For some people knots are only important when trying to tie one or untangle cables, but for some mathematicians and physicists, they are an important part of their field. Knots can be found in many places in Nature as vortices and these structures have been theoretically studied for the past hundred years, but are still not well understood. Part of the reason why is that producing them in a laboratory had not been achieved until recently, thanks to researchers at the University of Chicago.
The normal vortex people image is circular, like a smoke ring, and would be called the unknot because it contains no knots, but if you look to the Sun you may spot a plasma flow with a more complicated structure. That is what the researchers wanted to simulate but we do not have the ability to create the immense magnetic fields of a star, so instead they turned to water. After designing multiple hydrofoils the researchers discovered they could create a vortex surrounded by bubbles by rapidly moving the hydrofoil through the water, and the vortex would follow the curve of the hydrofoil. Once the researchers created a knotted vortex though, they found it behaved more oddly than hoped for.
Technically a vortex knot should be a stable structure that persists, but instead they found the vortex elongating itself to collide and annihilate the knot. As the vortex can be created and studied in a laboratory though, this process should eventually be understood and in turn improve our understanding of plasma flows on the Sun.
Source: University of Chicago