[time-nuts] Why 9,192,631,770 ??
jfor at quikus.com
Fri May 11 18:53:17 UTC 2012
IMO, that would be a disaster for all areas of physics and engineering,
except for possibly some aspects of astronomy.
When they 'redefined' the Volt some years ago it was a goat rodeo.
> So what you are saying is every 30 years select a new leap CS reference.
> Dispense with everything in between.
> On Fri, May 11, 2012 at 2:21 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
>> > Are there better estimates of the ET second nowadays (relative to the
>> > SI second)? It would be interesting to know what the cesium frequency
>> > "should have been" if much better estimates of the ephemeris-time
>> > second were available at the time.
>> Hi Peter,
>> Everyone should take ten seconds and look at this animated GIF:
>> It shows what would have happened to "earth time" vs. "atomic time" if
>> cesium frequency had been defined to be other than 9192.631770 MHz. As
>> you can see a slightly higher number would have meant less deviation
>> between the two timescales.
>> However it should also be clear, even with this short 40-year plot, that
>> no number is the best or correct or right choice. It all depends on
>> year(s) you choose to base your earth rotation rate calibration on (the
>> astronomers doing the calibration in the 1950's selected the year 1900
>> their baseline).
>> To see each page at your own pace here is it as a multi-page PDF file:
>> If you wanted a near perfect match between atomic time and the rotation
>> the earth during the 1970's hindsight tells you the frequency should
>> been 9192.632080 MHz. Similarly if your crystal ball said to use
>> 9192.632010 you would have been very close for three decades. If you
>> wanted the best time accuracy from the year 1972 to present you should
>> picked 9192.631950.
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