Elysa Kapelus, age 11, of Willowdale, Ont., Canada, for her question:
WHAT KEEPS THE STARS FROM FALLING?
Sometimes a bright spark arches across the night sky ¬and disappears before it reaches the ground. People call it a shooting star. However, up to date young Space Agers know that it is a tiny meteor that burns up in the atmosphere. A real star is a whopper at least a million times bigger than the planet earth.
The stars in our sky are strewn helter skelter through the galaxy, and the whole thing is almost too big for our minds to grasp. Yet this vast expanse of star studded space is organized and operated in a very orderly fashion. Though all the stars are in fast motion, the chances of collisions are almost impossible.
This celestial traffic system is possible because the universe is made from matter, including the stars, and stupendous cosmic energies that span the vast reaches of space. For example, every speck of matter has its own built in quota of gravity. And gravity is the major cosmic force that keeps the stars in their places.
Gravity reaches out from every star and from every speck of dust in every cosmic cloud. It attracts, or pulls, matter to matter. This, one might suppose, would pull all the material in the galaxy together in one big ball. However, this is counteracted by another cosmic force that works to keep the stars apart.
No doubt you have wondered why the mighty gravity of the massive sun does not pull all the planets down into its fiery furnace. This does not happen because the planets are in orbit, constantly swinging around and around the sun. The speed of this orbital motion works to counteract the sun's pulling gravity, somewhat like a tug of war.
The orbital speed of each planet is just right to balance the sun's pull of gravity. This keeps it in its own traffic lane in the orderly solar system. On a grander scale, loo billion stars swing around and around the stupendous galaxy. The gravity that would drag them all toward the crowded center is counteracted by their orbital speeds. They cannot fall out of their proper places.Everything in our wheeling galaxy is governed by this celestial tug of war. Gravity pulls the stars together; orbital speed keeps them apart. They cannot fall out of their separate orbits because balanced cosmic forces keep them in their proper traffic lanes.