At 9:38 AM +1100 10/15/08, Neville Michie wrote: >Hi, >the GPS system obviously counts seconds, and weeks. When the solar >year develops a phase >difference of more than half a second the UTC crowd consider a leap >second, so what is the current >rotational velocity of the Earth, either WRT the Sun or the stars? In >seconds. >I could find many answers on Google but none that seemed good enough >to set your clock by. >By clock I just mean a rubidium clock that is harmonised to the GPS >system. >cheers, Neville Michie
Neville, Unfortunately, the Earth's rotation and revolution around are not as stable as the oscillations of your rubidium clock. There is no formula for leap seconds; the folks who insert or subtract the leap seconds do so using observations of the stars as a guide. You could say that leap seconds represent the noisy least-significant digit in the Earth's somewhat jerky movement. (Jerky relative to the smoothness of a rubidium clock, that is.) It would be convenient for clockmakers if they calculated the best fit to a long-term trend of the Earth's behavior and allocated leap seconds based on that fit, but alas they do not. So there is no way to build a clock today that is guaranteed to count seconds correctly in future years, short of having it receive leap second announcements twice a year and adjust its timekeeping accordingly. -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ _______________________________________________ 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.
