Middle Ages Geocentrism

During the Middle Ages geocentrism was never cast into doubt. It was linked to theological conceptions of divine Providence and Creation, as witnessed in Dante Alighieri’s synthesis of late medieval thought in the Divina Commedia. The Earth rested at the center as the place of change and corruption, encircled by the ethereal perfec- tion of the heavenly spheres surrounded by the empyrean heaven, which was the abode of the blessed souls and the contemplating God. Planetary order was less standardized. In the twelfth century Andalusia al-Bitruji argued for the sublunary location of Mercury and the superlunary of Venus in his work of homocentric astronomy, Book on Astronomy, which had large dissemina- tion among Jewish and Latin philosophers. Medi- eval commentaries on Macrobius, Pliny the Elder, Martianus Capella, and Calcidus also displayed qualitative heavenly diagrams in which planetary motions are not perfectly circular or the two infe- rior planets encircle the Sun instead of the Earth. The latter model (geocentrism with heliocentric paths for Mercury and Venus), ascribed in antiq- uity to Herakleides of Pontus, became known as the Capellan system. Copernicus would refer to the diverging opinions of his ancient andmedieval forerunners in the beginning of De revolutionibus to claim his right to an independent and innova- tive inquiry into this matter:

Therefore, having obtained the opportunity from these sources, I too began to consider the mobility of the Earth. And even though the idea seemed absurd, nevertheless I knew that others before me had been granted the freedom to imagine any circles whatever for the purpose of explaining the heavenly phenomena. Hence I thought that I too would be readily permitted to ascertain whether explanations sounder than those of my predecessors could be found for the revolution of the celestial spheres on the assumption of some motion of the Earth.