Sunspots or Sun's Planets: Jean Tarde and the Sunspot Controversy of the Early Seventeenth Century

North John , “Thomas Harriot and the first telescopic observations of sunspots”, Thomas Harriot: Renaissance scientist, ed. by Shirley John (Oxford, 1974), 129–65. Sunspots were noted by naked-eye observers in Europe and especially China for centuries before the invention of the telescope.

Scheiner C. , Tres epistolae de maculis solaribus (Augsburg, 1612). They have been reprinted in Opere di Galileo Galilei, ed. by Favaro Antonio (20 vols, reprinted Florence, 1968), v, 26ff. Galileo's responses are also in Opere, v, and have been translated by Stillman Drake, Discoveries and opinions of Galileo (Garden City, N.Y., 1957), 89–143. For an analysis of the dispute between Scheiner and Galileo over sunspots, see Shea William , Galileo's intellectual revolution (New York, 1972), 48–74.

For example of how heated the debate over priority could be 250 years later, see the exchange between Tousessart E. L. and Dallet M. G. in Revue scientifique, xxx (1882), 9–13, 80–92, 144–9, over whether Galileo was the first to use the telescope as an astronomical instrument.

For biographical information on Tarde see Dujarric-Descombes A. , “Recherches sur les historiens du Périgord au XVIIe siècle: Jean Tarde”, Bulletin de la Société Historique et Archéologique du Périgord, ix (1882), 371–412; Moureau François (ed.), A la rencontre de Galilée: Deux voyages en Italie (Geneva, 1984), 9–12; and Edward Rosen's entry in the Dictionary of scientific biography, xii, 256–7.

Dujarric-Descombes , “Recherches”, 380–1. Tarde also wrote a well-regarded history of Sarlat, published by G. de Gérard as Les Chroniques de Jean Tarde (Oudin, 1887).

Moureau , Deux voyages, 45–97. The section on Tarde's visit to Galileo is excerpted in “Dal Diario del Viaggio di Giovanni Tarde in Italia”, Opere di Galileo Galilei, xix, 589–92; and Favaro Antonio , “Di Giovanni Tarde e di una sua visita a Galileo”, Bulletino di bibliografia e di storia delle scienze matematiche, xx (1887), 345–71. Tarde had made an earlier trip to Italy in 1593.

“Le mercredi au matin, je vis le seigneur Galileus Galilei, philosophe et astrologue très fameux…. Je lui représentai que sa réputation avait passé les Alpes, traversé la France et parvenue jusques la mer Océane” ( Moureau , Deux voyages, 60). Balfour had a copy of Copernicus's De revolutionibus in his library. Taton René , “Contribution à l'étude de la diffusion du De revolutionibus”, Revue d'histoire des sciences, xxvii (1974), 307–27.

Moureau , Deux voyages, 60–66. See pp. 21–22 for Tarde's letter to Galileo.

Ibid., 79–81. Contrary to Stillman Drake, Galileo studies (Ann Arbor, 1970), 190, Galileo did not discuss with Tarde his dispute with Scheiner.

Moureau , Deux voyages, 62; Tarde , “Dal Diario”, 590.

Dujarric-Descombes , “Recherches”, 377, states that Tarde's sketches of sunspots were still extant in 1789 but disappeared during the Revolution.

Tarde J. , Borbonia sidera, id est planetae qui Solis limino circum volitant motu proprio et regulari, falso hactenus ab helioscopis maculae Solis nuncupati. Ex novis observationibus Joannis Tarde, canonici theologi eccl. cathed. Sarlati (Paris, 1620); in French , Les Astres de Borbon et apologie pour le soleil. Monstrant et vérifiant que les apparences qui se voyent dans la face du soleil sont des planètes et non des taches, comme quelques italiens et allemans observateurs d'icelles luy ont imposés (Paris, 1622). I have seen both versions, and it is clear that the French is an exact translation of the Latin, which Tarde is said to have done himself. I will be citing the French.

Donahue W. H. , “The solid planetary spheres in post-Copernican natural philosophy”, in The Copernican achievement, ed. by Westman Robert (Los Angeles, 1972), 244–75, p. 266.

Bound with Astres de Borbon is an explanation of the telescope and a defence of it as a source of valid data, Telescopium, seu demonstrationes opticae…, (Paris, 1620). Dujarric-Descombes , “Recherches”, proposes that the two pieces were published together. On telescopes Tarde appears to have made extensive use of Scheiner , Tres epistolae de maculis, although he did not cite him on optics as he did for sunspots.

Tarde , Astres de Borbon, 5, made the same citation to Pithou Pierre , Annalium et historiae Francorum, first published in 1588, as Galileo did. Drake , Discoveries and opinions, 117.

Tarde , Astres de Borbon, 3, 13.

Maximus of Turin cited by Daniel Boorstin, The discoverers (New York, 1983), 16. Pierre de Bérulle, Discours de l'éstat et des grandeurs de Jesus (Paris, 1619), ii, 160: “Car Jesus est le Soleil immobile en sa grandeur, et mouvant toutes choses … Jesus est le vray Centre du Monde.” For similar statements see Birkenmajer A. , Le Soleil à la Renaissance: Science et mythes (Brussels, 1965). On solar symbolism as used by the French monarchy in Tarde's era, see Hennequin J. , Henri IV dans ses oraisons funèbres ou la naissance d'une légende (Paris, 1977), 62–67. Professor Richard Jackson provided me with this reference.

Tarde , Astres de Borbon , 18–19, 30. On Kepler's mistaken idea that he had seen a transit of Mercury, see Casper Max , Kepler (London, 1959), 106–7. Kepler later recognized that he had seen a sunspot and bemoaned the fact that he could have had the honour of being first to discover the spots. Tarde cited Scaliger's Contre Cardane, which almost certainly is his Exotericarum exercitationum liber xv (Paris, 1557). I have not found the reference, but the work is enormous. On the transits, see also Woolf Harry , The transits of Venus (Princeton, N.J., 1959).

Tarde , Astres de Borbon, 19.

Galileo's arguments against the spots as stars or planets were set out most clearly in his second letter to Welser, in Drake , Discoveries and opinions, 104–9. Tarde cited the letters to Welser and described Galileo's objections briefly but generally accurately.

See Kepler's comments on the difficulty of seeing Mercury because of its nearness to the Sun. Rosen Edward (ed.), Kepler's Conversation with Galileo's Sidereal Messenger (reprinted New York, 1965), 46.

Tarde , Astres de Borbon, 49–50.

Galileo had originally not noted the angled direction of the spots, but in 1632 he acknowledged its existence and used it as a proof for heliocentrism. See Smith Mark A. , “Galileo's proof for the Earth's motion from the movement of sunspots”, Isis, lxxvi (1985), 543–51. See also Drake , Galileo studies, 186; and Shea , Galileo's intellectual revolution, 66.

It was of course the inclination of the orbits of Venus and Mercury that made transits of the two planets such unusual events.

Tarde , Astres de Borbon, 60.

Galileo , Second letter on sunspots , in Drake , Discoveries and opinions, 117. Galileo's argument was based on a calculation of the length of a transit of Mercury, since he had never viewed one before writing the piece.

Tarde , Astres de Borbon, 26. For a similar comment by Galileo, see his letter to Giuliano de Medici, November 1610, in Opere, x, 474. Statements of that sort were in fact a commonplace of the era.

Tarde , Astres de Borbon, 64. On Martianus Capella and others, see Eastwood Bruce , “Kepler as historian of science”, Proceedings of the American Philosophical Society, cxxvi (1982), 367–94; and Jardine N. , The birth of history and philosophy of science (Cambridge, 1984), esp. 197–200.

“D'une force inherente et née avec eux et partant qu'ils se mouvent sans travail”, Tarde , Astres de Borbon, 64. The idea may have come from Galileo in 1614. See Moureau , Deux voyages, 65.

“Toute la troupe des peripateticiens”, Tarde , Astres de Borbon, 64.

Tarde , Astres de Borbon, 65.

Galileo briefly took note of the planetary theory in that work, but there is no indication that he was citing Tarde rather than Scheiner. Dialogue concerning the two chief world Systems, ed. by Drake S. (Berkeley, 1967), 53.

Malapert C. , Austriaca sidera heliocyclica astronomicis hypothesibus illigata (Mons, 1633). Malapert had finished his book by 1628 and had died in 1630.

de Larroque Tamizey P. , Les correspondants de Peiresc: Lettres inédits (reprinted Geneva, 1972), i, 332; Fletcher John , “Astronomy in the life and correspondence of Athanasius Kircher”, Isis, lxi (1970), 52–67, p. 56.

Gassendi P. , Opera omnia (reprinted Stuttgart, 1964), vi, 6; Tamizey , Les correspondants, i, 332. In 1625 Gassendi referred to the views of “a certain Frenchman”; in 1633 he referred to Tarde as “our canon of Sarlat”.

Eddy John , “The Maunder Minimum”, Science, cxcii (issue of 18 June 1976), 1189–202. See also Waldmeier M. , The sunspot-activity in the years 1616–1960 (Zurich, 1961).

Tarde Gabriel , “Observations au sujet des Astres de Borbon”, Bulletin de la Société Historique et Archéologique du Périgord, iv (1877), 169–73; Dujarric-Descombes , “Recherches”, 392.

In his Galileo studies , 188–90, Stillman Drake has dusted Tarde off a bit but for a solely negative reason, to serve as an unwitting but prominent element in the bitter Galileo-Scheiner feud. In his Assayer of 1623, Galileo wrote with great bitterness about those who attacked his letters on sunspots “pretending not to have seen my writings”. Scheiner took the attack as aimed at him specifically and began a vendetta that apparently contributed to the condemnation of Galileo ten years later. Drake argues that Galileo did not intend to attack Scheiner at that point but rather Tarde. Drake's argument is highly dubious given Tarde's extensive references to Galileo's work, whom he called “le Grand Galilée” at several points.