NASA - National Aeronautics and Space Administration

An eclipse is the darkening of a planet, moon, or star. This darkening is caused in one of two ways. It can be caused when the shadow of one planet or moon falls on another planet or moon. Or, it can be caused when one planet or moon moves in front of another to block its light. The light of the sun causes both Earth and the moon to throw shadows into space. This causes two kinds of eclipses, a lunar eclipse and a solar eclipse.

A lunar eclipse takes place when the moon gets dark as it passes through Earth's shadow. The moon does not become completely dark during most lunar eclipses. In many cases, it becomes reddish.

A solar eclipse takes place when the moon blocks the light of the sun. This makes the shadow of the moon pass across Earth. The moon may darken all or part of the sun.

Image to right: A solar eclipse occurs when the moon passes between the sun and Earth. This may darken all or part of the sun. Credit: World Book illustration

A person should never watch a solar eclipse with unprotected eyes. The light from the sun is very strong and will hurt the eyes. Only glasses with special filters are safe. Sunglasses do not provide enough protection.

One safe way to watch an eclipse is through a pinhole projector. This projector is made with two pieces of cardboard. One piece has a small hole punched through it. The piece with the hole is held above the second piece. Sunlight passes through the hole and casts an image of the eclipse onto the second piece. Instead of looking at the sun, you look at the shadow on the cardboard.

How to cite this article: To cite this article, World Book recommends the following format: "Eclipse." The World Book Student Discovery Encyclopedia. Chicago: World Book, Inc., 2005.

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