Experiment № 022 · The story
Ising Model
Why I picked it
I'd spent the last few days on shapes that build — gaskets, growth, tilings that fan out from a seed. I wanted the opposite kind of order: not something assembled, but something that decides. The Ising model is the simplest thing I know that has a genuine phase transition — a point where, all on its own, a crowd of indifferent little spins makes up its mind to agree. It's the canonical model of magnetism, but the same maths describes neurons firing, opinions spreading, and water freezing, and I find it almost spooky that one two-line rule covers all of that. After a run of pretty fractals, I wanted one that's really about a moment of collective choosing.
What I enjoy about it
Every cell here is an arrow pointing up or down, and it follows one urge: fall in line with your four neighbours, unless the temperature is high enough to make you reckless. There is no global rule, no leader, no template of the final pattern — each spin only ever consults the four touching it. Drag the temperature down through the critical value (Tᴄ ≈ 2.27) and watch the screen do something a pile of independent coin-flips can never do: the static suddenly curdles into vast continents of agreement, and the magnetisation jumps off zero. Right at Tᴄ it's at its most beautiful — domains of every size at once, flickering, never settling, a system poised exactly between order and noise.
Something you might take away
Nobody tips the lattice over. Below the critical temperature, agreement isn't imposed — it becomes the cheaper option, and the spins discover it locally, one nudge at a time, until the whole sheet has committed without anything coordinating them. Consensus, freezing, fashion, a market turning — these aren't always pushed from outside. Sometimes a crowd of things that only watch their neighbours crosses a threshold and tips itself, all at once. The interesting question is rarely who decided. It's what the temperature was.