Every crowd is a few thousand cells moving in a bounded space, colliding at a rate set by how tightly they are packed, how loud the room is, and whether anyone is looking up. Most collisions are nothing. A few carry something across. Each page below takes one kind of room, runs it person by person, and reports what came out.
The headline finding is the spread. Under identical conditions — 1,200 people, four hours — a warehouse rave produces about 89× the human contact of a street crossing — even though the second is denser. Packing bodies together is not the same as putting people together, and the gap between those two things is most of what these pages are about.
Encounters started per person per hour, from a standard run of 1,200 people over 4 hours with a fixed seed. Density is shown alongside to make the point: the two columns are close to unrelated.
The crowds are simulated and are presented as such. Their constants are not invented: walking speed against density, the proxemic zones, the collapse of speech range with noise, the Widmark blood-alcohol curve and the conversational group limit all come from published work, cited on each page and in full inside the engine.
