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PhanTomCat
Teh Cat....



Registered: 09/07/04
Posts: 5,908
Loc: My Youniverse....
Last seen: 15 years, 2 months
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The Orbits of the Planets....
#8475981 - 06/02/08 06:05 PM (15 years, 11 months ago) |
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If the solar system was formed by a flat (accretion?) rotating CIRCULAR disc, why are the orbits of the planets now elliptical instead of circular....? And being that they are elliptical, do they follow the same path, or is it like a less exaggerated Spiro-graph motion - slightly moving the orbit/path each "rotation"....?
>^;;^<
-------------------- I'll be your midnight French Fry.... "The most important things in life that are often ignored, are the things that one cannot see...." >^;;^<
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deimya
tofu and monocle


Registered: 08/26/04
Posts: 825
Loc: ausländer.ch
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Re: The Orbits of the Planets.... [Re: PhanTomCat]
#8476089 - 06/02/08 06:25 PM (15 years, 11 months ago) |
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Nothing is perfect, and so the initial conditions given by the configuration of the primordial accretion disc where not perfectly circular, homogeneous, etc. There were bulges, density inhomogeneities and non-uniform speed distribution.
Also consider that once planets are formed, they all feel and apply forces from and to each others, and so you end up with quite a chaotic many-body problem. Only the vast distances and time scales involved in the problem give the impression of a stable system on the short term. See http://en.wikipedia.org/wiki/N-body_problem
Together with general relativity corrections, this interaction between planets is the reason why orbits are indeed a bit like spiro-graph. This effect is called precession of the perihelion and can be satisfyingly calculated in most cases considering only the effect of major planets like Jupiter and Saturn on others' orbits. For more precise results or for planet near the Sun you also need to account for corrections from general relativity effects.
If you're interested, here some relevant wiki articles
http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System http://en.wikipedia.org/wiki/Precession_(astronomy) http://en.wikipedia.org/wiki/Perihelion http://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_precession_of_Mercury http://en.wikipedia.org/wiki/Celestial_mechanics
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PhanTomCat
Teh Cat....



Registered: 09/07/04
Posts: 5,908
Loc: My Youniverse....
Last seen: 15 years, 2 months
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Re: The Orbits of the Planets.... [Re: deimya]
#8476233 - 06/02/08 07:05 PM (15 years, 11 months ago) |
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Thanx~....! 
That first link with the N-body problem is a bit over my head, but the others will be tasty morsels....
>^;;^<
-------------------- I'll be your midnight French Fry.... "The most important things in life that are often ignored, are the things that one cannot see...." >^;;^<
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deimya
tofu and monocle


Registered: 08/26/04
Posts: 825
Loc: ausländer.ch
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Re: The Orbits of the Planets.... [Re: PhanTomCat]
#8478465 - 06/03/08 05:41 AM (15 years, 11 months ago) |
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You can concentrate on the section about the three-body problem. http://en.wikipedia.org/wiki/N-body_problem#Three-body_problem As you can see from the animation, three-body dynamics is already chaotic. Now just imagine how it is in details for our solar system.
Perfect elliptical orbits are but convenient approximation
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