Dzhanibekov effect demonstration in microgravity, NASA.(Tennis racket theorem)

Principal axes of a tennis racket. The tennis racket theorem or intermediate axis theorem is a result in classical mechanics describing the movement of a rigid body with three distinct principal moments of inertia. It is also dubbed the Dzhanibekov effect, after Russian cosmonaut Vladimir Dzhanibekov who rediscovered one of the theorem's consequences while in space in 1985