Ali Qushji and Regiomontanus:
Eccentric transformations and Copernican revolutions

F. Jamil Ragep
Çeviren: Yavuz Unat

In 1973, Noel Swerdlow presented a new and significant reconstruction of how Copernicus arrived at the heliocentric theory. This reconstruction was based upon a set of notes in Copernicus's hand. These notes provided compelling evidence that Copernicus had transformed Ptolemy's epicyclic models of the planets into eccentric models as a first step in developing a Sun-centred astronomy. Curiously Ptolemy denied this, claiming that this was possible only for the outer planets. Regiomontanus gives a brief sketch and prof of the crucial theory for the inner planets, which would allow Copernicus to convert all the planets from epicyclic to eccentric models. Whatever subsequent use was made of them, Regiomontanus's own motivation for including these propositions at the beginning of book XII remain unclear. One possibility is that Regiomontanus does not claim credit because he was not in fact the originator of the proposition. Indeed it would seem, based on evidence presented in the sequel, that an older contemporary of Regiomontanus named Ali Qushji may well have been the discoverer of the crucial proposition and that Regiomontanus learned of it either while in Italy or through the intermediation of Cardinal Bessarion, who had originally suggested to Regiomontanus and his collaborator Georg Peurbach that they write the Epitome.

Key words: Ali Qushji, Regiomontanus, Copernicus, heliocentric theory, eccentric transformations, history of astronomy; Anahtar kelimeler: Ali Kuşçu, Regiomontanus, Kopernik, güneşmerkezli kuram, dışmerkezli dönüşümler, astronomi tarihi.