Use this very simple construction to demonstrate the principle of Conservation of Angular Momentum. The Geomag Manual describes this as "DANCING BALLERINA EFFECT”: the principle of energy conservation"; the original demonstrations described here follow those in the Geomag Manual. But when you construct them, be sure to use Peter Jepsen's better modification version below, for best effect and more fun! My friends ask me what's so cool about Geomags, and I've showed them several things. Amazingly, this one is the one that gets the biggest "Oooooooooooh!"!