Coming of Age in the Milky Way by Timothy Ferris

immortal souls,
But whilest this muddy vesture of decay
Doth grossly close it in, we cannot hear it. 26
     
    The churches of the day rang with approximations of the music of the spheres. The plainsongs and chants of the medieval cathedrals were being supplanted by polyphony, the music of many voices that would reach an epiphany in the fugues—the word
fugue
means “flight”—of Johann Sebastian Bach. For Kepler, polyphony in music was a model for the voices sung by the planets as they spun out their Pythagorean harmonies: “The ratio of plainsong or monody … to polyphony,” he wrote,
    is the same as the ratio of the consonances which the single planets designate to the consonances of the planets taken together….
    … The movements of the heavens are nothing except a certain ever-lasting polyphony (intelligible, not audible)…. Hence it is no longer a surprise that man, the ape of his Creator, should finally have discovered the art of singing polyphonically,which was unknown to the ancients, namely in order that he might play the everlastingness of all created time in some short part of an hour by means of an artistic concord of many voices and that he might to some extent taste the satisfaction of God the Workman with His own works, in that very sweet sense of delight elicited from this music which imitates God. 27
     
    Kepler’s interest in astronomy, like Tycho’s, dated from his boyhood, when his mother took him out in the evening to see the great comet of 1577 and, three years later, to behold the sanguine face of the eclipsed moon. He was introduced to heliocentric cosmology at the University of Tübingen, by Michael Mastlin, one of the few Copernican academics of his day. Attracted to it partly out of mystical, Neoplatonic motives like those that had inspired Copernicus himself, Kepler wrote of sunlight in terms that would have brought a smile to the countenance of Marsilio Ficino:
    Light in itself is something akin to the soul…. And so it is consonant that the solar body, wherein the light is present as in its source, is endowed with a soul which is the originator, the preserver, and the continuator. And the function of the sun in the world seems to persuade us of nothing else except that just as it has to illuminate all things, so it is possessed of light in its body; and as it has to make all things warm, it is possessed of heat; as it has to make all things live, of a bodily life; and as it has to move all things, it itself is the beginning of the movement; and so it has a soul. 28
     
    But Kepler’s penchant for Platonic ecstasy was wedded to an acid skepticism about the validity of all theories, his own included. He mocked no thinker more than himself, tested no ideas more rigorously than his own. If, as he avowed in 1608, he was to “interweave Copernicus into the revised astronomy and physics, so that either both will perish or both be kept alive,” he would need more accurate observational data than were available to Ptolemy or to Copernicus. Tycho had those data. “Tycho possesses the best observations,” Kepler mused. “… He only lacks the architect who would put all this to use according to his own design.” 29 Tycho was “superlatively rich, but he knows not how to make proper use of it as is the case with most rich people. Therefore, one must tryto wrest his riches from him.” 30 Suiting action to intention, Kepler wrote adoring letters to Tycho, who in reply praised his theories as “ingenious” if rather too a priori, and invited him to come and join the staff at Benatek Castle.
    There the two quarreled constantly. Tycho, justly fearful that the younger and more incisive Kepler would eclipse him, played his cards close to his chest. “Tycho did not give me the chance to share his practical knowledge,” Kepler recalled, “except in conversation during meals, today something about the apogee, tomorrow something about the nodes of another planet.” 31 Kepler threw fits and