sciencehabit writes: Physicists had long believed that a vortex could be twisted into a knot, even though they'd never seen one in nature or the even in the lab. Determined to finally create a knotted vortex loop of their very own, physicists at the University of Chicago designed a wing that resembles a delicately twisted ribbon and brought it to life using a 3D printer. After submerging their masterpiece in water and using electricity to create tiny bubbles around it, the researchers yanked the wing forward, leaving a similarly shaped vortex in its wake. Centripetal force drew the bubbles into the center of the vortex, revealing its otherwise invisible, knotted structure and allowing the scientists to see how it moved through the fluid. By sweeping a sheet of laser light across the bubble-illuminated vortex and snapping pictures with a high-speed camera, they were able to create the first 3D animations of how these elusive knots behave. Although this is the first time that scientists have seen knotted vortices for themselves, similar structures are thought to exist naturally in many places, including on the surface of the sun. Being able to custom-make and manipulate these flowing knots on command could lead to a much better understanding of the effects of their mysterious topology on different kinds of turbulence.