Eclipses Are The Shadows Formed In Nature1

Eclipses are the shadows formed in nature. The Sun, the source of light when throws light rays on opaque objects such as the earth and the moon the shadows are formed. The shadows cast by the earth and the moon are called Eclipses.

Take a torch and a ball. Tie a thread around the ball and let it hang from the ceiling. At some distance on one side of the ball send your friend with the torch. Ask him to switch on the torch. You take up your position on the other side of the ball. Can you see the torch bulb? Yes/No

You cannot see the bulb because the ball has come in between you and he torch. Torch is like the sun. Just as you are not able to see the bulb because the ball has come inbetween you and the torch, and the shadow of the ball is casted, similarly, we are not able to see the sun when moon comes in-between the sun and the earth and forms a shadow and we call it solar eclipse.

There are two types of eclipses:

• Solar Eclipse • Lunar Eclipse When the moon, the earth and the sun are in a straight line such that the moon is in between the earth and the sun, solar eclipse occurs. When this happens as the below indicates, the shadow of the moon falls on the earth.

Shadow of moon on earth causes solar eclipse.

There are three types of solar eclipses:

• Total Solar Eclipse • Partial Solar Eclipse • Annular Solar Eclipse

Total Solar Eclipse Total solar eclipses occur when the umbra of the Moon’s shadow touches a region on the surface of the Earth.

Penumbra - Faint outer shadow; partial eclipses are seen from within this shadow.

Umbra- Dark inner shadow; total eclipses are seen from within this shadow.

Partial Solar Eclipse Partial Solar Eclipses occurs when a part of the sun is not visible or when only a part of the sun is visible. Moon (Sun is hidden

M oon Sun

Annular Solar Eclipse Annular Solar Eclipses occur when a region on the Earth's surface is in line with the umbra, but the distances are such that the tip of the umbra does not reach the Earth's surface.

As illustrated in the figure below, in a total eclipse the surface of the Sun is completely blocked by the Moon, in a partial eclipse it is only partially blocked, and in an annular eclipse the eclipse is partial, but such that the apparent diameter of the Moon can be seen completely against the (larger) apparent diameter of the Sun. A given solar eclipse may be all three of the above for different people. For example, in the path of totality (the track of the umbra on the Earth's surface) the eclipse will be total, in a band on either side of the path of totality the shadow cast by the penumbra leads to a partial eclipse, and in some eclipses the path of totality extends into a path associated with an annular eclipse because for that part of the path the umbra does not reach the Earth's surface.

When the earth, the moon and the sun are in the straight line such that the earth is in between the sun and the moon, the shadow of the earth falls on moon and the moon cannot be seen because it cannot be illuminated by the sun. However some light falls on the moon due to the earth’s atmosphere. Therefore, the moon does not disappear but appears reddish brown. At this stage moonlight does not reach the earth and it becomes a dark night.

Shadow of earth on moon causes Lunar Eclipse. Since the moon is revolving around the earth, it comes out of the shadow of the earth as it revolves. Lunar eclipse therefore ends. Since the moon completes one revolution around the earth in 28 days (approximately one month), once a month it must come in straight line with the earth and the sun. But an eclipse does not occur once in a month because the planes on which

moon moves are not the same. The two planes are slightly titled at an angle.

• • •

Partial Lunar Eclipse Total Lunar Eclipse Penumbral Lunar Eclipse

Partial Lunar Eclipse: During partial lunar eclipse only a part of moon is visible and the part of the moon that falls under the umbra of the earth is not visible.

Total Lunar Eclipse: When the whole moon is in the umbra of the earth, it is known as total lunar eclipse. We cannot see the moon at all; therefore, the night becomes totally dark. When the moon comes out of the umbra, it becomes visible again.

Penumbral Lunar Eclipse: Moon misses the umbra completely, only passes through the penumbral shadow. Even the birds feel the occurrence of total solar eclipse. People noticed and observed that even at about 2 p.m. during the occurrence of total solar eclipse the birds started behaving as night had fallen. They started returning to their nests. They could be seen flying in the sky to return home. They too must have been wondered struck with the duration of night for just few seconds.

All observers, whether you are student, an amateur or a astronomer, you must remember:

a teacher, a professional

NEVER EVER LOOK THROUGH AN UNSHIELDED TELESCOPE AIMED AT THE SUN OR THE PARTIALLY ECLIPSED SUN! If (with or without telescope) you stare at the Sun without a safe filter permanent eye damage can occur within less than a second. The tremendous heating power of sunlight is easily demonstrated using a magnifying lens (a burning glass). The only time it is completely safe to look at the Sun without filter is during the totality.

To view the eclipsed sun, make a pinhole in a cardboard. Place it perpendicular to the sun. Its image fall on the screen or wall through the pinhole. You can view this image. There are special glasses through which the rays of the sun are blocked but the view of the sun is very clear. This eclipsed sun is safe to view through them.

• At first thought, it would seem that we should have an eclipse each month when the moon passes between the Sun and the Earth. Why not? • The answer lies in the slight tilt (5o) of the Moon’s path in relation to the Earth’s path. It is usually above or below the direct sight line to the Sun.

Sun­Earth line

Earth

Moon’s tilted orbit

Bibliography

Science And Technology Book Of Class 7th • Yahoo Search • Google Search •