A century of existence: it may seem short on the time-scale of the evolution of the universe, but very consequential to that of a scientific association. The fact that the IAU may be able to celebrate such a milestone is in itself a meritorious collective achievement, for it was not obvious at the very beginning that this organization was going to last more than a decade. Drawing on the historical sociology of scientific institutions, my paper will discuss the moral economy through which the IAU – and its dated but persistent form of scientific internationalism – has stabilized and maintained its identity since its creation in 1919, under the unifying auspices of a global scientific object to be known as: Under One Sky.

International scientific institutions are preferred settings to explore prominent topics in the transnational approaches to the recent history of science. These include: the dichotomy between universalism and contextualism in the historical evolution of exact sciences; the historical transformation of the ideals of scientific internationalism; the tensions between these historically changing ideals and scientists’ national allegiances; the balance between scientific and diplomatic activities of such institutions; and the issue of how the complex ideological, socio-political roles these institutions play affected the actual evolution of science.

Inspired by these overreaching themes, the paper presents a conceptual framework for pursuing a comparative analysis of IAU and IUPAP. A bird’s-eye view of the parallel historical developments of these two unions shows that, in spite of their common origins in the highly politicized context of the post-WWI reconstruction of international cooperation, IAU and IUPAP followed diverging trajectories in many respects. It is argued that a deeper study of these differences might give important insights to properly understand the relevance of specific disciplines’ scientific needs in the way the ideals and practices of scientific internationalism were actualized through the 20th century.

The Czech astronomer František Nušl (1867–1951) was professor of mathematics, practical astronomy and geometrical optics at Prague Charles University. His scientific contribution to astronomy consisted mainly of inventing and constructing of new astronomical and geodetical instruments. Together with his friend Josef Jan Frič, founder of the Ondřejov Observatory, he developed and improved the circumzenithal telescope (1899–1903–1906–1922–1932), a portable instrument with a mercury horizon for determining the geodetic position using the Gauss method of equal altitudes. This instrument won the gold medal at the Exposition Internationale des Arts et Techniques dans la Vie Moderne in Paris in 1937. Nušl, independently of Ernst Öpik, invented the wobbling mirror for determining the velocity of meteors by visual observation, and constructed an unique guiding system for the Ondrejov astrograph etc. The organizational activities of Frantisek Nušl were considerably rich, too: He was one of the founders of the Czech Astronomical Society in 1917, in the years 1922–1948 he served as its president. From 1918 until his retirement in 1937 he was the director of the Ondrejov Observatory, 40 km south of capital city of Prague, lectured astronomy at the Prague university and held many popular lectures including regular courses in radio broadcasting. František Nušl was member of several commisions of international scientific unions; he organized the 3rd General Assembly of IUGG (International Union of Geodesy and Geophysics) in Prague 1927, and in IAU (International Astronomical Union) he was elected as Vice-President in the years 1928–1935. One can conclude that he was the main person who formed the Czech astronomy in the interwar period.

After the foundation of the International Astronomical Union (IAU), it took nearly 32 years until Germany became a national member of the IAU. This unfortunate delay was due to both international politics and discussions within Germany (e.g. about the future role of the Astronomische Gesellschaft). The first Statutes of the IAU of 1919 excluded Germany, Austria and other countries from membership for political reasons. When the IAU Statutes were revised in 1931, Germany’s membership was possible, but could not be realized because of financial problems. In the mean time, German astronomers (as individuals) were often able to attend General Assemblies of the IAU as invited participants and to work in IAU Commissions as members. After World War II, Germany became a member of the IAU in 1951, Austria in 1955. In 1962, East Germany was accepted as an additional member. The reunification of Germany in 1990 clarified this situation. Member of the IAU is now one unified Germany.

India was still a British colony when the International Astronomical Union was born in 1919. India did not have a national science academy nor a national research council at the time. The Royal Society, London, which was the adhering body of Great Britain to IAU, handled matters of the colony too. India formally joined the IAU in 1948 as an independent nation through an initiative taken by the Government of India. In 1968, the National Institute of Sciences of India (NISI) became the adhering organisation to the IAU, as did the other affiliate Unions of ICSU. Soon after, its name was changed to Indian National Science Academy (INSA).

Till the nineteen-sixties, individual Indian membership in the IAU grew rather tardily but the situation changed with the rapid growth of astronomical activities in the country. In 1967, M.K. Vainu Bappu, the then Director of the Kodaikanal Observatory, was elected a Vice-President of the Union. In 1979, he was elected the President of IAU for the triennium 1979–1982, and during the same period, V. Radhakrishnan and Govind Swarup were elected Presidents respectively of the Commisions 34 and 40. In 1985, the General Assembly of the Union was held in New Delhi. It was dedicated to the memory of Vainu Bappu who had initiated the process of inviting the Union to hold its GA in India. A few years later the Sixth Asian-Pacific Regional IAU Meeting was held in Pune. A number of IAU symposia and colloquia have also been held in the country. During the last three decades, the engagement of the Indian astronomers with IAU has increased a great deal with a large number of them taking on important official roles in the IAU. Currently, India has close to 300 individual members.

The so-called China crisis, well documented in History of the IAU by Adriaan Blaauw and in Under the Same Starry Sky: History of the IAU by Chengqi Fu and Shuhua Ye, refers to the withdrawal in 1960 of the People’s Republic of China (PRC) from the Union. The crisis stemmed from the admission by the IAU, amidst strong protest from PRC and some other member countries, of the Republic of China (ROC) to the Union, creating the so-called “Two Chinas” – or “One China, one Taiwan” problem. The crisis directly led to the absence of mainland Chinese astronomers from the stage of international collaborations and exchanges, and was only solved two decades later. The solution, accepted by all the parties involved, is that China is to have two adhering organizations, with mainland China astronomers represented by the Chinese Astronomical Society located in Nanjing (China Nanjing) and China Taiwan astronomers represented by the Academia Sinica located in Taipei (China Taipei). The denominations “China Nanjing” and “China Taipei” represent the IAU official resolution and should be used in all IAU events.

The China crisis, probably the most serious one in IAU history, was a painful lesson in the 100-year development of the Union. Yet, with its eventual solution, the Union has emerged stronger, upholding its spirit of promoting astronomical development through international collaboration of astronomers from all regions and countries, regardless of the political systems, religion, ethnicity, gender or level of astronomical development.

I have written elsewhere from a (mostly) celebratory point of view about early international astronomical projects. This version looks at some of the same projects, but from a less cheerful point of view.

Astronomy in Japan has long history and has its own “light”. The foresight of leaders in the early 20th century helped Japan to become a founding member of the International Astronomical Union. In this paper, a brief description will show the growth in its more recent history with particular emphasis on two important issues: large research facilities and women participation. On the ground or above, the large observational facilities are nowadays outside of the land of Japan, not only in terms of physical presence but also the community they serve. Domestic membership of the Astronomical Society of Japan at the same time is expanding, thanks to the increased opportunities for women. Continuing global cooperation with more diverse composition of members are the keys for sustaining the growth to carry the astronomy in Japan with IAU into the next century, and hopefully to another planet.

The South African Astronomical Observatory (SAAO), formerly known as the Royal Observatory, Cape of Good Hope, will be 200 years old in 2020. Also, South Africa (SA), formerly a British colony known as the Cape of Good Hope, will celebrate her 100-year anniversary as an International Astronomical Union (IAU) member in 2020, following the IAU centenary in 2019 that this IAU Symposium 349 celebrates. In light of all this, particularly in anticipation of the 200-year anniversary of SAAO in 2020, the SA National Research Foundation (NRF) has developed a Roadmap for the History of Astronomy in South Africa. As part of this we are conducting an oral history of astronomers to complement the historical celebrations of the institutions and science relating to astronomy in SA, supported by the SA NRF. Primarily drawing on literature and setting the scene for this work, here we present a snippet of the on-going oral histories, to glean the role of the IAU in astronomy in South Africa and show the potential of the oral histories to inform and complement written history.

Even though Italy officially joined the IAU in 1921, Italian astronomers were involved in its birth as early as 1919, when Annibale Riccò, Director of the Astrophysical Observatory of Catania, proposed to the IAU Committee to hold its first General Assembly in Rome. This contribution will analyze the role played by Italian astronomers in the development of the IAU from its foundation to the Second World War. The recent project of reordering of the astronomical historical archives in Italy permits for the first time a more in-depth study of the relations between Italian astronomers and the international scientific community.

The Arab Astronomical Society (ArAS) was officially created during the constitutional assembly held in Marrakech (Morocco) on November 30, 2016, and legally recognized on May 15, 2017. ArAS is composed of a group of Arab researchers and students in the field of astrophysics who aim to develop research in this field in the Arab world (22 countries). ArAS is working on bridging the gap between the Arab astrophysicists in the Arab world and those around the world by organizing collaborative workshops and international scientific meetings, offering scholarships and developing graduate programs in astrophysics. Presently, the Society is working on establishing personal and material scientific infrastructure in the Arab world by training advanced undergraduate and graduate students in astrophysics and stimulating the building of new telescopes on the best sites in the Arab world. This will be accomplished through the hosting of specialized schools and conferences in astrophysics, international collaborations, facilitation of students’ and post-docs’ training in international research centres and universities, the establishment of prizes in astronomy to honour leading Arab scientists in astronomy and to motivate junior researchers to present notable works in astronomy. In this work, we present the on-going ArAS activities as well as future projects. ArAS is a young but energetic organization which is welcoming collaborations and partnership with other groups.

This paper presents a brief survey on the history of radar observations of meteors in Kazan from 1950s to present days. Such achievements of Kazan researchers as development and further improvement of original measuring equipment and antenna systems, of observational data processing methods, their contribution to the theory of physics of meteor phenomena and theoretical interpretation of experimental data are highlighted. A particular progress in meteor astronomy has been achieved with a new discrete quasi-tomoghraphic method for faint meteor showers identification that uses goniometer data of meteor radio reflections detected on radar as input data. The current state and new horizons of meteor studies in Kazan are stated.

We briefly discuss the history of membership and the current position of Serbia inside the International Astronomical Union. We give an overview of astronomy education, research and public outreach in Serbia. Some statistics are presented concerning the number and gender of BSc, MSc and PhD students that graduated/obtained their degree in astronomy/astrophysics from the Department of Astronomy, Faculty of Mathematics, University of Belgrade. Due attention is paid to the most important scientific/educational institutions in Serbia in which the majority of astronomers are employed as well as various research topics investigated.

In 1918 the only Mexican institution dedicated professionally to astronomical work was the National Astronomical Observatory, which had begun operations in 1878. In that year of the 20th century, Mexico was immersed in the armed movement known as the Mexican Revolution, which strongly affected the social and economic structure of the country. The Mexican astronomers saw their group drastically reduced and their infrastructure limited; however, they made great efforts to continue their participation in the international project of the Carte du Ciel, since they were part of the 18 observatories that originally participated in it. Despite the limitations they suffered, they soon joined the group of seven nations that in 1919 formed the IAU, and two members of that observatory actively participated in the first general assembly held in Rome in May 1922.

During the last twenty years, due to the extensive help and assistance of the international scientific community, there has been a great success in the development and establishment of new well-functioning and competitive scientific groups specialized in general relativity and relativistic astrophysics in Uzbekistan (Tashkent), Kazakhstan (Astana and Almaty), Kyrgyzstan (Bishkek) and great achievements have been made on the study in Central Asia in relativistic cosmology and astrophysics of compact gravitational objects.

During its XXXth General Assembly, the International Astronomical Union (IAU) welcomed the island of Madagascar, under the Malagasy Astronomy & Space Science (MASS), as one of its new National Members. Founded in 2016, MASS is a non-profit association, a community of young professional astronomers and graduate students from Madagascar. As various organizational structures are gradually being established towards the development of Astronomy & Astrophysics in the country, the IAU has played a vital role and is still actively involved in achieving such ambitious goals.

This paper tells the story behind the succession of reforms that, for the last twenty years, progressively brought the IAU in line with the fast developments of astronomy and the public awareness of the sky worldwide. One major difficulty was how to organize the scientific activities of an exponentially growing population of astronomers, from 200 at its creation in 1919, in the aftermath of WW I, to over 13 500 a century later. The first attempts at “restructuring the IAU”, as the expression went, can be dated back to the 1988–1991 triennium. As shown by the Minutes of the successive meetings of the Executive Committee, the attempted strategy was to encourage and even propose Commission mergers, but this policy met with strong opposition, even though a need for change was felt increasingly necessary. The new approach proposed by L. Woltjer, then incoming IAU President, during the 1994 General Assembly at The Hague, was to retain the existing Commissions (along with their Working Groups) but grouping them, more or less topically, into a dozen Divisions. Putting an end to the Commission merger deadlock, this new structure was adopted very quickly, and confirmed at the following GA in Kyoto (1997). But even after this restructuring, there was little evolution of the Commissions, and in some areas the scientific classification and breakdown of the IAU activities reflected by Divisions became questionable. As a result, a new reform was undertaken in 2009, based on a more global approach, but keeping the Division/Commission/Working Group three-tier structure as the backbone of the reforming efforts. Thanks to a close collaboration between the Executive Committee and the Division Presidents, the Divisions were first redefined and approved at the Beijing GA in 2012, followed by a historic, full-fledged “Commission reset”, itself approved at the Honolulu GA in 2015. This marked the end of a structure created almost a century before, at the foundation of the IAU: the Standing Committees, precursors to the Commissions. But in response to a Call for Proposals issued by the Executive Committee, the “reset” gave birth to a whole new Commission structure, conceived by the community itself.

IAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, Standing Committee 19 became Commission 19 “Variation of Latitude”. In the beginning, the main topic of the Commission was the investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XII IAU General Assembly, the Commission was renamed “Rotation of the Earth”. The investigation of Earth orientation variations is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames and the improvement of the model of precession/nutation, have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 “Time” established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference Systems Service. Commission 19 continued to work to develop methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 “Rotation of the Earth” continuing Commission 19’s functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry, International GNSS Service, International Laser Ranging Service and International DORIS Service. During its entire history, IAU Commission 19/A2 has always worked in close cooperation with these and other related services to improve the accuracy and consistency of the Earth orientation parameters and celestial and terrestrial reference frames.

IAU Commission 41 (History of Astronomy) was founded in 1948, and between 1991 and its termination in 2015 this Commission hosted seven different Working Groups (one of which was shared with Commission 40 (Radio Astronomy). In this paper we list the objectives of these seven Working Groups and track their progress. We conclude by evaluating the role that each C41 Working Group played in furthering research on the history of astronomy.

The International Astronomical Union was conceived in 1918, and was formed one year later in Brussels. One of the 32 initial Commissions was the Committee on Stellar Photometry that later on became IAU Commission 25 Astronomical Photometry and Polarimetry, and since 2015 Commission B6 with the same name. The initial functions to be exercised by the Committee were

1. (a) to advise in the matter of notation, nomenclature, definitions, conventions, etc., and

2. (b) to plan and execute investigations requiring the cooperation of several observers or institutions.

The basic philosophy was that IAU Commission 25 was to be an advisory body, rather than a decision-making committee that imposes its regulations. This position was reconfirmed at the 10th IAU General Assembly in 1958.

From the early days on, the Commission members engaged in the teaching of the principles of photometric measurement – either via the Commission meetings and the ensuing reports, or via external means, such as lectures and publications. The topics of instruction dealt with absorption of light in the atmosphere, the modification imposed by the character of the receiving apparatus, the unequal response of different receivers to a same stimulus, and variations in the data-recorder response from one experiment to another.

From the 1930s on it was suggested that IAU Commission 25 takes responsibility in matters of standard stars, standard filters and standard calibration methods.

During the first half-century since its foundation, Commission 25 was an active forum for discussions on the basic principles of astronomical photometry, including the associated problems of transformability of magnitudes and colour indices from one instrumental configuration to another. During the second half-century of its existence, the Commission has served as a sort of news agency reporting on the developments in detector engineering, filter technology and data reduction. All along the Commission members were committed to accuracy and precision, a struggle that was primarily driven by the jumps forward in performance and sensitivity of every new detector that was introduced.

The development over one century shows that the Commission was continuously touching on the philosophy of precise measurement, where accurate measuring – for a select group of pioneers – was an end in itself.

This presentation looks back on the opinions of key players in the photometric standardisation debate, and briefly presents two case studies that illustrate the illusionary accuracy reached over a century in determining, as Commission member Ralph Allan Sampson put it, “a detail like magnitude”.