In more bizarre scientific research, physicists have come up with an equation that explains and predicts the shape of a ponytail.

Professor Raymond Goldstein worked on the equation with Professor Robin Ball from the University of Warwick and Patrick Warren, from Unilever’s Research and Development Centre. According to them, this equation aims to “solve a problem that has puzzled scientists and artists ever since Leonardo da Vinci remarked on the fluid-like streamlines of hair in his notebooks 500 years ago”.

The abstract of the paper, which will appear in Physical Review Letters Journal, follows:

A general continuum theory for the distribution of hairs in a bundle is developed, treating individual fibers as elastic filaments with random intrinsic curvatures. Applying this formalism to the iconic problem of the ponytail, the combined effects of bending elasticity, gravity, and orientational disorder are recast as a differential equation for the envelope of the bundle, in which the compressibility enters through an “equation of state.” From this, we identify the balance of forces in various regions of the ponytail, extract a remarkably simple equation of state from laboratory measurements of human ponytails, and relate the pressure to the measured random curvatures of individual hairs.

The best part? The scientists have come up with a new mathematical quantity known as the Rapunzel Number. Very clever.

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(via BBC News)