I know this must seem like a silly question for this forum but I'm actually serious. Why doesn't hair tangle?
Sure, hair does in fact tangle at times. (And dread locks are really tangles of hair.) But hair tangles much less often than I would expect it to.
Consider how easy it is to tangle an extension cord. Or consider how easy it is to tangle your headphones cord. Now compare that with hair:
- Your head has millions(?) of hairs, not just one to tangle with.
- The length-to-width ratio of hair makes it seem much more tangleable than the cord of a headphone.
- Hair is not terribly stiff, you can easily tie it in a knot. One strand of hair could probably hold thousands of knots.
- Hair, unlike extension cords or headphone cords, is covered with scales that seem like they would encourage tangling. (Actually the scales on wool play an important part in the process of felting!)
So given all of this, how is it possible that we are often able to keep such long hair without creating a tangled mess?
Best Answer
Hair is stiff.
Contrary to what the question states, a strand of hair is rather stiff. The average hair thickness is about 75$\,\mu$m, and you can hold horizontally by one end a strand about a thousand times this value in length (~5$\,$cm). See Shape of a Ponytail and the Statistical Physics of Hair Fiber Bundles. That means that an equally stiff earbud cord, which has a diameter of about 2$\,$mm at least, would be able to withstand its own weight in a horizontal position at a length of about one meter.
Also, as Geoffrey's answer points out, differently from earbuds, one end of the hair strand is fixed, attached to the head, which is an important constraint.