BERKELEY, Calif. (CBS) – The problem is as mystifying as it is frustrating: No matter how many times or how tightly you tie your shoelaces, they keep coming undone.
Well now science may be able to explain what keeps going wrong down by your feet. New research from the University of California-Berkeley finds that it all comes down to “knot mechanics.”
“A double whammy of stomping and whipping forces acts like an invisible hand, loosening the knot and then tugging on the free ends of your laces until the whole thing unravels,” researchers said in a statement.
To see that unraveling up close, the team pointed a camera at the sneakers of the study co-author running on a treadmill. Then they watched slow motion footage that shows exactly how the shoelace comes undone.
“When running, your foot strikes the ground at seven times the force of gravity. The knot stretches and then relaxes in response to that force,” they said. “As the knot loosens, the swinging leg applies an inertial force on the free ends of the laces, which rapidly leads to a failure of the knot in as few as two strides after inertia acts on the laces.”
The study also answered another vexing question about shoelaces – why they sometimes stay tied perfectly for a long time before suddenly coming undone.
“It’s not until you get one little bit of motion to cause loosening that starts this avalanche effect leading to knot failure,” Study co-author Christine Gregg said.
Why spend time studying shoelaces at all? It may one day help scientists learn more about other knotted structures, like DNA.