On 2010-02-10, Richard B. Gilbert <[email protected]> wrote: > unruh wrote: >> On 2010-02-10, David J Taylor >> <david-tay...@blueyonder.delete-this-bit.and-this-part.co.uk.invalid> wrote: >>> "David Woolley" <[email protected]> wrote in message >>> news:[email protected]... >>>> David J Taylor wrote: >>>> >>>>> I remember the flying of caesium or other atomic clocks round the >>>>> world, and that folks had to invoke relativistic corrections. Were >>>>> these better than microseconds as well? >>>> That's called Navstar (GPS) and GPS position solutions do have to >>>> include a general relativity correction to the satellite clocks. >>> Not today's GPS, but some forty or more years ago: >>> >>> http://www.hp.com/hpinfo/abouthp/histnfacts/timeline/hist_60s.html >>> >>> 1964: >>> >>> "The highly accurate HP 5060A cesium-beam atomic clocks gain worldwide >>> recognition as the "flying clocks" when they are flown from Palo Alto to >>> Switzerland to compare time as maintained by the U.S. Naval Observatory in >>> Washington, D.C. to time at the Swiss Observatory in Neuchatel. The atomic >>> clock was designed to maintain accuracy for 3000 years with only one >>> second of error. The cesium-beam standard becomes the standard for >>> international time." >>> >>> I had wondered what accuracy was obtained - i.e. how far was each nation >>> out - and whether relativistic corrections had been needed for these >>> "flying clock" tests. >> >> 1 sec/3000years is 1 part in 10^-11. The gravitational redshift is >> gh/c^2 (g is gravity acceln on earth, h the height of the flight, and c >> vel of light) which is 10^-12 -- ie below ( but not by much) the >> accuracy of the clock. The velocity correction is 1/2 v^2/c^2 which is >> again about 1 part in 10^12. Ie, both corrections are smaller (but not >> much) than the uncertainty in the clock rate. If the plane flew at Mach >> 2, rather than well below Mach 1, you could get that velocity correction >> up the accuracy and one would have to take special relativity into >> account. >> >> >> Since the flight probably lasted say 10 hr, which is 100000 sec, th > > BUZZ!!!!!!!! > > Ten hours is HOW MANY seconds? > > I make that as 10*60*60 which is 36,000!
You are right which makes the relativistic corrections even smaller. > ><snip> _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
