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Author Topic: im a little confused......  (Read 3313 times)

supernova77

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im a little confused......
« on: May 17, 2011, 09:13:37 AM »
hi universe sandbox community. :P
now I have not played universe sandbox. (warning)

I'm a little confused with the physics i took a class even though I'm only a kid.... :)
now I really want to play this game and I'm SO gonna get it but I've been looking a us2 youtube videos, and I noticed when you speed up time the planets fling out of place! is it because when you speed up time the gravity and the speed affects it? like "every action has a reaction" or is it because this may happen later on?

which one?
supernova- cheers

bojo

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Re: im a little confused......
« Reply #1 on: May 17, 2011, 09:26:03 AM »
I'm sure ill be corrected if i'm wrong, but I believe it has to do with how the simulator calculates orbits. From what I understand of it, the larger the time step the less accurate those calculations will be. Although i'm sure Dan is hard at work trying to fix this.

Triplanetary

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Re: im a little confused......
« Reply #2 on: May 19, 2011, 08:47:30 PM »
Yeah, there's no real-world physics reason for it. Like bojo said, it has to do with the accuracy of the simulation. Basically how it works is that the simulation is broken up into "steps." At each step the simulation calculates the new position of each body. When each step represents a relatively small amount of time, and the positions are updated frequently, the simulation is accurate.

When the steps are far apart, for reasons that I won't get into (because I don't understand them well enough to explain them myself :P) the accuracy breaks down. As a sort of very simplistic explanation, imagine that you're drawing a circle by connecting dots. The more dots you use, the rounder it looks.

ChemicalBR0

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Re: im a little confused......
« Reply #3 on: May 20, 2011, 03:33:38 AM »
to put it even simpler
say you have a planet that orbits a star in 40 hours.

and you put the timestep to 20 hours every step.
the simulation is only doing 2 calculations per orbit of the planets position

that's  not enough points to calculate a clean orbit (2 points is only enough to calculate a straight line :)) and the planet gets thrown out of the system



Dan Dixon

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Re: im a little confused......
« Reply #4 on: June 10, 2011, 05:40:23 PM »
As you increase the time step you decrease the accuracy. More info here:
http://universesandbox.com/faq/#sim