[time-nuts] ARRL FMT results

[Tom Van Baak]

> 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?
> 
> Warner

Ah, you may be on to something here. Someone
else on the list may know for sure, but let me
think out loud with you.

Yes, the Sagnac effect is often lumped together
with relativistic effects, but strictly speaking, it's
more of a time synchronization problem than a
feature of SR or GR (time dilation, redshift, etc).

On the rotating earth, at the equator, it amounts
to about 200 ns for a round-the-world clock trip
(40 000 km); or 5 ps/km. It depends on latitude
and such but it is independent of the speed or
duration of the trip.

Now a frequency shift is phase change over time.
Unless the receiver and transmitter move during
the experiment, it seems to me, there's no phase
change over time and so the Sagnac effect will
have no impact on a frequency measurement.

/tvb