Gilbert Yette, age 13, of Mohawk, New York, for his question:

 How do planets get centrifugal force?

The sums gravity pulls at the planets. If it could, it would drag them right into the blazing furnace. But it cannot do this because the planets have centrifugal force. And this force counteracts the gravitational pull of the sun by pulling away from it.

Tie a ball on a string and you can feel the pull of centrifugal force for yourself. Get in an open space where you are not likely to do any damage and set the ball whirling about your head. Hold tight to one end of the string and you will feel the pull of the whirling ball. It is pulling with centrifugal force and, if the string broke, the ball would fly away from you.

An object gets centrifugal force when it whirls around a central point. This force pulls it away from the center. And all the planets are whirling at high speed around the sun. Each planet gets its centrifugal force from the speed of its orbit. These speeds are fixed and the suns gravity is fixed. Hence the earth and the other planets come out of their orbits in the Solar System.