quote:Original post by Eelco

quote:
Actually there''s lots of rarified gas floating around up there. Not enough to breathe certainly, but, unless you''re in deep, deep space, you''re certainly not in a vacuum. So sure there''s resistance. It''s very small, but it''s there.

however much ''air'' there is in space, it orbits along with the planets anyway, otherwise it would have fallen into the sun long since .

That''s very true. Since everything in the solar system orbits in the same direction, it must be orbiting with us.

Anyway, Geoff''s explanation is excellent.

Just set the centripetal force equal to the gravitational force.

And if you''re still confused about the planets falling into the sun, think about this: When you spin a ball tied to a string around your head, is there some sort of magic "acceleration that is constantly applied at a perpendicular angle to the direction to the sun" (in your own words) being applied here? No - the only thing keeping that ball moving in a circle around your head is the force of you pulling inward on the string. (Although in reality your hand is swirling about, moving the center of rotation around, but don''t worry about that)

Things are in orbit because they are falling towards the sun. They end up falling around the sun because they are moving so fast in a perpendicular direction. Same thing with any kind of orbit.

Do not forget that we are also being pulled OUT of the solar system by the mass of the rest of the matter out there. (I don''t want to get into String theory and its 10 dementions, *11 for W, or wast it M theory* and stuff,...)

But yeah, in our life time, planets are basically stable, in the suns lifetime, No, we''re wobbling like drunks on speed.

They don''t pull MORE than the sun, but they still PULL the planets, as well as the sun itself. If you want to try and model our solar system as close as possible, you have to add in ALL the forces you can think of. A speck of dust trillions of lightyears a way still acts on our planet enough to change its movement. Just not enought that we could give a damn before the sun burns out, but it still pulls.

Thats all part of TT, (Time Theory) and why we can never change time/time travle, as time is based off every smallest bit of whatever wherever it is, so if you change something, you eventually change ALL of the history from that point, and in the past. (Time is best seen as poly directional, even if we only view it as mono directional)