Scientists have just uncovered the truth to a befuddling mystery, a truth that was right under our noses the whole time, literally. They’ve figured out why your shoe laces come undone so quickly after you tie them up tight.

And it’s a rather amazing conclusion: they discovered that the force of a foot striking the ground stretches and then relaxes the knot you just tied, and the second force of your leg moving forward acts on the lace’s ends, almost like an invisible hand pulling them apart. And it could have some big applications for other structures like DNA.

Researchers at the University of California at Berkeley made the discovery by using slow motion camera and a series of experiments. They found that shoe lace knot failure happens in seconds, and is due to complex forces.

“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,” said Christopher Daily-Diamond, study co-author and a graduate student at Berkeley. “This is the first step toward understanding why certain knots are better than others, which no one has really done.”

“We are trying to understand knots from a mechanics perspective, such as why you can take two strands and connect them in a certain way that can be very strong, but another way of connecting them is very weak,” said Oliver O’Reilly, a Berkeley professor of mechanical engineering, whose lab conducted the research. “We were able to show that the weak knot will always fail and the strong knot will fail at a certain time scale, but we still do not understand why there’s a fundamental mechanical difference between those two knots.”