John Rasmussen, age 12, Salt Lake City, Utah,

What exactly is a lunar eclipse?

You and I and everyone else has a shadow, So does a tree, a house, a mountain and any other solid object. Even a cloud has a shadow. Then we should not be surprised to learn that the earth has a shadow. It is a long, tapering shadow reaching 850,000 miles out into space. Like all shadows it always points away from the sun.

The distance of the moon from the earth varies between 222,000 and 253,000 miles. It circles the earth once in about 27 days. You would expect it to pass through earth's long shadow on every trip. This does not happen, If it did, we might get a lunar eclipse every month.

For a lunar eclipse happens when the shadow of the earth falls across the face of the full moon. It can been seen only on a few nights when the sun, earth and moon are arranged in a straight line, At the point of eclipse, the earth's shadow may be three times the diameter of the moon. The moon travels a distance of its own diameter in about an hour, So a Iota¬lunar eclipse may last two hours, the complete show almost four hours,

It begins as the earth's shadow takes a bite out of the full golden moon. The edge of the shadow is curved, which is one proof that our earth is round.  It casts a round shadow. The shadow may take a full hour to creep across and eclipse the whole moon. Even then the moon is not hidden. Its golden face dims in a dull, copper red blush.

This is because of the earths deep, gauzy atmosphere. Sunshine comes through it like a halo and scatters light into the shadow. Some of it falls on the face of the moon. Gradually the moon wends its way out of the shade into the full sunlight. Its golden face shows bit by bit as the eclipse wanes.

The moons s orbit is not at right angles to the orbit of the earth. It slopes about 5 degrees. Hence, the moon usually passes to the north or soutt of the earth's shadow. That is why we don't get a lunar eclipse every month.

As things are, a lunar eclipse is more rare than a solar eclipse, However, it lasts longer and can be seen over a wider area, There may be two a years none or only one; Once in a great while there are three. Not all of them are total lunar eclipses.