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So WHY are the orbits elliptical?? Is there a short understandable answer?

There was a similar question and here is a part of one answer..but it doesn't make any sense to me...

"..external force which existed during the formation of earth. This force on earth imparted earth a velocity that was greater then critical velocity to revolve in a circular path around sun but less than the escape velocity. Any body imparted with such velocity will rotate in an elliptical orbit.."

I can't make sense out of this explanation, but is it similar to the following statement....This is what I have read from other sources..: If the balance between large body's gravitational pull and centrifugal force is not perfect, the orbit will be elliptical, but to me it would mean that either the Moon will fall into the Earth or it will leave Earth's orbit, depending which force will be stronger...I really don't understand!!! Is there a purely logical explanation without complicated mathematical formulas???

Answers (4)

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aa10159262 profile image

The Sun is a gaseous (fluid) body, not solid; its mass shifts around. Similarly, the Earth has the Moon in orbit around it, so that the center of gravity of the Earth-Moon pair is constantly shifting. If you have two bodies, far removed from the gravitational influence of everything else, it is easy to show that their orbit is circular. But when you begin introducing multiple other bodies, close enough to affect one another, they all influence each other, and the orbit is no longer perfectly circular. It becomes elliptical.

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7 NOV 06, 1628 hrs, GMT

06513454f057 profile image

A circle is defined to be an ellipse with zero eccentricity - how "elliptical" it looks. Since this is only one of an infinite number of possible shapes for an ellipse, it would be very surprising to find a perfectly circular orbit anywhere. Even if there was one, the slightest gravitational influence from a passing asteroid or comet would stretch it out of shape.

Not to worry, though, we know elliptical orbits are stable or we wouldn't be here to talk about them.

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In fact, the moon IS crashing into the earth