THE COPERNICAN THEORY
Copernicus was born at Thorn in Poland (1473) of a German mother. Educated first in medicine, he studied astronomy in Vienna, and he was later in Italy (1495-1505) at the height of the Renaissance. When he returned home, his uncle, the bishop of Ermeland, presented him with a clerical position at Frauenburg. Here for forty years he labored to bring astronomical calculations and observations into harmony, and finally, long after he had become convinced of the soundness of the heliocentric view, published the work〖See his Dedication of his “Revolutions of Heavenly Bodies,” Harvard Classics, xxxix, 52-57.〗 which marks the first great step in modern science, a work which he saw for the first time on his deathbed in 1543.
Copernicus showed that all the difficulties which the movements of the planets present would become very much less if the moon were left the only satellite of the earth, and the earth itself and all the planets were assumed to move around the sun. He did not prove—in truth being wise and realizing his own limitations, he did not seek to prove—this hypothesis, but only to present the reasons why it must appear the most probable explanation of the principal astronomical phenomena.
The new doctrine made converts slowly. At first it was opposed by the professional astronomers, with whose time-honored habits it interfered, and who were, for the most part, not competent to understand it. Later the opposition of the great Tycho Brahe worked against it for many years. Still later the opposition of theologians effectually cut off many converts, most notably Descartes. But the discovery of Kepler’s laws completely destroyed the Ptolemaic system, and must have convinced nearly all reasonable men of the correctness of that of Copernicus. These famous laws are as follows: The line joining the sun with a planet sweeps over equal areas in equal periods of time. Every planet moves in an ellipse with the sun at one focus. The squares of the times of the revolution of any two planets are in the same ratio as the cubes of their mean distances from the sun.