In the late fifteenth century, humanist scholars in the West rediscovered the works of Plato. To many scholars, Plato’s description of a cosmos characterized by harmony, symmetry, and mathematical proportion deeply conflicted with the complex geometrical model of the universe elaborated in Ptolemy’s Almagest. Although Ptolemy’s models and the planetary tables from which they were calculated were still acceptable from a mathematical point of view, humanists found those models aesthetically unsatisfactory.
Polish astronomer Nicolaus Copernicus circulated his criticisms of Ptolemaic astronomy around 1514 in a manuscript he called Commentariolus (A Little Commentary). In it, he offered an alternative planetary model, in which the Sun was the center of the universe. The Earth joined the rest of the planets in moving in a circular motion around the Sun, and the moon in turn revolved around the Earth. After decades of refining his theory, Copernicus was persuaded to publish his work. De revolutionibus orbium coelestium (On the revolutions of the celestial spheres) appeared in 1543, only two months before Copernicus’ death.
De revolutionibus outlines Copernicus’ theory about the universe and provides complex mathematical computations explaining the movement of the planets based on the Sun-centered model. However, Copernicus’ theory was obscured by additions to the book. At the final stage of printing, an unsigned preface by a Lutheran pastor named Andreas Osiander was inserted without Copernicus’ permission. The preface declared that the author was only presenting a hypothesis which could improve astronomical computations, rather than asserting that the Earth truly revolved around the Sun. For the first fifty years after its publication, most astronomers focused on using these geometrical models to better predict planetary positions rather than on spreading Copernicus’ heliocentric theory.
Nicolaus Copernicus. De revolutionibus orbium celestium. Amsterdam: Wilhelm Janson, 1617.
The third edition, published in Protestant Amsterdam after the work was placed on the Catholic Church’s index of prohibited books in 1616.
Erasmus Reinhold. Prvdenticae tabvlae coelestivm motvvm (Prutenic tables). Tübingen: Ulrich Morhart, 1551.
Reinhold calculated these planetary tables using Copernican models. Astronomers found the Prutenic tables to be more accurate than the old Alfonsine tables, but they would be superseded by the work of Tycho Brahe and Johannes Kepler within a century of publication.