Cometary transits have always displayed the troubled relationship between astronomers, theologians, natural philosophers, and their public.
Simon Schaffer, 1987
Drawing by Honoré Daumier, 1857. From the Art Institute of Chicago
Between 1987 and 1993, Simon Schaffer published five papers on the history of cometography, meditating on some of his favorite themes concerning the links between cosmology, scientific methodology, scientific identity, epistemology, theology, politics, authority, social order, and the hermeneutics of history:
(1) “Newton’s Comets and the Transformation of Astrology” in Astrology, Science and Society: Historical Essays (1987), edited by Patrick Curry.
(2) “Authorized Prophets: Comets and Astronomers after 1759,” Studies in Eighteenth-Century Culture 17 (1987): 45-74.
(3) “Halley, Delisle, and the Making of the Comet” in Standing on the Shoulders of Giants: A Longer View of Newton and Halley (1990), edited by N. Thrower.
(4) “Comets and the World’s End” in Predicting the Future (1993), edited by L. Howe and A. Wain.
(5) “Comets & Idols: Newton’s Cosmology and Political Theology” in Action and Reaction (1993), edited by Paul Theerman and Adele Seeff.
From his earliest publications, comets had played a role in Schaffer’s thinking about seventeenth and eighteenth-century cosmology and philosophical inquiry: they were frequently called upon to fill various cosmological roles as agents of destruction, transportation, and restoration. In these five pieces, Schaffer provided further evidence for the centrality of comets in natural philosophical problematics, and clarified the staggering variety of implications cometography could have within and beyond them. In this post, I outline a few of the features of his decidedly complex set of arguments. In its sequel, I will look at Schaffer’s historiographical thinking in (4) and (5).
Although Schaffer’s examination of cometography stretches from Tycho Brahe (1546-1601) to the middle of the 19th century, the bulk the history in this series begins with Newton’s consideration of comets around 1680. Schaffer observes that in 1680 Newton understood comets to be ephemeral phenomena. Accordingly when Astronomer Royal John Flamsteed suggested to him that the 1680/1 comets had been one comet traveling in different directions, Newton dismissed it out of hand. By 1684, though, Newton (to the chagrin of Flamsteed) had changed his mind about the cosmological place of comets, now thinking them permanent celestial bodies. Accordingly, per the thinking of the time, they ought to move in closed orbits. Schaffer notes that before Newton had any observational basis on which to say so, he deemed their orbits must be elliptical.
For Newton, Schaffer emphasizes, arriving at a proper understanding of the behavior, nature, and cosmological function of comets in a divinely ordered and sustained universe was part and parcel of restoring a correct natural religion. Newton believed that ancient Chaldeans had possessed an uncorrupted natural philosophy as reflected in the symbolism of Vestal temple ceremonies, which had been corrupted by various “idols”, such as the physical reality of the celestial spheres introduced by literal-minded Greeks. Such idols could be used to claim illegitimate authority (see also Schaffer’s nice discussion of Hobbes’ arguments in his “Wallification” paper and Leviathan and the Air Pump), and were part of Newton’s privately circulated criticisms of ideas such as the inhabitation of the spheres by the souls of dead kings, astrology, as well as the doctrine of the Holy Trinity.
As to Halley’s famous 1717 prediction that the comet of 1682 would return in 1758 or 1759, Schaffer notes that it took some work before the prediction was widely accepted as a triumph for Newton’s mathematical principles as abstracted from his natural philosophy. In the first decades of the eighteenth century Newtonian mechanics did not prevail on the Continent until pushed by a small coterie of astronomers, including Joseph-Nicolas Delisle (1688-1768), who learned English astronomy and conversed with Halley (1656-1742) on a 1724 visit to England.
Delisle was eager to encourage Halley’s methods, but his 1725-1747 posting to the St. Petersburg Academy was effectively an “exile”, while other Continental Newton sympathizers remained unsuccessful in their own propaganda. It gave him time to develop his astronomical methods and to collaborate and debate with the great mathematician Leonhard Euler (1707-1783) who worked in St. Petersburg and Berlin in this period. But it was only after his eventual return to Paris that he had the opportunity to expound the importance of Halley’s astronomy.
By the time the 1682 comet was due to return, a new celestial mechanics had been developed. While appreciative of Halley’s methodology contrary to other natural philosophical approaches, the proponents of the new celestial mechanics, such as Delisle, Alexis Claude de Clairaut, and Jérôme Lalande, were eager to highlight their achievements and to observe the insufficiencies of Halley’s methods, including the impossibility of their arriving at a definitive prediction of even the closure of the comet’s orbit (due to methodological insufficiencies and the need to better analyze perturbations in the comet’s orbit). However the opponents of Delisle, Lalande, and their allies—such as Pierre Charles Le Monnier and Jean le Rond d’Alembert (whose Encyclopédie project helped establish the cult of Newton in French Enlightenment thought)—insisted that the cometary return was Halley’s achievement alone.
Finally, Schaffer argues for Newtonian astronomy’s transformation—rather than elimination—of the portentous significance of comets. As orbiting comets became a part of natural philosophical cosmologies, they took on all manner of physical (rather than symbolic) roles. They could be responsible for renourishing the vitality of the earth (which Newton thought), or restoring the sun’s expended luminous matter (as William Herschel (1738-1822) among others suspected). Their gravity might have been responsible for the pre-Genesis chaos and the Deluge (as Halley suggested), and might be responsible for future disasters. Or comets might actually collide with the earth at some point in the future. According to Buffon’s 1749 cosmology, a cometary collision with the sun was responsible for the creation of the earth.
Astronomers with the analytical power to predict cometary paths took it upon themselves to mediate just what dangers comets did and did not represent. In the Newtonian cosmology, the action of God intervened to maintain the stability of creation. Accordingly, comets were necessarily prevented from colliding with planets or disturbing the stability of their orbits. Other philosophers (following Gottfried Leibniz and Christian Wolff) understood comets as elements of an innately stable, divinely planned cosmos. Later astronomers were less willing to admit anything that smelled of an Aristotelian final cause and allowed that cometary disaster could not be probabilistically ruled out.
Beginning in the mid-eighteenth century, astronomers understood it as their responsibility to counteract public beliefs about comets. When in 1773 Lalande speculated about possible collisions and caused a public panic, he was arrested for a breach of the peace and the incident highlighted for members of the Academy the difficulty of using exotic ideas like “probability” in public.
For Schaffer, all these issues were encapsulated neatly in Alsatian natural philosopher Johann Lambert’s 1761 sniff that astronomers had made themselves into “authorized prophets”.
It’s not as visually appealing as the one above, but this Daumier illustration nicely makes Schaffer’s general point.