it is a longer article ... and I just know you're anxious to read the actual whyFor more than 40 years, Oliver O'Reilly's shoelaces have been coming untied pretty much every day. And for most of those 40 years O'Reilly didn't think too much about it.
But then, about a decade ago, his daughter Anna was learning to tie her shoes, and O'Reilly decided his shoelace problem wasn't worth passing on to another generation.
"I didn't want her to inherit my problems, so I went online and found some really helpful videos to teach me how to tie her shoelaces," he says.
And, perhaps if O'Reilly had had a different job, that's where the shoelace problem would have stopped. But Oliver O'Reilly is a professor of mechanical engineering at the University of California, Berkeley, and as he looked at videos of shoelace knots, he started wondering why they came untied in day-to-day life.
"That problem always stuck in my mind," he says.
Now, he and two graduate students have published a paper, in Proceedings Of The Royal Society A, titled "The roles of impact and inertia in the failure of a shoelace knot."
In order to study how shoelaces untie themselves, the team did a handful of experiments. "We did all sorts of stuff," says graduate student and co-author Christine Gregg. "We ran on treadmills. We swung our legs back and forth while sitting on tables, to take the impact out of the equation. We just stomped our feet like Frankenstein."
In all, they estimate it was well over 100 hours of testing, over about two years.
well, aren't you?
I mean, anticipation and all that ... probably as your own shoe comes untied ...
oh ... well, here it is :
Based on the video, and the other tests they did on shoelace knots, the team says two things happen when a lace comes untied. First, the impact of the shoe on the ground loosens the knot. With the knot loosened, the whipping of the free ends of the laces — as the leg swings back and forth — makes the laces slip.
As the foot hits the ground and the laces swing repeatedly, the knot loses integrity until, in a matter of seconds, it fails altogether.
the mystery is solved!