[time-nuts] Primary Standards...

[Mike S]

At 06:25 PM 2/23/2010, David C. Partridge wrote...
>No they cannot be - yet.  At the point where (e.g.) the second is 
>re-defined
>in terms of the aluminium quantum clock, then the aluminium quantum 
>clocks
>are then by definition the primary standards of time, and all the Cs 
>clocks
>are now secondary standards as the second is no longer defined in 
>terms of
>the Cs beam clock.

I disagree. A Cs clock is not a primary because it uses Cs, but because 
it's the pragmatic state-of-the-art. A Cs clock which determines time 
based on the definition simply doesn't exist, it meets only 1 of 3 
criteria. If a demonstrably more stable clock, using any technology, 
can be shown to exist, it too qualifies as a primary standard. Better 
is better.