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Knot Physics

November 14, 2007

Physicists study how headphone cords tie themselves in knots.


Cutting through some knotty physics. I’m Bob Hirshon and this is Science Update.

It seems like headphone cords tie themselves in knots almost instantly, and now, physicists at the University of California at San Diego have proven it. Doug Smith and his student Dorian Raymer took strings of various lengths and tumbled them around in small boxes, nearly thirty-five-hundred times.

DOUG SMITH (University of California, San Diego):
For a reasonable length of string, like several feet, we found that you’d get knots typically within seconds.

In all, they identified 120 different knot types with up to 11 crossings. They also found that longer and more flexible strings were more likely to knot, and described how the knots form from random twists and braids. Knots can also form in electrical cables, umbilical cords, and even DNA — so this simple model could eventually help untangle some more complicated mysteries. I’m Bob Hirshon, for AAAS, the science society.