Some vise guy once stated that "a body in uniform motion stays in uniform motion, if no force is acting on it, a body at rest stays at rest if no force is acting on it." Sure, our universe works this way, I think we all agree on that... but why does it work like this? Does anyone know? As far as I know, not relativity nor quantum mechanics or string theory violate this principe (allthough I know little of relativity and extremely little of quantum mechanics and string theory). Is that correct? Cheers fellows.