Steve Jordan, Age 12, Of Burlington, N.C., for his question:

How was the earth's moon formed?

We cannot say for sure how our own earth was formed, though we can dig down into its mineral. Crust and figure out a lot of its later history. So far, we have not set foot on the moon to examine its features at first hand. So we can only guess how it was formed and wait for more information to prove our guesses right or wrong.

A theory is an educated guess. Scientists cannot prove how our golden moon was formed, but they have suggested some theories about its origin. A theory, of course, must take into account all the facts we know for sure. If new facts are discovered which contradict the theory, then the theory is proved wrong.

At one time, many experts thought that the moon might have been a piece of matter torn from the earth. It is just about the right size to have come from the great hole in the earth's surface, which is the bed of the pacific ocean. The weight of the moon also fits in with this theory, for it is made of materials of the same density as those which form the earth's crust.

A new theory suggests that the earth and its satellite were born at the same time. Billions of years ago they were part of a vast mass of unformed fluid material. For some reason, perhaps because of its rotation, a large chunk of the material pulled away from a smaller chunk. The large chunk contained 80 times more material than the smaller chunk. It cooled to form our solid earth, and the smaller fragment became the moon.

This theory suggests that the moon cooled first on account of its smaller size. As gases arose from its steaming surface, they were lost, or so this theory suggests. In any case, the gravity of the moon is not strong enough to hold a blanket of atmosphere. This fact may explain the rugged lunar landscape.

Later, volcanic material may have erupted and welled up from the hotter interior of the cooling satellite. The crustal minerals bent to form mountains. But with no atmosphere, there was no xeather, no wind and water to wear down the original peaks. This theory could explain the known facts, but we still cannot say for sure how the moon was formed.

Nor do we know when the earth and the moon were born. We know from the ages of certain minerals in the earth's crust that our world has had at least four billion birthdays. The birth of the moon and the earth, then, must have occurred at least four billion years ago. We do not know enough to be sure when this happened or how it happened.