Science

Vortex Knot Theory Becomes Reality

By Pierre Dumont , Mar 04, 2013 07:16 PM EST
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Physicists from the University of Chicago have succeeded in creating a vortex knot.

For those unfamiliar with the term, this type of accomplishment is basically like tying a smoke ring in a knot. It's a remarkable accomplishment, given that the knotted vortex has existed in theory for over a century but never actually has been created.

The vortex can be found in many parts of nature, mostly air or water. Humans create them too by doing things like blowing smoke rings. This marks the first occasion on which physicists have been able to tie one in a knot.

The study has important implications, making it easier for scientists to study all kinds of twisty marvels, such as the sun's outer atmosphere. It may also mean that the "knottedness" of an object could be as important as things like energy and momentum.

"If confirmed, this would deepen our understanding of the dynamics and connections between many disparate physical fields," says assistant professor in physics William Irvine. "We don't know if it's true or not, but I think we can finally test this in experiment. There's actually around 50 years of theory on this subject with no clean experiments."

The idea goes all the way back to Lord Kelvin, who theorized that atoms were essentially knotted vortices themselves.

To conduct the study, the physicists used a 3-D printer to make small replicas of airplane foil wings. They then submerged them in water and yanked them forward very quickly. Water filled the space left by the airfoil, and since the airfoil was knot-shaped, the liquid vortex took the same shape. Although the vortex knot was only visible momentarily, the scientists captured it with video using a high-speed laser scanner. The success of the project means that scientists should now be able to create the knotted vortex as they see fit for experimental purposes.

Irvine himself became interested in knot physics while doing his postdoctoral work at New York University. He says he saw a smoke-ring demonstration in Washington Square Park and began to wonder if he could cause smoke rings to become tangled.

"At some point the enthusiasm wanes and you worry about whether there's a very good reason why nobody has ever done this," Irvine says. "But sometimes going into a new field with a little naivete can be helpful."

(Edited by Lois Heyman)

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