N-Body GravityDrag to orbit, scroll to zoom. 2,304 equal stars, each pulling on every other. From a slowly spinning disc the cloud caves in on itself, throws off spiral arms, then settles into a dense core while a few stars get slingshot out for good.Newton’s 1687 law of gravity solves two bodies exactly; add a third and Poincaré proved in 1890 there is no tidy formula — the motion is chaotic. So galaxies are studied by brute force: compute all 5.3 million pulls each step and just step forward. The core-plus-escapers ending is called “violent relaxation.”