The Fatal Consequences of a Priori in the Natural Sciences, to be Replaced by Facts

Abstract

Let us first speak, in Astronomy, of the original conception of the Universe, based on appearances. Every man, sailing on the sea, far from the coast, in good weather, sees the sky horizontally, in all directions, and vertically. He speaks of “celestial vault,’’ an apparent sphere on which, by clear night, moves, together with the stars “carried” by it. That was what was described by Aristotle in his “De Coelo”. Four centuries later, the astronomer Claude Ptolémée, in his work “L’Almageste”, reporting on measurements of the positions of known planets he had compiled, consecrated the philosophical theory of Aristotle as a scientific theory, which were taught in Christian universities in the Middle Ages. However, in the 3rd century BC, Aristarchus of Samos, adopting also the existence of the sphere of the fixed stars, postulated that the sun was the center. There were then, in the time of Ancient Greece and Rome, two philosophical schools, which agreed on the existence of this sphere carrying the fixed stars, but opposed on which star was at the center, either the Earth or the sun. This quarrel would re-emerge in the midst of Christianity in the Middle Ages. Copernicus, canon and astronomer, wondering about the irregular orbits described by the planets around the Earth, completed the calculations of the positions of the planets of Ptolemy and “demonstrated” that they revolved around the sun; he, however, attributed to them, by his approximate calculations of their distance from the sun, circular orbits which Kepler soon showed to be ellipses whose sun was a focus. Copernicus reported his theory in the work “De Revolutionibus Orbium Caelestium”, published in 1543, which was sent after his death, by his friend Osiander, to Pope Paul III.