These patterns are made with nothing but sound. They are called Chladni patterns, after the German physicist Ernst Chladni (1756–1827) who used his violin bow to vibrate a metal plate with sand on it. A pattern appears in the sand when a surface is made to vibrate at certain resonances. A plate or membrane vibrating at resonance is divided into regions vibrating in opposite directions, bounded by lines of zero vibration called nodal lines. The sand is moved around the plate and collects at the nodes on the plate. The patterns that form are highly symmetrical and beautiful.