There is this cone that rolls uphill by itself, by shifting its centre of gravity. http://plus.maths.org/issue40/features/uphill/index-gifd.html" [Broken] I wouldn't have looked up the mathematics of the issue if I hadn't seen it working with my own 2 eyes at a friend of mine's university physics museum. 2 questions: 1.) Thus "self-sustaining" system seems to break the laws of conservation of energy. How is this possible? The fact that the centre of gravity moves down the hill while the actual cone moves up doesn't seem to result in a conservative energy equation. Even thinking about imaginary forces such as centrifugal, coriolis etc does not help. 2.) I handled the double-cone and as far as I could tell its a legit piece of wood. So why hasn't anyone taken 1 000 000 of them and set them up with some dynamos in a smart way to make energy?