Why do some ponytails fan out unattractively while others form the perfect S-shaped swish?
It's all about the "Rapunzel Number", according to scientists at the University of Cambridge and the University of Warwick.
The physicists worked to devise a "ponytail shape equation" that was calculated by allowing for variables such as the curliness of hair, stiffness of each hair, ponytail length and the effects of gravity.
The unusual study doesn't just have implications for women's hairstyles – the work may have implications for materials such as fiberglass, wool and fur, as well as in the animation field, where depicting realistic hair has always been a challenge.
Unilever, which makes many haircare products, originally approached one of the physicists to collaborate on the study, in the hopes that it would reveal findings useful for making new haircare products.