Imagine a massive mug of cold, dense cream with hot coffee poured on top. Now place it on a rotating table. Over time, the fluids will slowly mix into each other, and heat from the coffee will eventually reach the bottom of the mug. But as most of us impatient coffee drinkers know, stirring the layers together is a more efficient way to distribute the heat and enjoy a beverage that’s not scalding hot or ice cold. The key is the swirls, or vortices, that formed in the turbulent liquid.