Coming after Muʾayyad al-Dīn al-ʿUrḍī and Naṣīr al-Dīn al-Ṭūsī, Quṭb al-Dīn al-Shīrāzī, a leading figure of the so-called Marāgha school in astronomy, presents his predecessors’ non-Ptolemaic models and criticizes them in his threehayʾabooks. Since his own new models inNihāyat al-idrāk andIkhtiyārāt muẓaffarī are not without difficulties, in his latest book onhayʾa,al-Tuḥfa al-shāhiyya he puts forward his modified models inspired from Ṭūsī’s and ʿUrḍī’s models and produces a series of new models for Mercury and the oscillation of the spheres. Nevertheless, in (...) spite of all his attempts, the tradition of non-Ptolemaic modeling after him never converged to a series of standard models.RésuméVenu après Muʾayyad al-Dīn al-ʿUrḍī et Naṣīr al-Dīn al-Ṭūsī, Quṭb al-Dīn al-Shīrāzī, éminente figure de l’école dite de Marāgha en astronomie, présente, dans ses trois ouvrages dehayʾa, les modèles de ses prédécesseurs tout en les critiquant. Puisque ses propres nouveaux modèles, présentés dansNihāyat al-idrāk etIkhtiyārāt muẓaffarī, ne sont pas sans difficulté, il présente, dans son dernier ouvrage dehayʾa,al-Tuḥfa al-shāhiyya, d'autres modèles inspirés de ceux d'al-Tūsī et d'al-ʿUrḍī, et produit un ensemble de nouveaux modèles pour Mercure et l'oscillation des sphères. Or, en dépit de tous ces efforts, la tradition des modèles non ptolémaïques, telle qu'elle se développa après lui, ne convergea pas vers un ensemble standard de modèles. (shrink)

It is well known that heliocentrism was proposed in ancient times, at least by Aristarchus of Samos. Given that ancient astronomers were perfectly capable of understanding the great advantages of heliocentrism over geocentrism—i.e., to offer a non-ad hoc explanation of the retrograde motion of the planets and to order unequivocally all the planets while even allowing one to know their relative distances—it seems difficult to explain why heliocentrism did not triumph over geocentrism or even compete significantly with it before Copernicus. (...) Usually, scholars refer to explanations of sociological character. In this paper, I offer a different explanation: that the pre-Copernican heliocentrism was essentially different from the Copernican heliocentrism, in such a way that the adduced advantages of heliocentrism can only be attributed to Copernican heliocentrism, but not to pre-Copernican heliocentrism proposals. (shrink)