A solar eclipse occurs when the Moon is between the Sun and Earth, so that the Moon’s shadow is cast upon a small spot on Earth. Different places on Earth can have partial solar eclipses when other places are experiencing total solar eclipses because the shadow of an eclipse has two parts. The two parts of the shadow are the umbra and the penumbra. The umbra is the center part of the shadow. The part of Earth that is in the umbra is having a total eclipse. The penumbra is the outer part of the shadow. The penumbra covers more land than the umbra. The part of Earth that is covered by the penumbra is having a partial eclipse.

Partial eclipses are more common than total eclipses. In fact, on average a total solar eclipse on any spot on Earth happens only one time every 350 years!

A solar eclipse can only occur during a new moon because this is the only time when the Moon is between the Sun and Earth.

The Sun looks like it is blocked during a solar eclipse because the moon is closer to the Earth than the Sun. Here’s an experiment that you can do to see this. Have a friend stand about 15 feet in front of you. Take your thumb and put it between your eye and your friend’s head. Now they have no head! Even though your thumb is much smaller than their head, it appears that your thumb is bigger because it is much closer to you than your friend’s head.

A solar eclipse works the same way. Even though the Sun is much, much bigger than the Moon, the Moon (like your thumb) blocks out the Sun (like your friend’s head).

Great Solar Eclipse Video

We found a great video that shows how the total solar eclipse on June 21, 2001 will affect Earth.  Click on the Sun to the right to open a new window where you can view the video.  When you're done, just close the window and you'll come right back here to learn lots more!

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Unless otherwise noted, all images courtesy of NASA. Permission for use at http://www.nasa.gov/gallery/photo/guideline.html.

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