Why do the planets rotate the sun? Wouldn't gravity just pull them in?

Question

Planets are know to move faster as they orbit the Sun, due to gravity, so why would the planets move away? Wouldn't the gravity of the Sun just pull them in and keep them there? I mean, magnets don't move away, they just stick together.

It may be an obvious answer, and a dumb question to ask, but I was just wondering. Answers are much appreciated. :)

Answer 1

When you orbit a stellar body, you "fall" around the object at such an angle that prevents collision.

Answer 2

Actually, something similar can be done with a magnet.  Just like with gravity, everything has to be balanced just right.  My video shows a small magnet levitating because it's repelled by another magnet.  

http://vids.myspace.com/index.cfm?fuseac...

To answer your question, you are right.  If the planet is too slow it will fall into the sun.  If it's too fast it will fly away.  Only if it's going the right speed will it stay in orbit.  

Answer 3

The planets do not ever pull crash into the sun because of a physical property called inertia. Sir Isaac Newton was the one who discovered this property. While doing research on gravity, he found that any moving object will keep on moving at a constant speed in a straight line unless something happens to make it speed up, slow down, or change its direction.

So, with that in mind, imagine that gravity does not exist. There is nothing to hold the planets in place, and because of inertia, they are just sailing through space at a constant speed in a straight line. Now throw a massive body, aka, the sun, into the equation, and give the sun the power of great gravitational pull. Suddenly there is something disturbing the planets' inertia. Instead of traveling at a constant speed in a straight line, the gravity of the sun is pulling on the planets, causing them to change direction. However, because the planets are still moving (because of inertia), they aren't pulled all the way into the sun. Instead, the gravity of the sun more or less bends the otherwise straight path they would be traveling in, and thus the planets orbit the sun in elliptical paths.

This answer is not very in-depth, but if you really wanna understand how this whole inertia/gravity thing works, there are plenty of good articles about it online! Hope this helps!

Answer 4

Yeah, cheeseca is right -- I'll just add that the speed of each planet balances the force of gravity just so. Newton (yeah, Newton again!) found out that the force of gravity between bodies gets stronger the closer they are together. So the closer planets go faster and that way they don't get pulled in. Out far from the sun, the outer planets feel much less force of gravity with the sun, and move more slowly.

The situation is very much like a weight on a sting being whirled around. The string pulls the weight toward you -- you can feel that force, and the faster you whirl the weight the stronger the force you feel on the string. There are really a balance of forces on the string - the force you are pulling the weight toward you with, and the inertia of the weight trying to go in a straight line. These forces balance, so the weight stays at a constant distance, and the effect of your pulling on the string is to change the direction of the weight's forward motion into a circle around you.