A field guide to emergence

Nobody is in charge

Simple rules, followed locally by many small parts, build structures that none of the parts know about.

A termite has no blueprint for the mound. A starling has no picture of the flock. A grain of sand has no idea it is part of an avalanche. Each reacts only to what is right next to it, and yet the whole has a shape.

This is a set of short interactive essays, one phenomenon each. Every chapter has a live simulation in the middle of it. Change the rules and watch what breaks. The pattern above comes from the first chapter. It is a sandpile that started as 9,000 grains on one square and spread out into a round, symmetric pattern. A grain is still dropped on the centre every frame, and orange flashes where the avalanches run.

1. The sandpile

   One grain at a time, until one grain moves half the pile. Self-organized criticality.
2. The flock

   Boids that follow three steering rules with no leader, and what real starlings do differently.
3. Spots and stripes

   Two chemicals that react and spread at different speeds, and the spots and stripes they paint.
4. The ant and the highway

   About ten thousand steps of chaos, then a road. Nobody has proved it always happens.
5. Slime that builds networks

   A brainless cell that prunes a maze, and a crowd of particles that draws networks between food.