Opus 5.5 writes code to render 1,000 double-pendulum chaos animation
Using Claude Code, the author had Opus 5.5 write 151 lines of plain JavaScript to simulate 1,000 double pendulums going from sync to chaos in a 9-second 1080p animation.
I released 1,000 double pendulums from the same height. Each one starts a billionth of a radian away from its neighbour. For 9 seconds they move as one. The counter in the corner tracks how far apart the tips are: 1 second: about 1 micrometre 10 seconds: 0.8 mm 13.7 seconds: over 1 metre After that the single white arm explodes into a rainbow cloud filling the whole reachable disc. The math stays exactly the same. Energy is conserved to 3 parts in a billion. The motion is fully deterministic, and a millionth of a radian of uncertainty in the start still makes it unpredictable after 14 seconds. That is why weather forecasts have a horizon no computer can push very far. Claude Opus 5.5 wrote it in Claude Code: 151 lines of plain JavaScript, no libraries, RK4 at 1,200 steps per second, 1080p render in about 100 seconds.
This post quotes another post: x.com/yumzlef/status/2079898642614268334