That thing, up above, is an optical illusion you probably recognize. It’s called a trefoil, and it was a popular physics mindbender: Could you make a knot out of a fluid, a fluid in the sense of physics, a never-ending, constantly circulating, self-contained system?
Turns out, you can.
Don’t believe us? Here’s the freaky-ass video:
https://c.brightcove.com/services/viewer/federated_f9?isVid=1
Look weird? It is weird, because this is literally the first time they have ever been observed in nature. How did the team at the University of Chicago pull this off?
To investigate, Dustin Kleckner and William Irvine of the University of Chicago, Illinois 3D-printed strips of plastic shaped into a trefoil knot and a Hopf link. Crucially, the strips had a cross section shaped like a wing, or hydrofoil.
Next, the researchers dragged the knots through water filled with microscopic bubbles. The result was a knot-shaped flow of moving bubbles.
This is particularly important because, well, we have no idea whether this happens naturally. For these knots to persist forever is currently impossible: That’d require a fluid with zero viscosity. But the fact is, they can be made to exist, and this might be important to understanding everything from how superfluids behave to improving airplanes to have less turbulence.
Also, it looks cool. It’s very important science look cool.
Wait, so if it exists, is it still an “optical illusion?”