[time-nuts] ARRL FMT results

[M. Warner Losh]

In message: <20070104221914.05232BE00 at ip-64-139-1-69.sjc.megapath.net>
            Hal Murray <hmurray at megapathdsl.net> writes:
: 
: > But there's a finite amount of time between when the signal is
: > transmitted and when it is received.  During this time, the earth
: > rotates, thus bringing the receiver either closer to or farther away
: > from the transmitter.  Doesn't that cause a frequency shift?  Isn't
: > this the Sagniac effect?  Small, but measurable as it is a
: > relativistic effect, no? 
: 
: Is that a frequency shift or a phase shift?
: 
: The transmitter is moving at the same speed as the receiver.  That motion 
: changes the transit time between the pair, but if the velocity is constant, 
: that makes a time/phase offset rather than a frequency offset.  Do get a 
: frequency offset you want a Doppler where one end is moving relative to the 
: other.

Right.  I talked to the guys here that are doing two way satellite
time transfer work.  The reason we had to have a Sagnac term in that
work wasn't because the earth was rotating, but because the platform
could be moving, including the satellite...

When both Rx and Tx are stationary, they both move the same amount as
the earth spins, which is why there'd be no effect.  If Rx or Tx is
moving, then the Sagnac and Doppler terms come into play.

I wasn't, like phk hinted, thinking that there were different drags in
the aether depending on the direction one goes.  The Michelson-Morely
experiments in 1887 showed that wasn't the case...  One of the more
interesting 'failures' in the history of science.

Warner