Free Coming of Age in the Milky Way by Timothy Ferris Page A

move the center of the universe to a point a little away from the sun. Nor did it make consistently more accurate predictions, even in its wretchedly compromised form; for many applications it was less useful.

     
    Copernicus’s model of the solar system is generally portrayed in simplified form, as in this illustration based upon one in his
De Revolutionibus
. In its details, however, it was as complex as Ptolemy’s geocentric model.
     
    This, in retrospect, was the tragedy of Copernicus’s career—that while the beauty of the heliocentric hypothesis convinced him that the planets ought to move in perfect circles around the sun, the sky was to declare it false. Settled within the stone walls of Frauenburg Cathedral, in a three-story tower that afforded him a view of Frisches Haff and the Gulf of Danzig below and the wide (though frequently cloudy) sky above—“the most remote corner of the earth,” 11 he called it—Copernicus carried out his sporadic astronomical observations, and tried, in vain, to perfect the heliocentric theory he had outlined while still a young man. For decades he turned it over in his thoughts, a flawed jewel, luminous and obdurate. It would not yield.
    As Darwin would do three centuries later, Copernicus wrote and privately circulated a longhand sketch of his theory. He called it the “ballet of the planets.” It aroused interest among scholars, but Copernicus published none of it. He was an old man before he finally released the manuscript of
De Revolutionibus
to the printer, and was on his death bed by the time the final page proofs arrived.
    One reason for his reluctance to publish was that Copernicus, like Darwin, had reason to fear censure by the religious authorities. The threat of papal disapproval was real enough that the Lutheran theologian Andreas Osiander thought it prudent to oil the waters by writing an unsigned preface to Copernicus’s book, as if composed by the dying Copernicus himself, reassuring its readers that divine revelation was the sole source of truth and that astronomical treatises like this one were intended merely to “save the phenomena.” Nor were the Protestants any more apt to kiss the heliocentric hem. “Who will venture to place the authority of Copernicus above that of the Holy Spirit?” thundered Calvin, 12 and Martin Luther complained, in his voluble way, that “this fool wishes to reverse the entire science of astronomy; but sacred Scripture tells us that Joshua commanded the sun to stand still, and not the earth.” 13 *
    The book survived, however, and changed the world, for much the same reason that Darwin’s
Origin of Species
did—because it was too technically competent for the professionals to ignore it. In addition to presenting astronomers with a comprehensive, original, and quantitatively defensible alternative to Ptolemy,
De Revolutionibus
was full of observational data, much of it fresh and some of it reliable. Consequently it was consulted regularly by astronomers—even by non-Copernicans like Erasmus Reinhold, who employed it in compiling the widely consulted
Prutenic Tables
—and thus remained in circulation for generations.
    To those who gave it the benefit of the doubt, Copernicanism offered both a taste of the immensity of space and a way to begin measuring it. The minimum radius of the Copernican sphere of stars (given the unchanging brightnesses of the zodiacal stars) was estimated in the sixteenth century to be more than 1.5 million times the radius of the earth. This represented an increase in the volume of the universe of at least 400,000 times over al-Farghani’s Ptolemaic cosmos. The maximum possible size of the Copernican universe was indefinite, and might, Copernicus allowed, be infinite: The stars, he wrote, “are at an immense height away,” and he expressed wonderment at “how exceedingly vast is the godlike work of the Best and Greatest Artist!” 14
    Interplanetary distances in Ptolemy were arbitrary;