The Confluence of Some Ideas Used by Copernicus in De Revolutionibus

Copernicus (1473-1543) first became familiar with ancient Greek astronomy via the Epitome of Ptolemy's Almagest by Georg Peurbach and Regiomontanus (ca. 1463); the full translation of the Almagest was published in Venice in 1515. The Almagest had been translated into Latin by Gerard of Cremona and Galib the Mozarab. This was completed in Toledo about 1175. How do we know this? From an eyewitness account by the Englishman Daniel of Morley. Copernicus's great book contains a diagram almost identical to one in a work of Nasir al-Din al-Tusi (1201-1274), the founder of the Maragha Observatory. Copernicus also uses a lemma attributed to a second astronomer who worked in Maragha, Mu'ayyad al-Din al-Urdi (d. 1266). There is evidence that the insights of the Maragha school became known in Byzantium thanks in part to the efforts of Gregory Chioniades (ca. 1240-1320). Copernicus's model of the motion of the Moon is identical to that of Ibn al-Shatir (1304-1375). How much Copernicus's model of the motion of Mercury is similar to that of Ibn al-Shatir is controversial. Recent investigations concerning the Jewish scholar Moses Galeano, who lived in Constantinople, Crete, and the Veneto, lend credence to the notion that the insights of the Maragha school reached Padua in the years 1497 to 1502 thanks to Galeano. This overlaps the very years that Copernicus studied astronomy in Padua. Thus, we now understand how some of the building blocks used by Copernicus were obtained by his teachers or directly by him.