CompuServe Thread

Gravity Math

2 messages in this thread
#21254From: GARRY R. OSGOODAug 19, 1989 7:47 PM
Notes: (1) Gravitational_Constant is 6.6695 if we measure masses in kilos, distances in kilometers and time slices in seconds. (2) the algorithm is an approximate solution to the n body problem, which has no exact solution. We cheat by first netting accelerations, then finding out how far objects move ***while assuming that the accelerations don't change!!!*** This is a false assumption, because the moment objects move even a little bit, all of the netted accelerations are changed a little bit — accelerations follow from proximities and proximities are changed by accelerations: an orbital mechanical Catch-22). We get away with this (approximately) as long as objects don't move significantly during the time slice we pick — we get caught when objects get close together: small distances –> big accelerations –> significant movement during the given time slice. (3) Don't ask me why there is no exact solution in (2). That answer would entail the practice of math I'm not licensed for, and I don't want to have the CompuServ Thought Police catch me. (4) I have this coded somewhere — an early Amiga effort developed under Workbench 1.0 using Manx 3.2. If I find it, I'll dust it off and post it, though I wouldn't be suprised if a spiffy version of this toy aready lurks in the libraries somewhere.
#21496From: Bob ShawAug 25, 1989 11:56 AM
GARRY, Glad to see you back. I'll have to work up a little thing using the 'Star Cluster'. The animation is postable, but not so interesting. Once the ball drops, the thrill is gone. The size verses the artistic merit does not justify a download. I'll come up with something a bit more fun and post that. Bob.