[LEAPSECS] drift of TAI

[Steve Allen]

On Sat 2008-09-13T13:26:07 +0100, Zefram hath writ:

> After a mere four millennia at the current

> rate of drift, TT(TAI) will not be accurate to the precision implied by

> its defining equation: once the accumulated drift has exceeded 500 us,

> TT will be better approximated by TT ~ TAI + 32.185 s.        It's only a

> matter of time before noon TT coincides with midnight TT(TAI)!


I noted when preparing my Delta T plots that the 1.e-12
change in the rate of TAI on 1977-01-01 amounts to a difference
of 0.1 s at the earliest point on my plots, or less than 0.25 s at
the earliest written records of humans.
I can't imagine any astronomical observation which, even if
described in totally unambiguous language, could make the distinction.
I expect that at the time the astronomers who were unconcerned with
the rate change of TAI had a similar viewpoint.

Looking the other way, I still take a lesson from the agencies which
launch payloads intended for rendevous.  Their countdowns have always
accepted the notion of a discontinuous "hold" in the time scale
leading to a future event.

--
Steve Allen                 <sla at ucolick.org>                   WGS-84 (GPS)
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