Steven J. Riegel, age 12, of Madison, Wisc., for his question:

Why is there no air on the moon?

Speed and gravity engage in an endless tug of war. If an object travels at a speed Of Seven miles a second, it can escape the Pull Of earth's gravity and leave Our planet. The earth's velocity of escape is just under seven miles a second. On the moon, where gravity is much less, the velocity of escape is one and one half miles a second.

Air molecules travel fast and the warmer they are the faster they travel. On the moon, gases could reach the velocity of escape. If the moon ever had air, it most likely escaped long ago. And' if more gases formed, they would also speed up and escape the lariat gravity.