It is a book that is not easy to understand, and which assumes not only a clever head, but also a particularly intellectual alertness amp; an extraordinary desire to learn the causes of things. In it I have set about clearing up the laws by which the Galilean telescope works. (I might add, that in this task I have had scant help, as you would expect, from him whose name is given to the new instrument.) It may be said, I believe, that between this book, and my Astronomia pars optica of 1604, I have laid the foundations of a new science. Whereas, however, the earlier book was a gay amp; speculative venturing upon the nature oflight and the working of lenses, the Dioptrice is a sober setting out of rules, in the manner of a geometry manual. O, that I could send you a copy, for I am eager to hear your opinion. Damn these penny-pinchers! It is composed of 141 rules, schematically divided into definitions, axioms, problems amp; propositions. I begin with the law of refraction, the expression of which, I confess, is not much less inexact than previously, although I have managed not too badly by virtue of the fact that the angles of incidence dealt with are very small. I have also set out a description of total reflection of light rays in a glass cube amp; three-sided prism. As well, of course, I have gone more deeply than ever into the matter of lenses. In Problem 86, in which I demonstrate how, with the help of two convex lenses, visible objects can be made larger amp; distinct but inverted, I believe I have defined the principle upon which the astronomical telescope is based. Also, by treating of the suitable combinations of a converging lens with a diverging lens in place of a simple object lens, I have shown the way toward a large improvement upon the Galilean telescope. This will not please the Paduan, I think. So you see, my dear Doctor, how far ahead I have pressed in our science. I think, indeed, that I have gone as far as it is possible to go, and I confess, with some regret, that I am losing interest in the subject. The telescope is a wonderfully useful instrument, and will no doubt prove of great service to astronomy. For my part, however, I grow tired rapidly of peering into the sky, no matter how wonderful the sights to be seen there. Let others map these new phenomena. My eyesight is bad. I am, I fear, no Columbus of the heavens, but a modest stay-at-home, an armchair dreamer. The phenomena with which I am already familiar are sufficiently strange amp; wonderful. If the new stargazers discover novel facts which will help to explain the true causes of things, fair enough; but it seems to me that the real answers to the cosmic mystery are to be found not in the sky, but in that other, infinitely smaller though no less mysterious firmament contained within the skull. In a word, my dear friend, I am old-fashioned; as I am also,
yours, Kepler
Aedes Cramerianis Prague October 1610
Georg Fugger: at Venice
Let me yet again offer you my warm amp; sincerest thanks for your loyal support of me amp; my work. I thank you also for your kind words regarding my Dissertatio cum nuncio sidero, and your efforts to promote in Italy the views expressed in that little work. Yet, once more, I must protest at your too enthusiastic championing of me against Galileo. I do not oppose him. My Dissertatio does not, as you put it, rip the mask from his face. If you read my pamphlet with attention, you will clearly see that I have, with reservations, given my blessing to his findings. Does this surprise you? Are you, perhaps, disappointed? How, you will ask, can I be warm toward someone who will not even deign to write to me directly? But as I have said before, I am a lover of truth, and will welcome it amp; celebrate it, whatever quarter it may come from. Sometimes I suspect that those who concern themselves in this squabble over the reliability of Galileo's findings, may in fact care less for the objective truth, than they do for getting hold of ammunition to use against an arrogant amp; clever man, and who is not subtle nor sly enough to put on a false humility in order to please the general. That young clown Martin Horky, Magini's assistant, in his so-called Refutation, had the gall to quote me-no, to misquote me, in support of his imbecile gibes against Galileo. I lost no time in terminating my acquaintance with the young pup.
Still, I confess Galileo is difficult to love. You know, in all this time he has written to me only one letter. For the rest, for news of his further discoveries, and even for word of his reactions to my Dissertatio (which after all was an open letter directed to him!), I must depend on second-hand accounts from the Tuscan Ambassador here, and other suchlike. And then, how secretive amp; suspicious the Paduan is! When he does send me a crumb, he hides it inside the most impossible amp; unnecessary of disguises. For instance, last summer he sent, again through the ambassador, the following message: Smaismirmilmepoetaleumibunenugttaurias. At first I was amused: after all, I myself sometimes play with anagrams amp; word games of this sort. However, when I set about deciphering the code, I was nearly driven out of my mind. The best I could manage was a bit of barbaric Latin verse that made no sense. It was not until last month-when Galileo had heard that the Emperor himself was curious-that the solution was furnished at last: hidden in that jumble was the announcement of the discovery of what appear to be two small moons circling Saturn! Now has come another puzzle, which seems to speak of a red spot in Jupiter which rotates mathematically. A red spot, I ask myself, or a red herring? How is one to respond to this kind of foolery? I shall scald the fellow's ears with my next letter.
And yet, what a splendid amp; daring scientist he is! O, that I could journey to Italy to meet this Titan! I will not have him sneered at, you know, in my presence. You mention how Magini amp; the dreadful Horky (nice name for him), and even you yourself, were delighted with the passage in the Dissertatio in which I mention that the principle of the telescope was set out 20 years ago by della Porta, and also in my own work on optics. But Galileo has not claimed the invention of the instrument! Besides, these anticipations were purely theoretical, and cannot dimmish Galileo's fame. For I know what a long road it is from the theoretical concept to its practical achievement, from the mention of the Antipodes in Ptolemy to Columbus's discovery of the New World, and even more from the two-lensed instruments used in this country to the instrument with which Galileo has penetrated the skies.
Let me state, then, clearly and without equivocation, that my Dissertatio is not the masterpiece of irony which so many take it to be (would that I possessed such subtlety!), but an open amp; express endorsement of Galileo's claims. Thank you for the oranges. Though I regret to say the packaging was damaged, and they had all gone bad.
Your servant, Sir, Joh: Kepler
Prague September 1610
Professor Gio. A. Magini: at Bologna
Excellent news, my dear sir: the Elector Ernst of Cologne, who is my patron, and who has been here throughout the summer for the Council of princes, returned last week from a brief visit to Vienna and brought with him a telescope, the very one which Galileo had himself presented to the Archduke of Bavaria. Thus the mean-spirited Paduan is frustrated in his jealousy by the kindness of my friends amp; patrons. Perhaps there is justice in the world, after all.