It's of interest to anyone who wears shoes with laces.
You've been there. You've done this countless times -- sat down and retied a shoe on which, for reasons unknown, a lace has come loose.
For Dr. Oliver O'Reilly at UC Berkeley, there came that time when enough was enough. Applicable to anyone on the planet who wears shoes -- why must their laces come untied?
Call it the nuisance that led to curiosity and finally intense investigation by O'Reilly and mechanical engineering graduate students Christine Gregg and Christopher Daily-Diamond.
If the question sounds simple, consider the factors: walking strides, shoelace material, bending stiffness, torsional stiffness, how fast you're walking, what your shoe is made out of, etc.
The team spent more than two years studying this "dynamic untying" as they called it, testing different varieties of the typical bow knot in both the weak and strong versions.
Gregg walked and ran countless miles on Berkeley streets, then even more on a treadmill. With a slow-motion camera, they captured and duplicated the motion and forces that slowly break and pull even the strongest knots to failure.
So no, this is not a matter of human error. It's physics, with possible future applications that might even help us understand DNA.
You might be wondering how many millions of dollars this cost California taxpayers. Well, the researchers are already paid and they borrowed all of their equipment. Essentially, they did it on a shoestring.