Introduction
A major contribution to Western thought was the publication in 1543 of De revolutionibus orbium coelestium, libri VI (Eng. trans., On the Revolutions of the Celestial Spheres, 1952; Latin reprint, 1965) by Copernicus, Polish astronomer, who is noted for the Copernican theory of the heavens. By attributing to the Earth a daily motion around its own axis and a yearly motion around the stationary Sun, Copernicus developed an idea that had far-reaching
implications for the rise of modern science. Henceforth, the Earth could no longer be considered the centre of the cosmos; rather, as one celestial body among many, it became subject to mathematical description.
Early life and education.
Nicolaus Copernicus (in Polish Mikolaj Kopernik, in German-Prussian dialect Niklas Koppernick) was born on February 19, 1473, at Torun, near the Vistula River in eastern Poland, where his father was a merchant of social standing. In 1491 Copernicus entered the University of Krakуw, where he became interested in the study of astronomy; he probably returned home in 1494 (or 1496). His maternal uncle, Lucas Waczenrode, newly elected bishop of Ermeland, wanted him to enter the canonry of Frauenburg in order to secure lifelong financial independence. While waiting for a vacancy to occur, he was sent by his uncle in 1497 for further training to the University of Bologna, where he associated himself with the German students.
For three and a half years Copernicus studied the Greek language, mathematics, and the writings of Plato; he also became further acquainted with the astronomical thought of the day. In Bologna he also made his first recorded observation of the heavens, an occultation (overlapping, or eclipse) of the star Aldebaran by the Moon on March 9, 1497; the light of the former was shut off by the Moon. The same year he was elected (by proxy) a canon of Frauenburg. He travelled to Rome in 1500 for the great jubilee celebration and may have given informal lectures in mathematics there. In 1501 he briefly visited Frauenburg to claim his post on the cathedral staff, returning promptly to Italy under special leave of absence to continue his studies at the University of Padua. There, enrolled with other Polish students, he studied both law and medicine. Except for a short interruption in 1503, when he was granted the degree of doctor of canon law by the University of Ferrara, he spent almost four years in Padua.
On returning to Poland in 1503, he visited Krakуw and later acted as adviser to his uncle until the latter's death in 1512. Copernicus settled permanently at Frauenburg, where he acted as representative of the cathedral chapter, his medical skill being used particularly in aid of the indigent.
As a result of his studies in Krakуw and Padua, Copernicus may be said to have mastered all the knowledge of the day in mathematics, astronomy, medicine, and theology. Copernicus appears to have planned a systematic program of astronomical work. Although he did not make extensive observations, he did enough to enable him to recalculate the major components of the supposed orbits of the Sun, Moon, and planets around the Earth. He published 27 such observations made during the years 1497-1529, and a few others have been found entered in books in his private library. He also published for his uncle in 1509 a Latin translation of Greek verses of Theophylactus, a Byzantine poet of the 7th century AD, and from 1519 to 1528 prepared an exposition of the principles of currency reform for
certain Polish provinces; the latter was not published in Warsaw, however, until 1816.
Copernicus' fame as an industrious student of astronomy rapidly increased, and in 1514 he was invited to give his opinion on calendar reform, which was then being considered by the Lateran Council, a general meeting of the church authorities. He refused to express any firm views, for he felt that the positions of the Sun and
Moon were not known with sufficient accuracy to permit a proper reassessment.
Dissatisfaction with the Ptolemaic system.
Yet, as his studies progressed, Copernicus became increasingly dissatisfied with the Ptolemaic system of astronomy. He was not alone in this dissatisfaction; indeed, he himself said that the many divergent views prevalent in his day gave him cause for profound thought. Ptolemy's system, which contained not only original work but also a synthesis of the views of previous Greek philosophers, was basically geocentric and circular in conception. By the 16th century this geocentric interpretation of the heavens had become firmly entrenched in astronomical thought, virtually as an article of faith. Although certain Greek philosophers had suggested, as far back as the 3rd century BC, that the Sun--and not the Earth--was the centre of the universe, their ideas had not been widely accepted. Difficulties
had arisen when ancient astronomers sought to account for the accumulated observations of the Sun, Moon, and planets. Accordingly, Ptolemy in the 2nd century AD had devised an elaborate geocentric model of the heavens composed of large circles, called deferents, and small circles, called epicycles. Each planet rode on
the circumference of an epicycle, the centre of which revolved on the deferent. Ptolemy used this system to account for observed irregularities of the planets, such as changes in brightness, and particularly for their puzzling retrogressive motions, when they seemed to stop and move backward and forward in a loop. Moreover, to account for observed variations in velocity, Ptolemy introduced the equant, which was an imaginary point in space where uniform, circular
speed would indeed be observed. This system enabled astronomers to account for the phenomena and to make predictions. As observations in succeeding centuries became more accurate, however, it became increasingly difficult to compute the future positions of the heavenly bodies, and much of the flexibility and elegance of the Ptolemaic system was thereby lost.
