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Science and Scientists The Copernican Revolution The Science Copernicus's work De revolutionibus (On the Revolutions of the Heavenly Spheres) replaced the ancient Greek idea of an Earth-centered solar system, the geocentric model, with the modern heliocentric model that placed the Sun at the center of the solar system. The Scientists Nicolaus Copernicus (1473-1543), astronomer Rheticus (1514-1574), Austrian astronomer and mathematicianRheticus> Andreas Osiander of Wittenberg (1498-1552), Protestant scholar who oversaw publication of De revolutionibus Seeking the Center of the Universe Since at least ancient times, humans have been fascinated with the motion of the objects in the sky. They recognized that most of these objects, the stars in particular, appeared to rotate in circles around the fixed pole star, Polaris, in the Northern Hemisphere, as if the stars were fixed to a rigid sphere that surrounds the Earth and that rotated once each day. More than two thousand years ago, humans recognized that there were several unusual objects in the sky, called the wanderers, because they appeared to move relative to the stars. In addition to the Sun and the Moon, these wanderers included five planets visible without telescopes: Mercury, Venus, Mars, Jupiter, and Saturn. The paths of these wanderers were observed and recorded. Astronomers wanted to know what caused the motion of the wanderers and how this motion could be predicted, while astrologers believed the positions of these wanderers influenced the daily lives of individuals on Earth. The Ptolemaic Model Ancient Greek philosophers tried to develop models for the motion of the wanderers that would be in accord with all past measurements and allow prediction of their future positions. The most successful among them, the Greek philosopher Ptolemy (c. 100-178), constructed a model in which all the objects in the sky moved around the Earth on progressively larger concentric circles. This model, however, did not accurately predict the motions of the wanderers, so Ptolemy fixed the planets to other circles that rolled around larger concentric circles. The Ptolemaic model, as it came to be called, was later adopted by Roman Catholic religious leaders because it was consistent with their idea that humans were a "special creation" of God, and thus it seemed appropriate for humankind to occupy a "special position" at the center of all creation. The Ptolemaic model dominated religious thinking in Europe as Europe emerged from the Middle Ages. A Dangerous New Model This idea that the Earth occupied a special position in the solar system was challenged by Nicolaus Copernicus, an astronomer and a Roman Catholic canon of the Church. Copernicus, who was born in the Prussian city of Thorn (modern Toru{nacute}, Poland), received his advanced education in Italy, where he studied astronomy, mathematics, and medicine and received a doctor's degree in canon law. Copernicus's long service in the religious office as canon of Ermland made him an odd candidate to defy Church teachings, but his study of astronomy led him on a path of conflict with the Church. Copernicus was an avid observer who compiled twenty years of observations of the positions of the wanderers in the sky. By combining his observations with those recorded by earlier observers, Copernicus was able to observe flaws in the predictions of Ptolemy's model. By 1513, when Copernicus returned to Poland from Italy, he had formulated his own model of the motion in the solar system, reviving an idea proposed more than seventeen hundred years earlier by Greek astronomer Aristarchus of Samos. In the Copernican model, the Sun was stationary at the center of the solar system, with the Earth and the other planets moving around the Sun in concentric circular orbits. Copernicus wrote: "As if seated on a royal throne, the Sun rules the family of planets as they circle around him." The Earth, in this model, was reduced to the status of one of the several planets circling around the Sun. It held no special status from a location at the center of all creation. Copernicus circulated his idea among his friends in a manuscript entitled Commentariolus (1514; English translation, 1939). This manuscript asserted that "The center of the Earth is not the center of the universe. . . . All the spheres revolve around the Sun, as if it were in the middle of everything." Copernicus recognized, however, that his idea was contrary to the teaching of the Church. Therefore, he refrained from widespread distribution of this manuscript. Nevertheless, Pope Clement VII became aware of Commentariolus in 1533 but took no action to suppress Copernicus's idea. The first serious attack on Copernicus's model came from Protestant religious leaders. Martin Luther said of Copernicus, "This fool wants to turn the whole art of astronomy upside down! But as the Holy Scripture testifies Joshua bade the Sun to stand still, not the earth." Luther's appeal to Scripture, and thus faith in the word of God, to explain the behavior of nature was in sharp contrast to Copernicus's belief that the behavior of natural objects could be understood by a combination of observation or experimentation and reasoning in what has come to be called the scientific method. De revolutionibus Perhaps because of the attacks by religious leaders, Copernicus did not publish the full description of his idea, in De revolutionibus orbium coelestium (1543; On the Revolutions of the Heavenly Spheres, 1952; better known as De revolutionibus), until 1543. Georg Joachim, called Rheticus, a professor of mathematics, had heard of Copernicus's idea and then journeyed to Ermland in 1539 to learn more about it from Copernicus himself. Rheticus encouraged Copernicus, who was nearing seventy years of age, to commit his ideas to writing. Copernicus agreed. He divided the text of De revolutionibus into six parts: the first, and most controversial, concerned the arrangement of objects within the solar system; the second contained his new star catalog; the third covered precession, that is, how the motion of the Earth's pole causes the fixed star about which the sky appears to rotate to change with time; the fourth discussed the Moon's motions; and the fifth and sixth examined the motions of the planets. The book was typeset in Nuremberg, Germany, initially under the supervision of Rheticus. Andreas Osiander, who took over supervision when Rheticus left Nuremberg, wrote to Copernicus in 1541, urging him to avoid a direct attack on the teachings of the Church about the arrangement of the solar system. Osiander suggested the introduction to De revolutionibus should indicate that either the hypothesis of Copernicus or that of Ptolemy could explain the observed planetary motion. Copernicus rejected this, but Osiander removed the introduction Copernicus had written and substituted his own preface, which emphasized that De revolutionibus presented a hypothesis. Since Osiander did not sign the new preface, readers generally assumed it was written by Copernicus, who did not see a copy of the printed work until he was near death in 1543. Osiander's preface might have kept Roman Catholic theologians from attacking the book for some time. De revolutionibus was not placed on the Index librorum prohibitorum (the Index of Prohibited Books) of the Roman Catholic Church until 1616, when the Holy Office in the Vatican began its investigation of the astronomer Galileo Galilei, who had spoken openly of his admiration for the work of Copernicus. At that time the Holy Office pronounced the idea of a Sun-centered solar system to be "foolish and philosophically absurd." In the intervening years, Roman Catholic leaders faced another challenge to the special status of the Earth and of humankind. Giordano Bruno, an Italian astronomer, philosopher, and Catholic cleric, was burned alive in 1600 for suggesting that the universe might contain other inhabited worlds. Impact Although Christian religious leaders rejected Copernicus's work, it was widely adopted by astronomers and astrologers throughout Europe as the method to predict planetary positions because of the simplicity of calculating the positions using this method. The publication of De revolutionibus began what is called the Copernican Revolution. Copernicus's work influenced later European astronomers, including Johannes Kepler and Galileo Galilei, and set the stage for the adoption of the Sun-centered model of the solar system by the scientific world. Kepler replaced the concentric circles of the Copernican model with elliptical paths for the planets and removed all the remaining discrepancies between observed planetary positions and the predictions of the Sun-centered model. Galileo, whose Dialogo sopra i due massimi sistemi del mondo, tolemaico e copernicano (1632; Dialogue Concerning the Two Chief World Systems, Ptolemaic and Copernican, 1661) was published in 1632, firmly established the Sun-centered solar system in the minds of European astronomers. See Also Gravitation: Newton; Heliocentric Universe; Herschel's Telescope; Kepler's Laws of Planetary Motion; Medieval Physics. Further Reading Barrett, Peter. Science and Theology Since Copernicus: The Search for Understanding. Reprint. Poole, Dorset, England: T&T Clark, 2003. Blumenberg, Hans. The Genesis of the Copernican World. Translated by Robert M. Wallace. Cambridge, Mass.: MIT Press, 1987. Durham, Frank, and Robert D. Purrington. Frame of the Universe. New York: Cambridge University Press, 1983. Gingerich, Owen. The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus. New York: Walker, 2004. Henry, John. Moving Heaven and Earth: Copernicus and the Solar System. Cambridge, England: Icon, 2001. Kuhn, Thomas S. The Copernican Revolution. Cambridge, Mass.: Harvard University Press, 1966. George J. Flynn |
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