Imagine a hurricane with an eye in the shape of a propeller amid the swirling clouds. Physicists have observed something almost as strange in whirlpools that they made by swirling liquids in a novel way. Within the whirlpools, they've seen three-blade-propeller shapes as well as regular polygons, including squares and hexagons.
The behavior of liquids in rotating containers has long fascinated physicists. For instance, in a famous late-1600s study, Isaac Newton pondered why the surface of water in a rotating bucket becomes concave.
In the new experiments, Tomas Bohr and his colleagues at the Technical University of Denmark in Lyngby observed liquids in a cylindrical, Plexiglas container