The Polish astronomer Nicholas Copernicus (1473–1543) provided the first modern theory of planetary motion that was heliocentric — that placed the sun motionless at the center of the solar system with all the planets, including the earth, revolving around it.

His theory ran counter to the Ptolemaic system advanced nearly 1,500 years before. The church embraced the Ptolemaic system, which held that the sun revolved around the earth. As it turned out, Copernicus's system was not published until 1543, the year he died.

After studying astronomy at the University of Krakow, Copernicus spent several years in Italy studying various subjects, including medicine and canon law. Around 1500 he lectured in Rome on mathematics and astronomy. By 1512 he had settled in Frauenburg, East Prussia, where he had been nominated canon of the cathedral. There he performed his canonical duties and also practiced medicine.

The Copernican System

The work that immortalized Copernicus was his De revolutionibus orbium coelestium (The Revolution of the Heavenly Bodies), in which he sets forth his beliefs concerning the universe, known as “the Copernican system.” The treatise, which was dedicated to Pope Paul III, was probably completed by 1530, but it was not published until Copernicus was on his deathbed. Modern astronomy was built upon the foundation of the Copernican system.

The new astronomy opposed the theological orthodoxy of the day. The church could not relinquish its belief that the earth was at the center of the solar system. If the earth was not at the center, then humankind's importance was symbolically reduced. Fearing controversy and even condemnation by the church, Copernicus held off publishing his book.

It was published a few days before his death. At first it did not engender controversy. In fact, it escaped Catholic condemnation until the time of Galileo. This was due in part to the book being dedicated to the pope. Furthermore, a friend, who was a Lutheran clergyman, had prudently added a preface saying that the Copernican theory was only a hypothesis.