> 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 _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
