Someone asked what a frequency time standard cam calibrate besides a clock. Gravity is, or was, measured by throwing a corner cube into the air (vacuum) and using a laser interferometer, timing its acceleration as it fell back. All of that can be calibrated from a frequency standard, so unlike volts and things gravity is one variable that frequency/time can be used to define. Although I dont think you will find a frequency/gravity transducer on fleabay. cheers, Neville Michie
On 03/12/2008, at 3:56 PM, Jim Palfreyman wrote: > 2008/11/29 Mike S <[EMAIL PROTECTED]> > >> At 01:30 AM 11/29/2008, Tom Van Baak wrote... >>> Note also that clocks at NIST run about 1.8e-13 fast due to the high >>> elevation of Boulder, CO (general relativity), which is yet another >>> factor that has to be corrected for compared to the official sea- >>> level >>> definition of the second. >> >> Do they really adjust to sea level on earth? That isn't part of the >> definition. Within that convention, as the mean sea level rises >> (~20 cm >> in the last 100 years), does the length of the second change >> (relatively)? >> >> A clock will run faster the lower the strength of the >> gravitational field. > Even though the mean sea level might rise 20cm in 100 years, it > doesn't mean > the gravitational field is changing in any meaningful way in that > time. > Daily tidal variations would be far greater. > > One would assume the definition of the second is in reference to the > gravitational field at the surface of the mean geoid and has > nothing to do > with sea level. > > Jim > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
