Christoph Rothmann's Discourse on the Comet of 1585

An Edition and Translation with Accompanying Essays


Christoph Rothmann wrote a treatise on the comet of 1585 shortly after it disappeared. Though it was not printed until 1619, Rothman sent a copy of his treatise in 1586 to Tycho Brahe, decisively influencing the latter's rejection of solid celestial spheres two years later. In his treatise, Rothmann joined the elimination of the solid celestial spheres to his concept of air as the substance filling the cosmos. He based his argument on the absence of refraction and the celestial location of the comet. The treatise also contained clear statements reflecting Rothmann’s adoption of Copernicanism. This first critical edition of the treatise is accompanied by an English translation and a thorough commentary. Some appendices with archival documents illustrate the genesis of Rothmann’s treatise.
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Biographical Note

Miguel A. Granada, Ph.D. (1978), University of Barcelona, is Professor of History of Renaissance Philosophy at the same university. He has published many monographs, translations and articles on Giordano Bruno and the astronomical and cosmological revolution in the early modern period.

Adam Mosley, Ph.D. (2000), University of Cambridge, is an Associate Professor in History and Classics at Swansea University. His publications include Bearing the Heavens: Tycho Brahe and the Astronomical Community of the Late Sixteenth Century (Cambridge University Press, 2007).

Nicholas Jardine, is Emeritus Professor of History and Philosophy of the Sciences, University of Cambridge. He is author, with Alain Segonds, of La guerre des astronomes, 2 vols (Les Belles Lettres, Paris, 2008).

Review Quotes

"Da alle drei Autoren seit Jahren zu den besten Kennern der behandelten Materie gehören, wundert es nicht, dass auch alle Essays höchst lesenswert sind. [..] Der ungewöhnlich Große wissenschaftliche Mehrwert, den das Buch liefert, deutet sich bereits in Miguel Granadas Einleitung an. [...] sowohl durch die sorgfältige zweisprachige Edition als auch aufgrund der hochwertigen wissenschaftlichen Beiträge für alle, die sich mit frühneuzeitlicher Wissenschaftsgeschichte beschäftigen, höchst lesenswert ist."
[English translation by Google Translate: "Since all three authors have been among the best connoisseurs of the subject matter for years, it is not surprising that all essays are highly readable. [...] The unusually large scientific added value provided by the book already is evident from Miguel Granada's introduction. [...] both through the careful bilingual edition as well as due to the high-quality scientific contributions for all, who deal with early modern history of science, highly worth reading." -karsten Gaulke, Berichte Wissenschafttsgeschichte 41 (2018), 194-196.

"Ultimately, this book by recognized specialists fills an important gap in the history of Renaissance astronomy and cosmology by providing a masterful study of first-hand documents that hitherto had remained unpublished in English." - Jean Seidengart (Université Paris Ouest Nanterre), Journal for the History of Astronomy, 2017, 48(2):251-252.

"Readers with an interest in the history of astronomy, scientific method, and cometary studies will profit from reading this book."
"The authors are well-known historians of astronomy. [...] The book is thoughtful, well documented, well written, and persuasive. The bibliographies of primary and secondary sources are thorough, as are the indexes of persons, places, and subjects."
"This is a model of splendid scholarship on an important aspect of early modern science."
- J.R. Christianson in: Isis Volume 106, Number 4 (December 2015): 916-917.

Table of contents

Preface xi
Miguel A. Granada
Introduction 1
Miguel A. Granada
1 Christoph Rothmann and Astronomy in Wittenberg 1
2 Astronomy in Kassel: Landgrave Wilhelm IV and His Programme of Stellar Astronomy 19
3 The Comet of 1585 and the Dialexis cometae 24
4 Phases of Composition of the Dialexis cometae 30
5 Rothmann’s Cosmological Innovations in the Dialexis cometae 36
6 The Status of Astronomical Hypotheses 55
7 The Title of the Work 64
2 Dialexis Cometae qui Anno Christi M.D.LXXXV. mensibus Octobri et Novembri apparuit 67
Latin text prepared by Miguel A. Granada
A Discourse on the Comet Which Appeared in the Months of October and November of 1585 67
Translation by Nicholas Jardine and Adam Mosley, with annotations by Miguel A. Granada, Nicholas Jardine and Adam Mosley
Chapter 1. On the Observations of This Comet 78
Chapter 2. Concerning the Motion of This Comet in Longitude and Latitude 92
Chapter 3. Whether This Comet Had Parallax 104
Chapter 4. In Which Sphere This Comet Was 114
Chapter 5. Since It Is Commonly Believed That the Spheres of the Planets Are Solid Bodies, How Could the Comet Have Progressed in Them? And What Is to Be Thought on This Question? 120
Chapter 6. A Refutation of Some Opinions Concerning Comets; Namely, That They Are Neither Species Appearing without Matter, Nor Perpetual Bodies Together with the Rest of the Stars, Nor Vapours Ignited in the Air 146
Chapter 7. The Opinion of the Author about the Matter and Essence of Comets 164
Chapter 8. The Uses of the Examination of Comets 178
Chapter 9. That That Matter Flowing around the Planets Differs Not at All from Pure Sublunar Air, and Where, Moreover, the Contrary Arguments Are Refuted 186
Description of the Comet Which Shone in the Year 1596 in the Month of July, but Set Out in a Fuller Form from the Papers of the Same Rothmann 202
3 Appendices: Related Texts and Translations 207
Miguel A. Granada, Nicholas Jardine and Adam Mosley
1 Letters of Christoph Rothmann to Landgrave Wilhelm IV of Hesse-Kassel, 1585–1586 208
2 Letter of Wilhelm IV of Hesse-Kassel to Heinrich Rantzau, 20 October 1585 246
3 Letter of Wilhelm IV to Christoph Rothmann of 18 November 1585, Authorising the Drafting of a scriptum on the Comet 250
4 Elias Olsen Morsing’s Account of the Comet of 1585 252
4 How to Present a Copernican Comet: The Form and Tactics of Christoph Rothmann’s Dialexis on the Comet of 1585 258
Nicholas Jardine
1 Introduction 258
2 Disciplines: Mathematics vs. Philosophy 260
3 Disciplines: Theology 262
4 Genres: Dialexis, ‘Critical Doxography’, Historia, Observationes 267
5 Persuasive Tactics 273
6 Comets as Boundary Objects 280
5 The History and Historiography of Early Modern Comets 282
Adam Mosley
1 1577 and All That: What Every Historian of Astronomy Knows 282
2 Historia: Comets, Astronomy, and Historical Astrology 287
3 1577 and All That Revisited 323
6 A Brief Note on Cometary Parallax 326
Adam Mosley
1 Tycho, Regiomontanus, and the Problems of Parallax 326
2 Rothmann and the Parallax of the Comet of 1585 334
3 Conclusion 339
Bibliography 341
Index of Persons 367
Index of Places 373
Index of Subjects 374


All interested in the history of astronomy and cosmology in the early modern period, and anyone concerned with the Copernican revolution and cometary theory.

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