British scientists have created an equation that can predict the shape of any ponytail using the Rapunzel Number, a ratio that accounts for the effects of gravity on hair relative to its length. Seems unimportant, but these new statistics, which solve an issue that has puzzled mathematicians since Leonardo da Vinci about 500 years ago, should help the computer graphics and animation industries represent hair better. Someday we may not need real people in film. Learn more in the Rapunzel number helps scientists quantify ponytails story at Reuters.