Zero Angular Momentum: The Falling Cat and the Geometry of Shape Space
A cat dropped upside-down rotates 180° and lands on its feet, despite having zero angular momentum throughout. This is not a trick and not a violation of physics. The explanation took physicists from 1894 to 1993 to fully work out, and the answer — a geometric phase arising from the holonomy of a fiber bundle — is the same mathematics that governs the Berry phase in quantum mechanics and the Aharonov-Bohm effect in electrodynamics. We adopted two strays this year. They fall beautifully.