How does it twirl? Why does it loop? An American cowboy might take it all for granted. But a French team has explored how the laws of physics can explain this common thread.
PARIS — Cowboys are alive and well, and not only in the United States. You can find three of them twirling their lassos in the middle of a Parisian physics laboratory.
Basile Audoly, Pierre-Thomas Brun and Neil Ribe, all French scientists, made the trip to Denver, Colorado in March to present their theory of “lasso art” at the annual meeting of the American Physical Society.
Audoly, Brun and Ribe call it “art,” as they chose to explore the aesthetic aspect of lassoing rather than its professional dimension — catching cattle. The scientists wanted to understand how one can perform such tricks as the “flat loop” — a horizontal spinning loop — the “vertical loop” or the well-known but complex “text skip,” in which the cowboy jumps back and forth through a large vertical loop.
The researchers pushed scientific precision to another level. They first consulted with Jesus Garcilazo, a Mexican professional working at Disneyland Paris. After initial trials with a small chain and some tape to close the loop, they finally bought a proper rope in the U.S.
Audoly, Brun and Ribe then built a rather basic robot able to spin a lasso. They found in Denver another cowboy to work with: Craig Ingram, now popular for his prowess in lasso tricks.
But the scientists’ interests go much further than the art of lasso spinning. The three of them are all specialists in “elastic and hanging threads.” This includes hair, trickles of honey, transatlantic submarine communications cable or even DNA molecules. Lassos are another example of this type of threads, with the distinctive feature of having a closing loop.
“It’s a well-known object yet there was no scientific research on it,” said Pierre-Thomas Brun, one of the researchers. "There is a fundamental interest in understanding why such different objects behave in similar ways.”
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How does it twirl? — Photo: Véronique PAGNIER
The researcher explained that the answers lie within the objects’ geometry and its relation with their dynamics. "The lasso gives us the opportunity to better understand these threads," he said.
After hours of practice — manually and with the robot — the French scientists confirmed the theory that three shapes appear depending on the rotation speed. The first one is a curved shape that looks like an elbow, in which the loop is closed and horizontal. The second one makes the rope look like a clothes hanger, with an open but vertical loop. The last one — the one researchers seek to achieve — is called “the flat shape,” in which the loop is open and horizontal.
In the end, the amplitude of the movement doesn’t matter much. The other factor to take into account is the length of the loop, which can be adjusted with a slipknot. The study predicts the favorable conditions needed to create the “flat loop”: Spin the rope twice per second, with at least 70% of the rope in the loop. "The typical beginner’s mistake is to start with a loop that is too small," Brun said. Don’t expect to make it work with less than a rotation a second. Another trick is to frequently untwist the rope with a small wrist movement, so as to prevent it from being completely tangled like old telephone cords.
“We didn’t do all of that just for pleasure. The most basic equations, which aren’t that complicated to pose, are difficult to solve in practice and remain poorly understood,” Brun said. “The lasso became a model problem to help us ask the fundamental questions. The study enables us to learn more about these equations.”
“The philosophy behind it is to use simple objects to get a sense of what is important in the abstract equations that describe them,” said Dominic Vella, a lecturer at Oxford University. Instead of catching cattles, the scientists caught realities that, until now, had eluded them.