Re: [time-nuts] The future of UTC
Antonio, and other posters, The issue of leap seconds is covered in the LEAPSECS mailing list rather than time-nuts. You can find the archives at: http://six.pairlist.net/mailman/listinfo/leapsecs Please move your well thought out questions or comments to that list. Thanks, /tvb ___ 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.
Re: [time-nuts] Japan Quake May Have Shortened Earth Days, Moved Axis
1E14 we might be able to notice Hal, No. Look at the adev of the earth (earlier posting). The length of earth day varies in the *milli*second range, day to day. VLBI measurements are under 0.1 millisecond, which comes to about 1e-9 resolution. Realize that none of the NASA earthquake may have shortened press releases are about real measurements of rotation. They are just impressive models of changes in momentum. The predictions are in the *micro*second range. The press does not always distinguish between milli and micro. /tvb ___ 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.
Re: [time-nuts] Primary Time Standards
Absolutely, but you can still pull a new Cs out of the box and it will run at the same frequency as your old Cs. Not quite the same. This is called the re-trace spec which is poorer than the stability spec. Vintage Cs standards like the 5060 or 5061 powered up within about 1e-10 or 1e-11. The 5071A retrace spec (called reproducibility in the data sheet) is 1e-13. /tvb ___ 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.
Re: [time-nuts] Primary Time Standards
A primary frequency standard is one that faithfully implements the definition of the SI second. Thus primary standards are based on Cs. But not all Cs-based clocks are primary. CSAC, for example, is not a primary standard. Rubidium, hydrogen, quartz, or pendulum clocks are not primary. The definition spells out zero magnetic field, zero temperature (zero velocity), and zero altitude on the earth's rotating geoid. There are many other practical physics details that need to be addressed. For a good example of what it takes to make a Cs clock a primary standard see: http://tf.nist.gov/general/pdf/1497.pdf http://tf.nist.gov/general/pdf/1846.pdf So strictly speaking no Cs clock actually runs at exactly 9192.631770 MHz since you need a certain amount of magnetic field to isolate the hyperfine transition, you can't run at absolute zero, no labs are actually at sea level, and atoms are not simple toys, etc. A lot of work is required to identify, predict, and quantify a host of factors. Again, please read or glance at those papers to appreciate the work that national metrology labs do to make copies of the SI second for their country. Some day the definition of the SI second will change; optical clocks offer much greater promise than microwave clocks. Note the length of a second won't change, it's just that the definition of a second will be more precise. /tvb ___ 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.
[time-nuts] NERC TEC test postponed
I've been told the NERC has decided to postpone their July 14 TEC-elimination test. Sorry I don't have a URL with more information. Those of you logging 60 Hz data should continue. As you know from my web site, measuring any sort of time/freq source is interesting. If nothing else you will have a longer baseline when/if the test is rescheduled. /tvb ___ 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.
Re: [time-nuts] The future of UTC
Mark, If the planet were not inclined 23 degrees this might make sense. But it turns out daylight times differ by latitude and season and hemisphere. So it is not surprising that nations, or even states within large nations, assume the right to set their own rules of local time. /tvb On Jul 15, 2011, at 9:50 AM, Mark Spencer mspencer12...@yahoo.ca wrote: Sorry for the prior email with no text. If the world could agree on the dates when DST adjustments are applied (if individual countries, states etc elect to make DST adjustments) and make any needed leap second adjustments at the same time that would be a positive step IMHO. ___ 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.
Re: [time-nuts] Japan Quake May Have Shortened Earth Days, Moved Axis
So what is the Allan deviation of the earth spinning? :) http://www.leapsecond.com/museum/earth/ /tvb ___ 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.
