Space And Physics Yr10

Focus 1 Our understanding of the nature of the universe has changed over time and the latest theory is the Big Bang 1.1Outline the features of nebulae, stars, galaxies, planets, quasars, black holes • Nebulae: glowing clouds of gas and dust, reflecting the light of nearby stars o Emission nebula: interstellar plasma which absorbs and re-emits electromagnetic radiation from close by hot young stars. o Reflection nebula: dust particles which scatter and reflect light from nearby bright young stars o Planetary nebulae: glowing shell of gas and plasma ejected from a low mass star near the end of the star’s life • Stars: luminous body of interstellar gas held together by gravity o Protostar: the earliest stage in a stars development. A protostar represents a region in which the density of the interstellar medium is increasing due to gravitational effects and in the process of collapsing to form a true star o Main sequence: stars that burn hydrogen in their cores are called main sequence stars. They are the most prominent stars in space. o Red Giant: dying phase of a star, where the outer shell has collapsed, and hydrogen is being used as a fuel. It emits weak (red) radiation o White Dwarf: the extremely dense core of a dead star, it forms after a Red Giant runs out of fuel. The outer layer has been shed to form a planetary nebula but the core is still extremely hot and dense. If a white dwarf gains mass it may become a supernova o Black Dwarf: a cooled down white dwarf that no longer emits heat or light. None exist yet o Brown Dwarf: formed when gas contracts to form a star, but there’s not enough of it to sustain for burning and form a star. o Pulsating Star: Dims and brightens as its surface expands and contracts o Binary Stars: two stars in orbit around a common centre of mass. Binaries are used to measure the mass of a distant star. The gravitational pull between individual stars of a binary causes each to orbit around the other o Double Stars: two stars that appear as one because they are in the same direction as each other when seen from earth. They aren’t orbiting each other as binaries are, and they are often very distant from each other. o Neutron Stars: a neutron star is formed from the collapsed remnant of a massive star, often a supernova. They are much denser than white dwarfs but not as dense as black holes. o Nova: nuclear explosion caused by hydrogen adding into a white dwarf star o Supernova: when a stars nuclear fuel is used up it is no longer supported by the release of nuclear energy. If the star is particularly big, then its core will collapse and in so doing will release a huge amount of energy. This will cause a blast wave that ejects the stars envelope into space. The result of the collapse may be, in some cases, a rapidly rotating neutron star that can be observed many years later as a pulsar. • Galaxy: vast system of stars and star systems, nebulae, interstellar gas and dust, plasma, and (possibly) unseen dark matter, all orbiting a common centre of gravity • Quasar: an enormous source of electromagnetic energy, including light, that dwarfs the energy output of the brightest stars. A quasar may release energy equal to the output of dozens of galaxies. It looks like a very faint star and has a very high red shift, so must be very distant

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Black hole: Concentration of mass so big that the force of gravity prevents anything from escaping it. Not even light can escape its gravity, hence the word “black”. It does not refer to a “hole” in the visual sense, but rather a region of space from which nothing can return Plasma: distinct phase of matter, separate from the traditional solids, liquids, and gases. It is a collection of charged particles that respond strongly and collectively to electromagnetic fields, taking the form of gas-like clouds or ion beams. Frequently described as ionized gas Planets: bodies revolving around a star

1.2Identify and describe the main features of the big bang theory • Theory: states that the universe was formed about 13.7 billion years ago (+ / - 1%) as the result of a giant explosion of very dense and hot matter. This matter expanded and started to cool down, going through different transitional phases. The universe has been expanding ever since. • Sequence o Approx 15 billion years ago:  Big Bang occurs.  Universe begins with a cataclysm that creates space and time, as well as all the matter and energy the universe will ever hold o <1 second after:  universe continued to expand but not nearly as quickly  becomes less dense  gravity emerges and matter forms  building block particles of quarks, leptons, photons and neutrinos form  rapidly cooling cosmosquarks combine to form protons and neutrons  protons and neutrons will eventually form the nuclei of all atoms (e.g. the atomic nuclei of hydrogen, helium and lithium) o 3 minutes after:  still too hot to form into atoms  charged electrons and protons prevent light from shining o 10 000 years after:  Radiation era – most energy in the form of radiation  different wavelengths of light, x-rays, radio waves and ultra violet waves  as universe expanded, the radiation waves were stretched and diluted o 300 000 years after:  average temperature has cooled to 5000 degrees Fahrenheit  energy in matter and energy in radiation are equal  electrons combine with protons and neutrons to form atoms (mostly hydrogen and helium)light can finally shine  universe keeps expandingstretching of the light wavesdriven into lower and lower energy; matter continued outward largely unaffected  electrons can now remain in orbit around atomic nuclei  hydrogen and helium atoms would eventually form as fuel for the stars o 300 000 000 years after:  force of gravity begins to affect the irregularities in the density of the gaseous matter  universe continues to expand rapidlypockets of gas are formed, becoming more and more dense. Within these pockets, stars are ignited. As they form, groups of them become the earliest galaxies o Approx 10 billion years after (5 bill years ago):  Our sun forms within a cloud of gas in a spiral arm of what we now call the Milky Way galaxy.

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huge cloud of gas and debris surround this new stargives birth to planets, moons and asteroids

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Evidence o Light from distant galaxies is ‘red-shifted’, i.e. shifted towards red (longwavelength) end of the spectrum  sign that galaxies are rushing apart at great speed and that the universe is expanding o Microwave radiation can be detected from distant galaxies. Astronomers previously predicted that microwave radiation would be given of by a rapidly expanding universe o The relative abundance of the light elements such as Hydrogen and Helium in the universe supports the Big Bang Theory o Star like objects, quasars, were discovered further away than any known object. Quasars are unlike anything else in the universeuniverse must have been different in the pastcontradicts Steady State Theory 1.3Recall the main features of a scientific theory and a law • Theory: explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of scientist Components of it can be changed or improved upon in attempt to make them more elegant and concise or to make them more all-encompassing, without changing the overall truth of the theory as a whole. • Law: statement of fact meant to explain, in concise terms, an action or set of actions. Generally accepted to be true and universal, and may sometimes be expressed in terms of a single mathematical equation. 1.4Outline evidence for the Big Bang Theory (see 1.2) 1.5Outline some previously accepted ideas about the origin of the universe and explain why they have been replaced by the Big Bang Theory • Steady State theory: o Proposes that the universe exists in a steady state (is unchanging and has a constant mean density). To account for the expansion of the universe, this theory indicates that matter is being created to fill the spaces produces during expansion and in this way maintains a constant density o States that our universe looks the same at all times from all directions o Universe has no beginning and no end o States that the large quantities of helium and hydrogen in the universe are created by supernovae o Problems include:  See 1.2 evidence  Discovery of cosmic microwave background radiation. Steady State theory explained it as light from ancient stars which has been absorbed and emitted in all directions by galactic particles. Microwave radiation discovered was very smoothmeaning it did not come from different small sourcescontradicts SS theory’s explanation

Focus 2 Our knowledge of the universe is based mainly on the interpretation of electromagnetic radiation that arrives on Earth 2.1 Review the nature of electromagnetic radiation • Consists of oscillating (regularly vibrating) electric and magnetic fields and does not require a medium to travel. • In air all types of electromagnetic radiation travel at the same speed (300 000 km/s) but have different wavelengths and frequencies. • The energy of an electromagnetic wave depends on its frequency.

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Wave with high frequency (e.g. gamma rays) transfer more energy than those with lower frequency (e.g. radio waves).

2.2 Describe how waves can be reflected and relate this to the working of optical and radio telescopes • Waves are reflected when they come into contact with a barrier. The angle of incidence is equal to the angle of reflection on a smooth surfaced barrier. However on a rough surface, the reflected waves are scattered due to the bumps • Optical telescopes: collect and detect light coming from objects and magnifies what the human eye sees. These telescopes use lenses (refracting telescopes) or mirrors (reflecting telescopes) or a combination of lenses and mirrors • Radio telescopes: consist of a large dish that collects radio waves, which are reflected onto a small aerial tuned to a particular wavelength. The signals are amplifies and passed to a receiver in a control room 2.3 Describe the difficulties that telescopes encounter in gathering information from the universe including absorption by atmosphere, light pollution, immensity of the distances, and loss of intensity with distance • Atmospheric distortion limits the resolution of terrestrial telescopes • Visible light can be detected by reflecting and refracting telescopes. Atmospheric pollution and glare from artificial lighting interfere with observations • Radio waves from space are collected by the large dishes of radio telescopes. They are reflected onto a small aerial, amplified and sent to computer recording equipment where they produce pictures and are studied. Radio waves travel through the atmosphere but may be distorted by interference from electronic devices (e.g. radios and microwave appliances) Radar (high frequency radio waves) is used to study the surfaces of planets, including the Earth. • X-rays are collected on special X-ray telescopes. They have been developed to detect and focus X-rays from space and produce images. The atmosphere absorbs most X-rays coming from space so the X-ray telescopes are placed on artificial satellites (e.g. the Einstein Observatory) • Infrared radiation coming from space is collected on special instruments on satellites (e.g. the Space Infrared Telescope Facility). Some infrared radiation enters the atmosphere but is interfered with by re-radiated heat from the Earth. New technology has now been developed to overcome this problem and enable some infrared astronomy from Earth. • Ultraviolet radiation from space is mostly filtered out by the ozone layer, so ultraviolet astronomy is conducted from satellites (e.g. the International Ultraviolet Explorer)

Focus 3 Electromagnetic radiation from the universe can be used to determine the size and temperature of the stars and their distance from the Earth 3.1 Relate temperature to wavelength of radiation emitted from hot bodies • All objects emit electromagnetic radiationamount of radiation emitted at each wavelength determines the temperature of the object • Shorter (bluer) wavelengthhotter objects; Longer (redder) wavelengthscooler objects 3.2 Explain how the colour of a star can be used to estimate its surface temperature • Amount of light produced by an object at each wavelength depends on the temperature of the object producing the light

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Stars over 6000oC put out most of their light in the blue/ultraviolet regions of the spectrum. Stars below 5000oC put out most of their light in the red/infrared regions of the spectrum.

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Generally, massive stars burn more fuel and are hotter and brighter than less massive stars Colour also gives an indication of the star’s age Red Yellow White Blue

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younger, smaller mature, larger cooler (3000 oC), less bright hotter (20 000 oC), brighter • Exceptions are stars at the end of their life o Red giants – large, cool and bright; White Dwarfs – small, hot and faint Focus 4 Stars are part of a dynamic universe and change over time 4.1 Describe the sequence of stellar evolution and relate different pathways to mass • Nebula – protostar – main sequence – red giant (supergiant) – white dwarf (black hole/neutron star) – brown star

4.2 Classify stars using an HR diagram & 4.3 Extract information from HR diagram and recognize the following groups – main sequence, red giants, white dwarfs, supergiants

Focus 5 The universe is held together by gravity 5.1 Distinguish between the terms mass and weight • Mass: amount of matter in an object or substance. Measured in grams(g) / kilograms(kg) • Weight: force of gravity pulling down on an object. Measure in newtons (N) 5.2 Define gravitational attraction as a force that exists between any two bodies that have mass. F= G Mm/d2 • Gravitational force: force of attraction that exists between all matter in the universe • Attraction between two objects depends on their masses and the distance between them

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Gravitational force becomes less when objects are further apart • F = G Mm/d2 ; where F is force, G is the gravitational pull / acceleration due to gravity (9.8 on earth), M and m are the masses of the two different objects, d is the distance between the objects 5.3 Calculate the acceleration due to gravity on the surface of the earth and other planets in the solar system

Focus 6 Travel to other parts of the solar system uses rockets and gravity 6.1 Identify real life situations of Newton’s 3 laws of motion in action (Sir Isaac) Newton’s 3 laws of motion describe the motion of objects: • First law of motion: o An object continues in its state of rest or uniform motion in a straight line unless there is an unbalanced force acting on it o Property of an object that tends to make it resist a change in motion (inertia) • Second law of motion: o Acceleration of an object is proportional to the unbalanced or net force acting on it, providing the mass remains constant  F = ma; F is force (N), m is mass (kg), a is acceleration (m/s/s or ms-2)  Acceleration increases,force increases(provided that the mass remains the same) • Third law of motion: o If an object applies a force on another, the second object applies an equal and opposite force back (for every action force there is an equal and opposite reaction force) 6.2 Apply Newton’s laws to explain how a rocket works • Rocket lifting off from the launch pad:  thrust exceeds the force keeping the rocket in place (weight of the rocket and payload caused by Earth’s gravity)  thrust of rocket engine is greater than weight of the rocket & net force accelerates the rocket away from the pad  reflects Newton’s First Law of Motion (object at rest will stay at rest as long as no unbalanced force is applied) • Rocket being launched: two forces acting on it (1)weight of the rocket, force generated by the gravitational attraction of Earth on the rocket (2)thrust, the force that moves the rocket heavier the rocketmore thrust needed to get it off the ground amount of thrust determined by: (1)mass of rocket propellant that is combusted (creating exhaust) (2)speed at which the exhaust is vented from the rocket reflects Newton’s Second Law of Motion (force=mass x acceleration) • High-speed exhaust moves in one direction propels rocket in the opposite direction Newton’s Third Law of Motion (for every action there is an equal and opposite reaction)

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Thrust must be carefully controlled when rockets or payloads (e.g. satellites) are launched into space orbit. Too much thrust or thrust at the wrong time satellite placed in wrong orbit Too little thrust satellite falls back to Earth.

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After rocket is airborne, another force comes into play drag  Drag: rocket's resistance to motion caused by the rocket's movement through air It depends on several factors: density of the air shape of the rocket roughness of the rocket’s surface The more resistant to motion a rocket ismore thrust is needed to propel it. The nose cones of rockets  help reduce drag. Model rockets experience drag along their entire flight path because they are moving through Earth's atmosphere. Rockets that move through space do not experience drag because there is no atmosphere. For a rocket to continue to ascend:  thrust must be greater than:  the weight of the rocket  any drag forces Once a model rocket uses all of its fuel: it no longer accelerates Earth's gravity continues to act on this rocket to slow it down. If the rocket's speed is slow enough, Earth's gravity eventually will pull it back to Earth. If the rocket's speed is: 17,500 miles per hour - fast enough to go into orbit around Earth. exceeds 25,000 miles per hour - rocket is able to escape Earth completely and goes into an independent orbit around our Sun to explore other planets and regions of our solar system.

6.3 Define speed, acceleration, force • Speed: o Speed on an object is the distance travelled in unit time o Measured in km/h or m/s o v = s/t (average speed = distance / time taken) • Acceleration: o Acceleration is the rate at which velocity changes. An object is accelerating if it speeds up, slows down (negative acceleration or deceleration) or changes direction.  a = v – u (change in velocity) t  a is average acceleration, v is final velocity, u is initial velocity, t is time • Force: o A push or pull o Capable of changing the speed of an object, its direction of motion or its shape o Measured in newtons (N) o F = m x a (force = mass x acceleration) (Newtons 2nd law of motion) o Forces occur in pairs; for every action there is a reaction (Newtons 3rd law of motion) o When acting forces are balanced (forces are equal) - object is at rest (not moving) or moving at a uniform speed in a straight line o When acting forces are unbalanced (one force is greater than the other) – object starts to move, speed up, slow down, stop or change direction

 there is a net force in one direction • Velocity of an object is the rate at which its position changes in a certain direction (displacement in unit time) o Velocity (m/s or ms-1)= displacement time 6.4 Solve problems using the equations of motion Equations of motion: • v=s/t  u = initial velocity [in metres per • a=v–u/t second (m/s or ms-1)] • v=u+(axt)  v = final velocity [in metres per • s = ( u x t ) + ( ½ a x t2) second (m/s or ms-1)] 2 2 • v =u + (2xaxs)  a = acceleration [in metres per second  t = time [in seconds (s)] per second (m/s/s or ms-2)]  s = distance (displacement) (m) 6.5 Construct and interpret motion graphs – distance vs time and speed vs time