The Scientific Revolution

Lesson 2: Columbus and Copernicus

Copernicus

Copernicus is not as vivid a personality as some of his scientific contemporaries and rivals. Born into a Polish family that had produced many churchmen, Copernicus was educated in Italy and in 1512 settled as a canon of the cathedral at Frauensberg. He used one of the towers of the wall surrounding the Cathedral for astronomical observations, although he was not particularly good at observation.

Despite his lack of publications or university teaching, Copernicus acquired a reputation as an astronomer, and in 1514 was invited to Rome to help reform the calendar. (Calendar reform was one of the biggest problems for astronomers in the sixteenth century.) Although he refused, his name remained known in Rome, and Pope Clement VII (1478-1534) had heard of Copernicus’s astronomical theories by 1533.

Copernicus was a busy churchman and politician at a time when the area he lived in was disputed between the military order of the Teutonic Knights and the King of Poland, and then between the Catholic Church and the Protestant Reformation.

All the time Copernicus was working out his astronomical theory, various people in Rome were urging him to publish. However, it was a young German Lutheran astronomer and mathematics professor Georg Rheticus who made Copernicus’s work known. Visiting Copernicus in 1539, Rheticus urged him to publish his book.

Copernicus’s Latin treatise On the Revolutions of the Heavenly Spheres appeared in 1543, the same year Copernicus died, with a dedication to the Pope. Oster’s document 2.1 consists of excerpts from On the Revolutions.

The Copernican hypothesis was that the earth itself turned daily on its axis, accounting for the movements of the stars. The earth and the other planets also circled around the sun, which replaced the earth at the center of the universe. A sun-centered universe was not a completely new idea–it had ancient Greek precedents, and some medieval scientists had also broached the idea, if only to refute it. However, Copernicus was the first to work it out mathematically.

Copernicus’s system explained certain celestial phenomena better than did Ptolemaicism–for example, the fact that Mercury and Venus are never seen far from the sun is easy to explain on the principle that they orbit the sun more closely than does the earth. The retrograde motion of the planets was also easier to explain–it was simply caused by the earth’s passing them in orbit around the sun.

Despite this break with the past, Copernicus’s system was shaped in many ways by the Ptolemaic astronomy he was familiar with. As can be seen from the title of his book, Copernicus continued to think in terms of solid crystalline spheres in which the planets are embedded. Like the Ptolemaic system, the Copernican system required a complicated system of corrections to reconcile observations with a theory based on circular orbits.

Copernicus continued to view the principle of uniform circular motion as central to astronomy. By eliminating the equants he proclaimed that he had been more faithful to the principle of circular motion than was Ptolemy. The system was complicated more because Copernicus uncritically accepted previous observations, mostly Greek and Islamic, many of which were inaccurate or had been corrupted being copied from manuscript to manuscript.

Accounting for these observations required further adjustments. Copernicus’s theory was not really much less cumbersome than Ptolemy’s.

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