Terry Erickson, age 11, of Duluth, Minnesota, for his question:
Why is there no gravity on the moon?
Naturally we are agog for newsy items about our space program as it gets into high gear. However, some of the reports are not as clear as they should be. Many of Andy's pen pals, through no fault of their own, have received the impression that the moon is gravityless and that inside a space capsule the laws of gravitation do not exist.
Our bodies and minds are accustomed to the earth's gravity. Its exertion hugs up to the. planet's surface, allows us to leap so high and so higher and never misses a chance to catch us off balance and bring ns tumbling down. Lately we have been viewing some simulated human activities on the surface of the moon. It we observe only these visual demonstrations, we may get the impression that gravity does not exert its mighty force on the lunar landscape. However, as a rule, the demonstrator adds a few words to go with the pictures. He states that the moon does indeed have gravity though it has only pne sixth the force of gravity on the earth.
This explains those lighthearted antics on the lunar landscape. On earth, our muscles have trained themselves to cope with six times more gravity. On the moon, a person has all that extra power. Suppose an earthling can spring four feet above the earth. His muscles are equipped to spring 24 feet above the lunar landscape. Suppose he can hike on earth with a 100 pound pack on his back. On the moon he can carry 600 pounds with the sane ease.
On the moon he can walk farther and faster with longer strides. The force of gravity also exerts itself on falling bodies. On earth it is strong enough to plumet you down at breakneck speed. The moon's lesser gravity would cause. a slower fall. A spaceman plunging accidentally down one of those steep cliffs around a lunar crater might have time to grab onto a rocky ledge to break his fall. Siotlstod movies of these goings on give the impression that the lunar landscape is a carefree place where earthlings can forget the force of gravity entirely.
Actually, the ever present force of gravitation is merely reduces to a sixth of its earthly power. But it is there, operating under exactly the sane laws as it does on earth. Every heavenly body in the entire universe has a quota of built in gravity. Its quota depends upon its mass, the amount of matter packed into its size. The moon is less massive than the earth, it is smaller and made of lighter materials. But since it is made of particles of matter, it must possess its quota of gravity. In fact, a speck of dust or any other tiny fragment of matter in the universe has the correct portion of gravitational force. The quota, in this case, is infinitesimal. But our mighty sun exerts enough gravitational force to keep all the far flung planets in their places merely because of its massive size and density.
Gravity, of course, gives weight to objects on the surface of a heavenly body. A 120 pound earth boy would weigh only 20 pounds on the moon. Our space capsule pictures show astronauts in a weightless condition and we assume that gravity disappears entirely out in space. But this apparent phenomenon is not quite so either. However, this weightlessness is a tricky topic and we have used all our space for today. Actually, it is another question and if you are interested we can tackle it in another column.