They went on to another tavern, and another. The Serb got lost along the way, and then Felix and the dwarf reeled off arm in arm with the bawds into the darkness, and Krump and the astronomer were left to stagger home up the Hradcany, falling and shouting and singing tearful songs of Württemberg their native land. In the small hours, his elusive quarters located at last, Kepler, a smouldering red eye in his mind fixed on the image of a romping whore, attempted with much shushing and chuckling to negotiate Barbara's rigid form into an exotic posture, for what precise purpose he had forgotten when he woke into a parched and anguished morning, though something of the abandoned experiment was still there in the line of her large hip and the spicy tang of her water in the earthen pot under the bed. She would not speak to him for a week.
Later that day, when the fumes of the charnel house had dispersed in his head, he brought out and contemplated, like a penniless collector with a purloined treasure, the understanding that had been given to him that the principle of uniform orbital velocity was a false dogma. It was the only, the obvious answer to the problem of Mars, of all the planets probably, and yet for two thousand years and more it had resisted the greatest of astronomy's inquisitors. And why had this annunciation been made to him, what heaven-hurled angel had whispered in his ear? He marvelled at the process, how a part of his mind had worked away in secret and in silence while the rest of him swilled and capered and lusted after poxed whores. He experienced an unwonted humility. He must be better now, behave himself, talk to Barbara and listen to her complaints, be patient with the Dane, and say his prayers, at least until the advent of new problems.
They were not long in coming. His rejection of uniform velocity threw everything into disarray, and he had to begin all over again. He was not discouraged. Here was real work, after all, fully worthy of him. Where before, in the Mysterium, there had been abstract speculation, was now reality itself. These were precise observations of a visible planet, coordinates fixed in time and space. They were events. It was not by chance he had been assigned the study of Mars. Christian Longberg, that jealous fool, had insisted on keeping the lunar orbit; Kepler laughed, glimpsing there too the quivering tips of angelic wings, the uplifted finger. For he knew now that Mars was the key to the secret of the workings of the world. He felt himself suspended in tensed bright air, a celestial swimmer. And seven months were becoming seventeen.
Tycho told him he was mad: uniform velocity was a principle beyond question. Next he would be claiming that the planets do not move in perfect circles! Kepler shrugged. It was the Dane's own observations that had shown the principle to be false. No no no, and Tycho shook his great bald head, there must be some other explanation. But Kepler was puzzled. Why should he seek another answer, when he had the correct one? There stood at the hatch of his mind an invoice clerk with a pencil and slate and a bad liver, who would allow no second thoughts. Tycho Brahe turned away; what little chance there had been that this Swabian lunatic would solve Mars for him was gone now. Kepler plucked at him, wait, look-where is my compass, I have lost my compass-the thing was as good as done! Even assuming a variable rate of speed, to define the orbit he had only to determine the radius of its circle, the direction relative to the fixed stars of the axis connecting aphelion and perihelion, and the position on that axis of the sun, the orbital centre, and the punctum equans, which for the moment he would retain, as a calculating device. Of course all this could only be done by a process of trial and error, but… but wait! And Tycho swept away, muttering.
He made seventy attempts. At the end, out of nine hundred pages of closely-written calculations, came a set of values which gave, with an error of only two minutes of arc, the correct position of Mars according to the Tychonic readings. He clambered up out of dreadful depths and announced his success to anyone who would listen. He wrote to Longberg in Denmark, demanding settlement of their wager. The fever which he had held at bay with promises and prayers took hold of him now like a demented lover. When it had spent itself, he returned to his calculations to make a final test. It was only play, really, a kind of revelling in his triumph. He chose another handful of observations and applied them to his model. They did not fit. Arrange matters as he would, there was always an error of eight minutes of arc. He plodded away from his desk, thinking of daggers, the poison cup, a launching into empty air from a high wall of the Hradcany. And yet, in a secret recess of his heart, a crazy happiness was stirring at the prospect of throwing away all he had done so far and starting over again. It was the joy of the zealot* in his cell, the scourge clasped in his hand. And seventeen months were to become seven years before the thing was done.
His overloaded brain began to throw off sparks of surplus energy, and he conceived all kinds of quaint ingenious enterprises. He developed a method of measuring the volume of wine casks by conic section. The keeper of the Emperor's cellars was charmed. He tested his own eyesight and made for himself an elaborate pair of spectacles from lenses ground in Linz by his old friend Wincklemann. The prosaic miracle of water had always fascinated him; he set up water clocks, and designed a new kind of pump which impressed the imperial engineers. Others of his projects caused much hilarity among the Brahes. There was his design for an automatic floor-sweeper, worked by suction power from a double-valved bellows attached to the implement's ratcheted wheels. He consulted the scullery maids on a plan for a laundry machine, a huge tub with paddles operated by a treadle. They ran away from him, giggling. These were amusing pastimes, but at the end of the day always there was the old problem of Mars waiting for him.
He liked to work at night, savouring the silence and the candleglow and the somehow attentive darkness, and then the dawn that always surprised him with that sense of being given a glimpse of the still new and unsullied other end of things. In the Curtius house he had burrowed into a little room on the top floor where he could lock himself away. The summer passed. Early one October morning he heard a step outside his door, and peering out spied Tycho Brahe standing in the corridor, his arms folded, gazing down pensively at his large bare feet. He was in his nightshirt, with a cloak thrown over his shoulders. Behind him, by the far wall, Jeppe the dwarf was creeping. They had the air of weary and discouraged searchers after some hopelessly lost small thing. Tycho looked up at Kepler without surprise.