Spin a coin on a tabletop. As it loses energy and tips toward the surface, the coin begins to
roll on its rim, wobbling faster and faster and faster. Toward the end, the coin generates a
characteristic rattling sound of rapidly increasing frequency until it suddenly stops with a distinctive
shudder.
Mathematician H. Keith Moffatt of the Isaac Newton Institute for Mathematical Sciences in
Cambridge, England, now offers an explanation of why this motion ends so abruptly instead of