Todd Elson, age 12, of Enid, Oklahoma, for his question:
What holds a satellite up?
Right now, several man made satellites are orbiting the planet Mars. Others have been orbiting the earth for years with no engines of any sort to push them around on their endless journeys. These man made satellites are held up by the same forces that govern the orbiting moon. The same forces also keep the planets from falling into the sun and govern the wheeling stars of the Galaxy.
In the 1600s, a student named Isaac Newton figured out the mysterious laws of gravity. Me took the trouble to express them in simple terms, hoping to make ft easy for everybody to understand them. But the mysterious, invisible farce is very complex and even scientists keep discovering new things about it. Recently they edified their ideas about why a satellite stays up when gravity keeps pulling it down. However, these ideas did not modify Newton's old laws.
We know that every particle of matter has a minuscule quote of gravity. Massive bodies, such as stars and planets, are dense packages of particles. Their gravitational force increases according to a strict ratio of mass and volume. The invisible force is a pulling pier, exerted from the mass. It reaches out, getting weaker at a fixed ratio as it extends out.
Certainly the earth's gravity is strong enough to pull down the man made satellites, now orbiting around it. Some of the meteors it pulls down are bigger and mole massive than they are. But meteors are not protected by the certain something that holds up the satellites and keeps the planets from falling into the sun.
This something is a circling motion, delicately balanced at the right speed and distance. This used to be called centrifugal force, though the circling motion does not exert a force. It merely counteracts the pull of gravity. Gravity pulls down meteors because they are not in orbit. But if they swerve in along a curved, partial circle, their falling speed is delayed.
If there were no gravity, a moving object would continue on at the same speed along the same path forever. A satellite is launched to offset the earth's gravity so that it can continue on and on under its own power. But to keep it above the earth, space scientists must compute the delicate balance between its orbit and the earth's gravity. These precise ratios include its mass and distance, its speed and orbit.
When a satellite is launched precisely into orbit, it counteracts the pull of gravity and stays above the earth with no engine to keep it going. But if it veers closer or loses speed, gravity gets the upper hand. The satellite winds closer and closer around the earth and finally returns home.