[time-nuts] Absolute time accuracy pre-Cesium?

[Steve Allen]

On Mon 2019-03-25T16:54:28-0700 Tom Van Baak hath writ:
> In retrospect we would have had fewer leap seconds if they had
> chosen 9192631950 Hz instead of 9192631770 Hz.  But at the time it
> wasn't a choice; it was just a measurement.

And it was a measurement which was performed during an interval when
everyone was surprised by the data they were seeing.  Around the
beginning of 1957 the rotation of the earth's crust shifted suddenly
as seen in the USNO plot of UT2 at the bottom of
https://www.ucolick.org/~sla/leapsecs/amsci.html

At the time that the paper giving 9192631770 was published nobody was
sure whether this was an actual change in the earth or some failure to
understand cesium frequency standards.  It was a few years before it
had become clear that earth rotation has a power spectrum of random
fluctuations.

Over time the BIH had the opportunity to watch cesium vs.  Ephemeris
Time for more years than the original papers.  In 1964 Anna Stoyko
found a value of the cesium frequency 9192631799 Hz w.r.t.  Ephemeris
Time  (Bulletin Horaire ser 6 no 7 p 186).

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