Hi user group,
I discovered Celestia a week ago, and I've found myself playing around with a lot for fun. I have some questions on the inner workings of the program. I suppose I could download the code and look at it, which I will probably do sometime, but asking a question here is probably easier.
How are the planeyary obits generated? Is from celestial mechanics first priinciples, i.e. from using a full (say) Runge-Kutta solution of the coupled differential equations? Or is it based on some perturbation approximation?
How well do the orbits tally with (say) detailed ephemerides ?
It's a great program!
Best regards,
s?ren molander
How does Celestia generate solar orbits?
s?ren,
Celestia does not include any gravitational calculations. Instead, it uses the VSOP87 theory to position the planets. (The appropriate one is invoked by a CustomOrbit declaration in solarsys.ssc.) The VSOP87 polynomials include enough of the relevant gravitational effects to make them accurate for most of the planets to better than one arc second (as seen from the Earth) from about 1000 BC to 3000 AD.
Ref:
Bretagnon P., Francou G., : 1988, Astron. Astrophys., 202, 309.
Celestia does not include any gravitational calculations. Instead, it uses the VSOP87 theory to position the planets. (The appropriate one is invoked by a CustomOrbit declaration in solarsys.ssc.) The VSOP87 polynomials include enough of the relevant gravitational effects to make them accurate for most of the planets to better than one arc second (as seen from the Earth) from about 1000 BC to 3000 AD.
Ref:
Bretagnon P., Francou G., : 1988, Astron. Astrophys., 202, 309.
Selden
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mluckham
Simulating Addition / Moving / Removal of Orbiting Bodies
Can Celestia be used to simulate what would happen if new bodies were introduced to an orbiting system - example, what if the moon were 10% closer to earth. Or, what if the moon was suddenly removed?
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tony873004
- Posts: 132
- Joined: 07.12.2003
- With us: 21 years
- Location: San Francisco http://www.gravitysimulator.com
Can Celestia be used to simulate what would happen if new bodies were introduced to an orbiting system - example, what if the moon were 10% closer to earth. Or, what if the moon was suddenly removed?
No, because it doesn't use the pre-mentioned Runge-Kutta routine or any other gravitational simulation routine. If you want to simulate stuff like that, you can use Gravity Simulator. (http://www.gravitysimulator.com). There's no fancy graphics, everything is just pixels and plain circles, but you can suddenly remove the moon if you want. Or move it, or add additional moons with your own custom masses.
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tony873004
- Posts: 132
- Joined: 07.12.2003
- With us: 21 years
- Location: San Francisco http://www.gravitysimulator.com
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Mikeydude750
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- With us: 22 years 10 months
- Location: Wisconsin