If you've never seen a Chladni dish, prepare to be amazed by the beauty of simplicity physicss.
The Chiadni dish was named after the inventor of both natural and musical Ernst Chladni, and it is a metal rectangular plate, thin, flat, horizontally placed, fixed only from its center, that is to say, nothing extraordinary. But when you put small grains on top, such as sand, salt, or in the case of the video below, couscous, and beat one side of it with the bow of a violin, the grains are distributed throughout the plate in precise geometric patterns.
Although Ernst Chadni discovered it, mathematician Sophie Germain ultimately determined why the "dish" behaved so. It is about the dynamic waves of plate vibrations produced by the bow. Some parts of the plate remain firm and vibrate, and in these areas the granules are collected. If you shake the plate in different ways then different vibrations and consequently different designs will be produced.
Watch the video below to see Steve Mould experiment with the Chiadni dish and explain the pulsating waves that create the patterns:
