# Thread: Thought experiment on gravity and EM

1. ## Thought experiment on gravity and EM

I wonder if somebody would give me help with a problem I've been thinking about. Just as a thought experiment, one could imagine this. Suppose there was a world of 2D beings living on the inside of a rotating cylinder, with the cyclinder being made out of some rubbery substance. I think they could experience something like gravity, because massive objects would, due to centripetal force, make "dents" in the cylinder, and other nearby objects would be attracted to one another.

Now I've been thinking about this. Is there any way that one could create a mechanical system that would replicate the way EM works, i.e. with like poles repulsing one another and unlike poles attracting one another? I'm trying to think of this specifically with some form of rotation, but if there are other models, I'd be happy to hear.

2. would two dimensional objects have mass in a three dimension world?

For example:

Mass=density*volume

a truly two dimensional object has no volume.

3. That's a good point. I guess it would have to be three-dimensional marbles living on the surface of a rotating rubber cyclinder or something like that.

4. It sounds like you are talking about the three fundamentally different ways that gravity, electric force, and magnetism work. With gravity, all objects experience the same acceleration, so that's why "ficticious forces" (say, from rotation) are a good way to emulate gravity. Electric forces come in two flavors, attraction and repulsion, so changing the sign of the charge changes the sign of the acceleration. Magnets are even more complicated, because they have poles where you can change the sign of the net acceleration by reversing the direction of the magnet. I don't think you'll ever get either of those latter effects with ficticious forces like rotation. It would violate the "equivalence principle".

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