Hard to exploit, but precious data

 

That is why Antoine Gaubil and his co-workers, while producing the list of the solar eclipses mentioned in the canonical texts, felt the need to relate to the sexagenary cycles of the tradition : for example, 16th August 1723, was equivalent to the year denoted by the "Tien Mao" Stem-Branch of the 74th cycle. [1] This ability to use both calendars made them able to "check the reality of eclipses", as Gaubil wrote to Father Souciet. In a letter of 20th October 1723, he shared his satisfaction with his penpal after this check : "Concerning eclipses, you will be pleased to learn that F. Adam Schall once calculated and checked the one of Tchonkam, in 2155 B.C. His calculation can be seen in a book called kin kiao-tche kao antiquarum novarum conjunctionum ecliplicarum Examen. This eclipse has newly been checked and calculated again by R. R. F. F. Slavisek and Kegler, from Germany. Thus, even if my own calculation was worthless, the others are too skilled to make a mistake in this area." [2]

However, for these calculations to get any value, the scientists had to make sure that the Chinese chronology was valid.  At that time, it wasn't obvious. In a Mémoire read at the Academy of Saint Petersburg in 1728, Delisle bitterly observed that "until now the astronomical facts found in Chinese books could not be used in astronomy". If some of them were simply "not detailed enough" to be usable, a more structural weakness also made them hard to exploit : "they are vitiated by the uncertainty of Chinese chronology."

This last problem was a double one. On the theological side, first, Chinese chronology competed with the biblical tradition, and risked contradicting or predating it. With a noticeable rigour, Nicolas Fréret tried a documented analysis of its "antiquity and certainty", according to the title of a series of presentations given at the Academy in 1733, complemented by Clarifications, in 1739. For instance, he went against the idea that the Spring and Autumn Annals were nothing but "the remnants of an ancient prophetic book of Enoch, disfigured by Confucius". [3] From a scientific point of view, Cassini himself, in his Reflections on Chinese chronology, had cast some doubts on it. In Cassini's mind, "one cannot get out of the embarrassment" caused by the "confusion" resulting from the mistaken intercalation of additional months in the Chinese years, or, on the contrary, from the forgotten necessary intercalations. Given the favour gained by the Jesuits in Beijing's court, Cassini concluded that the Chinese themselves "aknowledeged that they are unable" to "adjust by themselves without major mistakes" the cycles of their years. [4] Father Gaubil was mindful of these arguments and stated that he was "convinced that Chinese history, chronology, and astronomy were in need of a critical examination", and added : "that's what I have tried to enable myself to do." [5]

 

De l’Antiquité et de la Certitude de la chronologie chinoise

De l'antiquité et de la certitude de la chronologie chinoise, by Nicolas Fréret

 

If we wanted to judge from afar and by its fruits the research program sketched by Father Gaubil, we could revisit a fact reported by Jean-Pierre Luminet and Jean-Marc Bonnet-Bidaud. [6] When, in 1921, two American scientists, Carl Lampland and John Charles Duncan, noticed that the Crab Nebula expanded, the explanation was given by classical China : as Edwin Hubble showed (following an intuition of the Swedish Knut Lundmark), this nebula, with a pulsar in its heart, was nothing but the visible trace of the explosion of a "guest star" (ke xing, 客星) observed on 4th July 1054 (a ji-chou day, according to the sexagenary cycle) by Yang Weide, chief astronomer of the imperial observatory of Kaifeng. Without this observation, no doubt that our understanding of novae and supernovae wouldn't be the same. [7]

 

Observations des satellites de Jupiter depuis la Maison des jésuites français à Pékin

observations of Jupiter's satellites by Father Gaubil in Beijing for the year 1727

 

 

But ancient astronomy was not the only topic the Jesuits focused on. Gaubil regularly sent his own observations to Father Souciet, and they were collected in Delisle's portfolios. His correspondence with the latter also included several observations of eclipses. From 1725 to 1757, Father Gaubil's observations were mainly about satellites, especially Jupiter's ones, and eclipses (around ten lunar eclipses and four solar ones). He also recorded Mars passing through the Beehive Cluster, one of the comets of 1748, and the transit of Mercury on 7th November 1756.

Carte générale des constellations chinoises en deux hémisphères avec la trajectoire de la comète de 1723

On this map of the constellations, Father Ignace Kögler has included the trajectory of the comet of 1723. Delisle added the comet of march 1742's one.

 

 


[1] Observations mathématiques, Astronomiques, Géographiques, Chronologiques et Physiques, tirées des anciens livres chinois ou faites nouvellement aux Indes et à la Chine, par les Pères de la Compagnie de Jésus, rédigées et publiées par le P. É. Souciet de la même Compagnie, Paris, Rollin, 1729-1732, vol. 1, p. 28.

[2] Letter of October 20th, 1723, to F. E. Souciet, Correspondance de Pékinop. cit., p. 62.

[3] Quoted by Danielle Elisseeff, Nicolas Fréret (1668-1749). Réflexions d'un humaniste du XVIIIe siècle sur la Chine, Paris, Collège de France, 1981, p. 81. 

[4] Réflexions sur la chronologie chinoise par Monsieur Cassini, colllected in Du Royaume de Siam by Simon La Loubère, Paris, 1691, t.2, p. 379 sq.

[5] Correspondance de Pékin, p. 226. Gaubil's Taité de la chronologie chinoise was published after his death, in 1814 (ibid., preface, p. VIII). For a discussion on the reliability of Chinese astronomy, see Joseph Needham et al., Science and Civilisation in China, vol. 3, p. 417 sq.

[6] Jean-Pierre Luminet : https://blogs.futura-sciences.com/luminet/2015/10/12/la-nebuleuse-du-crabe-hier-et-aujourdhui ; Jean-Marc Bonnet-Bidaud, 4000 ans d’astronomie chinoise…op. cit., chap. 8, p. 119 – 134.

[7] A pulsar, for "pulsating star", is "a tiny dense and very compact star  – of a radius of 20 km only for a mass equivalent to the Sun's one – turning like a frenetic spinning-top with a speed of 30 turns per second, which constitutes the remains of an exploded star." (J.-M. Bonnet-Bidaud, ibid., p. 124-125.) The Crab Nebula happened to be the first object of the catalog produced by Charles Messier at the Hôtel de Cluny.