If I drive away in a car, you'll say I'm accelerating. But then I tell you that relative to me, you're accelerating in the opposite direction.
That's wrong. Acceleration can be measured, speed can't. So you can say very explicitly who is accelerating and who isn't. That's the definition of inertial system: coordinate frame and velocity is given, NO acceleration or whatsoever. Thus, the person who stays behind is always in the same inertial system, while you (the traveler) changes them by accelerating.
space shuttle clocks need adjusting not because of the movement but because of the fact that time moves slower in space. and while this has something todo with movement, its not the movement of the clock, but of the earth.
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HOWEVER if you love on a planet bigger than earth, you age faster...
That has nothing to do with the velocity but with gravity and is again an effect of general relativity. "Time moves slower in space" is not correct (where did you get that from?). It doesn't matter if I'm in space or not, what matters is the curvature of the fourdimensional manifold - and now again we're getting too detailed for this forum. Sorry.
one ages slower in space. in fact, if you COULD travel at near light speed for ten years away from earth and then return for another ten years, you aged 20 years while on earth roughly 400 years passed (or something).
That's the problem we're discussing. It has nothing to do with speed itself, though (see our discussion).
Read Error's answer, it is quite a good one I think ^^.
@Alberto: It's true what you say but I don't get if you're trying to resolve the problem, you're merely restating it - or did I miss something?
