Cimática
Chladni figures — geometry born from vibration. Fourteen thousand sand grains ride a vibrating square plate, drifting toward the nodal lines where the plate stands still and getting shaken hardest where it moves most; grain-grain exclusion spreads the piles into the continuous sand ridges real plates show. The loop sweeps six standing-wave modes of increasing intricacy: at each transition the settled figure bursts apart and recrystallizes into the next, pure standing-wave physics with nothing drawn but the grains.