Crüger to Müller, Easter Monday 1620
Peter Crüger, “Crüger to Müller, Easter Monday 1620,” Nova Kepleriana 4, 1620, 106–107, transcribed in Plain Old Text, https://sources.vjbe.net/stable/c2nge.
Nova Kepleriana 4 1620, p. 106–107 Summary
Part of Die Keplerbriefe auf der Nationalbibliothek und auf der Sternwarte in Paris
Crüger rejects Kepler's theory of straight-line comet paths because it assumes the earth's annual motion, mocks the 'rabid leaps' it implies, and finds the *Astronomia nova* and *Harmonice mundi* hard to follow.
Source: Peter Crüger's letter to Philipp Müller of Easter Monday 1620, written at Danzig after he had received Kepler's three books on comets (Augsburg, 1619). He rejects Kepler's straight-line paths for comets, because they assume the earth's annual motion, and finds the Astronomia nova and the Harmonice mundi hard going. The original is in the Bibliothèque de l'Observatoire, Paris (B, 1, 9; 89, 9. B. 24). Printed in extracts in Nova Kepleriana 4, ed. Walther von Dyck and Max Caspar, Abhandlungen der Bayerischen Akademie der Wissenschaften, Math.-naturw. Abteilung 31, no. 1 (Munich, 1927), 106–107.
English translation of the Latin extracts printed in Nova Kepleriana 4 (1927), made for Plain Old Text. Each paragraph translates the corresponding extract of the original; the omission marks (…) are the 1927 editors’. Italics follow the editors’ emphasis.
Kepler’s books arrived in good time, but I am still waiting for the title page of the Comet that you promised me. I am greatly and dutifully obliged to you.
This Author’s books on comets are written most ingeniously to establish that comets move in straight lines. Even so, I cannot subscribe to this motion of comets, and I have two reasons. The first is that before anything else he assumes the earth’s annual motion as clearly proved, when the case is still before the judge. Though I believe in the earth’s daily motion, I cannot bring myself to accept the annual one. …
The other reason that keeps me from embracing the straight-line motion of comets is that a straight path can in no way represent a comet’s own motion where it grows beyond a semicircle. …
The theorems of Kepler cited above suppose a marvellous motion of the comet, never dreamt of or heard of in any comet. Theorem XXI, obscure enough, he illustrated with no diagram; but I have overcome its obscurity, and I send you a diagram of it here, agreeing with every word of his. Weigh it carefully, I beg you, and see the comet’s rabid leaps one moment and idle standstills the next. Who (confound it!) since the world was made ever saw or heard of such a thing? Kepler seems, then, to sing the triumph before the victory. … But I shall stop here, fearing to offend you, who think so highly of Kepler, with this criticism. Whatever I have done, I have done as a student of astronomical truth, which I believe is a friend to you above all your friends.An echo of the proverb amicus Plato, sed magis amica veritas: Plato is a friend, but truth a greater one.
… His work on Mars demands a man free of every other thought, and that not for one day but for a whole year, until it can be grasped throughout. I would dare to say that the man has worked most zealously at being obscure and intricate …
Kepler’s Harmony of the World I have not yet read through attentively. This work seems as obscure as the one on Mars …