Why is earth's path is elliptical?

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Discussion Overview

The discussion centers around the nature of Earth's orbital path, specifically why it is elliptical rather than circular. Participants explore theoretical and conceptual aspects of orbital mechanics, referencing Kepler's laws and the implications of eccentricity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that a circular orbit is a special case of an elliptical orbit with zero eccentricity, which is not achievable in reality due to the Earth's eccentricity being approximately 0.016722.
  • There is a question about the existence of truly circular orbits, with some suggesting that while artificial satellites may have very small eccentricities, achieving exactly zero is improbable.
  • One participant argues that the motion of the Sun contributes to the elliptical nature of Earth's orbit, while another counters that the Sun's motion does not affect the shape of orbits as there is no privileged reference frame.
  • Another participant challenges the understanding of orbital mechanics, suggesting that the explanation provided is limited and outdated.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Sun's motion and the nature of circular orbits. There is no consensus on the correctness of the explanations provided, and the discussion remains unresolved regarding the influence of reference frames on orbital shapes.

Contextual Notes

Participants reference Kepler's laws and eccentricity without resolving the complexities involved in defining orbits in different reference frames. The discussion highlights the nuances of orbital mechanics and the challenges in achieving circular orbits.

kamalee
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Why is Earth's path is elliptical?why not circular?
 
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Welcome to these Forums kamalee!

kamalee said:
Why is Earth's path is elliptical?why not circular?
Why should it be circular?

A circular orbit is a special case of the general elliptical orbit in which the eccentricity is exactly zero.

As nothing is exact in the real world the Earth's orbital eccentricity is near zero but not exactly zero.

In fact e = 0.016722, therefore its orbit is elliptical, just as Kepler's laws says it should be...

Garth
 
Last edited:
Do any truly circular orbits exist (Eccentricity = 0)?
 
BosonJaw said:
Do any truly circular orbits exist (Eccentricity = 0)?

None of the planets have 0 eccentricity. I suspect most of the artificial Earth satellites have a very small eccentricity, so it is possible one or more might be zero. However it would be hard to maintain since the moon would exert some perturbing force.
 
BosonJaw said:
Do any truly circular orbits exist (Eccentricity = 0)?
Well, the answer can be seen in probability: Since, as Garth said, 0 is just one possible eccentricity, the odds of that happening are infinitessimaly small. So no, it would really be impossible to have an exactly zero eccentricity.
 
Thanks Guys!
 
There is a simple explanation. The sun is in motion. It is not static in the universe.
The Earth revolves around a moving object. Hence an elliptical orbit.
No Math required on this one.
 
Visualedtech said:
There is a simple explanation. The sun is in motion. It is not static in the universe.
The Earth revolves around a moving object. Hence an elliptical orbit.
No Math required on this one.

As someone mentioned in the other thread, that's incorrect. The Sun doesn't care whether it's in motion or not; there's no way to tell anyhow because there is no privileged reference frame.

When talking about the shapes of orbits, it's usually done from the reference frame of the barycenter. Obviously, an orbit's shape is going to be different if you watch it from, say, the reference frame of a cosmic ray.
 
Visualedtech said:
There is a simple explanation. The sun is in motion. It is not static in the universe.
The Earth revolves around a moving object. Hence an elliptical orbit.
No Math required on this one.
Visualedtech, stick to what you know. Your knowledge of orbital mechanics is ... limited.


Also, this post is two years old.
 

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