Zero by Charles Seife Page B

heavens—were made of light, airy stuff, but it also meant that any people in the heavens would naturally fall to Earth. Thus creatures could only inhabit the nutmeat in the center of the nutshell cosmos. Having other planets with life on them was as silly as having a sphere with two centers.
    When Tempier declared that the omnipotent God could create a vacuum if he so desired, Tempier insisted that God could break any Aristotelian law. God could create life on other worlds if he wished. There could be thousands of other Earths, each teeming with creatures; it was certainly within God’s power, whether Aristotle agrees or not.
    Nicholas of Cusa was bold enough to say that God must have done so. “The regions of the other stars are similar to this,” he said, “for we believe that none of them is deprived of inhabitants.” The sky was littered with an infinite number of stars. The planets glowed in the heavens; the moon and the sun each glowed with light. Why couldn’t the stars in the sky be planets or moons or suns on their own? Maybe Earth glows brightly in their heavens, just as they glow in ours. Nicholas was sure that God had, indeed, created an infinite number of other worlds. Earth was no longer at the center of the universe. Yet Nicholas was not declared a heretic, and the church didn’t react to the new idea.
    In the meantime another Nicholas turned Cusa’s philosophy into a scientific theory. Nicolaus Copernicus showed that Earth is not the center of the universe. It revolves around the sun.
    A Polish monk and a physician, Copernicus learned mathematics so he could cast astrological tables, the better to cure his patients with. Along the way, Copernicus’s dabblings with the planets and stars showed him how complicated the old Greek system of tracking the planets was. Ptolemy’s clockwork heavens—with Earth at the center—were extremely accurate. However, they were terribly complex. Planets course around the sky throughout the year, but every so often they stop, move backward, and then shoot ahead once more. To account for the planets’ bizarre behavior, Ptolemy added epicycles to his planetary clockwork: little circles within circles could explain the backward, or retrograde , motion of the planets (Figure 19).
    The power of Copernicus’s idea was in its simplicity. Instead of placing Earth at the center of the universe filled with epicycle-filled clockworks, Copernicus imagined that the sun was at the center instead, and the planets moved in simple circles. Planets would seem to zoom backward as Earth overtook them; no epicycles were needed. Though Copernicus’s system didn’t agree with the data completely—the circular orbits were wrong, though the heliocentric idea was correct—it was much simpler than the Ptolemaic system. The earth revolved around the sun. Terra non est centra mundi.
    Nicholas of Cusa and Nicolaus Copernicus cracked open the nutshell universe of Aristotle and Ptolemy. No longer was the earth comfortably ensconced in the center of the universe; there was no shell containing the cosmos. The universe went on into infinity, dotted with innumerable worlds, each inhabited by mysterious creatures. But how could Rome claim to be the seat of the one true Church if its authority could not extend to other solar systems? Were there other popes on other planets? It was a grim prospect for the Catholic Church, especially since it was beginning to have trouble with its subjects on even its own world.
    Copernicus published his magnum opus on his deathbed—in 1543, just before the church started clamping down on new ideas. Copernicus’s book, De Revolutionibus, was even dedicated to Pope Paul III. However, the church was under attack. As a result, the new ideas—the questioning of Aristotle—could no longer be tolerated.
    The attack on the church began in earnest in 1517, when a constipated German monk nailed a list of