Roger Louis Billard 1922-2000




Roger Billard’s investigations into Indian astronomy marked a radical advance in our understanding of that long tradition. For so long people had assumed that there had been no serious observations underpinning the parameters in the numerous texts, this in spite of the fact that for so many centuries perfectly competent calendars had been calculated according to one or another of the various canonical texts.


Billard, an only child, was born in Puteaux, in the outskirts of Paris, in 1922, Aug 29, in modest circumstances. His father was a seaman, but when he was seven his parents became concierges at 36 rue de Naples (Paris 8e). His early upbringing was Catholic, but in adult years he abandoned this in favour of a broad secular humanism. An active interest in astrology, even at the early age of 11, was a sign of his eventual commitment, and before long his orientalist interests also were being defined, with visits to the Musée Guimet, and notably by the sale of his bicycle to buy a Sanskrit dictionary,


However his youthful ambition was frustrated in German-occupied Paris. He was aged 18 at the start of the occupation, and in order to evade the forced labour which was the fate of so many young Frenchmen at that time, his parents kept him out of sight in the attic of the building. He was therefore unable to complete the normal secondary schooling.


Immediately after the war, however, he entered the École des Langues Orientales Vivantes in Paris, with the assistance of the sinologist Paul Pelliot, in spite of his lacking the Baccalauréat. There he obtained his only formal qualifications, diplomas in Chinese and Hindi, in 1945 and 1947, and also Certficat de licence in Sanskrit language and literature from the University of Paris, where he studied under Louis Renou.


He married Constance Ragunather, a woman of Scottish and Indian parents, in 1949, and in the following year he chanced to meet the distinguished orientalist Louis Hambis, which led to his becoming in 1952 a member of the École Française d’Extrême Orient, and to his appointment as Conservateur at the Musée Albert Sarreau in Phnom Penh, Cambodia. French archaeologists were well established there, and as a normal part of their work, had collected a great many inscriptions from the Hindu temples, written in mixed Sanskrit and Khmer. After about A.D. 600 the dates in these texts were based on the Indian calendar. These were to become a major focus of Billard’s interest. In 1956, on his return to Paris, he published the article ‘Perspectives nouvelles sur l'astronomie indienne’, announcing his principal discovery that the parameters of the mean longitudes in Āryabhaa’s canon were based on observations carried out in his own lifetime, that is around A.D. 500. This discovery was the cornerstone of all the later researches which became the subject of his book  L’Astronomie indienne.


He spent the next three years in France, and then moved to Pondicherry in South India, where he stayed from 1959 to 1962, attached there to the École Française d’Extrême Orient. After that he was back in Paris for six months, and then he returned to Pondicherry for another 4 years. He returned to France for good in 1966.

Up to this time the heavy calculations which his investigations required were made with  a Swedish desktop machine made by Odhner, similar to the better known Brunschviga, one of those mechanical aids that so many will remember from those years, when electronic calculation could only be done on a large mainframe computer. From 1966 however he was able to make use of the mainframe installed at the Collège de France. Without that support the numerical results and graphs in L’Astronomie indienne would have been impossible. That book appeared in 1971, and on its publication he was awarded the Delalande-Guérineau prize by the Académie des inscriptions et Belles-Lettres. In 1976 he was elected to the International Academy of the History of Science.


In 1979, soon after his retirement at age 55, he moved from Paris to Mennecy, a small town, 35 kms south of Paris. This was an unhappy period, not only because of the failure of the community of historians to appreciate the singular advances that he had made, but because since 1976 he no longer had the use of the computing facilities that he had enjoyed at the Collège de France. Like so many others in the 1980’s he switched to the new generation of desktop programmable calculators produced by Sharp and Hewlett-Packard. It was not until 1989 that he acquired a PC, one that he continued to use until his death, although he did not attempt to keep up with the extraordinarily rapid developments in machines and program compilers in the decade that followed, but continued to program in Basic.


The response to his work was a grave disappointment to him. He presented his first article of 1956 to Otto Neugebauer, who was initially unimpressed, but who, after some correspondance, encouraged him to write an ampler account as a book. When eventually the book L’Astronomie indienne appeared, the response came this time not from Neugebauer, but in a review by David Pingree. This was wholly negative, and only served to confirm him in his feeling that people were entirely unprepared to understand his work.


In fact he was recognized by a handful of scholars. For example, by 1977, after my own appreciation had matured, I told  B.L. van der Waerden, the distinguished mathematician and historian of astronomy, about Billard’s discoveries, and he showed at once a full and enthusiastic appreciation of its singular importance for the understanding of the history of Indian astronomy.


At the heart of this relatively straightforward scientific investigation, was the comparison between the mean longitudes of Sun, Moon and planets as calculated by modern procedures, with those calculated from a Sanskrit source. Such comparisons had been made earlier, notably by John Bentley, but without much success. Billard correctly put this failure down to the relative inaccuracy of Bentley’s astronomical calculations, and to the fact that fewer Sanskrit texts were available at that time. Both fields needed to mature further, and more especially, greater effort was needed with the extensive numerical calculations.


The results of his analysis of any individual canon were expressed graphically as a bundle of deviation curves, showing in the most dramatic instances, such as that of Āryabhaa, the tight convergence of the deviations at one date, proving that the canon was founded on very close observations at that date, with an exact reduction to mean longitudes. With other canons, such as that of the Brāhmasphuṭasiddhānta, the same approach showed that although the canon was not so well related to observations, at least it belonged to the time of the author. It was therefore not derived from Pitāmahasiddhānta contained in theViṣṇudharmottarapurāṇa, as some had supposed; that is to say, the section of that work entitled Pitāmahasiddhānta merely plagiarizes from the work of Brahmagupta. However, perhaps the discovery that was most remarkable, since it went against the tendency of the Sanskrit texts to be founded on observations at one particular date, was his demonstration that the canons documented in Lalla’s Ṣiśyadhīvṛddhidatantra were truly founded on a long time base, extending from the 6th to the 9th centuries. So it is thanks to Billard’s meticulous researches that we can now for the first time follow the development of Indian astronomy as a normal observational science.


It is true that researches of this kind, in which modern astronomical calculations are applied to Indian astronomy, have acquired a bad reputation, so many uncritical datings having been proposed. Billard’s work however shows that when both the Sanskrit scholarship and the astronomical science are sound, then results of real depth can be established. If the work has not been widely appreciated, it is to some extent because so many in the community of historians tend to lack a rigorous scientific formation, and also because so many are in thrall to the pronouncements of David Pingree. However, the book is completely self-contained, and it is open to anyone with basic programming skills to reproduce his results


In his last years he continued to develop programmes for the calculation of Indian dates, according to the many canons that he had studied. In this way he helped to interpret the dates found in hitherto unpublished Cambodian texts. These results will be published by Claude Jacques, of the École française d’Extrême-Orient, as Les sources de l’histoire du pays khmer. Symposium organisé par l’École pratique des Hautes Études (Section des sciences historiques et phlologiques) du 28 juin au 3 juillet 1993.


His health began to fail as a result of Parkinson’s disease from around 1985, although it was kept under fair control by medication. In the end he was a victim of cancer, and died on Dec 30, 2000. He is survived by his widow, his daughter Hélène, granddaughter Léa, and son-in-law Doron.


Raymond Mercier




BEFEO = Bulletin de l’École française d’Extrême-Orient.


‘Perspectives nouvelles sur l'astronomie indienne’, Artibus Asiae, xix, 3/4 (1956), pp.186 - 196.


Rapport de travail 1959-1960, LAstronomie indienne, BEFEO, tome li, 2 (1963), pp. 659 - 674.


‘Les cycles chronographiques Chinois dans les inscription Thaïs’, BEFEO, tome li, 1963, 403 - 431.


L’Astronomie indienne. Investigation des textes Sanskrits et des données numériques. Publications de l’École française d’Extrême-Orient, Volume lxxxiii, Paris, 1971.


‘L’Astronomie indienne. Résolution d’une énigme et mathémathique d’une histoire’, Revue du Palais de la Découverte. Février 1973, pp. 11 - 2.


‘L’Astronomie indienne. Résolution d’une énigme et mathémathique d’une histoire’, Sciences et techniques. Revue de l’Ingénieur. No. 6 nouvelle série 15 Sept 1973, pp 31 - 45.


Āryabhaa and Indian astronomy : an outline of an unexpected insight’, Indian Journal for the History of Science, xii (1977), 207 - 224.


‘Investigation du present karaaratna’, BEFEO, lxxv, 1986, 21 - 35.


[Previously published in Archives Internationales d’Histoire des Sciences, 52, (2002, No.149) 355-359.]

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