It is a common complaint and an often head-scratching mystery: “How the heck did these cords get so tangled together?” In 2007, student Dorian Raymer and physics professor Doug Smith at the University of California at San Diego conducted an experiment to solve the mystery of “”Spontaneous Knotting of an Agitated String“. Using a computer program and motorized boxes, strings of varying lengths were tumbled inside and it was found that complex knots often form within seconds. They repeated the test 3000 more times, using strings of different lengths and stiffness, and boxes of varying sizes, to determine whether there were any rules that could be applied to the knotting of a string. Overall, 120 different types of knots were counted.
The result: the longer the string, the more likely it is to form a knot. String that was 1.5 feet or shorter never became knotted. But “as the string gets longer, the probability of a knot forming goes up and up,” Smith says, at least to 18 feet. Flexibility was also a factor. The more flexible the string, the greater chance it will become knotted.
“The way that you get a knot is the string has to bend back on itself, coil back on itself. As a string or cord tumbles, the end of it has a 50 percent chance of weaving to the left or the right of the coils, and under or over the coils, sort of like random braiding.” Smith said.
Download the full study report from PNAS.