For all these years, we just took it as a thing that happens – a shoelace becomes untied. But no longer do we have to let this happen. In the future, our children’s children will get an odd look on their face when they read an old book or watch an old shoe where a shoelace becomes untied and a person trips.
Oliver O’Reilly was teaching his daughter to tie her shoes when he realized something: he had no idea why shoelaces suddenly come undone. When he went looking for an answer, it was apparent that no one else knew either.
So O’Reilly, a mechanical engineer at the University of California, Berkeley, roped in two of his colleagues to help work it out. In a paper published on April 11 in Proceedings of the Royal Society A, they show that a combination of forces act on shoelace knots to cause a sudden, runaway failure.