# Why is earth's path is elliptical?

Why is earth's path is elliptical?why not circular?

Garth
Gold Member
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)?

mathman
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.

russ_watters
Mentor
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.

ideasrule
Homework Helper
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.

DaveC426913
Gold Member
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.