Most of the interesting equations in physics cannot be solved with pen and paper. Three bodies pulling on each other, a fluid going turbulent, 10^{23} spins deciding whether to become a magnet — for these, the pen runs out and the computer takes over. Computational physics is the craft of turning a physical law into an algorithm and letting a machine grind out the answer, step by tiny step.

This branch is hands-on: integrating equations of motion, finding roots and solving linear systems, Monte-Carlo methods and the Ising model, solving partial differential equations on a grid, N-body and molecular dynamics, and fitting models to data. The code here is runnable in the browser, so you can change it and watch physics happen.