I’m a guy with hands that aren’t overly big so much as they are clumsy and non-dexterous – take note, ladies – so the only knots I’m any good at taking apart are baked and covered with pretzel salt. When physicists refer to knots, though, they’re talking more about closed loops with no ends to untie, such as the trefoil, Hopf Link, or Olympic rings. Discussions about theoretical fluid rings have been around since mathematical physicist and temperature superstar Lord Kelvin proposed that atoms were knots in the ether, and now they’ve gone from the world of theory to a scientific reality.
The University of Chicago’s Dustin Kleckner and William Irvine used 3-D printers to create a plastic trefoil knot and a Hopf link, each with a wing-shaped cross section. When they dragged the knots through a pool of water filled with microscopic bubbles, the acceleration of hydrofoils left a knot-shaped vortex in its wake, which sucked in all the bubbles and created a flowing formation shaped like a knot, which was the first fluid knot ever created in a lab. Cue the fireworks and watch the mesmerizing video below, which compiles shots of the knots imaged by lasers.
Though the knots appeared to dissipate after rotating for a while, the researchers, who presented their findings in a study for the journal Nature Physics, were unable to tell if this meant the knots completely vanished, or if it still existed on a smaller level. Ideal fluids have no viscosity, so an ideal fluid knot would never dissolve. And I thought bourbon was the ideal.
Further study could lead to a better understanding of more functional aircraft wings by advancing how the airflow is directed around the wing, as well as a solid step in grasping what superfluids may consist of. And, of course, there’s always the chance of bigger and more complicated knots. “We don’t think there is a fundamental limit,” says Irvine. “We’re trying to make all sorts of things.” And if one of those things is “a lot of people confused,” then they’ve definitely done it.