[LEAPSECS] [Non-DoD Source] D.H. Sadler in 1954

Fri Mar 16 12:16:23 EDT 2018

I was surprised to find phrases in the Lick web pages:  "CCIR ignored the advice that astronomers " and "squelched astronomers who insisted that leap seconds would cause trouble".   

I realize their author is not the only person with a strong emotional bias, but even so I question the tone of these web pages because they are inconsistent with the following:

1. There was a progression in thought as technology advanced and atomic clocks proved their reliability.

2. It should be obvious that ephemeris time would need a flywheel system to get practical time to the users, and GMT could be part of that.  Today individual labs realize UTC(k) for the same reason - to flywheel before the monthly computations of UTC are published.  WWVB, GPS, and your local cell towers are all part of the system as well.  (Even so, I think everyone today agrees that Ephemeris time was a mistake.)

3.  According to references in Nelson et al’s Metrologia article, which was peer-reviewed, it looks to me like the switch to UTC was by universal agreement among the institutions.  The IAU, URSI, CIPM(=CGPM), and CCIR(= ITU) all agreed to the current system in the late 60's, and I would guess that the timing of their resolutions probably depended more on the (generally) 3-year spacing of their general assemblies than anything else.  Note that many of those groups had overlapping membership.  It would however be unusual if all individual members of these bodies ever agreed to any resolution, even if passed "by consensus".

For more trivia, the dynamic  Gernot Winkler of the USNO was both a practical clock man and astronomer.  He was not the only one, and he was a very active member of the IAU who chaired commissions, served on working groups, etc.  He told me personally that he and Essen independently came up with the idea of leap seconds.   He also said a big reason was to win the support of the mariners, who in the pre-GNSS days actually did celestial navigation and who in the pre-internet days could not easily get access to tables that incorporated the difference between UT1 and UTC.

________________________________________
From: LEAPSECS [leapsecs-bounces at leapsecond.com] on behalf of Steve Allen [sla at ucolick.org]
Sent: Wednesday, March 14, 2018 12:16 AM
To: Leap Second Discussion List
Subject: [Non-DoD Source] [LEAPSECS] D.H. Sadler in 1954

In 1954 D.H. Sadler produced a monograph on the changes in time
that had been resolved at the 1952 IAU General Assembly.
His writeup is clearer than almost anything else for the next 60 years.
It was published in Occasional Notices of the RAS, and it has been hard
to find until now.
https://www.ucolick.org/~sla/leapsecs/twokindsoftime.html
This is one of the series of documents produced starting in 1948 and
proceeding through the next 20 years where astronomers explained that
two kinds of time would be needed to satisfy all applications.

--
Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street               Voice: +1 831 459 3046         Lng -122.06015
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