How is a curling hair like a long-range oil pipeline? And what two groups are working on the physics that apply to both? Learn about the science of engineering mop-tops.

Over at Physics Central's podcast, there's a fascinating discussion with an MIT grad student, Jay Miller, who looks at the curve of the flagella on an amoeba, the spiral of a double helix, and the buckling of an oil pipeline. Through a group of acquaintances, he found out that the movie-makers at Pixar were doing the same. They were trying to figure out the exact motion of the curly hair that the heroine in Brave flips around the screen. Each separate group was studying the same curling motion.

As Miller says on the podcast, "Hair actually is the easiest example of a whole class of problems."

So what do a human hair, a steel pipeline and an amoeba's flagella have in common? Once they all assume the right proportions, they all work the same. A miles-long pipeline, though it can be massively thick when looked at up close, looks like a long, spindly hair when it's spread across the landscape. When a hair is short enough (like a military buzz cut) it's sticking out from the head directly as it grows. It's short enough that its internal strength can stand up to the force of gravity. As it grows, however, it has to 'carry' a longer length, and gravity pulls it down.

Even those of us who aren't at MIT â€” or working for Pixar â€” can see the interplay of gravity, exerting a force in in one direction, and the structure of the actual 'hair' curling in on itself. Grow a hair long enough, and its own weight will pull it straight. However, as you get to the very tips of the hair, which don't have as much weight on them, the curl will come back. The more towards the end you get, the less weight is on it, and the more extreme the curl.