Nicholaus Copernicus, the founder of modern astronomy, was born on February 19, 1473 in Thorn, Poland to a well-to-do family. When he was only 10 years old, he lost his father, a prosperous merchant. His maternal uncle stepped in to raise him.
Through his uncle's influence, he was able to enter the University of Cracow, in 1491, which was famous for its mathematics, philosophy, and astronomy curriculum. It was here he became interested in astronomy . Through the influence of his uncle, who had become the bishop of Varmia, Copernicus was elected a canon of the Cathedral Chapter of Frombork. This membership entitled him to an income that he enjoyed throughout his life.
Copernicus enrolled in the University of Bologna in 1496 as a student of canon law, where he studied law. He pursued medicine at Padua, and law at the University of Ferrara, from which he received a doctorate degree in 1503.
As a student of canon law, Copernicus privately pursued his interest in astronomy. His earliest recorded observation was made on March 9, 1497. He observed a lunar eclipse in Rome on November 6, 1500. Much of his work, which made him famous, was accomplished in his spare time.
On March 13, 1513, he purchased building stones and a barrel of lime to construct a roofless tower to study the moon. He used a parallactic instrument to observe the moon, the quadrant for the sun, and the astrolobe, or armillary sphere for the stars.
Copernicus had become acquainted with the ideas of the Greek philosopher, Aristarchus of Samos (third century B.C.), that the earth and other planets revolved about the sun. By May 1514, he had circulated, to friends, handwritten manuscripts, Commentariolus. This manuscript contained his ideas on the subject. He deliberately withheld his name, for he did not want to antagonize the Christian leaders.
He spent many years researching and recording his observations that were necessary for his book, De Revolutionibus orbium coelestium (On the Revolution of the Celestial Spheres), in which he described his theory and his evidence for it. He proposed that a rotating Earth about a stationary central accounted for the daily rotation of the heavens, the annual movement of the Sun through the ecliptic, and the periodic retrograde of the planets.
By challenging the findings of Aristotle and Ptolemy, Copernicus laid no claim to priority, but recalled that the Pythagoreans had asserted the motion of the earth. He named Philolaus as having believed in the earth's revolution around an imaginary central fire, and Ecphantus as giving the earth an axial rotation. However, he refrained from linking Aristarchus with the earth's motion.
Though Copernicus made great gains, he badly underestimated the scale of the solar system and wrongly believed the orbits consisted of circles or of epicycles. Thus, his theory was inexact. His book motivated other astronomers, most notably, Tycho Brahe, to make accurate observations of planetary motions. It was Tycho's data that Johannes Kepler was able to deduce the laws of planetary motion correctly.
Copernicus' new theory had a particular mixture of both radical and conservative elements. He still adhered to Aristolelian doctrines of solid celestial spheres and the entire Aristotelian physics of motion. He also clung to the Ptolemaic representation of planetary motion.
Removal of the sun from the category of the planets was one of Copernicus' most influential contributions to the advancement of astronomy. His system also located Venus and Mercury correctly as the lower planets inside the earths' orbit at greater speeds. Furthermore, he located three outer planets on an epicycleit, whose center rode on a larger epicycle carried by a concentric deferent.
Though Aristarchus of Samos had propounded the heliocentric hypothesis more than seventeen centuries before Copernicus, it is appropriate that Copernicus received the bulk of the credit. Aristarchus never presented his theory in sufficient detail to make it useful. Copernicus transformed his hypothesis into a useful scientific theory that could be used for prediction, that could be checked against astronomical observations and that could be meaningfully compared with older theories of heliocentric ideas.
Copernicus' book was the prologue to the work of Galileo, Kepler, and Newton. Kepler determined the ellipticity if planetary orbits, Galileo formulated a new concept of motion, and Newton espoused his theory of universal gravitation.
Copernicus' views was a shift away from the anthropocentrism of the ancient and medieval world. This theory was not welcomed by the Church and it was only after the publication (1540) of Narratio prime (A First Account) by a supporter named Rheticus, that an aged Copernicus agreed to have his theory printed. One often repeated story holds that Copernicus received a printed copy on his deathbed. He died on May 24, 1543.