The theologian ‘Abdul Deen Al ‘Iji (1281–1355), a leading cleric who maintained that all physical effects were directly caused by God rather than by any natural triggers, was one of the first Muslims who rejected the Aristotelian principle that celestial bodies operated in circular motions. Instead, Al ‘Iji believed in and promoted the view that celestial spheres were “imaginary things” and “more tenuous than a spider’s web”. Though such esoteric fare amused contemporary scientists, Muslim astronomers considered the possibility that circular motion was widespread, theorising that even the Earth rotated on its own axis or, perhaps, moved in a heliocentric solar system in a circular orbit even if the latter notion was never explicitly cited. In time, the heliocentric model was perfected by one of the greatest scientists of all time, the Prussian-born Nicolaus Copernicus (1473-1543), who, most likely, borrowed the concept from Ibn Al Shatir as well as scientists who formed the Maraghah school, led by the great Nasri Al Deen Al Tusi and ‘Ali Al Qushji. The latter was not as well known but deserved to be.
‘Ali Al Qushji (1403—1474) rejected Aristotelian physics — which advanced the notion of a stationary Earth — and completely separated it from astronomy, which allowed the study of celestial bodies to become a purely empirical and mathematical science. He concluded that while philosophy was a necessary subject to study in depth, it ought to be separated from pure sciences, which required empirical evidence. Qushji was the first to posit that the theory of Earth rotating on its own axis was just as likely to be true as the Aristotelian hypothesis of a stationary Earth, and that it was not possible to empirically deduce which one was the truth. Such a bold vision helped usher in the Copernican revolution that, without exaggeration, introduced fresh concepts of astronomy. This, in turn, paved the way for the physical study of celestial bodies. What was noteworthy was this: there were few if any precedents for such vision in European traditions before Copernicus, though incredibly sophisticated discussions occurred in the Muslim world, where scientists raised questions about the rotation of our planet as well as most celestial movements. Though seldom read outside of expert circles, Qushji’s treatise, “Concerning the Supposed Dependence of Astronomy upon Philosophy”, stood apart as a work of science and that ensured his place in several disciplines.
Life and times
‘Ala’ Al Deen ‘Ali Al Qushji was born in 1403 in Samarkand, in present-day Uzbekistan. His father, Mohammad Al Qushji (the falconer), who was attached to the royal court of Mirza Mohammad Taraghay Bin Shahrukh, better known as Ulugh Beg (ruled 1394-1449). The Timurid sultan was also an astronomer/mathematician and established the renowned Samarkand observatory. After Ulugh Beg’s assassination in 1449, Al Qushji left Samarkand for Herat, but quickly moved to Tabriz and finally Constantinople (today’s Istanbul). It was in Tabriz that he made his first contacts among the rulers. In 1470, the ruler Uzun Hassan sent Al Qushji as an emissary to the Ottoman Sultan Mehmet (Mohammad) II who, in turn, was impressed by the astronomer. Through various discussions, the two men bonded, which led the pro-intellectual Sultan Mehmet to offer Qushji a permanent post. As a gesture of appreciation, Qushji presented the sultan with the mathematical treatise, “Al-Risalah al-Muhammadiyyah fil-Hisab” (Treatise on Arithmetic), a significant contribution that used the terms “muthbat” and “manfi” for added and subtracted quantities instead of the standard terms “za’id” and “naqis”. The new terms were translations from Chinese, and were widely used for positive and negative quantities in Iran, Turkey, central Asia, and Azerbaijan, though they were unknown among Arabs; in time, Europeans borrowed these terms too, which most probably reached the Old Continent through Al Qushji’s writings that were translated into Latin.
In Constantinople, ‘Ali Al Qushji was appointed a mudarris (teacher) at the Hagia Sophia School of Sultan Mehmet II, where the scientist composed his “Risalah dar Hayat” (1470) in Persian. He completed various other books during his sojourn in the Ottoman Empire’s capital, including the “Sharh-e Tejrid” (“Sharh al-Tajrid” or Abstract of Isolation) that expanded on Al Tusi’s “Tajrid al-Kalam” (Abstract of Theology). He died in the capital in 1474.
Contributions to astronomy
Like other polymaths, Al Qushji delved into several disciplines, including language, religion, philosophy and the mathematical sciences, and while he certainly introduced new ways of understanding and exploring these disciplines, his most significant area of expertise was astronomy. Al Qushji must be given credit for improving Al Tusi’s planetary model and contributing towards the “Zij-i Sultani”, the astronomical tables and star catalogues that were published by Ulugh Beg in 1437 at the Samarkand Observatory — epochal developments for the times. In addition to his contributions to the “Zij”, Qushji wrote nine major books in astronomy, two in Persian and seven in Arabic. John Greaves translated two, the “Tract on Arithmetic” and the “Tract on Astronomy”, both into Latin in 1650.
As stated above, Al Qushji’s most important book was “Concerning the Supposed Dependence of Astronomy upon Philosophy”, which offered a refutation of Aristotelian theories and which was partially translated by F. Jamil Ragep in his impressive analytical works on the medieval scientist. Although Qushji explored alternatives to the Aristotelian notion of a stationary Earth, and developed the idea of a moving Earth instead, few recognised his role. Even worse, while at least one Western historian (Emilie Savage-Smith) of the medieval Islamic era asserted that no Islamic astronomer proposed a heliocentric Universe, where the Sun is at the centre rather than Earth, Al Qushji may well have advanced the empirical evidence for the Earth’s rotation through numerous observations of comets and other celestial bodies. Professor Ragep, an authority with numerous publications on leading Muslim astronomers, argued that Al Qushji certainly entertained the theory on the basis of empirical evidence rather than speculative philosophy (something which Savage-Smith acknowledges), though his investigations in various documents were still not completed. In his words, Ragep affirmed that whereas Al Qushji’s predecessor, the great Al Tusi, realised that “the monoformity of falling bodies, and the uniformity of celestial motions”, both moved “in a single way” — Qushji proposed that “the astronomer had no need for Aristotelian physics and in fact should establish his own physical principles independently of the natural philosophers”. This was a novel assessment, and while the need for irrefutable evidence remained, the conversation entered a fresh arena where alternatives could be considered.
Still, while Qushji’s “conceptual revolution” must be taken into account when the Copernican Revolution is discussed, there is no direct evidence so far that European astronomy benefited from such views. Professor Ragep is hard at work to identify period manuscripts that could enlighten us as to whether Al Qushji’s vision of Earthly motions was similar to the later views of Copernicus.
Naturally, one could not eliminate the possibility that the two men, Al Qushji and Copernicus, could well have arrived at similar conclusions because both relied on Al Tusi’s earlier work. This is more of a possibility considering “the remarkable coincidence” between a passage in Copernicus’s “De Revolutionibus” (I.8) and one in Al Tusi’s “Tadhkirah” (II.1[6]), in which Copernicus follows Al Tusi in objecting to Ptolemy’s “proofs” of the Earth’s immobility.
The Maraghah School
It may be useful in this context to clarify the notion that Copernicus or other European scholars operated independently, because there is near unanimity that the Islamic world was the centre of astronomical thought and activity throughout the Middle Ages. In fact, Ptolemy’s solar theory were recalculated by Muslim scientists starting in the tenth century, led by Ibn Al Haytham, who wrote a scathing critique of the Greek. “Ptolemy assumed an arrangement that cannot exist,” Ibn Al Haytham concluded, “and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist.”
By the 13th century, the Maraghah School — an observatory in Maraghah (today in Iran), which, under the leadership of Al Tusi, was then the largest such facility in the world, consisting of a series of buildings occupying an area of 150 metres in width and 350 metres in length — was fully engaged in correcting Ptolemy. Indeed, various planetary models developed by Al Tusi and Al Qushji broke the equant motion — where all axes of an object have the same length — into two or more components of uniform circular motion at different lengths. In turn, the Maraghah models advanced the notion that the uniform rotation of spheres controlled the direction and distance of the centre of the epicycle, together. Even if the centre of the epicycle lay in nearly the same position as it would have in Ptolemy’s model, and always moved uniformly with respect to the equant, the circular motion allowed for independent movements too.
Copernicus used several of the devices developed by the Maraghah astronomers, including Al Tusi (1201-1274), Mu’ayyad Al Deen Al ‘Urdi (died 1266), Qutb Al Deen Al Shirazi (1236-1311), Ibn Al Shatir (1304–1375) and, of course, Al Qushji. Professor Ragep has added significant knowledge on the period, arguing that the theory for the inner planets presented by the German mathematician/astronomer and Catholic bishop Johannes Müller von Königsberg, today best known by the Latin epithet Regiomontanus, which allowed Copernicus to convert the planets to eccentric models, was first developed in the 15th century by Al Qushji. Even if no proof exists of their transmission from East to West, Ragep raises the most critical question: How likely is it that so many similar techniques were invented independently in Western societies?
Whether the achievements of the Maraghah School and their predecessors and successors qualified as a “Maraghah Revolution” was impossible to know although few could deny the many advances in astronomy made by its scientists. Were it not for their contributions, the work at the Baghdad observatory during the reign of the Caliph Al Ma’mum, which corrected previous astronomical data and resolved significant problems that led to the development of universal astrolabes, could not have been accomplished.
Legacy to Arabs and Muslims
Al Qushji’s studies on astronomy and arithmetic were used as course books in Ottoman, Persian and Arab schools during the scientist’s lifetime and were, naturally, relied upon for several decades after his death before successors fine-tuned his evidence. While few Arabs and Muslims recalled the astronomer’s numerous contributions, what stood out was his reliance on empirical evidence instead of speculative notions, which he believed originated in faith. A devout believer, Al Qushji was serene in his outlook, concluding that God created celestial bodies and empowered man to discover its “mechanisms” precisely to strengthen his convictions in the creator. He saw no contradictions between faith and science as the latter represented mere evidence to buttress divine power.
Dr Joseph A. Kéchichian is an author, most recently of, “Legal and Political Reforms in Sa‘udi Arabia”, London: Routledge, 2013.
This article is the 25th of a series on Muslim thinkers who greatly influenced Arab societies across the centuries.
