Swans on Tea

Over at Popsci, the physics of tossing a ping-pong ball into a beer cup, with videos of, well, tossing a ping-pong ball into a beer cup, under various conditions you’d find in a dorm (starting with the unlikely presence of beer cups).
These guys are pretty amazing. And the nonchalance with which they accomplish each trick [...]

From arXiv, rotation of a thin film of water when subjected to perpendicular electric fields.
The question is: what’s causing the rotation? The team can easily control the direction and speed of rotation by varying the relative angle and direction of the electric fields, which rules out the possibility that convection is causing the rotation (something [...]