So if the SI second is specified at sea level, and we know from Einstein and TVB's work that going up a mountain changes a clock's period, how would the second be affected at the center of the Earth ( ignore thermal problems, this is a conceptual discussion) where the net gravity vector might conceivably zero? Or for that matter, at a Lagrange point in space? We do have some data from those locations I would think.
A second question (no pun intended) is that given the Earth's elliptical orbit around the Sun, has there been observed an effect of the change in its gravity on atomic clocks? Tom Holmes, N8ZM -----Original Message----- From: time-nuts <time-nuts-boun...@lists.febo.com> On Behalf Of Tom Van Baak Sent: Tuesday, November 20, 2018 6:31 PM To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com> Subject: Re: [time-nuts] WWV Doppler Shift > That was the first time that I had seen an xy plot of WWV versus a > stable crystal oscillator. It is even worse than I thought. I had to > look up FRK to see that it is a rubidium standard. I talked to Jim > Maxton the chief engineer of WWVB many times around 1995. An xy cycle of WWV is just 200 ns, about 80x shorter than the 16667 ns cycle of WWVB. So, yes the xy plot in the video seems to jump around a lot, but if that were WWVB it would be 80x less, barely a wiggle. Does someone have a strip chart version of that video? Or, better yet, a raw data set of WWV (or WWVB) phase over a day or week? How hard would it be to use a hands-off SDR to produce a 5 MHz WWV phase data point every second? > Ft Collins is at 5,003 ft and clocks there run fast by 1.663ยท10^-13. > (g/c^2)/meter) compared to sea level. Yes, an out-of-the-box cesium clock will be relatively fast by that amount. But NIST (and everyone else) uses UTC, which is based on the SI second, which is defined at sea level (and several other footnotes). Which is to say that a national clock or radio transmitter (such as NIST, WWV, WWVB, or DCF77, or GPS for that matter) are adjusted in frequency so they tick SI seconds, and adjusted in phase so they align with UTC. /tvb _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
