Why Do Revolving Bodies Have Elliptical Orbits?

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Discussion Overview

The discussion explores why revolving bodies have elliptical orbits rather than perfectly circular ones, touching on concepts from physics, mathematics, and celestial mechanics. It includes considerations of gravitational forces and the nature of orbits in different contexts, such as satellites and Saturn's rings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question the existence of perfectly circular orbits in nature, suggesting that perfect circles are a mathematical abstraction.
  • It is proposed that ellipses are the trajectories of particles in a 1/r potential, and that different gravitational force relations could lead to different orbit shapes.
  • One participant raises a comparison regarding Saturn's rings, questioning whether their motion is governed by gravity in the same way as celestial bodies.
  • Another participant suggests that while a satellite in a circular orbit can become elliptical if perturbed, the nature of Saturn's rings involves individual orbits that are not perfect circles, despite their average being closer to circular.

Areas of Agreement / Disagreement

Participants express differing views on the nature of orbits, particularly regarding Saturn's rings and the concept of perfect circular orbits. There is no consensus on these points, and the discussion remains unresolved.

Contextual Notes

Participants note the dependence on gravitational force relations and the implications for orbit shapes, but do not resolve the complexities of these relationships or the definitions of circularity.

Shahin.Omar
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Why revolving bodies have their orbits elliptical and not perfectly circular (please correct me if I am wrong)?
 
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Shahin.Omar said:
Why revolving bodies have their orbits elliptical and not perfectly circular (please correct me if I am wrong)?
Is there anything in nature that is perfectly circular? Perfect circles exist in math only.
 
Because ellipses (technically, conic sections) are the trajectories of particles in a 1/r potential. If gravity had a different relation of force vs. distance, there would be different shaped orbits.
 
Vanadium 50 said:
Because ellipses (technically, conic sections) are the trajectories of particles in a 1/r potential. If gravity had a different relation of force vs. distance, there would be different shaped orbits.

Just for a comparison, and I actually wonder about it: Celestial bodies revolve around other objects due to gravity, does the same apply to Saturn's rings too (or is it just like Saturn's atmosphere)?

I was looking for an example for a circular orbit. Saturn's rings are a set of large number of bodies and they together form a perfect circular orbit.
 
If a satellite were in a circular orbit, but then it gets knocked by a meteoroid so that the direction of its tangential velocity is no longer exactly perpendicular to the direction of the gravitational force, that would make the orbit become elliptical.
 
Shahin.Omar said:
Saturn's rings are a set of large number of bodies and they together form a perfect circular orbit.
They don't have one orbit, just individual orbits which are not perfect circles. The average of the individual orbit is closer to the circle but not a perfect circle either.
 
A.T. said:
They don't have one orbit, just individual orbits which are not perfect circles. The average of the individual orbit is closer to the circle but not a perfect circle either.

Thanks for the information, and is gravity responsible for their revolution as it is for the revolution of other celestial bodies?
 

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