Strange pentagon is the best shape for stirring two liquids together

The best way to mix together two liquids – like milk and coffee – is by moving two pentagonal stirrers in a jagged motion

By Karmela Padavic-Callaghan

You’ve been stirring your coffee all wrong. According to a series of simulations, not only should your stirring implement be shaped like a weird pentagon but you should use two of them and move them in a jagged half circle before letting vortices generated in the fluid do the rest.

Maximilian Eggl at University of Mainz Medical Center in Germany and Peter Schmid at King Abdullah University of Science and Technology in Saudi Arabia used simulations and an algorithm to determine what shape is …