Tom Taggart, age 16, of Shreveport, Louisiana, for his question:

Why are heavenly bodies generally sphere shared?

When an event is repeated again and again, we can expect to find a reasonable cause for it. Hence it seems logical to expect a reasonable explanation for the fact that all the sizable heavenly bodies tend to be roughly spherical in shape. To find the molding agent, we need look no farther than the built in force of gravity. Gravity tends to exert itself as though its pulling power were in the exact center of a massive object. The earth's center of gravity is in the middle of our sphere shaped globe. From this point gravity exerts its pulling attraction outward in all directions. The particles of matter on every side are pulled toward the center. This event occurs in the stars, the planets and their moons.

Gravity has tended to mold the celestial materials into sphere shapes. This molding process began when the heavenly bodies first began to form from particles of cosmic gases. The gravity operating in the embryo earth pulled its heaviest elements down toward its central core. Less force was exerted on the lighter elements and they were molded into spherical onion skins around the dense, heavy core.