in the Dedication to the Pope (dated 1543) his work had been formulated not merely nine years but for "more than three nines of years." It had not been neglected all this time, however, as the original MS. (now in the Prague Library) with its innumerable changes and corrections shows how continually he worked over it, altering and correcting the tables and verifying his statements.
Copernicus was a philosopher. He thought out a new explanation of the world machine with relatively little practical work of his own, though we know he controlled his results by the accumulated observations of the ages. His instruments were inadequate, inaccurate and out of date even in his time, for much better ones were then being made at Nürnberg; and the cloudy climate of Ermeland as well as his own active career prevented him from the long-continued, painstaking observing, which men like Tycho Brahe were to carry on later. Despite such handicaps, because of his dissatisfaction with the complexities and intricacies of the Ptolemaic system and because of his conviction that the laws of nature were simple and harmonious, Copernicus searched the writings of the classic philosophers, as he himself tells us, to see what other explanation of the universe had been suggested. "And I found first in Cicero that a certain Nicetas had thought the earth moved. Later in Plutarch I found certain others had been of the same opinion." He quoted the Greek referring to Philolaus the Pythagorean, Heraclides of Pontus, and Ecphantes the Pythagorean. As a result he began to consider the mobility of the earth and found that such an explanation seemingly solved many astronomical problems with a simplicity and a harmony utterly lacking in the old traditional scheme. Unaided by a telescope, he worked out in part the right theory of the universe and for the first time in history placed all the then known planets in their true positions with the sun at the center. He claimed that the earth turns on its axis as it travels around the sun, and careens slowly as it goes, thus by these three motions explaining many of the apparent movements of the sun and the planets. He retained, however, the immobile heaven of the fixed stars (though vastly farther off in order to account for the non-observance of any stellar parallax), the "perfect" and therefore circular orbits of the planets, certain of the old eccentrics, and 34 new epicycles in place of all the old ones which he had cast aside. He accepted the false notion of trepidation enunciated by the Arabs in the 9th century and later overthrown by Tycho Brahe. His calculations were weak. But his great book is a sane and modern work in an age of astrology and superstition. His theory is a triumph of reason and imagination and with its almost complete independence of authority is perhaps as original a work as an human being may be expected to produce.
Copernicus was extremely reluctant to publish his book because of the misunderstandings and malicious attacks it would unquestionably arouse. Possibly, too, he was thinking of the hostility already existing between himself and his Bishop, Dantiscus, whom he did not wish to antagonize further. But his devoted pupil and friend, Rheticus, aided by Tiedeman Giese, Bishop of Culm and a lifelong friend, at length (1542) persuaded him. So he entrusted the matter to Giese who passed it on to Rheticus, then connected with the University at Wittenberg as professor of mathematics. Rheticus, securing leave of absence from Melancthon his superior, went to Nürnberg to supervise the printing. This was done by Petrejus. Upon his return to Wittenberg, Rheticus left in charge Johann Schöner, a famous mathematician and astronomer, and Andreas Osiander, a Lutheran preacher interested in astronomy. The printed book was placed in Copernicus's hands at Frauenburg on May 24th, 1543, as he lay dying of paralysis.
Copernicus passed away that day in ignorance that his life's work appeared before the world not as a truth but as an hypothesis; for