Copernicus was the First Person to Give Us the Concept of a Sun-Centered Universe

Actually, it was the Greek, Heracleides (388 BC-315 BC) and later, Aristarchus of Samos (310 BC-230 BC) who first entertained the heliocentric notion that a rotating Earth could be in revolution around the sun. The concept lost favor to the geocentric model of the universe which was the synthesis of hundreds of years of inductive reasoning practiced by Plato, Eudoxus, Aristotle, Hipparchus, Ptolemy and others. The Greeks never intended their ideas to represent reality, but by the time of the Renaissance, Ptolemy's geocentric model was thought to portray accurately the true order of the cosmos. Copernicus realized the inexactness of the cumbersome geocentric models to predict accurately planetary positions and borrowed ideas from earlier Greeks to simplify the system into a heliocentric version. However, Copernicus did not merely suggest this change, he worked out the mathematical details of this system to show how the revolutions of the planets around the sun could account for the observations of planetary motion. Ironically, after Copernicus completed publication of his theory in 1543, under the title of De Revolutionibus Orbium Coelestium, astronomers could not decide by observations which theory produced the better fit. It appeared that the simplicity of the Copernicus's theory easily began to win converts, particularly in the Protestant territories of Europe. The dilemma of which theory was superior was finally solved by Johannes Kepler in 1609 when he used the Copernican model to solve correctly for the changes which Tycho Brahe had observed in the positional shifts of the planet Mars. When Kepler used ellipses to explain planetary motions, rather than the circular motions which Copernicus had retained in his theory, Tycho's data fit precisely with the orbital parameters of Mars. In short order, the reinvented heliocentric theory as proposed by Copernicus became one of the cornerstones of Renaissance thought.