page_title: Ali Qushji
section_title: Concerning the Supposed Dependence of Astronomy upon Philosophy
hierarchical_section_title: Ali Qushji / Contributions to astronomy / Concerning the Supposed Dependence of Astronomy upon Philosophy
caption_attribution_description: English: Map showing the travels of Ali Qushji. Sources: [1]
context_page_description: Ala al-Dīn Ali ibn Muhammed, known as Ali Qushji was a Timurid theologian, jurist, astronomer, mathematician and physicist, who settled in the Ottoman Empire some time before 1472. As a disciple of Ulugh Beg, he is best known for the development of astronomical physics independent from natural philosophy, and for providing empirical evidence for the Earth's rotation in his treatise, Concerning the Supposed Dependence of Astronomy upon Philosophy. In addition to his contributions to Ulugh Beg's famous work Zij-i-Sultani and to the founding of Sahn-ı Seman Medrese, one of the first centers for the study of various traditional Islamic sciences in the Ottoman caliphate, Ali Kuşçu was also the author of several scientific works and textbooks on astronomy.
context_section_description: Qushji's most important astronomical work is Concerning the Supposed Dependence of Astronomy upon Philosophy. Under the influence of Islamic theologians who opposed the interference of Aristotelianism in astronomy, Qushji rejected Aristotelian physics and completely separated natural philosophy from Islamic astronomy, allowing astronomy to become a purely empirical and mathematical science. This allowed him to explore alternatives to the Aristotelian notion of a stationary Earth, as he explored the idea of a moving Earth instead (though Savage-Smith asserts that no Islamic astronomers proposed a heliocentric universe). He found empirical evidence for the Earth's rotation through his observation on comets and concluded, on the basis of empirical evidence rather than speculative philosophy, that the moving Earth theory is just as likely to be true as the stationary Earth theory.
  His predecessor al-Tusi had previously realized that "the monoformity of falling bodies, and the uniformity of celestial motions," both moved "in a single way", though he still relied on Aristotelian physics to provide "certain principles that only the natural philosophers could provide the astronomer." Qushji took this concept further and proposed that "the astronomer had no need for Aristotelian physics and in fact should establish his own physical principles independently of the natural philosophers." Alongside his rejection of Aristotle's concept of a stationary Earth, Qushji suggested that there was no need for astronomers to follow the Aristotelian notion of the heavenly bodies moving in uniform circular motion.
  Qushji's work was an important step away from Aristotelian physics and towards an independent astronomical physics. This is considered to be a "conceptual revolution" that had no precedent in European astronomy prior to the Copernican Revolution in the 16th century. Qushji's view on the Earth's motion was similar to the later views of Nicolaus Copernicus on this issue, though it is uncertain whether the former had any influence on the latter. However, it is likely that they both may have arrived at similar conclusions due to using the earlier work of Nasir al-Din al-Tusi as a basis. This is more of a possibility considering "the remarkable coincidence between a passage in De revolutionibus (I.8) and one in Ṭūsī’s Tadhkira (II.1[6]) in which Copernicus follows Ṭūsī’s objection to Ptolemy’s "proofs" of the Earth's immobility."
caption: His travel to the Ottoman Empire.
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