whatA colony of light-makers on a dark field. Every cell leaks a signal into the water; the signal diffuses and decays; every cell reads it back and glows in proportion -- and glowing cells leak six times harder. That loop is the whole machine.

whyThe claim is quorum sensing's punchline: nothing... nothing... then everything at once. Below a critical census the field starves before it reaches threshold and the colony sits dark forever. Past it, the loop closes: the ledger measures a LONG induction (light below a tenth) ending in a SHORT ignition (a tenth to nine-tenths in a few seconds) -- the wait dwarfs the flash, and the whole colony crosses together. The final glow against density is a step, not a slope. And the quorum test, the classic flask experiment: click to squirt signal into the water -- a colony well below quorum shrugs it off and goes dark again, while one near the threshold ignites at once.

howA diffusing, decaying scalar field on a coarse grid, secretion spread over each cell's neighbourhood; the culture is STIRRED -- three-quarters of what a cell smells is the flask average (which diffusion conserves, so it is exactly the census), the rest its own neighbourhood; activation relaxes toward a sigmoid of that mixture with a one-second memory. The story grows the colony a few cells at a time until it ignites, holds the glow, then thins the plate and begins again. Everything seeded, fixed-step.