Bulletin Horaire in 1955

At and after the General Assembly of the IAU

The 1950s were a decade of tremendous change for astronomy and physics. Among those changes was a complete reorganization of the way that time and date were measured.

The Transactions of the IAU B from the 1955 GA in Dublin contain one view of the meetings about time. Another view of those meetings and their consequences was published in Bulletin Horaire, the journal of the Bureau International de l'Heure (BIH, the International Time Bureau). The BIH was tasked with measuring the differences between the times provided by different national agencies and observatories all around the world. These other views written Nicolas Stoyko, head of the services at BIH, whose wife Anna was also part of the staff at BIH who measured and calculated and produced the publications.

Issues of Bulletin Horaire are not widely available. Below are PDF files created from scans of several important issues. Of particular note, these are the places which directed that Universal Time (UT) should be divided into UT0, UT1, and UT2, and issue number 4 is the first place where those new terms were used.

This meeting and the change it demanded were the point at which the duration of the second became disconnected with the duration of the day. This meeting demanded immediate changes that produced the disconnect, but the participants did not discuss nor explain the broader implications of having a definition for the second that was unrelated to the definition of a day. At a subsequent IAU meeting in 1964 they attempted to clarify the confusion between the two with this explanatory note on time. A few years later the astronomers were excluded from the discussion, and the physicists and radio scientists decided that leap seconds were the best solution to the dilemma.

Bulletin Horaire, series 4, number 3, 1955 May/June

This issue was published for the tabulations of times during May and June, but it begins with a synopsis of the meetings of IAU Commission 31 (Time) at the General Assembly in Dublin during August/September. It has the resolutions adopted by the IAU from both the 1952 meeting and the 1955 meeting.

The resolutions adopted at the 1955 GA required drastic changes in the operations at each of the international time services, latitude services, and radio broadcast time signal services. It appears as if N. Stoyko was on the edge of incredulity when the astronomers directed that these changes should be in place on 1956 January 1, less than 4 months after adoption.

The text includes the names and aims of the astronomers, physicists, and radio scientists at the sessions of Comm. 31. It shows the tensions between various factions. At no point do the participants give a clear explanation of the implications of having two different kinds of seconds in two different time scales.

original French text as BHs4n3.pdf

English translation as BHs4n3EN.pdf

Bulletin Horaire, series 4, number 4, 1955 July/August

This issue was published for the tabulations of times during July and August, but it begins with a synopsis of the changes to the radio broadcasts of time signals and the changes to the tabulations of the differences of times measured from all sites which were to have gone into effect on 1956 January 1.

This has the original definitions and first use of the terms UT0, UT1, and UT2. It makes it clear that beginning with 1956 all broadcast time signals were intended to be providing UT2, and all tabulations of time differences would be expressed in UT2.

original French text as BHs4n4.pdf

English translation as BHs4n4EN.pdf

Steve Allen <sla@ucolick.org>
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