Tea leaf paradox

The tea leaf paradox describes a phenomenon where tea leaves in a cup of tea migrate to the center and bottom of the cup after being stirred rather than being forced to the edges of the cup, as would be expected in a spiral centrifuge.

Quotes

 * I very much enjoyed your delightful explanation of the formation of meanders. It just happens that my wife had asked me about the “teacup phenomenon” a few days earlier, but I did not know a rational explanation. She says that she will never stir her tea again without thinking of you.
 * Erwin Schrödinger to Albert Einstein, 23 April 1926