Faraday WavesDrag to orbit, scroll to zoom. Shake a shallow dish of fluid past a critical strength and the flat surface shatters into a standing pattern of ridges — stripes, a checkerboard, or a honeycomb — that sits still even though the dish keeps bouncing. The trick: each ridge only needs a nudge on every OTHER shake to keep itself going.Michael Faraday noticed this in 1831 and clocked something odd: the ripples repeat at HALF the shaking rate. Benjamin & Ursell (1954) showed why — each ripple obeys a Mathieu equation, the same maths as a swing pumped at twice its natural rhythm. Which shape wins, stripes, squares, or hexagons, is settled by how ripples running in different directions reinforce or cancel each other — a pattern-selection puzzle mapped out by Douady and by Zhang & Viñals.