On 2020-02-04 21:16, Steve Allen wrote:
The first time that the 4th meeting of the CCDS happened was in 1966,
but that meeting is not found in any official record. The meeting
ended with a vote to recommend that the CGPM should adopt an SI second
based on cesium, but the circumstances of that vote were deemed so
abusive that the entire meeting was nullified. That did not stop the
rush for an atomic second. During the next year subsets of the CCDS
members gathered for discussions at other meetings. When the second
4th meeting of the CCDS was held in 1967 they did recommend the cesium
second to the CGPM.
From the standpoint of a physicist, the 1960 definition of the SI second
(based on ET and Newcomb's tables for the Sun) was extremely
impractical.
With the wide availability of Cs clocks, the atomic second was much
easier and more precisely reproducible than the SI second, so a
redefinition of the second (or at least a practical unit, as with
the recently abolished practical volt and ohm) was urgent.
On the other hand, you are certainly right that the actions of the
CCDS in 1967 appear strange: they propose to redefine the SI second,
and then go on to propose that the BIH, IAU, IUGG, URSI, and CCIR
study the problems arising from the new definition ("étudier les
problèmes soulevés par l'application des décisions prises
concernants la nouvelle définition de l'unité du temps").
Apparently, it did not even occur to them that this is bad
engineering.
The proposal of the IAU GA13 in 1967 to introduce an (unsteered)
international atomic time scale would have allowed to study the
possible problems of a redefinition of the SI second before
applying it.
Folks at the PTB took a different aim by introducing draft legislation
that the German government passed in 1969. The law made it illegal
for the German government to broadcast anything other than SI seconds,
and it would become effective in 1970. This seems to have pulled the
trigger on the CCIR process, for without some kind of quick action a
major nation would be broadcasting time signals using a different
scale than other nations.
The law on legal units in West Germany, from 1969-07-02, lists under
the title "tasks of the Physikalisch-Technische Bundesanstalt"
that the PTB has to publicize the procedures by which units without
material prototype are realized, including the units of time and
time scales, as well as the temperature unit and temperature scales.
(" hat die Verfahren bekanntzumachen, nach denen nicht verkörperte
Einheiten, einschließlich der Zeiteinheiten und der Zeitskalen
sowie der Temperatureinheit und Temperaturskalen, dargestellt
werden,")
This can be taken to imply the task to disseminate a standard
frequency (which they already did). But in my opinion it does not
imply that UTC must have the same rate as the atomic time scales
at the time -- the law even allows for several time scales.
I'll try to find out how the PTB was involved in this legislation
as far as time in concerned. In Germany, federal law can only
be proposed by members of parliament, and by federal and state
governments; but the PTB was certainly heard during the legislative
process.
In my home state of California the process that led to UTC with leap
seconds would have been illegal under the Brown Act that requires
public access to meetings. But in the full context that is not the
most criminal aspect of the process that led to the 1970 CCIR
decision.
Yes, and the ITU-R deliberations before the WRC in 2015 were not
transparent either. Nevertheless, past decisions of the CCIR and
the IAU have become accessible nowadays.
Let's hope that the CIPM treats any future discussions about
a redefinition of UTC in an open manner, and that it adheres
to rational design and decision processes. The recent revision
of the SI has been largely transparent and guided by good practices.
Michael Deckers.
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