Termyn8or
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Joined: 11/12/2005
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xB, the orbit does not change like that. If it did it would change exponentially and decay so fast that none of would be here. To be defined as an orbit it must be self sustaining, which means there is an equilibrium between the gravity of the sun and the velocity of the Earth as it relates to the centripetal force. The centripetal force exactly balances out the gravity exerted by the object which is orbited. What many find hard to belive is that the mass of the orbiting object is irrelevant. The only exception is when the mass of the orbited and the orbiting objects are near the same, and they then affect each others' path. That is not what we are talking about here.
The Earth is 93 million miles away, so the Earth cruises around at sonething like 9.26 miles per second, which counterbalances the gravity precisely. If it did not, we would not be here. And there is no mentionable friction in space, so it can go on practically indefinitely.
Now the moon goes around the Earth about every month, and that, at that SPECIFIC distance produces precisely the force needed to counteract the force of the Earth's gravitational field.
At lower orbits higher orbital velocities are needed, and that fact was put to use to bring you satellite TV. The satellites your dish picks up are in what's called a geosynchronous orbit. Remember since their mass is small compared to the orbited object, it has no effect to mention. At any mass this occurs at about 22,000 miles above the surface of the planet. At that height, the orbital velocity is the same as at any given place on the surface of the planet. This all occurs over the equator, it just doesn't work anywhere else. This is why your dish does not have to move around like a RADAR dish in an old time scifi movie.
Now don't get me wrong, the Earth's orbit around the sun is not perfectly round, that means it has an apogee and a perigee, which are the closest and farthest points. This is not the mechanism by which the seasons change though, that is chiefly caused by the "wobble" in the Earth's own rotation. However cyclic orbital differences can coincide with the seasons and either enhance or abate the normal effect of same. Those differences are on a shorter basis timewise though, and don't have very much to do with any significant climate change. It may go through cycles over the span of years, and I admit I don't know exactly how long that cycle lasts, but in the end analysis, it balances out because if you got less sun during the winter you will get more during the summer or vice versa. The major factor is still that wobble.
Can it affect the weather ? Hell yes, but it does not bring on a climactic change because it seems to be pretty well balanced.
However elliptical orbits can and do change in their roundness, but that happens very slowly. In other words if you thought of east and west of the sun, the apogee and perigees' relative positions could change, which will have some effect. A small one, but there nonetheless. The problem comes when the actual roundness of the orbit changes, and they generally do not become rounder, they become more eliptical. Right now the Earth's perigee and apogee in relation to the sun is only a couple million miles if that. If the orbit rounds out, it will contribute to a more stable [seasonally] climate, but just barely. If, however the orbit becomes more eliptical, that is trouble. If that happens it's effect will become significant, and cause drastic seasonal changes.
If someday the apogee is only 60 million miles, somewhere in the orbit this planet would probably have to swing out to about 150 million miles. If that happens the Earth will become uninhabitable, because we are talking about 200-300F ambient during the apogee and possibly a hundred below zero during the perigee. We could play games and use technology to survive for a time, but it will not work for long because the vegetation will die off. Luckily before any of this becomes significant we shall have destroyed ourselves. We are taling millions, or billions of years into the future.
Hopefully that is cleared up, the orbit is of no concern in this matter. If it has an effect, it is seasonal, and quite negligable, for now.
T
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RE: PRAVDA: "Earth on the Brink of an Ice Age" - 
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I have a question for you Hippie, I think you're our resident brain. 
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