Centripetal Spheres: a fun DIY physics toy- two metal spheres connected by a rubber band orbit each other as energy oscillates between elastic potential energy and rotation kinetic energy. Just wind up the rubber band and let go. When the rubber band has unwound the rotational inertia of the bearings winds it back up until it changes direction. The process repeats until the initial energy is dissipated through friction. ➡️ Follow the link in my profile for info on where to get parts for this dev