[time-nuts] Re: The SI second and the ease of realization (was: leap seconds finally being retired?)

[Hal Murray]

Thanks to Magnus and Attila for a wonderful discussion.

Attila Kinali said:
> I would like to add here, that we already have this problem. If you look at
> the current list of primary standards contributing to TAI https://
> webtai.bipm.org/database/show_psfs.html you see that it's only a few labs.
> And it was just SYRTE, PTB, NIST and INRIM 20 years ago. Also note the huge
> gaps most of the primary standards have. I.e. very few are run once a month,
> much less continuous. And this is a technology that's quite mature and well
> understood.[1] 

I'm missing a key step.  If the primary standards are only run once a month, 
how can they contribute to TAI?

I'm guessing that they are used to calibrate non-primary standards AND that 
the non-primary standards are known to drift slowly relative to how often the 
primary standards are run.

Does that mean that back in the early days of primary standards, they were run 
for long-enough to get good data on the non-primary standards?

Crystals are known to have jumps.  Do boxes based on atomic properties also 
jump?


> Yes, this means that any time-nut with a GPS disciplined Rb gets to within
> 1-2 orders of magnitude of an average NMI. And yes, I find this incredible! 

+1  :)


> Sure, there is no legal traceability for a time-nuts lab, but who needs that
> anyways?

Is there legal traceability to GPS?  I thought somebody offcial (in a legal 
sense) published the offset between GPS and UTC.

I guess my real question is what does "legal traceability" mean to the US 
court system?

In the stock markets there are rules I don't understand involving time.  I 
think the typical computers involved get their time via NTP from a GPS box.  
These days, they probably use PTP to shave a bit on the error bars.





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