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eccentricity of orbit


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why is it that planets and other heavenly bodies only follow the elliptical path. (eccentricity < 1)?

 

And not circular?

 

As a planet like earth would extend its gravitational field equally in all directions and produce a circular "ripple" in space-time?

 

A circle when stretched, so as to change its eccentricity produces an ellipse.

 

Does that tell us something about the space-time matrix?

 

Please elicit your opinions.

 

Thanks in advance.

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The solutions for a closed two-body orbit is an ellipse, of which a circle is a possibility, but the details of the ellipse depend on the velocity of the orbiting body at a specific point. If the velocity is not purely tangential, the orbit will not be a circle. There is no way for a radial force to change this; one must rely on weaker effects (which I expect become even weaker as the eccentricity approaches 1).

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BTW, from the Kepler Mission we have learned that circular orbits are uncommon. Our solar system, with nearly circular orbits for most of the planets, is rare, which supports the Rare Earth hypothesis.

 

Circular orbits give a solar system long-term stability, so life on Earth could not exist without our lucky circular solar system.

Edited by Airbrush
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BTW, from the Kepler Mission we have learned that circular orbits are uncommon. Our solar system, with nearly circular orbits for most of the planets, is rare, which supports the Rare Earth hypothesis.

 

Circular orbits give a solar system long-term stability, so life on Earth could not exist without our lucky circular solar system.

Or the planets with circular orbits are more difficult to detect because of their physical caracteristics. But I don't see why.

 

In our Solar system, we have Mercury whose orbit is seriously eccentric. Mars isn't very circular neither. Most minor planets have eccentric orbits, with Pluto being an extreme case.

Edited by Enthalpy
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why is it that planets and other heavenly bodies only follow the elliptical path. (eccentricity < 1)?

 

And not circular?

 

As a planet like earth would extend its gravitational field equally in all directions and produce a circular "ripple" in space-time?

 

A circle when stretched, so as to change its eccentricity produces an ellipse.

 

Does that tell us something about the space-time matrix?

For any satellite to have a perfectly circular orbit it must stay the same distance from the sun or whatever it's orbiting. This is not indicative of any trait of the spacetime continuum as much as the fact that the gravitational pull is stronger near the heavenly body. As a satellite nears the sun it speeds up and is then carried further out into space. Read up on Kepler's Laws of Planetary Motion. http://csep10.phys.utk.edu/astr161/lect/history/kepler.html

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Or the planets with circular orbits are more difficult to detect because of their physical caracteristics. But I don't see why.

 

In our Solar system, we have Mercury whose orbit is seriously eccentric. Mars isn't very circular neither. Most minor planets have eccentric orbits, with Pluto being an extreme case.

I cannot think of why a circular orbit is tougher to detect than a very eliptical orbit. Sorry I can't remember where I heard this, I think it was an episode of "How the Universe Works" on Sci channel.

 

Although Mercury has a seriously eccentric orbit, it will never disturb Venus, for at least Billions of years. The other planets all have slightly eliptical orbits, but they are very close to being circular.

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