Our side has ridges or hills, and craters, some of them deep. But it is not nearly so “bumpy” as the dark side. Researchers think this is because the little moon crashed, fell apart, and landed on the other side. They say the dark side has a thick upper layer of soil. It also has much higher mountains than on the side we see. Some of them are three thousand meters high. And when the little moon hit the big moon, it caused a bulge. The other side of the moon sticks out into space more. Think of a children’s ball that has been hit or kicked too much. That ball, and our moon, are no longer round. They are lop-sided. Pictures of the dark side clearly show this.

CHRISTOPHER CRUISE: You may be wondering how our moon got there in the first place. Scientists think it also resulted from a crash. Billions of years ago, they say, something very large hit the earth. It may have been as big as the planet Mars. When that happened, part of the earth was thrown out into space. Over time, these pieces of earth-rock and dust came together, and formed not one, but two moons.

The American space agency plans to explore the moon further within the next year. That may help to prove the two-moon crash idea, or maybe offer something completely new. But if the latest research is correct, what is now one, was once two!

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JIM TEDDER: Imagine a summer night in America. A father and mother are watching television or reading the newspaper. Their children are outside the house, playing and waiting for a special time. Then, just as it starts to get very dark, the magic begins.