There are many bodies in space. The sun shines on these bodies. A body in space may also block the sunlight and cast a shadow on another body, making it look dark. The darkening of a body in space is called an eclipse. Find out how an eclipse of the sun or moon happens.

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Solar Eclipse

When a bright day suddenly turned into night because the sun became completely dark is called total solar eclipse. In total solar eclipse, the moon completely blocks the view of the sun. How can the moon completely block the view of the sun when the sun is very much bigger? The sun may be very big, but it is very far from Earth. The moon is small but it is nearer to Earth. So, the sun and the moon appear to be of almost the same size in the sky. During a total solar eclipse, the sky becomes dark and some stars can be seen. The darkness may last for only a few minutes. As the moon moves on, the sun becomes bright again. A total solar eclipse can be seen only in places which lie in the path where the moon’s shadow passes across Earth. When the moon blocks only part of the sun, a partial solar eclipse occurs. This does not darken the sky as much as a total solar eclipse does.

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A total solar eclipse is a wonderful sight. Even ancient people were fascinated by it. However, it is not safe to view solar eclipse with your naked eyes whether they are partial or total. Why? Our eyes are sensitive to light. We blink when the light in our homes are too bright. The sun is about 150 million kilometers away from Earth, but its light is so bright it can reach us and enable us to see things around us. During solar eclipse, the moon slowly moves across the sun. if you look at the sun directly, its sudden bright light can damage your eyes. You may become blind forever.

Astronomers learn much about the sun, moon and earth by observing eclipses. They do this by using special filters. Special filters cut the solar light to a safe level. We, too, can observe a solar eclipse. One way is to place a basin with water on the ground. When we look at the water, we can see the image of the moon moving across the sun. Another way is to stand near a tree with plenty of leaves. Sunlight can pass through the spaces between leaves and cast images on the ground. Do not use sunglasses. They do not provide enough protection. To view a solar eclipse without protection, wait until the sun is completely hidden by the moon and only the corona is visible.

Why a solar eclipse occurs during a new moon? We recall that, as the moon revolves around Earth, we see different amounts of its lighted side. The amount of light that we see depends on the position of Earth and the moon in relation to the sun. Earth, moon and sun appear in a straight line during a new moon. At this time, the moon is between the sun and Earth. In this position, the moon blocks sunlight, the sun casts the moon’s shadow on Earth. But solar eclipse does not happen every month when there is a new moon. This is because the moon’s orbit is a little bit tilted to the earth’s orbit around the sun. As a result, the shadow of the moon falls into space and not on earth.

Lunar Eclipse

A lunar eclipse happens when the moon darkens as it passes through Earth’s shadow. A lunar eclipse may be total or partial. In a total lunar eclipse, the entire moon passes through Earth’s shadow. In a partial lunar eclipse, only part of the moon passes through Earth’s shadow. During a lunar eclipse, the moon becomes reddish because, as sunlight passes through Earth’s atmosphere, part of it is bent around Earth and toward the moon. The atmosphere scatters all the colors of light except red. A total lunar eclipse may last for more than one and a half hours. This is because the shadow of earth is much larger than the moon. Unlike a solar eclipse, a lunar eclipse can be seen in most areas on the side of earth where it is night.

Why a lunar eclipse occurs during a full moon? During a new moon, the moon is between the sun and the Earth. Thus, the Earth cannot cast its shadow on the moon. Recall that, during a full moon, the Earth is between the sun and the moon. In this position the Earth can block the light from the sun and cast its shadow on the moon. Therefore, a lunar eclipse can occur only during a full moon. However, an eclipse does not happen every month when there is a full moon. Why? As the moon revolves around the Earth, it may pass above or below the Earth’s shadow. In this way the earth’s shadow does not fall on it. Therefore, no eclipse happens.

Astronomers can predict accurately the occurrences of eclipse. Each year there are at least two solar eclipses and three lunar eclipses that may be seen from different places on Earth.