On 4/12/2016 3:16 PM, Michael Wouters wrote:
evaluations (for accuracy) to finally get its best estimate of what one second is. Each participating lab is then told what the difference between its clock and UTC is. USNO participates in UTC and keeps within tens of ns of UTC.
It might also be useful to introduce the concept of a "paper clock", as opposed to a physical clock. A paper clock is where a lab has a physical clock that is compared to UTC and they get an after the fact report that gives them a correction factor to apply to their clock. This makes a paper clock. So they can't tell you what time it is now to a high degree of accuracy, but they can tell you exactly what time it was last week. Also note that there is a division of labor between cesium clocks, which run continuously to keep time, but may not be as accurate as "big" cesium standards in terms of frequency. However, the big standards may not run 24/7 so they function as frequency standards as opposed to true clocks. There is also the whole issue of "time transfer" among all these devices. The gold standard is 2 way satellite. But the everyday method is GPS itself. Rick _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.