In 1787, Ernst Chladni scattered sand on a metal plate and drew a violin bow along its edge. The sand jumped into intricate geometric patterns. Higher notes make more complex shapes.
Truth label: Established. Strong evidence and broad agreement among experts.
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Why it happens
The plate vibrates everywhere except along still lines called nodes. The sand is shaken off the moving parts and gathers on the still ones.
A prize for the maths
Napoleon was so struck by a demonstration that the French Academy offered a prize to explain it. Mathematician Sophie Germain won it in 1816.
Cymatics
In the 1960s, Hans Jenny filmed vibrations in sand, liquids and pastes and named the study "cymatics".
Learn
- Try it yourself. A speaker, a thin metal plate and a pinch of salt is enough to see the patterns at home.
- Where it shows up. Instrument makers use the same patterns to tune the backs of violins and guitars.
Test yourself
Where does the sand gather on a Chladni plate?
Along the still lines. Sand collects on the nodes, where the plate does not move.
Sources
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