Simon Schaffer, “Authorized Prophets: Comets and Astronomers after 1759,” Studies in Eighteenth-Century Culture 17 (1987): 45-74.
Response
Before Simon Schaffer’s 1987 “Authorized Prophets: Comets and Astronomers after 1759” Clifford Lecture, the historiography held fast to the conclusion that the comet of 1759 (a Halley’s), the long-awaited and predicted return of the comet of 1682, heralded the “triumph of a single form of rational astronomy” and “mark[ed] the destruction of cometary and cosmological significance.” In fact, even more simplistically, cometary theory was supposedly completed after the 1682 comet, and its 1758-9 return simply a reassuring spectacle. Schaffer’s lecture, with its focus on Jerome Lalande and Johann Lambert, seeks to contradict both these assertions and argues that the comet of 1759 “was a resource used for profoundly differing theological, ideological and cosmological purposes.” It goes without saying that the triumphalist historiographic consensus that inspired Schaffer’s resistance was predicated on the linear-progressionist (need I say whiggish) school of the history of science about which you have had to so often hear me complain, in which Halley, in concert with Newton, got it right, and in 1682 predicted the return of that year’s comet some ~75 years later (in the story we tell the public he predicted it exactly). Lo and behold the comet reappeared when Halley said it would.
But history is always more complicated than story, as Schaffer is keen to inform us. The reappearance of Halley’s comet in 1759 did not eliminate cometary cosmic significance, and its proof of celestial mechanics was not self-evident. In fact, Schaffer, as he was so fond of doing in the 1980s, insists that the triumph of celestial mechanics through the reappearance of the comet was “a deliberate task set by workers in London and Paris,” in other words artifice made possible in the context of a certain social milieu.
Much of that work was done by Jerome Lalande. In the years immediately prior to the expected return of the 1682 comet, Lalande, along with Clairaut and Mme. Lepaute began calculating the gravitational effects of Jupiter and Saturn on the comet. They determined that these pulls would delay the comet some 20 months (they would themselves be 30 days off). Without this adjustment, the predicted return could have passed for little more than coincidence, 20 months is hardly an encouraging degree of specificity for a supposedly regular and quantifiable mechanical process. With this adjustment, however, the precision of the calculation of the expected return becomes uncanny in its precision, and, furthermore, the comet is put to work overtime to serve as an impressive demonstration of the theory of universal gravitation — acknowledging the gravitational force of all bodies of mass, in this case Jupiter and Saturn. Lalande’s calculations of cometary delay stimulated still further research. Arguing against Euler’s hypothesis of a resistant aether, in an October 1757 paper Lalande pointed out that this conjecture would spell the eventual demise of the solar system as the planets would collapse into the Sun; this resistant aether, if it existed, like the gravitational pulls of Jupiter and Saturn would also have further delayed the transit of the returning comet. When the comet (roughly) arrived according to Lalande’s original calculations, there was no evidence for further deviation by resistant aether.
Of particular interest (and further evidence that the comet of 1759’s triumph was not self-evident), was the effort Lalande was required to exert in convincing his audiences that the comet of 1579 was the same as that of 1682. After all, it had rather different look in its return. Lalande was forced to spend a considerable portion of his re-edition of Halley’s Synopsis emphasizing the Newtonian explanation of comet tails — they had to be understood as constantly variable for the comet of 1579 to be identifiable with that of 1682. And still, to the casual natural-philosophical hobbyist with an iota of common sense, acknowledging that comet’s tails are constantly changing is not demonstrable proof that two differently-appearing comets are the same comet. This is of great interest to me: if the two comets were not recognized as one, the comet of 1759 confirms neither the periodicity of comets, nor Halley’s cometography, nor universal gravitation, nor denies the existence of Euler’s resistant aether. All of these “proofs,” to the pre-Schafferian historiography so indisputably indicative of a rationalist positive triumph, made possible by Lalande’s considerably elaborate quantitative gymnastics calculating the effects of Jupiter’s and Saturn’s gravity on the comet’s path, depend upon the qualitative judgment of the comet’s appearance. In contrast to the assumptions of our pre-1987 historiography, the work on cometary theory was far from over in 1759.
And likewise neither was cometary cosmic significance. Halley and Newton themselves acutely embody this contradiction. While their cometography was “rashly” assumed to put an end to this signification, they insisted comets “could fit into a single divinely planned economy” and connected them “with the stability of the solar system, the scriptural history of the Earth, including the Deluge and the Apocalypse and the restoration of matter and activity of the planets and the Sun.” These insistences gave post-Newtonian thinkers like Maupertuis and Wiston license to drum up cometary scenarios as eschatological as those of Reformation Protestant doomsayers, much to Johann Lambert’s frustration who quipped that “comets are no longer fearful through their significance but through their effect” and reduced his post-Newton contemporaries as “no better than what he called ‘authorized prophets.’” This diminutive moniker, I think, and I think Schaffer hints as much in his lecture, could just as well be applied to Newton and Halley, and, more imporantly, to the historians of science who told us bedtime stories of the inexorable triumph of reason over superstition, little aware of their infantile resemblance to Grimm moralizing about the triumph of Good over Evil, Light over Dark, and just about as mythological to boot.
Notes
- 46 – “As the satirists rightly saw, very close connections did exist between the accomplishment of the return of 1759 as a proof of Newtonian cometography and the deliberate interpretation of the cometography as part of a general cosmological account of the past and future history of the world.”
- 47 – “Quite apart from the contemporary English embarrassment that the recovery of the comet was at best the accomplishment of a group of French astronomers around Claraut and Delisle, and at worst that of a Saxon peasant, the reproduction of this sentiment needed considerable interpretive labour. Furthermore, as we shall see, this was by no means the most significant enterprise of cometary debate in the 1750s. The recovery of the comet as a triumph of celestial mechanics, then, was a deliberate task set by workers in London and Paris and not the self-evident destruction of superstition by true astronomy.”
- “In this paper I examine the relationship between the careers of two astronomers of the period. Jerome Lalande and Johann Lambert, and their interested use of the resources located in cometography. It will be argued that the comet was a resource used for profoundly differing theological, ideological and cosmological purposes. This was the object’s cultural significance.”
- 48 – “In June 1757 he [Lalande] began aiding the work of Clairaut and Mme. Lepaute on the calculation of the effects of Jupiter and Saturn on the comet’s path through the space of 150 years.”
- 48-9 – “Part of the purpose of this paper was to refute the conjectures of Euler, on the possible perturbations of cometary and planetary paths due to unpredictable effects of a resisting aether. Such a resistance would send the Earth and the other planets spiralling into the Sun, and would have changed the time of the cometary return. He demonstrated that ‘this acceleration of the Earth should already have led to a deadly consequence for humanity, in letting us know almost the time and the manner in which it must end.’”
- 49 – Lalande in 1802 – “The comet of 1759 was the first remarkable event which signaled the beginning of this happy and brilliant revolution. Halley predicted it in 1705 but the event was necessary to confirm it. . . . This comet, at the same time, provided an admirable proof of universal attraction. Its return should have been delayed 20 months by the attractions of Jupiter and Saturn, following the results of the immense calculations which Clairaut and I made in advance and this delay was almost precisely confirmed by the observed return.”
- 49-50 – “It was hard to convince his audiences that the object which appeared during winter and spring 1758-1759 was the same as that of 1682. It differed so markedly in appearance that Lalande was compelled to spend a considerable portion of his re-edition of Halley’s Synopsis in an exegesis of the Newtonian account of the origin of cometary tails, since their variability was the only acceptable account of this dramatic transformation.”
- It’s amazing to me that despite all of the extraordinary quantitative reasoning employed to determine the comet’s delay by the pulls of Jupiter and Saturn, the success of this ‘happy and brilliant revolution (48)” hinged upon the qualitative trifle of the comet’s external appearance. If you can’t identify the 1759 comet with the 1682 comet, then you discount Halley’s periodicity and thus his cometary theory and also the law of universal gravitation.
- 51 – “The second trouble for cometographers in Paris in the 1750s, including Lalande, was the interpretation of the cosmological function of comets. Historians have often rashly assumed that the final propositions of the Principia, together with the triumph of 1759, must mark the end of comets’ role as cosmic signifiers. . . . In fact, most English commentators on Newtonian cometography were keen to show the divine and cosmological significance of comets, precisely because Halley and Newton had shown how these objects could fit into a single divinely planned economy. Newton and Halley connected comets with the stability of the solar system, the scriptural history of the Earth, including the Deluge and the Apocalypse and the restoration of matter and activity of the planets and the Sun.”
- 52-3 – “Maupertuis’s purpose was to deny divine teleology as a guarantee of cosmic stability. He rejected Newton’s supposition that only the smallest comets approached the Sun lest cosmic perturbation result. Maupertuis instructed his fair correspondent that comets could ‘bring fatal changes to our Earth and to the whole economy of the heavens against which only habit reassures us . . . they are capable of causing us all the the [sic] catastrophes which I have just explained to you.’ The English cosmological versions of cometography licensed this view: ‘One of the greatest astronomers of the century, Gregory, has spoken of comets in a manner which re-establishes them in all that reputation of terror which they once had.’”
- Fascinating, the recapitulation of cometary eschatology along naturalistic lines, but still with divine purposes
- 53 – “Buffon suggested that a massive comet had detached a portion of the Sun’s incandescent body and thus formed the planets, ‘at the time when Moses said that God divided light from darkness.’”
- 55 – “In 1757 and 1759 Lalande argued for a separation between astrotheology and celestial mechanics in the case of the possible secular accelerations of the Moon and the comets due to some aethereal resistance. Since it would send the Earth spiralling into the Sun, authorities such as Halley and Euler had tried to use this acceleration as an argument against atheist eternalism. Lalande replied that no such changes were observed . . .. In 1774 he told Voltaire that he subscribed to the Platonist doctrine of a universal geometer: the function of astronomy was the destruction of ‘all the superstitions of men.’”
- 62 – “For the next decade he produced a stream of papers on all branches of philosophy and mathematics, including deeply influential cometary analysis, which provided sources for future work by the German astronomers Olbers and Gauss, who defined all subsequent approaches to cometary prediction from the first decade of the next century. Their program, using Lambert’s techniques, utterly changed the status of comets in astronomy and led directly to the construction of a new celestial mechanics and a new stellar astronomy in the German observatories.”
- 63 – “However, the fundamental contrast between Lalande and Lambert remained their attitude to cosmic stability. Lambert designed a universe which was finite, bounded and unchanging. The Sun is a member of an orbiting cluster of stars, and such clusters compose our galaxy. The appearance of the Milky Way was the effect of looking sideways through the disc. Such a disc, Lambert suggested, was itself composed of clusters of stars each moving round a central, massive object. Ultimately, this cosmopolitical hierarchy continued almost indefinitely, but ‘you will finally come to the centre of the whole world-edifice, and here I find my last bady which steers around itself the whole creation. . . . There is the throne to which all systems attend like so many satellites, the capital city that issues laws to the realm of reality and keeps all in order and complete harmony, makes all a whole, bans all excess, and sets a limit to the revolt and dissolution of each fleeing part, and guides it back to its proper place.’”
- 64 – “Lambert pointed out that the accomplishment of Newtonian cometography in sacred physics and in the work of Maupertuis or Wiston meant that ‘comets are no longer fearful through their significance but through their effects.’ . . . According to Lambert, the work on comets since Newton and Halley made contemporary astronomers no better than what he called ‘authorized prophets.’ His new cosmology was designed to find a better job for cosmologists.”
- 65-6 – “In this paper, I have examined the cometary cosmology of two astronomers who both took an active role in the interpretation of the return of Halley’s Comet and who both worked strenuously to further the development of the celestial mechanics of cometary motion. Against the historiography which makes that return of the self-evident triumph of a single form of rational astronomy, and uses 1759 as a key marker in the destruction of cometary and cosmological significance, I have shown that both Lalande and Lambert sought to make cosmologies which gave comets fundamental roles in the universal economy which they did not perceive as contradictory with an analysis of secular stability and astronomical prediction.”
