The hair on people’s heads (typically 100,000-150,000 hairs per head) comes in lots of shades, degrees of oiliness, and amounts of curliness. Jean-Baptiste Masson, who works at the Laboratory for Optics and Biosciences of the Ecole Polytechnique in France set out to study the problem scientifically. On the experimental front, he consulted hairdressers and got them to count tangles in people’s hair. On the theoretical front, he devised a geometrical model of hair, hoping to explain the results mathematically.
Tangles, defined as groupings of hair that resist combing, proved to be almost twice as prevalent with straight hair than with curly hair. Masson (firstname.lastname@example.org) explains this by saying that although straight hairs interact with each other less frequently the interaction is at great angles, and it is the relative angle between hairs that causes tangles. This in turn is a consequence of the surface properties of the hairs. One possible application of this work on hair, Masson says, is in designing velcro-like products.
For instance, the velcro properties could be changed by adding extra scales to the soft part of the velcro elements or by making the tension of the strings higher-the equivalent of making the strands straighter. Masson, whose main field of research is biophysics, expects his geometrical modeling might also be useful in the study of polymers and other filamentary materials in the biological world. (American Journal of Physics, August 2007)