It’s a problem no one has dared to study before: why, exactly, do shoelaces come untied?
Three mechanical engineers at UC Berkeley ― Christine Gregg, Oliver O’Reilly, and Christopher Daily-Diamond ― have been busy figuring out the answer to one of life’s simplest (and most annoying) problems. According to their study, which was recently published in Proceedings of the Royal Society A, it all depends on two main factors: stomping and whipping forces.
In order to arrive at these findings, the Cal Berkeley engineers videotaped Gregg while she ran on a treadmill. It was filmed in slow-motion so researchers could figure out what causes “shoelace knot failure.”
"First, the repeated impact of the shoe on the floor during walking serves to loosen the knot,” the study says. “Then, the whipping motions of the free ends of the laces caused by the leg swing produce slipping of the laces. This leads to eventual runaway untangling of the knot.”
Stomping or whipping forces by themselves are not enough to untie the shoe, as both forces must take effect.
In the study, the researchers also looked at the two most common ways people tie their shoes. The pictures from the study below illustrate both the strong and weak versions of the knots:
“Some laces might be better than others for tying knots, but the fundamental mechanics causing them to fail is the same, we believe,” Gregg said in an interview with Berkeley’s website.
And while the study about shoelaces sounds pretty simple, it could have major implications for DNA research.
“When you talk about knotted structures, if you can start to understand the shoelace, then you can apply it to other things, like DNA or microstructures, that fail under dynamic forces,” Daily-Diamond told Berkeley’s website. “This is the first step toward understanding why certain knots are better than others, which no one has really done.”
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