Re: Would a velocity opposite to earth's velocity be absolute rest?

There is no such thing as "absolute rest" in the Special Theory of 
Relativity.  All motion can only be defined RELATIVE to some reference 
frame, and there is no way to determine or specify absolute motion.  The 
rate of time can only be compared between two different reference frames.  
There is no single frame where you could say time passes "at the fastest 
rate possible".

If a space ship were moving at high constant velocity (in any direction) 
with respect to the Earth,  a person on Earth would observe that a clock 
on the ship was ticking slower than one on Earth.  But, a person on the 
ship would observe that a clock on Earth was ticking slower than one on 
the ship.  The slowing of each moving clock, compared to the clock at 
rest, follows from application of the Lorentz Transformation equations.  
This makes perfect sense in Special Relativity, where there can be no 
preferred frame.  It could seem confusing to someone who has learnt too 
much classical physics, without studying the consistency of relative 
motion.