Where it shows up
The Ising model is the fruit fly of statistical physics, and its reach goes well past magnets. The same "agree with your neighbours, but noise fights you" rule describes a binary alloy sorting its two metals, a liquid boiling into gas near its critical point, and simplified neurons that fire or rest. It also anchors universality: very different systems share identical critical exponents near their transition, so measuring one teaches you about the rest. Image denoising, spin glasses, and opinion-spreading models borrow the same structure.
The knobs
- Temperature T: how much thermal jostling the spins feel. Cool below and domains lock in; heat above it and any order dissolves into noise. Park it near 2.27 to watch criticality itself.
- Coupling J: how strongly neighbours want to agree. Raising also raises , so a stiffer coupling needs more heat to melt. Changing re-randomises the lattice for a clean start.
- Field h: an external bias. Push it positive and up-spins (orange) win even without much cooperation; push it negative and teal takes the sheet.
- Speed: how many spin flips run each frame. Turn it up to evolve the pattern faster, without touching the underlying physics.