I'm just curious, why is it that anye perpetual motion machine that is thought up is discarded immedietly. I know that energy can't be created nor can be destroyed but then again, a few centuries we were absolutely positively sure that the Earth was flat! I mean anything can be wrong, why newton's law's itself was proved wrong and we still learn them in school! How can we be so sure that it can't possibly work!!! Can someone clear this out for me?