QUṬB AL-DĪN AL-SHĪRĀZĪ AND THE DEVELOPMENT OF NON-PTOLEMAIC PLANETARY MODELING IN THE 13th CENTURY

Coming after Muʾayyad al-Dīn al-ʿUrḍī (1200–1266) and Naṣīr al-Dīn al-Ṭūsī (1201–1274), Quṭb al-Dīn al-Shīrāzī (1236–1311), a leading figure of the so-called Marāgha school in astronomy, presents his predecessors’ non-Ptolemaic models and criticizes them in his three hayʾa books. Since his own new models in Nihāyat al-idrāk (written in Arabic in 1281) and Ikhtiyārāt muẓaffarī (written in Persian in 1282) are not without difficulties, in his latest book on hayʾa , al-Tuḥfa al-shāhiyya (written in Arabic in 1285) 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.