Quote Originally Posted by Thorne View Post
Then you're talking about the Solar Wind, then? Basically, material ejected from the Sun and streaming outwards into space. I would think this would make it even less likely to move a planet. Most of the particles of the Solar Wind are deflected by the Earth's magnetic field, and so wouldn't actually provide any drag, or push, to move the planet.

On the other hand, the Sun's gravity isn't going to change significantly, but as it expands it will spread out with the material of the Sun. It might possibly reach a point where the pull of the Sun's gravity will no longer act like a point source. I wouldn't want to even TRY to calculate the results of that!

As for orbits, a single planet can orbit it's star at almost any distance, depending only on the mass of the star and the speed of the planet. When you add additional planets things become more complicated, and there will indeed be optimal orbits formed. But remember, as the Sun expands it will easily engulf Mercury, and Venus. These changes will have an effect on the Earth's orbit as well.

And you still have the problem of the Earth's momentum. The Sun's expansion will be fairly rapid, on an astronomical scale. I don't know if there would be enough time to move the Earth aside before it became engulfed.
Sighs a lot of the stuff your speaking off is only in effect if you use only the outdated Newtonian physics (which in a lot of cases is perfectly ok on the normal levels of the macro scale) ...a lot of what Im talking about is using Relativity and quantum physics. Where gravity and space-time act much differently than just a bunch of spinning planets with mass and velocity. Space -time has wrinkles and gravity pressure waves (the arms of the galaxey wouldnt exist without them btw). The natural outward pressure of the sun thats driving the solar wind currently doesnt generate all that much force...enough to push bad particles through the atmosphere or burn off any planet's atmosphere that doesnt have a stong enough magnetic field but over all not so powerful. Now when the sun transitions to red giant status, its gravitational aspect will change, the allready existing pressure waves that act like troughs in the fabric of spacetime that the planets orbit within...will also change. Theorehtically unless there is a mass ejection wave none of the planets should get swallowed so much as shoved out as their orbitale trough moves.