# Q & A: Solar System in a Jar

Q:
Therorticaly when looking at gravity we know space is a vacume so would it be posible to create a small scale modle of our solour system with in a vacume chamber?
- Chris
A:
It's a great idea! But...

The thing is that gravity doesn't need air. So if you had a model of the solar system in a vaccuum jar, all the planets in it would fall towards the ground.

Now, let's assume that we found a way to keep the Earth's pull out of it. Still, gravity is a VERY weak force. If you think of it, it take the entire Earth (and the Earth is pretty darn big) just to create the little force that you feel as weight. A 1 pound ball would still only have a tiny fraction of the Earth's pull. (about one billionth of one billionth of one millionth) So not much would happen with such weak forces.

Now, that being said, it would not be inconceivable to use other forces than gravity for your model. The electric force is similar to that of gravity, only it's much stronger. Or perhaps you can think of some other way to make a good model.

I like your thought, but we'll need some force other than gravity to make it work. Keep the ideas coming!

math dan

P.s. If you made a little scale model using balls about the same density as the Earth and Sun, and managed to put it on a satellite (or anything in pure free-fall) to keep the Earth's gravity from making trouble, it would of course still orbit due to the gravity of the balls. The question is, how quickly would it make one orbit, since, as Dan points out, the force isn't very strong. The answer turns out to be that for a real scale model, it would still take one year to make the orbit! That would be a little slow for viewing, but still should work in principle. Mike W.

(published on 10/22/2007)