Laraine Mcmahon, Age 11, Of St. Catharines, Ont., Canada, for her question;

Can we prove what is really dawn inside the earth?

No, we cannot say for certain what fills up the center of our round globe. We can only make some educated guesses on the basis of the very scanty evidence we have. We can estimate the weight of the surface crust and the weight of the planet as a whole. But the entire earth is much heayier than it would be if it were made altogether from rocks like those on the surface.

The deeper layers, then, are denser and heavier. Earthquake vibrations give u8 another clue about the earth's iaterior. Vibrations travel at different rates through materials of different densities. And the records indicate that the layers get heavier the deeper we go and that the earth's core may  just may  be made of the heavy metals, nickel and iron.