Karen Sutherland, age 11, of Winnipeg, Manitoba, Canada, for her question:

What causes an eclipse?

There are solar eclipses and lunar eclipses. The moon causes them both, but it could not perform this magic without help from the earth and the sun. When the orbiting moon passes directly between us and the sun, we get a solar eclipse. The sun happens to be 400 times wider than the moon and 400 times farther away. So from our point of view, during a total solar eclipse the dark moon is just big enough to blot out the radiant face of the sun along a thin curving line across the face of the earth. This happens very rarely because the orbiting moon usually passes above or below the sun.

A solar eclipse is done with solid objects. A lunar eclipse is done with shadows. The beaming sun causes our planet to cast a long tapering shadow, far out into space from the night side of the globe. The lunar orbit is rather wobbly and usually the moon does not pass through our shadow. But sometimes it does. As the earth's long shadow creeps across the face of the full moon, we see a lunar eclipse.