Hacker News Reader

To quote Iain M. Banks, probably not :)

> "Sma," the ship said finally, with a hint of what might have been frustration in its voice, "I'm the smartest thing for a hundred light years radius, and by a factor of about a million ... but even I can't predict where a snooker ball's going to end up after more than six collisions." [GCU Arbitrary in "The State of the Art"]

View on HN

6? That can't be right. I don't know how big a GCU is, so the scale could be up to 1 OOM off, but a full redirection of all simulation capacity should let it integrate out further than that.

The target precision wasn't specified.

For ball-to-ball collisions, 6 is already a highly conservative estimate-- this is basically a chaotic system (outcome after a few iterations, while deterministic, is extremely sensitive to exact starting conditions).

The error scales up exponentially with the number of (ball-to-ball) collisions.

So if the initial ball position is off by "half a pixel" (=> always non-zero) this gets amplified extremely quickly.

Your intuition about the problem is probably distorted by considering/having experienced (less sensitive) ball/wall collisions.

See: https://www.lesswrong.com/posts/JehyrC6W3YTtdxw6S/a-primer-o...

Reply on news.ycombinator.com