[time-nuts] 15 Seconds error...??

[Mike S]

On 1/18/2012 5:26 PM, Tom Van Baak wrote:
> The issue, I suspect, is that "TAI" still, mostly, in print and in
> people's minds, refers to the abstract paper clock, maintained
> by the BIPM, rather than some physical realization.
>
> For physical realizations we have all the UTC(k) clocks, one or
> sometimes more than one per country.

Well, yes and no. From the perspective of being real-time exact, even 
the UTC(k) clocks are only good for those with direct access, and even 
that is debatable, since any measurement is subject to propagation 
delay. (which may be variable at some scale, and there's phase noise, 
and now we're picking nits)

I think the proper comparison is between UTC and TAI, as they are 
available to average users in real time. Aren't they the same, except 
for how they're enumerated? i.e. don't they differ only in the number of 
integer seconds they are apart? Aren't both based on the same ensemble 
of atomic clocks, and aren't both only really only known "after the 
fact," when comparisons and calculations have been made?

So, I'd still like to know who says "don't use TAI," and for what reason.