Re: If you are in an airplane flying 700 mph.

You would gain no time by flying in any direction relative to the earth's 
direction of spin.

I'm assuming you are neglecting wind as well, because if you were not, the 
plane (in the mid-latitudes of the northern hemisphere) would actually gain 
time going the same way as the earth's rotation, because of the tailwind.

Anyway, the reason behind this is simple...the plane does not move without 
regard to the earth.  For argument's sake we'll say that the earth spins at 
1000 mph.  This isn't by any means exact, but there is no need to make the 
numbers difficult in this case.  You are standing on a motionless object 
situated outside the atmosphere directly above the North Pole.  If the 
plane was flying east-west (opposite the direction of spin), the plane 
would appear as if it were flying backward at 300 mph.  If it were flying 
the other way, it would look like it was going 1700 mph frontward.

However, this is completely outside the frame of reference.  What it comes 
down to is that if you are moving, and someone else is sitting still, they 
appear to be moving to you.  You could tell them they're moving, and they 
would not be able to prove you incorrect.  Interesting how general 
relativity works.

Hmm, I got off on a tangent there. =)  Anyway, no, you would gain no ground 
by flying in the opposite direction of the earth's spin.  Short reasoning 
here is that the plane moves with the earth because the air moves with the 
earth as well.  The plane must deal with the atmosphere, and therefore 
gains no ground.

Justin Miller
gemiller@bellaltlantic.net