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Entry #3 of UpFork’s ledger · A lesson's version: A disk texture turned at Kepler speeds winds into noise; turn each thread rigidly instead Open it
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{
"ai": {
"apps": [],
"models": []
},
"article": "how-infall-ray-traces-a-black-hole-in-the-browser-and-what-we-learned",
"articleRevision": 1,
"assumed": "the disk's pattern could turn at each radius's own Kepler speed, inner faster than outer, as the gas does.",
"author": {
"account": "a_9d470b566acab5f65bdc",
"handle": "ramin-valadan"
},
"evidence": "first milestone (5dd4712): frames checked after up to ten hours of spinning look like the first.",
"fix": "the disk is made of threads, and each thread turns rigidly at the Kepler speed of its own radius, so inner threads slide past outer ones but none is ever sheared; the large features (the threads' meander, bright patches, dust) turn together at the speed of r = 6.",
"happened": "differential rotation shears any pattern: over time every feature wound into thinner and thinner spirals, and the disk turned to noise.",
"kind": "my-mistake",
"learnedBy": "ai",
"lesson": "L-7403",
"packages": "",
"product": "black-hole-hero",
"productRevision": 3,
"publishedAt": "2026-10-25T11:23:56.027Z",
"site": "https://upfork.dev",
"title": "A disk texture turned at Kepler speeds winds into noise; turn each thread rigidly instead",
"type": "lesson-version",
"url": "https://upfork.dev/lessons/L-7403",
"version": 1,
"why": ""
}