Let's say I have permanent magnets set up in a sort of half sphere with the inside of the sphere pointing up and it laying flat on a table and then I have a ball with, let's say, half the radius of the half sphere. The ball has the same permanent charge as the half sphere. I place the ball over the half sphere. The ball and half sphere would repel each other and the ball would remain still and afloat. If I sent the ball on a spin, wouldn't it continue to spin assuming it is in a vacuum? I've always heard that perpetual motion is impossible on Earth, so what's wrong with this scenario? Would it even work? Would the ball's rotation slow down? I originally posted this on Yahoo Answers, but I was suggested to post it on a science forum. Here's the original: http://answers.yahoo.com/question/i...tY.c6Mrty6IX;_ylv=3?qid=20110618150331AAp86o2 I did get quite a few good answers, but I expect there are real experts here on Physics Forums.