The Galton Board
Bouncing balls always draw the same bell
Francis Galton's quincunx is a triangle of pegs. Release a marble at the apex: at every peg it veers left or right on a fifty-fifty coin flip, until gravity drops it into one of the catch bins along the floor. Drop ten thousand marbles and the bins fill — always — into the shape of the normal distribution. The bell is not a coincidence; it is the Central Limit Theorem made tactile: any sum of many independent small random kicks converges to a Gaussian, no matter what the individual kicks look like.
