The Curious Case of the Hopping Hoop

Take a rigid hoop and attach a weight to it at some point on the circumference. Start it rolling. Will the hoop hop off the surface at some point in its rotation? This simple question and physical model has been a matter of controversy ever since it was posed in John Littlewood’s 1953 book, A Mathematician’s Miscellany. Since then, numerous publications have examined the puzzle, some concluding it hops, others that it doesn’t, and presenting a variety of mathematical models to explain why it does, or doesn’t, or does under certain conditions and doesn’t under others.

What is really going on?