Trying Ursus: A Reappraisal of the Tycho-Ursus Priority Dispute

Jarrell R. , “The contemporaries of Tycho Brahe”, in Taton R. Wilson C. (eds), Planetary astronomy from the Renaissance to the rise of astrophysics, Part A: Tycho Brahe to Newton (Cambridge, 1989), 22–32, p. 22.

Ibid., 31.

See Schofield C. , Tychonic and semi-Tychonic world systems (New York, 1981), 118–19, and Schofield C. , “The Tychonic and semi-Tychonic world systems”, in Taton Wilson (eds), op. cit. (ref. 1), 33–44.

Only recently a book-length study of Ursus has been published (in German): Launert D. , Nicolaus Reimers: Günstling Rantzhaus — Brahes Feind, Leben und Werk (Munich, 1999).

Letter from Tycho Brahe to Georg Rollenhagen, 26 September 1600. Quoted in both Rosen E. , Three Imperial Mathematicians: Kepler trapped between Tycho Brahe and Ursus (New York, 1986), 307, and in Thoren V. , The Lord of Uraniborg (Cambridge, 1990), 454.

That is, a member of the Council of the Kingdom of Denmark.

Gingerich O. Westman R. , “The Wittich connection: Conflict and priority in late sixteenth-century cosmology”, Transactions of the American Philosophical Society, lxxviii/7 (Philadelphia, 1988), 1–76, p. 50.

Iliffe R. , “In the warehouse: Privacy, property and priority in the early Royal Society”, History of science, xxx (1992), 29–62, p. 30.

Gingerich Westman , “The Wittich connection” (see ref. 7), 63.

See Schofield , Tychonic and semi-Tychonic world systems (ref. 3), 108–67, and Schofield , “The Tychonic and semi-Tychonic world systems” (ref. 3), 33–44.

Iliffe , “In the warehouse” (ref. 8), 52.

Westman R. , “The astronomer's role in the sixteeenth century: A preliminary study”, History of science , xviii (1980), 105–47, pp. 124–5. See also Thoren V. , “Tycho Brahe as the dean of a renaissance research institute”, in Osler M. Farber P. (eds), Religion, science and worldview: Essays in honor of Richard S. Westfall (Cambridge, 1985), 275–95.

Jardine N. Harloe K. , “Kepler's refutation of Ursus's Demonstratio”, in Jardine N. , “Tycho v. Ursus: The build-up to a trial”, Journal for the history of astronomy , xxxvi (2005), 81–106 (Part 1) and 125–65 (Part 2), pp. 151–65, see p. 152.

Gingerich Westman , “The Wittich connection” (ref. 7), 71. See also Gingerich O. Voelkel J. , “Tycho Brahe's Copernican campaign”, Journal for the history of astronomy , xxix (1998), 1–34.

Jardine N. , The birth of history and philosophy of science: Kepler's A defence of Tycho against Ursus with essays on its provenance and significance (Cambridge, 1984; hereafter: Birth of HPS).

Jardine , “Ursus' Tractatus”, in Birth of HPS (ref. 15), 29–57.

Ursus's argument is essentially what the philosopher of science Larry Laudan has called “pessimistic meta-induction”.

Rosen , Three Imperial Mathematicians (ref. 5).

Jardine N. Segonds A. , La guerre des astronomes: La querelle au sujet de l'origine du système géo-héliocentrique à la fin du XVIe siècle . Vol. i, Introduction (Paris, 2008). Vol. ii/1, Le Contra Ursum de Jean Kepler: Introduction et textes préparatoires (Paris, 2008) is a critical edition of preparatory texts for Kepler's Apologia, together with essays on its persuasive strategies and recent interpretations. Vol. ii/2, Le Contra Ursum de Jean Kepler: Édition critique, traduction et notes (Paris, 2008) is a critical edition of the Apologia, with Latin-French translation and notes. Subsequent volumes (in preparation) will cover the relevant works of Tycho, Ursus and Roeslin.

Gingerich Westman , “The Wittich connection” (ref. 7).

Jardine , “Tycho v. Ursus” (ref. 13).

Launert D. , “A letter of complaint against Tycho from Ursus to the Emperor (1597)”, in Jardine , “Tycho v. Ursus” (ref. 13), 89–92.

Launert D. Jardine N. , “The production of Ursus's De astronomicis hypothesibus (Prague, 1597)”, in Jardine , “Tycho v. Ursus” (ref. 13), 92–5.

Launert D. Jardine N. Segonds A. , “Ursus's anonymous pamphlet on the ancient origins of geo-heliocentric hypotheses”, in Jardine , “Tycho v. Ursus” (ref. 13), 129–36.

Jardine N. Segonds A. , “The formal refutation of Ursus's Demonstratio by Johannes Müller, briefed by Tycho Brahe”, in Jardine , “Tycho v. Ursus” (ref. 13), 137–50.

Jardine Harloe , op. cit. (ref. 13), 151–65.

Also fully translated into English by both Rosen Jardine . See Rosen , Three Imperial Mathematicians (ref. 5), 290–6, and Jardine , Birth of HPS (ref. 15), 67–71.

Johannes Kepler gesammelte Werke (22 vols, Munich, 1938–2009), and Tychonis Brahe Dani opera omnia (15 vols, Copenhagen, 1913–29).

Though one is available in German, see ref. 4.

Caspar M. , Kepler , transl. by Hellman C. Doris , 2nd edn (New York, 1993), and Thoren, The Lord of Uraniborg (ref. 5).

On the basic facts presented in this section, all authors who have seriously studied the Tycho–Ursus affair agree: See Rosen , Three Imperial Mathematicians (ref. 5); Jardine , Birth of HPS (ref. 15); Gingerich Westman , “The Wittich connection” (ref. 7); and O. Gingerich, The book nobody read: Chasing the revolutions of Nicolaus Copernicus (New York, 2004).

For more on Tycho's struggle with Mars's parallax, see Gingerich Voelkel , op. cit. (ref. 14), and Gingerich Westman , “The Wittich connection” (ref. 7), 69–76.

He had first broached the issue of Ursus's plagiarism in letters of 4 November and 21 December 1588, addressed respectively to his former teacher Henry Van Den Brock (Brucaeus) and to his friend Heinrich Rantzau, the Governor of Holstein and Ursus's former patron, through whom Tycho had first known about Ursus's whereabouts in Kassel.

Letter from Christoph Rothmann to Tycho Brahe, 26 August 1586, in Rosen , Three Imperial Mathematicians (ref. 5), 224.

Ibid., 92.

For an account of this, see Caspar , Kepler (ref. 30), 111–21.

Letter from Johannes Kepler to Nicolaus Ursus, 15 November 1595.

Letter from Tycho Brahe to Johannes Kepler, 11 April 1598.

Letter from Johannes Kepler to Tycho Brahe, 19 February 1599.

Letter from Tycho Brahe to Johannes Kepler, 9 December 1599.

Tycho Brahe to Johannes Kepler, 28 August 1600, in Rosen, Three Imperial Mathematicians (ref. 5), 302.

Ibid., 305.

Ibid., 307.

Jardine N. Segonds A. Mosley A. , “Introduction”, in Jardine , “Tycho v. Ursus” (ref. 13), 81–9, p. 85.

Launert Jardine , op. cit. (ref. 23), 93.

Letter from Tycho Brahe to Georg Rollenhagen, 26 September 1600, in Rosen , Three Imperial Mathematicians (ref. 5), 303–7. This explains why Ursus's book is so rare. According to Gingerich, only around a dozen extant copies of the Tractatus have been located worldwide. See Gingerich , The book nobody read (ref. 31), 118.

Letter from Tycho Brahe to Georg Rollenhagen, 26 September 1600 (ref. 46).

Jardine Segonds Mosley , op. cit. (ref. 44), 85.

Letter from Tycho Brahe to Georg Rollenhagen, 26 September 1600 (ref. 46).

Ibid.

A full English translation of the Apologia is provided by Jardine in his Birth of HPS (ref. 15), 134–207. I use the page numbers of this translation when I quote from the Apologia.

Kepler , Apologia, 136.

For the dating of the Apologia see Rosen E. , “Kepler's defense of Tycho against Ursus”, Popular astronomy , liv (1946), 405–8, and Jardine N. , “The circumstances of composition”, in Birth of HPS (ref. 5), 9–28.

Letter from Johannes Kepler to David Fabricius, 2 December 1602, in Rosen , Three Imperial Mathematicians (ref. 5), 318.

Johannes Kepler gesammelte Werke, xx/1 (Manuscripta astronomica I).

Letter from Kepler to Ursus, 15 November 1595, in Jardine , Birth of HPS (ref. 15), 53–4. Rosen , Three Imperial Mathematicians (ref. 5), 86, gives a slightly different translation (“I love your hypotheses”).

Caspar , Kepler (ref. 30), 119.

Rosen , op. cit. (ref. 53), 408.

Rosen , Three Imperial Mathematicians (ref. 5), 15.

Jardine , Birth of HPS (ref. 15), 2.

Ibid., 5.

Martens R. , Kepler's philosophy and the new astronomy (Princeton, 2000), 57.

Voelkel J. , The composition of Kepler's Astronomia Nova (Princeton, 2001), 125.

Westman , “The astronomer's role” (ref. 12), 126.

See Jardine , “The scope and form of the Apologia”, in Birth of HPS (ref. 15), 72–9.

Schofield , Tychonic and semi-Tychonic world systems (ref. 3), 132.

Kepler , Apologia, 135–6.

Letter from Kepler to Herwart von Hohenburg, 30 May 1599, in Jardine , Birth of HPS (ref. 15), 61. By “his confession” Kepler refers to Ursus's quip in the Tractatus: “Let it be a theft, but a philosophical one. Learn to safeguard your things hereafter.”

Kepler , Apologia, 190.

Ibid., 206.

Letter from Kepler to Herwart von Hohenburg, 30 May 1599, in Jardine , Birth of HPS (ref. 15), 64–5.

Jardine Harloe , op. cit. (ref. 13), 162.

Such as, for instance, in his above-quoted letter to Herwart von Hohenburg. See Jardine , Birth of HPS (ref. 15), 59–60.

Letter from Kepler to Ursus, 15 November 1595. Fully translated in Jardine, Birth of HPS (ref. 15), 53–4.

Kepler , Apologia, 139.

Ibid., 144.

Ibid., 153.

Ibid., 156.

Ibid., 185–6.

Ibid., 144–5.

Kepler J. , New astronomy, transl. by Donahue W. (Cambridge, 1992), 28.

Kepler , Apologia, 191–2.

Jardine Harloe , op. cit. (ref. 13), 163.

Ibid.

Kepler , Apologia, 206.

Rosen , Three Imperial Mathematicians (ref. 5), 333. Rosen's suggestion is based upon Kepler's own words in the introduction to the Apologia: “And in itself the undertaking was an honourable one: To root out the erroneous opinions from the minds of students, and to obliterate the calumnies against the mathematicians impressed on the minds of patrons” ( Kepler , Apologia , 136).

A member of the Council of the Kingdom of Denmark.

According to the account given in the letter from Tycho Brahe to Georg Rollenhagen, 26 September 1600. See Rosen , Three Imperial Mathematicians (ref. 5), 305.

Jardine N. Tybjerg K. , “The lost copy of Ursus's De astronomicis hypothesibus marked for use in his trial”, in “Tycho v. Ursus” (ref. 13), 97–106.

Launert , op. cit. (ref. 22), 89–92.

Translated in Rosen, Three Imperial Mathematicians (ref. 5), 289–96, and Jardine , Birth of HPS (ref. 15), 67–71. Kepler himself dates it around a year before the Apologia.

Launert Jardine Segonds , op. cit. (ref. 24), 129–36.

Uraniborg opened in 1576, but serious and systematic observing began later. Stjerneborg, the underground observatory, opened in 1584.

Whereas in the Ursine system, Mars and the Sun are equidistant from the Earth at opposition.

Letters, from Tycho Brahe to the Landgrave Wilhelm IV, 18 January 1587; Tycho Brahe to Christoph Rothmann, 21 February 1589; and Tycho Brahe to Thaddeus Hayek (Hagecius), 1 November 1589.

Letter from Tycho Brahe to Henry Van Den Brock (Brucaeus), spring of 1584 (undated).

Some of these diagrams, described in detail by Gingerich Westman in “The Wittich connection” (ref. 7), are bound at the end of Wittich's personal copy of the first edition of Copernicus's De revolutionibus, now at the Biblioteca Apostolica Vaticana (this copy had been first mistakenly identified as Tycho's copy). Upon learning of Wittich's death, Tycho acquired some items from Wittich's personal library, including this volume.

For a useful chronology of Wittich's wanderings, see Gingerich Westman , “The Wittich connection” (ref. 7), 67–69. Tycho carefully recorded the dates of people's visits to Uraniborg in his meteorological diaries.

Ibid.

Even Tycho admits this in his letter to Kepler of 9 December 1599: “He [Hansen] arrived a little after Ursus had been with me, and therefore he found out from my other students how deceitfully Ursus had behaved.” See Rosen , Three Imperial Mathematicians (ref. 5), 242.

Ibid., 251.

Interestingly, in his letter to Anders Vedel (Velleius) of 18 September 1599, Tycho relates that Lange had been “compelled” to testify before a notary against his former employee Ursus, “even though he did this reluctantly”. See Rosen , Three Imperial Mathematicians (ref. 5), 254. We do not have Lange's testimony, but we can surmise Tycho somehow pressed him to testify on his behalf.

See Schofield , “The Tychonic and semi-Tychonic world systems” (ref. 3), 43.

For more on the Tycho–Liddell affair, see Schofield , Tychonic and semi-Tychonic world systems (ref. 3), 145–60, and Thoren , The Lord of Uraniborg (ref. 5), 455–8.

From Ursus's Tractatus, translated by Jardine , Birth of HPS (ref. 15), 35–6. Tycho's wife, Kirsten Jørgensdatter, was a commoner to whom he was informally engaged, as given his social status they could not legally marry. Despite his protests about Ursus's calumnies, Tycho repaid him in his own coin, at least in his private correspondence: In a letter of 18 September 1599 to his former teacher Anders Vedel (Velleius), he refers to Ursus's wife as “a notorious adulteress” (Rosen, Three Imperial Mathematicians (ref. 5), 254) and in his letter to Rollenhagen of 26 September 1600, he reports that Ursus's death may have been caused by an attack in the French camp (syphilis), “to which he was accustomed” (Rosen, Three Imperial Mathematicians (ref. 5), 303).

Jardine Tybjerg , op. cit. (ref. 89), 97–106, esp. pp. 100–2.

Letter from Nicolaus Ursus to Emperor Rudolph II, 1 June 1597. Transl. by Launert , op. cit. (ref. 22), 90–1.

For this reason, I find Schofield's assertion that “Ursus alleged actual priority of discovery over Tycho” (Tychonic and semi-Tychonic world systems (ref. 10), 166) questionable.

See Jardine , Birth of HPS (ref. 15), 41–2.

Ibid., 48.

A version of the geo-heliocentric system in which Mercury and Venus circle the Sun, which in turn circles the Earth, but the superior planets (Mars, Jupiter and Saturn) circle the Earth. In the Tychonic system, all planets circle the Sun, which revolves around the Earth (unlike Copernicus, Tycho did not regard the Earth as a planet).

However, the part of Kepler's refutation of Ursus's claims regarding Copernicus is missing from the Apologia, which Kepler left unfinished.

Transl. by Rosen , Three Imperial Mathematicians (ref. 5), 325.

Transl. by Jardine , Birth of HPS (ref. 15), 42.

Transl. by Rosen , Three Imperial Mathematicians (ref. 5), 325. Kepler also pointed out this contradiction in the Apologia, 148.

See Schofield , Tychonic and semi-Tychonic world systems (ref. 3), 118–19.

Jardine Launert Gingerich Westman all agree on this translation. Rosen offers a slightly different translation (“intellectual” instead of “philosophical”) in Three Imperial Mathematicians (ref. 5), 195.

Kepler Both Rosen take Ursus's remark at face value, namely as a plain admission of theft, but Jardine contends that it was clearly intended as a rhetorical strategy. Gingerich and Westman endorse the latter interpretation and further suggest that Wittich may have been the source of Tycho (and perhaps Ursus).

The complete title in English translation is “Demonstration: That the Apollonian (that is, of Apollonius of Perga) hypotheses of the celestial motions are explicitly described in the surviving works of Martianus Capella, a most ancient author, and of Nicolaus Copernicus”. See Launert Jardine Segonds , op. cit. (ref. 24), 129–36.

Ibid., 134.

Ibid.