter, or other aerial vehicle. Naval weapons are designed to be mounted on ships and submarines. Space weapons are designed to be used in or launched from space.

How it works refers to the construction of the weapon and how it operates: • • • • • • • • • • • • • • • • • •

Antimatter weapons (still theoretical) would combine matter and antimatter to cause a powerful explosion. However, antimatter is still hard to make and harder to store. Archery related weapons operate by using a tensioned string to launch a projectile at some target. Artillery are large firearms capable of launching heavy projectiles (normally explosive) over long distances. Biological weapons spread biological agents, attacking humans (or livestock) by causing disease and infection. Chemical weapons spread chemical agents, attacking humans by poisoning and causing reactions. Energy weapons rely on concentrating forms of energy to attack, such as lasers, electrical shocks, and thermal or sonic attack. Explosive weapons use a physical explosion to create blast concussion or spread shrapnel. Firearms use a chemical charge to launch one or more projectiles down a rifled or smoothbore barrel. Improvised weapons are common objects that were not designed for combat purposes but are used as such in self defense, guerrilla warfare or a violent crime. Incendiary weapons rely on combustible materials and an ignition mechanism to cause damage by fire. Non-lethal weapons are used to attack and subdue humans, but are designed to minimize the risk of killing the target. Magnetic weapons is one that uses magnetic fields to accelerate and propel projectiles, or to focus charged particle beams. Mêlée weapons operate as physical extensions of the user's body and directly impact their target. Missiles are rockets which are guided to their target after launch. This is also a general term for projectile weapons. Nuclear weapons use radioactive materials to create nuclear fission and/or nuclear fusion detonations above a target (air burst) or at ground-level (ground burst). Primitive weapons make little or no use of technological or industrial elements, instead being purely constructed of easily obtainable natural materials. Ranged weapons cause a projectile to leave the user and (ideally) strike a target afterwards. Rockets use chemical propellant to accelerate a projectile (usually with an explosive warhead) towards a target and are typically unguided once fired.

•

Suicide weapons are typically explosive in nature and exploit the willingness of their operator to not survive the attack to reach their target.

What it targets refers to what type of target the weapon is designed to attack: • •

• • • • • • • •

Anti-aircraft weapons target enemy aircraft, helicopters, missiles and any other aerial vehicles in flight. Anti-fortification weapons are designed to target enemy installations, including bunkers and fortifications. The American bunker buster bomb is designed to travel almost 10 metres underground before detonating, toppling underground installations. Anti-personnel weapons are designed to attack people, either individually or in numbers. Anti-radiation weapons target enemy sources of electronic radiation, particularly radar emitters. Anti-ship weapons target enemy ships and vessels on water. Anti-submarine weapons target enemy submarines and other underwater targets. Anti-tank weapons are primarily used to defeat armored targets, but may be targeted against other less well armored targets. Area denial weapons are designed to target territory, making it unsafe or unsuitable for enemy use or travel. Hunting weapons are designed particularly for use against animals for hunting purposes. Infantry support weapons are designed to attack various threats to infantry units, supporting the infantry's operations, including heavy machine guns, mortars and pinpoint airstrikes ordered by the infantry, often to strike heavily defended positions, such as enemy camps or extensively powerful machine-gun nests.

[edit] See also • • • • • •

Arms trade List of martial arts weapons List of weapons Riot control agent Toy weapons Weapons of mass destruction

[edit] Citations and notes

Crime From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Crime (disambiguation). Crime is the breach of one or more rules or laws for which some governing authority or force may ultimately prescribe a punishment. The word crime originates from the Latin crimen (genitive criminis), from the Latin root cernō and Greek κρινω = "I judge". Originally it meant "charge (in law), guilt, accusation". When society deems informal relationships and sanctions insufficient to create and maintain a desired social order, there may result more formalized systems of social control imposed by a government, or more broadly, by a State. With the institutional and legal machinery at their disposal, agents of the State

can compel individuals to conform to behavioural codes and punish those that do not. Various mechanisms are employed to regulate behaviour, including rules codified into laws, policing people to ensure they comply with those laws, and other policies and practices designed to prevent crime. In addition are remedies and sanctions, and collectively these constitute a criminal justice system. Not all breaches of the law, however, are considered crimes, for example, breaches of contract and other civil law offences. The label of "crime" and the accompanying social stigma are normally reserved for those activities that are injurious to the general population or the State, including some that cause serious loss or damage to individuals. The label is intended to assert an hegemony of a dominant population, or to reflect a consensus of condemnation for the identified behavior and to justify a punishment imposed by the State, in the event that an accused person is tried and convicted of a crime. Usually, the perpetrator of the crime is a natural person, but in some jurisdictions and in some moral environments, legal persons are also considered to have the capability of committing crimes.

Contents [hide]

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1 Definition 2 Criminalization 3 History 4 Natural-law theory 5 Distinctions 6 Types o 6.1 U.S. classification 7 Crimes against international law 8 Religion and crime 9 Military jurisdictions and states of emergency 10 Employee crime 11 See also o 11.1 Statistics 12 Notes 13 References

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14 External links

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[edit] Definition A normative definition views crime as deviant behavior that violates prevailing norms – cultural standards prescribing how humans ought to behave normally. This approach considers the complex realities surrounding the concept of crime and seeks to understand how changing social, political, psychological, and economic conditions may affect the current definitions of crime and the form of the legal, law enforcement, and penal responses made by society. These structural realities remain fluid and often contentious. For example, as cultures change and the political environment shifts, behavior may be criminalised or decriminalised, which will directly affect the statistical crime rates, determine the allocation of resources for the enforcement of such laws, and influence the general public opinion. Similarly, changes in the way that crime data are collected and/or calculated may affect the public perceptions of the extent of any given "crime problem". All such adjustments to crime statistics, allied with the experience of people in their everyday lives, shape attitudes on the extent to which law should be used to enforce any particular social norm. There are many ways in which behaviour can be controlled without having to resort to the criminal justice system. Indeed, in those cases where there is no clear

consensus on the given norm, the use of criminal law by the group in power to prohibit the behaviour of another group may be considered an improper limitation of the second group's freedom, and the ordinary members of society may lose some of their respect for the law in general whether the disputed law is actively enforced or not. Legislatures pass laws (called mala prohibita) that define crimes which violate social norms. These laws vary from time to time and from place to place: note variations in gambling laws, for example. Other crimes, called mala in se, are nearly universally outlawed, such as murder, theft and rape

[edit] Criminalization Main article: Criminalization •

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One can view criminalization as a procedure intended as a pre-emptive, harm-reduction device, using the threat of punishment as a deterrent to those proposing to engage in the behavior causing harm. The State becomes involved because they usually believe costs of not criminalizing (i.e. allowing the harms to continue unabated) outweigh the costs of criminalizing it (i.e. restricting individual liberty in order to minimize harm to others). Criminalization may provide future harm-reduction even after a crime, assuming those incarcerated for committing crimes are more likely to cause harm in the future.[clarification needed] Criminalization might be intended as a way to make potential criminals pay for their crimes. In this case, criminalization is a way to set the price that one must pay (to society) for certain actions that are considered detrimental to society as a whole. In this sense criminalization can be viewed as nothing more than State-sanctioned revenge.

States control the process of criminalization because: •

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Even if victims recognize their own role as victims, they may not have the resources to investigate and seek legal redress for the injuries suffered: the enforcers formally appointed by the State have the expertise and the resources. The victims may only want compensation for the injuries suffered, while being indifferent to a possible desire for deterrence (see Polinsky & Shavell (1997) on the fundamental divergence between the private and the social motivation for using the legal system). Fear of retaliation may deter victims or witnesses of crimes from taking any action. Even in policed societies, fear may inhibit reporting or co-operation in a trial. Victims alone may lack the economies of scale which might allow them to administer a penal system, let alone collect any fines levied by a court (see Polinsky (1980) on the enforcement of fines). Garoupa & Klerman (2002) warn that a rent-seeking government has as its primary motivation to maximize revenue and so, if offenders have sufficient wealth, a rent-seeking government will act more aggressively than a social-welfare-maximizing government in enforcing laws against minor crimes (usually with a fixed penalty such as parking and routine traffic violations), but more laxly in enforcing laws against major crimes. As a result of the crime, victims may die or become incapacitated.

[edit] History The earliest known civilizations had codes of law, containing both civil and penal rules mixed together, though not always in recorded form. The Sumerians produced the earliest surviving written codes,[1] and it is known that Urukagina had an early code that does not survive. A later king, Ur-Nammu left the earliest code that has been discovered, creating a formal system of prescribed penalties for specific cases in 57 articles, the Code of Ur-Nammu. The Sumerians later issued other codes, including the "code of Lipit-

Ishtar". This code, from the 20th century BCE, contains some fifty articles, and has been reconstructed by comparison among several sources. The Sumerian was deeply conscious of his personal rights and resented any encroachment on them, whether by his King, his superior, or his equal. No wonder that the Sumerians were the first to compile laws and law codes. — Kramer[2]

Successive legal codes in Babylon, including the code of Hammurabi, reflected Mesopotamian society's belief that law derived from the will of the gods (see Babylonian law).[3] Many states at this time functioned as theocracies, with codes of conduct largely religious in origin or reference. Sir Henry Maine (1861) studied the ancient codes available in his day, and failed to find any criminal law in the "modern" sense of the word. While modern systems distinguish between offences against the "State" or "Community", and offences against the "Individual", the so-called penal law of ancient communities was not the law of "Crimes" (crimina); it was the law of "Wrongs" (delicta). Thus, the Hellenic laws[4] treated all forms of theft, assault, rape, and murder as private wrongs, and left action for enforcement up to the victims or their survivors. The earliest systems seem to have lacked formal courts. The Romans systematized law and exported it across their Empire. Again, the initial rules of Roman Law regarded assaults as a matter of private compensation. The most significant Roman Law concept involved dominion.[5] The pater familias owned all the family and its property (including slaves); the pater enforced matters involving interference with any property. The Commentaries of Gaius on the Twelve Tables treated furtum (in modern parlance: theft) as a tort. Similarly, assault and violent robbery involved trespass as to the pater's property (so, for example, the rape of a slave could become the subject of compensation to the pater as having trespassed on his "property"), and breach of such laws created a vinculum juris (an obligation of law) that only the payment of monetary compensation (modern "damages") could discharge. Similarly, the consolidated Teutonic Laws of the Germanic tribes,[6] included a complex system of monetary compensations for what courts would now consider the complete range of criminal offences against the person, from murder down. Even though Rome abandoned its Britannic provinces sometime around 400 AD, the Germanic mercenaries – who had largely become instrumental in enforcing Roman rule – acquired ownership of the land there and continued to use a mixture of Roman and Teutonic Law, with much written down under the early Anglo-Saxon Kings.[7] But only when a more centralized English monarchy emerged following the Norman invasion, and the kings of England attempted to assert power over the land and its peoples, did the modern concept emerge, namely of a crime not only as an offence against the "individual", but also as a wrong against the "State".[8] This idea came from common law, and the earliest conception of a criminal act involved events of such major significance that the "State" had to usurp the usual functions of the civil tribunals, and direct a special law or privilegium against the perpetrator. All the earliest English criminal trials involved wholly extraordinary and arbitrary courts without any settled law to apply, whereas the civil delictual law operated in a highly developed and consistent manner (except where a King wanted to raise money by selling a new form of writ). The development of the idea that the "State" dispenses justice in a court only emerges in parallel with or after the emergence of the concept of sovereignty. In continental Europe, Roman Law persisted, but with a stronger influence from the Church.[9] Coupled with the more diffuse political structure based on smaller State units, various different legal traditions emerged, remaining more strongly rooted in Roman jurisprudence modified to meet the prevailing political climate. In Scandinavia, the effect of Roman law did not become apparent until the 17th century, and the courts grew out of the things — the assemblies of the people. The cases were decided by the people (usually largest freeholders dominating) which later gradually transformed into a system of a royal

judge nominating a number of most esteemed men of the parish as his board, fulfilling the function of "the people" of yore. From the Hellenic system onwards, the policy rationale for requiring the payment of monetary compensation for wrongs committed has involved the avoidance of feuding between clans and families.[10] If families' feelings could be mollified by compensation, this would help to keep the peace. On the other hand, the threat of feudal warfare was played down also by the institution of oaths. Both in archaic Greece and in medieval Scandinavia, the accused was released if he could get a sufficient number of male relatives to swear him unguilty. This may be compared with the United Nations Security Council where the veto power of the permanent members ensures that the organization is not drawn into crises where it could not enforce its decisions. These means of restraining private feuds did not always work or prevented the fulfillment of justice but, in the earliest times, the "States" were not prepared to provide an independent police force. Thus, criminal law grew out of what is now tort and, in real terms, many acts and omissions that are classified as crimes overlap civil law concepts. The development of sociological thought from the 19th century onwards prompted some fresh views on crime and criminality, and fostered the beginnings of criminology as a study of crime in society. Nietzsche noted a link between crime and creativity – in The Birth of Tragedy he asserted: "The best and brightest that man can acquire he must obtain by crime". In the 20th century Michel Foucault in Discipline and Punish made a study of criminalization as a coercive method of state control.

[edit] Natural-law theory Justifying the State's use of force to coerce compliance with its laws has proven a consistent theoretical problem. One of the earliest justifications involved the theory of natural law. This posits that the nature of the world or of human beings underlies the standards of morality or constructs them. Thomas Aquinas said: "the rule and measure of human acts is the reason, which is the first principle of human acts" (Aquinas, ST I-II, Q.90, A.I), i.e. since people are by nature rational beings, it is morally appropriate that they should behave in a way that conforms to their rational nature. Thus, to be valid, any law must conform to natural law and coercing people to conform to that law is morally acceptable. William Blackstone (1979: 41) describes the thesis: "This law of nature, being co-eval with mankind and dictated by God himself, is of course superior in obligation to any other. It is binding over all the globe, in all countries, and at all times: no human laws are of any validity, if contrary to this; and such of them as are valid derive all their force, and all their authority, mediately or immediately, from this original." But John Austin, an early positivist, applied utilitarianism in accepting the calculating nature of human beings and the existence of an objective morality, but denied that the legal validity of a norm depends on whether its content conforms to morality. Thus in Austinian terms a moral code can objectively determine what people ought to do, the law can embody whatever norms the legislature decrees to achieve social utility, but every individual remains free to choose what he or she will do. Similarly, Hart (1961) saw the law as an aspect of sovereignty with lawmakers able to adopt any law as a means to a moral end. Thus, the necessary and sufficient conditions for the truth of a proposition of law were simply that the law was internally logical and consistent, and that State power was being used with responsibility. Dworkin (2005) rejects Hart's theory and argues that fundamental among political rights is the right of each individual to the equal respect and concern of those who govern him. He offers a theory of compliance overlaid by a theory of deference (the citizen's duty to obey the law) and a theory of enforcement, which identifies the legitimate goals of enforcement and punishment. Legislation must conform to a theory of legitimacy, which describes the circumstances under which a particular person or group is entitled to make law, and a theory of legislative justice, which describes the law they are entitled or obliged to make.

Indeed, despite everything, the majority of natural-law theorists have accepted the idea of enforcing the prevailing morality as a primary function of the law. This view entails the problem that it makes any moral criticism of the law impossible in that, if conformity with natural law forms a necessary condition for legal validity, all valid law must, by definition, be morally just. Thus, on this line of reasoning, the legal validity of a norm necessarily entails its moral justice. The solution to this problem is to admit some degree of moral relativism and to accept that norms may evolve over time and, therefore, the continued enforcement of old laws may be criticized in the light of the current norms. The law may be acceptable but the use of State power to coerce citizens to comply with that law is not morally justified. In more modern conceptions of the theory, crime is characterized as the violation of individual rights. Since so many rights are considered as natural, hence the term "right", rather than man-made, what constitutes a crime is also natural, in contrast to laws, which are man-made. Adam Smith illustrates this view, saying that a smuggler would be an excellent citizen, "...had not the laws of his country made that a crime which nature never meant to be so." Natural-law theory therefore distinguishes between "criminality" (which derives from human nature) and "illegality" (which originates with the interests of those in power). Lawyers sometimes express the two concepts with the phrases malum in se and malum prohibitum respectively. A crime malum in se (they argue) is inherently criminal; whereas a crime malum prohibitum is argued to be criminal only because the law has decreed it so. This view leads to a seeming paradox, that an act can be illegal that is no crime, while a criminal act could be perfectly legal. Many Enlightenment thinkers such as Adam Smith and the American Founding Fathers subscribed to this view to some extent, and it remains influential among socalled classical liberals[citation needed] and libertarians[citation needed].

[edit] Distinctions

Religious sentiment often become a contributory factor of crime. Rioters set fire to many of Ahmedabad's buildings during the 2002 Gujarat violence. Governments criminalise antisocial behaviour — and treat it within a system of offences against society — in order to justify the imposition of punishment. Authorities make a series of distinctions depending on the passive subject of the crime (the victim), or on the offended interest(s), in crimes against: • • • • • • •

personality of the State rights of the citizen public administration administration of justice religious sentiment and faith public order public economy, industry, and commerce

• • •

public morality. person and honour. patrimony

Or one can categorise crimes depending on the related punishment with sentencing tariffs prescribed in line with the perceived seriousness of the offence with fines and noncustodial sentences for the least serious, and (in some States) capital punishment for the most serious.

[edit] Types Researchers and commentators may classify crime into categories, including violent crime, property crime, and public order crime.

[edit] U.S. classification In the United States since 1930, the FBI has tabulated Uniform Crime Reports (UCR) annually from crime data submitted by law enforcement agencies across the United States.[11] Officials compile this data at the city, county, and state levels into the Uniform crime reports (UCR). They classify violations of laws which derive from common law as Part I (index) crimes in UCR data, further categorised as violent or property crimes. Part I violent crimes include murder and criminal homicide (voluntary manslaughter), forcible rape, aggravated assault, and robbery, while Part I property crimes include burglary, arson, larceny/theft, and motor vehicle theft. All other crimes are classified as Part II crimes. Analysts can also group crimes by severity, some common categorical terms including: • • • •

felonies (US and previously UK) indictable offences (UK) misdemeanors (US and previously UK) summary offences (UK)

For convenience, such lists usually include infractions although, in the U.S., they may not be the subject of the criminal law, but rather of the civil law. Compare tortfeasance.

[edit] Crimes against international law Crimes defined by treaty as crimes against international law include: • • • • • • •

crimes against peace waging a war of aggression crimes of apartheid piracy genocide war crimes the slave trade

From the point of view of State-centric law, extraordinary procedures (usually international courts) may prosecute such crimes. Note the role of the International Criminal Court at The Hague in the Netherlands.

[edit] Religion and crime

Socially accepted or imposed religious morality has influenced secular jurisdictions on issues that may otherwise concern only an individual's conscience. Activities sometimes criminalized on religious grounds include (for example) alcohol-consumption (prohibition), abortion and stem cell research. In various historical and present-day societies institutionalized religions have established systems of earthly justice which punish crimes against the divine will and specific devotional, organizational and other rules under specific codes, such as Islamic sharia or Roman Catholic canon law.

[edit] Military jurisdictions and states of emergency In the military sphere, authorities can prosecute both regular crimes and specific acts (such as mutiny or desertion) under martial-law codes that either supplant or extend civil codes in times of war. Many constitutions contain provisions to curtail freedoms and criminalize otherwise tolerated behaviors under a state of emergency in the event of war, natural disaster or civil unrest. Such undesired activities may include assembly in the streets, violation of curfew, or possession of firearms.

[edit] Employee crime Two common types of employee crime exist: embezzlement and sabotage.[citation needed] The complexity and anonymity of computers may help sinister employees camouflage their crimes. The victims of the most costly scams include banks, brokerage houses, insurance companies, and other large financial institutions. [12] Most people guilty of embezzlement do not have criminal histories. It is more likely that they have a gripe against their employer, have financial problems, or simply can't resist the temptation of a loop-hole they have found. Screening and background checks on perspective employees can help; however, many laws make some types of screening difficult or even illegal. Fired or disgruntled employees sometimes sabotage their company's computer system as a form of 'pay back'.[12] This sabotage may take the form of a Logic bomb, a computer virus, or creating general havoc. Some places of employment have developed measures in an attempt to combat and prevent employee crime. Places of employment sometimes implement security measures such as cameras, fingerprint records of employees, and background checks.[citation needed] Although privacy-advocates have questioned such methods, they serve the interests of the companies using them. Not only do these methods help prevent employee crime, but they protect the company from punishment and/or lawsuits for negligent hiring.[13][verification needed]

[edit] See also • • • • • • • • • • • •

Actus reus Case law Civil law Corrections Crime importation Crime Library Crime mapping Crime in Brazil Crime in Mexico Crime in the United States Criminal justice Criminal law

• • • • • • • • • • •

Fear of crime Gang Insanity defense Juvenile delinquency Law and order Neighborhood watch Organized Crime Outlaw Penal colony Timeline of organized crime from 1870 Victimology

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Victimless crime (political philosophy)

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Criminal record

[edit] Statistics • • • • •

Crime rate Murder statistics Rape statistics List of countries by murder rate United States cities by crime rate

[edit] Notes

From Wikipedia, the free encyclopedia

(Redirected from Shy) Jump to: navigation, search "Shy" redirects here. For other uses, see Shy (disambiguation). The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008) In humans, shyness (also called diffidence) is a social psychology term used to describe the feeling of apprehension, lack of confidence, or awkwardness experienced when a person is in proximity to, approaching, or being approached by other people, especially in new situations or with unfamiliar people. The term is often used by laypersons as a blanket-term for a family of related and partially overlapping

afflictions, including timidity around new people, bashfulness and diffidence, lack of assertiveness, apprehension and anticipation of interaction, social anxiety, or intimidation. Shyness may come from personality introversion, genetic traits, or the environment in which a person is raised. In zoology, shy generally means "tends to avoid human beings"; See crypsis. Shyness in animals manifests with ostensibly similar behavioral traits, but differs wholly from humans in cognition and motivation.

Contents [hide]

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1 Triggers, traits and misperception o 1.1 Complications 2 Origins o 2.1 Genetics and heredity o 2.2 As symptom of mercury poisoning 3 See also 4 References

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5 External links

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[edit] Triggers, traits and misperception Shyness is most likely to occur during unfamiliar situations, though in severe cases it may hinder an individual in his or her most familiar situations and relationships as well. Shy individuals avoid the objects of their apprehension in order to avoid feeling uncomfortable and inept, thus the situations remain unfamiliar and the shyness perpetuates itself. Shyness may fade with time (a child who is shy toward strangers, for instance, may eventually lose this trait when older and more socially adept), often by adolescence and young adulthood (most likely around the age of 13), or it may be an integrated, life-long character trait. Humans experience shyness to different degrees and in different areas. For example, an actor may be loud and bold on stage, but shy in an interview. In addition, shyness may manifest when one is in the company of certain people and completely disappear when with others—one may be outgoing with friends and family, but experience love-shyness toward potential partners, even if strangers are generally not an obstacle. The condition of true shyness may simply involve the discomfort of difficulty in knowing what to say in social situations, or may include crippling physical manifestations of uneasiness. Shyness usually involves a combination of both symptoms, and may be quite devastating for the sufferer, in many cases leading them to feel that they are boring, or exhibit bizarre behavior in an attempt to create interest, alienating them further. Instinctive behavioral traits in social situations such as smiling, easily producing suitable conversational topics, assuming a relaxed posture and making good eye contact, which come spontaneously for the average person, may not be second nature for a shy person, requiring struggle or being completely unattainable. Shyness is considered to be a neutral personality trait by people who are not shy, but a very negative trait by those who are shy themselves.

[edit] Complications The term shyness may be implemented as a lay blanket-term for a family of related and partially overlapping afflictions, including timidity (apprehension in meeting new people), bashfulness and

diffidence (lack of assertiveness), apprehension and anticipation (general fear of potential interaction), or intimidation (relating to the object of fear rather than one's low confidence).[1] Apparent shyness, as perceived by others, may simply be the manifestation of reservation or introversion, character traits which cause an individual to voluntarily avoid excessive social contact or be terse in communication, but are not motivated or accompanied by discomfort, apprehension, or lack of confidence. Rather, according to Bernardo J. Carducci, director of the Shyness Research Institute, introverts choose to avoid social situations because they derive no reward from them, or may find surplus sensory input overwhelming. Conversely, shy people fear such situations and feel that they must avoid them. [2] Shy people tend to perceive their own shyness as a negative trait, and many people are uneasy with shyness in others, especially in cultures which value individuality and taking charge. This generally poor reception of shyness may be misinterpreted by the suffering individual as aversion related to his or her personality, rather than simply to his or her shyness. Both conditions can lead to a compounding of a shy individual's low self-confidence. In some cultures which value outspokenness and overt confidence, shyness can be perceived as weakness. To an unsympathetic observer, a shy individual may be mistaken as cold, distant, arrogant or aloof, which can be frustrating for the shy individual. However in other cultures, shy people may be perceived as being thoughtful, intelligent, as being good listeners, and as being more likely to think before they speak. Furthermore, boldness, the opposite of shyness, may cause its own problems, such as impertinence or inappropriate behavior.

[edit] Origins The initial causes of shyness vary. Scientists have located some genetic data that supports the hypothesis that shyness is at least partially genetic. However, there is also evidence that the environment in which a person is raised can affect their shyness. This includes child abuse, particularly emotional abuse such as ridicule. Shyness can originate after a person has experienced a physical anxiety reaction; at other times, shyness seems to develop first and then later causes physical symptoms of anxiety. Shyness differs from social anxiety, which is a broader, often depression-related psychological condition including the experience of fear, apprehension or worry about being evaluated by others in social situations to the extent of inducing panic.

[edit] Genetics and heredity The genetics of shyness is a relatively small area of research that has been receiving an even smaller amount of attention, although papers on the biological bases of shyness date back to 1988. Some research has indicated that shyness and aggression are related—through long and short forms of the gene DRD4, though considerably more research on this is needed. Further, it has been suggested that shyness and social phobia (the distinction between the two is becoming ever more blurred) are related to obsessivecompulsive disorder. As with other studies of behavioral genetics, the study of shyness is complicated by the number of genes involved in, and the confusion in defining, the phenotype. Naming the phenotype – and translation of terms between genetics and psychology — also causes problems. In some research, "behavioral inhibition" is studied, in others anxiety or social inhibition is. One solution to this problem is to study the genetics of underlying traits, such as "anxious temperament." Several genetic links to shyness are current areas of research. One is the serotonin transporter promoter region polymorphism (5-HTTLPR), the long form of which has been shown to be modestly correlated with shyness in grade school children.[1] Previous studies had shown a connection between this form of the gene and both obsessive-compulsive disorder and autism.[citation needed] Mouse models have also been used, to derive genes suitable for further study in humans; one such gene, the glutamic acid decarboxylase

gene (which encodes an enzyme that functions in GABA synthesis), has so far been shown to have some association with behavioral inhibition. Another gene, the dopamine D4 receptor gene (DRD4) exon III polymorphism, had been the subject of studies in both shyness and aggression, and is currently the subject of studies on the "novelty seeking" trait. A 1996 study of anxiety-related traits (shyness being one of these) remarked that, "Although twin studies have indicated that individual variation in measures of anxiety-related personality traits is 40-60% heritable, none of the relevant genes has yet been identified," and that "10 to 15 genes might be predicted to be involved" in the anxiety trait. Progress has been made since then, especially in identifying other potential genes involved in personality traits, but there has been little progress made towards confirming these relationships. The long version of the 5-HTT gene-linked polymorphic region (5-HTTLPR) is now postulated to be correlated with shyness,[1] but in the 1996 study, the short version was shown to be related to anxiety-based traits. This confusion and contradiction does not oppose the genetic basis of personality traits, but does emphasize the amount of research there is still to be done before the bases of even one or two of these characteristics can be identified.

[edit] As symptom of mercury poisoning Excessive shyness, embarrassment, self consciousness and timidity, social-phobia and lack of selfconfidence are also components of erethism, which is a symptom complex that appears in cases of mercury poisoning[2][3]. Mercury poisoning was common among hat makers in England in the 1700s and 1800s, who used mercury to stabilize the wool into felt fabric.

[edit] See also Psychology portal • • • • • • • • •

Boldness Love-shyness Introversion Social anxiety Social anxiety disorder Selective mutism Avoidant personality disorder Highly sensitive person Schizoid Personality Disorder

[edit] References • •

•

Kluger, A. N.; Siegfried, Z.; Epbstein, R. P.: A meta-analysis of the association between DRD4 polymorphism and novelty seeking. Molecular Psychiatry 2002; 7: 712-717. Lesch, Klaus-Peter; Bengal, Dietmar; Heils, Armin; Sabol, Sue Z.; Greenberg, Benjamin D.; Petri, Susanne; Benjamin, Jonathan; Muller, Clemens R.; Hamer, Dean H.; Murphy, Dennis L.: Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region. Science 1996; 274(5292): 1527-1531. Smoller, Jordan W.; Rosenbaum, Jerold F.; Biederman, Joseph; Susswein, Lisa S.; Kennedy, John; Kagan, Jerome; Snidman, Nancy; Laird, Nan; Tsuang, Ming T.; Faraone, Stephen V.; Schwarz, Alysandra; Slaugenhaupt, Susan A.: Genetic association analysis of behavioral inhibition using candidate loci from mouse models. American Journal of Medical Genetics 2001; 105: 226-235.

1. ^ a b Shoshana Arbelle, Jonathan Benjamin, Moshe Golin, Ilana Kremer, Robert H. Belmaker & Richard P. Ebstein (April 2003). "Relation of shyness in grade school children to the genotype for the long form of the serotonin transporter promoter region polymorphism". The American journal of psychiatry 160 (4): 671– 676. PMID 12668354. 2. ^ WHO (1976) Environmental Health Criteria 1: Mercury, Geneva, World Health Organization, 131 pp. 3. ^ WHO. Inorganic mercury. Environmental Health Criteria 118. World Health Organization, Geneva, 1991.

[edit] External links

Calmness From Wikipedia, the free encyclopedia

Jump to: navigation, search This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2007) Calmness is a mental state wherein the mind is not turbulent, but open and reflective. No emotions are agitating the mind and no insistent train of thought is disturbing the mind. Calmness can most easily occur for the average person during a state of relaxation, but it can also be found during much more alert and aware states. Some people find that focusing the mind on something external, or even internal, such as the breathing, can itself be very calming. Calmness is a quality that can be cultivated and increased with practice. It usually takes a trained mind to stay calm in the face of a great deal of different stimulation, and possible distractions, especially emotional ones. The negative emotions are the greatest challenge to someone who is attempting to cultivate a calm mind. Some disciplines that promote and develop calmness are yoga, relaxation training, breath training, and meditation practices.

[edit] See also Look up calmness in Wiktionary, the free dictionary. •

Ataraxia

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Emotions (list) Acceptance · Affection · Alertness · Ambivalence · Anger · Angst · Annoyance · Anticipation · Anxiety · Apathy · Awe · Boredom · Calmness · Compassion · Confusion · Contempt · Contentment · Curiosity · Depression · Desire · Disappointment · Disgust · Doubt · Ecstasy · Embarrassment · Empathy · Emptiness · Enthusiasm · Envy · Epiphany · Euphoria · Fanaticism · Fear · Frustration · Gratification · Gratitude · Grief · Guilt · Happiness · Hatred · Homesickness · Honesty · Hope · Hostility · Humiliation · Hysteria · Inspiration · Interest · Jealousy · Kindness · Limerence · Loneliness · Love · Lust · Melancholia · Nostalgia · Panic · Patience · Pity · Pride · Rage · Regret · Remorse · Repentance · Resentment · Righteous indignation · Sadness · Saudade · Schadenfreude · Sehnsucht · Self-pity · Shame · Shyness · Suffering · Surprise · Suspicion · Sympathy · Wonder · Worry

This psychology-related article is a stub. You can help Wikipedia by expanding it. Retrieved from "http://en.wikipedia.org/wiki/Calmness" Category: Psychology stubs Hidden category: Articles needing additional references from September 2007

Water From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the chemical substance. For its chemical and physical properties, see water (molecule). For other uses, see Water (disambiguation).

Water in three states: liquid, solid (ice), and (invisible) vapor in air. Clouds are droplets of liquid, condensed from water vapor. Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. About 1.460 petatonnes (Pt) (1021kilograms) of water covers 71% of the Earth's surface[1], mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[2] Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%,

and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within water towers, biological bodies, manufactured products, and food stores. Other water is trapped in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land. Water moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt (1012kilograms) per year. Over land, evaporation and transpiration contribute another 71 Tt per year to the precipitation of 107 Tt per year over land. Clean, fresh drinking water is essential to human and other life. However, in many parts of the world—especially developing countries—there is a water crisis, and it is estimated that by 2025 more than half of the world population will be facing water-based vulnerability.[3] Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of freshwater is consumed by agriculture.[4]

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1 Types of water 2 Chemical and physical properties 3 Distribution of water in nature o 3.1 Water in the Universe o 3.2 Water and habitable zone 4 Water on Earth o 4.1 Water cycle o 4.2 Fresh water storage o 4.3 Tides 5 Effects on life o 5.1 Aquatic life forms 6 Effects on human civilization o 6.1 Health and pollution o 6.2 Human uses  6.2.1 Agriculture  6.2.2 As a scientific standard  6.2.3 For drinking  6.2.4 As a dissolving agent or solvent  6.2.5 As a heat transfer fluid  6.2.6 Extinguishing fires  6.2.7 Chemical uses  6.2.8 Recreation  6.2.9 Water industry  6.2.10 Industrial applications  6.2.11 Food processing 7 Water politics and water crisis 8 Religion, philosophy, and literature 9 See also 10 References 11 Further reading o 11.1 Water as a natural resource

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12 External links

Types of water

Liquid water in motion Water can appear in three states; it is one of the very few substances to be found naturally in all three states on earth.[citation needed] Water takes many different forms on Earth: water vapor and clouds in the sky; seawater and rarely icebergs in the ocean; glaciers and rivers in the mountains; and the liquid in aquifers in the ground. Water can dissolve many different substances, giving it different tastes and odors. In fact, humans and other animals have developed senses which are, to a degree, able to evaluate the potability of water, avoiding water that is too salty or putrid. Humans also tend to prefer cold water to lukewarm; cold water is likely to contain fewer microbes. The taste advertised in spring water or mineral water derives from the minerals dissolved in it, as pure H2O is tasteless. As such, purity in spring and mineral water refers to purity from toxins, pollutants, and microbes. Different names are given to water's various forms:

Snowflakes by Wilson Bentley, 1902 •

according to state o solid - ice o liquid - water o gaseous - water vapor

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according to meteorology: o hydrometeor  precipitation

precipitation according to moves • vertical (falling) precipitation o rain o freezing rain o drizzle o freezing drizzle o snow o snow pellets o snow grains o ice pellets o frozen rain o hail o ice crystals • horizontal (seated) precipitation o dew o hoarfrost o atmospheric icing o

glaze ice

precipitation according to state • liquid precipitation o rain o freezing rain o drizzle o freezing drizzle o dew • solid precipitation o snow o snow pellets o snow grains o ice pellets o frozen rain o hail o ice crystals o hoarfrost o atmospheric icing o glaze ice • mixed precipitation o

in temperatures around 0 °C

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levitating particles  clouds  fog  mist o ascending particles (drifted by wind)  spindrift  stirred snow according to occurrence o groundwater o meltwater o meteoric water o connate water o fresh water o surface water o mineral water – contains much minerals o brackish water o dead water – strange phenomenon which can occur when a layer of fresh or brackish water rests on top of denser salt water, without the two layers mixing. It is dangerous for ship traveling. o seawater o brine according to uses o tap water o bottled water o drinking water or potable water – useful for everyday drinking, without fouling, it contains balanced minerals that are not harmful to health (see below) o purified water, laboratory-grade, analytical-grade or reagent-grade water – water which has been highly purified for specific uses in science or engineering. Often broadly classified as o

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Type I, Type II, or Type III, this category of water includes, but is not limited to the following:  distilled water  double distilled water  deionized water •

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according to other features o soft water – contains less minerals o hard water – from underground, contains more minerals o distilled water, double distilled water, deionized water - contains no minerals o Water of crystallization — water incorporated into crystalline structures o Hydrates — water bound into other chemical substances o heavy water – made from Water heavy atoms of hydrogen deuterium. It is in nature in normal water in very low Water is a necessary solvent for all known life, and concentration. It was used in an abundant compound on the earth's surface. construction of first nuclear reactors. Information and properties o tritiated water Common name water according to microbiology IUPAC name oxidane o drinking water aqua, dihydrogen monoxide, o wastewater Alternative names hydrogen hydroxide, (more) o stormwater or surface water according to religion o holy water

Chemical and physical properties Main article: Water (molecule)

Molecular formula

H2O[citation needed]

CAS number

7732-18-5

InChI

InChI=1/H2O/h1H2

Molar mass

18.0153 g/mol

Density and phase

0.998 g/cm³ (liquid at 20 °C, 1 atm) 0.917 g/cm³ (solid at 0 °C, 1 atm)

Melting point

0 °C (273.15 K) (32 °F)

Boiling point

99.974 °C (373.124 K) (211.95 °F)

Specific heat capacity

4.184 J/(g·K) (liquid at 20 °C) 74.539 J/ (mol·K) (liquid at 25 °C)

Supplementary data page Disclaimer and references

model of hydrogen bonds between molecules of water

Impact from a water drop causes an upward "rebound" jet surrounded by circular capillary waves.

Dew drops adhering to a spider web capillary action of water compared to mercury Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. The major chemical and physical properties of water are: •

Water is a tasteless, odorless liquid at ambient temperature and pressure. The color of water and ice is, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas.[5]

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Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly absorbed.

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Since oxygen has a higher electronegativity than hydrogen, water is a polar molecule. The oxygen has a slight negative charge while the hydrogens have a slight positive charge giving the article a strong effective dipole moment. The interactions between the different dipoles of each molecule cause a net attraction force associated with water's high amount of surface tension.

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Another very important force that causes the water molecules to stick to one another is the hydrogen bond.[6]

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The boiling point of water (and all other liquids) is directly related to the barometric pressure. For example, on the top of Mt. Everest water boils at about 68 °C (154 °F), compared to 100 °C (212 °F) at sea level. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid.

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Water has a high surface tension caused by the weak interactions, (Van Der Waals Force) between water molecules because it is polar. The apparent elasticity caused by surface tension drives the capillary waves.

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Water also has high adhesion properties because of its polar nature.

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Capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.

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Water is a very strong solvent, referred to as the universal solvent, dissolving many types of substances. Substances that will mix well and dissolve in water, e.g. salts, sugars, acids, alkalis, and some gases: especially oxygen, carbon dioxide (carbonation), are known as "hydrophilic" (water-loving) substances, while those that do not mix well with water (e.g. fats and oils), are known as "hydrophobic" (water-fearing) substances.

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All the major components in cells (proteins, DNA and polysaccharides) are also dissolved in water.

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Pure water has a low electrical conductivity, but this increases significantly upon solvation of a small amount of ionic material such as sodium chloride.

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Water has the second highest specific heat capacity of any known chemical compound, after ammonia, as well as a high heat of vaporization (40.65 kJ mol−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature.

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The maximum density of water is at 3.98 °C (39.16 °F).[7] Water becomes even less dense upon freezing, expanding 9%. This causes an unusual phenomenon: ice floats upon water, and so water organisms can live inside a partly frozen pond because the water on the bottom has a temperature of around 4 °C (39 °F).

ADR label for transporting goods dangerously reactive with water •

Water is miscible with many liquids, for example ethanol, in all proportions, forming a single homogeneous liquid. On the other hand, water and most oils are immiscible usually forming layers according to increasing density from the top. As a gas, water vapor is completely miscible with air.

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Water forms an azeotrope with many other solvents.

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Water can be split by electrolysis into hydrogen and oxygen.

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As an oxide of hydrogen, water is formed when hydrogen or hydrogen-containing compounds burn or react with oxygen or oxygen-containing compounds. Water is not a fuel, it is an endproduct of the combustion of hydrogen. The energy required to split water into hydrogen and oxygen by electrolysis or any other means is greater than the energy released when the hydrogen and oxygen recombine.[8]

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Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides. Being a flammable gas, the hydrogen given off is dangerous and the reaction of water with the more electropositive of these elements is violently explosive.

Distribution of water in nature

Water in the Universe Much of the universe's water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.[9] Water has been detected in interstellar clouds within our galaxy, the Milky Way. It is believed[who?] that water exists in abundance in other galaxies too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems, such as ours. Water vapor is present on: • • • • • • • •

Mercury - 3.4% in the atmosphere, and large amounts of water in Mercury's exosphere[10] Venus - 0.002% in the atmosphere Earth - trace in the atmosphere (varies with climate) Mars - 0.03% in the atmosphere Jupiter - 0.0004% in the atmosphere Saturn - in ices only Enceladus (moon of Saturn) - 91% in the atmosphere exoplanets known as HD 189733 b[11] and HD 209458 b.[12]

Liquid water is present on: • •

Earth - 71% of surface Moon - small amounts of water have been found (in 2008) in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971.[13]

Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus. Probably some liquid water is on Europa. Water ice is present on: • • • • •

Earth - mainly on ice sheets polar ice caps on Mars Titan Europa Enceladus

Probability or possibility of distribution of water ice is at: lunar ice on the Moon, Ceres (dwarf planet), Tethys (moon). Ice is probably in internal structure of Uranus, Neptune, and Pluto and on comets.

Water and habitable zone

The Solar System along center row range of possible habitable zones of varying size stars. The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth is vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if

it were slightly closer to or further from the Sun (about 5%, or about 8 million kilometres), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.[14] Earth's mass allows gravity to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a greenhouse effect which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would cause temperature extremes preventing the accumulation of water except in polar ice caps (as on Mars). It has been proposed that life itself may maintain the conditions that have allowed its continued existence. The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis. The state of water also depends on a planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity. There are various theories about origin of water on Earth.

Water on Earth Main articles: Hydrology and Water distribution on Earth

Water covers 71% of the Earth's surface; the oceans contain 97.2% of the Earth's water. The Antarctic ice sheet, which contains 90% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo. Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology. The collective mass of water found on, under, and over the surface of a planet is called hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1 360 000 000 km³ (326 000 000 mi³). Of this volume: • • • • •

1 320 000 000 km³ (316 900 000 mi³ or 97.2%) is in the oceans. 25 000 000 km³ (6 000 000 mi³ or 1.8%) is in glaciers, ice caps and ice sheets. 13 000 000 km³ (3,000,000 mi³ or 0.9%) is groundwater. 250 000 km³ (60,000 mi³ or 0.02%) is fresh water in lakes, inland seas, and rivers. 13 000 km³ (3,100 mi³ or 0.001%) is atmospheric water vapor at any given time.

Groundwater and fresh water are useful or potentially useful to humans as water resources. Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers. The most important geological processes caused by water are: chemical weathering, water erosion, water sediment transport and sedimentation, mudflows, ice erosion and sedimentation by glacier.

Water cycle Main article: Water cycle Water cycle. The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes: • • •

evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air. precipitation, from water vapor condensing from the air and falling to earth or ocean. runoff from the land usually reaching the sea.

Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year. Precipitation, at a rate of 107 Tt per year over land, has several forms: most commonly rain, snow, and hail, with some contribution from fog and dew. Condensed water in the air may also refract sunlight to produce rainbows. Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh water storage Main article: Water resources Some runoff water is trapped for periods, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is

important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply.

Tides

High tide (left) and low tide (right). Main article: Tide Tides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

Effects on life

An oasis is an isolated water source with vegetation in desert

Some of the biodiversity of a coral reef

Water reflecting light in Crissy Field From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc. Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO2 in the process (cellular respiration). Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7. Stomach acid (HCl) is useful to digestion. However, its corrosive effect on the esophagus during reflux can temporarily be neutralized by ingestion of a base such as aluminum hydroxide to produce the neutral molecules water and the salt aluminum chloride. Human biochemistry that involves enzymes usually performs optimally around a biologically neutral pH of 7.4. For example a cell of Escherichia coli contains 70% of water, a human body 60–70%, plant body up to 90% and the body of an adult jellyfish is made up of 94–98% water.

Aquatic life forms Main articles: Hydrobiology and Aquatic plant

Some marine diatoms - a key phytoplankton group

Earth's waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land. Plants such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain. Aquatic animals must obtain oxygen to survive, and they do so in various ways. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Smaller life forms are able to absorb oxygen through their skin.

Effects on human civilization

Water Fountain Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development.

Health and pollution

Environmental Scientist sampling water. Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by filtration or distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). Sometimes the term safe water is applied to potable water of a lower quality threshold (i.e., it is used effectively for nutrition in humans that have weak access to water cleaning processes, and does more good than harm). Water that is not fit for drinking but is not harmful for humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes

called safe water, or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1–2 ppm of chlorine not yet reacted with impurities for bathing water). This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently, about 1 billion people around the world routinely drink unhealthy water. Most countries accepted the goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitation during the 2003 G8 Evian summit.[15] Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water and over 1 billion without access to adequate sanitation. Poor water quality and bad sanitation are deadly; some 5 million deaths a year are caused by polluted drinking water. The World Health Organization estimates that safe water could prevent 1.4 million child deaths from diarrhea each year.[16] Water, however, is not a finite resource, but rather re-circulated as potable water in precipitation in quantities many degrees of magnitude higher than human consumption. Therefore, it is the relatively small quantity of water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers around every 1 to 10 years), that is a non-renewable resource, and it is, rather, the distribution of potable and irrigation water which is scarce, rather than the actual amount of it that exists on the earth. Waterpoor countries use importation of goods as the primary method of importing water (to leave enough for local human consumption), since the manufacturing process uses around 10 to 100 times products' masses in water. In the developing world, 90% of all wastewater still goes untreated into local rivers and streams.[17] Some 50 countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 of these extract more water annually than is recharged through their natural water cycles.[18] The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

Human uses Agriculture

Irrigation of field crops The most important use of water in agriculture is for an irrigation and irrigation is key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countries.[19] As a scientific standard On 7 April 1795, the gram was defined in France to be equal to "the absolute weight of a volume of pure water equal to a cube of one hundredth of a meter, and to the temperature of the melting ice."[20] For practical purposes though, a metallic reference standard was required, one thousand times more massive, the kilogram. Work was therefore commissioned to determine precisely how massive one liter of water

was. In spite of the fact that the decreed definition of the gram specified water at 0 °C—a highly stable temperature point—the scientists chose to redefine the standard and to perform their measurements at the most stable density point: the temperature at which water reaches maximum density, which was measured at the time as 4 °C.[21] The Kelvin temperature scale of the SI system is based on the triple point of water, defined as exactly 273.16 K or 0.01 °C. The scale is a more accurate development of the Celsius temperature scale, which is defined by the boiling point (100 °C) and melting point (0 °C) of water. Natural water consists mainly of the isotopes hydrogen-1 and oxygen-16, but there is also small quantity of heavier isotopes such as hydrogen-2 (deuterium). The amount of deuterium oxides or heavy water is very small, but it still affects the properties of water. Water from rivers and lakes tends to contain less deuterium than seawater. Therefore, a standard water called Vienna Standard Mean Ocean Water is defined as the standard water. For drinking

A young girl drinking bottled water. Main article: Drinking water The human body is anywhere from 55% to 78% water depending on body size.[22] To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though most advocates agree that 6–7 glasses of water (approximately 2 litres) daily is the minimum to maintain proper hydration.[23] Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather.[24] For those who have healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising, however, putting them at risk of water intoxication (hyperhydration), which can be fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source.[25] There are other myths such as the effect of water on weight loss and constipation that have been dispelled.[26] An original recommendation for water intake in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods."[27] The latest dietary reference intake report by the United States National Research Council in general recommended (including food sources): 2.7 liters of water total for women and 3.7 liters for men.[28] Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. According to the Institute of Medicine—who recommend that, on average, women consume 2.2 litres and men 3.0 litres—this is recommended to be 2.4 litres (approx. 9 cups) for pregnant women and 3 litres (approx. 12.5 cups) for breastfeeding women since an especially large amount of fluid is lost during nursing.[29] Also noted is that normally, about 20 percent of water

intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through urine and feces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well.

Hazard symbol for No drinking water Humans require water that does not contain too many impurities. Common impurities include metal salts and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes.[30] The single largest freshwater resource suitable for drinking is Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean. As a dissolving agent or solvent Dissolving (or suspending) is used to wash everyday items such as the human body, clothes, floors, cars, food, and pets. Also, human wastes are carried by water in the sewage system. Its use as a cleaning solvent consumes most of water in industrialized countries. Water can facilitate the chemical processing of wastewater. An aqueous environment can be favourable to the breakdown of pollutants, due to the ability to gain an homogenous solution that is pumpable and flexible to treat. Aerobic treatment can be used by applying oxygen or air to a solution reduce the reactivity of substances within it. Water also facilitates biological processing of waste that have been dissolved within it. Microorganisms that live within water can access dissolved wastes and can feed upon them breaking them down into less polluting substances. Reedbeds and anaerobic digesters are both examples of biological systems that are particularly suited to the treatment of effluents. Typically from both chemical and biological treatment of wastes, there is often a solid residue or cake that is left over from the treatment process. Depending upon its constituent parts, this 'cake' may be dried and spread on land as a fertilizer if it has beneficial properties, or alternatively disposed of in landfill or incinerated. As a heat transfer fluid

Ice used for cooling. Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive. In almost all electric power plants, water is the coolant, which vaporizes and drives steam turbines to drive generators. In the nuclear industry, water can also be used as a neutron moderator. In a pressurized water reactor, water is both a coolant and a moderator. This provides a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down. Extinguishing fires

Water is used for fighting wildfires. Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, water cannot be used to fight fires of electric equipment, because impure water is electrically conductive, or of oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid. Use of water in fire fighting should also take into account the hazards of a steam explosion, which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas. The power of such explosions was seen in the Chernobyl disaster, although the water involved did not come from fire-fighting at that time but the reactor's own water cooling system. A steam explosion occurred when the extreme over-heating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result of reaction between steam and hot zirconium. Chemical uses Organic reactions are usually quenched with water or a water solution of a suitable acid, base or buffer. Water is generally effective in removing inorganic salts. In inorganic reactions, water is a common solvent. In organic reactions, it is usually not used as a reaction solvent, because it does not dissolve the reactants well and is amphoteric (acidic and basic) and nucleophilic. Nevertheless, these properties are sometimes desirable. Also, acceleration of Diels-Alder reactions by water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently. Recreation

Main article: Water sport (recreation) Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. Lakesides, beaches and waterparks are popular places for people to go to relax and enjoy recreation. Many find the sound of flowing water to be calming, too. Some keep fish and other life in aquariums or ponds for show, fun, and companionship. Humans also use water for snow sports i.e. skiing or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns or water balloons. They may also make fountains and use water in their public or private decorations. Water industry Main articles: Water industry and :Category:Water supply and sanitation by country

A water-carrier in India,1882. In many places where running water is not available, water has to be transported by people. The water industry provides drinking water and wastewater services (including sewage treatment) to households and industry.

A manual water pump in China

water purification facility

Water used in landscaping. Water supply facilities includes for example water wells cisterns for rainwater harvesting, water supply network, water purification facilities, water tanks, water towers, water pipes including old aqueducts. Atmospheric water generator is in development. Drinking water is often collected at springs, extracted from artificial borings in the ground, or wells. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Other water sources are rainwater and river or lake water. This surface water, however, must be purified for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material, while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant ocean or seawater is a more expensive solution used in coastal arid climates. The distribution of drinking water is done through municipal water systems or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource and to finance the boring of wells or the construction of dams and reservoirs. Reducing waste by using drinking water only for human consumption is another option. In some cities such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources. Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as externalities for which the market cannot account. Thus other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population victim of this pollution. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable. Wastewater facilities are sewers and wastewater treatment plants. Another way to remove pollution from surface runoff water is bioswale. Industrial applications Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes, from where it flows down.

Three Gorges Dam is the largest hydro-electric power station Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in the cooling of machinery to prevent over-heating, or prevent saw blades from over-heating. Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge. Food processing

Water can be used to cook foods such as noodles. Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products. Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) raises the boiling point of water by 0.52 °C, and one mole of salt raises the boiling point by 1.04 °C while lowering the freezing point of water in a similar way.[31] Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food.[32] Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water.[31] Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity.[32] Not only does microbial growth affect the safety of food but also the preservation and shelf life of food. Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness.[31] Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains.[vague] [31] The hardness of water may be altered or treated by using a chemical ion exchange system. The hardness of water also

affects its pH balance which plays a critical role in food processing. For example, hard water prevents successful production of clear beverages. Water hardness also affects sanitation; with increasing hardness, there is a loss of effectiveness for its use as a sanitizer.[31] Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam. While cooking water is used for dishwashing too.

Water politics and water crisis Main articles: Water politics and Water crisis See also: Water resources, Water law, and Water right Water politics is politics affected by water and water resources. Because of overpopulation, mass consumption, misuse, and water pollution, the availability of drinking water per capita is inadequate and shrinking as of the year 2006. For this reason, water is a strategic resource in the globe and an important element in many political conflicts. It causes health impacts and damage to biodiversity. The serious worldwide water situation is called water crisis. UNESCO's World Water Development Report (WWDR, 2003) from its World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from waterborne diseases (related to the consumption of contaminated water) or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of sewage disposal; see toilet. To halve, by 2015, the proportion of people without sustainable access to safe drinking water is one of the Millennium Development Goals. Fresh water — now more precious than ever in our history for its extensive use in agriculture, high-tech manufacturing, and energy production — is increasingly receiving attention as a resource requiring better water management and sustainable use. Organizations concerned in water protection include International Water Association (IWA), WaterAid, Water 1st, American Water Resources Association. Water related conventions are United Nations Convention to Combat Desertification (UNCCD), International Convention for the Prevention of Pollution from Ships, United Nations Convention on the Law of the Sea and Ramsar Convention. World Day for Water takes place at March 22 and World Ocean Day at June 8. Water used in the production of a good or service is virtual water.

Religion, philosophy, and literature

A Hindu ablution as practiced in Tamil Nadu Water is considered a purifier in most religions. Major faiths that incorporate ritual washing (ablution) include Christianity, Hinduism, Rastafarianism, Islam, Shinto, Taoism, and Judaism. Immersion (or aspersion or affusion) of a person in water is a central sacrament of Christianity (where it is called baptism); it is also a part of the practice of other religions, including Judaism (mikvah) and Sikhism (Amrit Sanskar). In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the five daily prayers can be done in most cases after completing washing certain parts of the body using clean water (wudu). In Shinto, water is used in almost all rituals to cleanse a person or an area (e.g., in the ritual of misogi). Water is mentioned in the Bible 442 times in the New International Version and 363 times in the King James Version: 2 Peter 3:5(b) states, "The earth was formed out of water and by water" (NIV). Some faiths use water especially prepared for religious purposes (holy water in some Christian denominations, Amrita in Sikhism and Hinduism). Many religions also consider particular sources or bodies of water to be sacred or at least auspicious; examples include Lourdes in Roman Catholicism, the Jordan River (at least symbolically) in some Christian churches, the Zamzam Well in Islam and the River Ganges (among many others) in Hinduism. Water is often believed to have spiritual powers. In Celtic mythology, Sulis is the local goddess of thermal springs; in Hinduism, the Ganges is also personified as a goddess, while Saraswati have been referred to as goddess in Vedas. Also water is one of the "panch-tatva"s (basic 5 elements, others including fire, earth, space, air). Alternatively, gods can be patrons of particular springs, rivers, or lakes: for example in Greek and Roman mythology, Peneus was a river god, one of the three thousand Oceanids. In Islam, not only does water give life, but every life is itself made of water: "We made from water every living thing".[33] The Ancient Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the ylem, or basic substance of the universe. Water was considered cold and moist. In the theory of the four bodily humors, water was associated with phlegm. Water was also one of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal. Water also plays an important role in literature as a symbol of purification. Examples include the critical importance of a river in As I Lay Dying by William Faulkner and the drowning of Ophelia in Hamlet. Water portal

Sherlock Holmes held that "From a drop of water, a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other."[34]

See also Sustainable development portal • •

Water Pasteurization Indicator Dihydrogen monoxide hoax

References

Exploration From Wikipedia, the free encyclopedia

Jump to: navigation, search "Explorer" redirects here. For other uses, see Explorer (disambiguation).

Stereotypical explorer Kazimierz Nowak Exploration is the act of searching or traveling a terrain for the purpose of discovery, e.g. of unknown people, including space (space exploration), for oil, gas, coal, ores, caves, water (Mineral exploration, or prospecting), or information. Although exploration has existed as long as human beings, its peak is seen as being during the Age of Discovery when European navigators traveled around the world discovering new lands and cultures.

Contents [hide] • • • • •

1 Other uses 2 Notable Female Explorers 3 Notable Male Explorers 4 See also 5 References

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[edit] Other uses

The term may also be used metaphorically, for example persons may speak of exploring the internet, sexuality, etc. In scientific research, exploration is one of three purposes of research (the other two being description and explanation). Exploration is the attempt to develop an initial, rough understanding of some phenomenon.

[edit] Notable Female Explorers

Photo of Explorer Kira Salak in Iran[1] •

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Sacagawea; accompanied and assisted Meriwether Lewis and William Clark on the Lewis and Clark Expedition (1804–1806), the first American overland expedition to the Pacific coast and back. Lady Mary Wortley Montagu (b. 26 May 1689 – d. 21 August 1762) Explored Turkey. Isabella Bird (b. October 15, 1831 – d. October 7, 1904) She was the first woman inducted into the Royal Geographical Society; she travelled extensively, exploring the Far East, Central Asia, and the American West. Mary Kingsley (b. October 13, 1862 – d. June 3, 1900) Explored the Upper Ogawe River in Gabon and journeyed alone into unknown regions of the Congo jungle. Freya Stark (b. 31 Jan 1893, Paris France - d. 9 May 1993) She was not only one of the first Western women to travel through the Arabian deserts (Hadhramaut); she often traveled solo into areas where few Europeans, let alone women, had ever been. Robyn Davidson (b. September 6, 1950) She was the first person to make a solo crossing of the Australian Outback by camel; she also explored the remote desert regions of India.[2]

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Valentina Tereshkova, one of the first people in space; first female cosmonaut. Kira Salak (b. September 4, 1971) A National Geographic Emerging Explorer[3], Salak was the first woman to cross the island of New Guinea; she was also the first person in the world to kayak 600 miles alone to Timbuktu. Salak has done solo exploration to regions such as Borneo, Libya, Iran, Madagascar, and the Democratic Republic of the Congo.[1]

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Pytheas (380 – c. 310 BC) - Greek explorer. First to circumnavigate Great Britain and to explore Germany. Reached Thule, most commonly thought to be the Shetland Islands or Iceland. Brendan the Navigator (c. 484 – c. 577) - Irish monk, allegedly found Iceland and America in the 6th century. Dicuil (born in the 8th century) - Irish monk and geographer, author of "De mensura Orbis terrae". The Papar - Irish monks who lived in Iceland, 8th-9th centuries, before the Vikings. Ahmad ibn Fadlan - 10th century Iraqi explorer. Erik the Red (950 - 1003) - Norwegian Viking explorer. After being cast out from Iceland, he sailed to Greenland and settled there. Leif Ericson (980 - 1020) - Icelandic explorer. Believed to have been the first European to land in North America. Friar Julian (traveled in 1235) - Hungarian Dominican friar. Marco Polo (1254 - 1324) - Venetian explorer.[4] Ibn Battuta (1304 - 1377) - Moroccan explorer.[5] James of Ireland (fl.1316 - 1330) - Irish companion of Odoric of Pordenone. Simon FitzSimon (fl.1323), Irish author of a itenerum through Egypt and the Holy Land. Zheng He (1371 - 1433) - Chinese explorer. João Fernandes Lavrador (1445? - 1501) - Portuguese explorer. First European reaching Labrador/Newfoundland. Fernandes charted the coasts of Southwestern Greenland and of adjacent Northeastern North America around 1498. In 1501, Fernandes set sail again in discovery of lands and was never heard from again. John Cabot (c. 1450 - 1499) - Italian explorer for England. Discovered Newfoundland and claimed it for the Kingdom of England. Bartolomeu Dias (c. 1450 - 1500) - Portuguese explorer. He sailed from Portugal and reached the Cape of Good Hope. Christopher Columbus (1451 - 1506) - Genoese explorer for Spain. Sailed in 1492 and discovered the "New World" of the Americas. Amerigo Vespucci (c. 1454 - 1512) - Italian explorer for Spain. Sailed in 1499 and 1502. He explored the east coast of South America. Juan Ponce de León (c. 1460 - 1521) - Spanish explorer. He explored Florida while attempting to locate a Fountain of Youth. Piri Reis (c. 1465/1470 – 1554/1555) - Ottoman explorer. Pedro Álvares Cabral (c. 1467 - c. 1520) - Portuguese explorer, generally regarded as the European discoverer of Brazil. Vasco da Gama (c. 1469 - 1524) - Portuguese explorer. The first European to sail from Europe to India by rounding the Cape of Good Hope. Vasco Núñez de Balboa (c. 1475 - 1519) - Spanish explorer. The first European to cross the Isthmus of Panama and view the Pacific ocean from American shores. Francisco Pizarro (c. 1475 - 1541) - Spanish explorer. Conquered the Inca Empire. Juan Sebastián Elcano (1476 - 1526) - Spanish explorer. Completed the first circumnavigation of the globe in a single expedition after its captain, Magellan, was killed.

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Ferdinand Magellan (1480 - 1521) - Portuguese explorer for Spain. Initiated the first circumnavigation of the globe in a single expedition. Sailed through Strait of Magellan and named Pacific Ocean. Died in the Philippines after claiming them for Spain. Giovanni da Verrazzano (c. 1485 - 1528) - Italian explorer for France. Explored the northeast coast of America, from about present day South Carolina to Newfoundland. Hernán Cortés (1485 - 1545) - Spanish explorer. Conquered the Aztec Empire for Spain. Jacques Cartier (1491 – 1557) - French explorer. Discovered Canada. Hernando de Soto (c. 1496 - 1542) - Spanish explorer. Explored Florida, mainly northwest Florida, and discovered the Mississippi River. Francisco Vásquez de Coronado (c. 1510 - 1554) - Spanish explorer. Searched for the Seven Cities of Gold and discovered the Grand Canyon in the process. Francisco de Orellana (1511-1546) - Spanish explorer in 1541-42 sails the length of the Amazon River. Pedro Sarmiento de Gamboa (1532 - 1592) Spanish explorer of the Pacific. Sir Francis Drake (c. 1540 - 1596) - English explorer. The first English captain to sail around the world and survive. Alvaro de Mendaña de Neyra 1541-1596 - Spanish explorer of the Pacific. Willem Barentsz 1550-1597 Dutch navigator and explorer, leader of early expeditions to the far north. Pedro Fernandes de Queirós 1565-1614 Portuguese navigator. Explored the Pacific in the service of the Spanish Crown. Luis Váez de Torres (c. 1565- ) Spanish or Portuguese navigator. Explored the Pacific in the service of the Spanish Crown. Henry Hudson (1570 - 1611) - English explorer. Explored much of the North Atlantic, including Labrador, the coast of Greenland, and Hudson Bay. Presumed dead in a 1611 mutiny of his own crew. António de Andrade (1580 - 1634) - Portuguese explorer. First European reaching Tibet. His reports were the only account of the Tibet culture and geography until the second half of the 18th century. Abel Tasman (1603 - 1659) - Dutch explorer. Discovered New Zealand and Tasmania. Evliya Çelebi (1611 - 1682) - Ottoman traveller. Vitus Bering (1681 - 1741) - Danish explorer. Explored the Siberian Far East and Alaska and claimed it for Russia. James Cook (1728 - 1779) - British naval captain. Explored much of the Pacific including New Zealand, Australia and Hawaii. Jean François La Pérouse (1741–1788) was a French Navy officer and explorer whose expedition vanished in Oceania Alessandro Malaspina (1754-1810) - Italian explorer. Explored the Pacific and the west coast of North America in the service of Spanish Crown Alexander MacKenzie (1764-1820) Scottish-Canadian explorer who in 1789, looking for the Northwest Passage, followed the river now named after him to the Arctic Ocean and then in 1793 crossed the Rockies and reached the Pacific in 1793, thus beating Lewis and Clark by 12 years. Alexander von Humboldt (1769 - 1859) - German explorer and scientist whose work was foundational to the field of biogeography. Mungo Park (1771-1806) Was the first Westerner to discover the Niger River; he was the first Western explorer to reach Timbuktu, though he didn't live to share his discovery with the world. Captain Meriwether Lewis (1774 - 1809) - American explorer and field scientist who led the Lewis and Clark Expedition into the Louisiana Purchase and the Pacific Northwest in 1804-1806. Edward Sabine(October 14, 1788 – May 26, 1883) - Irish participant in the Ross and Perry Arctic expeditions. Thomas Coulter (1793 – 1843) - Irish botanist and explorer of Mexico and Arizona.

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Charles Wilkes (April 3, 1798 – February 8, 1877) - American naval officer and explorer who commanded the United States Exploring Expedition George Fletcher Moore (10 December 1798 – 30 December 1886) - early Irish explorer of Australia Pierre-Jean De Smet (1801 - 1873) - Belgian missionary and explorer in North America. David Livingstone (1813 – 1873) - Scottish missionary and explorer in central Africa. He was the first European to see Victoria Falls, which he named in honour of Queen Victoria. Robert O'Hara Burke (1821 – c.28 June 1861) - Irish leader of the Burke and Wills expedition. Henry Morton Stanley (1841 – 1904) - Welsh journalist and explorer in central Africa best remembered for his search for David Livingstone, and upon finding him saying: "Dr. Livingstone, I presume?" George Comer (1858 - 1937) - American polar explorer. The Comer Strait of northern Southampton Island and the Gallinula comeri flightless bird of Gough Island were named in his honor. Fridtjof Nansen (1861 - 1930) - Norwegian explorer, scientist and diplomat. He was the first to cross the Greenland ice cap in 1888 and drifted across the Arctic ocean with the Fram in 18931896 where he attempted to reach the North Pole with Hjalmar Johansen. Otto Sverdrup (1854 - 1930) - Norwegian explorer. Joined Fridtjof Nansen acoss Greenland in 1888 and captain on the Fram on the polar drift in 1893-1896 and the 2nd Fram expedition in 1898-1902. Mapped the Northernmost part of Canada in 1898-1902. Roald Amundsen (1872 - 1928) - Norwegian explorer. He led the first successful Antarctic expedition between 1910 and 1912. He was also the first ever person to successfully traverse the North West Passage. Ernest Shackleton (1874 - 1922) - Irish Explorer, noted for his ill-fated Endurance expedition to Antarctica. Hiram Bingham III (1875 - 1956) - U.S. Senator from Connecticut and explorer best known for uncovering Machu Picchu. Robert Bartlett (1875 - 1946) - Newfoundland captain. Led over 40 expeditions to the Arctic, more than anyone before or since. Was the first to sail north of 88° N latitude. Tom Crean (20 July 1877 – 27 July 1938) - Irish Antarctic explorer. Knud Rasmussen (1879 - 1933) - Greenlandic polar explorer and anthropologist. Rasmussen was the first to cross the Northwest Passage via dog sled. Auguste Piccard (1884-1962), physicist, balloonist, hydronaut- Explored the stratosphere and the deep sea Ahmed Pasha Hassanein (1889 - 1946) - Egyptian explorer, diplomat, one of two non-European winners of Gold Medal of Royal Geographical Society in 1924, King's chamberlain, fencing participant to 1924 Olympics, photographer, author and discoverer of Jebel Uweinat, and writer of "The Lost Oases" book in three languages. Colonel Noel Andrew Croft (1906 - 1998) - held the record for the longest self-sustaining journey across the Arctic in the 1930s for 60 years. Sir Edmund Percival Hillary (1919–2008) - New Zealand explorer, together with Tenzing Norgay, the first to climb Mount Everest on May 29, 1953. Yuri Gagarin (March 9, 1934 – March 27, 1968) - Soviet cosmonaut who on April 12, 1961 became the first man in space and the first human to orbit Earth. Neil Armstrong (born August 5, 1930) - American astronaut - First human being to set foot on the Moon on July 20, 1969. Robert Ballard - born in 1942) - undersea explorer; discovered the shipwreck of the RMS Titanic'. Dr. E. Lee Spence (1947- ) - undersea explorer and pioneer underwater archaeologist: discovered numerous shipwrecks including H.L. Hunley the first submarine in history to sink an enemy ship; and the Georgiana, said to have been the most powerful Confederate cruiser. Reinhold Messner (born September 17, 1944) - Italian mountaineer, first man to climb all the 14 peaks higher than 8,000 meters.

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Frank Cole (1954 - 2000) - Canadian explorer, filmmaker and life extensionist. He was the first North American to cross the Sahara desert in 1990 alone on camel. He was murdered by bandits during a second crossing in 2000. Jeremy Curl (born 1982) - British explorer; the youngest to traverse the Sahara on foot and the first non African to cross the desolate Tanezrouft area of the Sahara by camel. Michael Asher (1953-) - British explorer. In 1986-7 Michael Asher and his wife, Italian-born photographer and Arabist, Mariantonietta Peru, made the first ever west-east crossing of the Sahara desert by camel and on foot.

In 2001 Jon Muir and his dog, Seraphine, began an odyssey to cross Australia on foot, from the coast of South Australia to the north coast of Queensland. 128 days and 2,500 kilometers later, on the point of starvation and exhaustion, Jon arrived in Burketown, becoming the first person to walk solo and unassisted across the continent of Australia.

[edit] See also • • • • • • • • • • • • • • • •

Exploration of Asia European exploration of Africa Expeditions List of explorers List of maritime explorers BSES (British Schools Exploring Society) Expeditions Age of Exploration Cave exploration Confluence exploration/hunting Desert exploration Global Vision International Polar exploration Space exploration Urban exploration Mineral exploration Explorer (newspaper)

[edit] References

Woman From Wikipedia, the free encyclopedia

Jump to: navigation, search "Women" redirects here. For other uses, see Woman (disambiguation). For other uses, see Women (disambiguation). Truth, 1870 by Jules Joseph Lefebvre A woman is an adult female human. The term woman (irregular plural: women) usually is used for an adult, with the term girl being the usual term for a female child or adolescent. However, the term woman

is also sometimes used to identify a female human, regardless of age, as in phrases such as "Women's rights".

Contents [hide]

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1 Etymology 2 Age and terminology 3 Biology and sex 4 Culture and gender roles 5 Education and employment o 5.1 OECD countries 6 Further reading 7 See also 8 References

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Etymology Symbol of the planet/Roman goddess Venus, also used to indicate the female sex among animals that reproduce sexually The English term "Man" (from Proto-Germanic mannaz "man, person") and words derived therefrom can designate any or even all of the human race regardless of their sex or age. This is indeed the oldest usage of "Man" in English. It derives from Proto-Indo-European *mánu- 'man, human', cognate to Sanskrit manu, Old Church Slavonic mǫžĭ, 'man', 'husband'. In Old English the words wer and wyf (also wæpman and wifman) were what was used to refer to "a man" and "a woman" respectively, and "Man" was gender-neutral. In Middle English man displaced wer as term for "male human", whilst wifman (which eventually evolved into woman) was retained for "female human". ("Wif" also evolved into the word "wife".) "Man" does continue to carry its original sense of "Human" however, resulting in an asymmetry sometimes criticized as sexist.[1] (See also womyn.) A very common Indo-European root for woman, *gwen-, is the source of English queen (Old English cwēn primarily meant woman, highborn or not; this is still the case in Danish, with the modern spelling kvinde), as well as gynaecology (from Greek gynē), banshee fairy woman (from Irish bean woman, sí fairy) and zenana (from Persian zan). The Latin fēmina, whence female, is likely from the root in fellāre (to suck), referring to breastfeeding.[2][3] The symbol for the planet Venus is the sign also used in biology for the female sex. It is a stylized representation of the goddess Venus's hand mirror or an abstract symbol for the goddess: a circle with a small equilateral cross underneath (Unicode: ♀). The Venus symbol also represented femininity, and in ancient alchemy stood for copper. Alchemists constructed the symbol from a circle (representing spirit) above an equilateral cross (representing matter).

Age and terminology

A young woman Womanhood is the period in a female's life after she has transitioned from girlhood, at least physically, having passed the age of menarche. Many cultures have rites of passage to symbolize a woman's coming of age, such as confirmation in some branches of Christianity, bat mitzvah in Judaism, or even just the custom of a special celebration for a certain birthday (generally between 12 and 21). Currently in the English language there is no commonly-used word for a woman who has passed menopause, although historically a woman in the third part of her life was known as a crone, which was originally not a pejorative term. The three ages of woman were historically known as "maiden, matron, and crone" and are sometimes quoted as "maiden, mother and crone". This could perhaps be rendered in modern English as "little girl", "woman of reproductive age" and "older lady". The word woman can be used generally, to mean any female human, or specifically, to mean an adult female human as contrasted with girl. The word girl originally meant "young person of either sex" in English; it was only around the beginning of the 16th century that it came to mean specifically a female child. Nowadays girl sometimes is used colloquially to refer to a young or unmarried woman. During the early 1970s feminists challenged such use, and use of the word to refer to a fully grown woman may cause offence. In particular, previously common terms such as office girl are no longer used. Conversely, in certain cultures which link family honor with female virginity, the word girl is still used to refer to a never-married woman; in this sense it is used in a fashion roughly analogous to the obsolete English maid or maiden. Referring to an unmarried female as a woman may, in such a culture, imply that she is sexually experienced, which would be an insult to her family. In some settings, the use of girl to refer to an adult female is a common practice (such as girls' night out), even among some elderly women. In this sense, girl may be considered to be the analogue to the British word bloke for a man, although it again fails to meet the parallel status as an adult. Gal aside, some feminists cite this lack of an informal yet respectful term for women as misogynistic; they regard nonparallel usages, such as men and girls, as sexist. There are various words used to refer to the quality of being a woman. The term "womanhood" merely means the state of being a woman, having passed the menarche; "femininity" is used to refer to a set of supposedly typical female qualities associated with a certain attitude to gender roles; "womanliness" is like "femininity", but is usually associated with a different view of gender roles; "femaleness" is a general

term, but is often used as shorthand for "human femaleness"; "distaff" is an archaic adjective derived from women's conventional role as a spinner, now used only as a deliberate archaism; "muliebrity" is a "neologism" (derived from the Latin) meant to provide a female counterpart of "virility", but used very loosely, sometimes to mean merely "womanhood", sometimes "femininity", and sometimes even as a collective term for women.

Biology and sex The human female reproductive system In terms of biology, the female sex organs are involved in the reproductive system, whereas the secondary sex characteristics are involved in nurturing children or, in some cultures, attracting a mate. The ovaries, in addition to their regulatory function producing hormones, produce female gametes called eggs which, when fertilized by male gametes (sperm), form new genetic individuals. The uterus is an organ with tissue to protect and nurture the developing fetus and muscle to expel it when giving birth. The vagina is used in copulation and birthing (although the word vagina is often colloquially and incorrectly used for the vulva or external female genitalia, which also includes the labia, the clitoris, and the female urethra). The breast evolved from the sweat gland to produce milk, a nutritious secretion that is the most distinctive characteristic of mammals, along with live birth. In mature women, the breast is generally more prominent than in most other mammals; this prominence, not necessary for milk production, is probably at least partially the result of sexual selection. (For other ways in which men commonly differ physically from women, see Man.)

Spectral karyotype of a human female. The XX combination is formed at the 23rd week of gestation. National Human Genome Resource Institute An imbalance of maternal hormonal levels and some chemicals (or drugs) may alter the secondary sexual characteristics of fetuses. Most women have the karyotype 46,XX, but around one in a thousand will be 47,XXX, and one in 2500 will be 45,X. This contrasts with the typical male karotype of 46,XY; thus, the X and Y chromosomes are known as female and male, respectively. Unlike the Y chromosome, the X can come from either the mother or the father, thus genetic studies which focus on the female line use mitochondrial DNA. Biological factors are not sufficient determinants of whether a person considers themselves a woman or is considered a woman. Intersex individuals, who have mixed physical and/or genetic features, may use other criteria in making a clear determination. There are also transgender or transsexual women, who were born or physically assigned as male at birth, but identify as women; there are varying social, legal, and individual definitions with regard to these issues. (See transwoman.)

Although fewer females than males are born (the ratio is around 1:1.05), due to a longer life expectancy there are only 81 men aged 60 or over for every 100 women of the same age, and among the oldest populations, there are only 53 men for every 100 women.[citation needed] Women typically have a longer life expectancy than men.[citation needed] This is due to a combination of factors: genetics (redundant and varied genes present on sex chromosomes in women); sociology (such as not being expected in most countries to perform military service); health-impacting choices (such as suicide or the use of cigarettes, and alcohol); the presence of the female hormone estrogen, which has a cardioprotective effect in premenopausal women; and the effect of high levels of androgens in men. Out of the total human population, there are 101.3 men for every 100 women (source: 2001 World Almanac). Most women go through menarche and are then able to become pregnant and bear children.[4] This generally requires internal fertilization of her eggs with the sperm of a man through sexual intercourse, though artificial insemination or the surgical implantation of an existing embryo is also possible (see reproductive technology). The study of female reproduction and reproductive organs is called gynaecology. Women generally reach menopause in their late 40s or early 50s, at which point their ovaries cease producing estrogen[citation needed] and they can no longer become pregnant. To a large extent, women suffer from the same illnesses as men.[citation needed] However, there are some diseases that primarily affect women, such as lupus. Also, there are some sex-related illnesses that are found more frequently or exclusively in women, e.g., breast cancer, cervical cancer, or ovarian cancer. Women and men may have different symptoms of an illness and may also respond differently to medical treatment. This area of medical research is studied by gender-based medicine. During early fetal development, embryos of both sexes appear gender-neutral; the release of hormones is what changes physical appearance male or female. As in other cases without two sexes, such as species that reproduce asexually, the gender-neutral appearance is closer to female than to male.

Culture and gender roles Main article: Gender role This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (November 2006)

A woman weaving. Textile work has historically been a female occupation in some cultures.

Turkish women smoking hookah, 1910

Women pilots In many prehistoric cultures, women assumed a particular cultural role. In hunter-gatherer societies, women were generally the gatherers of plant foods, small animal foods, fish, and learned to use dairy products, while men hunted meat from large animals. In more recent history, the gender roles of women have changed greatly. Traditionally, middle-class women were typically involved in domestic tasks emphasizing child care, and did not enter paid employment. For poorer women, especially working class women, this often remained an ideal,[specify] as economic necessity compelled them to seek employment outside the home. The occupations that were available to them were, however, lower in prestige and pay than those available to men. As changes in the labor market for women came about, availability of employment changed from only "dirty", long houred factory jobs to "cleaner", more respectable office jobs where more education was demanded, women's participation in the U.S. labor force rose from 6% in 1900 to 23% in 1923. These shifts in the labor force led to changes in the attitudes of women at work, allowing for the "quiet" revolution which resulted in women becoming more career and education oriented. Women's movements advocate equality of opportunity with men, and equal rights irrespective of gender. Through a combination of economic changes and the efforts of the feminist movement,[specify] in recent decades women in most societies now have access to careers beyond the traditional homemaker. Many observers, including feminist groups, maintain that women in industry and commerce face glass ceilings. These changes and struggles are among the foci of the academic field of women's studies.[citation needed]

Education and employment

OECD countries •

Education

The gender gap in OECD countries has been reduced over the last 30 years. Younger women today are far more likely to have completed a tertiary qualification: in 19 of the 30 OECD countries, more than twice as many women aged 25 to 34 have completed tertiary education than women aged 55 to 64 do. In 21 of 27 OECD countries with comparable data, the number of women graduating from university-level programmes is equal to or exceeds that of men. 15-year-old girls tend to show much higher expectations for their careers than boys of the same age.[5] While women account for more than half of university graduates in several OECD countries, they receive only 30% of tertiary degrees granted in science and engineering fields, and women account for only 25% to 35% of researchers in most OECD countries.[6]

Further reading • • • • • •

Chafe, William H., "The American Woman: Her Changing Social, Economic, And Political Roles, 1920-1970", Oxford University Press, 1972. ISBN 0-19-501785-4 Roget’s II: The New Thesaurus, (Boston: Houghton Mifflin, 2003 3rd edition) ISBN 0-618-254145 McWhorter, John. 'The Uses of Ugliness', The New Republic Online, January 31, 2002. Retrieved May 11, 2005 ["bitch" as an affectionate term] McWhorter, John. Authentically Black: Essays for the Black Silent Majority (New York: Gotham, 2003) ISBN 1-59240-001-9 [casual use of "bitch" in ebonics] Routledge international encyclopedia of women, 4 vls., ed. by Cheris Kramarae and Dale Spender, Routledge 2000 Women in world history : a biographical encyclopedia, 17 vls., ed. by Anne Commire, Waterford, Conn. [etc.] : Yorkin Publ. [etc.], 1999 - 2002

See also • • • • • • •

Childbirth Feminism Gender and sexuality studies Gender differences Lady Lesbian Lists of women

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Matriarchy

References

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New Woman Obstetrics Representation of women in Ancient Greek theatre Sexism Timeline of women's suffrage Women in science Women in religion

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Women's suffrage

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Adult From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the human developmental stage. For the adult insect stage, see Imago. For the band, see ADULT.. For the 2008 British film by Noel Clarke see Adulthood (film). The term adult has three distinct meanings. It indicates a grown person. It may also mean a plant or animal that has reached full growth, or one who is legally of age; as opposed to a minor.

Adulthood can be defined in biology, psychological adult development, law, personal character, or social status. These different aspects of adulthood are often inconsistent and contradictory. A person may be biologically an adult, and have adult behavioral but still be treated as a child if they are under the legal age of majority. Conversely one may legally be an adult but possess none of the maturity and responsibility that define adult character. Coming of age is the event; passing a series of tests to demonstrate the child is prepared for adulthood; or reaching a specified age, sometimes in conjunction with demonstrating preparation. Most modern societies determine legal adulthood based on reaching a legally-specified age without requiring a demonstration of physical maturity or preparation for adulthood. Adult, especially in the sense of entertainment or other diversion, frequently appears as a euphemism for being related to sexual behaviour. Adult toys and adult games—which terms refer to games and toys that are closely related to sex, do not generally refer only to games or toys with which children are simply incompatible—are in this category, for example. This usage does indicate unsuitability for children, but the more immediate meaning is closer to "not legal for children." Adult education, however, does simply mean education for adults, especially for those past the usual age for either high school or university. Some propose that moving into adulthood involves an emotional structuring of denial. This process becomes necessary to cope with one's own behavior, especially in uncomfortable situations, and also the behavior of others.

Contents [hide] • • • • •

1 Biological adulthood 2 Legal adulthood 3 Personal characteristics 4 See also 5 References

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6 External links

[edit] Biological adulthood Adulthood is generally understood as the time when physical maturation is complete. This usually occurs anywhere between 19 and 21. They reach their maximum height and secondary sex characteristics in the form of body hair and maturing of the larynx, as well as ovulating monthly for women. Natural sleep patterns change in adulthood, as adults typically require less sleep than during adolescence and childhood. At this point, such individuals usually become independent and therefore able to care for others as well as themselves. There are exceptions to this rule however.

[edit] Legal adulthood Main article: Age of majority Legally it means that one can engage in a contract. The same or a different minimum age may be applicable to, for example, parents losing parenting rights and duties regarding the person concerned, parents losing financial responsibility, marriage, voting, having a job, being a soldier, buying/possessing

firearms (if legal at all), driving, traveling abroad, involvement with alcoholic beverages (if legal at all), smoking, sex, gambling (both lottery and casino) being a prostitute or a client of a prostitute (if legal at all), being a model or actor in pornography, etc. Admission of a young person to a place may be restricted because of danger for that person, and/or because of the risk that the young person causes damage (for example, at an exhibition of fragile items). One can distinguish the legality of acts of a young person, and of enabling a young person to carry out that act, by selling, renting out, showing, permitting entrance, participating, etc. There may be distinction between commercially and socially enabling. Sometimes there is the requirement of supervision by a legal guardian, or just by an adult. Sometimes there is no requirement, but just a recommendation. With regard to pornography one can distinguish: • • • • •

being allowed inside an adult establishment being allowed to purchase pornography being allowed to possess pornography another person being allowed to sell, rent out, or show the young person pornography, see disseminating pornography to a minor being a model or actor in pornography: rules for the young person, and for other people, regarding production, possession, etc. (see child pornography)

With regard to films with violence, etc.: •

another person being allowed to sell, rent out, or show the young person the film, a cinema being allowed to let the young person (under 17) enter

The legal definition of entering adulthood usually varies between ages 15–21, depending on the region in question. Some cultures in Africa define adult at age 13. According to Jewish tradition, adulthood is reached at age 13 (the age of the Bar Mitzvah), for Jewish boys, for example, were expected to demonstrate preparation for adulthood by learning the Torah and other Jewish practices. The Christian Bible and Jewish scripture has no age requirement for adulthood or marrying, which includes engaging in sexual activity. According to The Disappearance of Childhood by Neil Postman, the Christian Church of the Middle Ages considered the age of accountability, when a person could be tried and even executed as an adult, to be age 7 . In most of the world, including the United States, parts of the United Kingdom (England, Northern Ireland, Wales), India and China, the legal adult age is 18, with some exceptions: 1. Iran and Singapore (21) 2. Indonesia and Japan (20) 3. South Korea & British Columbia, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Nunavut, Yukon Territory in Canada (19) 4. the United Kingdom: Scotland (16)

[edit] Personal characteristics There are some qualities that symbolize adultness in most cultures. There is not always a correlation between the qualities and the physical age of the person. The adult character comprises:

Self-control - restraint, emotional control. Stability - stable personality, strength. Independence - ability to self-regulate. Seriousness - ability to deal with life in a serious manner. Responsibility - accountability, commitment and reliability. Method/Tact - ability to think ahead and plan for the future, patience. Endurance - ability and willingness to cope with difficulties that present themselves. Experience - breadth of mind, understanding. Objectivity - perspective and realism. Decision making capability - as all of the above correspond to making proper decisions. Priorities - Ability to determine what is necessary at that place and time.

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[edit] See also Adolescence Adult development Child Watershed (television) Age of consent Manhood Womanhood Motion picture rating system Adultism

• • • • • • • • •

[edit] References [edit] External links Table 8. Age of Independence US and UK legal age guide.

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This article has multiple issues. Please help improve the article or discuss these issues on the talk page. •

It does not cite any references or sources. Please help improve it by citing reliable sources. Tagged since December 2007.

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It may require restructuring to meet Wikipedia's quality standards. Tagged since October 2007.

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It may contain original research or unverifiable claims. Tagged since October 2007. [hide]

v•d•e

Human development: biological - psychological - Overview table Pre- and Prenatal development • Pre- and perinatal psychology perinatal Infancy Infant and child development (stages) • Infancy Childhood

Child development (stages) Toddlerhood • Preadolescence

Adolescence Youth development • Puberty Adulthood Early adulthood • Middle adulthood • Late adulthood • Ageing & Senescence John Bowlby-attachment • Urie Bronfenbrenner-ecological systems • Erik Theorists-theories Erikson-psychosocial • Sigmund Freud-psychosexual • Lawrence Kohlbergmoral • Jean Piaget-cognitive • Lev Vygotsky-cultural-historical Retrieved from "http://en.wikipedia.org/wiki/Adult" Categories: Biology | Human development Hidden categories: Articles lacking sources from December 2007 | All articles lacking sources | Cleanup from October 2007 | All pages needing cleanup | Articles that may contain original research since October 2007

Human sexual behavior From Wikipedia, the free encyclopedia

(Redirected from Sexual behaviour) Jump to: navigation, search This article is about sexual practices (i.e., physical sex). For broader aspects of sexual behavior see human sexuality. This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (December 2008)

Close relationships

Affinity · Attachment · Bonding Boyfriend · Casual · Cohabitation

Compersion · Concubinage Consort · Courtesan · Courtship Divorce · Domestic partnership Dower / Dowry / Bride price Family · Friendship · Girlfriend Husband · Infatuation · Intimacy Jealousy · Limerence · Love Kinship · Marriage · Monogamy Psychology of monogamy Non-monogamy Passion · Pederasty Platonic love · Polyamory Polyfidelity · Polygamy Relationship abuse Relationship breakup · Romance Romantic friendship · Separation Sexuality · Same-sex relationship Significant other · Soulmate Teen dating violence · Wedding Widowhood · Wife v•d•e

Human sexual behavior or different human sexual practices encompass a wide range of activities such as strategies to find or attract partners (mating and display behaviour), interactions between individuals, physical or emotional intimacy, and sexual contact. Some cultures find only sexual contact within marriage acceptable; however, extramarital sexual activity still takes place within such cultures. Unprotected sex poses a risk in unwanted pregnancy or sexually transmitted diseases. In some areas, sexual abuse of individuals is prohibited by law and considered against the norms of society.

Contents [hide] •

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1 Aspects of human sexual behavior o 1.1 Sexual pleasure o 1.2 Cultural aspects o 1.3 Social norms and rules o 1.4 Frequency of sexual activity 2 Safety and ancillary issues 3 Legal issues related to sexual behavior o 3.1 Sodomy and same sex laws 4 Child sexuality 5 Footnotes

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6 Further reading

[edit] Aspects of human sexual behavior [edit] Sexual pleasure Sexual pleasure is pleasure derived from any kind of sexual activity, most commonly masturbation and sexual intercourse. Though orgasm (sexual climax) is generally known, sexual pleasure includes erotic pleasure during foreplay, and pleasure due to fetish or BDSM.[1][2]

[edit] Cultural aspects As with other behaviors, human intelligence and complex societies have produced among the most complicated sexual behaviors of any animal. Most people experiment with a range of sexual activities during their lives, though they tend to engage in only a few of these regularly. Most people enjoy some sexual activities. However, most societies have defined some sexual activities as inappropriate (wrong person, wrong activity, wrong place, etc.) Some people enjoy many different sexual activities, while others avoid sexual activities altogether for religious or other reasons (see chastity, sexual abstinence). Some societies and religions view sex as appropriate only within marriage.

Coitus, tacuinum sanitatis casanatensis (XIV century)

[edit] Social norms and rules Main article: Social norm Human sexual behavior, like many other kinds of activity engaged in by human beings, is generally governed by social rules that are culturally specific and vary widely. These social rules are referred to as sexual morality (what can and can not be done by society's rules) and sexual norms (what is and is not expected). In the United States, attitudes towards premarital sex and the use of contraceptives correlate to religious beliefs and political affiliation.[3] Sexual ethics, morals, and norms relate to issues including deception/honesty, legality, fidelity and consent. Some activities, known as sex crimes, are illegal in some jurisdictions, including those conducted between (or among) consenting and competent adults (examples include sodomy law and adult-adult incest).

Some people engage in various sexual activities as a business transaction. When this involves having sex with, or performing certain actual sexual acts for another person, it is called prostitution. Other aspects of the adult industry include (for example) telephone sex operators, strip clubs, pornography and the like. Nearly all developed societies consider it a serious crime to force someone to engage in sexual behavior or to engage in sexual behavior with someone who does not consent. This is called sexual assault, and if sexual penetration occurs it is called rape, the most serious kind of sexual assault. The details of this distinction may vary among different legal jurisdictions. Also, precisely what constitutes effective consent to have sex varies from culture to culture and is frequently debated. Laws regulating the minimum age at which a person can consent to have sex (age of consent) are frequently the subject of political and moral debate[citation needed], as is adolescent sexual behavior in general. Additionally, many societies have forced marriage, so consent does not really figure in to the equation of a sex crime.[citation needed] It is possible to engage in sexual activity without a partner, primarily through masturbation and/or sexual fantasy.

[edit] Frequency of sexual activity The frequency of sexual intercourse might range from zero (sexual abstinence) to 15 or 20 times a week.[4] It is generally recognized that postmenopausal women experience declines in frequency of sexual intercourse.[5]. The average frequency of sexual intercourse for married couples is 2 to 3 times a week (in America). [6]

[edit] Safety and ancillary issues Main article: Safe sex There are four main areas of risk in sexual activity, namely: • • • •

choosing to trust a partner who is physically at risk sexually transmitted disease unwanted pregnancy seeking or engaging in an activity which is legally or culturally disapproved

These risks are raised by any condition (temporary or permanent) which impairs one's judgement, such as excess alcohol or drugs, or emotional states such as loneliness, depression or euphoria. Carefully considered activity can greatly reduce all of these issues. Sexual behaviors that involve contact with the bodily fluids of another person entail risk of transmission of sexually transmitted disease. Safe sex practices try to avoid this. These techniques are often seen as less necessary for those in committed relationships with persons known to be free of disease; see fluid bonding. Due to health concerns arising from HIV/AIDS, chlamydia, syphilis, gonorrhea, HPV and other sexually transmitted infections, some people may want potential sex partners to be tested for STDs before engaging in sex. Sexual behaviors that involve the contact of semen with the vagina or vulva may result in pregnancy. To prevent pregnancy, many people employ a variety of birth control measures. The most popular methods of prevention are condoms, spermicides, hormonal contraception, and sterilization.

[edit] Legal issues related to sexual behavior Main articles: Paraphilia#Legal views and Sex and the law

[edit] Sodomy and same sex laws Various forms of same-sex sexual activity have been prohibited under law in many areas at different times in history. In 2003, the Lawrence v Texas United States Supreme Court decision overturned all such laws in the US.[7] Usually, though not always, such laws are termed sodomy laws, but also include issues such as age of consent laws, "decency" laws, and so forth. Laws prohibiting same-sex sexuality have varied widely throughout history, varying by culture, religious and social taboos and customs, etc. Often such laws are targeted or applied differently based on sex as well. For example, laws against same-sex sexual behavior in the United Kingdom during the reign of Queen Victoria, sodomy or "buggery" laws were aimed specifically at male same-sex sexual activity and did not target or even address female homosexuality. A well known example of such laws applied in relatively modern times can be found in the life story of Alan Turing.

[edit] Child sexuality Main article: Child sexuality Child sexuality examines sexual feelings, behaviors, and developments in children. Children are naturally curious about their bodies and sexual functions — they wonder where babies come from, they notice anatomical differences between males and females, and many engage in genital play (often mistaken for masturbation). In the past, children were often assumed to be sexually "pure", having no sexuality until later development. Sigmund Freud was one of the first researchers to take child sexuality seriously. While his ideas, such as psychosexual development and the Oedipus conflict, have been rejected or labeled obsolete, acknowledging the existence of child sexuality was a milestone. Alfred Kinsey also examined child sexuality in his Kinsey Reports. Child sexual abuse is a form of child abuse in which a child is abused for the sexual gratification of someone else; child abuse is also a legal umbrella term describing criminal and civil offenses in which an adult engages in sexual activity with a minor or exploits a minor for the purpose of sexual gratification.[8] [9][10][11] In addition to direct sexual contact, child sexual abuse also occurs when an adult exposes their genitals to a child, asks or pressures a child to engage in sexual activities, displays pornography to a child, or uses a child to produce child pornography.[12][10][9] The American Psychiatric Association states that "children cannot consent to sexual activity with adults",[13][14] and condemns any such action: "An adult who engages in sexual activity with a child is performing a criminal and immoral act which never can be considered normal or socially acceptable behavior."[13] Nonetheless, transgenerational sexual contact is present in a large number of societies[15] under the form of handling of toddlers's genitals and also, with older kids, for the purpose of sexual training[16]. Possible effects of child sexual abuse include depression, post-traumatic stress disorder, anxiety, propensity to re-victimization in adulthood, and physical injury to the child, among other problems.[17][18] [19][20][21] Sexual abuse by a family member is a form of incest, and can result in more serious and long-term psychological trauma, especially in the case of parental incest.[22]

[edit] Footnotes

World view From Wikipedia, the free encyclopedia

(Redirected from World outlook) Jump to: navigation, search It has been suggested that this article or section be merged with Contemplation. (Discuss) A comprehensive world view (or worldview) is a term calqued from the German word Weltanschauung ([ˈvɛlt.ʔanˌʃaʊ.ʊŋ] (help·info)) Welt is the German word for "world", and Anschauung is the German word for "view" or "outlook." It is a concept fundamental to German philosophy and epistemology and refers to a wide world perception. Additionally, it refers to the framework of ideas and beliefs through which an individual interprets the world and interacts with it. The German word is also in wide use in English, as well as the translated form world outlook or world view.

Contents [hide]

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1 Origins of world views o 1.1 Worldview and linguistics o 1.2 Weltanschauung and cognitive philosophy o 1.3 Worldview and folk-epics o 1.4 Construction of worldviews 2 Impact of worldviews o 2.1 Structural aspects o 2.2 Other aspects 3 Worldviews in religion and philosophy 4 See also 5 References

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6 External links

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[edit] Origins of world views [edit] Worldview and linguistics A worldview describes a consistent (to a varying degree) and integral sense of existence and provides a framework for generating, sustaining, and applying knowledge.

The linguistic relativity hypothesis of Benjamin Lee Whorf describes how the syntactic-semantic structure of a language becomes an underlying structure for the Weltanschauung of a people through the organization of the causal perception of the world and the linguistic categorization of entities. As linguistic categorization emerges as a representation of worldview and causality, it further modifies social perception and thereby leads to a continual interaction between language and perception.[1] The theory, or rather hypothesis, was well received in the late 1940s, but declined in prominence after a decade. In the 1990s, new research gave further support for the linguistic relativity theory, in the works of Stephen Levinson and his team at the Max Planck institute for Psycholinguistics at Nijmegen, The Netherlands [2]. The theory has also gained attention through the work of Lera Boroditsky at Stanford University.

[edit] Weltanschauung and cognitive philosophy One of the most important concepts in cognitive philosophy and generative sciences is the German concept of ‘Weltanschauung’. This expression refers to the "wide worldview" or "wide world perception" of a people, family, or person. The Weltanschauung of a people originates from the unique world experience of a people, which they experience over several millennia. The language of a people reflects the Weltanschauung of that people in the form of its syntactic structures and untranslatable connotations and its denotations. If it were possible to draw a map of the world on the basis of Weltanschauung, it would probably be seen to cross political borders — Weltanschauung is the product of political borders and common experiences of a people from a geographical region,[3] environmental-climatic conditions, the economic resources available, socio-cultural systems, and the linguistic family.[3] (The work of the population geneticist Luigi Luca Cavalli-Sforza aims to show the gene-linguistic co-evolution of people). If the Sapir-Whorf hypothesis is correct, the worldview map of the world would be similar to the linguistic map of the world. However, it would also almost coincide with a map of the world drawn on the basis of music across people.[4]

[edit] Worldview and folk-epics As natural language becomes manifestations of world perception, the literature of a people with common Weltanschauung emerges as holistic representations of the wide world perception of the people. Thus the extent and commonality between world folk-epics becomes a manifestation of the commonality and extent of a worldview. Epic poems are shared often by people across political borders and across generations. Examples of such epics include the Nibelungenlied of the Germanic-Scandinavian people, The Silappadhikaram of the South Indian people, The Gilgamesh of the Mesopotamian-Sumerian civilization and the people of the Fertile Crescent at large, The Arabian nights of the Arab world and the Sundiata epic of the Mandé people. See also: list of world folk-epic

[edit] Construction of worldviews The 'construction of integrating worldviews' begins from fragments of worldviews offered to us by the different scientific disciplines and the various systems of knowledge [5]. It is contributed to by different

perspectives that exist in the world's different cultures. This is the main topic of research at the Center Leo Apostel for Interdisciplinary Studies. It should be noted that while Apostel and his followers clearly hold that individuals can construct worldviews, other writers regard worldviews as operating at a community level, and/or in an unconscious way. For instance, if one's worldview is fixed by one's language, as according to a strong version of the Sapir-Whorf hypothesis, one would have to learn or invent a new language in order to construct a new worldview. According to Apostel, a worldview should comprise seven elements: 1. 2. 3. 4. 5. 6. 7.

An ontology, a descriptive model of the world An explanation of the world A futurology, answering the question "where are we heading?" Values, answers to ethical questions: "What should we do?" A praxeology, or methodology, or theory of action.: "How should we attain our goals?" An epistemology, or theory of knowledge. "What is true and false?" An etiology. A constructed world-view should contain an account of its own "building blocks," its origins and construction.

[edit] Impact of worldviews [edit] Structural aspects The term denotes a comprehensive set of opinions, seen as an organic unity, about the world as the medium and exercise of human existence. Weltanschauung serves as a framework for generating various dimensions of human perception and experience like knowledge, politics, economics, religion, culture, science, and ethics. For example, worldview of causality as uni-directional, cyclic, or spiral generates a framework of the world that reflects these systems of causality. A uni-directional view of causality is present in some monotheistic views of the world with a beginning and an end and a single great force with a single end (e.g., Christianity and Islam), while a cyclic worldview of causality is present in religious tradition which is cyclic and seasonal and wherein events and experiences recur in systematic patterns (e.g., Zoroastrianism, Mithraism, and Hinduism). These worldviews of causality not only underlie religious traditions but also other aspects of thought like the purpose of history, political and economic theories, and systems like democracy, authoritarianism, anarchism, capitalism, socialism, and communism. The worldview of a linear and non-linear causality generates various related/conflicting disciplines and approaches in scientific thinking. The Weltanschauung of the temporal contiguity of act and event leads to underlying diversifications like determinism vs. free will. A worldview of Freewill leads to disciplines that are governed by simple laws that remain constant and are static and empirical in scientific method, while a worldview of determinism generates disciplines that are governed with generative systems and rationalistic in scientific method. Some forms of Philosophical naturalism and materialism reject the validity of entities inaccessible to natural science. They view the scientific method as the most reliable model for building anunderstanding of the world.

[edit] Other aspects

In The Language of the Third Reich, Weltanschauungen came to designate the instinctive understanding of complex geo-political problems by the Nazis, which allowed them to act in the name of a higher ideal[6] and in accordance to their theory of the world. These acts perceived outside that unique Weltanschauung are now commonly perceived as acts of aggression, such as openly beginning invasions, twisting facts, and violating human rights.

[edit] Worldviews in religion and philosophy Various writers suggest that religious or philosophical belief-systems should be seen as worldviews rather than a set of individual hypotheses or theories. The Japanese Philosopher Nishida Kitaro wrote extensively on "the Religious Worldview" in exploring the philosophical significance of Eastern religions[7]. According to Neo-Calvinist David Naugle's Worldview: The History of a Concept "Conceiving of Christianity as a worldview has been one of the most significant developments in the recent history of the church."[8] The Christian thinker James W. Sire defines a worldview as "a commitment, a fundamental orientation of the heart, that can be expressed as a story or in a set of presuppositions (assumptions which may be true, partially true, or entirely false) which we hold (consciously or subconsciously, consistently or inconsistently) about the basic construction of reality, and that provides the foundation on which we live and move and have our being." He suggests that "we should all think in terms of worldviews, that is, with a consciousness not only of our own way of thought but also that of other people, so that we can first understand and then genuinely communicate with others in our pluralistic society."[9] The Rev. Professor Keith Ward bases his discussion of the rationality of religious belief in Is Religion Dangerous? on a consideration of religious and non-religious worldviews.[10] The philosophical importance of Worldviews became increasingly clear during the 20th Century for a number of reasons, such as increasing contact between cultures, and the failure of some aspects of the Enlightenment project, such as the rationalist project of attaining all truth by reason alone. Mathematical logic showed that fundamental choices of axioms were essential in deductive reasoning[11] and that, even having chosen axioms not everything that was true in a given logical system could be proven[12]. Some philosophers believe the problems extend to "the inconsistencies and failures which plagued the Enlightenment attempt to identify universal moral and rational principles"[13]; although Enlightenment principles such as universal suffrage and (the universal declaration of) human rights are accepted, if not taken for granted, by many.[14] A worldview can be considered as comprising a number of basic beliefs which are philosophically equivalent to the axioms of the worldview considered as a logical theory. These basic beliefs cannot, by definition, be proven (in the logical sense) within the worldview precisely because they are axioms, and are typically argued from rather than argued for[15]. However their coherence can be explored philosophically and logically, and if two different worldviews have sufficient common beliefs it may be possible to have a constructive dialogue between them[16]. On the other hand, if different worldviews are held to be basically incommensurate and irreconcilable, then the situation is one of cultural relativism and would therefore incur the standard criticisms from philosophical realists. [17] [18][19]. Additionally, religious believers might not wish to see their beliefs relativized into something that is only "true for them"[20][21]. Subjective logic is a belief reasoning formalism where beliefs explicitly are subjectively held by individuals but where a consensus between different worldviews can be achieved[22]. A third alternative is that the Worldview approach is only a methodological relativism, that it is a suspension judgment about the truth of various belief systems, but not a declaration that there is no global truth. For instance, the religious philosopher Ninian Smart begins his Worldviews: Crosscultural Explorations of Human Beliefs with "Exploring Religions and Analysing Worldviews" and argues for "the

neutral, dispassionate study of different religious and secular systems - a process I call worldview analysis."[23]

[edit] See also • • • • • • • • •

Belief Belief networks Contemplation Cultural identity Ideology Life stance Metaphysics Ontology Paradigm

• • • • • • • • •

Philosophy Point of view Reality Reality tunnel Religion Scientism Scientific modeling Social reality Socially constructed reality

•

Perspective

•

Subjective logic

[edit] References

House From Wikipedia, the free encyclopedia

Jump to: navigation, search This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2008) The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

For the television series, see House (TV series). For the governmental body, see house of representatives; see also legislature. For other uses, see House (disambiguation).

A ranch style house in Salinas, California

Example of an early Victorian "Gingerbread House" in the United States, built in 1855 House generally refers to a shelter or building that is a dwelling or place for habitation by human beings. The term includes many kinds of dwellings ranging from rudimentary huts of nomadic tribes to high-rise apartment buildings.[1] However, the word can also be used as a verb ("to house"), and can have adjectival formations as well. In some contexts, "house" may mean the same as dwelling, residence, home, abode, accommodation, housing, lodging, among other meanings. The social unit that lives in a house is known as a household. Most commonly, a household is a family unit of some kind, though households can be other social groups, such as single persons, or groups of unrelated individuals. Settled agrarian and industrial societies are composed of household units living permanently in housing of various types, according to a variety of forms of land tenure. English-speaking people generally call any building they routinely occupy "home". Many people leave their houses during the day for work and recreation but typically return to them to sleep or for other activities.

Contents [hide]

• •

1 History 2 Types o 2.1 Structure o 2.2 Shape o 2.3 Function 3 Inside the house o 3.1 Layout o 3.2 Parts 4 Construction o 4.1 Energy-efficiency o 4.2 Earthquake protection 5 Legal issues o 5.1 United Kingdom o 5.2 United States and Canada 6 Identifying houses 7 Animal houses 8 Shelter 9 Houses and symbolism o 9.1 Heraldry 10 See also 11 References

•

12 External links

• •

•

•

•

• • • •

[edit] History The oldest house in the world is approximately from 10,000 B.C and was made of mammoth bones, found at Mezhirich near Kiev in Ukraine. It was probably covered with mammoth hides. The house was discovered in 1965 by a farmer digging a new basement six feet below the ground.[2] Architect Norbert Schoenauer, in his book 6,000 Years of Housing, identifies three major categories of types of housing: the "Pre-Urban" house, the "Oriental Urban" house, and the "Occidental Urban" house. Types of Pre-Urban houses include temporary dwellings such as the Inuit igloo, semi-permanent dwellings such as the pueblo, and permanent dwellings such as the New England homestead. "Oriental Urban" houses include houses of the ancient Greeks and Romans, and traditional urban houses in China, India, and Islamic cities. "Occidental Urban" houses include medieval urban houses, the Renaissance town house, and the houses, tenements and apartments of the 19th and 20th centuries.[1]

[edit] Types See also: List of house types

[edit] Structure

A suburban neighborhood in San Jose, California.

Wood houses in the Swiss Alps. The developed world in general features three basic types of house that have their own ground-level entry and private open space, and usually on a separately titled parcel of land: • • •

Single-family detached houses - free-standing on all sides. Semi-detached houses (duplexes) - houses that are attached, usually to only one other house via a party wall. Terraced house (UK) also known as a row house or townhouse - attached to other houses, possibly in a row, each separated by a party wall.

In addition, there are various forms of attached housing where a number of dwelling units are co-located within the same structure, which share a ground-level entry and may or may not have any private open space, such as apartments (a.k.a. flats) of various scales. Another type of housing is movable, such as houseboats, caravans, and trailer homes. In the United Kingdom, 27% of the population live in terraced houses and 32% in semi-detached houses, as of 2002. In the United States as of 2000, 61.4% of people live in detached houses and 5.6% in semidetached houses, 26% in row houses or apartments, and 7% in mobile homes.

[edit] Shape Archaeologists have a particular interest in house shape: they see the transition over time from round huts to rectangular houses as a significant advance in optimizing the use of space, and associate it with the growth of the idea of a personal area (see personal space).[citation needed]

[edit] Function

A Nalukettu traditional Kerala house in India Some houses transcend the basic functionality of providing "a roof over one's head" or of serving as a family "hearth and home". When a house becomes a display-case for wealth and/or fashion and/or conspicuous consumption, we may speak of a "great house". The residence of a feudal lord or of a ruler may require defensive structures and thus turn into a fort or a castle. The house of a monarch may come to house courtiers and officers as well as the royal family: this sort of house may become a palace. Moreover, in time the lord or monarch may wish to retreat to a more personal or simple space such as a villa, a hunting lodge or a dacha. Compare the popularity of the holiday house or cottage, also known as a crib. In contrast to a relatively upper class or modern trend to ownership of multiple houses, much of human history shows the importance of multi-purpose houses. Thus the house long served as the traditional place of work (the original cottage industry site or "in-house" small-scale manufacturing workshop) or of commerce (featuring, for example, a ground floor "shop-front" shop or counter or office, with living space above). During the Industrial Revolution there was a separation of manufacturing and banking from the house, though to this day some shopkeepers continue (or have returned) to live "over the shop".

[edit] Inside the house [edit] Layout

House in Brazil. Main article: House plan Ideally, architects of houses design rooms to meet the needs of the people who will live in the house. Such designing, known as "interior design", has become a popular subject in universities. Feng shui, originally a Chinese method of situating houses according to such factors as sunlight and micro-climates, has recently expanded its scope to address the design of interior spaces with a view to promoting harmonious effects on the people living inside the house. Feng shui can also mean the 'aura' in or around a dwelling. Compare the real-estate sales concept of "indoor-outdoor flow". The square footage of a house in the United States reports the area of "living space", excluding the garage and other non-living spaces. The "square meters" figure of a house in Europe reports the area of the walls enclosing the home, and thus includes any attached garage and non-living spaces.[citations needed]

[edit] Parts It has been suggested that this article or section be merged into Room. (Discuss)

Floor plan of a "foursquare" house Many houses have several rooms with specialized functions. These may include a living/eating area, a sleeping area, and (if suitable facilities and services exist) washing and lavatory areas. In traditional agriculture-oriented societies, domestic animals such as chickens or larger livestock (like cattle) often share part of the house with human beings. Most conventional modern houses will at least contain a bedroom, bathroom, kitchen (or kitchen area), and a living room. A typical "foursquare house" (as pictured) occurred commonly in the early history of the United States of America, with a staircase in the center of the house, surrounded by four rooms, and connected to other sections of the house (including in more recent eras a garage). The names of parts of a house often echo the names of parts of other buildings, but could typically include:

• • • • •

atrium attic alcove basement / cellar bathroom (in various senses of the word) • •

• • • •

bath / shower toilet

bedroom (or nursery, for infants or small children) conservatory dining room family room or den

• • •

kitchen larder laundry room library living room loft lounge nook office or study pantry parlour recreation room / rumpus room / television room shrines to serve the religious functions associated with a family stairwell sunroom storage room / box room

•

workshop

• • • • • • • • • • • • •

Fireplace (for warmth during winter; generally not found in warmer climates) •

• • • •

foyer front room (in various senses of the phrase) garage hallway/passage

•

hearth - often an important symbolic focus of family togetherness See also: Room (architecture)

[edit] Construction

The structure of the house (under demolition). This house is constructed from bricks and wood and was later covered by insulating panels. The roof construction is also seen. In the United States, modern house-construction techniques include light-frame construction (in areas with access to supplies of wood) and adobe or sometimes rammed-earth construction (in arid regions with scarce wood-resources). Some areas use brick almost exclusively, and quarried stone has long provided walling. To some extent, aluminum and steel have displaced some traditional building materials. Increasingly popular alternative construction materials include insulating concrete forms (foam forms filled with concrete), structural insulated panels (foam panels faced with oriented strand board or fiber cement), and light-gauge steel framing and heavy-gauge steel framing.

The Saitta House, Dyker Heights, Brooklyn, New York built in 1899 is made of and decorated in wood.[3] More generally, people often build houses out of the nearest available material, and often tradition and/or culture govern construction-materials, so whole towns, areas, counties or even states/countries may be built out of one main type of material. For example, a large fraction of American houses use wood, while most British and many European houses utilize stone or brick. In the 1900s, some house designers started using prefabrication. Sears, Roebuck & Co. first marketed their Houses by Mail to the general public in 1908. Prefab techniques became popular after World War II. First small inside rooms framing, then later, whole walls were prefabricated and carried to the construction site. The original impetus was to use the labor force inside a shelter during inclement weather. More recently builders have begun to collaborate with structural engineers who use computers and finite element analysis to design prefabricated steel-framed homes with known resistance to high wind-loads and seismic forces. These newer products provide labor savings, more consistent quality, and possibly accelerated construction processes. Lesser-used construction methods have gained (or regained) popularity in recent years. Though not in wide use, these methods frequently appeal to homeowners who may become actively involved in the construction process. They include: • • • • •

Cannabrick construction Cordwood construction Straw bale construction Geodesic domes Wattle and daub

Thermographic comparison of traditional (left) and 'passivhaus' (right) buildings

[edit] Energy-efficiency In the developed world, energy-conservation has grown in importance in house-design. Housing produces a major proportion of carbon emissions (30% of the total in the UK, for example).[citation needed] Development of a number of low-energy building types and techniques continues. They include the zeroenergy house, the passive solar house, superinsulated and houses built to the Passivhaus standard.

[edit] Earthquake protection One tool of earthquake engineering is base isolation which is increasingly used for earthquake protection. Base isolation is a collection of structural elements of a building that should substantially decouple it from the shaking ground thus protecting the building's integrity[4] and enhancing its seismic performance. This technology, which is a kind of seismic vibration control, can be applied both to a newly designed building and to seismic upgrading of existing structures.[5] Normally, excavations are made around the building and the building is separated from the foundations. Steel or reinforced concrete beams replace the connections to the foundations, while under these, the isolating pads, or base isolators, replace the material removed. While the base isolation tends to restrict transmission of the ground motion to the building, it also keeps the building positioned properly over the foundation. Careful attention to detail is required where the building interfaces with the ground, especially at entrances, stairways and ramps, to ensure sufficient relative motion of those structural elements.

[edit] Legal issues Buildings with historical importance have restrictions.

[edit] United Kingdom New houses in the UK are not covered by the Sale of Goods Act. When purchasing a new house the buyer has less legal protection than when buying a new car. New houses in the UK may be covered by a NHBC guarantee but some people feel that it would be more useful to put new houses on the same legal footing as other products.

[edit] United States and Canada In the US and Canada, many new houses are built in housing tracts, which provide homeowners a sense of "belonging" and the feeling they have "made the best use" of their money. However, these houses are often built as cheaply and quickly as possible by large builders seeking to maximize profits. Many environmental health issues are ignored or minimized in the construction of these structures. In one case in Benicia, California, a housing tract was built over an old landfill. Home buyers were never told, and only found out when some began having reactions to high levels of lead and chromium.

[edit] Identifying houses With the growth of dense settlement, humans designed ways of identifying houses and/or parcels of land. Individual houses sometimes acquire proper names; and those names may acquire in their turn considerable emotional connotations: see for example the house of Howards End or the castle of Brideshead Revisited. A more systematic and general approach to identifying houses may use various methods of house numbering.

[edit] Animal houses Humans often build "houses" for domestic or wild animals, often resembling smaller versions of human domiciles. Familiar animal houses built by humans include bird-houses, hen-houses/chicken-coops and doghouses (kennels); while housed agricultural animals more often live in barns and stables. However, human interest in building houses for animals does not stop at the domestic pet. People build bat-houses,

nesting-sites for wild ducks and other birds, bee houses, giraffe houses, kangaroo houses, worm houses, hermit crab houses, as well as shelters for many other animals.

[edit] Shelter

A modern style house in Canberra, ACT Forms of (relatively) simple shelter may include: • • • • • • • • • • • • • • • •

Bus stop Camper Chalet Cottage dugout Gazebo Hangar Houseboat hut Lean-to Log Cabin Shack Tent (see also camp) yaodong Caravan Umbrella

[edit] Houses and symbolism Houses may express the circumstances or opinions of their builders or their inhabitants. Thus a vast and elaborate house may serve as a sign of conspicuous wealth, whereas a low-profile house built of recycled materials may indicate support of energy conservation. Houses of particular historical significance (former residences of the famous, for example, or even just very old houses) may gain a protected status in town planning as examples of built heritage and/or of streetscape values. Plaques may mark such structures. House-ownership provides a common measure of prosperity in economics. Contrast the importance of house-destruction, tent dwelling and house rebuilding in the wake of many natural disasters. Peter Olshavsky's House for the Dance of Death provides a 'pataphysical variation on the house.

[edit] Heraldry

The house occurs as a rare charge in heraldry.

[edit] See also Institutions •

•

U.S. Department of Housing and Urban Development o Regulatory Barriers Clearinghouse o HUD USER Moladi

Economics • •

Affordable housing Housing bubble o United States housing bubble

Functions • •

Mixed-use development Visitability

Types • • • • • • • • • •

Home automation Hurricane proof house Earth sheltering Lodging Boarding house Lustron house Mobile home Modular home Housing in Japan Housing estate

Miscellaneous • • •

Housewarming party Domestic robot Squatting

Lists • • • • •

List of house types List of house styles List of types of lodging List of real estate topics List of famous American Houses

[edit] References

Calendar date From Wikipedia, the free encyclopedia

Jump to: navigation, search For the use of dates on Wikipedia, see Wikipedia:Manual of Style (dates and numbers) This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (August 2007) A date in a calendar is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "19 December 2008" is ten days after "9 December 2008" in the Gregorian calendar. The date of a particular event depends on the time zone in which it is observed. For example the attack on Pearl Harbor took place on December 7, 1941, in Hawaii, but on December 8 according to Japanese time. A particular day may be represented by a different date in another calendar as in the Gregorian calendar and the Julian calendar, which have been used simultaneously in different places. In most calendar systems, the date consists of three parts: the day of month, month, and the year. There may also be additional parts, such as the day of week. Years are usually counted from a particular starting point, usually called the epoch, with era referring to the particular period of time (Note the different use of the terms in geology). The most widely used epoch is a conventional birthdate of Jesus (which was established by Dionysius Exiguus in the sixth century). A date without the year part may also be referred to as a date or calendar date (such as "20 December" rather than "20 December 2008"). As such, it defines the day of an annual event, such as a birthday or Christmas on 25 December.

Contents [hide] •

1 Date format o 1.1 Little endian forms, starting with the day o 1.2 Big endian forms, starting with the year

• • •

1.3 Middle endian forms, starting with the month 1.4 Usage issues  1.4.1 dd/mm/yyyy or dd.mm.yyyy (day, month, year)  1.4.2 mm/dd/yy or mm/dd/yyyy (month, day, year)  1.4.3 yyyy-mm-dd (year, month, day)  1.4.3.1 Advantages for ordering in sequence o 1.5 Day and year only o 1.6 Week number used 2 Expressing dates in spoken English 3 See also 4 References

•

5 External links

o o

[edit] Date format Related to the classification of a day as a specific calendar date is the format used to express that date. The differing formats of dates are an example of endianness. Even for a specific calendar system, different formats are used. For example, the following formats all express the same date in the Gregorian calendar.

[edit] Little endian forms, starting with the day This sequence is common to the vast majority of the world's countries (see below for breakdown of countries by format). This date format originates from the custom of writing the date as ' the 16th day of November in the year of our Lord 2003' in religious and legal documents which at one time were the majority of documents created. The format has shortened as more and more people learned to read and write but the order of the elements has remained constant. • • • • •

16/11/2003, 16.11.2003 (using dot as separator with this sequence has been defined by DIN 5008) 16-11-2003 or 16-11-03 16th [of] November 2003 (The 'of' is included in speech, however it is considered bad practice to include it when written.) 16th November 2003 16 November 2003 16 Nov 2003

[edit] Big endian forms, starting with the year This form is consistent with the big endianness of the western decimal numbering system, progressing from the highest to the lowest order magnitude. This is a standard format in Asian countries, in Hungary and in Sweden where the most significant data item is written first followed by lesser data items. An example of this is the custom of writing the family name before the personal name of an individual. • •

2003 November 16 2003-11-16: the ISO 8601 international standard orders the components of a date like this, and additionally uses leading zeros, e.g. 0813-03-01, to be easily read and sorted by computers. It is used with UTC in the Internet date/time format (see the external link below). This format is also favoured in certain Asian countries, mainly East Asian countries, as well as in some European countries. The big endian convention is also frequently used in Canada, but all three conventions are used there.[1]

It is also extended through the universal big-endian format clock time: 2003 Nov. 16, 18h 14m 12s, or 2003/11/16/18:14:12 or 2003-11-16T18:14:12.

[edit] Middle endian forms, starting with the month This sequence is used only in the United States and a few other countries (listed below) that have been heavily influenced by the US. • • •

November 16, 2003 Nov. 16, 2003 11/16/2003, 11-16-2003, 11.16.2003 or 11.16.03

[edit] Usage issues The many numerical forms can create confusion when used in international correspondence, particularly when abbreviating the year to its final two digits. For example, '9/11' can refer to both 'The fall of the Berlin Wall' on 9 November 1989 and to the September 11, 2001 attacks. In the United States, dates are rarely written in purely numerical forms in formal writing. In the United Kingdom, while it is regarded as acceptable, but rare, to write monthname day, year (as well as day monthname year), this order is never used when written numerically, although, due to American media influence, the American shorthand "9/11" is widely understood as referring to the 11th of September aeroplane attacks.[2] When numbers are used to represent months, a significant amount of confusion can arise from the ambiguity of a date order; especially when the numbers representing the day, month or year are low, it can be impossible to tell which order is being used. This can be clarified by using four digits to represent years, and naming the month; for example, "Feb" instead of "02". In some countries Roman numerals are used to denote the month, e.g. 11.IX.2001.[citation needed] Many Internet sites use year-month-day, and those using other conventions often write out the month (9-MAY-2001, MAY 09 2001, etc.) so there is no ambiguity. The ISO 8601 date order, with four-digit years, is specifically chosen to be unambiguous. The ISO 8601 standard also has the advantage of being language independent and is therefore useful when there may be no language context and a universal application is desired (expiration dating on export products, for example). In addition, the ISO considers its ISO 8601 standard to make sense from a logical perspective.[3] Mixed units, for example feet and inches, or pounds and ounces, are normally written with the largest unit first, in decreasing order. Numbers are also written in that order, so the digits of 2006 indicate, in order, the millennium, the century within the millennium, the decade within the century, and the year within the decade. The only date order that is consistent with these well-established conventions is year-month-day. A plain text list of dates with this format can be easily sorted by word processors, spreadsheets and other software tools with built-in sorting functions. An early U.S. Federal Information Processing Standard recommended 2-digit years. This is now widely recognized as a bad idea, because of the year 2000 problem. Some U.S. government agencies now use ISO 8601 with 4 digit year.[4][5] When transitioning from one date notation to another, people often write both Old Style and New Style dates.

dd-mm-yyyy dd-mm-yyyy and yyyy-mm-dd yyyy-mm-dd yyyy mm-dd-yyyy, dd-mm-yyyy, and yyyy-mm-dd

mm-dd-yyyy

mm-dd-yyyy and dd-mm-

[edit] dd/mm/yyyy or dd.mm.yyyy (day, month, year) Using the dd/mm/yyyy format, the 30th December 2006 would be written as 30/12/2006. The dd/mm/yyyy format is used in: • • • • • • • • • • • • • • • • • • • • • • •

• • • • • • • • • • • • • • •

Albania[6][7] (some use of ISO 8601)[8] Algeria[9][10] Argentina[11][12] Armenia (dd.mm.yyyy)[13][14] Australia[15][16][17] Austria (using dots (which denote ordinal numbering) as in “d.m.(yy)yy” or sometimes "d. month (yy)yy")[18][19] Azerbaijan (dd.mm.yyyy)[20] Bahrain[21] Bangladesh (century digits may be omitted, e.g. dd-mm-yy)[22] Barbados Belarus (dd.mm.yyyy)[23][24] Belgium[25][26] Bolivia[27] Brazil (dd.mm.yyyy)[28][29] Bulgaria (dd.mm.yyyy)[30][31] Canada (All 3 main types are used in Canada - in French and in English) Chile[32] Colombia[33] Costa Rica[34] Croatia (d. m. yyyy. or d. month yyyy; yyyy-mm-dd also used widely)[35][36] Cyprus Czech Republic (d. m. yyyy or d. month yyyy)[37][38] Denmark (The format dd-mm-yy(yy) is the traditional Danish date format.[39] The international format yyyy-mm-dd or yyyymmdd is also accepted. There are no preferences, although the traditional format is the most widely used. The formats dd.'monthname' yyyy and in handwriting d/m/yy are also acceptable. [40]) Dominica Dominican Republic[41] Ecuador[42] Egypt[43][44] El Salvador[45] Estonia (d.m.yyyy or d. month yyyy)[46][47] Finland (d.m.yyyy or d. month yyyy)[48] France (dd-mm-yyyy or dd/mm/yyyy)[49][50] Georgia (dd.mm.yyyy) Germany (using dots (which denote ordinal numbering) as in “d.m.(yy)yy” or sometimes "d. month (yy)yy")[51] Greece[52][53] Greenland (dd.mm.yyyy)[54] Grenada Guatemala[55] Guyana

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Hong Kong (in English)[56] Honduras[57] Iceland (dd.mm.yyyy)[58][59] Iran (yyyy/mm/dd) Ireland (dd-m-yyyy)[60] India (dd.mm.yyyy in Bengali; dd-mm-yyyy in Gujarati, Hindi, Marathi, Punjabi, Tamil; d-myyyy in Telugu, no leading zeroes used)[61][62] Indonesia[63] Iraq (dd/mm/yyyy)[64] Ireland[65] Israel (dd/mm/yyyy)[66][67] Italy[68] Jamaica[69] Jordan[70] Kazakhstan (dd.mm.yyyy)[71] Kenya (d/m/yyyy and m/d/yyyy)[72] Kuwait[73] Kyrgyzstan (dd.mm.yyyy) Latvia (dd.mm.yyyy[74]; official standard is year-month-day[citation needed]) Lebanon[75] Libya[76] Luxembourg(dd/mm/yyyy in French,[77] d.m.yyyy in German[78]) Macau (in Portuguese & English) Macedonia (dd.mm.yyyy)[79] Malaysia[80] Mexico[81] Montenegro (d.m.yyyy) Morocco[82] Netherlands (using hyphens as in “dd-mm-(yy) yy”, very often "d month (yy)yy")[83] New Zealand[84] Nicaragua[85] Norway (d.m.y; the fraction form d/m-y is common, but incorrect[citation needed]) Oman[86] Pakistan[87] (dd-mm-(yy)yy) Panama[88] Paraguay[89] Peru[90] Philippines (in Filipino) Poland (dd.mm.yyyy[91], more official is d <month in genitive> yyyy, occasionally archaic format d <month as roman figure> yyyy, often with dots as separators)[92][93] Portugal[94] Qatar[95] Romania (dd.mm.yyyy)[96][97] Russia (dd.mm.yyyy)[98] Saint Kitts and Nevis Saint Lucia Saint Vincent and the Grenadines Saudi Arabia (dd/mm/yyyy in Islamic and Gregorian calendar systems,[99][100] except for major companies, which conventionally use the American mm/dd/yyyy format[citation needed]) Serbia (d.m.yyyy)[101][102][103] Singapore (English)[104] Slovakia (d.m.yyyy, some use of dd-mm-yyyy)[105][106]

• • • • • • • • • • • • • • • • • • •

Slovenia (d.m.yyyy or d. mmmm yyyy)[107] Spain[108] Sweden (as d/m yyyy, although the yyyy-mm-dd form is more common and the national standard.) Switzerland (dd.mm.yyyy)[109][110] Syria[111] Tajikistan (dd.mm.yyyy)[112] Thailand (with Buddhist Era years instead of Common Era)[113] Trinidad and Tobago[114] Tunisia[115] Turkey[116][117] Turkmenistan (dd.mm.yyyy)[118] Ukraine (dd.mm.yyyy[119]; some cases of dd/mm/yyyy[120]) United Arab Emirates[121] United Kingdom[122][123] Uruguay[124][125] Uzbekistan (dd.mm.yyyy Cyrillic, dd/mm yyyy Latin)[126][127][127] Venezuela[128][129] Vietnam[130] Yemen[131][132]

[edit] mm/dd/yy or mm/dd/yyyy (month, day, year) Using the mm/dd/yy format, October 18, 2008 would be written as 10/18/08. The mm/dd/yy format is used in: • • • • • • • •

Belize[133] Canada (Although most official documents use the yyyy-mm-dd format, the mm/dd/yy format is also understood due to influences from the United States.)[134] Federated States of Micronesia[135] Kenya[136] Palau Philippines (d/m/yy in Filipino language.[citation needed] May still be found in certain contexts, mm/dd/yy is used in English)[137] Puerto Rico[138] United States[139]

[edit] yyyy-mm-dd (year, month, day) Using the yyyy-mm-dd format, the 30th of December 2006 would be written as 2006-12-30. •

Used internationally in some contexts as the ISO 8601 standard

• •

Albania (more references indicate use of dd/mm/yyyy, see above)[8] Canada (yyyy-mm-dd, government all-numeric standard)[140] (All 3 main types are used in Canadain French and in English) China (yyyy-mm-dd or yyyy 年 m 月 d 日 with no leading zeroes)[141] Denmark (The format dd-mm-yy(yy) is the traditional Danish date format. The international format yyyy-mm-dd or yyyymmdd is also accepted. There are no preferences, although the traditional format is the most widely used. The formats dd.'monthname' yyyy and in handwriting d/m/yy are also acceptable. [40])

• •

• • • • • • • • • • • • • • • • •

Europe[142] Hong Kong (yyyy 年 m 月 d 日 with no leading zeroes;[143] and dd/mm/yyyy for English[144]) Hungary (yyyy.mm.dd[145][8] – traditionally the number of the month is sometimes written in Roman numerals[citation needed]) Japan, often in the form yyyy 年 mm 月 dd 日;[146] sometimes Japanese era year is used, e.g. 平成 18 年 12 月 30 日.[147] Korea (yyyy 년 mm 월 dd 일; yyyy/mm/dd also used)[148] Latvia[149] (But often dd.mm.yyyy. is used[citation needed]) Lithuania (yyyy-mm-dd)[150] Macau (same as Hong Kong)[151] Mongolia (yyyy.mm.dd)[152] Nepal[citation needed] (also see Nepal Sambat which is also in use) Norway[153] Singapore (Chinese representation: yyyy 年 m 月 d 日, no leading zeroes)[154] Slovenia[155] South Africa (yyyy/mm/dd;[156][157] "d/m/yy" is a common alternative[citation needed]) Spain (Basque: yyyy.mm.dd)[158] Sweden (national standard format)[159] Taiwan; same as China except year might be represented using ROC era system: 民國 95 年 12 月 30 日.[160]

[edit] Advantages for ordering in sequence

Editors are currently in dispute concerning points of view expressed in this section. Please help to discuss and resolve the dispute before removing this message. (November 2008) One of the advantages of using the ISO 8601 standard date format is that when dates in this format are ordered by a standard collation i.e by leading characters first, they are also in date order, for example: 1998-02-28 (28 February 1998) 1999-03-01 (01 March 1999) 2000-01-30 (30 January 2000)

Layouts with the elements in a different format or order will not give this result, although the separators do not affect sort order.[161] This ordering is often used in scientific, technical or international communication.[citation needed]

[edit] Day and year only See also: calendar, time, date-time group, Japanese calendar, and Wikibooks:English:Time The U.S. military sometimes uses a system, which they call "Julian date format"[162] that indicates the year and the actual day out of the 365 days of the year (and thus a designation of the month would not be needed). For example, "10 December 1999" can be written in some contexts as "1999345" or "99345", for the 345th day of 1999.[163] This system is most often used in US military logistics, since it makes the process of calculating estimated shipping and arrival dates easier. For example: say a tank engine takes an estimated 35 days to ship by sea from the US to Korea. If the engine is sent on 99104, it should arrive on 99139. Note that outside of the US military, this format is usually referred to as "ordinal date", rather than "Julian date."

Such ordinal date formats are also used by many computer programs (especially those for mainframe systems). Using a three-digit Julian day number saves one byte of computer storage over a two-digit month plus two-digit day, e.g. "January 17" is 017 in Julian versus 0117 in month-day format. OS/390 or its successor, z/OS, display dates in yy.ddd format for most operations. Another "ordinal" date system ("ordinal" in the sense of advancing in value by one as the date advances by one day) is in common use in astronomical calculations and referencing and uses the same name as this "logistics" system. The continuity of representation of period regardless of the time of year being considered is obviously highly useful to both groups of specialists. The astronomers describe their system too as being a "Julian date", and it is described in more detail in the article Julian date. Unlike the system described above, the astronomical system does not consider years, it only counts days. Thus it is unperturbed by complications such as leap years.

[edit] Week number used Companies in Europe often use year, week number and day for planning purposes. So, for example, an event in a project can happen on w43 (week 43) or w43-1 (Monday, week 43) or, if the year needs to be indicated, on w0543 or w543 (year 2005 week 43). The ISO does present a standard for identifying weeks, but as it does not match up with Gregorian calendar (the beginning and ending days of a given year do not match up), this standard is somewhat more problematic than the other standards for dates.

[edit] Expressing dates in spoken English In British English, full dates are usually written and spoken as 7th December 1941 (or 7 December 1941) and pronounced "the seventh of December, nineteen forty-one" (note mandatory usage of "the" and "of"), with the occasional usage of December 7, 1941 ("December the seventh, nineteen forty-one"). In common with continental European usage, however, numerical dates are invariably ordered dd/mm/yyyy. In the United States, the usual written form is December 7, pronounced "December the seventh" or colloquially "December seventh".

[edit] See also • •

Date and time notation by country Internationalization and localization

[edit] References

Money From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Money (disambiguation). "Dinero" redirects here. For obsolete Spanish currency, see Spanish dinero. For the community in the United States, see Dinero, Texas.

Various denominations of currency, one form of money.

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Money is anything that is generally accepted as payment for goods and services and repayment of debts.[1] The main uses of money are as a medium of exchange, a unit of account, and a store of value.[2] Some authors explicitly require money to be a standard of deferred payment.[3] The term "price system" is sometimes used to refer to methods using commodity valuation or money accounting systems. The word "money" is believed to originate from a temple of Hera, located on Capitoline, one of Rome's seven hills. In the ancient world Hera was often associated with money. The temple of Juno Moneta at Rome was the place where the mint of Ancient Rome was located.[4]. The name "Juno" may derive from the Etruscan goddess Uni (which means "the one", "unique", "unit", "union", "united") and "Moneta"

either from the Latin word "monere" (remind, warn, or instruct) or the Greek word "moneres" (alone, unique).

Contents [hide]

• • •

1 Economic characteristics o 1.1 Medium of exchange o 1.2 Unit of account o 1.3 Store of value 2 Market liquidity 3 Types of money o 3.1 Commodity money o 3.2 Representative money o 3.3 Credit money o 3.4 Fiat money o 3.5 Money supply o 3.6 Monetary policy 4 History of money 5 See also 6 References

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7 External links

•

• •

Economic characteristics Money is generally considered to have the following characteristics, which are summed up in a rhyme found in older economics textbooks: "Money is a matter of functions four, a medium, a measure, a standard, a store." That is, money functions as a medium of exchange, a unit of account, a standard of deferred payment, and a store of value.[2][5][6] There have been many historical arguments regarding the combination of money's functions, some arguing that they need more separation and that a single unit is insufficient to deal with them all. One of these arguments is that the role of money as a medium of exchange is in conflict with its role as a store of value: its role as a store of value requires holding it without spending, whereas its role as a medium of exchange requires it to circulate.[6] Others argue that storing of value is just deferral of the exchange, but does not diminish the fact that money is a medium of exchange that can be transported both across space and time.[7] 'Financial capital' is a more general and inclusive term for all liquid instruments, whether or not they are a uniformly recognized tender.

Medium of exchange Main article: Medium of exchange Money is used as an intermediary for trade, in order to avoid the inefficiencies of a barter system, which are sometimes referred to as the 'double coincidence of wants problem'. Such usage is termed a medium of exchange.

Unit of account

Main article: Unit of account A unit of account is a standard numerical unit of measurement of the market value of goods, services, and other transactions. Also known as a "measure" or "standard" of relative worth and deferred payment, a unit of account is a necessary prerequisite for the formulation of commercial agreements that involve debt. • • •

Divisible into small units without destroying its value; precious metals can be coined from bars, or melted down into bars again. Fungible: that is, one unit or piece must be perceived as equivalent to any other, which is why diamonds, works of art or real estate are not suitable as money. A specific weight, or measure, or size to be verifiably countable. For instance, coins are often made with ridges around the edges, so that any removal of material from the coin (lowering its commodity value) will be easy to detect.

Store of value Main article: Store of value To act as a store of value, a commodity, a form of money, or financial capital must be able to be reliably saved, stored, and retrieved — and be predictably useful when it is so retrieved. Fiat currency like paper or electronic currency no longer backed by gold in most countries is not considered by some economists to be a store of value.

Market liquidity Main article: Market liquidity Liquidity describes how easily an item can be traded for another item, or into the common currency within an economy. Money is the most liquid asset because it is universally recognised and accepted as the common currency. In this way, money gives consumers the freedom to trade goods and services easily without having to barter. Liquid financial instruments are easily tradable and have low transaction costs. There should be no — or minimal — spread between the prices to buy and sell the instrument being used as money.

Types of money In economics, money is a broad term that refers to any financial instrument that can fulfill the functions of money (detailed above). Modern monetary theory distinguishes among different types of monetary aggregates, using a categorization system that focuses on the liquidity of the financial instrument used as money.

Commodity money Main article: Commodity money Commodity money value comes from the commodity out of which it is made. The commodity itself constitutes the money, and the money is the commodity.[8] Examples of commodities that have been used as mediums of exchange include gold, silver, copper, rice, salt, peppercorns, large stones, decorated belts,

shells, alcohol, cigarettes, cannabis, candy, barley, etc. These items were sometimes used in a metric of perceived value in conjunction to one another, in various commodity valuation or Price System economies. Use of commodity money is similar to barter, but a commodity money provides a simple and automatic unit of account for the commodity which is being used as money.

Representative money Main article: Representative money Representative money is money that consists of token coins, other physical tokens such as certificates, and even non-physical "digital certificates" (authenticated digital transactions) that can be reliably exchanged for a fixed quantity of a commodity such as gold, silver or potentially water, oil or food. Representative money thus stands in direct and fixed relation to the commodity which backs it, while not itself being composed of that commodity.

Banknotes from all around the world donated by visitors to the British Museum, London.

Credit money Main article: Credit money Credit money is any claim against a physical or legal person that can be used for the purchase of goods and services.[8] Credit money differs from commodity and fiat money in two ways: It is not payable on demand (although in the case of fiat money, "demand payment" is a purely symbolic act since all that can be demanded is other types of fiat currency) and there is some element of risk that the real value upon fulfillment of the claim will not be equal to real value expected at the time of purchase.[8] This risk comes about in two ways and affects both buyer and seller. First it is a claim and the claimant may default (not pay). High levels of default have destructive supply side effects. If manufacturers and service providers do not receive payment for the goods they produce, they will not have the resources to buy the labor and materials needed to produce new goods and services. This reduces supply, increases prices and raises unemployment, possibly triggering a period of stagflation. In extreme cases, widespread defaults can cause a lack of confidence in lending institutions and lead to economic depression. For example, abuse of credit arrangements is considered one of the significant causes of the Great Depression of the 1930s.[9] The second source of risk is time. Credit money is a promise of future payment. If the interest rate on the claim fails to compensate for the combined impact of the inflation (or deflation) rate and the time value of

money, the seller will receive less real value than anticipated. If the interest rate on the claim overcompensates, the buyer will pay more than expected.

Fiat money Main article: Fiat money Fiat money is any money whose value is determined by legal means. The terms fiat currency and fiat money relate to types of currency or money whose usefulness results not from any intrinsic value or guarantee that it can be converted into gold or another currency, but instead from a government's order (fiat) that it must be accepted as a means of payment.[10] [11] Fiat money is created when a type of credit money (typically notes from a central bank, such as the Federal Reserve System in the U.S.) is declared by a government act (fiat) to be acceptable and officiallyrecognized payment for all debts, both public and private. Fiat money may thus be symbolic of a commodity or a government promise, though not a completely specified amount of either of these. Fiat money is thus not technically fungible or tradable directly for fixed quantities of anything, except more of the same government's fiat money. Fiat moneys usually trade against each other in value in an international market, as with other goods. An exception to this is when currencies are locked to each other, as explained below. Many but not all fiat moneys are accepted on the international market as having value. Those that are trade indirectly against any internationally available goods and services [8]. Thus the number of U.S. dollars or Japanese yen which are equivalent to each other, or to a gram of gold metal, are all market decisions which change from moment to moment on a daily basis. Occasionally, a country will peg the value of its fiat money to that of the fiat money of a larger economy: for example the Belize dollar trades in fixed proportion (at 2:1) to the U.S. dollar, so there is no floating value ratio of the two currencies. Fiat money, if physically represented in the form of currency (paper or coins) can be easily damaged or destroyed. However, here fiat money has an advantage over representative or commodity money, in that the same laws that created the money can also define rules for its replacement in case of damage or destruction. For example, the U.S. government will replace mutilated federal reserve notes (U.S. fiat money) if at least half of the physical note can be reconstructed, or if it can be otherwise proven to have been destroyed.[12] By contrast, commodity money which has been destroyed or lost is gone.

Money supply Main article: Money supply The money supply is the amount of money within a specific economy available for purchasing goods or services. The supply in the US is usually considered as four escalating categories M0, M1, M2 and M3. The categories grow in size with M3 representing all forms of money (including credit) and M0 being just base money (coins, bills, and central bank deposits). M0 is also money that can satisfy private banks' reserve requirements. In the US, the Federal Reserve is responsible for controlling the money supply, while in the Euro area the respective institution is the European Central Bank. Other central banks with significant impact on global finances are the Bank of Japan, People's Bank of China and the Bank of England. When gold is used as money, the money supply can grow in either of two ways. First, the money supply can increase as the amount of gold increases by new gold mining at about 2% per year, but it can also increase more during periods of gold rushes and discoveries, such as when Columbus discovered the new world and brought gold back to Spain, or when gold was discovered in California in 1848. This kind of

increase helps debtors, and causes inflation, as the value of gold goes down. Second, the money supply can increase when the value of gold goes up. This kind of increase in the value of gold helps savers and creditors and is called deflation, where items for sale are less expensive in terms of gold. Deflation was the more typical situation for over a century when gold and credit money backed by gold were used as money in the US from 1792 to 1913.

Monetary policy Main article: Monetary policy Monetary policy is the process by which a government, central bank, or monetary authority manages the money supply to achieve specific goals. Usually the goal of monetary policy is to accommodate economic growth in an environment of stable prices. For example, it is clearly stated in the Federal Reserve Act that the Board of Governors and the Federal Open Market Committee should seek “to promote effectively the goals of maximum employment, stable prices, and moderate long-term interest rates.”[13] A failed monetary policy can have significant detrimental effects on an economy and the society that depends on it. These include hyperinflation, stagflation, recession, high unemployment, shortages of imported goods, inability to export goods, and even total monetary collapse and the adoption of a much less efficient barter economy. This happened in Russia, for instance, after the fall of the Soviet Union. Governments and central banks have taken both regulatory and free market approaches to monetary policy. Some of the tools used to control the money supply include: • • • • • • • •

changing the interest rate at which the government loans or borrows money currency purchases or sales increasing or lowering government borrowing increasing or lowering government spending manipulation of exchange rates raising or lowering bank reserve requirements regulation or prohibition of private currencies taxation or tax breaks on imports or exports of capital into a country

For many years much of monetary policy was influenced by an economic theory known as monetarism. Monetarism is an economic theory which argues that management of the money supply should be the primary means of regulating economic activity. The stability of the demand for money prior to the 1980s was a key finding of Milton Friedman and Anna Schwartz[14] supported by the work of David Laidler[15], and many others. The nature of the demand for money changed during the 1980s owing to technical, institutional, and legal factors and the influence of monetarism has since decreased.

History of money Main article: History of money

Himba woman covered with a traditional ochre pigment The use of barter like methods may date back to at least 100,000 years ago. Trading in red ochre is attested in Swaziland, shell jewellery in the form of strung beads also dates back to this period, and had the basic attributes needed of commodity money. To organize production and to distribute goods and services among their populations, before market economies existed, people relied on tradition, top-down command, or community cooperation. The Shekel referred to an ancient unit of weight and currency. The first usage of the term came from Mesopotamia circa 3000 BC. and referred to a specific mass of barley which related other values in a metric such as silver, bronze, copper etc. A barley/shekel was originally both a unit of currency and a unit of weight.[16]

A 640 BCE one-third stater electrum coin from Lydia, shown larger. According to Herodotus, and most modern scholars, the Lydians were the first people to introduce the use of gold and silver coin.[17] It is thought that these first stamped coins were minted around 650-600 BC.[18] A stater coin was made in the stater (trite) denomination. To complement the stater, fractions were made: the trite (third), the hekte (sixth), and so forth in lower denominations. The name of Croesus of Lydia became synonymous with wealth in antiquity. Sardis was renowned as a beautiful city. Around 550 BC, Croesus contributed money for the construction of the temple of Artemis at Ephesus, one of the Seven Wonders of the ancient world. The first banknotes were used in China in the 7th century, and the first in Europe issued by Stockholms Banco in 1661. In the Western world, a prevalent term for coin-money has been specie, stemming from Latin in specie "in kind".[19]

See also Numismatics portal

Wikiquote has a collection of quotations related to: Money Look up Money in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Money • • • • • • • • • • • • • • • • • •

Category:Money Coin of account Counterfeit, for Counterfeiting of Money Credit money Currency market Economics Electronic money Federal Reserve Fractional reserve banking Full reserve banking Labor-time voucher Local Exchange Trading Systems Money creation non-market economics Numismatics — Collection and study of money Seignorage Standard of deferred payment World currency

References

Currency From Wikipedia, the free encyclopedia

Jump to: navigation, search For current exchange rates, see exchange links.

Numismatics Terminology Portal Currency Coins, Banknotes, Forgery

Circulating currencies Community currencies Company scrip, LETS, Time dollars

Fictional currencies Ancient currencies Greek, Roman, Byzantine

Medieval currencies Modern currencies Africa, The Americas, Europe, Asia, Oceania

Production Mint, Designers Coining, Milling, Hammering, Cast

Exonumia Credit cards, Medals, Tokens

Notaphily Banknotes

Scripophily Stocks, Bonds v•d•e

A currency is a unit of exchange, facilitating the transfer of goods and/or services.[citation needed] It is one form of money, where money is anything that serves as a medium of exchange, a store of value, and a standard of value. Currencies are the dominant medium of exchange.[citation needed] Coins and paper money are both forms of currency.

Currencies around the world.

Contents [hide] •

1 History o 1.1 Early currency

1.2 Coinage 1.3 Era of hard and credit money 1.4 Legal tender era 1.5 Paper money era 2 Modern currencies 3 Local currencies 4 Proposed currencies 5 See also o 5.1 Accounting units o 5.2 Lists o o o o

• • • •

•

6 References

In most cases, each country has monopoly control over the supply and production of its own currency. To facilitate trade between these currency zones, there are exchange rates, which are the prices at which currencies (and the goods and services of individual currency zones) can be exchanged against each other. Currencies can be classified as either floating currencies or fixed currencies based on their exchange rate regime. In cases where a country does have control of its own currency, that control is exercised either by a central bank or by a Ministry of Finance. In either case, the institution that has control of monetary policy is referred to as the monetary authority. Monetary authorities have varying degrees of autonomy from the governments that create them. In the United States, the Federal Reserve System operates without direct oversight by the legislative or executive branches. It is important to note that a monetary authority is created and supported by its sponsoring government, so independence can be reduced or revoked by the legislative or executive authority that creates it. However, in practical terms, the revocation of authority is not likely. In almost all Western countries, the monetary authority is largely independent from the government. Several countries can use the same name for their own distinct currencies (e.g., dollar in Canada and the United States). By contrast, several countries can also use the same currency (e.g., the euro), or one country can declare the currency of another country to be legal tender. For example, Panama and El Salvador have declared U.S. currency to be legal tender, and from 1791–1857, Spanish silver coins were legal tender in the United States. At various times countries have either re-stamped foreign coins, or used currency board issuing one note of currency for each note of a foreign government held, as Ecuador currently does. Each currency typically has a main currency unit (the U.S. dollar, for example, or the euro) and a fractional currency, often valued at 1⁄100 of the main currency: 100 cents = 1 dollar, 100 centimes = 1 franc, 100 pence = 1 pound, although units of 1⁄10 or 1⁄1000 are also common. Some currencies do not have any smaller units at all. Mauritania and Madagascar are the only remaining countries that do not use the decimal system; instead, the Mauritanian ouguiya is divided into 5 khoums, while the Malagasy ariary is divided into 5 iraimbilanja. In these countries, words like dollar or pound "were simply names for given weights of gold."[1] Due to inflation khoums and iraimbilanja have in practice fallen into disuse. (See non-decimal currencies for other historic currencies with non-decimal divisions.)

[edit] History

[edit] Early currency The origin of currency is the creation of a circulating medium of exchange based on a unit of account which quickly becomes a store of value. Currency evolved from two basic innovations: the use of counters to assure that shipments arrived with the same goods that were shipped, and later with the use of silver ingots to represent stored value in the form of grain.[citation needed] Both of these developments had occurred by 2000 BC. Originally money was a form of receipting grain stored in temple granaries in ancient Egypt and Mesopotamia. This first stage of currency, where metals were used to represent stored value, and symbols to represent commodities, formed the basis of trade in the Fertile Crescent for over 1500 years. However, the collapse of the Near Eastern trading system pointed to a flaw: in an era where there was no place that was safe to store value, the value of a circulating medium could only be as sound as the forces that defended that store. Trade could only reach as far as the credibility of that military. By the late Bronze Age, however, a series of international treaties had established safe passage for merchants around the Eastern Mediterranean, spreading from Minoan Crete and Mycenae in the North West to Elam and Bahrein in the South East. Although it is not known what functioned as a currency to facilitate these exchanges, it is thought that ox-hide shaped ingots of copper, produced in Cyprus may have functioned as a currency. It is thought that the increase in piracy and raiding associated with the Bronze Age collapse, possibly produced by the Peoples of the Sea, brought this trading system to an end. It was only with the recovery of Phoenician trade in the ninth and tenth centuries, that saw a return to prosperity, and the appearance of real coinage, possibly first in Anatolia with Croesus of Lydia and subsequently with the Greeks and Persians. In Africa many forms of value store have been used including beads, ingots, ivory, various forms of weapons, livestock, the manilla currency, ochre and other earth oxides, and so on. The manilla rings of West Africa were one of the currencies used from the 15th century onwards to buy and sell slaves. African currency is still notable for its variety, and in many places various forms of barter still apply.

[edit] Coinage These factors led to the shift of the store of value being the metal itself: at first silver, then both silver and gold. Metals were mined, weighed, and stamped into coins. This was to assure the individual taking the coin that he was getting a certain known weight of precious metal. Coins could be counterfeited, but they also created a new unit of account, which helped lead to banking. Archimedes' principle was that the next link in currency occurred: coins could now be easily tested for their fine weight of metal, and thus the value of a coin could be determined, even if it had been shaved, debased or otherwise tampered with (see Numismatics). In most major economies using coinage, copper, silver and gold formed three tiers of coins. Gold coins were used for large purchases, payment of the military and backing of state activities. Silver coins were used for large, but common, transactions, and as a unit of account for taxes, dues, contracts and fealty, while copper coins represented the coinage of common transaction. This system had been used in ancient India since the time of the Mahajanapadas. In Europe, this system worked through the medieval period because there was virtually no new gold, silver or copper introduced through mining or conquest. Thus the overall ratios of the three coinages remained roughly equivalent.

[edit] Era of hard and credit money In premodern China, the need for credit and for circulating a medium that was less of a burden than exchanging thousands of copper coins led to the introduction of paper money, commonly known today as

banknotes. This economic phenomenon was a slow and gradual process that took place from the late Tang Dynasty (618–907) into the Song Dynasty (960–1279). It began as a means for merchants to exchange heavy coinage for receipts of deposit issued as promissory notes from shops of wholesalers, notes that were valid for temporary use in a small regional territory. In the 10th century, the Song Dynasty government began circulating these notes amongst the traders in their monopolized salt industry. The Song government granted several shops the sole right to issue banknotes, and in the early 12th century the government finally took over these shops to produce state-issued currency. Yet the banknotes issued were still regionally-valid and temporary; it was not until the mid 13th century that a standard and uniform government issue of paper money was made into an acceptable nationwide currency. The already widespread methods of woodblock printing and then Bi Sheng's movable type printing by the 11th century was the impetus for the massive production of paper money in premodern China. At around the same time in the medieval Islamic world, a vigorous monetary economy was created during the 7th–12th centuries on the basis of the expanding levels of circulation of a stable high-value currency (the dinar). Innovations introduced by Muslim economists, traders and merchants include the earliest uses of credit,[2] cheques, promissory notes,[3] savings accounts, transactional accounts, loaning, trusts, exchange rates, the transfer of credit and debt,[4] and banking institutions for loans and deposits.[5] In Europe paper money was first introduced in Sweden in 1661. Sweden was rich in copper, thus, because of copper's low value, extraordinarily big coins (often weighing several kilograms) had to be made. Because the coin was so big, it was probably more convenient to carry a note stating your possession of such a coin than to carry the coin itself.[citation needed] The advantages of paper currency were numerous: it reduced transport of gold and silver, and thus lowered the risks; it made loaning gold or silver at interest easier, since the specie (gold or silver) never left the possession of the lender until someone else redeemed the note; and it allowed for a division of currency into credit and specie backed forms. It enabled the sale of stock in joint stock companies, and the redemption of those shares in paper. However, these advantages held within them disadvantages. First, since a note has no intrinsic value, there was nothing to stop issuing authorities from printing more of it than they had specie to back it with. Second, because it created money that did not exist, it increased inflationary pressures, a fact observed by David Hume in the 18th century. The result is that paper money would often lead to an inflationary bubble, which could collapse if people began demanding hard money, causing the demand for paper notes to fall to zero. The printing of paper money was also associated with wars, and financing of wars, and therefore regarded as part of maintaining a standing army. For these reasons, paper currency was held in suspicion and hostility in Europe and America. It was also addictive, since the speculative profits of trade and capital creation were quite large. Major nations established mints to print money and mint coins, and branches of their treasury to collect taxes and hold gold and silver stock.

[edit] Legal tender era The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

With the creation of central banks, currency underwent several significant changes. During both the coinage and credit money eras the number of entities which had the ability to coin or print money was quite large. One could, literally, have "a license to print money"; many nobles had the right of coinage.

Royal colonial companies, such as the Massachusetts Bay Company or the British East India Company could issue notes of credit—money backed by the promise to pay later, or exchangeable for payments owed to the company itself. This led to continual instability of the value of money. The exposure of coins to debasement and shaving, however, presented the same problem in another form: with each pair of hands a coin passed through, its value grew less. The solution which evolved beginning in the late 18th century and through the 19th century was the creation of a central monetary authority which had a virtual monopoly on issuing currency, and whose notes had to be accepted for "all debts public and private". The creation of a truly national currency, backed by the government's store of precious metals, and enforced by their military and governmental control over an area was, in its time, extremely controversial. Advocates of the old system of Free Banking repealed central banking laws, or slowed down the adoption of restrictions on local currency. (See Gold standard for a fuller discussion of the creation of a standard gold based currency). At this time both silver and gold were considered legal tender, and accepted by governments for taxes. However, the instability in the ratio between the two grew over the course of the 19th century, with the increase both in supply of these metals, particularly silver, and of trade. This is called bimetallism and the attempt to create a bimetallic standard where both gold and silver backed currency remained in circulation occupied the efforts of inflationists. Governments at this point could use currency as an instrument of policy, printing paper currency such as the United States Greenback, to pay for military expenditures. They could also set the terms at which they would redeem notes for specie, by limiting the amount of purchase, or the minimum amount that could be redeemed. By 1900, most of the industrializing nations were on some form of gold standard, with paper notes and silver coins constituting the circulating medium. Private banks and governments across the world followed Gresham's Law: keeping gold and silver paid, but paying out in notes. This did not happen all around the world at the same time, but occurred sporadically, generally in times of war or financial crisis, beginning in the early part of the 20th century and continuing across the world until the late 20th century, when the regime of floating fiat currencies came into force. One of the last countries to break away from the gold standard was the United States in 1971. Prior to this final, President Franklin D. Roosevelt authorized the confiscation of all private holdings of gold, and permitted the private banks to confiscate gold deposits pursuant to Presidential Executive Order number 6102, which effectively confiscated all privately held gold in the United States on April 5, 1933.[citation needed] No country anywhere in the world today has an enforceable gold standard or silver standard currency system.

[edit] Paper money era Main articles: Banknote and Fiat currency A banknote (more commonly known as a bill in the United States and Canada) is a type of currency, and commonly used as legal tender in many jurisdictions. With coins, banknotes make up the cash form of all modern money.

[edit] Modern currencies

British pounds, Danish kroner, euros, and Canadian dollars. To find out which currency is used in a particular country, check list of circulating currencies. Currently, the International Organization for Standardization has introduced a three-letter system of codes (ISO 4217) to define currency (as opposed to simple names or currency signs), in order to remove the confusion that there are dozens of currencies called the dollar and many called the franc. Even the pound is used in nearly a dozen different countries, all, of course, with wildly differing values. In general, the three-letter code uses the ISO 3166-1 country code for the first two letters and the first letter of the name of the currency (D for dollar, for instance) as the third letter. United States currency, for instance is globally referred to as USD. The International Monetary Fund uses a variant system when referring to national currencies. For exchange rates, see exchange rate and tables of historical exchange rates.

[edit] Local currencies Main article: Local currency In economics, a local currency is a currency not backed by a national government, and intended to trade only in a small area. Advocates such as Jane Jacobs argue that this enables an economically depressed region to pull itself up, by giving the people living there a medium of exchange that they can use to exchange services and locally-produced goods (In a broader sense, this is the original purpose of all money.) Opponents of this concept argue that local currency creates a barrier which can interfere with economies of scale and comparative advantage, and that in some cases they can serve as a means of tax evasion. Local currencies can also come into being when there is economic turmoil involving the national currency. An example of this is the Argentinian economic crisis of 2002 in which IOUs issued by local governments quickly took on some of the characteristics of local currencies.

[edit] Proposed currencies • • • • • •

Eco: West African Monetary Zone (Gambia, Ghana, Guinea, Nigeria, Sierra Leone, possibly Liberia) Metica: Mozambique (never implemented) Perun: Montenegro (never implemented) Amero: American currency union (hypothetical) Asian Currency Unit: proposed for the ASEAN +3 East African shilling: East African Community (Burundi, Kenya, Rwanda, Tanzania, Uganda)

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Khaleeji (currency): Gulf Cooperation Council (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates) Currency for Caribbean area[6]—CARICOM states except the Bahamas. QUID or Quasi Universal Intergalactic Denomination: Prototype currency for use in space. (proposed)

[edit] See also Numismatics portal • • • • • •

Exchange rate Foreign exchange Foreign exchange reserves Optimum currency area History of money World currency

[edit] Accounting units • • • • • • • • •

Franc Poincaré Special Drawing Rights European Currency Unit Currency sign Krugerrand Fictional currency Local currencies Petrocurrency Currency pair

[edit] Lists • • • • • • •

List of currencies List of circulating currencies List of historical currencies List of fictional currencies List of motifs on banknotes List of international trade topics List of historical exchange rates

[edit] References

Economic system From Wikipedia, the free encyclopedia

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Part of a series on

Economic systems

Economic ideologies

An economic system is a system that involves the production, distribution and consumption of goods and services between the entities in a particular society. The economic system is composed of people and institutions, including their relationships to productive resources, such as through the convention of property. In a given economy, it is the systemic means by which problems of economics are addressed, such as the economic problem of scarcity through allocation of finite productive resources. Examples of contemporary economic systems include capitalist systems, socialist systems, and mixed economies. Economic systems is the economics category that includes the study of respective systems.

Anarchist · Capitalist Communist · Corporatist Contents Fascist · Georgist

[hide] Islamic · Laissez-faire Market socialist · Mercantilist

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1 Overview Protectionist · Socialist 2 Division of economic systems Syndicalist Way State-oriented Systems o 2.1· Third "Hands-on" o 2.2 "Hands-on" Private-oriented Systems o 2.3 "Hands-on" Communal-oriented Systems Sectors and systems o 2.4 "Hands-off" Private-oriented Systems o 2.5 "Hands-off" State-oriented Systems Closed · Digital Communal-oriented Systems o (Autarky) 2.6 "Hands-off" o · Gift 2.7 ·"Compromise" Mixed systems Dual Informal 3 List of economic systems by Name Market · Mixed · Natural 4 See also Open · Participatory 5 References 6Planned Further· Subsistence reading Underground · Virtual

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7 External links Other types of economies Anglo-Saxon · Feudal Global · Hunter-gatherer Information Newly industrialized country Palace · Plantation

Post-capitalist · Post-industrial Social market · Socialist market Token · Traditional Transition Business and economics portal

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[edit] Overview An economic system is a set of methods and standards brought by which a society decides and organizes the ownership and allocation of economic resources. At one extreme, production is carried in a privateenterprise system such that all resources are privately owned. It was described by Adam Smith as frequently promoting a social interest, although only a private interest was intended. Adam Smith's book, "The Wealth of Nations", changed the way people thought about economics, and is one of the most important books of the modern world. At the other extreme, following Karl Marx and Vladimir Lenin is what is commonly called a pure-communist system, such that all resources are publicly owned with an intent of minimizing inequalities of wealth among other social objectives.[1] Alternatively, 'economic system' refers to the organizational arrangements and process through which a society makes its production and consumption decisions. In creating and modifying its economic

system, each society chooses among alternative objectives and alternative decision modes. Many objectives may be seen as desirable, like efficiency, growth, liberty, and equality.[2] Part of a social system An economic system can be considered a part of the social system and hierarchically equal to the law system, political system, cultural, etc. There is often a strong correlation between certain ideologies, political systems and certain economic systems (for example, consider the meanings of the term "communism"). Many economic systems overlap each other in various areas (for example, the term "mixed economy" can be argued to include elements from various systems). There are also various mutually exclusive hierarchical categorizations. Basic types Economic systems The basic and general economic systems are: • •

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Market economy (the basis for several "hands off" systems, such as capitalism). Mixed economy (a compromise economic system that incorporates some aspects of the market approach as well as some aspects of the planned approach). Planned economy (the basis for several "hands on" systems, such as socialism). Command Economy (a complete "hands on" system, such as the Soviet economic model). Traditional economy (a generic term for the oldest and traditional economic systems) • Participatory economics (a recent proposal for a new economic system) • Inclusive Democracy (a project for a new political and economic system) There are several basic and unfinished questions that must be answered in order to resolve the problems of economics satisfactorily. The scarcity problem, for example, requires answers to basic questions, such as: what to produce, how to produce it, and who gets what is produced. An economic system is a way of answering these basic questions, and different economic systems answer them differently. fred eats ham and cheese sandwiches

[edit] Division of economic systems Typically, "hands-on" economic systems involve a greater role for society and/or the government to determine what gets produced, how it gets produced, and who gets the produced goods and services, with the stated aim of ensuring social justice and a more equitable distribution of wealth (see welfare state). Meanwhile, "hands-off" economic

systems give more power to private individuals (and perhaps corporations) to make those decisions, rather than leaving them up to society as a whole, and often limit government involvement in the economy. Often the primary concern of "hands-on" economic systems is usually egalitarianism, while the primary concern of "hands-off" economic systems is usually private property. Libertarians target individual economic freedom as a primary goal of their "hands-off" policies, though in general, most types of economic systems claim that their system of economic organization is either most efficient or socially effective. The following list divides the main economic systems into "hands-on" and "hands-off," it attempts to structure the systems in a given section by alphabetical order and in a vertical hierarchy where possible.

[edit] "Hands-on" State-oriented Systems Economic systems in which the state directs or controls economic activity. • •

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Marxian Socialism Socialism o State socialism o Market socialism Feudalism Mercantilism

[edit] "Hands-on" Private-oriented Systems A system in which large privately-owned entities control or direct the economy in their favor, or in which private shareholders invest in and own enterprises that are operated by the state or by employee cooperatives. • •

State Corporatism o Fascist Economics Capitalism o State Capitalism

[edit] "Hands-on" Communal-oriented Systems Economic systems in which a collective, such as a commune or cooperative directs or plans large-scale economic activity. • •

Communism o Anarcho-communism (a form of libertarian socialism) Socialism o Libertarian socialism o Democratic Socialism (a form of socialism in which enterprises are managed democratically by workers but are owned by the state) o Participatory Economics

[edit] "Hands-off" Private-oriented Systems Economic systems in which the economy is controlled by privately in a usually decentralized fashion and operated based on market principles.

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Capitalism o Anarcho-capitalism o Laissez-faire capitalism o Corporate capitalism Gift economy Mutualism (a form of libertarian socialism)

[edit] "Hands-off" State-oriented Systems Economic systems in which the state runs, owns and/or manages its own resources and businesses in a free-market economy with minimal regulation. • •

Socialist market economy Various socialist proposals in which the means of production are owned and operated by the state in a free-market system with no government regulation

[edit] "Hands-off" Communal-oriented Systems Economic systems that are characterized by decentralized cooperative or collective ownership that operate in market economies or decentralized, collectively-planned economies. •

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Anarchist economics o Syndicalism o Participatory Planning o Inclusive Democracy (a project for a new political and economic system based on democratic principles and libertarian socialism) Mutualism (a form of libertarian socialism) Non-property system

[edit] "Compromise" Mixed systems Economic systems that contain substantial state, private and sometimes cooperative ownership and operated in mixed economies - i.e, ones that contain substantial amounts of both market activity and economic planning. • • •

Distributism Georgism Mixed economy o American School o Dirigisme o Nordic model o Japanese System o Mercantilism o Social market economy also known as Soziale Marktwirtschaft o PROUT also known as Progressive Utilization Theory o Indicative Planning also known as a planned market economy

[edit] List of economic systems by Name

An etymologist's approach to economic systems, this list attempts to sort all possible economic systems in alphabetical order, without any division or hierarchization. • • • • • • • • • • • • • • • • •

American School Anarchism Anarcho-capitalism Anarcho-communism Autarky Barter economy Buddhist Economy Capitalism Colonialism Command economy Communism Coordinatorism Corporatism Corporate capitalism Digital Economy Distributism Dirigisme

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[edit] See also • • • •

Economy History of economic thought Political economy Economic ideology

[edit] References

Fascist socialization Feudalism Green economy Hydraulic despotism Inclusive Democracy Information economy Internet Economy Islamic economics Japanese System Knowledge Economy Libertarian communism Libertarian socialism Market economy Market socialism Marxian economics Mercantilism Mixed economy

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Mutualism National Socialism Natural economy Neo-colonialism Network Economy Nordic model Parecon Participatory economy Planned economy Progressive Utilization Theory Resource based economy Self-management Social market economy Socialism Socialist market economy Subsistence economy Traditional economy

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Virtual economy

Market From Wikipedia, the free encyclopedia

Jump to: navigation, search

A market outside of the walls of Tangier, by Louis Comfort Tiffany.

Markets may be any of a variety of different systems, institutions, procedures, social relations and infrastructures whereby persons trade, and goods and services are exchanged, forming part of the economy. Markets vary in size, range, geographic scale, location, types and variety of human communities, as well as the types of goods and services traded. Some examples include local farmers’ markets held in town squares or parking lots, shopping centers and shopping malls, international currency and commodity markets, legally created markets such as for pollution permits, and illegal markets such as the market for illicit drugs. In mainstream economics, the concept of a market is any structure that allows buyers and sellers to exchange any type of goods, services and information. The exchange of goods or services for money is a transaction. Market participants consist of all the buyers and sellers of a good who influences its price. This influence is a major study of economics and has given rise to several theories and models concerning the basic market forces of supply and demand. There are two roles in markets, buyers and sellers. The market facilitates trade and enables the distribution and allocation of resources in a society. Markets allow any tradable item to be evaluated and priced. A market emerges more or less spontaneously or is constructed deliberately by human interaction in order to enable the exchange of rights (cf. ownership) of services and goods. The historical origin of markets is the physical marketplaces which would often develop into small communities, towns and cities[citation needed].

Contents [hide]

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1 Types of markets o 1.1 Financial markets o 1.2 Prediction markets 2 Organization of markets 3 Mechanisms of markets 4 Study of markets 5 Gallery 6 Notes 7 References 8 Sources 9 See also

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10 External links

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[edit] Types of markets Although many markets exist in the traditional sense—such as a marketplace—there are various other types of markets and various organizational structures to assist their functions.

[edit] Financial markets Financial markets facilitate the exchange of liquid assets. Most investors prefer investing in two markets, the stock markets and the bond markets. NYSE, AMEX, and the NASDAQ are the most common stock markets in the US. Futures markets, where contracts future delivery of goods are exchanged, these are often and outgrowth of general commodity markets.

Currency markets are used to trade one currency for another, and are often used for speculation on currency exchange rates. The money market is the name for the global market for lending and borrowing.

[edit] Prediction markets Prediction markets are a type of speculative market in which the goods exchanged are futures on the occurrence of certain events. They apply the market dynamics to facilitate information aggregation.

[edit] Organization of markets A market can be organized as an auction, as a private electronic market, as a shopping center, as a complex institution such as a stock market, and as an informal discussion between two individuals. Markets of varying types can spontaneously arise whenever a party has interest in a good or service that some other party can provide. Hence there can be a market for cigarettes in correctional facilities, another for chewing gum in a playground, and yet another for contracts for the future delivery of a commodity. There can be black markets, where a good is exchanged illegally and virtual markets, such as eBay, in which buyers and sellers do not physically interact. There can also be markets for goods under a command economy despite pressure to repress them.

[edit] Mechanisms of markets In economics, a market that runs under laissez-faire policies is a free market. It is "free" in the sense that the government makes no attempt to intervene through taxes, subsidies, minimum wages, price ceilings, etc. Market prices may be distorted by a seller or sellers with monopoly power, or a buyer with monopsony power. Such price distortions can have an adverse effect on market participant's welfare and reduce the efficiency of market outcomes. Also, the level of organization or negotiation power of buyers, markedly affects the functioning of the market. Markets where price negotiations do not arrive at efficient outcomes for both sides are said to experience market failure.

[edit] Study of markets The study of actual existing markets made up of persons interacting in space and place in diverse ways is widely seen as an antidote to abstract and all-encompassing concepts of “the market” and has historical precendent in the works of Ferdinand Braudel and Karl Polanyi. The latter term is now generally used in two ways. First, to denote the abstract mechanisms whereby supply and demand confront each other and deals are made. In its place, reference to markets reflects ordinary experience and the places, processes and institutions in which exchanges occurs.[1] Second, the market is often used to signify an integrated, all-encompassing and cohesive capitalist world economy. A widespread trend in economic history and sociology is skeptical of the idea that it is possible to develop a theory to capture an essence or unifying thread to markets. [2]. For economic geographers, reference to regional, local, or commodity specific markets can serve to undermine assumptions of global integration, and highlight geographic variations in the structures, institutions, histories, path dependencies, forms of interaction and modes of selfunderstanding of agents in different spheres of market exchange [3] Reference to actual markets can show capitalism not as a totalizing force or completely encompassing mode of economic activity, but rather as “a set of economic practices scattered over a landscape, rather than a systemic concentration of power” [4]

C.B. MacPherson identifies an underlying model of the market underlying Anglo-American liberaldemocratic political economy and philosophy in the seventeenth and eighteenth centuries: Persons are cast as self-interested individuals, who enter into contractual relations with other such individuals, concerning the exchange of goods or personal capacities cast as commodities, with the motive of maximizing pecuniary interest. The state and its governance systems are cast as outside of this framework.[5]). This model came to dominant economic thinking in the later nineteenth century, as economists such as Ricardo, Mill, Jevons, Walras and later neo-classical economics shifted from reference to geographically located marketplaces to an abstract “market” [6]. This tradition is continued in contemporary neoliberalism, where the market is held up as optimal for wealth creation and human freedom, and the states’ role imagined as minimal, reduced to that of upholding and keeping stable property rights, contract, and money supply. This allowed for boilerplate economic and institutional restructuring under structural adjustment and post-Communist reconstruction. [7] Similar formalism occurs in a wide variety of social democratic and Marxist discourses that situate political action as antagonistic to the market. In particular, commodification theorists such as Georg Lukacs insist that market relations necessarily lead to undue exploitation of labour and so need to be opposed in toto. ,[8]). Pierre Bourdieu has suggested the market model is becoming self-realizing, in virtue of its wide acceptance in national and international institutions through the 1990s. [9]). The formalist conception faces a number of insuperable difficulties, concerning the putatively global scope of the market to cover the entire Earth, in terms of penetration of particular economies, and in terms of whether particular claims about the subjects (individuals with pecuniary interest), objects (commodities), and modes of exchange (transactions) apply to any actually existing markets. A central theme of empirical analyses is the variation and proliferation of types of markets since the rise of capitalism and global scale economies. The Regulation School stresses the ways in which developed capitalist countries have implemented varying degrees and types of environmental, economic, and social regulation, taxation and public spending, fiscal policy and government provisioning of goods, all of which have transformed markets in uneven and geographical varied ways and created a variety of mixed economies. Drawing on concepts of institutional variance and path dependency, varieties of capitalism theorists (such as Hall and Soskice) identify two dominant modes of economic ordering in the developed capitalist countries, “coordinated market economies” such as Germany and Japan, and an AngloAmerican “liberal market economies”. However, such approaches imply that the Anglo-American liberal market economies in fact operate in a matter close to the abstract notion of “the market”. While AngloAmerican countries have seen increasing introduction of neo-liberal forms of economic ordering, this has not lead to simple convergence, but rather a variety of hybrid institutional orderings. [10]. Rather, a variety of new markets have emerged, such as for carbon trading or rights to pollute. In some cases, such as emerging markets for water, different forms of privatization of different aspects of previously state run infrastructure have created hybrid private-public formations and graded degrees of commodification, commercialization and privatization [11] Problematic for market formalism is the relationship between formal capitalist economic processes and a variety of alternative forms, ranging from semi-feudal and peasant economies widely operative in many developing economies, to informal markets, barter systems, worker cooperatives, or illegal trades that occur in most developed countries. Practices of incorporation of non-Western peoples into global markets in the nineteenth and twentieth century did not merely result in the quashing of former social economic institutions. Rather, various modes of articulation arose between transformed and hybridized local traditions and social practices and the emergence world economy. So called capitalist markets in fact include and depend on a wide range of geographically situated economic practices that do not follow the market model. Economies are thus hybrids of market and non-market elements[12] Helpful here is J. K. Gibson-Graham’s complex topology of the diversity of contemporary market economies describing different types of transactions, labour, and economic agents. Transactions can occur

in underground markets (such as for marijuana) or be artificially protected (such as for patents). They can cover the sale of public goods under privatization schemes to co-operative exchanges and occur under varying degrees of monopoly power and state regulation. Likewise, there are a wide variety of economic agents, which engage in different types of transactions on different terms: One cannot assume the practices of a religious kindergarten, multinational corporation, state enterprise, or community-based cooperative can be subsumed under the same logic of calculability (pp. 53-78). This emphasis on proliferation can also be contrasted with continuing scholarly attempts to show underlying cohesive and structural similarities to different markets. [13] A prominent entry point for challenging the market model’s applicability concerns exchange transactions and the homo economicus assumption of self-interest maximization. There are now a number of streams of economic sociological analysis of markets focusing on the role of the social in transactions, and the ways transactions involve social networks and relations of trust, cooperation and other bonds. [13]. Economic geographers in turn draw attention to the ways in exchange transactions occur against the backdrop of institutional, social and geographic processes, including class relations, uneven development, and historically contingent path dependencies [14]. A useful schema is provided by Michel Callon’s concept of framing: Each economic act or transaction occurs against, incorporates and also re-performs a geographically and cultural specific complex of social histories, institutional arrangements, rules and connections. These network relations are simultaneously bracketed, so that persons and transactions may be disentangled from thick social bonds. The character of calculability is imposed upon agents as they come to work in markets and are “formatted” as calculative agencies. Market exchanges contain a history of struggle and contestation that produced actors predisposed to exchange under certain sets of rules. As such market transactions can never be disembedded from social and geographic relations and there is no sense to talking of degrees of embeddedness and disembeddeness [15]. An emerging theme worthy of further study is the interrelationship, interpenetrability and variations of concepts of persons, commodities, and modes of exchange under particular market formations. This is most pronounced in recent movement towards post-structuralist theorizing that draws on Foucault and Actor Network Theory and stress relational aspects of personhood, and dependence and integration into networks and practical systems. Commodity network approaches further both deconstruct and show alternatives to the market models concept of commodities. Here, both researchers and market actors are understood as reframing commodities in terms of processes and social and ecological relationships. Rather than a mere objectification of things traded, the complex network relationships of exchange in different markets calls on agents to alternatively deconstruct or “get with” the fetish of commodities. [16] Gibson-Graham thus read a variety of alternative markets, for fair trade and organic foods, or those using Local Exchange Trading Systems as not only contributing to proliferation, but also forging new modes of ethical exchange and economic subjectivities. Most markets are regulated by state wide laws and regulations. While barter markets exist, most markets use currency or some other form of money.

[edit] Gallery

A produce market in Banfora,

A street market in Aix-en-

Fruit and vegetables on sale in a

Burkina Faso

Provence, France

market in Bonn

[edit] Notes

Good (economics) From Wikipedia, the free encyclopedia

(Redirected from Goods) Jump to: navigation, search A good in economics is any object, service or right that increases utility, directly or indirectly, not to be confused with the adjective "good", as used in a moral or ethical sense (see Utilitarianism and Consequentialism). A good that cannot be used by consumers directly, such as an "office building" or "capital equipment", can also be referred to as a good as an indirect source of utility through resale value or as a source of income. In macroeconomics and accounting, a good is contrasted with a service. A good here is defined as a physical (tangible) product, capable of being delivered to a purchaser and involves the transfer of ownership from seller to customer, say an apple, as opposed to an (intangible) service, say a haircut. A more general term that preserves the distinction between goods and services is 'commodities'. In microeconomics, a 'good' is often used in this more inclusive sense of the word.

Contents [hide] • • •

1 Utility characteristics of goods 2 Types of goods 3 See also

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4 References

[edit] Utility characteristics of goods A good is an object whose consumption increases the utility of the consumer, for which the quantity demanded exceeds the quantity supplied at zero price. Goods are usually modeled as having diminishing marginal utility. The first car an individual purchases is very valuable; the fourth is much less useful. Thus, in these and similar goods, the marginal utility of additional units approaches zero, as the quantity consumed increases. Assuming that one cannot re-sell it, there is a point at which a consumer would decline to purchase an additional car, even at a price very near zero. This margin of utility is the consumer's satiation point. In some cases, such as the above example of a car, the lower limit of utility as quantity increases is zero. In other goods, the utility of a good can cross zero, changing from positive to negative through time. This means that what initially is a good can become bad if too much of it is consumed. For example, shots of vodka can have positive utility, but beyond some point, additional units make the consumer less happy.

Some things are useful, but not scarce enough to have monetary value, such as the Earth's atmosphere, these are referred to as 'free goods'. In economics, a bad is the opposite of a good. Ultimately, whether an object is a good or a bad depends on each individual consumer and therefore, it is important to realize that not all goods are good all the time and not all goods are goods to all people!

[edit] Types of goods Goods can be defined in a variety of ways, depending on a number a characteristics. These are listed in the table below: [hide] v•d•e

Types of goods public good - private good - common good - common-pool resource - club good - anti-rival good (non-)rivalrous good and (non-)excludable good complementary good vs. substitute good free good vs. positional good (non-)durable good - intermediate good (producer good) - final good - capital good inferior good - normal good - ordinary good - Giffen good - luxury good - Veblen good - superior good search good - (post-)experience good - merit good - credence good - demerit good - composite good

[edit] See also • • •

Fast moving consumer goods Final goods List of economics topics

[edit] References • •

Bannock, Graham et al. (1997). Dictionary of Economics, Penguin Books. Milgate, Murray (1987), "goods and commodities," The New Palgrave: A Dictionary of Economics, v. 2, pp. 546-48. Includes historical and contemporary uses of the terms in economics.

Retrieved from "http://en.wikipedia.org/wiki/Good_(economics)" Categories: Goods | Consumer theory | Supply chain management terms

Utility From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Utility (disambiguation). In economics, utility is a measure of the relative satisfaction from or desirability of consumption of various goods and services. Given this measure, one may speak meaningfully of increasing or decreasing utility, and thereby explain economic behavior in terms of attempts to increase one's utility. For illustrative purposes, changes in utility are sometimes expressed in units called utils. The doctrine of utilitarianism saw the maximization of utility as a moral criterion for the organization of society. According to utilitarians, such as Jeremy Bentham (1748-1832) and John Stuart Mill (18061876), society should aim to maximize the total utility of individuals, aiming for "the greatest happiness for the greatest number". In neoclassical economics, rationality is precisely defined in terms of imputed utility-maximizing behavior under economic constraints. As a hypothetical behavioral measure, utility does not require attribution of mental states suggested by "happiness", "satisfaction", etc. Utility is applied by economists in such constructs as the indifference curve, which plots the combination of commodities that an individual or a society requires to maintain a given level of satisfaction. Individual utility and social utility can be construed as the dependent variable of a utility function (such as an indifference curve map) and a social welfare function respectively. When coupled with production or commodity constraints, these functions can represent Pareto efficiency, such as illustrated by Edgeworth boxes and contract curves. Such efficiency is a central concept of welfare economics.

Contents [hide] • • •

1 Cardinal and ordinal utility 2 Utility functions 3 Expected utility o 3.1 Additive von Neumann-Morgenstern Utility

• • • •

4 Utility of money 5 Discussion and criticism 6 See also 7 References and additional reading

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8 External links

[edit] Cardinal and ordinal utility Economists distinguish between cardinal utility and ordinal utility. When cardinal utility is used, the magnitude of utility differences is treated as an ethically or behaviorally significant quantity. On the other hand, ordinal utility captures only ranking and not strength of preferences. An important example of a cardinal utility is the probability of achieving some target. Utility functions of both sorts assign real numbers (utils) to members of a choice set. For example, suppose a cup of Coca-Cola has utility of 120 utils, a cup of tea has a utility of 80 utils, and a cup of water has a utility of 40 utils. When speaking of cardinal utility, it could be concluded that the cup of Coca-Cola is better than the cup of tea by exactly the same amount by which the cup of tea is better than the cup of water. One is not entitled to conclude, however, that the cup of tea is two thirds as good as the cup of Coca-Cola, because this conclusion would depend not only on magnitudes of utility differences, but also on the "zero" of utility. It is tempting when dealing with cardinal utility to aggregate utilities across persons. The argument against this is that interpersonal comparisons of utility are suspect because there is no good way to interpret how different people value consumption bundles. When ordinal utilities are used, differences in utils are treated as ethically or behaviorally meaningless: the utility values assigned encode a full behavioral ordering between members of a choice set, but nothing about strength of preferences. In the above example, it would only be possible to say that coke is preferred to tea to water, but no more. Neoclassical economics has largely retreated from using cardinal utility functions as the basic objects of economic analysis, in favor of considering agent preferences over choice sets. As will be seen in subsequent sections, however, preference relations can often be rationalized as utility functions satisfying a variety of useful properties. Ordinal utility functions are equivalent up to monotone transformations, while cardinal utilities are equivalent up to positive linear transformations.

[edit] Utility functions While preferences are the conventional foundation of microeconomics, it is often convenient to represent preferences with a utility function and reason indirectly about preferences with utility functions. Let X be the consumption set, the set of all mutually-exclusive packages the consumer could conceivably consume (such as an indifference curve map without the indifference curves). The consumer's utility function ranks each package in the consumption set. If u(x) ≥ u(y), then the consumer strictly prefers x to y or is indifferent between them. For example, suppose a consumer's consumption set is X = {nothing, 1 apple, 1 orange, 1 apple and 1 orange, 2 apples, 2 oranges}, and its utility function is u(nothing) = 0, u (1 apple) = 1, u (1 orange) = 2, u

(1 apple and 1 orange) = 4, u (2 apples) = 2 and u (2 oranges) = 3. Then this consumer prefers 1 orange to 1 apple, but prefers one of each to 2 oranges. In microeconomic models, there are usually a finite set of L commodities, and a consumer may consume an arbitrary amount of each commodity. This gives a consumption set of , and each package is a vector containing the amounts of each commodity. In the previous example, we might say there are two commodities: apples and oranges. If we say apples is the first commodity, and oranges the second, then the consumption set X = and u (0, 0) = 0, u (1, 0) = 1, u (0, 1) = 2, u (1, 1) = 4, u (2, 0) = 2, u (0, 2) = 3 as before. Note that for u to be a utility function on X, it must be defined for every package in X. A utility function rationalizes a preference relation on X if for every , if and only if . If u rationalizes , then this implies is complete and transitive, and hence rational. In order to simplify calculations, various assumptions have been made of utility functions. • • • •

CES (constant elasticity of substitution, or isoelastic) utility Exponential utility Quasilinear utility Homothetic utility

Most utility functions used in modeling or theory are well-behaved. They usually exhibit monotonicity, convexity, and global non-satiation. There are some important exceptions, however. Lexicographic preferences cannot even be represented by a utility function.[1][citation needed]

[edit] Expected utility Main article: Expected utility hypothesis The expected utility theory deals with the analysis of choices among risky projects with (possibly multidimensional) outcomes. The expected utility model was first proposed by Daniel Bernoulli as a solution to the St. Petersburg paradox. Bernoulli argued that the paradox could be resolved if decisionmakers displayed risk aversion and argued for a logarithmic cardinal utility function. The first important use of the expected utility theory was that of John von Neumann and Oskar Morgenstern who used the assumption of expected utility maximization in their formulation of game theory.

[edit] Additive von Neumann-Morgenstern Utility In older definitions of utility, it makes sense to rank utilities, but not to add them together. A person can say that a new shirt is preferable to a baloney sandwich, but not that it is twenty times preferable to the sandwich. The reason is that the utility of twenty sandwiches is not twenty times the utility of one ham sandwich, by the law of diminishing returns. So it is hard to compare the utility of the shirt with 'twenty times the utility of the sandwich'. But Von Neumann and Morgenstern suggested an unambiguous way of making a comparison like this.

Their method of comparison involves considering probabilities. If a person can choose between various randomized events (lotteries), then it is possible to additively compare the shirt and the sandwich. It is possible to compare a sandwich with probability 1, to a shirt with probability p or nothing with probability 1-p. By adjusting p, the point at which the sandwich becomes preferable defines the ratio of the utilities of the two options. A notation for a lottery is as follows: if options A and B have probability p and 1-p in the lottery, write it as a linear combination: More generally, for a lottery with many possible options: . By making some reasonable assumptions about the way choices behave, von Neumann and Morgenstern showed that if an agent can choose between the lotteries, then this agent has a utility function which can be added and multiplied by real numbers, which means the utility of an arbitrary lottery can be calculated as a linear combination of the utility of its parts. This is called the expected utility theorem. The required assumptions are four axioms about the properties of the agent's preference relation over 'simple lotteries', which are lotteries with just two options. Writing to mean 'A is preferred to B', the axioms are: 1. completeness: For any two simple lotteries and , either , , or . 2. transitivity: if and , then . 3. convexity/continuity (Archimedean property): If , then there is a between 0 and 1 such that the lottery is equally preferable to . 4. independence: if , then . In more formal language: A von Neumann-Morgenstern utility function is a function from choices to the real numbers: which assigns a real number to every outcome in a way that captures the agent's preferences over both simple and compound lotteries. The agent will prefer a lottery L2 to a lottery L1 if and only if the expected utility of L2 is greater than the expected utility of L1: Repeating in category language: u is a morphism between the category of preferences with uncertainty and the category of reals as an additive group. Of all the axioms, independence is the most often discarded. A variety of generalized expected utility theories have arisen, most of which drop or relax the independence axiom. • •

CES (constant elasticity of substitution, or isoelastic) utility is one with constant relative risk aversion Exponential utility exhibits constant absolute risk aversion

[edit] Utility of money One of the most common uses of a utility function, especially in economics, is the utility of money. The utility function for money is a nonlinear function that is bounded and asymmetric about the origin. These properties can be derived from reasonable assumptions that are generally accepted by economists and decision theorists, especially proponents of rational choice theory. The utility function is concave in the

positive region, reflecting the phenomenon of diminishing marginal utility. The boundedness reflects the fact that beyond a certain point money ceases being useful at all, as the size of any economy at any point in time is itself bounded. The asymmetry about the origin reflects the fact that gaining and losing money can have radically different implications both for individuals and businesses. The nonlinearity of the utility function for money has profound implications in decision making processes: in situations where outcomes of choices influence utility through gains or losses of money, which are the norm in most business settings, the optimal choice for a given decision depends on the possible outcomes of all other decisions in the same time-period. [2]

[edit] Discussion and criticism Different value systems have different perspectives on the use of utility in making moral judgments. For example, Marxists, Kantians, and certain libertarians (such as Nozick) all believe utility to be irrelevant as a moral standard or at least not as important as other factors such as natural rights, law, conscience and/or religious doctrine. It is debatable whether any of these can be adequately represented in a system that uses a utility model. Another criticism come from the assertion that neither cardinal nor ordinary utility are empirically observable in the real world. In case of cardinal utility it is impossible to measure the level of satisfaction "quantitatively" when someone consume/purchase an apple. In case of ordinal utility, it is impossible to determine what choice were made when someone purchase an orange. Any act would involve preference over infinite possibility of set choices such as (apple, orange juice, other vegetable, vitamin C tablets, exercise, not purchasing, etc). [1][2][3]

[edit] See also • • • • • • • • • • • • • • • • • • • • • • •

Allais paradox behavioral economics Choice Modelling consumer surplus convex preferences cumulative prospect theory decision theory efficient market theory expectation utilities Ellsberg paradox game theory list of economics topics marginal utility microeconomics prospect theory risk aversion risk premium transferable utility utility maximization problem utility (patent) utility model usability applicability

[edit] References and additional reading 1. ^ Jonathan E. Ingersoll, Jr. Theory of Financial Decision Making. Rowman and Littlefield, 1987. p. 21 2. ^ J.O. Berger, Statistical Decision Theory and Bayesian Analysis. Springer-Verlag 2nd ed. (1985) ch. 2. (ISBN 3540960988) • • • • • • •

Neumann, John von and Morgenstern, Oskar Theory of Games and Economic Behavior. Princeton, NJ. Princeton University Press. 1944 sec.ed. 1947 Nash Jr., John F. The Bargaining Problem. Econometrica 18:155 1950 Anand, Paul. Foundations of Rational Choice Under Risk Oxford, Oxford University Press. 1993 reprinted 1995, 2002 Kreps, David M. Notes on the Theory of Choice. Boulder, CO. Westview Press. 1988 Fishburn, Peter C. Utility Theory for Decision Making. Huntington, NY. Robert E. Krieger Publishing Co. 1970. ISBN 978-0471260608 Plous, S. The Psychology of Judgement and Decision Making New York: McGraw-Hill, 1993 Virine, L. and Trumper M., Project Decisions: The Art and Science. Management Concepts. Vienna, VA, 2007. ISBN 978-1567262179

[edit] External links • •

Anatomy of Cobb-Douglas Type Utility Functions in 3D Anatomy of CES Type Utility Functions in 3D

Retrieved from "http://en.wikipedia.org/wiki/Utility" Categories: Utility | Economics of uncertainty | Ethical principles Hidden categories: All articles with unsourced statements | Articles with unsourced statements since April 2008

Science From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Science (disambiguation).

The Meissner effect causes a magnet to levitate above a Very low temperature superconductor

A human protected by advanced technology during the first lunar landing, demonstrates knowledge developed through study of the natural sciences. Science (from the Latin scientia, meaning "knowledge" or "knowing") is the effort to discover, and increase human understanding of how the physical world works. Using controlled methods, scientists collect data in the form of observations, records of observable physical evidence of natural phenomena,

and analyze this information to construct theoretical explanations of how things work. Knowledge in science is gained through research. The methods of scientific research include the generation of hypotheses about how natural phenomena work, and experimentation that tests these hypotheses under controlled conditions. The outcome or product of this empirical scientific process is the formulation of theory that describes human understanding of physical processes and facilitates prediction. Lavoisier says, "... the impossibility of separating the nomenclature of a science from the science itself is owing to this, that every branch of physical science must consist of three things: the series of facts which are the objects of the science, the ideas which represent these facts and the words by which these ideas are expressed."[1] A broader modern definition of science may include the natural sciences along with the social and behavioral sciences, as the main subdivisions of science, defining it as the observation, identification, description, experimental investigation, and theoretical explanation of phenomena.[2] However, other contemporary definitions still place the natural sciences, which are closely related with the physical world's phenomena, as the only true vehicles of science.

Contents [hide]

• • • •

1 History of science 2 History of usage of the word science o 2.1 Distinguished from technology 3 Scientific method o 3.1 Mathematics 4 Philosophy of science 5 Critiques o 5.1 Science, pseudoscience and nonscience o 5.2 Philosophical focus o 5.3 The media and the scientific debate o 5.4 Epistemological inadequacies 6 Scientific community o 6.1 Fields o 6.2 Institutions o 6.3 Literature 7 See also 8 Notes 9 References 10 Further reading

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11 External links

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•

[edit] History of science Main article: History of science While empirical investigations of the natural world have been described since antiquity (for example, by Aristotle, Theophrastus and Pliny the Elder), and scientific methods have been employed since the Middle Ages (for example, by Ibn al-Haytham, Abu Rayhan Biruni and Roger Bacon), the dawn of modern

science is generally traced back to the early modern period, during what is known as the Scientific Revolution of the 16th and 17th centuries. The Greek word for science is 'επιστήμη', deriving from the verb 'επίσταμαι', which literally means 'to know'.

[edit] History of usage of the word science Well into the eighteenth century, science and natural philosophy were not quite synonymous, but only became so later with the direct use of what would become known formally as the scientific method, which was earlier developed during the Middle Ages and early modern period in Europe and the Middle East (see History of scientific method). Prior to the 18th century, however, the preferred term for the study of nature was natural philosophy, while English speakers most typically referred to the study of the human mind as moral philosophy. By contrast, the word "science" in English was still used in the 17th century to refer to the Aristotelian concept of knowledge which was secure enough to be used as a sure prescription for exactly how to do something. In this differing sense of the two words, the philosopher John Locke in An Essay Concerning Human Understanding wrote that "natural philosophy [the study of nature] is not capable of being made a science".[3] By the early 1800s, natural philosophy had begun to separate from philosophy, though it often retained a very broad meaning. In many cases, science continued to stand for reliable knowledge about any topic, in the same way it is still used in the broad sense (see the introduction to this article) in modern terms such as library science, political science, and computer science. In the more narrow sense of science, as natural philosophy became linked to an expanding set of well-defined laws (beginning with Galileo's laws, Kepler's laws, and Newton's laws for motion), it became more popular to refer to natural philosophy as natural science. Over the course of the nineteenth century, moreover, there was an increased tendency to associate science with study of the natural world (that is, the non-human world). This move sometimes left the study of human thought and society (what would come to be called social science) in a linguistic limbo by the end of the century and into the next.[4] Through the 19th century, many English speakers were increasingly differentiating science (meaning a combination of what we now term natural and biological sciences) from all other forms of knowledge in a variety of ways. The now-familiar expression “scientific method,” which refers to the prescriptive part of how to make discoveries in natural philosophy, was almost unused during the early part of the 19th century, but became widespread after the 1870s, though there was rarely total agreement about just what it entailed.[4] The word "scientist," meant to refer to a systematically-working natural philosopher, (as opposed to an intuitive or empirically-minded one) was coined in 1833 by William Whewell.[5] Discussion of scientists as a special group of people who did science, even if their attributes were up for debate, grew in the last half of the 19th century.[4] Whatever people actually meant by these terms at first, they ultimately depicted science, in the narrow sense of the habitual use of the scientific method and the knowledge derived from it, as something deeply distinguished from all other realms of human endeavor. By the twentieth century, the modern notion of science as a special brand of information about the world, practiced by a distinct group and pursued through a unique method, was essentially in place. It was used to give legitimacy to a variety of fields through such titles as "scientific" medicine, engineering, advertising, or motherhood.[4] Over the 1900s, links between science and technology also grew increasingly strong.

[edit] Distinguished from technology By the end of the century, it is arguable that technology had even begun to eclipse science as a term of public attention and praise. Scholarly studies of science have begun to refer to "technoscience" rather than science or technology separately. Meanwhile, such fields as biotechnology and nanotechnology are

capturing the headlines. One author has suggested that, in the coming century, "science" may fall out of use, to be replaced by technoscience or even by some more exotic label such as "techknowledgy."[4]

[edit] Scientific method Main article: Scientific method The Bohr model of the atom, like many ideas in the history of science, was at first prompted by and later partially disproved by experiment. The scientific method seeks to explain the events of nature in a reproducible way, and to use these reproductions to make useful predictions. It is done through observation of natural phenomena, and/or through experimentation that tries to simulate natural events under controlled conditions. It provides an objective process to find solutions to problems in a number of scientific and technological fields.[6] Based on observations of a phenomenon, a scientist may generate a model. This is an attempt to describe or depict the phenomenon in terms of a logical physical or mathematical representation. As empirical evidence is gathered, a scientist can suggest a hypothesis to explain the phenomenon. This description can be used to make predictions that are testable by experiment or observation using the scientific method. When a hypothesis proves unsatisfactory, it is either modified or discarded. While performing experiments, Scientists may have a preference for one outcome over another, and it is important that this tendency does not bias their interpretation.[7][8] A strict following of the scientific method attempts to minimize the influence of a scientist's bias on the outcome of an experiment. This can be achieved by correct experimental design, and a thorough peer review of the experimental results as well as conclusions of a study.[9][10] Once the experiment results are announced or published, an important cross-check can be the need to validate the results by an independent party.[11] Once a hypothesis has survived testing, it may become adopted into the framework of a scientific theory. This is a logically reasoned, self-consistent model or framework for describing the behavior of certain natural phenomena. A theory typically describes the behavior of much broader sets of phenomena than a hypothesis—commonly, a large number of hypotheses can be logically bound together by a single theory. These broader theories may be formulated using principles such as parsimony (e.g., "Occam's Razor"). They are then repeatedly tested by analyzing how the collected evidence (facts) compares to the theory. When a theory survives a sufficiently large number of empirical observations, it then becomes a scientific generalization that can be taken as fully verified. Despite the existence of well-tested theories, science cannot claim absolute knowledge of nature or the behavior of the subject or of the field of study due to epistemological problems that are unavoidable and preclude the discovery or establishment of absolute truth. Unlike a mathematical proof, a scientific theory is empirical, and is always open to falsification, if new evidence is presented. Even the most basic and fundamental theories may turn out to be imperfect if new observations are inconsistent with them. Critical to this process is making every relevant aspect of research publicly available, which allows ongoing review and repeating of experiments and observations by multiple researchers operating independently of one another. Only by fulfilling these expectations can it be determined how reliable the experimental results are for potential use by others. Isaac Newton's Newtonian law of gravitation is a famous example of an established law that was later found not to be universal—it does not hold in experiments involving motion at speeds close to the speed of light or in close proximity of strong gravitational fields. Outside these conditions, Newton's Laws

remain an excellent model of motion and gravity. Since general relativity accounts for all the same phenomena that Newton's Laws do and more, general relativity is now regarded as a more comprehensive theory.[12]

[edit] Mathematics

Data from the famous Michelson–Morley experiment Mathematics is essential to many sciences. One important function of mathematics in science is the role it plays in the expression of scientific models. Observing and collecting measurements, as well as hypothesizing and predicting, often require extensive use of mathematics and mathematical models. Calculus may be the branch of mathematics most often used in science, but virtually every branch of mathematics has applications in science, including "pure" areas such as number theory and topology. Mathematics is fundamental to the understanding of the natural sciences and the social sciences, many of which also rely heavily on statistics. Statistical methods, comprised of mathematical techniques for summarizing and exploring data, allow scientists to assess the level of reliability and the range of variation in experimental results. Statistical thinking also plays a fundamental role in many areas of science. Computational science applies computing power to simulate real-world situations, enabling a better understanding of scientific problems than formal mathematics alone can achieve. According to the Society for Industrial and Applied Mathematics, computation is now as important as theory and experiment in advancing scientific knowledge.[13] Whether mathematics itself is properly classified as science has been a matter of some debate. Some thinkers see mathematicians as scientists, regarding physical experiments as inessential or mathematical proofs as equivalent to experiments. Others do not see mathematics as a science, since it does not require an experimental test of its theories and hypotheses. Mathematical theorems and formulas are obtained by logical derivations which presume axiomatic systems, rather than the combination of empirical observation and logical reasoning that has come to be known as the scientific method. In general, mathematics is classified as formal science, while natural and social sciences are classified as empirical sciences.[14]

[edit] Philosophy of science Velocity-distribution data of a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate. Main article: Philosophy of science The philosophy of science seeks to understand the nature and justification of scientific knowledge. It has proven difficult to provide a definitive account of the scientific method that can decisively serve to distinguish science from non-science. Thus there are legitimate arguments about exactly where the borders are, leading to the problem of demarcation. There is nonetheless a set of core precepts that have broad consensus among published philosophers of science and within the scientific community at large.

Science is reasoned-based analysis of sensation upon our awareness. As such, the scientific method cannot deduce anything about the realm of reality that is beyond what is observable by existing or theoretical means.[15] When a manifestation of our reality previously considered supernatural is understood in the terms of causes and consequences, it acquires a scientific explanation.[16] Some of the findings of science can be very counter-intuitive. Atomic theory, for example, implies that a granite boulder which appears a heavy, hard, solid, grey object is actually a combination of subatomic particles with none of these properties, moving very rapidly in space where the mass is concentrated in a very small fraction of the total volume. Many of humanity's preconceived notions about the workings of the universe have been challenged by new scientific discoveries. Quantum mechanics, particularly, examines phenomena that seem to defy our most basic postulates about causality and fundamental understanding of the world around us. Science is the branch of knowledge dealing with people and the understanding we have of our environment and how it works. There are different schools of thought in the philosophy of scientific method. Methodological naturalism maintains that scientific investigation must adhere to empirical study and independent verification as a process for properly developing and evaluating natural explanations for observable phenomena.[17] Methodological naturalism, therefore, rejects supernatural explanations, arguments from authority and biased observational studies. Critical rationalism instead holds that unbiased observation is not possible and a demarcation between natural and supernatural explanations is arbitrary; it instead proposes falsifiability as the landmark of empirical theories and falsification as the universal empirical method. Critical rationalism argues for the ability of science to increase the scope of testable knowledge, but at the same time against its authority, by emphasizing its inherent fallibility. It proposes that science should be content with the rational elimination of errors in its theories, not in seeking for their verification (such as claiming certain or probable proof or disproof; both the proposal and falsification of a theory are only of methodological, conjectural, and tentative character in critical rationalism).[18] Instrumentalism rejects the concept of truth and emphasizes merely the utility of theories as instruments for explaining and predicting phenomena.[19]

[edit] Critiques [edit] Science, pseudoscience and nonscience Main articles: Cargo cult science, Fringe science, Junk science, Pseudoscience, and Scientific misconduct Any established body of knowledge which masquerades as science in an attempt to claim a legitimacy which it would not otherwise be able to achieve on its own terms is not science; it is often known as fringe- or alternative science. The most important of its defects is usually the lack of the carefully controlled and thoughtfully interpreted experiments which provide the foundation of the natural sciences and which contribute to their advancement. Another term, junk science, is often used to describe scientific theories or data which, while perhaps legitimate in themselves, are believed to be mistakenly used to support an opposing position. There is usually an element of political or ideological bias in the use of the term. Thus the arguments in favor of limiting the use of fossil fuels in order to reduce global warming are often characterized as junk science by those who do not wish to see such restrictions imposed, and who claim that other factors may well be the cause of global warming. A wide variety of commercial advertising (ranging from hype to outright fraud) would also fall into this category. Finally, there is just plain bad science, which is commonly used to describe well-intentioned but incorrect, obsolete, incomplete, or over-simplified expositions of scientific ideas.

The status of many bodies of knowledge as true sciences, has been a matter of debate. Discussion and debate abound in this topic with some fields like the social and behavioural sciences accused by critics of being unscientific. Many groups of people from academicians like Nobel Prize physicist Percy W. Bridgman,[20] or Dick Richardson, Ph.D.—Professor of Integrative Biology at the University of Texas at Austin,[21] to politicians like U.S. Senator Kay Bailey Hutchison and other co-sponsors,[22] oppose giving their support or agreeing with the use of the label "science" in some fields of study and knowledge they consider non-scientific, ambiguous, or scientifically irrelevant compared with other fields. Karl Popper denied the existence of evidence[23] and of scientific method.[24] Popper holds that there is only one universal method, the negative method of trial and error. It covers not only all products of the human mind, including science, mathematics, philosophy, art and so on, but also the evolution of life.[25] He also contributed to the Positivism dispute, a philosophical dispute between Critical rationalism (Popper, Albert) and the Frankfurt School (Adorno, Habermas) about the methodology of the social sciences.[26]

[edit] Philosophical focus Historian Jacques Barzun termed science "a faith as fanatical as any in history" and warned against the use of scientific thought to suppress considerations of meaning as integral to human existence.[27] Many recent thinkers, such as Carolyn Merchant, Theodor Adorno and E. F. Schumacher considered that the 17th century scientific revolution shifted science from a focus on understanding nature, or wisdom, to a focus on manipulating nature, i.e. power, and that science's emphasis on manipulating nature leads it inevitably to manipulate people, as well.[28] Science's focus on quantitative measures has led to critiques that it is unable to recognize important qualitative aspects of the world.[28] It is not clear, however, if this kind of criticism is adequate to a vast number of non-experimental scientifics fields like astronomy, cosmology, evolutionary biology, complexity theory, paleontology, paleoanthropology, archeology, earth sciences, climatology, ecology and other sciences, like statistical physics of irreversible non-linear systems, that emphasize systemic and historically contingent frozen accidents. Considerations about the philosophical impact of science to the discussion of the (or lack of) meaning in human existence are not suppressed but strongly discussed in the literature of science divulgation, a movement sometimes called The Third Culture. The implications of the ideological denial of ethics for the practice of science itself in terms of fraud, plagiarism, and data falsification, has been criticized by several academics. In "Science and Ethics", the philosopher Bernard Rollin examines the ideology that denies the relevance of ethics to science, and argues in favor of making education in ethics part and parcel of scientific training.[29]

[edit] The media and the scientific debate The mass media face a number of pressures that can prevent them from accurately depicting competing scientific claims in terms of their credibility within the scientific community as a whole. Determining how much weight to give different sides in a scientific debate requires considerable expertise on the issue at hand.[30] Few journalists have real scientific knowledge, and even beat reporters who know a great deal about certain scientific issues may know little about other ones they are suddenly asked to cover.[31][32]

[edit] Epistemological inadequacies Psychologist Carl Jung believed that though science attempted to understand all of nature, the experimental method used would pose artificial, conditional questions that evoke only partial answers.[33] Robert Anton Wilson criticized science for using instruments to ask questions that produce answers only meaningful in terms of the instrument, and that there was no such thing as a completely objective vantage point from which to view the results of science.[34]

[edit] Scientific community Main article: Scientific community The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science.

[edit] Fields Main article: Fields of science Fields of science are commonly classified along two major lines: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.[35] There are also related disciplines that are grouped into interdisciplinary and applied sciences, such as engineering and health science. Within these categories are specialized scientific fields that can include elements of other scientific disciplines but often possess their own terminology and body of expertise.[36] Mathematics, which is sometimes classified within a third group of science called formal science, has both similarities and differences with the natural and social sciences.[35] It is similar to empirical sciences in that it involves an objective, careful and systematic study of an area of knowledge; it is different because of its method of verifying its knowledge, using a priori rather than empirical methods.[35] Formal science, which also includes statistics and logic, is vital to the empirical sciences. Major advances in formal science have often led to major advances in the physical and biological sciences. The formal sciences are essential in the formation of hypotheses, theories, and laws,[35] both in discovering and describing how things work (natural sciences) and how people think and act (social sciences).

[edit] Institutions

Louis XIV visiting the Académie des sciences in 1671. Learned societies for the communication and promotion of scientific thought and experimentation have existed since the Renaissance period.[37] The oldest surviving institution is the Accademia dei Lincei in

Italy.[38] National Academy of Sciences are distinguished institutions that exist in a number of countries, beginning with the British Royal Society in 1660[39] and the French Académie des Sciences in 1666.[40] International scientific organizations, such as the International Council for Science, have since been formed to promote cooperation between the scientific communities of different nations. More recently, influential government agencies have been created to support scientific research, including the National Science Foundation in the U.S. Other prominent organizations include the academies of science of many nations, CSIRO in Australia, Centre national de la recherche scientifique in France, Max Planck Society and Deutsche Forschungsgemeinschaft in Germany, and in Spain, CSIC.

[edit] Literature Main article: Scientific literature An enormous range of scientific literature is published.[41] Scientific journals communicate and document the results of research carried out in universities and various other research institutions, serving as an archival record of science. The first scientific journals, Journal des Sçavans followed by the Philosophical Transactions, began publication in 1665. Since that time the total number of active periodicals has steadily increased. As of 1981, one estimate for the number of scientific and technical journals in publication was 11,500.[42] While Pubmed lists almost 40,000, related to the medical sciences only.[43] Most scientific journals cover a single scientific field and publish the research within that field; the research is normally expressed in the form of a scientific paper. Science has become so pervasive in modern societies that it is generally considered necessary to communicate the achievements, news, and ambitions of scientists to a wider populace. Science magazines such as New Scientist, Science & Vie and Scientific American cater to the needs of a much wider readership and provide a non-technical summary of popular areas of research, including notable discoveries and advances in certain fields of research. Science books engage the interest of many more people. Tangentially, the science fiction genre, primarily fantastic in nature, engages the public imagination and transmits the ideas, if not the methods, of science. Recent efforts to intensify or develop links between science and non-scientific disciplines such as Literature or, more specifically, Poetry, include the Creative Writing <-> Science resource developed through the Royal Literary Fund.[44]

[edit] See also Science portal

Main lists: List of basic science topics and List of science topics Application

Controversy

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Military funding of science Scientific computing Scientific enterprise

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Pseudoscience Relationship between religion and science Creation-evolution controversy Scientific misconduct

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History of science and technology Historiography of science Protoscience Scientific constants named after people Scientific laws named after people Scientific phenomena named after people Scientific revolution Scientific units named after people

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Competition From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Competition (disambiguation). The examples and perspective in this article or section may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page. (August 2008)

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2008) This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (August 2008)

Competition is a rivalry between individuals, groups, nations, or animals, for territory or resources. It arises whenever two or more parties strive for a goal which cannot be shared. Competition occurs naturally between living organisms which co-exist in the same environment. For example, animals compete over water supplies, food, and mates, etc. Humans compete for water, food, and mates as well, though when these needs are met deep rivalries often arise over the pursuit of wealth, prestige, and fame. Business is often associated with competition as most companies are in competition with at least one other firm over the same group of customers. Competition may give incentives for self-improvement. For example, if two watchmakers are competing for business, they will lower their prices and improve their products to increase sales. If birds compete for a limited water supply during a drought, the more suited birds will survive to reproduce and improve the population. Rivals will often refer to their competitors as "the competition". The term can also be used to refer to the contest or tournament itself.

Contents [hide]

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1 Etymology 2 Sizes and levels 3 Destructive competition and co-operative competition o 3.1 Destructive competition o 3.2 Co-operative competition 4 Consequences 5 Economics and business 6 Law 7 Politics 8 Sports 9 Education 10 Literature 11 Biology and ecology 12 The study of competition o 12.1 Competitiveness o 12.2 Hypercompetitiveness 13 See also

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[edit] Etymology The Latin root for the verb "to compete" is "competere", which means "to seek together" or "to strive together".[1] However, even the general definition stated above is not universally accepted. Social theorists, most notably Alfie Kohn [2] and cooperativists in general, argue that the traditional definition of competition is too broad and vague. Competition which originates internally and is biologically motivated can and should be defined as either amoral competition or simply the survival instinct, i.e. behavior which is neither good nor bad, but exists to further the survival of an individual or species (for instance hunting), or behavior which is coerced (for instance self-defense). Social Darwinists, however, state that competition is not only moral, but necessary for the survival of the species.

[edit] Sizes and levels Competition may also exist at different sizes; some competitions may be between two members of a species, while other competitions can involve entire species. In an example in economics, a competition between two small stores would be considered small compared to competition between several megagiants. As a result, the consequences of the competition would also vary- the larger the competition, the larger the effect. In addition, the level of competition can also vary. At some levels, competition can be informal; more for pride and/or fun. However, other competitions can be extremely serious; for example, some human wars have erupted because of the intense competition between two nations or nationalities.

[edit] Destructive competition and co-operative competition [edit] Destructive competition Destructive competition seeks to benefit an individual/group/organism by damaging and/or eliminating competing individuals, groups and/or organisms; it opposes the desire for mutual survival. It is “winner takes all”, the rationale being that the challenge is a zero-sum game; the success of one group is dependent on the failure of the other competing groups. Destructive competition tends to promote fear, a "strike-first" mentality and embraces certain forms of trespass.[3]

[edit] Co-operative competition Further information: coopetition Co-operative competition is based upon promoting mutual survival - “everyone wins”. Adam Smith’s “invisible hand” is a process where individuals compete to improve their level of happiness but compete in a cooperative manner through peaceful exchange and without violating other people. Cooperative competition focuses individuals/groups/organisms against the environment.[3]

[edit] Consequences Competition can have both beneficial and detrimental effects. Many evolutionary biologists view interspecies and intra-species competition as the driving force of adaptation, and ultimately of evolution. However, some biologists, most famously Richard Dawkins, prefer to think of evolution in terms of competition between single genes, which have the welfare of the organism 'in mind' only insofar as that welfare furthers their own selfish drives for replication. Some social Darwinists claim (controversially) that competition also serves as a mechanism for determining the best-suited group; politically, economically and ecologically. On the negative side, competition can cause injury to the organisms involved, and drain valuable resources and energy. Human competition can be expensive, as is the case with political elections, international sports competitions, and advertising wars. It can lead to the compromising of ethical standards in order to gain an advantage: for example, several athletes have been caught using banned steroids in professional sports in order to boost their own chances of success or victory. It can also be harmful for the participants, such as athletes who injure themselves when pushing their body past its natural limits, or companies which pursue unprofitable paths while engaging in competitive rivalries.

[edit] Economics and business Main article: Competition (economics) Merriam-Webster defines competition in business as "the effort of two or more parties acting independently to secure the business of a third party by offering the most favorable terms". [2] Seen as the pillar of capitalism in that it may stimulate innovation, encourage efficiency or drive down prices, competition is touted as the foundation upon which capitalism is justified. According to microeconomic theory, no system of resource allocation is more efficient than pure competition. Competition, according to the theory, causes commercial firms to develop new products, services and technologies, which would give consumers greater selection and better products. The greater selection typically causes lower prices for the products, compared to what the price would be if there was no competition (monopoly) or little competition (oligopoly). However, competition may also lead to wasted (duplicated) effort and to increased costs (and prices) in some circumstances. For example, the intense competition for the small number of top jobs in music and movie acting leads many aspiring musicians and actors to make substantial investments in training which are not recouped, because only a fraction become successful. Three levels of economic competition have been classified: 1. The most narrow form is direct competition (also called category competition or brand competition), where products which perform the same function compete against each other. For example, one brand of pick-up trucks competes with several other brands of pick-up trucks. Sometimes, two companies are rivals and one adds new products to their line, which leads to the other company distributing the same new things, and in this manner they compete. 2. The next form is substitute or indirect competition, where products which are close substitutes for one another compete. For example, butter competes with margarine, mayonnaise and other various sauces and spreads. 3. The broadest form of competition is typically called budget competition. Included in this category is anything on which the consumer might want to spend their available money. For example, a family which has $20,000 available may choose to spend it on many different items, which can all be seen as competing with each other for the family's expenditure. Competition does not necessarily have to be between companies. For example, business writers sometimes refer to internal competition. This is competition within companies. The idea was first introduced by Alfred Sloan at General Motors in the 1920s. Sloan deliberately created areas of overlap between divisions of the company so that each division would be competing with the other divisions. For example, the Chevy division would compete with the Pontiac division for some market segments. Also, in 1931, Procter & Gamble initiated a deliberate system of internal brand-versus-brand rivalry. The company was organized around different brands, with each brand allocated resources, including a dedicated group of employees willing to champion the brand. Each brand manager was given responsibility for the success or failure of the brand, and compensated accordingly. This is known as intra-brand competition. Finally, most businesses also encourage competition between individual employees. An example of this is a contest between sales representatives. The sales representative with the highest sales (or the best improvement in sales) over a period of time would gain benefits from the employer.

It should also be noted that business and economic competition in most countries is often limited or restricted. Competition often is subject to legal restrictions. For example, competition may be legally prohibited, as in the case with a government monopoly or a government-granted monopoly. Tariffs, subsidies or other protectionist measures may also be instituted by government in order to prevent or reduce competition. Depending on the respective economic policy, the pure competition is to a greater or lesser extent regulated by competition policy and competition law. Competition between countries is quite subtle to detect, but is quite evident in the World economy. Countries compete to provide the best possible business environment for multinational corporations. Such competition is evident by the policies undertaken by these countries to educate the future workforce. For example, East Asian economies such as Singapore, Japan and South Korea tend to emphasize education by allocating a large portion of the budget to this sector, and by implementing programmes such as gifted education. (See separate sub-markets principle).

[edit] Law Main article: Competition law

The Department of Justice building in Washington, D.C. is home to the influential antitrust enforcers of U.S. competition laws Competition law, known in the United States as antitrust law, has three main functions. Firstly, it prohibits agreements aimed to restrict free trading between business entities and their customers. For example, a cartel of sports shops who together fix football jersey prices higher than normal is illegal.[4] Secondly, competition law can ban the existence or abusive behaviour of a firm dominating the market. One case in point could be a software company who through its monopoly on computer platforms makes consumers use its media player.[5] Thirdly, to preserve competitive markets, the law supervises the mergers and acquisitions of very large corporations. Competition authorities could for instance require that a large packaging company give plastic bottle licenses to competitors before taking over a major PET producer.[6] In this case (as in all three), competition law aims to protect the welfare of consumers by ensuring business must compete for its share of the market economy. In recent decades, competition law has also been sold as good medicine to provide better public services, traditionally funded by tax payers and administered by democratically accountable governments. Hence competition law is closely connected with the law on deregulation of access to markets, providing state aids and subsidies, the privatisation of state-owned assets and the use of independent sector regulators, such as the United Kingdom telecommunications watchdog Ofcom. Behind the practice lies the theory, which over the last fifty years has been dominated by neo-classical economics. Markets are seen as the most efficient method of allocating resources, although sometimes they fail, and regulation becomes necessary to protect the ideal market model. Behind the theory lies the history, reaching back further than the Roman Empire. The business practices of market traders, guilds and governments have always been subject to scrutiny and sometimes severe sanctions. Since the twentieth century, competition law has become global. The two largest, most organised and influential systems of competition regulation are United States antitrust law and European Community competition law. The respective national authorities, the U.S. Department of Justice (DOJ) and the Federal Trade Commission (FTC) in the United

States and the European Commission's Competition Directorate General (DGCOMP) have formed international support and enforcement networks. Competition law is growing in importance every day, which warrants for its careful study.

[edit] Politics Competition is also found in politics. In democracies, an election is a competition for an elected office. In other words, two or more candidates strive and compete against one another to attain a position of power. The winner gains the seat of the elected office for a predefined period of time, towards the end of which another election is usually held to determine the next holder of the office. In addition, there is inevitable competition inside a government. Because several offices are appointed, potential candidates compete against the others in order to gain the particular office. Departments may also compete for a limited amount of resources, such as for funding. Finally, where there are party systems, elected leaders of different parties will ultimately compete against the other parties for laws, funding and power. Finally, competition also exists between governments. Each country or nationality struggles for world dominance, power, or military strength. For example, the United States competed against the Soviet Union in the Cold War for world power, and the two also struggled over the different types of government (in these cases representative democracy and communism). The result of this type of competition often leads to worldwide tensions, and may sometimes erupt into warfare.

[edit] Sports

The USOC's headquarters in Colorado Springs, Colorado. The Olympic Games are regarded as the international pinnacle of sports competition. While some sports (such as fishing or hiking) have been viewed as primarily recreational, most sports are considered competitive. The majority involve competition between two or more persons (or animals and/or mechanical devices typically controlled by humans, as in horse racing or auto racing). For example, in a game of basketball, two teams compete against one another to determine who can score the most points. While there is no set reward for the winning team, many players gain an internal sense of pride. In addition, extrinsic rewards may also be given. Athletes, besides competing against other humans, also compete against nature in sports such as whitewater kayaking or mountaineering, where the goal is to reach a destination, with only natural barriers impeding the process. A regularly scheduled (for instance annual) competition meant to determine the "best" competitor of that cycle is called a championship. While professional sports have been usually viewed as intense and extremely competitive, recreational sports, which are often less intense, are often considered a healthy option for the release of competitive urges in humans. Sport provides a relatively safe venue for converting unbridled competition into harmless competition, because sports competition is restrained. Competitive sports are governed by

codified rules agreed upon by the participants. Violating these rules is considered to be unfair competition. Thus, sports provide artificial (not natural) competition; for example, competing for control of a ball, or defending territory on a playing field is not an innate biological factor in humans. Athletes in sports such as gymnastics and competitive diving compete against each other in order to come closest to a conceptual ideal of a perfect performance, which incorporates measurable criteria and standards which are translated into numerical ratings and scores by appointed judges. Sports competition is generally broken down into three categories: individual sports, such as archery; dual sports, such as doubles tennis, and team sports competition, such as cricket or football. While most sports competitions are recreation, there exist several major and minor professional sports leagues throughout the world. The Olympic Games, held every four years, is usually regarded as the international pinnacle of sports competition.

[edit] Education Competition is a major factor in education. On a global scale, national education systems, intending to bring out the best in the next generation, encourage competitiveness among students through scholarships. Countries such as England and Singapore have special education programmes which cater for specialist students, prompting charges of academic elitism. Upon receipt of their academic results, students tend to compare their grades to see who is better. In severe cases, the pressure to perform in some countries is so high that it can result in stigmatization of intellectually deficient students, or even suicide as a consequence of failing the exams; Japan being a prime example (see Education in Japan). This has resulted in critical re-evaluation of examinations as a whole by educationalists[citation needed]. Critics of competition (as opposed to excellence) as a motivating factor in education systems, such as Alfie Kohn, assert that competition actually has a net negative influence on the achievement levels of students, and that it "turns all of us into losers" (Kohn 1986). Competitions also make up a large proponent of extracurricular activities in which students participate. Such competitions include TVO's broadcast Reach for the Top competition, FIRST Robotics, Duke Annual Robo-Climb Competition (DARC) and the University of Toronto Space Design Contest. In Texas, the University Interscholastic League (UIL) has 22 High School-level contests and 18 elementary and Junior High in subjects ranging from accounting to science to ready writing.

[edit] Literature Literary competitions, such as contests sponsored by literary journals, publishing houses and theaters, have increasingly become a means for aspiring writers to gain recognition. Prestigious awards for fiction include those sponsored by the Missouri Review, Boston Review and Southwest Review. The Albee Award, sponsored by the Yale Drama Series, is among the most prestigious playwriting awards. Charging fees for literary competitions is extremely controversial. Some writers view fees as a form of exploitation that takes advantage of aspiring authors and playwrights. However, fee-based contests also have strong supporters who argue that these competitions offer rare opportunities for young writers to have their voices heard at a time when access to major agents and editors has grown increasingly limited. [7]

[edit] Biology and ecology Main article: Competition (biology)

Competition within and between species is an important topic in biology, specifically in the field of ecology. Competition between members of a species ("intraspecific") is the driving force behind evolution and natural selection; the competition for resources such as food, water, territory, and sunlight results in the ultimate survival and dominance of the variation of the species best suited for survival. Competition is also present between species ("interspecific"). A limited amount of resources are available, and several species may depend on these resources. Thus, each of the species competes with the others to gain access to the resources. As a result, species less suited to compete for the resources must either adapt or die out. According to evolutionary theory, this competition within and between species for resources plays a critical role in natural selection. For example, a smaller tree will receive less sunlight than an adjacent tree which is larger than it in a rainforest. The larger tree is competing with the smaller one for the same sunlight.

[edit] The study of competition Competition has been studied in several fields, including psychology, sociology and anthropology. Social psychologists, for instance, study the nature of competition. They investigate the natural urge of competition and its circumstances. They also study group dynamics, to detect how competition emerges and what its effects are. Sociologists, meanwhile, study the effects of competition on society as a whole. In addition, anthropologists study the history and prehistory of competition in various cultures. They also investigate how competition manifested itself in various cultural settings in the past, and how competition has developed over time.

[edit] Competitiveness Main article: Competitiveness Many philosophers and psychologists have identified a trait in most living organisms which can drive the particular organism to compete. This trait, unsurprisingly called competitiveness, is viewed as an innate biological trait which coexists along with the urge for survival. Competitiveness, or the inclination to compete, though, has become synonymous with aggressiveness and ambition in the English language. More advanced civilizations integrate aggressiveness and competitiveness into their interactions, as a way to distribute resources and adapt. Most plants compete for higher spots on trees to receive more sunlight. However, Stephen Jay Gould and others have argued that as one ascends the evolutionary hierarchy, competitiveness (the survival instinct) becomes less innate, and more a learned behavior. The same could be said for co-operation: in humans, at least, both co-operation and competition are considered learned behaviors, because the human species learns to adapt to environmental pressures. Consequently, if survival requires competitive behaviors, the individual will compete, and if survival requires co-operative behaviors, the individual will co-operate. In the case of humans, therefore, aggressiveness may be an innate characteristic, but a preson need not be competitive at the same time, for instance when scaling a cliff. On the other hand, humans seem also to have a nurturing instinct, to protect newborns and the weak. While that does not necessitate co-operative behavior, it does help. The term also applies to econometrics. Here, it is a comparative measure of the ability and performance of a firm or sub-sector to sell and produce/supply goods and/or services in a given market. The two academic bodies of thought on the assessment of competitiveness are the Structure Conduct Performance Paradigm and the more contemporary New Empirical Industrial Organisation model. Predicting changes in the competitiveness of business sectors is becoming an integral and explicit step in public policymaking. Within capitalist economic systems, the drive of enterprises is to maintain and improve their own competitiveness.

[edit] Hypercompetitiveness The tendency toward extreme, unhealthy competition has been termed hypercompetitive. This concept originated in Karen Horney's theories on neurosis; specifically, the highly aggressive personality type which is characterized as "moving against people". In her view, some people have a need to compete and win at all costs as a means of maintaining their self-worth. These individuals are likely to turn any activity into a competition, and they will feel threatened if they find themselves losing. Researchers have found that men and women who score high on the trait of hypercompetitiveness are more narcissistic and less psychologically healthy than those who score low on the trait [8]. Hypercompetitive individuals generally believe that "winning isn't everything; it's the only thing".

[edit] See also Look up competition, competitor in Wiktionary, the free dictionary. • • • • • • • • • • • • •

Biological interaction Competition regulator Competitor analysis Cooperation Cooperative Ecological model of competition Imperfect competition Microeconomics Monopolistic competition Perfect competition Planned economy Zero-profit condition Zero-sum

[edit] References

Music From Wikipedia, the free encyclopedia

Jump to: navigation, search This article or section deals primarily with Europe and does not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

For other uses, see Music (disambiguation).

Performing arts Major forms Dance · Music · Opera · Theatre

Minor forms Circus Arts Genres Drama · Tragedy · Comedy · Tragicomedy · Romance · Satire · Epic · Lyric

Music is an art form whose medium is sound organized in time. Common elements of music are pitch (which governs melody and harmony), rhythm (and its associated concepts tempo, meter, and articulation), dynamics, and the sonic qualities of timbre and texture. The word derives from Greek μουσική (mousike), "(art) of the Muses".[1] The creation, performance, significance, and even the definition of music vary according to culture and social context. Music ranges from strictly organized compositions (and their recreation in performance), through improvisational music to aleatoric forms. Music can be divided into genres and subgenres, although the dividing lines and relationships between music genres are often subtle, sometimes open to individual interpretation, and occasionally controversial. Within "the arts", music may be classified as a performing art, a fine art, and auditory art. To people in many cultures, music is inextricably intertwined into their way of life. Greek philosophers and ancient Indians defined music as tones ordered horizontally as melodies and vertically as harmonies. Common sayings such as "the harmony of the spheres" and "it is music to my ears" point to the notion that music is often ordered and pleasant to listen to. However, 20th-century composer John Cage thought that any sound can be music, saying, for example, "There is no noise, only sound."[2] According to musicologist Jean-Jacques Nattiez, "the border between music and noise is always culturally defined— which implies that, even within a single society, this border does not always pass through the same place; in short, there is rarely a consensus.… By all accounts there is no single and intercultural universal concept defining what music might be, except that it is 'sound through time'."[3]

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1 History o 1.1 Prehistoric eras and antiquity o 1.2 Western cultures 2 Non-Western Classical traditions 3 Performance o 3.1 Aural tradition o 3.2 Ornamentation 4 Production o 4.1 Composition o 4.2 Notation o 4.3 Improvisation o 4.4 Theory 5 Cognition 6 Sociology 7 Media and technology o 7.1 Internet

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8 Business 9 Education o 9.1 Non-professional o 9.2 Academia o 9.3 Ethnomusicology 10 Music therapy 11 See also 12 References 13 Further reading

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History Main article: History of music

Prehistoric eras and antiquity The development of music among humans must have taken place against the backdrop of natural sounds such as birdsong and the sounds other animals use to communicate.[citation needed] Prehistoric music is the name which is given to all music produced in preliterate cultures.[citation needed][4]Ancient music can only be imagined by scholars, based on findings from a range of paleolithic sites, such as bones in which lateral holes have been pierced: these are usually identified as flutes,[5] blown at one end like the Japanese shakuhachi. The earliest written records of musical expression are to be found in the Samaveda of India and in 4,000 year old cuneiform from Ur.[citation needed] Instruments, such as the seven-holed flute and various types of stringed instruments have been recovered from the Indus Valley Civilization archaeological sites. [6]

India has one of the oldest musical traditions in the world—references to Indian classical music (marga) can be found in the ancient scriptures of the Hindu tradition, the Vedas. The traditional music of China has a history stretching for around three thousand years. Music was an important part of cultural and social life in Ancient Greece: mixed-gender choruses performed for entertainment, celebration and spiritual ceremonies; musicians and singers had a prominent role in ancient Greek theater In the 9th century, the Arab scholar al-Farabi wrote a book on music titled Kitab al-Musiqi al-Kabir ("Great Book of Music"). He played and invented a variety of musical instruments and devised the Arab tone system of pitch organisation, which is still used in Arabic music.[7]

Western cultures During the Medieval music era (500-1400), the only European repertory which has survived from before about 800 is the monophonic liturgical plainsong of the Roman Catholic Church, the central tradition of which was called Gregorian chant. Alongside these traditions of sacred and church music there existed a vibrant tradition of secular song. From the Renaissance music era (1400-1600), much of the surviving music of 14th century Europe is secular. By the middle of the 15th century, composers and singers used a smooth polyphony for sacred musical compositions. The introduction of commercial printing helped to disseminate musical styles more quickly and across a larger area.

Allegory of Music, by Filippino Lippi The era of Baroque music (1600-1750) began when the first operas were written and when contrapuntal music became prevalent. German Baroque composers wrote for small ensembles including strings, brass, and woodwinds, as well as choirs, pipe organ, harpsichord, and clavichord. During the Baroque period, several major music forms were defined that lasted into later periods when they were expanded and evolved further, including the fugue, the invention, the sonata, and the concerto.[8] The music of the Classical period (1750-1800) is characterized by homophonic texture, often featuring a prominent melody with accompaniment. These new melodies tended to be almost voice-like and singable. The now popular instrumental music was dominated by further evolution of musical forms initially defined in the Baroque period: the sonata, and the concerto, with the addition of the new form, the symphony. Joseph Haydn and Wolfgang Amadeus Mozart are among the central figures of the Classical period. In 1800, the Romantic era (1800-1890s) in music developed, with Ludwig van Beethoven and Franz Schubert as transitional composers who introduced a more dramatic, expressive style. During this era, existing genres, forms, and functions of music were developed, and the emotional and expressive qualities of music came to take precedence over technique and tradition. The late 19th century saw a dramatic expansion in the size of the orchestra, and in the role of concerts as part of urban society. Later Romantic composers created complex and often much longer musical works. They used more complex chords and used more dissonance to create dramatic tension. With 20th century music, there was a vast increase in music listening as the radio gained popularity and phonographs were used to replay and distribute music. The focus of art music was characterized by exploration of new rhythms, styles, and sounds. Igor Stravinsky, Arnold Schoenberg, and John Cage were all influential composers in 20th century art music. Jazz evolved and became a significant genre of music over the course of the 20th century, and during the second half of that century, rock music did the same. Jazz is an American musical art form which originated in the beginning of the 20th century in African American communities in the Southern United States from a confluence of African and European music traditions. The style's West African pedigree is evident in its use of blue notes, improvisation, polyrhythms, syncopation, and the swung note.[9] From its early development until the present, jazz has also incorporated music from 19th and 20th century American popular music.[10] Jazz has, from its early 20th century inception, spawned a variety of subgenres, ranging from New Orleans Dixieland (1910s) to 1970s and 1980s-era jazz-rock fusion. Rock music is a genre of popular music that developed in the 1960s from 1950s rock and roll, rockabilly, blues, and country music. The sound of rock often revolves around the electric guitar or acoustic guitar, and it uses a strong back beat laid down by a rhythm section of electric bass guitar, drums, and keyboard instruments such as organ, piano, or, since the 1970s, digital synthesizers. Along with the guitar or keyboards, saxophone and blues-style harmonica are used as soloing instruments. In its "purest form", it "has three chords, a strong, insistent back beat, and a catchy melody."[11] In the late 1960s and early 1970s, rock music branched out into different subgenres, ranging from blues rock and jazz-rock fusion to heavy metal and punk rock, as well as the more classical influenced genre of progressive rock.

Non-Western Classical traditions Indian classical music is one of the oldest musical traditions in the world.[12] The Indus Valley civilization has sculptures which show dance[13] and old musical instruments, like the seven holed flute. Various types of stringed instruments and drums have been recovered from Harrappa and Mohenjo Daro by excavations carried out by Sir Mortimer Wheeler.[14] The Rigveda has elements of present Indian music, with a musical notation to denote the metre and the mode of chanting.[15] Indian classical music (marga) is monophonic, and based around a single melody line or raga rhythmically organized through talas. Carnatic music is largely devotional; the majority of the songs are addressed to the Hindu deities. There are a lot of songs emphasising love and other social issues. Hindustani music was also influenced by the Persian performance practices of the Afghan Mughals. Asian music covers the music cultures of Arabia, Central Asia, East Asia, South Asia, and Southeast Asia. Chinese classical music, the traditional art or court music of China, has a history stretching over around three thousand years. It has its own unique systems of musical notation, as well as musical tuning and pitch, musical instruments and styles or musical genres. Chinese music is pentatonic-diatonic, having a scale of twelve notes to an octave (5+7 = 12) as does European-influenced music. Persian music is the music of Persia and Persian language countries: musiqi, the science and art of music, and muzik, the sound and performance of music (Sakata 1983). See also: Music of Iran, Music of Afghanistan, Music of Tajikistan, Music of Uzbekistan). The music of Greece was a major part of ancient Greek theater. In ancient Greece, mixed-gender choruses performed for entertainment, celebration and spiritual reasons. Instruments included the double-reed aulos and the plucked string instrument, the lyre, especially the special kind called a kithara. Music was an important part of education in ancient Greece, and boys were taught music starting at age six. Greek musical literacy created a flowering of development; Greek music theory included the Greek musical modes, eventually became the basis for Western religious music and classical music. Later, influences from the Roman Empire, Eastern Europe and the Byzantine Empire changed Greek music.

Performance Main article: Performance

Chinese Naxi musicians Performance is the physical expression of music. Often, a musical work is performed once its structure and instrumentation are satisfactory to its creators; however, as it gets performed, it can evolve and change. A performance can either be rehearsed or improvised. Improvisation is a musical idea created without premeditation, while rehearsal is vigorous repetition of an idea until it has achieved cohesion. Musicians will sometimes add improvisation to a well-rehearsed idea to create a unique performance. Many cultures include strong traditions of solo and performance, such as in Indian classical music, and in the Western Art music tradition. Other cultures, such as in Bali, include strong traditions of group

performance. All cultures include a mixture of both, and performance may range from improvised solo playing for one's enjoyment to highly planned and organised performance rituals such as the modern classical concert, religious processions, music festivals or music competitions. Chamber music, which is music for a small ensemble with only a few of each type of instrument, is often seen as more intimate than symphonic works.

Aural tradition Many types of music, such as traditional blues and folk music were originally preserved in the memory of performers, and the songs were handed down orally, or aurally (by ear). When the composer of music is no longer known, this music is often classified as "traditional". Different musical traditions have different attitudes towards how and where to make changes to the original source material, from quite strict, to those which demand improvisation or modification to the music. A culture's history may also be passed by ear through song.

Ornamentation Main article: Ornament (music) The detail included explicitly in the music notation varies between genres and historical periods. In general, art music notation from the 17th through the 19th century required performers to have a great deal of contextual knowledge about performing styles. For example, in the 17th and 18th century, music notated for solo performers typically indicated a simple, unornamented melody. However, it was expected that performers would know how to add stylistically-appropriate ornaments such as trills and turns. In the 19th century, art music for solo performers may give a general instruction such as to perform the music expressively, without describing in detail how the performer should do this. It was expected that the performer would know how to use tempo changes, accentuation, and pauses (among other devices) to obtain this "expressive" performance style. In the 20th century, art music notation often became more explicit and used a range of markings and annotations to indicate to performers how they should play or sing the piece. In popular music and jazz, music notation almost always indicates only the basic framework of the melody, harmony, or performance approach; musicians and singers are expected to know the performance conventions and styles associated with specific genres and pieces. For example, the "lead sheet" for a jazz tune may only indicate the melody and the chord changes. The performers in the jazz ensemble are expected to know how to "flesh out" this basic structure by adding ornaments, improvised music, and chordal accompaniment.

Production Main article: Music production Music is composed and performed for many purposes, ranging from aesthetic pleasure, religious or ceremonial purposes, or as an entertainment product for the marketplace. Amateur musicians compose and perform music for their own pleasure, and they do not derive their income from music. Professional musicians are employed by a range of institutions and organisations, including armed forces, churches and synagogues, symphony orchestras, broadcasting or film production companies, and music schools. Professional musicians sometimes work as freelancers, seeking contracts and engagements in a variety of settings.

There are often many links between amateur and professional musicians. Beginning amateur musicians take lessons with professional musicians. In community settings, advanced amateur musicians perform with professional musicians in a variety of ensembles and orchestras. In some cases, amateur musicians attain a professional level of competence, and they are able to perform in professional performance settings. A distinction is often made between music performed for the benefit of a live audience and music that is performed for the purpose of being recorded and distributed through the music retail system or the broadcasting system. However, there are also many cases where a live performance in front of an audience is recorded and distributed (or broadcast).

Composition Main article: Musical composition

An old songbook showing a composition "Composition" is often classed as the creation and recording of music via a medium by which others can interpret it (i.e. paper or sound). Many cultures use at least part of the concept of preconceiving musical material, or composition, as held in western classical music. Even when music is notated precisely, there are still many decisions that a performer has to make. The process of a performer deciding how to perform music that has been previously composed and notated is termed interpretation. Different performers' interpretations of the same music can vary widely. Composers and song writers who present their own music are interpreting, just as much as those who perform the music of others or folk music. The standard body of choices and techniques present at a given time and a given place is referred to as performance practice, where as interpretation is generally used to mean either individual choices of a performer, or an aspect of music which is not clear, and therefore has a "standard" interpretation. In some musical genres, such as jazz and blues, even more freedom is given to the performer to engage in improvisation on a basic melodic, harmonic, or rhythmic framework. The greatest latitude is given to the performer in a style of performing called free improvisation, which is material that is spontaneously "thought of" (imagined) while being performed, not preconceived. Improvised music usually follows stylistic or genre conventions and even "fully composed" includes some freely chosen material. Composition does not always mean the use of notation, or the known sole authorship of one individual. Music can also be determined by describing a "process" which may create musical sounds; examples of this range from wind chimes, through computer programs which select sounds. Music which contains elements selected by chance is called Aleatoric music, and is associated with such composers as John Cage, Morton Feldman, and Witold Lutosławski. Music can be composed for repeated performance or it can be improvised: composed on the spot. The music can be performed entirely from memory, from a written system of musical notation, or some combination of both. Study of composition has traditionally been dominated by examination of methods and practice of Western classical music, but the definition of composition is broad enough to include spontaneously improvised works like those of free jazz performers and African drummers such as the Ewe drummers.

What is important in understanding the composition of a piece is singling out its elements. An understanding of music's formal elements can be helpful in deciphering exactly how a piece is constructed. A universal element of music is how sounds occur in time, which is referred to as the rhythm of a piece of music. When a piece appears to have a changing time-feel, it is considered to be in rubato time, an Italian expression that indicates that the tempo of the piece changes to suit the expressive intent of the performer. Even random placement of random sounds, which occurs in musical montage, occurs within some kind of time, and thus employs time as a musical element.

Notation Main article: Musical notation Notation is the written expression of music notes and rhythms on paper using symbols. When music is written down, the pitches and rhythm of the music is notated, along with instructions on how to perform the music. The study of how to read notation involves music theory, harmony, the study of performance practice, and in some cases an understanding of historical performance methods. Written notation varies with style and period of music. In Western Art music, the most common types of written notation are scores, which include all the music parts of an ensemble piece, and parts, which are the music notation for the individual performers or singers. In popular music, jazz, and blues, the standard musical notation is the lead sheet, which notates the melody, chords, lyrics (if it is a vocal piece), and structure of the music. Scores and parts are also used in popular music and jazz, particularly in large ensembles such as jazz "big bands." In popular music, guitarists and electric bass players often read music notated in tablature (often abbreviated as "tab"), which indicates the location of the notes to be played on the instrument using a diagram of the guitar or bass fingerboard. Tabulature was also used in the Baroque era to notate music for the lute, a stringed, fretted instrument. Notated music is produced as sheet music. To perform music from notation requires an understanding of both the rhythmic and pitch elements embodied in the symbols and the performance practice that is associated with a piece of music or a genre.

Improvisation Musical improvisation is the creation of spontaneous music. Improvisation is often considered an act of instantaneous composition by performers, where compositional techniques are employed with or without preparation. Improvisation is a major part of some types of music, such as blues, jazz, and jazz fusion, in which instrumental performers improvise solos and melody lines. In the Western art music tradition, improvisation was an important skill during the Baroque era and during the Classical era; solo performers and singers would improvise virtuoso cadenzas during concerts. However, in the 20th and 21st century, improvisation played a smaller role in Western Art music.

Theory Main article: Music theory Music theory encompasses the nature and mechanics of music. It often involves identifying patterns that govern composers' techniques. In a more detailed sense, music theory (in the western system) also distills and analyzes the elements of music – rhythm, harmony (harmonic function), melody, structure, and texture. People who study these properties are known as music theorists.

Cognition

Further information: Hearing (sense) and Psychoacoustics

A chamber music group consisting of stringed instrument players, a flutist, and a harpsichordist perform in Salzburg The field of music cognition involves the study of many aspects of music including how it is processed by listeners. Rather than accepting the standard practices of analyzing, composing, and performing music as a given, much research in music cognition seeks instead to uncover the mental processes that underlie these practices. Also, research in the field seeks to uncover commonalities between the musical traditions of disparate cultures and possible cognitive "constraints" that limit these musical systems. Questions regarding musical innateness, and emotional responses to music are also major areas of research in the field. Deaf people can experience music by feeling the vibrations in their body, a process which can be enhanced if the individual holds a resonant, hollow object. A well-known deaf musician is the composer Ludwig van Beethoven, who composed many famous works even after he had completely lost his hearing. Recent examples of deaf musicians include Evelyn Glennie, a highly acclaimed percussionist who has been deaf since age twelve, and Chris Buck, a virtuoso violinist who has lost his hearing. This is relevant because it indicates that music is a deeper cognitive process than unexamined phrases such as, "pleasing to the ear" would suggest. Much research in music cognition seeks to uncover these complex mental processes involved in listening to music, which may seem intuitively simple, yet are vastly intricate and complex.

Sociology

This painting, entitled the "Night Revels of Han Xiza", shows Chinese musicians entertaining guests at a party in a 10th century household.

Music is experienced by individuals in a range of social settings ranging from being alone to attending a large concert. Musical performances take different forms in different cultures and socioeconomic milieus. In Europe and North America, there is often a divide between what types of music are viewed as a "high culture" and "low culture." "High culture" types of music typically include Western art music such as Baroque, Classical, Romantic, and modern-era symphonies, concertos, and solo works, and are typically heard in formal concerts in concert halls and churches, with the audience sitting quietly in seats. Other types of music - including, but not limited to, jazz, blues, soul, and country - are often performed in bars, nightclubs, and theatres, where the audience may be able to drink, dance, and express themselves by

cheering. Until the later 20th century, the division between "high" and "low" musical forms was widely accepted as a valid distinction that separated out better quality, more advanced "art music" from the popular styles of music heard in bars and dance halls. However, in the 1980s and 1990s, musicologists studying this perceived divide between "high" and "low" musical genres argued that this distinction is not based on the musical value or quality of the different types of music.[citation needed] Rather, they argued that this distinction was based largely on the socioeconomic standing or social class of the performers or audience of the different types of music.[citation needed] For example, whereas the audience for Classical symphony concerts typically have above-average incomes, the audience for a rap concert in an inner-city area may have below-average incomes. Even though the performers, audience, or venue where non-"art" music is performed may have a lower socioeconomic status, the music that is performed, such as blues, rap, punk, funk, or ska may be very complex and sophisticated. When composers introduce styles of music which break with convention, there can be a strong resistance from academic music experts and popular culture. Late-period Beethoven string quartets, Stravinsky ballet scores, serialism, bebop-era jazz, hip hop, punk rock, and electronica have all been considered nonmusic by some critics when they were first introduced.[citation needed] Such themes are examined in the sociology of music. The sociological study of music, sometimes called sociomusicology, is often pursued in departments of sociology, media studies, or music, and is closely related to the field of ethnomusicology.

Media and technology Further information: Computer music The music that composers make can be heard through several media; the most traditional way is to hear it live, in the presence, or as one of the musicians. Live music can also be broadcast over the radio, television or the Internet. Some musical styles focus on producing a sound for a performance, while others focus on producing a recording which mixes together sounds which were never played "live". Recording, even of styles which are essentially live, often uses the ability to edit and splice to produce recordings which are considered better than the actual performance. As talking pictures emerged in the early 20th century, with their prerecorded musical tracks, an increasing number of moviehouse orchestra musicians found themselves out of work.[16] During the 1920s live musical performances by orchestras, pianists, and theater organists were common at first-run theaters.[17] With the coming of the talking motion pictures, those featured performances were largely eliminated. The American Federation of Musicians (AFM) took out newspaper advertisements protesting the replacement of live musicians with mechanical playing devices. One 1929 ad that appeared in the Pittsburgh Press features an image of a can labeled "Canned Music / Big Noise Brand / Guaranteed to Produce No Intellectual or Emotional Reaction Whatever"[18] Since legislation introduced to help protect performers, composers, publishers and producers, including the Audio Home Recording Act of 1992 in the United States, and the 1979 revised Berne Convention for the Protection of Literary and Artistic Works in the United Kingdom, recordings and live performances have also become more accessible through computers, devices and Internet in a form that is commonly known as Music-On-Demand. In many cultures, there is less distinction between performing and listening to music, since virtually everyone is involved in some sort of musical activity, often communal. In industrialized countries,

listening to music through a recorded form, such as sound recording or watching a music video, became more common than experiencing live performance, roughly in the middle of the 20th century. Sometimes, live performances incorporate prerecorded sounds. For example, a disc jockey uses disc records for scratching, and some 20th century works have a solo for an instrument or voice that is performed along with music that is prerecorded onto a tape. Computers and many keyboards can be programmed to produce and play Musical Instrument Digital Interface (MIDI) music. Audiences can also become performers by participating in karaoke, an activity of Japanese origin which centres around a device that plays voice-eliminated versions of well-known songs. Most karaoke machines also have video screens that show lyrics to songs being performed; performers can follow the lyrics as they sing over the instrumental tracks.

Internet The advent of the Internet has transformed the experience of music, partly through the increased ease of access to music and the increased choice. Chris Anderson, in his book The Long Tail: Why the Future of Business is Selling Less of More, suggests that while the economic model of supply and demand describes scarcity, the Internet retail model is based on abundance. Digital storage costs are low, so a company can afford to make its whole inventory available online, giving customers as much choice as possible. It has thus become economically viable to offer products that very few people are interested in. Consumers' growing awareness of their increased choice results in a closer association between listening tastes and social identity, and the creation of thousands of niche markets.[19] Another effect of the Internet arises with online communities like YouTube and MySpace. MySpace has made social networking with other musicians easier, and greatly facilitates the distribution of one's music. YouTube also has a large community of both amateur and professional musicians who post videos and comments.[citation needed] Professional musicians also use YouTube as a free publisher of promotional material. YouTube users, for example, no longer only download and listen to MP3s, but also actively create their own. According to Don Tapscott and Anthony D. Williams, in their book Wikinomics, there has been a shift from a traditional consumer role to what they call a "prosumer" role, a consumer who both creates and consumes. Manifestations of this in music include the production of mashes, remixes, and music videos by fans.[20]

Business Main article: Music industry The music industry refers to the business industry connected with the creation and sale of music. It consists of record companies, labels and publishers that distribute recorded music products internationally and that often control the rights to those products. Some music labels are "independent," while others are subsidiaries of larger corporate entities or international media groups. In the 2000s, the increasing popularity of listening to music as digital music files on MP3 players, iPods, or computers, and of trading music on file sharing sites or buying it online in the form of digital files had a major impact on the traditional music business. Many smaller independent CD stores went out of business as music buyers decreased their purchases of CDs, and many labels had lower CD sales. Some companies did well with the change to a digital format, though, such as Apple's iTunes, an online store which sells digital files of songs over the Internet.

Education

Non-professional Main article: Music education The incorporation of music training from preschool to post secondary education is common in North America and Europe. Involvement in music is thought to teach basic skills such as concentration, counting, listening, and cooperation while also promoting understanding of language, improving the ability to recall information, and creating an environment more conducive to learning in other areas.[21] In elementary schools, children often learn to play instruments such as the recorder, sing in small choirs, and learn about the history of Western art music. In secondary schools students may have the opportunity to perform some type of musical ensembles, such as choirs, marching bands, concert bands, jazz bands, or orchestras, and in some school systems, music classes may be available. Some students also take private music lessons with a teacher. Amateur musicians typically take lessons to learn musical rudiments and beginner- to intermediate-level musical techniques. At the university level, students in most arts and humanities programs can receive credit for taking music courses, which typically take the form of an overview course on the history of music, or a music appreciation course that focuses on listening to music and learning about different musical styles. In addition, most North American and European universities have some type of musical ensembles that nonmusic students are able to participate in, such as choirs, marching bands, or orchestras. The study of Western art music is increasingly common outside of North America and Europe, such as the Indonesian Institute of the Arts in Yogyakarta, Indonesia, or the classical music programs that are available in Asian countries such as South Korea, Japan, and China. At the same time, Western universities and colleges are widening their curriculum to include music of non-Western cultures, such as the music of Africa or Bali (e.g. Gamelan music).

Academia Musicology is the study of the subject of music. The earliest definitions defined three sub-disciplines: systematic musicology, historical musicology, and comparative musicology or ethnomusicology. In contemporary scholarship, one is more likely to encounter a division of the discipline into music theory, music history, and ethnomusicology. Research in musicology has often been enriched by crossdisciplinary work, for example in the field of psychoacoustics. The study of music of non-western cultures, and the cultural study of music, is called ethnomusicology. Graduates of undergraduate music programs can go on to further study in music graduate programs. Graduate degrees include the Master of Music, the Master of Arts, the Doctor of Philosophy (PhD) (e.g., in musicology or music theory), and more recently, the Doctor of Musical Arts, or DMA. The Master of Music degree, which takes one to two years to complete, is typically awarded to students studying the performance of an instrument, education, voice or composition. The Master of Arts degree, which takes one to two years to complete and often requires a thesis, is typically awarded to students studying musicology, music history, or music theory. Undergraduate university degrees in music, including the Bachelor of Music, the Bachelor of Music Education, and the Bachelor of Arts (with a major in music) typically take three to five years to complete. These degrees provide students with a grounding in music theory and music history, and many students also study an instrument or learn singing technique as part of their program. The PhD, which is required for students who want to work as university professors in musicology, music history, or music theory, takes three to five years of study after the Master's degree, during which time the student will complete advanced courses and undertake research for a dissertation. The DMAis a relatively new degree that was created to provide a credential for professional performers or composers that want to

work as university professors in musical performance or composition. The DMA takes three to five years after a Master's degree, and includes advanced courses, projects, and performances. In Medieval times, the study of music was one of the Quadrivium of the seven Liberal Arts and considered vital to higher learning. Within the quantitative Quadrivium, music, or more accurately harmonics, was the study of rational proportions. Zoomusicology is the study of the music of non-human animals, or the musical aspects of sounds produced by non-human animals. As George Herzog (1941) asked, "do animals have music?" FrançoisBernard Mâche's Musique, mythe, nature, ou les Dauphins d'Arion (1983), a study of "ornithomusicology" using a technique of Nicolas Ruwet's Language, musique, poésie (1972) paradigmatic segmentation analysis, shows that bird songs are organised according to a repetition-transformation principle. Jean-Jacques Nattiez (1990), argues that "in the last analysis, it is a human being who decides what is and is not musical, even when the sound is not of human origin. If we acknowledge that sound is not organised and conceptualised (that is, made to form music) merely by its producer, but by the mind that perceives it, then music is uniquely human." Music theory is the study of music, generally in a highly technical manner outside of other disciplines. More broadly it refers to any study of music, usually related in some form with compositional concerns, and may include mathematics, physics, and anthropology. What is most commonly taught in beginning music theory classes are guidelines to write in the style of the common practice period, or tonal music. Theory, even that which studies music of the common practice period, may take many other forms. Musical set theory is the application of mathematical set theory to music, first applied to atonal music. Speculative music theory, contrasted with analytic music theory, is devoted to the analysis and synthesis of music materials, for example tuning systems, generally as preparation for composition.

Ethnomusicology Main article: Ethnomusicology In the West, much of the history of music that is taught deals with the Western civilization's art music. The history of music in other cultures ("world music" or the field of "ethnomusicology") is also taught in Western universities. This includes the documented classical traditions of Asian countries outside the influence of Western Europe, as well as the folk or indigenous music of various other cultures. Popular styles of music varied widely from culture to culture, and from period to period. Different cultures emphasised different instruments, or techniques, or uses for music. Music has been used not only for entertainment, for ceremonies, and for practical and artistic communication, but also for propaganda in totalitarian countries. There is a host of music classifications, many of which are caught up in the argument over the definition of music. Among the largest of these is the division between classical music (or "art" music), and popular music (or commercial music - including rock and roll, country music, and pop music). Some genres do not fit neatly into one of these "big two" classifications, (such as folk music, world music, or jazz music). As world cultures have come into greater contact, their indigenous musical styles have often merged into new styles. For example, the United States bluegrass style contains elements from Anglo-Irish, Scottish, Irish, German and African instrumental and vocal traditions, which were able to fuse in the United States' multi-ethnic society. Genres of music are determined as much by tradition and presentation as by the actual music. Some works, like George Gershwin's Rhapsody in Blue, are claimed by both jazz and classical music, while Gershwin's Porgy and Bess and Leonard Bernstein's West Side Story are claimed by both opera and the Broadway musical tradition. Many current music festivals celebrate a particular musical genre.

Indian music, for example, is one of the oldest and longest living types of music, and is still widely heard and performed in South Asia, as well as internationally (especially since the 1960s). Indian music has mainly three forms of classical music, Hindustani, Carnatic, and Dhrupad styles. It has also a large repertoire of styles, which involve only percussion music such as the talavadya performances famous in South India.

Music therapy Main article: Music therapy Music therapy is an interpersonal process in which the therapist uses music and all of its facets—physical, emotional, mental, social, aesthetic, and spiritual—to help clients to improve or maintain their health. In some instances, the client's needs are addressed directly through music; in others they are addressed through the relationships that develop between the client and therapist. Music therapy is used with individuals of all ages and with a variety of conditions, including: psychiatric disorders, medical problems, physical handicaps, sensory impairments, developmental disabilities, substance abuse, communication disorders, interpersonal problems, and aging. It is also used to: improve learning, build self-esteem, reduce stress, support physical exercise, and facilitate a host of other health-related activities. Music has long been used to help people deal with their emotions. In the 17th century, the scholar Robert Burton's The Anatomy of Melancholy argued that music and dance were critical in treating mental illness, especially melancholia.[22] He noted that music has an "excellent power ...to expel many other diseases" and he called it "a sovereign remedy against despair and melancholy". He pointed out that in Antiquity, Canus, a Rhodian fiddler, used music to "make a melancholy man merry, ...a lover more enamoured, a religious man more devout." [23][24][25] In November 2006, Dr. Michael J. Crawford[26] and his colleagues also found that music therapy helped schizophrenic patients.[27] In the Ottoman Empire, mental illnesses were treated with music.[28]

See also Music portal • •

List of basic music topics List of music topics

References

Visual perception From Wikipedia, the free encyclopedia

Visual perception is the ability to interpret information from visible light reaching the eyes. The resulting perception is also known as eyesight, sight or vision. The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive science, neuroscience and molecular biology.

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1 Visual system 2 Study of visual perception o 2.1 Early studies on visual perception o 2.2 Unconscious inference o 2.3 Gestalt theory o 2.4 Analysis of eye-movements 3 The cognitive and computational approaches 4 See also o 4.1 Disorders/Dysfunctions o 4.2 Related disciplines 5 References

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6 External links

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[edit] Visual system Main article: Visual system The visual system in humans allows individuals to assimilate information from the environment. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive

membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of patterns of light into neuronal signals. The lens of the eye focuses light on the photoreceptive cells of the retina, which detect the photons of light and respond by producing neural impulses. These signals are processed in a hierarchical fashion by different parts of the brain, from the retina to the lateral geniculate nucleus, to the primary and secondary visual cortex of the brain.

[edit] Study of visual perception The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what we actually see.

[edit] Early studies on visual perception

The visual dorsal stream (green) and ventral stream (purple) are shown. Much of the human cerebral cortex is involved in vision. There were two major ancient Greek schools, providing a primitive explanation of how vision is carried out in the body. The first was the "emission theory" which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If we saw an object directly it was by 'means of rays' coming out of the eyes and again falling on the object. A refracted image was, however, seen by 'means of rays' as well, which came out of the eyes, traversed through the air, and after refraction, fell on the visible object which was sighted as the result of the movement of the rays from the eye. This theory was championed by scholars like Euclid and Ptolemy and their followers. The second school advocated the so called the 'intromission' approach which sees vision as coming from something entering the eyes representative of the object. With its main propagators Aristotle, Galen and their followers, this theory seems to have touched a little sense on what really vision is, but light did not play any role in this theory and it remained only a speculation lacking any experimental foundation.

Leonardo DaVinci: The eye has a central line and everything that reaches the eye through this central line can be seen distinctly. Ibn al-Haytham (also known as Alhacen or Alhazen), the "father of optics", was the first to reconcile both schools of thought in his influential Book of Optics (1021). He argued that vision is due to light from objects entering the eye, and he developed an early scientific method emphasizing extensive

experimentation in order to prove this. He pioneered the scientific study of the psychology of visual perception, being the first scientist to argue that vision occurs in the brain, rather than the eyes. He pointed out that personal experience has an effect on what people see and how they see, and that vision and perception are subjective. He explained possible errors in vision in detail, and as an example, describes how a small child with less experience may have more difficulty interpreting what he/she sees. For a little child however ugly a mother is, it does not matter to it as the definition of beauty is not that well defined for the little child as it is with any other adult. He also gives an example of an adult that can make mistakes in vision because of how one's experience suggests that he/she is seeing one thing, when he/she is really seeing something else. This can be easily related to the famous saying "beauty lies in the eye of the beholder," which is to say that a flower which may appear beautiful to one person may not appeal that much to another.[1] Al-Haytham carried out many investigations and experiments on visual perception, extended the work of Ptolemy on binocular vision, and commented on the anatomical works of Galen.[2][3] Leonardo DaVinci,1452-1519, was the first to recognize the special optical qualities of the eye. He wrote "The function of the human eye, ... was described by a large number of authors in a certain way. But I found it to be completely different." His main experimental finding was that there is only a distinct and clear vision at the line of sight, the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the modern distinction between foveal vision and peripheral vision.

[edit] Unconscious inference Hermann von Helmholtz is often credited with the first study of visual perception in modern times. Helmholtz examined the human eye and concluded that it was, optically, rather poor. The poor quality information gathered via the eye seemed to him to make vision impossible. He therefore concluded that vision could only be the result of some form of unconscious inferences: a matter of making assumptions and conclusions from incomplete data, based on previous experiences. Inference requires prior experience of the world: examples of well-known assumptions - based on visual experience - are: • • •

light comes from above objects are normally not viewed from below faces are seen (and recognized) upright [4]

The study of visual illusions (cases when the inference process goes wrong) has yielded much insight into what sort of assumptions the visual system makes. Another type of the unconscious inference hypothesis (based on probabilities) has recently been revived in so-called Bayesian studies of visual perception. Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a perception from sensory data. Models based on this idea have been used to describe various visual subsystems, such as the perception of motion or the perception of depth.[5][6]

[edit] Gestalt theory Main article: Gestalt psychology Gestalt psychologists working primarily in the 1930s and 1940s raised many of the research questions that are studied by vision scientists today.

The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. Gestalt is a German word that translates to "configuration or pattern". According to this theory, there are six main factors that determine how we group things according to visual perception: Proximity, Similarity, Closure, Symmetry, Common fate and Continuity. One of the reasons why Gestalt laws have often been disregarded by cognitive psychologists is a lack of understanding the nature of peripheral vision. It is true that visual perception only takes place during fixations. But during fixations not only the high definition foveal vision at the fixation point, but also the peripheral vision is functioning. Due to its lack of acuity and relative independence of eye position (due to its extreme wide angle) it is an image compressing system. While foveal vision is very slow (only 3 to 4 high quality telescopic images per second), peripheral vision is very inaccurate but also very fast (up to 90 images per second - permitting one to see the flicker of the European 50Hz TV images). Elements of the visual field are thus grouped automatically according to laws like Proximity, Similarity, Closure, Symmetry, Common fate and Continuity.

[edit] Analysis of eye-movements

During the 1960s the technical development permitted the continuous registration of eye movements during reading[7] in picture viewing [8] and later in visual problem solving [9] and when headset-cameras became available, also during driving.[10] The picture to the left shows what may happen during the first two seconds of visual inspection. While the background is out of focus, representing the peripheral vision, the first eye movement goes to the boots of the man (just because they are very near the starting fixation and have a reasonable contrast). The following fixations jump from face to face. They might even permit comparisons between faces. It may be concluded that the icon face is a very attractive search icon within the peripheral field of vision. The foveal vision adds detailed information to the peripheral first impression.

[edit] The cognitive and computational approaches The major problem with the Gestalt laws (and the Gestalt school generally) is that they are descriptive not explanatory. For example, one cannot explain how humans see continuous contours by simply stating that the brain "prefers good continuity". Computational models of vision have had more success in explaining visual phenomena and have largely superseded Gestalt theory. More recently, the computational models of visual perception have been developed for Virtual Reality systems - these are closer to real life

situation as they account for motion and activities which populate the real world.[11] Regarding Gestalt influence on the study of visual perception, Bruce, Green & Georgeson conclude: "The physiological theory of the Gestaltists has fallen by the wayside, leaving us with a set of descriptive principles, but without a model of perceptual processing. Indeed, some of their "laws" of perceptual organisation today sound vague and inadequate. What is meant by a "good" or "simple" shape, for example?" [12] In the 1980s David Marr developed a multi-level theory of vision, which analysed the process of vision at different levels of abstraction. In order to focus on the understanding of specific problems in vision, he identified (with Tomaso Poggio) three levels of analysis: the computational, algorithmic and implementational levels. The computational level addresses, at a high level of abstraction, the problems that the visual system must overcome. The algorithmic level attempts to identify the strategy that may be used to solve these problems. Finally, the implementational level attempts to explain how these problems are overcome in terms of the actual neural activity necessary. Marr suggested that it is possible to investigate vision at any of these levels independently. Marr described vision as proceeding from a two-dimensional visual array (on the retina) to a three-dimensional description of the world as output. His stages of vision include: •

•

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a 2D or primal sketch of the scene, based on feature extraction of fundamental components of the scene, including edges, regions, etc. Note the similarity in concept to a pencil sketch drawn quickly by an artist as an impression. a 2-1/2 D sketch of the scene, where textures are acknowledged, etc. Note the similarity in concept to the stage in drawing where an artist highlights or shades areas of a scene, to provide depth. a 3 D model, where the scene is visualized in a continuous, 3-dimensional map.[13]

Marr unfortunately died of leukemia in Cambridge, Massachusetts at the age of 35, but his theory provides an important framework for the continued investigation of vision.

[edit] See also • • • •

Color vision Motion perception Depth perception Visual illusion

[edit] Disorders/Dysfunctions • • • •

Achromatopsia Color blindness Scotopic Sensitivity Syndrome Astigmatism

[edit] Related disciplines • •

Psychophysics Neuroscience

• • •

Cognitive science Optometry Ophthalmology

[edit] References

Road From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Road (disambiguation). "Thoroughfare" redirects here. For other uses, see Thoroughfare (disambiguation). "Roadway" redirects here. For the transportation holding company, see Roadway Services. For merged transportation company, see YRC Worldwide.

The St. Gotthard Pass road with hairpin turns in the Swiss Alps

Interstate 80, the second-longest U.S. Interstate highway, runs from California to New Jersey

Castle Roads, in Bermuda. An example of the maritime application of the word roads. A road is an identifiable route, way or path between places.[1] Roads are typically smoothed, paved, or otherwise prepared to allow easy travel;[2] though they need not be, and historically many roads were simply recognizable routes without any formal construction or maintenance.[3] The term was also commonly used to refer to roadsteads, waterways that lent themselves to use by shipping. Notable examples being Hampton Roads, in Virginia, and Castle Roads, in Bermuda (also formerly in Virginia). In urban areas roads may diverge through a city or village and be named as streets, serving a dual function as urban space easement and route.[4] Economics and society depend heavily on efficient roads. In the European Union (EU) 44% of all goods are moved by trucks over roads and 85% of all persons are transported by cars, buses or coaches on roads.[5] The United States has the largest network of roadways of any country with 6,430,366 km (2005). India has the second largest road system in the world with 3,383,344 km (2002). People's Republic of China is third with 1,870,661 km of roadway (2004).[6] When looking only at expressways the National Trunk Highway System (NTHS) in People's Republic of China has a total length of 45,000 km at the end of 2006, second only to the United States with 90,000 km in 2005.[7][8]

Contents [hide] •

1 History

• • • •

o 1.1 Historical road construction dating to 4000 BC 2 Road transport economics 3 Environmental aspects 4 Driving on the right or the left 5 Construction o 5.1 Duplication 6 Maintenance 7 Terminology 8 See also 9 References

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10 External links

• • • •

[edit] History See also: History of road transport

A Greek street from the 3rd to 4th century BC in Velia, Italy. The Porta Rosa was the main street of Elea. It is paved with limestone blocks, with a gutter for the drainage of rain water.

A paved Roman road in Pompeii. That the first pathways were the trails made by animals has not been universally accepted, arguing that animals do not follow constant paths.[3] Others believe that some roads originated from humans following animal trails.[9][10] The Icknield Way is given as an example of this type road origination, where man and animal both selected the same natural line.[11] By about 10,000 BC, rough pathways were used by human travelers.[3]

[edit] Historical road construction dating to 4000 BC •

Stone paved streets are found in the city of Ur in the Middle East dating back to 4000 BC[3]

•

Corduroy roads (log roads) are found dating to 4,000 BC in Glastonbury, England[3]

•

The timber trackway; Sweet Track causeway in England, is one of the oldest engineered roads discovered and the oldest timber trackway discovered in Northern Europe. Built in winter 3807 BC or spring 3806 BC, tree-ring dating (Dendrochronology) enabled very precise dating. It has been claimed to be the oldest road in the world.[12][13]

•

Brick paved streets were used in India as early as 3000 BC[3]

•

In 500 BC, Darius I the Great started an extensive road system for Persia (Iran), including the famous Royal Road which was one of the finest highways of its time.[14] The road remained in use after Roman times.

•

In ancient times, transport by river was far easier and faster than transport by road,[13] especially considering the cost of road construction and the difference in carrying capacity between carts and river barges. A hybrid of road transport and ship transport beginning in about 1740 is the horsedrawn boat in which the horse follows a cleared path along the river bank.[15][16]

•

From about 312 BC, the Roman Empire built straight[17] strong stone Roman roads throughout Europe and North Africa, in support of its military campaigns. At its peak the Roman Empire was connected by 29 major roads moving out from Rome and covering 78,000 kilometers or 52,964 Roman miles of paved roads.[13]

•

In the 700s AD, many roads were built throughout the Arab Empire. The most sophisticated roads were those of the Baghdad, Iraq, which were paved with tar in the 8th century. Tar was derived from petroleum, accessed from oil fields in the region, through the chemical process of destructive distillation.[18]

•

In the 1600s road construction and maintenance in Britain was traditionally done on a local parish basis.[13] This resulted in a poor and variable state of roads. To remedy this, the first of the "Turnpike Trusts" was established around 1706, to build good roads and collect tolls from passing vehicles. Eventually there were approximately 1,100 Trusts in Britain and some 36,800 km of engineered roads.[13] The Rebecca Riots in Carmarthenshire and Rhayader from 1839 to 1844 contributed to a Royal Commission leading to the demise of the system in 1844.[19]

[edit] Road transport economics Main article: Transport economics

A road in Mumbai, India. Most of the roads across the world are built and maintained by the public sector

The Transfăgărăşan in Romania, first built as a military road. Transport economics is a branch of economics that deals with the allocation of resources within the transport sector and has strong linkages with civil engineering. Transport economics differs from some other branches of economics in that the assumption of a spaceless, instantaneous economy does not hold. People and goods flow over networks at certain speeds. Demands peak. Advanced ticket purchase is often induced by lower fares. The networks themselves may or may not be competitive. A single trip (the final good from the point-of-view of the consumer) may require bundling the services provided by several firms, agencies and modes. Although transport systems follow the same supply and demand theory as other industries, the complications of network effects and choices between non-similar goods (e.g. car and bus travel) make estimating the demand for transportation facilities difficult. The development of models to estimate the likely choices between the non-similar goods involved in transport decisions "discrete choice" models led to the development of the important branch of econometrics, and a Nobel Prize for Daniel McFadden.[20] In transport, demand can be measured in numbers of journeys made or in total distance traveled across all journeys (e.g. passenger-kilometres for public transport or vehicle-kilometres of travel (VKT) for private transport). Supply is considered to be a measure of capacity. The price of the good (travel) is measured using the generalised cost of travel, which includes both money and time expenditure. The effect of increases in supply (capacity) are of particular interest in transport economics (see induced demand), as the potential environmental consequences are significant. Road building and maintenance is an area of economic activity that remains dominated by the public sector (though often through private contractors).[21] Roads (except those on private property that are not accessible to the general public) are typically paid for by taxes (often raised through levies on fuel),[22] though some public roads, especially freeways are funded by tolls.[23]

[edit] Environmental aspects

Road in Kaluga Oblast, Russia Motor vehicle traffic on roads generate noise pollution especially at higher operating speeds, near intersections and on uphill sections. Therefore, considerable noise health effects are expected from road

systems used by large numbers of motor vehicles. Noise mitigation strategies exist to reduce sound levels at nearby sensitive receptors. The idea that road design could be influenced by acoustical engineering considerations first arose about 1973.[24] Motor vehicles operating on roads contribute emissions, particularly for congested city street conditions and other low speed circumstances. Of particular concern are particulate emmissions from diesel engines. Concentrations of air pollutants and adverse respiratory health effects are greater near the road than at some distance away from the road. [25] Road dust dust kicked up by vehicles may trigger allergic reactions. [26]

De-icing chemicals and sand can run off into roadsides. Road salts (primarily chlorides of sodium, calcium or magnesium) can be toxic to sensitive plants and animals. Sand can alter stream bed environments, causing stress for the plants and animals that live there. Traffic can grind sand into fine particulates and contribute to air pollution.

[edit] Driving on the right or the left Main article: Driving on the left or right

A sign on Australia's Great Ocean Road reminding foreign motorists to keep left. Traffic flows on the right or on the left side of the road depending on the country.[27] In countries where traffic flows on the right, traffic signs are mostly on the right side of the road, roundabouts and traffic circles go counter-clockwise, and pedestrians crossing a two-way road should watch out for traffic from the left first.[28] In countries where traffic flows on the left, the reverse is true. About 34% of the world by population drive on the left, and 66% keep right. By roadway distances, about 28% drive on the left, and 72% on the right,[29] even though originally most traffic drove on the left worldwide.[30]

[edit] Construction It has been suggested that Carriageway be merged into this article or section. (Discuss)

Surveyor at work with a leveling instrument.

Asphalt layer and roller Road construction requires the creation of a continuous right-of-way, overcoming geographic obstacles and having grades low enough to permit vehicle or foot travel.[31] (pg15) and may be required to meet standards set by law[32] or official guidelines.[33] The process is often begun with the removal of earth and rock by digging or blasting, construction of embankments, bridges and tunnels, and removal of vegetation (this may involve deforestation) and followed by the laying of pavement material. A variety of road building equipment is employed in road building.[34] [35] After design, approval, planning, legal and environmental considerations have been addressed alignment of the road is set out by a surveyor. [17] The Radii and gradient are designed and staked out to best suit the natural ground levels and minimize the amount of cut and fill.[33] (page34) Great care is taken to preserve reference Benchmarks [33] (page59) Roadways are designed and built for primary use by vehicular and pedestrian traffic. Storm drainage and environmental considerations are a major concern. Erosion and sediment controls are constructed to prevent detrimental effects. Drainage lines are laid with sealed joints in the road easement with runoff coefficients and characteristics adequate for the land zoning and storm water system. Drainage systems must be capable of carrying the ultimate design flow from the upstream catchment with approval for the outfall from the appropriate authority to a watercourse, creek, river or the sea for drainage discharge. [33] (page38 to 40)

A Borrow pit (source for obtaining fill, gravel, and rock) and a water source should be located near or in reasonable distance to the road construction site. Approval from local authorities may be required to draw water or for working (crushing and screening) of materials for construction needs. The top soil and vegetation is removed from the borrow pit and stockpiled for subsequent rehabilitation of the extraction area. Side slopes in the excavation area not steeper than one vertical to two horizontal for safety reasons. [33] (page 53 to 56 )

Road construction on Marquette Avenue in Minneapolis, Minnesota, USA Old road surfaces, fences, and buildings may need to be removed before construction can begin. Trees in the road construction area may be marked for retention. These protected trees should not have the topsoil within the area of the tree's drip line removed and the area should be kept clear of construction material and equipment. Compensation or replacement may be required if a protected tree is damaged. Much of the vegetation may be mulched and put aside for use during reinstatement. The topsoil is usually stripped and stockpiled nearby for rehabilitation of newly constructed embankments along the road. Stumps and roots are removed and holes filled as required before the earthwork begins. Final rehabilitation after road construction is completed will include seeding, planting, watering and other activities to reinstate the area to be consistent with the untouched surrounding areas.[33] (page 66 to 67 ) Processes during earthwork include excavation, removal of material to spoil, filling, compacting, construction and trimming. If rock or other unsuitable material is discovered it is removed, moisture content is managed and replaced with standard fill compacted to 90% relative compaction. Generally blasting of rock is discouraged in the road bed. When a depression must be filled to come up to the road grade the native bed is compacted after the topsoil has been removed. The fill is made by the "compacted layer method" where a layer of fill is spread then compacted to specifications, the process is repeated until the desired grade is reached.[33] (page 68 to 69 )

Typical pavement stratum for a heavily traveled road General fill material should be free of organics, meet minimum California bearing ratio (CBR) results and have a low plasticity index. Select fill (sieved) should be composed of gravel, decomposed rock or broken rock below a specified Particle size and be free of large lumps of clay. Sand clay fill may also be used.

The road bed must be "proof rolled" after each layer of fill is compacted. If a roller passes over an area without creating visible deformation or spring the section is deemed to comply. [33] (page 70 to 72 ) The completed road way is finished by paving or left with a gravel or other natural surface. The type of road surface is dependent on economic factors and expected usage. Safety improvements like Traffic signs, Crash barriers, Raised pavement markers, and other forms of Road surface marking are installed.

[edit] Duplication When a single carriageway road is converted into dual carriageway by building a second separate carriageway alongside the first, it is usually referred to as duplication[36] or twinning. The original carriageway is changed from two-way to become one-way, while the new carriageway is one-way in the opposite direction. In the same way as converting railway lines from single track to double track, the new carriageway is not always constructed directly alongside the existing carriageway.

[edit] Maintenance

Like all structures, roads deteriorate over time. Deterioration is primarily due to accumulated damage from vehicles, however environmental effects such as frost heaves, thermal cracking and oxidation often contribute.[37] According to a series of experiments carried out in the late 1950s, called the AASHO Road Test, it was empirically determined that the effective damage done to the road is roughly proportional to the 4th power of axle weight .[38] A typical tractor-trailer weighing 80,000 pounds (36.287 t) with 8,000 pounds (3.6287 t) on the steer axle and 36,000 pounds (16.329 t) on both of the tandem axle groups is expected to do 7,800 times more damage than a passenger vehicle with 2,000 pounds (0.907 t) on each axle. Potholes on roads are caused by rain damage and vehicle braking or related construction works. Pavements are designed for an expected service life or design life. In some UK countries the standard design life is 40 years for new bitumen and concrete pavement. Maintenance is considered in the whole life cost of the road with service at 10, 20 and 30 year milestones. [39] Roads can be and are designed for a variety of lives (8-, 15-, 30-, and 60-year designs). When pavement lasts longer then its intended life, it may have been overbuilt, and the original costs may have been too high. When a pavement fails before its intended design life, the owner may have excessive repair and rehabilitation costs. Many concrete pavements built since the 1950s have significantly outlived their intended design lives. [40] Some roads like Chicago, Illinois's "Wacker Drive", a major two-level viaduct in downtown area are being rebuilt with a designed service life of 100 years. [41] Virtually all roads require some form of maintenance before they come to the end of their service life. Pro-active agencies continually monitor road conditions and apply preventive maintenance treatments as needed to prolong the lifespan of their roads. Technically advanced agencies monitior the road network surface condition with sophisticated equipment such as laser/inertial Profilometers. These measurements include road curvature, cross slope, unevenness, roughness, rutting and texture (roads). This data is fed into a pavement management system, which recommends the best maintenance or construction treatment to correct the damage that has occurred. Maintenance treatments for asphalt concrete generally include crack sealing, surface rejuvenating, fog sealing, micro-milling and surface treatments. Thin surfacing preserves, protects and improves the functional condition of the road while reducing the need for routing maintenance, leading to extended service life without increasing structural capacity.[42]

[edit] Terminology

The A22(T) near Summer Hill, East Sussex, England • • • • • • • • • •

• • •

• • •

• •

• •

Alignment (road) - Cross slope/Banking/Superelevation, horizontal and vertical curvature of a road. All-weather road - Unpaved road that is constructed of a material that does not create mud during rainfall. Bollard - Rigid posts that can be arranged in a line to close a road or path to vehicles above a certain width Byway - Highway over which the public have a right to travel for vehicular and other kinds of traffic, but which is used mainly as footpaths and bridleways Bypass Road that avoids or "bypasses" a built-up area, town, or village Bottleneck - Section of a road with a carrying capacity substantially below that of other sections of the same road Botts' dots - Non reflective raised pavement marker used on roads Cat's eye - reflective raised pavement marker used on roads Chicane - Sequence of tight serpentine curves (usually an S-shape curve or a bus stop) in a roadway Chipseal - Road surface composed of a thin layer of crushed stone 'chips' and asphalt emulsion. It seals the surface and protects it from weather, but provides no structural strength. It is cheaper than asphalt concrete or a concrete, in the U.S. it is usually only used on low volume rural roads Corniche - Road on the side of a cliff or mountain, with the ground rising on one side and falling away on the other Curb - Edge where a raised pavement/sidewalk/footpath, road median, or road shoulder meets an unraised street or other roadway. Curb extension - (or also kerb extension, bulb-out, nib, elephant ear, curb bulge and blister) Traffic calming measure, intended to slow the speed of traffic and increase driver awareness, particularly in built-up and residential neighborhoods. Fork - (literally "fork in the road") Type of intersection where a road splits Guard rail - Prevents vehicles from veering off the road into oncoming traffic, crashing against solid objects or falling from a road Green lane - (UK) Unsurfaced road, may be so infrequently used that vegetation colonises freely, hence 'green'. Many green lanes are ancient routes that have existed for millennia, similar to a Byway Interstate Highway System - United States System of Interstate and Defense Highways Median - On divided roads, including expressways, motorways, or autobahns, the central reservation (British English), median (North American English), median strip (North American English and Australian English), neutral ground [Louisiana English] or central nature strip (Australian English) is the area which separates opposing lanes of traffic Mountain pass - Lower point that allows easier access through a range of mountains Milestone - One of a series of numbered markers placed along a road at regular intervals, showing the distance to destinations.

• • • • • • • •

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• •

•

•

•

Pavement - The road regarded as a geoconstruction. Pedestrian crossing - Designated point on a road at which some means are employed to assist pedestrians wishing to cross safely Private highway - Highway owned and operated for profit by private industry Private road - Road owned and maintained by a private individual, organization, or company rather than by a government Public space - Place where anyone has a right to come without being excluded because of economic or social conditions Pullout (layby, pull-off) - A paved area beside a main road where cars can stop temporarily to let another car pass. Ranch road - U.S. road which serves to connect rural and agricultural areas to market towns Road number - Often assigned to a stretch of public roadway. The number chosen is often dependent on the type of road, with numbers differentiating between interstates, motorways, arterial thoroughfares, and so forth Road-traffic safety - Process to reduce the harm (deaths, injuries, and property damage) resulting from crashes of road vehicles traveling on public roads Roadworks - Part or all of the road has to be occupied for work or maintenance relating to the road Roughness - Deviations from a true planar pavement surface, which affects vehicle suspension deflection, dynamic loading, ride quality, surface drainage and winter operations. Roughness have wavelengths ranging from 500 mm up to some 40 m. The upper limit may be as high as 350 m when considering motion sickness aspects; motion sickness is generated by motion with down to 0.1 Hz frequency; in an ambulance car driving 35 m/s (126 km/h), waves with up to 350 m will excite motion sickness. Shoulder - Reserved area by the verge of a road, generally it is kept clear of all traffic State highway - Road numbered by the state, falling below numbered national highways (like U.S. Routes) in the hierarchy OR A road maintained by the state, including nationally-numbered highways Texture (roads) - Deviations from a true planar pavement surface, which affects the interaction between road and tire. Microtexture have wavelengths below 0.5 mm, Macrotexture below 50 mm and Megatexture below 500 mm. Traffic calming - Set of strategies used by urban planners and traffic engineers which aim to slow down or reduce traffic, thereby improving safety for pedestrians and bicyclists as well as improving the environment for residents Traffic light - also known as a traffic signal, stop light, stop-and-go lights, robot or semaphore, is a signaling device positioned at a road intersection, pedestrian crossing, or other location in order to assign right of way to different approaches to an intersection

[edit] See also Roads portal • Corpse roads • Design Manual for Roads and • Habitat fragmentation • Inca road system • Line source • List of roads and highways •

Bridges

List of OECD countries by road network size

[edit] References

• • • • • •

Road movie Roadway air dispersion model Roadway noise Street Strip road Towing

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Trade route

Sea

From Wikipedia, the free encyclopedia

Jump to: navigation, search This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (May 2008)

This article is about the body of water. For other uses, see SEA and seas. For the ancient Jewish unit of volume, see Seah (unit). For the Smirnoff advertising campaign, see Sea (Smirnoff advert) The term sea refers to certain large bodies of water, but there is inconsistency as to its precise definition and application. Most commonly, a sea may refer to a large expanse of saline water connected with an ocean, but it is also used sometimes of a large saline lake that lacks a natural outlet, e.g. the Caspian Sea. Colloquially, the term is used as a synonym for ocean. Additionally, large lakes, such as the Great Lakes, are occasionally referred to as inland seas.

Contents [hide]

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1 International Hydrographic Organization 2 List of seas o 2.1 Atlantic Ocean o 2.2 Arctic Ocean o 2.3 Indian Ocean o 2.4 Pacific Ocean o 2.5 Southern Ocean o 2.6 Landlocked seas 3 Nomenclature 4 Science 5 See also

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6 References

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[edit] International Hydrographic Organization The International Hydrographic Organization (IHO) is the international authority that sets forth nomenclature and definition of bodies of water.[1] The IHO's Limits of Oceans and Seas was first published in 1928, with its current working document the third edition published in 1953.[2] A fourth draft edition was proposed in 1986 but has yet to be ratified due to outstanding issues such as the Sea of Japan naming dispute.

[edit] List of seas [edit] Atlantic Ocean • • • • •

Adriatic Sea Aegean Sea Alboran Sea Argentine Sea Bay of Biscay

[edit] Arctic Ocean • • • • •

Amundsen Gulf Baffin Bay Barents Sea Beaufort Sea Bering Sea

[edit] Pacific Ocean • • • • •

Arafura Sea Banda Sea Bering Sea Bismarck Sea Bohai Sea

[edit] Southern Ocean • • • •

Amundsen Sea Bass Strait Bellingshausen Sea Davis Sea

• • • • • • •

Bay of Bothnia Bay of Campeche Bay of Fundy Baltic Sea Black Sea Bothnian Sea Caribbean Sea

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• •

Celtic Sea Central Baltic Sea Chesapeake Bay English Channel Gulf of Bothnia Gulf of Guinea Gulf of Finland Gulf of Mexico Gulf of Sidra Gulf of St. [edit] Indian Ocean Lawrence Gulf of • Andaman Sea Venezuela Ionian Sea • Arabian Sea Ligurian Sea Irish Sea • Bay of Bengal Marmara Sea Mediterranean • Gulf of Aden Sea Mirtoon Sea • Gulf of Oman North Sea Sea of Azov • Mozambique Sea of Crete Channel Sea of the Hebrides • Persian Gulf Sargasso Sea Thracian Sea • Red Sea

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Tyrrhenian Sea

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Cambridge Bay Chukchi Sea Cold Bay Davis Strait Denmark Strait East Siberian Sea Greenland Sea Hudson Bay James Bay Kara Sea Kara Strait Labrador Sea Laptev Sea Lincoln Sea Norwegian Sea White Sea

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Bohol Sea (Mindanao Sea)

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Great Australian Bight Gulf Saint Vincent Ross Sea Scotia Sea Spencer Gulf Weddell Sea

Camotes Sea • Celebes Sea • Ceram Sea • Chilean Sea • Coral Sea • East China Sea Flores Sea [edit] Landlocked seas Gulf of Alaska Gulf of California • Aral Sea (Sea of Cortés) • Lake Balkhash Gulf of • Caspian Sea Carpentaria • Lake Chad Gulf of Thailand • Lake Chilwa Halmahera Sea • Chott Melrhir Java Sea • Dead Sea Koro Sea • Lake Eyre Molucca Sea • Issyk Kul Philippine Sea • Namtso Salish Sea • Sea of Galilee Savu Sea • Great Salt Lake Sea of Japan • Qinghai Lake Sea of Okhotsk • Salton Sea Seto Inland Sea • Tonle Sap Solomon Sea • Lake Torrens South China Sea • Lake Turkana Sulu Sea Tasman Sea • Lake Van Yellow Sea

Timor Sea

[edit] Nomenclature Some bodies of water that are called "seas" are not actually seas; there are also some seas that are not called "seas". The following is an incomplete list of such potentially confusing names. • • • •

The Sea of Galilee is a small freshwater lake with a natural outlet, which is called Lake Tiberias or Lake Kinneret on modern Israeli maps, but its original name remains in use. The Sea of Cortés is more commonly known as the Gulf of California. The Persian Gulf is a sea. The Dead Sea is actually a lake, as is the Caspian Sea.

[edit] Science The term "sea" has also been used in quantum physics. Dirac sea is an interpretation of the negative energy states that comprises the vacuum.

[edit] See also Wikimedia Commons has media related to: Seas Look up maritime in Wiktionary, the free dictionary. Look up sea in Wiktionary, the free dictionary. • • • • • • • • • •

Oceanography Inlet International Maritime Organization List of places on land with elevations below sea level Pole of inaccessibility: the locations farthest from any coastline Marine debris Sea level Sea level rise Sea salt Seven Seas

[edit] References 1. ^ "IHO Background Information". International Hydrographic Organization (25 August 2004). Retrieved on 2008-05-17. 2. ^ International Hydrographic Conference of 1952 (1953). "Limits of Oceans and Seas: Special publication S-23" (.PDF). Third edition. International Hydrographic Organization. Retrieved on 2008-05-17. Retrieved from "http://en.wikipedia.org/wiki/Sea" Categories: Bodies of water | Seas

Mountain From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Mountain (disambiguation).

Mount Damavand, Iran

Five Finger Mountain, Azerbaijan. A mountain is a landform that stretches above the surrounding land in a limited area, with a peak. A mountain is generally steeper than a hill, but there is no universally accepted standard definition for the height of a mountain or a hill although a mountain usually has an identifiable summit. Mountains cover 64% of Asia, 36% of North America, 25% of Europe, 22% of South America, 17% of Australia, and 3% of Africa. As a whole, 24% of the Earth's land mass is mountainous. 10% of people live in mountainous regions. Most of the world's rivers are fed from mountain sources, and more than half of humanity depends on mountains for water.[1][2] All 50 of the world’s tallest mountains are in Asia. The adjective montane is used to describe mountainous areas and things associated with them. Orology is its specialized field of studies, though the term is mostly replaced by "Mountain studies".

Contents [hide]

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1 Definitions o 1.1 In the United States o 1.2 Height 2 Characteristics 3 Types of mountains 4 Geology 5 See also 6 Gallery

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7 References

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[edit] Definitions

Ben Nevis, a 1344 m (4409 ft) munro, Grampian Mountains, Scotland

Some authorities define a mountain as a peak with a large topographic prominence over a defined value: for example, according to the Britannica Student Encyclopedia, the term "generally refers to rises over 2,000 feet (609.6 m)".[3] This is a widely accepted common usage in the UK; even though the Countryside and Rights of Way Act 2000 gives a statute definition of a mountain as any "land above 600 m".[4] The Encyclopædia Britannica, on the other hand, does not prescribe any height, merely stating that "the term has no standardized geological meaning".[5]

[edit] In the United States In the United States, the U.S. Board on Geographic Names lists hundreds of landscape features under 1,000 feet (305 m) (some as low as 100 feet) named as "mountains." This is true for all parts of the United States, including the west coast where such lofty ranges as the Cascade Mountains dominate. And yet the Board does not attempt to distinguish between such features as mountains, hills, or other prominences, and simply categorizes all of them as summit, regardless of what they are called or how high they are. However, the Board does list and categorize such low mountain ranges as the Mount Tom Range (with a high point of 1,200 feet; 366 m) as range.[1]

[edit] Height

K2, 8,611 metres (28,250 ft), Karakoram Range, Pakistan. The height of a mountain is measured as the elevation of its summit above mean sea level. The Himalayas average 5 km above sea level, while the Andes average 4 km. The highest mountain on land is Everest, 8,848 metres (29,030 ft) in the Himalayas. The shortest mountain is Mount Wycheproof, 42 metres (140 ft) in north west Victoria, Australia. Other definitions of height are possible. The peak that is farthest from the center of the Earth is Chimborazo in Ecuador. At 6,267 metres (20,560 ft) above sea level it is not even the tallest peak in the Andes, but because Chimborazo is very close to the equator and the Earth bulges at the equator, it is 2,150 metres (7,100 ft) further away from the Earth's center than Everest.[6] The peak that rises farthest from its base is Mauna Kea on Hawaii, whose peak is 10,200 metres (33,500 ft) above its base on the floor of the Pacific Ocean.[7] Mount Lamlam on Guam also lays claim to the tallest mountain as measured from it base. Although its peak is only 406 metres (1,330 ft) above sea level, it measures 11,530 metres (37,830 ft) to its base at the bottom of the Marianas Trench.[8]

Even though Everest is the highest mountain on Earth today, there have been much taller mountains in the past. During the Precambrian era, the Canadian Shield once had mountains 12,000 m (39,370 ft)[9] in height that are now eroded down into rolling hills. These formed by the collision of tectonic plates much like the Himalaya and the Rocky Mountains. At 26 kilometres (85,000 ft) (Fraknoi et al., 2004), the tallest known mountain in the solar system is Olympus Mons, located on Mars and is an ancient volcano. Volcanoes have been known to erupt on other planets and moons in our solar system and some of them erupt ice instead of lava (see Cryovolcano).

[edit] Characteristics High mountains, and mountains located closer to the Earth's poles, have elevations that exist in colder layers of the atmosphere. They are consequently often subject to glaciation and erosion through frost action. Such processes produce the popularly recognizable mountain peak shape. Some of these mountains have glacial lakes, created by melting glaciers; for example, there are an estimated 3,000 glacial lakes in Bhutan.

Mount Olympus in Greece.

Alps mountain view in Switzerland Sufficiently tall mountains have very different climatic conditions at the top than at the base, and will thus have different life zones at different altitudes. The flora and fauna found in these zones tend to become isolated since the conditions above and below a particular zone will be inhospitable to those organisms. These isolated ecological systems are known as sky islands and/or microclimates. Alpine forests are forests on mountain sides which attract moisture from the trees, creating a unique ecosystem. Very tall mountains may be covered in ice or snow. Mountains are colder than lower ground, because the Sun heats Earth from the ground up. The Sun's radiation travels through the atmosphere to the ground, where Earth absorbs the heat. Air closest to the Earth's surface is, in general, warmest (see lapse rate for details). Air as high as a mountain is poorly warmed and, therefore, cold.[10] Air temperature normally drops 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) for each 300 meters (1000 feet) of altitude. Mountains are generally less preferable for human habitation than lowlands; the weather is often harsher, and there is little level ground suitable for agriculture. At very high altitudes, there is less oxygen in the

air and less protection against solar radiation (UV). Acute mountain sickness (caused by hypoxia - a lack of oxygen in the blood) affects over half of lowlanders who spend more than a few hours above 3,500 meters (11,483 feet). A number of mountains and mountain ranges of the world have been left in their natural state, and are today primarily used for recreation, while others are used for logging, mining, grazing, or see little use of any sort at all. Some mountains offer spectacular views from their summits, while others are densely wooded. Summit accessibility ranges from mountain to mountain; height, steepness, latitude, terrain, weather, and the presence or lack thereof of roads, lifts, or tramways are all factors that affect accessibility. Hiking, backpacking, mountaineering, rock climbing, ice climbing, downhill skiing, and snowboarding are recreational activities typically enjoyed on mountains. Mountains that support heavy recreational use (especially downhill skiing) are often the locations of mountain resorts.

[edit] Types of mountains

The Matterhorn, the classical pyramidal peak Mountains can be characterized in several ways. Some mountains are volcanoes and can be characterized by the type of lava and eruptive history. Other mountains are shaped by glacial processes and can be characterized by their glaciated features. Still others are typified by the faulting and folding of the Earth's crust, or by the collision of continental plates via plate tectonics (the Himalayas, for instance). Shape and placement within the overall landscape also define mountains and mountainous structures (such as butte and monadnock). Finally, many mountains can be characterized by the type of rock that make up their composition. More information on mountain types can be found in List of mountain types.

[edit] Geology

The Himalayan mountain range with Mount Everest. A mountain is usually produced by the movement of lithospheric plates, either orogenic movement or epeirogenic movement. The compressional forces, isostatic uplift and intrusion of igneous matter forces surface rock upward, creating a landform higher than the surrounding features. The height of the feature makes it either a hill or, if higher and steeper, a mountain. The absolute heights of features termed mountains and hills vary greatly according to an area's terrain. The major mountains tend to occur in long

linear arcs, indicating tectonic plate boundaries and activity. Two types of mountain are formed depending on how the rock reacts to the tectonic forces – block mountains or fold mountains. The compressional forces in continental collisions may cause the compressed region to thicken, so the upper surface is forced upward. In order to balance the weight of the earth surface, much of the compressed rock is forced downward, producing deep "mountain roots" [see the Book of "Earth", Press and Siever page.413]. Mountains therefore form downward as well as upward (see isostasy). However, in some continental collisions part of one continent may simply override part of the others, crumpling in the process. Some isolated mountains were produced by volcanoes, including many apparently small islands that reach a great height above the ocean floor.

Blue Ridge Mountains in Shenandoah National Park, Virginia, USA Block mountains are created when large areas are widely broken up by faults creating large vertical displacements. This occurrence is fairly common. The uplifted blocks are block mountains or horsts. The intervening dropped blocks are termed graben: these can be small or form extensive rift valley systems. This form of landscape can be seen in East Africa, the Vosges, the Basin and Range province of Western North America and the Rhine valley. These areas often occur when the regional stress is extensional and the crust is thinned. The mid-ocean ridges are often referred to as undersea mountain ranges due to their bathymetric prominence. Where rock does not fault it folds, either symmetrically or asymmetrically. The upfolds are anticlines and the downfolds are synclines; in asymmetric folding there may also be recumbent and overturned folds. The Jura mountains are an example of folding. Over time, erosion can bring about an inversion of relief: the soft upthrust rock is worn away so the anticlines are actually lower than the tougher, more compressed rock of the synclines.

[edit] See also • • •

List of mountains List of highest mountains Category:Lists of mountains

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Latin names of mountains

Environment portal Ecology portal • • •

Mountain range and list of mountain ranges Mountaineering List of ski areas and resorts

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List of peaks by prominence

[edit] Gallery

Mount Everest, 8,848 metres (29,030 ft), Himalayas, Nepal.

Mount Feathertop, Mount Kilimanjaro, 1,922 metres (6,310 ft), 5,895 metres Great Dividing Range, (19,340 ft), Tanzania. Victoria, Australia

Northern Appalachian Mountains, Chic-Choc Range, Gaspé Peninsula, Quebec, Canada

Yu Shan (Jade Mountain), 3,952 metres (12,970 ft), Taiwan.

Finsteraarhorn, 4,274 metres (14,020 ft), Bernese Alps, Switzerland.

Pilot Mountain, 738 metres (2,420 ft), Sauratown Mountains, North Carolina, United States

Sugarloaf Mountain, Brazil, 396 metres (1,300 ft), Rio de Janeiro, Brazil.

Table Mountain Cape Town, South Africa

[edit] References

River From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see River (disambiguation). "Riverine" redirects here. For the use of that term in maritime geography, see there.

Blackwood River, Western Australia

This bridge across the Danube River links Hungary with Slovakia.

This is an image of the Comal River in Landa Park, New Braunfels, Texas.

A view across the Brahmaputra from near Sukleswar ghat in Guwahati. A river is a natural stream of water, usually freshwater, flowing toward an ocean, a lake, or another stream. In some cases a river flows into the ground or dries up completely before reaching another body of water. Usually larger streams are called rivers while smaller streams are called creeks, brooks, rivulets, rills, and many other terms, but there is no general rule that defines what can be called a river. Sometimes a river is said to be larger than a creek,[1] but this is not always the case.[2] A river is a component of the water cycle. The water within a river is generally collected from precipitation through surface runoff, groundwater recharge (as seen at baseflow conditions / during periods of lack of precipitation) and release of stored water in natural reservoirs, such as a glacier.

Contents [hide] • • • • • • •

1 Origins 2 Topography 3 Classification 4 Uses 5 Ecology 6 Flooding 7 Flow o 7.1 Direction

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o 7.2 Rate 8 Management 9 Rating systems o 9.1 Gallery 10 See also o 10.1 Crossings o 10.2 Transport 11 References

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12 Further reading

• • •

[edit] Origins

The youthful Tambo River flowing over a slight change in topography

The beginning of a mountain river in the Swiss Alps (Reichenbach in Grosse Scheidegg) A river may have its source in a spring, lake, from damp, boggy landscapes where the soil is waterlogged, from glacial melt, or from surface runoff of precipitation. Almost all rivers are joined by other rivers and streams termed tributaries, the highest of which are known as headwaters. Water may also originate from groundwater sources. Throughout the course of the river, the total volume transported downstream will often be a combination of the free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. From their source, rivers flow downhill, typically terminating in a sea or in a lake, through a confluence. In arid areas rivers sometimes end by losing water to evaporation. River water may also infiltrate into the soil or pervious rock, where it becomes groundwater. Excessive abstraction of water for use in industry, irrigation, etc., can also cause a river to dry before reaching its natural terminus. The mouth, or lower end, of a river is known as its base level. The area drained by a river and its canals is called catchment, catchment basin, drainage basin or watershed. The term "watershed" is also used to mean a boundary between catchments, which is also called a water divide, or in some, continental divide.

[edit] Topography

Amazon River in Brazil The water in a river is usually confined to a channel, made up of a stream bed between banks. In larger rivers there is also a wider floodplain shaped by flood-waters over-topping the channel. Flood plains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry. The term upriver, is referred to as the beginning or source of the river flow regardless of the direction of flow. Therefore, the term down river, is referring to the direction of flow that the river continues in. The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river. Extensive braided rivers are found in only a few regions worldwide, such as the South Island of New Zealand. They also occur on peneplains and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are also quite rare. They have multiple sinuous channels carrying large volumes of sediment. A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. According to Brahm's law (sometimes called Airy's law), the mass of objects that may be flown away by a river is proportional to the sixth power of the river flow speed. Thus, when the speed of flow increases two times, it can transport 64 times larger (i.e. more massive) objects.[3] In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. In U shaped glaciated valleys, the subsequent river valley can often easily be identified by the V shaped channel that it has carved. In the middle reaches where the river may flow over flatter land, meanders may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake or billabong. Rivers that carry large amounts of sediment may develop conspicuous deltas at their mouths, if conditions permit. Rivers whose mouths are in saline tidal waters may form estuaries.

[edit] Classification Although the following classes are a useful way to visualize rivers, there are many other factors at work. Gradient is controlled largely by tectonics, but discharge is controlled largely by climate, and sediment load is controlled by various factors including climate, geology in the headwaters, and the stream gradient.

Leisure activities on the River Avon at Avon Valley Country Park, Keynsham, Bristol, England. A boat giving trips to the public passes a moored private boat. Youthful river a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. (Examples: Brazos River, Trinity River, Ebro River)

Mature river a river with a gradient that is less steep than those of youthful rivers and flows more slowly than youthful rivers. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. (Examples: Mississippi River, St. Lawrence River, Danube River, Ohio River, River Thames) Old river a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. (Examples: Huang He River, Ganges River, Tigris, Euphrates River, Indus River, Nile River) Rejuvenated river a river with a gradient that is raised by tectonic uplift. The straight-line distance from the beginning to the end of most rivers is about one third their actual length.[4][5] The way which a river's characteristics vary between the upper course and lower course of a river is summarized by the Bradshaw model. Most rivers flow on the surface; however subterranean rivers flow underground in caves or caverns. Such rivers are frequently found in remote regions with limestone geologic formations. An intermittent river (or ephemeral river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur due to geologic conditions such as having a highly permeable river bed.

[edit] Uses Rivers have been used as a source of water, for food, for transport, as a defensive barrier, as a source of power to drive machinery, and as a means of disposing of waste. For thousands of years rivers have been used for navigation (The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern pakistan around 3300 BC). Riverine navigation provides the cheapest means of transport and is still used extensively on major rivers of the world like the Amazon the Ganges, the Nile, the Mississippi, and the Indus. In some heavily-forested regions like Scandinavia and Canada, lumberjacks use the river to float felled trees downstream to lumber camps for further processing, saving much effort and cost by transporting the huge heavy logs by natural means. Rivers have been a source of food since pre-history. Apart from being a rich source of fish, rivers indirectly aid cultivation by supplying water for the crops. Rivers sustain their own food chain. They are a major source of fresh water, hence, it is no surprise to find most of the major cities of the world situated on the banks of rivers. Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as Riverwalks. Rivers also provide an easy means of disposing of waste.

Most riverbanks in Japan are used as places for playing, recreation and parties The rocks and gravel generated and moved by rivers are used in construction. The beauty of rivers and their surroundings contributes to tourist income. In upland rivers, rapids with whitewater or even waterfalls occur. Rapids are often used for recreation, such as whitewater kayaking. Fast flowing rivers and waterfalls are harnessed as sources of energy, via watermills and hydroelectric plants. Rivers have been important in determining political boundaries and defending countries. For example, the Danube was a longstanding border of the Roman Empire, and today it forms most of the border between Bulgaria and Romania. The Mississippi in North America and the Rhine in Europe are major east-west boundaries in those continents. The Orange and Limpopo Rivers in southern Africa form the boundaries between provinces and countries along their routes. Ancient Greek historian Megasthenes mentions about River Ganga several times in his work Indika: "India, again, possesses many rivers both large and navigable, which, having their sources in the mountains which stretch along the northern frontier, traverse the level country, and not a few of these, after uniting with each other, fall into the river called the Ganges. Now this river, which at its source is 30 stadia broad, flows from north to south, and empties its waters into the ocean forming the eastern boundary of the Gangaridai, a nation which possesses a vast force of the largest-sized elephants." (Diodorus II.37.)

[edit] Ecology Main article: Lotic ecosystems The flora and fauna of rivers use the aquatic habitats available, from torrential waterfalls through to lowland mires. Although many organisms are restricted to the fresh water in rivers, some, such as salmon and hilsa, have adapted to be able to survive both in rivers and in the sea.

[edit] Flooding Flooding is a natural part of a river's cycle. The majority of the erosion of river channels and the erosion and deposition on the associated floodplains occur during flood stage. Human activity, however, has upset the natural way flooding occurs by walling off rivers, straightening their courses and by draining of natural wetlands.

[edit] Flow [edit] Direction

Some people think that most rivers flow from north to south.[6][7] Rivers in fact flow downhill regardless of direction, often in a complex meandering path involving all directions of the compass.[8][9][10] Few major rivers in the continental U.S. flow north since most of the country is located in the watershed of the Pacific or Atlantic oceans or the Gulf of Mexico, with very few rivers flowing northward toward the Arctic Ocean, Great Lakes, or Hudson Bay. However, thousands of north-flowing rivers exist elsewhere, including such major watercourses as the Nile, Mackenzie, Rhine, Yenisei, Nelson, and Lena. Four of the ten longest river systems of the world flow mainly north.

[edit] Rate Volumetric flow rate, also called volume flow rate and rate of water flow, is the volume of water which passes through a given volume per unit time, measured in cubic meters per second (1 m³/s = 35.51 ft³/s) or cubic feet per second, sometimes gallons per second.

[edit] Management Main article: River engineering Rivers are often managed or controlled to make them more useful, or less disruptive, to human activity. • • • •

Dams or weirs may be built to control the flow, store water, or extract energy. Levees, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways. Canals connect rivers to one another for water transfer or navigation. River courses may be modified to improve navigation, or straightened to increase the flow rate.

River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or

catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life.

[edit] Rating systems • •

International Scale of River Difficulty – The scale is used to rate the challenges of navigation— particularly those with rapids. Class I is the easiest and Class VI is the hardest. Strahler Stream Order – The Strahler Stream Order ranks rivers based on the connectivity and hierarchy of contributing tributaries. Headwaters are first order while the Amazon River is twelfth order. Approximately 80% of the rivers and streams in the world are of the first and second order.

[edit] Gallery

Río Peralonso - El Zulia River Gambia flowing (Norte de Santander), through Niokolokoba National Park Colombia

Bridges are a common way of crossing rivers (Hooghly Zambezi and Victoria Falls (Zambia/Zimbabwe, River, Kolkata, India) Africa)

Hooghly River (Kolkata, This river flows from Heathcote National Park India) Woronora Dam, Sydney.

[edit] See also See also: geography, water cycle, and drainage basin Look up River in Wiktionary, the free dictionary. Wikimedia Commons has media related to: River • • • • • • • • •

Aqueduct Baer's law Canal Drought Hydrology List of river name etymologies List of rivers by average discharge List of rivers by length List of rivers of Africa

• • • • • • • • •

List of rivers of Asia List of rivers of Europe List of rivers of Oceania List of rivers of the Americas List of waterways Mainstem (hydrology) River cruise Rock-cut basin Water dispute

[edit] Crossings • • • •

Bridges Ferries Fords Tunnels

[edit] Transport • • • •

Barge Riverboat Sailing Towpath

[edit] References

Art From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the general concept of art. For the formal categories of different expressive disciplines, see The arts. For other uses, see Art (disambiguation).

The Bath, a painting by Mary Cassatt (1844–1926).

The Café Terrace on the Place du Forum, Arles, at Night, Vincent van Gogh, September 1888. Art is the process or product of deliberately and creatively arranging elements in a way that appeals to the senses or emotions. In its narrow sense, the word art most often refers specifically to the visual arts, including media such as painting, sculpture, and printmaking. However, "the arts" may also encompass a diverse range of human activities, creations, and modes of expression, including music and literature. Aesthetics is the branch of philosophy which studies art. Traditionally, the term art was used to refer to any skill or mastery. This conception changed during the Romantic period, when art came to be seen as "a special faculty of the human mind to be classified with religion and science".[1] Generally, art is a human activity, made with the intention of stimulating thoughts and emotions. Beyond this description, there is no general agreed-upon definition of art. The definition and evaluation of art has become especially problematic since the 20th century. Richard Wollheim distinguishes three approaches: the Realist, whereby aesthetic quality is an absolute value independent of any human view; the Objectivist, whereby it is also an absolute value, but is dependent on general human experience; and the Relativist position, whereby it is not an absolute value, but depends on, and varies with, the human experience of different humans.[2] An object may be characterized by the intentions, or lack thereof, of its creator, regardless of its apparent purpose. A cup, which ostensibly can be used as a container, may be considered art if intended solely as an ornament, while a painting may be deemed craft if mass-produced. Visual art is defined as the arrangement of colors, forms, or other elements "in a manner that affects the sense of beauty, specifically the production of the beautiful in a graphic or plastic medium".[3] The nature of art has been described by Wollheim as "one of the most elusive of the traditional problems of human culture".[4] It has been defined as a vehicle for the expression or communication of emotions and ideas, a means for exploring and appreciating formal elements for their own sake, and as mimesis or representation.[5] Leo Tolstoy identified art as a use of indirect means to communicate from one person to another.[5] Benedetto Croce and R.G. Collingwood advanced the idealist view that art expresses emotions, and that the work of art therefore essentially exists in the mind of the creator.[6][7] The theory of art as form has its roots in the philosophy of Immanuel Kant, and was developed in the early twentieth century by Roger Fry and Clive Bell.[5] Art as mimesis or representation has deep roots in the philosophy of Aristotle. [5]

Contents [hide]

• • • •

1 Usage 2 Theories 3 Purpose of Art o 3.1 Non-Motivated Functions of Art o 3.2 Motivated Functions of Art 4 Classification disputes 5 Controversial art 6 Art, class and value 7 Forms, genres, mediums, and styles 8 History 9 Characteristics o 9.1 Skill and craft o 9.2 Value judgment o 9.3 Communication 10 See also 11 Notes 12 Bibliography 13 Further reading

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14 External links

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• • • • • •

Usage The most common usage of the word "art," which rose to prominence after 1750, is understood to denote skill used to produce an aesthetic result.[8] Britannica Online defines it as "the use of skill and imagination in the creation of aesthetic objects, environments, or experiences that can be shared with others."[9] By any of these definitions of the word, artistic works have existed for almost as long as humankind: from early pre-historic art to contemporary art; however, some theories restrict the concept to modern Western societies.[10] Much has been written about the concept of "art".[11] Where Adorno said in 1970 "It is now taken for granted that nothing which concerns art can be taken for granted any more[...],"[12],[13] The first and broadest sense of art is the one that has remained closest to the older Latin meaning, which roughly translates to "skill" or "craft," and also from an Indo-European root meaning "arrangement" or "to arrange". In this sense, art is whatever is described as having undergone a deliberate process of arrangement by an agent. A few examples where this meaning proves very broad include artifact, artificial, artifice, artillery, medical arts, and military arts. However, there are many other colloquial uses of the word, all with some relation to its etymology. The second and more recent sense of the word art is as an abbreviation for creative art or fine art. Fine art means that a skill is being used to express the artist’s creativity, or to engage the audience’s aesthetic sensibilities, or to draw the audience towards consideration of the finer things. Often, if the skill is being used in a common or practical way, people will consider it a craft instead of art. Likewise, if the skill is being used in a commercial or industrial way, it will be considered Commercial art instead of fine art. On the other hand, crafts and design are sometimes considered applied art. Some art followers have argued that the difference between fine art and applied art has more to do with value judgments made about the art than any clear definitional difference.[14] However, even fine art often has goals beyond pure creativity and self-expression. The purpose of works of art may be to communicate ideas, such as in politically-, spiritually-, or philosophically-motivated art; to create a sense of beauty (see aesthetics); to explore the nature of perception; for pleasure; or to generate strong emotions. The purpose may also be seemingly nonexistent.

Painting by Song Dynasty artist Ma Lin, c. 1250. 24,8 × 25,2 cm. Art can describe several things: a study of creative skill, a process of using the creative skill, a product of the creative skill, or the audience’s experience with the creative skill. The creative arts (art as discipline) are a collection of disciplines (arts) that produce artworks (art as objects) that are compelled by a personal drive (art as activity) and echo or reflect a message, mood, or symbolism for the viewer to interpret (art as experience). Artworks can be defined by purposeful, creative interpretations of limitless concepts or ideas in order to communicate something to another person. Artworks can be explicitly made for this purpose or interpreted based on images or objects. Art is something that stimulates an individual's thoughts, emotions, beliefs, or ideas through the senses. It is also an expression of an idea and it can take many different forms and serve many different purposes. Although the application of scientific theories to derive a new scientific theory involves skill and results in the "creation" of something new, this represents science only and is not categorized as art.

Theories

Fountain by Marcel Duchamp. 1917 In the nineteenth century, artists were primarily concerned with ideas of truth and beauty. The aesthetic theorist John Ruskin, who championed the raw naturalism of J. M. W. Turner, saw art's role as the communication by artifice of an essential truth that could only be found in nature.[15] The arrival of Modernism in the early twentieth century lead to a radical break in the conception of the function of art,[16] and then again in the late twentieth century with the advent of postmodernism. Clement Greenberg's 1960 article "Modernist Painting" defines Modern Art as "the use of characteristic methods of a discipline to criticize the discipline itself".[17] Greenberg originally applied this idea to the Abstract Expressionist movement and used it as a way to understand and justify flat (non-illusionistic) abstract painting:

Realistic, naturalistic art had dissembled the medium, using art to conceal art; modernism used art to call attention to art. The limitations that constitute the medium of painting – the flat surface, the shape of the support, the properties of the pigment — were treated by the Old Masters as negative factors that could be acknowledged only implicitly or indirectly. Under Modernism these same limitations came to be regarded as positive factors, and were acknowledged openly.[17]

After Greenberg, several important art theorists emerged, such as Michael Fried, T. J. Clark, Rosalind Krauss, Linda Nochlin and Griselda Pollock among others. Though only originally intended as a way of understanding a specific set of artists, Greenberg's definition of Modern Art is important to many of the ideas of art within the various art movements of the 20th century and early 21st century. Pop artists like Andy Warhol became both noteworthy and influential through work including and possibly critiquing popular culture, as well as the art world. Certain radical artists of the 1980s, 1990s, and 2000s expanded this technique of self-criticism beyond high art to all cultural image-making, including fashion images, comics, billboards and pornography.

Purpose of Art Art has had an great number of different functions throughout its history, making its purpose difficult to abstract or quantify to any single concept. This does not imply that the purpose of Art is "vague", but that it has had many unique, different, reasons for being created. Some of these functions of Art are provided in the following outline. The different purposes of art may be grouped according to those which are nonmotivated, and those which are motivated (Levi-Strauss).

Non-Motivated Functions of Art The non-motivated purposes of Art are those which are integral to being human, transcend the individual, or do not fulfill a specific external purpose. Aristotle has said, "Imitation, then, is one instinct of our nature." [18] In this sense, Art, as creativity, is something which humans must do by their very nature (i.e. no other species creates art), and is therefore beyond utility. 1. Basic human instinct for harmony, balance, rhythm. Art at this level is not an action or an object, but an internal appreciation of balance and harmony (beauty), and therefore an aspect of being human beyond utility. "Imitation, then, is one instinct of our nature. Next, there is the instinct for 'harmony' and rhythm, meters being manifestly sections of rhythm. Persons, therefore, starting with this natural gift developed by degrees their special aptitudes, till their rude improvisations gave birth to Poetry." -Aristotle [19]

2. Experience of the mysterious. Art provides us with a way to experience ourselves in relation to the universe. This experience may often come unmotivated, as we appreciate art, music or poetry. "The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." -Albert Einstein [20]

3. Expression of the imagination. Art provide a means to express the imagination in non-grammatic ways that are not tied to the formality of spoken or written language. Unlike words, which come in sequences and each of which have a definite meaning, art provides a range of forms, symbols and ideas with meanings that are maleable. "Jupiter's eagle [as an example of art] is not, like logical (aesthetic) attributes of an object, the concept of the sublimity and majesty of creation, but rather something else - something that gives the imagination an

incentive to spread its flight over a whole host of kindred representations that provoke more thought than admits of expression in a concept determined by words. They furnish an aesthetic idea, which serves the above rational idea as a substitute for logical presentation, but with the proper function, however, of animating the mind by opening out for it a prospect into a field of kindred representations stretching beyond its ken." -Immanuel Kant[21]

4. Universal communication. Art allows the individual to express things toward the world as a whole. Earth Artists often create art in remote locations that will never be experienced by another person. The practice of placing a cairn, or pile of stones at the top of a mountain, is an example. (Note: This need not suggest a particular view of God, or religion.) Art created in this way is a form of communication between the individual and the world as a whole. 5. Ritualistic and symbolic functions. In many cultures, art is used in rituals, performances and dances as a decoration or symbol. While these often have no specific utilitarian (motivated) purpose, anthropologists know that they often serve a purpose at the level of meaning within a particular culture. This meaning is not furnished by any one individual, but is often the result of many generations of change, and of a cosmological relationship within the culture. "Most scholars who deal with rock paintings or objects recovered from prehistoric contexts that cannot be explained in utilitarian terms and are thus categorized as decorative, ritual or symbolic, are aware of the trap posed by the term 'art'." -Silva Tomaskova[22]

Motivated Functions of Art The purposes of art which are motivated refer to intentional, conscious actions on the part of the artists or creator. These may be to bring about political change, to comment on an aspect of society, to convey a specific emotion or mood, to address personal psychology, to illustrate another discipline, to (with commercial arts) to sell a product, or simply as a form of communication. 1. Communcation. Art, at its simplest, is a form of communication. As most forms of communication have an intent or goal directed toward another individual, this is a motivated purpose. Illustrative arts, such as scientific illustration, are a form of art as communication. Maps are another example. However, the content need not be scientific. Emotions, moods and feelings are also communicated through art. "[Art is a set of] artefacts or images with symbolic meanings as a means of communication." -Steve Mithen[23]

2. Art as Entertainment. Art may seek to bring about a particular emotion or mood, for the purpose of relaxing or entertaining the viewer. This is often the function of the art industries of Motion Pictures and Video Games. 3. The Avante-Garde. Art for political change. One of the defining functions of early twentieth century art has been to use visual images to bring about political change. The art movements which had this goal - Dadaism, Surrealism, Russian Constructivism, and Abstract Expressionism, among others - are collectively referred to as the avante-garde arts. "By contrast, the realistic attitude, inspired by positivism, from Saint Thomas Aquinas to Anatole France, clearly seems to me to be hostile to any intellectual or moral advancement. I loathe it, for it is made up of mediocrity, hate, and dull conceit. It is this attitude which today gives birth to these ridiculous books, these insulting plays. It constantly feeds on and derives strength from the newspapers and stultifies both science and art by assiduously flattering the lowest of tastes; clarity bordering on stupidity, a dog’s life." -Andre Breton (Surrealism)[24]

4. Art for psychological and healing purposes. Art is also used by art therapists, psychotherapists and clinical psychologists as art therapy. The Diagnostic Drawing Series, for example, is used to determine the personality and emotional functioning of a patient. The end product is not the principal goal in this case, but rather a process of healing, through creative acts, is sought. The resultant piece of artwork may also offer insight into the troubles experienced by the subject and may suggest suitable approaches to be used in more conventional forms of psychiatric therapy. 5. Art for social inquiry, subversion and/or anarchy. While similar to art for political change, subversive or deconstructivist art may seek to question aspects of society without any specific political goal. In this case, the function of art may be simply to criticize some aspect of society.

Spray-paint graffiti on a wall in Rome. Graffiti art and other types of street art are graphics and images that are spray-painted or stencilled on publicly viewable walls, buildings, buses, trains, and bridges, usually without permission. Certain art forms, such as graffiti, may also be illegal when they break laws (in this case vandalism). 6. Art for propaganda, or commercialism. Art is often utilized as a form of propaganda, and thus can be used to subtly influence popular conceptions or mood. In a similar way, art which seeks to sell a product also influences mood and emotion. In both cases, the purpose of art here is to subtly manipulate the viewer into a particular emotional or psychological response toward a particular idea or object. [25] The functions of art described above are not mutually exclusive, as many of them may overlap. For example, art for the purpose of entertainment may also seek to sell a product, i.e. the movie or video game. One of the central challenges of post-modern art (after the 1970s), is that as the world becomes increasingly utilitarian, functional, and market-driven, the presence of the non-motivated arts, or art which is ritualistic or symbolic, becomes increasingly rare.

Classification disputes Main article: Classificatory disputes about art

Image of a horse from the Lascaux caves.

It is common in the history of art for people to dispute whether a particular form or work, or particular piece of work counts as art or not. In fact for much of the past century the idea of art has been to simply challenge what art is. Philosophers of Art call these disputes “classificatory disputes about art.” For example, Ancient Greek philosophers debated about whether or not ethics should be considered the "art of living well". Classificatory disputes in the 20th century included: cubist and impressionist paintings, Duchamp’s Fountain, the movies, superlative imitations of banknotes, propaganda, and even a crucifix immersed in urine. Conceptual art often intentionally pushes the boundaries of what counts as art. New media such as Video games slowly become co-opted by artists and/or recognized as art forms in its own right, though these new classification shifts are not universally adopted and remain the subject of dispute. [26]

Disputes over the nature of art have raged for centuries, and have even resulted in the banning of some forms. Philosopher David Novitz has argued that disagreement about the definition of art are rarely the heart of the problem. Rather, "the passionate concerns and interests that humans vest in their social life" are "so much a part of all classificatory disputes about art" (Novitz, 1996). According to Novitz, classificatory disputes are more often disputes about our values and where we are trying to go with our society than they are about theory proper. For example, when the Daily Mail criticized Hirst's and Emin’s work by arguing "For 1,000 years art has been one of our great civilising forces. Today, pickled sheep and soiled beds threaten to make barbarians of us all" they are not advancing a definition or theory about art, but questioning the value of Hirst’s and Emin’s work.[27] In 1998, Arthur Danto, suggested a thought experiment showing that "the status of an artifact as work of art results from the ideas a culture applies to it, rather than its inherent physical or perceptible qualities. Cultural interpretation (an art theory of some kind) is therefore constitutive of an object’s arthood."[28][29]

Controversial art Theodore Gericault's "Raft of the Medusa" (1820), was a social commentary on a current event, unprecedented at the time. Edouard Manet's "Le Déjeuner sur l'Herbe" (1863), was considered scandalous not because of the nude woman, but because she is seated next to men fully dressed in the clothing of the time, rather than in robes of the antique world. John Singer Sargent's "Madame Pierre Gautreau (Madam X)" (1884), caused a huge uproar over the reddish pink used to color the woman's ear lobe, considered far too suggestive and supposedly ruining the high-society model's reputation.

Leon Golub's Interrogation III (1981) In the twentieth century, Pablo Picasso's Guernica (1937) used arresting cubist techniques and stark monochromatic oils, to depict the harrowing consequences of a contemporary bombing of a small, ancient Basque town. Leon Golub's Interrogation III (1981), depicts a female nude, hooded detainee strapped to a chair, her legs open to reveal her sexual organs, surrounded by two tormentors dressed in everyday clothing. Andres Serrano's Piss Christ (1989) is a photograph of a crucifix, sacred to the Christian religion and representing Christ's sacrifice and final suffering, submerged in a glass of the artist's own urine. The resulting uproar led to comments in the United States Senate about public funding of the arts. In the twenty-first century, Eric Fischl created Tumbling Woman as a memorial to those who jumped or fell to their death in the attacks on the World Trade Center on September 11, 2001. Initially installed at Rockefeller Center in New York City, within a year the work was removed as too disturbing.[30]

Art, class and value

Versailles: Louis Le Vau opened up the interior court to create the expansive entrance cour d'honneur, later copied all over Europe Art has been perceived by some as belonging to some social classes and often excluding others. In this context, art is seen as an upper-class activity associated with wealth, the ability to purchase art, and the leisure required to pursue or enjoy it. For example, the palaces of Versailles or the Hermitage in St. Petersburg with their vast collections of art, amassed by the fabulously wealthy royalty of Europe exemplify this view. Collecting such art is the preserve of the rich, or of governments and institutions. Fine and expensive goods have been popular markers of status in many cultures, and continue to be so today. There has been a cultural push in the other direction since at least 1793, when the Louvre, which had been a private palace of the Kings of France, was opened to the public as an art museum during the French Revolution. Most modern public museums and art education programs for children in schools can be traced back to this impulse to have art available to everyone. Museums in the United States tend to be gifts from the very rich to the masses (The Metropolitan Museum of Art in New York City, for example, was created by John Taylor Johnston, a railroad executive whose personal art collection seeded the museum.) But despite all this, at least one of the important functions of art in the 21st century remains as a marker of wealth and social status.

Performance by Joseph Beuys, 1978 : Everyone an artist — On the way to the libertarian form of the social organism. There have been attempts by artists to create art that can not be bought by the wealthy as a status object. One of the prime original motivators of much of the art of the late 1960s and 1970s was to create art that could not be bought and sold. It is "necessary to present something more than mere objects"[31] said the major post war German artist Joseph Beuys. This time period saw the rise of such things as performance art, video art, and conceptual art. The idea was that if the artwork was a performance that would leave nothing behind, or was simply an idea, it could not be bought and sold. "Democratic precepts revolving around the idea that a work of art is a commodity impelled the aesthetic innovation which germinated in the mid-1960s and was reaped throughout the 1970s. Artists broadly identified under the heading of Conceptual art... substituting performance and publishing activities for engagement with both the material and materialistic concerns of painted or sculptural form... [have] endeavored to undermine the art object qua object."[32] In the decades since, these ideas have been somewhat lost as the art market has learned to sell limited edition DVDs of video works,[33] invitations to exclusive performance art pieces, and the objects left over from conceptual pieces. Many of these performances create works that are only understood by the elite who have been educated as to why an idea or video or piece of apparent garbage may be considered art. The marker of status becomes understanding the work instead of necessarily owning it, and the artwork remains an upper-class activity. "With the widespread use of DVD recording technology in the early 2000s, artists, and the gallery system that derives its profits from the sale of artworks, gained an important means of controlling the sale of video and computer artworks in limited editions to collectors."[34]

Forms, genres, mediums, and styles Main article: The arts The creative arts are often divided into more specific categories that are related to their technique, or medium, such as decorative arts, plastic arts, performing arts, or literature. Unlike scientific fields, art is one of the few subjects that is academically organized according to technique [1]. An artistic medium is the substance or material the artistic work is made from, and may also refers to the technique used. For example, paint is the media used in painting, paper is a media used in drawing. An art form is the specific shape, or quality an artistic expression takes. The media used often influences the form. For example, the form of a sculpture must exist in space in three-dimensions, and respond to gravity. The constraints and limitations of a particular medium are thus called its formal qualities. To

give another example, the formal qualities of painting are the canvas texture, color, and brush texture. The formal qualities of video games are non-linearity, interactivity and virtual presence. The form of a particular work of art is determined by both the formal qualities of the media, and the intentions of the artist. A genre is a set of conventions and styles within a particular media. For instance, well recognized genres in film are western, horror and romantic comedy. Genres in music include death metal and trip hop. Genres in painting include still life, and pastoral landscape. A particular work of art may bend or combine genres but each genre has a recognizable group of conventions, clichés and tropes. (One note: the word genre has a second older meaning within painting; genre painting was a phrase used in the 17th to 19th century to refer specifically to paintings of scenes of everyday life and can still be used in this way.)

Detail of Leonardo da Vinci's Mona Lisa, showing the painting technique of sfumato. An artwork, artist’s, or movement's style is the distinctive method and form that art takes. Any loose brushy, dripped or poured abstract painting is called expressionistic (with a lower case "e" and the "ic" at the end). Often these styles are linked with a particular historical period, set of ideas, and particular artistic movement. So Jackson Pollock is called an Abstract Expressionist. Because a particular style may have a specific cultural meanings, it is important to be sensitive to differences in technique. Roy Lichtenstein's (1923-1997) paintings are not pointillist, despite his uses of dots, because they are not aligned with the original proponents of Pointillism. Lichtenstein used Ben-Day dots: they are evenly-spaced and create flat areas of color. These types of dots, used in halftone printing, were originally used in comic strips and newspapers to reproduce color. Lichtenstein thus uses the dots as a style to question the "high" art of painting with the "low" art of comics - to comment on class distinctions in culture. Lichtenstein is thus associated with the American Pop art movement (1960s). Pointillism is a technique in late Impressionism (1880s), developed especially by the artist Georges Seurat, that employs dots that are spaced in a way to create variation in color and depth in an attempt to paint images that were closer to the way we really see color. Both artists use dots, but the particular style and technique relates to the artistic movement these artists were a part of.

The Great Wave off Kanagawa by Katsushika Hokusai (Japanese, 1760–1849), colored woodcut print. These are all ways of beginning to define a work of art, to narrow it down. "Imagine you are an art critic whose mission is to compare the meanings you find in a wide range of individual artworks. How would you proceed with your task? One way to begin is to examine the materials each artist selected in making an object, image video, or event. The decision to cast a sculpture in bronze, for instance, inevitably effects its meaning; the work becomes something different than if it had been cast in gold or plastic or chocolate, even if everything else about the artwork remained the same. Next, you might examine how the materials in each artwork have become an arrangement of shapes, colors, textures, and lines. These, in turn, are organized into various patterns and compositional structures. In your interpretation, you would comment on how salient features of the form contribute to the overall meaning of the finished artwork. [But in the end] the meaning of most artworks... is not exhausted by a discussion of materials, techniques, and form. Most interpretations also include a discussion of the ideas and feelings the artwork engenders."[35]

History Main article: History of Art

Venus of Willendorf. Art predates history; sculptures, cave paintings, rock paintings, and petroglyphs from the Upper Paleolithic starting roughly 40,000 years ago have been found, but the precise meaning of such art is often disputed because so little is known about the cultures that produced them. The oldest art objects in the world: a series of tiny, drilled snail shells about 75,000yrs old, were discovered in a South African cave. [36]

The great traditions in art have a foundation in the art of one of the great ancient civilizations: Ancient Egypt, Mesopotamia, Persia, India, China, Ancient Greece, Rome, or Arabia (ancient Yemen and Oman). Each of these centers of early civilization developed a unique and characteristic style in their art. Because of the size and duration these civilizations, more of their art works have survived and more of their influence has been transmitted to other cultures and later times. They have also provided the first records of how artists worked. For example, this period of Greek art saw a veneration of the human physical form and the development of equivalent skills to show musculature, poise, beauty and anatomically correct proportions In Byzantine and Gothic art of the Western Middle Ages, art focused on the expression of Biblical and not material truths, and emphasized methods which would show the higher unseen glory of a heavenly world, such as the use of gold in the background of paintings, or glass in mosaics or windows, which also presented figures in idealized, patterned (flat) forms.

The stylized signature of Sultan Mahmud II of the Ottoman Empire was written in Arabic calligraphy. It reads Mahmud Khan son of Abdulhamid is forever victorious. The western Renaissance saw a return to valuation of the material world, and the place of humans in it, and this paradigm shift is reflected in art forms, which show the corporeality of the human body, and the three dimensional reality of landscape.

Landscape of pine valley, by Ming Dynasty artist Chen Hongshou. In the east, Islamic art's rejection of iconography led to emphasis on geometric patterns, calligraphy, and architecture. Further east, religion dominated artistic styles and forms too. India and Tibet saw emphasis on painted sculptures and dance with religious painting borrowing many conventions from sculpture and tending to bright contrasting colors with emphasis on outlines. China saw many art forms flourish, jade carving, bronzework, pottery (including the stunning terracotta army of Emperor Qin), poetry, calligraphy, music, painting, drama, fiction, etc. Chinese styles vary greatly from era to era and are traditionally named after the ruling dynasty. So, for example, Tang Dynasty paintings are monochromatic and sparse, emphasizing idealized landscapes, but Ming Dynasty paintings are busy, colorful, and focus on telling stories via setting and composition. Japan names its styles after imperial dynasties too, and also saw much interplay between the styles of calligraphy and painting. Woodblock printing became important in Japan after the 17th century. The western Age of Enlightenment in the 18th century saw artistic depictions of physical and rational certainties of the clockwork universe, as well as politically revolutionary visions of a post-monarchist world, such as Blake’s portrayal of Newton as a divine geometer, or David’s propagandistic paintings.

This led to Romantic rejections of this in favor of pictures of the emotional side and individuality of humans, exemplified in the novels of Goethe. The late 19th century then saw a host of artistic movements, such as academic art, symbolism, impressionism and fauvism among others. By the 20th century these pictures were falling apart, shattered not only by new discoveries of relativity by Einstein[37] and of unseen psychology by Freud,[38] but also by unprecedented technological development accelerated by the implosion of civilisation in two world wars. The history of twentieth century art is a narrative of endless possibilities and the search for new standards, each being torn down in succession by the next. Thus the parameters of Impressionism, Expressionism, Fauvism, Cubism, Dadaism, Surrealism, etc cannot be maintained very much beyond the time of their invention. Increasing global interaction during this time saw an equivalent influence of other cultures into Western art, such as Pablo Picasso being influenced by African sculpture. Japanese woodblock prints (which had themselves been influenced by Western Renaissance draftsmanship) had an immense influence on Impressionism and subsequent development. Later, African sculptures were taken up by Picasso and to some extent by Matisse. Similarly, the west has had huge impacts on Eastern art in 19th and 20th century, with originally western ideas like Communism and Post-Modernism exerting powerful influence on artistic styles. Modernism, the idealistic search for truth, gave way in the latter half of the 20th century to a realization of its unattainability. Relativity was accepted as an unavoidable truth, which led to the period of contemporary art and postmodern criticism, where cultures of the world and of history are seen as changing forms, which can be appreciated and drawn from only with irony. Furthermore the separation of cultures is increasingly blurred and some argue it is now more appropriate to think in terms of a global culture, rather than regional cultures.

Characteristics Art tends to facilitate intuitive rather than rational understanding, and is usually consciously created with this intention. Fine art intentionally serves no other purpose. As a result of this impetus, works of art are elusive, refractive to attempts at classification, because they can be appreciated in more than one way, and are often susceptible to many different interpretations. In the case of Gericault's Raft of the Medusa, special knowledge concerning the shipwreck that the painting depicts is not a prerequisite to appreciating it, but allows the appreciation of Gericault's political intentions in the piece. Even art that superficially depicts a mundane event or object, may invite reflection upon elevated themes. Traditionally, the highest achievements of art demonstrate a high level of ability or fluency within a medium. This characteristic might be considered a point of contention, since many modern artists (most notably, conceptual artists) do not themselves create the works they conceive, or do not even create the work in a conventional, demonstrative sense. Art has a transformative capacity: confers particularly appealing or aesthetically satisfying structures or forms upon an original set of unrelated, passive constituents.

Skill and craft

Adam. Detail from Michelangelo's fresco in the Cappella Sistina (1511) Art can connote a sense of trained ability or mastery of a medium. Art can also simply refer to the developed and efficient use of a language to convey meaning with immediacy and or depth. Art is an act of expressing our feelings, thoughts, and observations. There is an understanding that is reached with the material as a result of handling it, which facilitates one's thought processes. A common view is that the epithet “art”, particular in its elevated sense, requires a certain level of creative expertise by the artist, whether this be a demonstration of technical ability or an originality in stylistic approach such as in the plays of Shakespeare, or a combination of these two. Traditionally skill of execution was viewed as a quality inseparable from art and thus necessary for its success; for Leonardo da Vinci, art, neither more nor less than his other endeavors, was a manifestation of skill. Rembrandt's work, now praised for its ephemeral virtues, was most admired by his contemporaries for its virtuosity. At the turn of the 20th century, the adroit performances of John Singer Sargent were alternately admired and viewed with skepticism for their manual fluency, yet at nearly the same time the artist who would become the era's most recognized and peripatetic iconoclast, Pablo Picasso, was completing a traditional academic training at which he excelled. A common contemporary criticism of some modern art occurs along the lines of objecting to the apparent lack of skill or ability required in the production of the artistic object. In conceptual art, Marcel Duchamp's "Fountain" is among the first examples of pieces wherein the artist used found objects ("ready-made") and exercised no traditionally recognised set of skills. Tracey Emin's My Bed, or Damien Hirst's The Physical Impossibility of Death in the Mind of Someone Living follow this example and also manipulate the mass media. Emin slept (and engaged in other activities) in her bed before placing the result in a gallery as work of art. Hirst came up with the conceptual design for the artwork but has left most of the eventual creation of many works to employed artisans. Hirst's celebrity is founded entirely on his ability to produce shocking concepts. The actual production in many conceptual and contemporary works of art is a matter of assembly of found objects. However there are many modernist and contemporary artists who continue to excel in the skills of drawing and painting and in creating hands on works of art.

Value judgment

Aboriginal hollow log tombs. National Gallery, Canberra, Australia.

Somewhat in relation to the above, the word art is also used to apply judgments of value, as in such expressions like "that meal was a work of art" (the cook is an artist), or "the art of deception," (the highly attained level of skill of the deceiver is praised). It is this use of the word as a measure of high quality and high value that gives the term its flavor of subjectivity. Making judgments of value requires a basis for criticism. At the simplest level, a way to determine whether the impact of the object on the senses meets the criteria to be considered art, is whether it is perceived to be attractive or repulsive. Though perception is always colored by experience, and is necessarily subjective, it is commonly taken that - that which is not aesthetically satisfying in some fashion cannot be art. However, "good" art is not always or even regularly aesthetically appealing to a majority of viewers. In other words, an artist's prime motivation need not be the pursuit of the aesthetic. Also, art often depicts terrible images made for social, moral, or thought-provoking reasons. For example, Francisco Goya's painting depicting the Spanish shootings of 3rd of May 1808, is a graphic depiction of a firing squad executing several pleading civilians. Yet at the same time, the horrific imagery demonstrates Goya's keen artistic ability in composition and execution and produces fitting social and political outrage. Thus, the debate continues as to what mode of aesthetic satisfaction, if any, is required to define 'art'. The assumption of new values or the rebellion against accepted notions of what is aesthetically superior need not occur concurrently with a complete abandonment of the pursuit of that which is aesthetically appealing. Indeed, the reverse is often true, that in the revision of what is popularly conceived of as being aesthetically appealing, allows for a re-invigoration of aesthetic sensibility, and a new appreciation for the standards of art itself. Countless schools have proposed their own ways to define quality, yet they all seem to agree in at least one point: once their aesthetic choices are accepted, the value of the work of art is determined by its capacity to transcend the limits of its chosen medium in order to strike some universal chord by the rarity of the skill of the artist or in its accurate reflection in what is termed the zeitgeist.

Communication Art is often intended to appeal and connect with human emotion. It can arouse aesthetic or moral feelings, and can be understood as a way of communicating these feelings. Artists express something so that their audience is aroused to some extent, but they do not have to do so consciously. Art explores what is commonly termed as the human condition that is essentially what it is to be human. Effective art often brings about some new insight concerning the human condition either singly or en-mass, which is not necessarily always positive, or necessarily widens the boundaries of collective human ability. The degree of skill that the artist has, will affect their ability to trigger an emotional response and thereby provide new insights, the ability to manipulate them at will shows exemplary skill and determination.

See also • •

List of basic art topics Lives of the Most Excellent Painters, Sculptors, and Architects

Notes

Mathematics From Wikipedia, the free encyclopedia

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"Maths" and "Math" redirect here. For other uses of "Mathematics" or "Math", see Mathematics (disambiguation) and Math (disambiguation).

Euclid, Greek mathematician, 3rd century BC, as imagined by Raphael in this detail from The School of Athens.[1] Mathematics is the academic discipline, and its supporting body of knowledge, that involves the study of such concepts as quantity, structure, space and change. The mathematician Benjamin Peirce called it "the science that draws necessary conclusions".[2] Other practitioners of mathematics maintain that mathematics is the science of pattern, and that mathematicians seek out patterns whether found in numbers, space, science, computers, imaginary abstractions, or elsewhere.[3][4] Mathematicians explore such concepts, aiming to formulate new conjectures and establish their truth by rigorous deduction from appropriately chosen axioms and definitions.[5] Through the use of abstraction and logical reasoning, mathematics evolved from counting, calculation, measurement, and the systematic study of the shapes and motions of physical objects. Knowledge and use of basic mathematics have always been an inherent and integral part of individual and group life. Refinements of the basic ideas are visible in mathematical texts originating in the ancient Egyptian, Mesopotamian, Indian, Chinese, Greek and Islamic worlds. Rigorous arguments first appeared in Greek mathematics, most notably in Euclid's Elements. The development continued in fitful bursts until the Renaissance period of the 16th century, when mathematical innovations interacted with new scientific discoveries, leading to an acceleration in research that continues to the present day.[6] Today, mathematics is used throughout the world as an essential tool in many fields, including natural science, engineering, medicine, and the social sciences such as economics and psychology. Applied mathematics, the branch of mathematics concerned with application of mathematical knowledge to other fields, inspires and makes use of new mathematical discoveries and sometimes leads to the development of entirely new disciplines. Mathematicians also engage in pure mathematics, or mathematics for its own sake, without having any application in mind, although practical applications for what began as pure mathematics are often discovered later.[7]

Contents [hide] • • • • • •

1 Etymology 2 History 3 Inspiration, pure and applied mathematics, and aesthetics 4 Notation, language, and rigor 5 Mathematics as science 6 Fields of mathematics

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6.1 Quantity 6.2 Structure 6.3 Space 6.4 Change 6.5 Foundations and philosophy 6.6 Discrete mathematics 6.7 Applied mathematics 7 Common misconceptions o 7.1 Mathematics and physical reality 8 See also 9 Notes 10 References

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11 External links

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[edit] Etymology The word "mathematics" comes from the Greek μάθημα (máthēma), which means learning, study, science, and additionally came to have the narrower and more technical meaning "mathematical study", even in Classical times. Its adjective is μαθηματικός (mathēmatikós), related to learning, or studious, which likewise further came to mean mathematical. In particular, μαθηματικὴ τέχνη (mathēmatikḗ tékhnē), in Latin ars mathematica, meant the mathematical art. The apparent plural form in English, like the French plural form les mathématiques (and the less commonly used singular derivative la mathématique), goes back to the Latin neuter plural mathematica (Cicero), based on the Greek plural τα μαθηματικά (ta mathēmatiká), used by Aristotle, and meaning roughly "all things mathematical".[8] In English, however, the noun mathematics takes singular verb forms. It is often shortened to math in English-speaking North America and maths elsewhere.

[edit] History A quipu, a counting device used by the Inca. Main article: History of mathematics The evolution of mathematics might be seen as an ever-increasing series of abstractions, or alternatively an expansion of subject matter. The first abstraction was probably that of numbers: the realization that two apples and two oranges (for example) have something in common was a breakthrough in human thought. In addition to recognizing how to count physical objects, prehistoric peoples also recognized how to count abstract quantities, like time — days, seasons, years. Elementary arithmetic (addition, subtraction, multiplication and division) naturally followed. Further steps needed writing or some other system for recording numbers such as tallies or the knotted strings called quipu used by the Inca to store numerical data. Numeral systems have been many and diverse, with the first known written numerals created by Egyptians in Middle Kingdom texts such as the Rhind Mathematical Papyrus. The Indus Valley civilization developed the modern decimal system, including the concept of zero.

Mayan numerals From the beginning of recorded history, the major disciplines within mathematics arose out of the need to do calculations relating to taxation and commerce, to understand the relationships among numbers, to measure land, and to predict astronomical events. These needs can be roughly related to the broad subdivision of mathematics into the studies of quantity, structure, space, and change. Mathematics has since been greatly extended, and there has been a fruitful interaction between mathematics and science, to the benefit of both. Mathematical discoveries have been made throughout history and continue to be made today. According to Mikhail B. Sevryuk, in the January 2006 issue of the Bulletin of the American Mathematical Society, "The number of papers and books included in the Mathematical Reviews database since 1940 (the first year of operation of MR) is now more than 1.9 million, and more than 75 thousand items are added to the database each year. The overwhelming majority of works in this ocean contain new mathematical theorems and their proofs."[9]

[edit] Inspiration, pure and applied mathematics, and aesthetics

Sir Isaac Newton (1643-1727), an inventor of infinitesimal calculus. Main article: Mathematical beauty Mathematics arises wherever there are difficult problems that involve quantity, structure, space, or change. At first these were found in commerce, land measurement and later astronomy; nowadays, all sciences suggest problems studied by mathematicians, and many problems arise within mathematics itself. For example, the physicist Richard Feynman invented the path integral formulation of quantum mechanics using a combination of mathematical reasoning and physical insight, and today's string theory, a still-developing scientific theory which attempts to unify the four fundamental forces of nature, continues to inspire new mathematics.[10] Some mathematics is only relevant in the area that inspired it, and is applied to solve further problems in that area. But often mathematics inspired by one area proves useful in many areas, and joins the general stock of mathematical concepts. The remarkable fact that even the "purest" mathematics often turns out to have practical applications is what Eugene Wigner has called "the unreasonable effectiveness of mathematics."[11] As in most areas of study, the explosion of knowledge in the scientific age has led to specialization in mathematics. One major distinction is between pure mathematics and applied mathematics: most mathematicians focus their research solely on one of these areas, and sometimes the choice is made as

early as their undergraduate studies. Several areas of applied mathematics have merged with related traditions outside of mathematics and become disciplines in their own right, including statistics, operations research, and computer science. For those who are mathematically inclined, there is often a definite aesthetic aspect to much of mathematics. Many mathematicians talk about the elegance of mathematics, its intrinsic aesthetics and inner beauty. Simplicity and generality are valued. There is beauty in a simple and elegant proof, such as Euclid's proof that there are infinitely many prime numbers, and in an elegant numerical method that speeds calculation, such as the fast Fourier transform. G. H. Hardy in A Mathematician's Apology expressed the belief that these aesthetic considerations are, in themselves, sufficient to justify the study of pure mathematics.[12] Mathematicians often strive to find proofs of theorems that are particularly elegant, a quest Paul Erdős often referred to as finding proofs from "The Book" in which God had written down his favorite proofs.[13][14] The popularity of recreational mathematics is another sign of the pleasure many find in solving mathematical questions.

[edit] Notation, language, and rigor The infinity symbol ∞ in several typefaces. Main article: Mathematical notation Most of the mathematical notation in use today was not invented until the 16th century.[15] Before that, mathematics was written out in words, a painstaking process that limited mathematical discovery.[citation needed] In the 18th century, Euler was responsible for many of the notations in use today. Modern notation makes mathematics much easier for the professional, but beginners often find it daunting. It is extremely compressed: a few symbols contain a great deal of information. Like musical notation, modern mathematical notation has a strict syntax and encodes information that would be difficult to write in any other way. Mathematical language can also be hard for beginners. Words such as or and only have more precise meanings than in everyday speech. Additionally, words such as open and field have been given specialized mathematical meanings. Mathematical jargon includes technical terms such as homeomorphism and integrable. But there is a reason for special notation and technical jargon: mathematics requires more precision than everyday speech. Mathematicians refer to this precision of language and logic as "rigor". Rigor is fundamentally a matter of mathematical proof. Mathematicians want their theorems to follow from axioms by means of systematic reasoning. This is to avoid mistaken "theorems", based on fallible intuitions, of which many instances have occurred in the history of the subject.[16] The level of rigor expected in mathematics has varied over time: the Greeks expected detailed arguments, but at the time of Isaac Newton the methods employed were less rigorous. Problems inherent in the definitions used by Newton would lead to a resurgence of careful analysis and formal proof in the 19th century. Today, mathematicians continue to argue among themselves about computer-assisted proofs. Since large computations are hard to verify, such proofs may not be sufficiently rigorous.[17] Axioms in traditional thought were "self-evident truths", but that conception is problematic. At a formal level, an axiom is just a string of symbols, which has an intrinsic meaning only in the context of all derivable formulas of an axiomatic system. It was the goal of Hilbert's program to put all of mathematics on a firm axiomatic basis, but according to Gödel's incompleteness theorem every (sufficiently powerful) axiomatic system has undecidable formulas; and so a final axiomatization of mathematics is impossible.

Nonetheless mathematics is often imagined to be (as far as its formal content) nothing but set theory in some axiomatization, in the sense that every mathematical statement or proof could be cast into formulas within set theory.[18]

[edit] Mathematics as science

Carl Friedrich Gauss, himself known as the "prince of mathematicians", referred to mathematics as "the Queen of the Sciences". Carl Friedrich Gauss referred to mathematics as "the Queen of the Sciences".[19] In the original Latin Regina Scientiarum, as well as in German Königin der Wissenschaften, the word corresponding to science means (field of) knowledge. Indeed, this is also the original meaning in English, and there is no doubt that mathematics is in this sense a science. The specialization restricting the meaning to natural science is of later date. If one considers science to be strictly about the physical world, then mathematics, or at least pure mathematics, is not a science. Albert Einstein has stated that "as far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality."[20] Many philosophers believe that mathematics is not experimentally falsifiable, and thus not a science according to the definition of Karl Popper.[21] However, in the 1930s important work in mathematical logic showed that mathematics cannot be reduced to logic, and Karl Popper concluded that "most mathematical theories are, like those of physics and biology, hypothetico-deductive: pure mathematics therefore turns out to be much closer to the natural sciences whose hypotheses are conjectures, than it seemed even recently."[22] Other thinkers, notably Imre Lakatos, have applied a version of falsificationism to mathematics itself. An alternative view is that certain scientific fields (such as theoretical physics) are mathematics with axioms that are intended to correspond to reality. In fact, the theoretical physicist, J. M. Ziman, proposed that science is public knowledge and thus includes mathematics.[23] In any case, mathematics shares much in common with many fields in the physical sciences, notably the exploration of the logical consequences of assumptions. Intuition and experimentation also play a role in the formulation of conjectures in both mathematics and the (other) sciences. Experimental mathematics continues to grow in importance within mathematics, and computation and simulation are playing an increasing role in both the sciences and mathematics, weakening the objection that mathematics does not use the scientific method. In his 2002 book A New Kind of Science, Stephen Wolfram argues that computational mathematics deserves to be explored empirically as a scientific field in its own right. The opinions of mathematicians on this matter are varied. Many mathematicians feel that to call their area a science is to downplay the importance of its aesthetic side, and its history in the traditional seven liberal

arts; others feel that to ignore its connection to the sciences is to turn a blind eye to the fact that the interface between mathematics and its applications in science and engineering has driven much development in mathematics. One way this difference of viewpoint plays out is in the philosophical debate as to whether mathematics is created (as in art) or discovered (as in science). It is common to see universities divided into sections that include a division of Science and Mathematics, indicating that the fields are seen as being allied but that they do not coincide. In practice, mathematicians are typically grouped with scientists at the gross level but separated at finer levels. This is one of many issues considered in the philosophy of mathematics. Mathematical awards are generally kept separate from their equivalents in science. The most prestigious award in mathematics is the Fields Medal,[24][25] established in 1936 and now awarded every 4 years. It is often considered, misleadingly, the equivalent of science's Nobel Prizes. The Wolf Prize in Mathematics, instituted in 1978, recognizes lifetime achievement, and another major international award, the Abel Prize, was introduced in 2003. These are awarded for a particular body of work, which may be innovation, or resolution of an outstanding problem in an established field. A famous list of 23 such open problems, called "Hilbert's problems", was compiled in 1900 by German mathematician David Hilbert. This list achieved great celebrity among mathematicians, and at least nine of the problems have now been solved. A new list of seven important problems, titled the "Millennium Prize Problems", was published in 2000. Solution of each of these problems carries a $1 million reward, and only one (the Riemann hypothesis) is duplicated in Hilbert's problems.

[edit] Fields of mathematics An abacus, a simple calculating tool used since ancient times. As noted above, the major disciplines within mathematics first arose out of the need to do calculations in commerce, to understand the relationships between numbers, to measure land, and to predict astronomical events. These four needs can be roughly related to the broad subdivision of mathematics into the study of quantity, structure, space, and change (i.e., arithmetic, algebra, geometry, and analysis). In addition to these main concerns, there are also subdivisions dedicated to exploring links from the heart of mathematics to other fields: to logic, to set theory (foundations), to the empirical mathematics of the various sciences (applied mathematics), and more recently to the rigorous study of uncertainty.

[edit] Quantity The study of quantity starts with numbers, first the familiar natural numbers and integers ("whole numbers") and arithmetical operations on them, which are characterized in arithmetic. The deeper properties of integers are studied in number theory, whence such popular results as Fermat's Last Theorem. Number theory also holds two widely considered unsolved problems: the twin prime conjecture and Goldbach's conjecture. As the number system is further developed, the integers are recognized as a subset of the rational numbers ("fractions"). These, in turn, are contained within the real numbers, which are used to represent continuous quantities. Real numbers are generalized to complex numbers. These are the first steps of a hierarchy of numbers that goes on to include quarternions and octonions. Consideration of the natural numbers also leads to the transfinite numbers, which formalize the concept of counting to infinity. Another area of study is size, which leads to the cardinal numbers and then to another conception of infinity: the aleph numbers, which allow meaningful comparison of the size of infinitely large sets.

Natural numbers

Integers

Rational numbers

Real numbers

Complex numbers

[edit] Structure Many mathematical objects, such as sets of numbers and functions, exhibit internal structure. The structural properties of these objects are investigated in the study of groups, rings, fields and other abstract systems, which are themselves such objects. This is the field of abstract algebra. An important concept here is that of vectors, generalized to vector spaces, and studied in linear algebra. The study of vectors combines three of the fundamental areas of mathematics: quantity, structure, and space. Vector calculus expands the field into a fourth fundamental area, that of change. Tensor calculus studies symmetry and the behavior of vectors under rotation. A number of ancient problems concerning Compass and straightedge constructions were finally solved using Galois theory.

Number theory

Abstract algebra

Group theory

Order theory

[edit] Space The study of space originates with geometry - in particular, Euclidean geometry. Trigonometry combines space and numbers, and encompasses the well-known Pythagorean theorem. The modern study of space generalizes these ideas to include higher-dimensional geometry, non-Euclidean geometries (which play a central role in general relativity) and topology. Quantity and space both play a role in analytic geometry, differential geometry, and algebraic geometry. Within differential geometry are the concepts of fiber bundles and calculus on manifolds. Within algebraic geometry is the description of geometric objects as solution sets of polynomial equations, combining the concepts of quantity and space, and also the study of topological groups, which combine structure and space. Lie groups are used to study space, structure, and change. Topology in all its many ramifications may have been the greatest growth area in 20th century mathematics, and includes the long-standing Poincaré conjecture and the controversial four color theorem, whose only proof, by computer, has never been verified by a human.

Geometry

Trigonometry

Differential geometry

Topology

Fractal geometry

[edit] Change Understanding and describing change is a common theme in the natural sciences, and calculus was developed as a powerful tool to investigate it. Functions arise here, as a central concept describing a changing quantity. The rigorous study of real numbers and real-valued functions is known as real analysis, with complex analysis the equivalent field for the complex numbers. The Riemann hypothesis, one of the most fundamental open questions in mathematics, is drawn from complex analysis. Functional analysis focuses attention on (typically infinite-dimensional) spaces of functions. One of many applications of functional analysis is quantum mechanics. Many problems lead naturally to relationships between a quantity and its rate of change, and these are studied as differential equations. Many phenomena in nature can be described by dynamical systems; chaos theory makes precise the ways in which many of these systems exhibit unpredictable yet still deterministic behavior.

Calculus

Vector calculus

Differential equations

Dynamical systems

Chaos theory

[edit] Foundations and philosophy In order to clarify the foundations of mathematics, the fields of mathematical logic and set theory were developed, as well as category theory which is still in development. The crisis of foundations, which is the early 20th century's term for the search for proper foundations of mathematics, is a persistent phenomenon; it is illustrated by a number of controversies, including the controversy over Cantor's set theory and the Brouwer-Hilbert controversy. Mathematical logic is concerned with setting mathematics on a rigid axiomatic framework, and studying the results of such a framework. As such, it is home to Gödel's second incompleteness theorem, perhaps the most widely celebrated result in logic, which (informally) implies that any formal system that contains basic arithmetic, if sound (meaning that all theorems that can be proven are true), is necessarily incomplete (meaning that there are true theorems which cannot be proved in that system). Gödel showed how to construct, whatever the given collection of number-theoretical axioms, a formal statement in the logic that is a true number-theoretical fact, but which does not follow from those axioms. Therefore no formal system is a true axiomatization of full number theory. Modern logic is divided into recursion theory, model theory, and proof theory, and is closely linked to theoretical computer science.

Mathematical logic

Set theory

Category theory

[edit] Discrete mathematics Discrete mathematics is the common name for the fields of mathematics most generally useful in theoretical computer science. This includes computability theory, computational complexity theory, and information theory. Computability theory examines the limitations of various theoretical models of the computer, including the most powerful known model - the Turing machine. Complexity theory is the study of tractability by computer; some problems, although theoretically solvable by computer, are so expensive in terms of time or space that solving them is likely to remain practically unfeasible, even with rapid advance of computer hardware. Finally, information theory is concerned with the amount of data that can be stored on a given medium, and hence deals with concepts such as compression and entropy. As a relatively new field, discrete mathematics has a number of fundamental open problems. The most famous of these is the "P=NP?" problem, one of the Millennium Prize Problems.[26]

Combinatorics

Theory of computation

Cryptography

Graph theory

[edit] Applied mathematics Applied mathematics considers the use of abstract mathematical tools in solving concrete problems in the sciences, business, and other areas. An important field in applied mathematics is statistics, which uses probability theory as a tool and allows the description, analysis, and prediction of phenomena where chance plays a role. Most experiments, surveys and observational studies require the informed use of

statistics. (Many statisticians, however, do not consider themselves to be mathematicians, but rather part of an allied group.) Numerical analysis investigates computational methods for efficiently solving a broad range of mathematical problems that are typically too large for human numerical capacity; it includes the study of rounding errors or other sources of error in computation. Mathematical physicsMathematical fluid dynamics Numerical analysis Optimization Probability theory

Statistics

Financial mathematicsGame theory

[edit] Common misconceptions Mathematics is not a closed intellectual system, in which everything has already been worked out. There is no shortage of open problems. Mathematicians publish many thousands of papers embodying new discoveries in mathematics every month. Mathematics is not numerology; it is not concerned with "supernatural" properties of numbers. It is not accountancy; nor is it restricted to arithmetic. Pseudomathematics is a form of mathematics-like activity undertaken outside academia, and occasionally by mathematicians themselves. It often consists of determined attacks on famous questions, consisting of proof-attempts made in an isolated way (that is, long papers not supported by previously published theory). The relationship to generally accepted mathematics is similar to that between pseudoscience and real science. The misconceptions involved are normally based on: • • •

misunderstanding of the implications of mathematical rigor; attempts to circumvent the usual criteria for publication of mathematical papers in a learned journal after peer review, often in the belief that the journal is biased against the author; lack of familiarity with, and therefore underestimation of, the existing literature.

Like astronomy, mathematics owes much to amateur contributors such as Fermat, Mersenne, and Ramanujan. See further the List of amateur mathematicians.

[edit] Mathematics and physical reality Mathematical concepts and theorems need not correspond to anything in the physical world. Insofar as a correspondence does exist, while mathematicians and physicists may select axioms and postulates that seem reasonable and intuitive, it is not necessary for the basic assumptions within an axiomatic system to be true in an empirical or physical sense. Thus, while many axiom systems are derived from our perceptions and experiments, they are not dependent on them. For example, we could say that the physical concept of two apples may be accurately modeled by the natural number 2. On the other hand, we could also say that the natural numbers are not an accurate model because there is no standard "unit" apple and no two apples are exactly alike. The modeling idea is further complicated by the possibility of fractional or partial apples. So while it may be instructive to visualize the axiomatic definition of the natural numbers as collections of apples, the definition itself is not dependent upon nor derived from any actual physical entities. Nevertheless, mathematics remains extremely useful for solving real-world problems.

[edit] See also Mathematics portal • • • • • • • • • • • •

Dyscalculia List of basic mathematics topics Lists of mathematics topics Mathematics and art Mathematics competitions Mathematics education Mathematical game Mathematical model Mathematical problem Mathematical structure Mathematics portal Philosophy of mathematics

[edit] Notes

Responsibility assumption From Wikipedia, the free encyclopedia

Jump to: navigation, search This article may contain original research or unverified claims. Please improve the article by adding references. See the talk page for details. (July 2007) Responsibility assumption is a doctrine in the personal growth field holding that each individual has substantial or total responsibility for the events and circumstances that befall them in their life. While there is little that is notable about the notion that each person has at least some role in shaping their experience, the doctrine of responsibility assumption posits that the individual's mental contribution to his or her own experience is substantially greater than is normally thought. "I must have wanted this" is the type of catchphrase used by adherents of this doctrine when encountering situations, pleasant or unpleasant, to remind them that their own desires and choices led to the present outcome. The term responsibility assumption thus has a specialized meaning beyond the general concept of taking responsibility for something, and is not to be confused with the general notion of making an assumption that a concept such as "responsibility" exists.

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1 Variations in degree of personal responsibility postulated o 1.1 Partial but substantial responsibility o 1.2 Total responsibility 2 Religious and philosophical roots and usage 3 In popular culture 4 See also 5 References o 5.1 Nonfiction o 5.2 Fiction 6 External links

[edit] Variations in degree of personal responsibility postulated The main variable within various interpretations of the responsibility assumption doctrine is the degree to which the individual is considered the cause of his or her own experience, ranging from partial but substantial, to total.

[edit] Partial but substantial responsibility In its forms positing less than total responsibility, the doctrine appears in nearly all motivational programs, some psychotherapy, and large group awareness training programs. In programs as noncontroversial as books on the power of positive thinking, it functions as a mechanism to point out that each individual does affect the perceived world by the decisions they make each day and by the choices they made in the past. These less absolute forms may be expressed within the rubric that we cannot control the situations that befall us, but we can at least control our attitudes toward them.

[edit] Total responsibility In its more absolute form, the doctrine becomes both more pronounced and more controversial. Perhaps the most prominent dividing line of controversy is the threshold of reversed mental causation, where sufficient responsibility is assigned to the individual that their thoughts or mental attitudes are considered the actual cause of external situations or physical occurrences rather than vice-versa, along the lines of the catchphrase, "mind over matter." In this realm the doctrine can present controversial propositions such as, "you chose to have cancer and can just as easily become well if you choose," or the even more shocking and unpalatable proposition, "this genocide took place because the victims wanted to die." Despite the extremity of these positions, there are indeed groups and schools of thought subscribing to the doctrine of responsibility assumption that would support these propositions and more.[1]

[edit] Religious and philosophical roots and usage The est seminars popularized the doctrine "responsibility assumption" in the 1970s although they did not explicitly use the term.[citation needed] The doctrine both predates est and is found in a far wider variety of settings. The doctrine has spiritual roots in the monism of Eastern religious traditions which hold that only one true being exists, and all people are one with each other and with god and hence possess Godlike powers, though they are often unaware of it. It has been likened to karma, which however tends to suggest

later retribution for earlier acts, while responsibility assumption posits more of an immediate link between the experience desired and the outcome received. The doctrine also has associations with the neoplatonist notion of an illusory world, which the doctrine's adherents would phrase more precisely as an illusion of external worldly effects on inner mental states. It finds further support in philosophical idealism, which posits thought as the one true substance. Among historically Christian churches, denominations have belief systems that incorporate doctrinal elements similar to responsibility assumption.[citation needed] The doctrine can be found in the work of psychotherapist Georg Groddeck assigning mental causes to physical ailments, has been more recently propagated by self-help authors such as Arnold Patent, and can be found in a number of New Age and new religious movements. Prominent among these are Christian Science and the New Thought Movement, whose constituent theologies espouse mental approaches to bodily healing and express precepts such as, "to each, according to his belief." The doctrine combined with reversed causation can further be found explicitly expressed in works such as A Course in Miracles.

[edit] In popular culture Lists of miscellaneous information should be avoided. Please relocate any relevant information into appropriate sections or articles. (October 2007) The theme of responsibility assumption appears in several places in popular culture. For example, it appeared in Richard Bach's bestseller, Jonathan Livingston Seagull, and Bach addressed the topic more directly in a less-popular later book, Illusions. John Denver, a proponent of est, wrote two songs about it, Farewell Andromeda (1973) and Looking for Space (1975), and the opening lines of Farewell Andromeda capture the essence of responsibility assumption: Welcome to my morning, welcome to my day I'm the one responsible, I made it just this way To make myself some pictures, see what they might bring I think I made it perfectly, I wouldn't change a thing The 1956 movie Forbidden Planet featured an analogous concept to responsibility assumption, about a race who, through technology, became able to materialize their thoughts, to disastrous ends. The 1967 television series The Prisoner featured an ambiguous climax spawning several interpretations, one of which implicates responsibility assumption. Throughout the short seventeen-episode series, the eponymous prisoner, a man held against his will by a mysterious group, attempted to determine—and in the final episode apparently succeeded in determining—the identity of the mysterious person who led the group and thus ultimately determined the prisoner's fate. The moment of revelation in which the mysterious leader was literally unmasked by the prisoner was brief and unclear, but there are fans of the series who believe the unmasked leader was the prisoner himself. In 1962, the comic book superhero Spider-Man, created by Stan Lee, adopted the maxim, "With great power there must also come great responsibility" after his failure to stop a thief led to the death of his uncle Ben. The phrase has come into common usage as, "With great power comes great responsibility" and was used as the tagline for the 2002 Spider-Man movie.

In a deleted scene from the 1999 movie Dogma, a fallen angel explained how the subconscious demands of the damned that they be punished, as they believed God could never forgive their sins, remade the face of Hell from a simple separation from God into a "suffering pit." Though these are prominent examples, varying degrees of the doctrine of responsibility assumption have formed a minor theme more broadly within the United States cultural landscape since the 1960s counterculture. More generally, different cultures place different weight on individual responsibility and that this difference is manifested in folklore. In this view, the tale of the Fisherman and the Little Goldfish (in which the protagonist makes little effort to improve his lot) illustrates the denial of responsibility.

[edit] See also • • •

Phenomenalism Phenomenology Karma

[edit] References 1. ^ Espouse total responsibility o Dr. Joe Vitale o Landmark Education at this site states: “Responsibility,” according to The Charter of The Landmark Education Corporation, “begins with the willingness to be cause in the matter of one’s life. Ultimately, it is a context from which one chooses to live.” To be cause in the matter of one’s life is only possible if there are no other causes to which one is ultimately subject.

[edit] Nonfiction • •

Anonymous (1992). A Course in Miracles (2d ed.). Mill Valley, CA: Foundation for Inner Peace. ISBN 0-9606388-8-1. May, Rollo, and Irvin D. Yalom (1984). "Existential Psychotherapy," pp. 354-391 in Raymond J. Corsini, ed., Current Psychotherapies (3rd ed.). Itasca, IL: Peacock.

[edit] Fiction • •

Bach, Richard. Illusions—Confessions of a Reluctant Messiah. Bach, Richard (1970). Jonathan Livingston Seagull.

[edit] External links •

Leadership Personal Responsibility

Retrieved from "http://en.wikipedia.org/wiki/Responsibility_assumption" Categories: New Age | Personal development Hidden categories: Articles that may contain original research since July 2007 | All articles that may contain original research | All articles with unsourced statements | Articles with unsourced statements since February 2007 | Articles with trivia sections from October 2007

Mind From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Mind (disambiguation). For the football player, see John Minds. Mind collectively refers to the aspects of intellect and consciousness manifested as combinations of thought, perception, memory, emotion, will and imagination; mind is the stream of consciousness. It includes all of the brain's conscious processes. This denotation sometimes includes, in certain contexts, the working of the human unconscious or the conscious thoughts of animals. "Mind" is often used to refer especially to the thought processes of reason. There are many theories of the mind and its function. The earliest recorded works on the mind are by Zarathushtra, the Buddha, Plato, Aristotle, Adi Shankara and other ancient Greek, Indian and Islamic philosophers. Pre-scientific theories, based in theology, concentrated on the relationship between the mind and the soul, the supernatural, divine or god-given essence of the person. Modern theories, based on scientific understanding of the brain, theorize that the mind is a phenomenon of the brain and is synonymous with consciousness. The question of which human attributes make up the mind is also much debated. Some argue that only the "higher" intellectual functions constitute mind: particularly reason and memory. In this view the emotions - love, hate, fear, joy - are more "primitive" or subjective in nature and should be seen as different from the mind. Others argue that the rational and the emotional sides of the human person cannot be separated, that they are of the same nature and origin, and that they should all be considered as part of the individual mind. In popular usage mind is frequently synonymous with thought: It is that private conversation with ourselves that we carry on "inside our heads." Thus we "make up our minds," "change our minds" or are "of two minds" about something. One of the key attributes of the mind in this sense is that it is a private sphere to which no one but the owner has access. No-one else can "know our mind." They can only interpret what we consciously or unconsciously communicate.

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1 Aspects of mind o 1.1 Mental faculties o 1.2 Philosophy of mind o 1.3 Science of mind o 1.4 Social psychology and group behaviour o 1.5 Brain o 1.6 Mental health o 1.7 Developmental history of the human mind o 1.8 Animal intelligence o 1.9 Artificial intelligence o 1.10 Religious perspectives o 1.11 New age and alternative perspectives

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2 See also 3 References

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4 External links

[edit] Aspects of mind [edit] Mental faculties See also: Reason, Faculty psychology, and Modularity of mind Thought is a mental process in which the mind allows the being to model the world, and so to deal with it effectively according to their goals, plans, ends and desires. Words referring to similar concepts and processes include cognition, sentience, consciousness, idea, and imagination. Thinking involves the cerebral manipulation of information, as when we form concepts, engage in problem solving, reason and make decisions. Thinking is a higher cognitive function and the analysis of thinking processes is part of cognitive psychology. Memory is an organism's ability to store, retain, and subsequently recall information. Although traditional studies of memory began in the realms of philosophy, the late nineteenth and early twentieth century put memory within the paradigms of cognitive psychology. In recent decades, it has become one of the principal pillars of a new branch of science called cognitive neuroscience, a marriage between cognitive psychology and neuroscience. Imagination is accepted as the innate ability and process to invent partial or complete personal realms the mind derives from sense perceptions of the shared world. The term is technically used in psychology for the process of reviving in the mind percepts of objects formerly given in sense perception. Since this use of the term conflicts with that of ordinary language, some psychologists have preferred to describe this process as "imaging" or "imagery" or to speak of it as "reproductive" as opposed to "productive" or "constructive" imagination. Imagined images are seen with the "mind's eye". One hypothesis for the evolution of human imagination is that it allowed conscious beings to solve problems (and hence increase an individual's fitness) by use of mental simulation. Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, selfawareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment. It is a subject of much research in philosophy of mind, psychology, neuroscience, and cognitive science. Some philosophers divide consciousness into phenomenal consciousness, which is subjective experience itself, and access consciousness, which refers to the global availability of information to processing systems in the brain.[1] Phenomenal consciousness is a state with qualia. Phenomenal consciousness is being something and access consciousness is being conscious of something.

[edit] Philosophy of mind Main article: Philosophy of mind Philosophy of mind is the branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness and their relationship to the physical body. The mind-body problem, i.e. the relationship of the mind to the body, is commonly seen as the central issue in philosophy

of mind, although there are other issues concerning the nature of the mind that do not involve its relation to the physical body.[2] Dualism and monism are the two major schools of thought that attempt to resolve the mind-body problem. Dualism is the position that mind and body are in some way separate from each other. It can be traced back to Plato,[3] Aristotle[4][5][6] and the Samkhya and Yoga schools of Hindu philosophy,[7] but it was most precisely formulated by René Descartes in the 17th century.[8] Substance dualists argue that the mind is an independently existing substance, whereas Property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.[9] Monism is the position that mind and body are not ontologically distinct kinds of entities. This view was first advocated in Western Philosophy by Parmenides in the 5th Century BC and was later espoused by the 17th Century rationalist Baruch Spinoza.[10] Physicalists argue that only the entities postulated by physical theory exist, and that the mind will eventually be explained in terms of these entities as physical theory continues to evolve. Idealists maintain that the mind is all that exists and that the external world is either mental itself, or an illusion created by the mind. Neutral monists adhere to the position that there is some other, neutral substance, and that both matter and mind are properties of this unknown substance. The most common monisms in the 20th and 21st centuries have all been variations of physicalism; these positions include behaviorism, the type identity theory, anomalous monism and functionalism.[11] Many modern philosophers of mind adopt either a reductive or non-reductive physicalist position, maintaining in their different ways that the mind is not something separate from the body.[11] These approaches have been particularly influential in the sciences, particularly in the fields of sociobiology, computer science, evolutionary psychology and the various neurosciences.[12][13][14][15] Other philosophers, however, adopt a non-physicalist position which challenges the notion that the mind is a purely physical construct. Reductive physicalists assert that all mental states and properties will eventually be explained by scientific accounts of physiological processes and states.[16][17][18] Non-reductive physicalists argue that although the brain is all there is to the mind, the predicates and vocabulary used in mental descriptions and explanations are indispensable, and cannot be reduced to the language and lower-level explanations of physical science.[19][20] Continued neuroscientific progress has helped to clarify some of these issues. However, they are far from having been resolved, and modern philosophers of mind continue to ask how the subjective qualities and the intentionality (aboutness) of mental states and properties can be explained in naturalistic terms.[21][22]

[edit] Science of mind See also: Sigmund Freud, Carl Jung, and Unconscious mind Psychology is the scientific study of human behaviour; Noology, the study of thought. As both an academic and applied discipline, Psychology involves the scientific study of mental processes such as perception, cognition, emotion, personality, as well as environmental influences, such as social and cultural influences, and interpersonal relationships, in order to devise theories of human behaviour. Psychology also refers to the application of such knowledge to various spheres of human activity, including problems of individuals' daily lives and the treatment of mental health problems. Psychology differs from the other social sciences (e.g., anthropology, economics, political science, and sociology) due to its focus on experimentation at the scale of the individual, as opposed to groups or institutions. Historically, psychology differed from biology and neuroscience in that it was primarily concerned with mind rather than brain, a philosophy of mind known as dualism. Modern psychological

science incorporates physiological and neurological processes into its conceptions of perception, cognition, behaviour, and mental disorders. A new scientific initiative, the Decade of the Mind, seeks to advocate for the U.S. Government to invest $4 billion over the next ten years in the science of the mind. However, the mind research has many ramifications. There is a possibility that the mind is an entity of a dynamic system that integrates its processes. Integration means conscious control of coordination of the mind processes. A thing that may have remained without attention, and needs further elaboration.

[edit] Social psychology and group behaviour Social psychology is the study of how social conditions affect human beings. Scholars in this field are generally either psychologists or sociologists. Social psychologists who are trained in psychology tend to focus on individuals as the unit of study; sociologists tend to favor the study of groups and larger social units such as societies, although there are exceptions to these general tendencies in both fields. Despite their similarity, the disciplines also tend to differ in their respective goals, approaches, methods, and terminology. They also favor separate academic journals and societies. Like biophysics and cognitive science, social psychology is an interdisciplinary area. The greatest period of collaboration between sociologists and psychologists was during the years immediately following World War II (Sewell, 1989). Although there has been increasing isolation and specialization in recent years, some degree of overlap and influence remains between the two disciplines.

[edit] Brain See also: Cognitive science, Meme, and Memetics In animals the brain, or encephalon (Greek for "in the head"), is the control center of the central nervous system, responsible for thought. In most animals, the brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing, equilibrioception, taste and olfaction. While all vertebrates have a brain, most invertebrates have either a centralized brain or collections of individual ganglia. Primitive animals such as sponges do not have a brain at all. Brains can be extremely complex. For example, the human brain contains more than 100 billion neurons, each linked to as many as 10,000 others.

[edit] Mental health Main article: Mental health By analogy with the health of the body, one can speak metaphorically of a state of health of the mind, or mental health. Merriam-Webster defines mental health as "A state of emotional and psychological wellbeing in which an individual is able to use his or her cognitive and emotional capabilities, function in society, and meet the ordinary demands of everyday life." According to the World Health Organization (WHO), there is no one "official" definition of mental health. Cultural differences, subjective assessments, and competing professional theories all affect how "mental health" is defined. In general, most experts agree that "mental health" and "mental illness" are not opposites. In other words, the absence of a recognized mental disorder is not necessarily an indicator of mental health. One way to think about mental health is by looking at how effectively and successfully a person functions. Feeling capable and competent; being able to handle normal levels of stress, maintaining

satisfying relationships, and leading an independent life; and being able to "bounce back," or recover from difficult situations, are all signs of mental health. Psychotherapy is an interpersonal, relational intervention used by trained psychotherapists to aid clients in problems of living. This usually includes increasing individual sense of well-being and reducing subjective discomforting experience. Psychotherapists employ a range of techniques based on experiential relationship building, dialogue, communication and behavior change and that are designed to improve the mental health of a client or patient, or to improve group relationships (such as in a family). Most forms of psychotherapy use only spoken conversation, though some also use various other forms of communication such as the written word, art, drama, narrative story, or therapeutic touch. Psychotherapy occurs within a structured encounter between a trained therapist and client(s). Purposeful, theoretically based psychotherapy began in the 19th century with psychoanalysis; since then, scores of other approaches have been developed and continue to be created.

[edit] Developmental history of the human mind The nature and origins of hominid intelligence is of natural interest to humans as the most successful and intelligent hominid species. As nearly a century of archaeological research has shown, the hominids evolved from earlier primates in eastern Africa. Like some non-primate tree-dwelling mammals, such as opossums, they evolved an opposable thumb, which enabled them to grasp and manipulate objects, such as fruit. They also possessed front-facing binocular vision. Around 10 million years ago, the earth's climate entered a cooler and drier phase, which led eventually to the ice ages. This forced tree-dwelling animals to adapt to their new environment or die out. Some primates adapted to this challenge by adopting bipedalism: walking on their hind legs. The advantages of this development are widely disputed. It was once thought that this gave their eyes greater elevation and the ability to see approaching danger further off but as we now know that hominids developed in a forest environment this theory has little real basis. At some point the bipedal primates developed the ability to pick up sticks, bones and stones and use them as weapons, or as tools for tasks such as killing smaller animals or cutting up carcases. In other words, these primates developed the use of technology, an adaptation other animals have not attained to the same capacity as these hominids. Bipedal tool-using primates evolved in the class of hominids, of which the earliest species, such as Sahelanthropus tchadensis, are dated to about 7 million years ago although homonid-made tools were not developed until about 2 million years ago. Thus bipedal hominids existed for 5 million years before they started making tools. The advantage of bipedalism would have been simply to be able to carry anything with survival value from an unfavorable environment to a more favorable one. Anything too big or heavy would have to be broken or cut. This would be an insight that led early minds to develop tools for the purpose. From about 5 million years ago, the hominid brain began to develop rapidly, some say this was because an evolutionary loop had been established between the hominid hand and brain. This theory says that the use of tools conferred a crucial evolutionary advantage on those hominids which had this skill. The use of tools required a larger and more sophisticated brain to co-ordinate the fine hand movements required for this task. However this theory has not been confirmed and many other theories have been developed based on scientific evidence. It is likely that a tool using hominid would have made a formidable enemy and that surviving this new threat would have been the loop that increased brain size and mind power. By 2 million years ago Homo habilis had appeared in east Africa: the first hominid to make tools rather than merely use them. Several more species in the genus 'homo' appeared before fully modern humans, known as homo sapiens developed. these homo sapiens, which are the archaic version of the modern human showed the first evidence of language, and the range of activities we call culture, including art and religion.

About 200,000 years ago in Europe and the Near East hominids known to us as Neanderthal man or some call them homo neanderthalensis appeared. They too had art such as decorated tools for aesthetic pleasure and culture, such as burying their dead in ways which suggest spiritual beliefs. hotly debated in the scientific community is whether or not Homo sapiens developed from neanderthals or a combinations of hominids. Some scientists say that the Neanderthals were wiped out by homo sapiens when they entered the region about 40,000 years ago. What is known is that by 25,000 years ago the Neanderthal was extinct. Between 120,000 to 165,000 years ago Homo sapiens reached their fully modern form, the first evidence of this was found in Africa although once again the origins are widely debated between three theories, the Single-Origin theory, the Multiregional model and the Assimilation model. See also: Evolutionary psychology, Evolutionary neuroscience, and Paleoanthropology

[edit] Animal intelligence Animal cognition, or cognitive ethology, is the title given to a modern approach to the mental capacities of animals. It has developed out of comparative psychology, but has also been strongly influenced by the approach of ethology, behavioral ecology, and evolutionary psychology. Much of what used to be considered under the title of animal intelligence is now thought of under this heading. Animal language acquisition, attempting to discern or understand the degree to which animal cognistics can be revealed by linguistics-related study, has been controversial among cognitive linguists.

[edit] Artificial intelligence This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2007) Main article: Philosophy of artificial intelligence The term Artificial Intelligence (AI) was first used by John McCarthy who considers it to mean "the science and engineering of making intelligent machines".[23] It can also refer to intelligence as exhibited by an artificial (man-made, non-natural, manufactured) entity. AI is studied in overlapping fields of computer science, psychology, neuroscience and engineering, dealing with intelligent behavior, learning and adaptation and usually developed using customized machines or computers. Research in AI is concerned with producing machines to automate tasks requiring intelligent behavior. Examples include control, planning and scheduling, the ability to answer diagnostic and consumer questions, handwriting, natural language, speech and facial recognition. As such, the study of AI has also become an engineering discipline, focused on providing solutions to real life problems, knowledge mining, software applications, strategy games like computer chess and other video games. One of the biggest difficulties with AI is that of comprehension. Many devices have been created that can do amazing things, but critics of AI claim that no actual comprehension by the AI machine has taken place. The debate about the nature of the mind is relevant to the development of artificial intelligence. If the mind is indeed a thing separate from or higher than the functioning of the brain, then hypothetically it would be much more difficult to recreate within a machine, if it were possible at all. If, on the other hand, the mind is no more than the aggregated functions of the brain, then it will be possible to create a machine with a recognisable mind (though possibly only with computers much different from today's), by simple virtue of the fact that such a machine already exists in the form of the human brain.

[edit] Religious perspectives

Various religious traditions have contributed unique perspectives on the nature of mind. In many traditions, especially mystical traditions, overcoming the ego is considered a worthy spiritual goal. Judaism teaches that "moach shalit al halev", the mind rules the heart. Humans can approach the Divine intellectually, through learning and behaving according to the Divine Will as enclothed in the Torah, and use that deep logical understanding to elicit and guide emotional arousal during prayer. Christianity has tended to see the mind as distinct from the soul (Greek nous) and sometimes further distinguished from the spirit. Western esoteric traditions sometimes refer to a mental body that exists on a plane other than the physical. Hinduism's various philosophical schools have debated whether the human soul (Sanskrit atman) is distinct from, or identical to, Brahman, the divine reality. Buddhism attempted to break with such metaphysical speculation, and posited that there is actually no distinct thing as a human being, who merely consists of five aggregates, or skandhas. The Indian philosopher-sage Sri Aurobindo attempted to unite the Eastern and Western psychological traditions with his integral psychology, as have many philosophers and New religious movements. Swami Parmanand Ji Maharaj of Bhagwat Bhakti Ashram also gave a very good discourse on The Mind. Taoism sees the human being as contiguous with natural forces, and the mind as not separate from the body. Confucianism sees the mind, like the body, as inherently perfectible. See also: Buddhism and psychology

[edit] New age and alternative perspectives According to the Parapsychological Association, parapsychology is the scientific study of certain types of paranormal phenomena, or of phenomena which appear to be paranormal.[24] The term is based on the Greek para (beside/beyond), psyche (soul/mind), and logos (account/explanation) and was coined by psychologist Max Dessoir in or before 1889. Its first appearance was in an article by Dessoir in the June 1889 issue of the German publication Sphinx.[25] J. B. Rhine later popularized "parapsychology" as a replacement for the earlier term "psychical research", during a shift in methodologies which brought experimental methods to the study of psychic phenomena.[25] In contemporary research, the term 'parapsychology' refers to the study of psi, a general blanket term used by academic parapsychologists to denote anomalous processes or outcomes.[26][27][28] The scientific reality of parapsychological phenomena and the validity of scientific parapsychological research is a matter of frequent dispute and criticism. The field is regarded by critics as a pseudoscience. Parapsychologists, in turn, say that parapsychological research is scientifically rigorous. Despite criticisms, a number of academic institutions now conduct research on the topic, employing laboratory methodologies and statistical techniques, such as meta-analysis.[citation needed] The Parapsychological Association is the leading association for parapsychologists and has been a member of the American Association for the Advancement of Science since 1969.[29]

[edit] See also • • • •

Mental state Mind at Large Subjective character of experience Theory of mind

[edit] References

Sport From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Sport (disambiguation).

Sport in childhood. Association football, shown above, a team sport, and may provide social interaction. Sport is activity that is governed by a set of rules or customs and often engaged in competitively. Sports commonly refer to activities where the physical capabilities of the competitor are the sole or primary determiner of the outcome (winning or losing), but the term is also used to include activities such as mind sports (a common name for some card games and board games with little to no element of chance) and motor sports where mental acuity or equipment quality are major factors. Sport is commonly defined as an organized, competitive and skillful physical activity requiring commitment and fair play. Sports differ from games based on levels of organization and profit (not always monetary). Accurate records are kept and updated, while failures and accomplishments are widely announced in sport news.

[edit] Terminology

Show Jumping, an equestrian sport.

In British English, sporting activities are commonly denoted by the collective noun "sport". In American English, "sports" is more used. In all English dialects, "sports" is the term used for more than one specific sport. For example, "football and swimming are my favourite sports", would sound natural to all English speakers, whereas "I enjoy sport" would sound less natural than "I enjoy sports" to North Americans. The term "sport" is sometimes extended to encompass all competitive activities in which offense and defense are played, regardless of the level of physical activity. Both games of skill and motor sport exhibit many of the characteristics of physical sports, such as skill, sportsmanship, and at the highest levels, even professional sponsorship associated with physical sports. Air sports, billiards, bridge, chess, motorcycle racing, and powerboating are all recognized as sports by the International Olympic Committee with their world governing bodies represented in the Association of the IOC Recognised International Sports Federations.[1]

[edit] References 1. ^ "Recognized non-Olympic Sports" (2007-01-03). •

Free, Marcus; Hughson, John (2006) Common culture, commodity fetishism and the cultural contradictions of sport International Journal of Cultural Studies, Vol. 9, No. 1, pp. 83-104 DOI: 10.1177/1367877906061166 SAGE Publications

[edit] See also Sports and games portal

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Martial arts From Wikipedia, the free encyclopedia

Jump to: navigation, search For other uses, see Martial arts (disambiguation). A block print from the Wu Pei Chih ("Bubishi" in Japanese), an 18th- or 19th-century text which describes techniques found in Chinese martial arts (mostly addressing Fujian White Crane Gong-fu). Martial arts are systems of codified practices and traditions of training for combat. While they may be studied for various reasons, martial arts share a single objective: to defeat one or more people physically and to defend oneself or others from physical threat. In addition, some martial arts are linked to spiritual or religious beliefs/philosophies such as Buddhism, Daoism, Confucianism or Shinto while others have their own spiritual or non-spiritual code of honour. Many arts are also practised competitively most commonly as combat sports, but may also be in the form of dance. The word 'martial' derives from the name of Mars, the Roman god of war. The term 'martial arts' literally means arts of war. This term comes from 15th century Europeans who were referring to their own

fighting arts that are today known as historical European martial arts. A practitioner of martial arts is referred to as a martial artist. In popular culture, the term "Martial Arts" often specifically refers to the combat systems that originated in Asian cultures, especially East Asian martial arts. However, the term actually refers to any sort of codified combat systems, regardless of origin. Europe is home to many extensive systems of martial arts, both living traditions (e.g. Jogo do Pau and other stick and sword fencing and Savate, a French kicking style developed by sailors and street fighters) and older systems collectively referred to as historical European martial arts that existed until modern times and are now being reconstructed by several organizations. In the Americas, Native Americans have a tradition of open-handed martial arts, which includes wrestling, and Hawaiians have historically practiced arts featuring small and large joint manipulation. A mix of origins occur in the athletic movements of Capoeira, a practice that was created in Brazil by slaves and was based on skills brought with them from Africa. While each style has unique facets that make it different from other martial arts, a common characteristic is the systemization of fighting techniques. Methods of training vary and may include sparring or forms (kata), which are sets or routines of techniques that are performed alone, or sometimes with a partner, and which are especially common in the Asian and Asian-derived martial arts.[1]

Contents [hide]

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1 Variation and scope 2 History o 2.1 Asia  2.1.1 Early history  2.1.2 Recent history o 2.2 Europe o 2.3 Americas o 2.4 Africa o 2.5 Modern history 3 On the modern battlefield 4 Testing and competition o 4.1 Light- and medium-contact o 4.2 Full-contact o 4.3 Sparring debates 5 Martial sport 6 Dance 7 See also o 7.1 Styles 8 References

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9 External links

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[edit] Variation and scope Martial arts vary widely, and may focus on a specific area or combination of areas, but they can be broadly grouped into focusing on strikes, grappling, or weapons training. Below is a list of examples that make extensive use of one these areas; it is not an exhaustive list of all arts covering the area, nor are

these necessarily the only areas covered by the art but are the focus or best known part as examples of the area:

Some arts have a very specific focus while others, such as Mixed martial arts, are more syncretic. Striking • • •

Punching - Boxing (Western) Kicking - Capoeira, Savate, Taekwondo Other strikes (e.g. Elbows, knees, open-hand) - Muay Thai, Karate, Shaolin Kung Fu, Wing Chun

Grappling • • •

Throwing - Glima, Judo, Jujutsu, Sambo, Shuai jiao Joint lock - Aikido, Brazilian Jiu-Jitsu, Hapkido Pinning Techniques - Judo, Wrestling

Weaponry • •

Traditional Weaponry - Fencing, Gatka, Kendo, Silambam Modern Weaponry - Eskrima, Jogo do Pau, Jukendo, Modern Arnis

Many martial arts, especially those from Asia, also teach side disciplines which pertain to medicinal practices. This is particularly prevalent in traditional Chinese martial arts which may teach bone-setting, qigong, acupuncture, acupressure (tui na), and other aspects of traditional Chinese medicine.[2]

[edit] History Main article: History of martial arts Further information: Martial arts timeline Pictorial records of both wrestling and armed combat date to the Bronze Age ancient Near East, such as the 20th century BC mural in the tomb of Amenemhet at Beni Hassan, or the 26th century BC "Standard of Ur".

Ancient depiction of Shaolin monks practicing the art of self defense.

[edit] Asia [edit] Early history Main article: Asian martial arts (origins) The foundation of the Asian martial arts is likely a blend of early Chinese and Indian martial arts. Extensive trade occurred between these nations beginning around 600 BC, with diplomats, merchants, and monks traveling the Silk Road. During the Warring States period of Chinese history (480-221 BC) extensive development in martial philosophy and strategy emerged, as described by Sun Tzu in The Art of War (c. 350 BC). An early legend in martial arts tells the tale of a South Indian Pallava prince turned monk named Bodhidharma (also called Daruma), believed to have lived around 550 A.D. The martial virtues of discipline, humility, restraint and respect are attributed to this philosophy.[3] Shaolin Monastery was built by the Emperor Xiaowen of the Northern Wei Dynasty in AD 477. Batuo (also called Buddhabhadra), an Indian dhyana master becomes the first abbot of Shaolin Temple.[4] The teaching of martial arts in Asia has historically followed the cultural traditions of teacher-disciple apprenticeship. Students are trained in a strictly hierarchical system by a master instructor: Sifu in Cantonese or Shifu in Mandarin; Sensei in Japanese; Sabeom-nim in Korean; Guru in Sanskrit, Hindi, Telugu and Malay; Kruu in Khmer; Guro in Tagalog; Kalari Gurukkal or Kalari Asaan in Malayalam; Asaan in Tamil; Achan or Kru in Thai; and Saya in Myanmar. Though these may not translate literally as 'Master' [edit] Recent history Further information: Modern history of East Asian martial arts

Kalaripayat, an Indian martial art that witnessed a revival in 20th century

The Western interest in Asian martial arts dates back to the late 19th century, due to the increase in trade between the United States with China and Japan. Relatively few Westerners actually practiced the arts, considering it to be mere performance. Edward William Barton-Wright, a railway engineer who had studied Jujutsu while working in Japan between 1894–97, was the first man known to have taught Asian martial arts in Europe. He also founded an eclectic martial arts style named Bartitsu which combined jujutsu, judo, boxing, savate and stick fighting. Europe's colonisation of Asian countries also brought about a decline in local martial arts, especially with the introduction of firearms. Most clearly be seen in India after the full establishment of British Raj in the 19th century.[5] More European modes of organizing police, armies and governmental institutions, and the increasing use of firearms, eroded the need for traditional martial training associated with caste-specific duties.[5] and in 1804 the British Colonial government banned kalaripayat in response to a series of revolts.[6] Kalaripayat and other traditional arts experienced a resurgence in the 1920s in Tellicherry and spread throughout South India.[5] Similar phenomena occurred in other Southeast Asian colonies such as Malaysia, Indonesia, Vietnam and the Phillippines. Other Indian martial arts, such as Thang-Ta also witnessed a resurgence in the 1950s.[7] As Western influence grew in East Asia a greater number of military personnel spent time in China, Japan, and Korea. Exposure to martial arts during the Korean war was also significant. The later 1970s and 1980s witnessed an increased media interest in the martial arts, thanks in part to Asian and Hollywood martial arts movies. Jackie Chan and Jet Li are prominent movie figures who have been responsible for promoting Chinese martial arts in recent years.

[edit] Europe Main article: Historical European martial arts

Boxing was practiced in the ancient Mediterranean Martial arts existed in classical European civilization, most notably in Greece where sports were integral to the way of life. Boxing (pygme, pyx), Wrestling (pale) and Pankration (from pan, meaning "all", and kratos, meaning "power" or "strength") were represented in the Ancient Olympic Games. The Romans produced Gladiatorial combat as a public spectacle.

A number of historical fencing forms and manuals have survived, and many groups are working to reconstruct older European martial arts. The process of reconstruction combines intensive study of detailed combat treatises produced from 1400–1900 A.D. and practical training or "pressure testing" of various techniques and tactics. This includes such styles as sword and shield, two-handed swordfighting, halberd fighting, jousting and other types of melee weapons combat. This reconstruction effort and modern outgrowth of the historical methods is generally referred to as Western martial arts. Many Medieval martial arts manuals have survived, the most famous being Johannes Lichtenauer's Fechtbuch (Sword Tome) of the 14th century. Today Lichtenauer's tome forms the basis of the German school of swordsmanship. In Europe, the martial arts declined with the rise of firearms. As a consequence, martial arts with historical roots in Europe do not exist today to the same extent as in Asia, since the traditional martial arts either died out or developed into sports. Swordsmanship developed into fencing. Boxing as well as forms of wrestling have endured. European martial arts have mostly adapted to changing technology so that while some traditional arts still exist, military personnel are trained in skills like bayonet combat and marksmanship. Some European weapon systems have also survived as folk sports and as self-defense methods. These include stick-fighting systems such as bataireacht of Ireland, Jogo do Pau of Portugal and the Juego del Palo style(s) of the Canary Islands. Other martial arts evolved into sports that no longer recognized as combative. One example is the pommel horse event in men's gymnastics, an exercise which itself is derived from the sport of Equestrian vaulting. Cavalryriders needed to be able to change positions on their horses quickly, rescue fallen allies, fight effectively on horseback and dismount at a gallop. Training these skills on a stationery barrel evolved into sport of gymnastics' pommel horse exercise. More ancient origins exist for the shot put and the javelin throw, both weapons utilized extensively by the Romans.

[edit] Americas Native peoples of North America and South America had their own martial training which began in childhood. Some First Nations men, and more rarely some women, were called warriors only after they had proved themselves in battle. Most groups selected individuals for training in the use of bows, knives, blowguns, spears, and war clubs in early adolescence. War clubs were the preferred martial weapon because Native American warriors could raise their social status by killing enemies in single combat face to face.[citation needed] Warriors honed their weapons skills and stalking techniques through lifelong training. Capoeira, with great roots in Africa, is a martial art originating in Brazil that involves a high degree of flexibility and endurance. It consists of kicks, elbow strikes, hand strikes, head butts, cartwheels and sweeps. Jeet Kune Do is a martial arts system developed by martial artist and actor Bruce Lee. Its roots lie in Wing Chun, western boxing and fencing with a philosophy of a casting off what is useless and using no way as way. Brazilian Jiu Jitsu is an adaptation of pre-World War II Judo and jujutsu, developed by the brothers Carlos and Hélio Gracie, it was restructured into a sport with a large focus on groundwork. This system has become a popular martial art and proved to be effective in mixed martial arts competitions such as the UFC and PRIDE.[8] As of 2003, over 1.5 million US citizens practice martial arts.

[edit] Africa African knives may be classified by shape—typically into the 'f' group and the 'circular' group—and have often been incorrectly described as throwing knives.[9]There are also wrestling and grappling techniques found in West Africa. "Stick fighting" formed an important part of Zulu culture in South Africa, and is a

significant part of Obnu Bilate, a fighting form practiced in southern Botswana and Northern South Africa.

[edit] Modern history Wrestling, Javelin, Fencing (1896 Summer Olympics), Archery (1900), Boxing (1904), and more recently Judo (1964) and Tae Kwon Do (2000) are the martial arts that are featured as events in the modern Summer Olympic Games. Martial arts also developed among military and police forces to be used as arrest and self-defense methods including: Kapap and Krav Maga developed in Israeli Defense Forces; San Shou in Chinese; Systema: developed for the Russian armed forces and Rough and Tumble (RAT): originally developed for the South African special forces (Reconnaissance Commandos) (now taught in a civilian capacity). Tactical arts for use in close quarter combat warfare, i.e. Military Martial arts e.g. UAC (British), LINE (USA). Other combative systems having their origins in the modern military include Soviet Bojewoje (Combat) Sambo. Pars Tactical Defence (Turkei security personally self defence system) Inter-art competitions came to the fore again in 1993 with the first Ultimate Fighting Championship this has since evolved into the modern sport of Mixed martial arts.

[edit] On the modern battlefield

U.S. Army Combatives instructor Matt Larsen demonstrates a chokehold Some traditional martial concepts have seen new use within modern military training. Perhaps the most recent example of this is point shooting which relies on muscle memory to more effectively utilize a firearm in a variety of awkward situations, much the way an iaidoka would master movements with their sword. During the World War II era William E. Fairbairn, a Shanghai policeman and a leading Western expert on Asian fighting techniques, was recruited by the Special Operations Executive (SOE) to teach Jujutsu to

U.K., U.S. and Canadian Special Forces. The book Kill or Get Killed, written by Colonel Rex Applegate, became a classic military treatise on hand-to-hand combat. This fighting method was called Defendu. Traditional hand-to-hand, knife, and spear techniques continue to see use in the composite systems developed for today's wars. Examples of this include the US Army's Combatives system developed by Matt Larsen, the Israeli army trains its soldiers in Krav Maga, the US Marine Corps's Marine Corps Martial Arts Program (MCMAP), and Chinese San Shou. Unarmed dagger defenses identical to that found in the fechtbuch of Fiore dei Liberi and the Codex Wallerstein were integrated into the U.S. Army's training manuals in 1942[10] and continue to influence today's systems along with other traditional systems such as Eskrima. The rifle-mounted bayonet, which has its origin in the spear, has seen use by the United States Army, the United States Marine Corps, and the British Army as recently as the Iraq War.[11]

[edit] Testing and competition Testing or evaluation is important to martial art practitioners of many disciplines who wish to determine their progression or own level of skill in specific contexts. Students within individual martial art systems often undergo periodic testing and grading by their own teacher in order to advance to a higher level of recognized achievement, such as a different belt color or title. The type of testing used varies from system to system but may include forms or sparring. Various forms and sparring are commonly used in martial art exhibitions and tournaments. Some competitions pit practitioners of different disciplines against each other using a common set of rules, these are referred to as mixed martial arts competitions. Rules for sparring vary between art and organization but can generally be divided into light-contact, medium-contact, and full-contact variants, reflecting the amount of force that should be used on an opponent.

[edit] Light- and medium-contact These types of sparring restrict the amount of force that may be used to hit an opponent, in the case of light sparring this is usual to 'touch' contact, e.g. a punch should be 'pulled' as soon as or before contact is made. In medium-contact (sometimes referred to as semi-contact) the punch would not be 'pulled' but not hit with full force. As the amount of force used is restricted, the aim of these types of sparring is not to knock out an opponent; a point system is used in competitions. A referee acts to monitor for fouls and to control the match, while judges mark down scores, as in boxing. Particular targets may be prohibited (such as the face or groin), certain techniques may be forbidden, and fighters may be required to wear protective equipment on their head, hands, chest, groin, shins or feet. In grappling arts aikido uses a similar method of compliant training that is equivalent to light or medium contact. In some styles (such as fencing and some styles of taekwondo sparring), competitors score points based on the landing of a single technique or strike as judged by the referee, whereupon the referee will briefly stop the match, award a point, then restart the match. Alternatively, sparring may continue with the point noted by the judges. Some critics of point sparring feel that this method of training teaches habits that result in lower combat effectiveness. Lighter-contact sparring may be used exclusively, for children or in other situations when heavy contact would be inappropriate (such as beginners), medium-contact sparring is often used as training for full-contact.

[edit] Full-contact "Full-contact" sparring or fighting is considered by some to be requisite in learning realistic unarmed combat.[12] Full-contact sparring is different from light and medium-contact sparring in several ways, including the use of strikes that are not pulled but are thrown with full force, as the name implies. In fullcontact sparring, the aim of a competitive match is either to knock out the opponent or to force the opponent to submit. Full-contact sparring may include a wider variety of permitted attacks and contact zones on the body. Where scoring takes place it may be a subsidiary measure, only used if no clear winner has been established by other means; in some competitions, such as the UFC 1, there was no scoring, though most now use some form of judging as a backup.[13] Due to these factors, full-contact matches tend to be more aggressive in character, but rule sets may still mandate the use of protective gloves and forbid certain techniques or actions during a match, such as punching the back of the head. Nearly all mixed martial arts leagues such as UFC, Pancrase, Shooto use a form of full-contact rules, as do professional boxing organizations and K-1. Kyokushin karate requires advanced practitioners to engage in bare-knuckled, full-contact sparring while wearing only a karate gi and groin protector but does not allow strikes to the face, only kicks and knees. Brazilian Jiu-Jitsu and Judo matches do not allow striking, but are full-contact in the sense that full force is applied in the application during grappling and submission techniques.

[edit] Sparring debates Some practitioners believe that sports matches with rules are not a good measure of hand-to-hand combat ability and training for these restrictions may inhibit effectiveness in self defence situations. These practitioners may prefer not to participate in most types of rule-based martial art competition (even one such as vale tudo where there are minimal rules), electing instead to study fighting techniques with little or no regard to competitive rules or, even perhaps, ethical concerns and the law (the techniques practiced may aim to kill or cripple the opponent). Others maintain that, given proper precautions such as a referee and a ring doctor, sparring, in particular full-contact matches with basic rules, serves as a useful gauge of an individual's overall fighting ability, and that failing to test techniques against a resisting opponent is more likely to impede ability in self defence situations.

Several martial arts, such as Judo, are Olympic sports.

[edit] Martial sport

Judo and Tae Kwon Do as well as western archery, boxing, javelin, wrestling and fencing are currently events in the Summer Olympic Games. Chinese wushu recently failed in its bid to be included, but is still actively performed in tournaments across the world. Practitioners in some arts such as kickboxing and Brazilian Jiu-Jitsu often train for sport matches, whereas those in other arts such as Aikido and Wing Chun generally spurn such competitions. Some schools believe that competition breeds better and more efficient practitioners, and gives a sense of good sportsmanship. Others believe that the rules under which competition takes place have diminished the combat effectiveness of martial arts or encourage a kind of practice which focuses on winning trophies rather than a focus such as cultivating a particular moral character. As part of the response to sport martial arts, new forms of competition are being held such as the Ultimate Fighting Championship in the U.S. or Pancrase, DREAM, and Shooto in Japan which are also known as mixed martial arts (or MMA) events. The original UFC was fought under very few rules allowing all martial arts styles to enter and not be limited by the rule set. Some martial artists also compete in non-sparring competitions such as breaking or choreographed techniques poomse, kata or aka. Modern variations of the martial arts include dance-influenced competitions such as tricking. Some martial traditions have been influenced by governments to become more sport-like for political purposes. The central impetus for the attempt by the People's Republic of China in transforming Chinese martial arts into the committee-regulated sport of Wushu was suppressing what they saw as the potentially subversive aspects of martial training, especially under the traditional system of family lineages.[14]

[edit] Dance As mentioned above, some martial arts in various cultures can be performed in dance-like settings for various reasons, such as for evoking ferocity in preparation for battle or showing off skill in a more stylized manner. Many such martial arts incorporate music, especially strong percussive rhythms. Examples of such war dances include:

Capoeira is a martial art traditionally performed with a dance-like flavor and to live musical accompaniment, as seen depicted here. • • • • • • • •

Buza - From Russia. Panther Dance - Burmese Bando with swords (dha) Gymnopaidiai - ancient Sparta European Sword dance or Weapon dance of various kinds Haka - New Zealand Sabre Dance - depicted in Khachaturian's ballet Gayane Maasai moran (warrior age-set) dances Aduk-Aduk - Brunei

• • • • • • •

Ayyalah - Qatar Khattak Dance - Afghanistan and Pakistan Brazil's Capoeira, as well as some similar Afro-Caribbean arts Dannsa Biodag - Scotland and Scottish sword dances Hula & Lua - from the traditions of indigenous Hawaiian Combat Hopak - From Ukraine Yolah - From Oman/UAE

[edit] See also Martial arts portal

Wikimedia Commons has media related to: Martial arts • • •

For a time line of martial arts historical milestones, see Martial arts timeline For a detailed list of martial arts weapons, see List of martial arts weapons For other related topics, see List of martial arts-related topics

[edit] Styles Over time, the number of martial arts has grown and multiplied, with hundreds of schools and organizations around the world currently working towards myriad goals and practising a huge variety of styles. • •

For a detailed list of martial arts styles see: List of martial arts For a detailed list of fictional martial arts, see List of fictional martial arts

Entertainment From Wikipedia, the free encyclopedia

Jump to: navigation, search This article may need to be rewritten entirely to comply with Wikipedia's quality standards. You can help. The discussion page may contain suggestions. See also Entertainment (disambiguation) and The Entertainer (disambiguation)

A mime working for tips entertaining crowd in Paris, France

Entertainment is an activity designed to give people pleasure or relaxation. An audience may participate in the entertainment passively as in watching opera or a movie, or actively as in games.[1] The playing of sports and reading of literature are usually included in entertainment, but these are often called recreation, because they involve some active participation beyond mere leisure The industry that provides entertainment is called the entertainment industry.

Contents [hide]

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1 Examples of entertainment o 1.1 Animation o 1.2 Cinema o 1.3 Theatre o 1.4 Circus o 1.5 Comedy o 1.6 Comics o 1.7 Dance o 1.8 Reading o 1.9 Games o 1.10 Music o 1.11 Other forms of entertainment 2 See also 3 Footnotes

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4 External links

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[edit] Examples of entertainment [edit] Animation

Wikipe-tan sailor fuku is a character in Japanese animation. Animation provides moving images that are generated by an artist, in contrast to the live action normally used in motion pictures. It is typically accompanied by a sound track consisting of recordings of live actors. Animation is often used in computer-based forms of entertainment.

Cartoons are a comedic form of animation.[2] Anime or TV manga refers to animation originating from Japan in the Occidental use of the word. In Japan the word refers to all animation. It may contain adult themes and futuristic locations.[3]

[edit] Cinema Cinema provides moving pictures as an art form. Cinema may also be called films or movies.[4] A film produces an illusion of motion by presenting a series of individual image frames in rapid succession. Films are produced by a crew that handle the cameras, sets and lighting. The cast consists of actors who appear in front of the camera and follow a script. After the film has been shot, it is edited then distributed to theaters or television studios for viewing.

[edit] Theatre Theatre encompasses live performance such as plays, musicals, farces, monologues and pantomimes.

Circus act - fire breather

[edit] Circus Circus acts include acrobats, clowns, trained animals, trapeze acts, hula hoopers, tightrope walkers, jugglers, unicyclists and other stunt-oriented artists.[5] Circuses are a great place for families.

[edit] Comedy Comedy provides laughter and amusement. The audience is taken by surprise, by the parody or satire of an unexpected effect or an opposite expectations of their cultural beliefs. Slapstick film, one-liner joke, observational humor are forms of comedy which have developed since the early days of jesters and traveling minstrels.[6]

[edit] Comics

Felix the Cat Comic Strip Comics comprise of text and drawings which convey an entertaining narrative.[7] Several famous comics revolve around super heroes such as Superman, Batman. Marvel Comics and DC Comics are two publishers of comic books. Manga is the Japanese word for comic and print cartoons. Caricature is a graphical entertainment. The purpose may vary from merely putting smile on the viewers face, to raising social awareness, to highlighting the moral vices of a person being caricaturised.

[edit] Dance

Dancing Dance refers to movement of the body, usually rhythmic and to music,[8] used as a form of expression, social interaction or presented in a spiritual or performance setting. Dance includes ballet, cancan, Charleston, Highland fling, folk dance, sun dance, modern dance, polka and many more.[9]

[edit] Reading Reading comprises the interpretation of written symbols.[10] An author, poet or playwright sets out a composition for publication to provide education or diversion for the reader. The format includes paperback or hard cover books, magazines, periodicals, puzzle books, crossword magazines and coloring books. Fantasy, horror, science fiction and mystery are forms of reading entertainment.

[edit] Games

Playing Bingo Games provide relaxation and diversion usually following a rule set. Games may be played by one person for their own entertainment, or by a group of people. Games may be played for achievement or money such as gambling or bingo. Racing, chess or checkers may develop physical or mental prowess. Games may be geared for children, or may be played outdoors such as lawn bowling. Equipment may be necessary to play the game such as a deck of cards for card games, or a board and markers for board games such as Monopoly, or backgammon.[11] A few may be ball games, Blind man's bluff, board games, card games, children's games, Croquet, Frisbee, Hide and seek, Number games, Paintball, and Video games to name a few.

[edit] Music

Musical Piece: Ludwig van Beethoven - Symphony no. 5 in C minor Music is a art form combining rhythm, melody, harmony for entertainment, ceremonial or religious purposes.[12]

[edit] Other forms of entertainment • • • • • • • • •

Concert Lecture Magic Sports Mass media Revue Television Radio Storytelling

A juggler entertains outdoors in Devizes, Wiltshire, England

[edit] See also Main list: List of basic entertainment topics • • • • • •

Broadway theatre History of film Leisure Escapism Literature West End theatre

[edit] Footnotes 1. ^ "entertainment - Definitions from Dictionary.com". Lexico Publishing Group, LLC. (2007). Retrieved on 2007-11-30. 2. ^ "cartoon - Definitions from Dictionary.com". Lexico Publishing Group, LLC. (2007). Retrieved on 2007-11-30. 3. ^ "anime - Definitions from Dictionary.com". Lexico Publishing Group, LLC. (2007). Retrieved on 2007-11-30. 4. ^ Harper, Douglas gfg (2001). "fdgfg cinema- Definitions from Dictionary.com". rOnline Etymology Dictionary fd fdf. Lexico Publishing Group, LLC.. Retrieved on 2007-11-30. 5. ^ Hoh, Lavahn G. (2004). "The Circus in America: 1793–1940". The Institute for Advanced Technology in the Humanities. University of Virginia. Retrieved on 2007-11-30. 6. ^ "comedy". From: The Columbia Encyclopedia, Sixth Edition. HighBeam Research, Inc. (2007). Retrieved on 2007-11-30. 7. ^ "comic strip comic strip". Britannica Online Encyclopedia. Encyclopædia Britannica, Inc. (2007). Retrieved on 2007-11-30. 8. ^ "britannica". 9. ^ "Encyclopedia: Dance — Infoplease.com". Pearson Education, publishing as Infoplease (2000– 2007). Retrieved on 2007-11-30. 10. ^ "reading - Encyclopedia.com". HighBeam Research, Inc (2007). Retrieved on 2007-11-30. 11. ^ "Games - MSN Encarta". Microsoft (2007). Retrieved on 2007-11-30. 12. ^ "music - definition of music by the Free Online Dictionary, Thesaurus and Encyclopedia". Farlex, Inc. (2007). Retrieved on 2007-11-30.

[edit] External links Look up entertainer in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Category:Entertainment

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Entertainment at the Open Directory Project Entertainment

Retrieved from "http://en.wikipedia.org/wiki/Entertainment" Category: Entertainment Hidden category: Wikipedia articles needing rewrite