Is there an equation for a ponytail?
Shape of a ponytail and the statistical physics of hair fiber bundles
Physicists wrote an equation for the shape of a ponytail.
Ig Nobel 2012
A ponytail is thousands of springy, curly fibres, all pushing against each other while gravity pulls them down. The team turned that into a “ponytail shape equation”.
A key number in it is called the Rapunzel number. Yes, really. It is useful for anything made of bundles of fibres, from wool to fur.
There is now a Rapunzel number. Use it wisely.