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Glen Van Brummelen

« Taking latitude with Ptolemy: Jamshīd al-Kāshī's novel geometric model of the motions of the inferior planets ». Archive for History of Exact Sciences, 60, 2006, pp. 353-377.

Compte-rendu réalisé par Benno Van Dalen

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1This article describes the remarkable model for planetary latitude presented in the Ḫāqānī Zīj by Ġiyāṯ al-Dīn Jamšīd al-Kāšī (d. AD 1429), who is particularly well-known for his leading role in Ulugh Beg’s observatory at Samarkand and his exceptional computational skills. al-Kāšī designed a three-dimensional model for the planetary latitudes that allowed their calculation with much more precision than Ptolemy’s two-dimensional model with separate treatment of the three latitude components for Venus and Mercury. In al-Kāšī’s model the epicycle is embedded in a sphere (in the same way in which the ecliptic, equator and inclined orbits of the planets are embedded in the heavenly sphere), and the latitude components correspond to certain movements of that sphere. The author reproduces al-Kāšī’s method of calculating the latitudes on the basis of his new model and his highly elaborate example for Venus. An Appendix includes an English translation by Sergei Tourkin of al-Kāšī’s Persian description of the model.

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Benno Van Dalen. Glen Van Brummelen, « « Taking latitude with Ptolemy: Jamshīd al-Kāshī's novel geometric model of the motions of the inferior planets ». Archive for History of Exact Sciences, 60, 2006, pp. 353-377. », Abstracta Iranica [En ligne], Volume 29 | 2008, document 312, mis en ligne le 15 septembre 2008, consulté le 23 octobre 2019. URL : http://journals.openedition.org/abstractairanica/30922

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