Ala al-Din Ali ibn Muhammed Ali Qushji

Quick Info

Samarkand, Timurid Empire, now Uzbekistan
16 December 1474
Constantinople, now Istanbul, Turkey

Ali Qushji was an Islamic astronomer and mathematician, born in what is now Uzbekistan, who worked at observatories in Samarkand and Constantinople and whose results influenced Copernicus to produce his heliocentric system.


Ali Qushji was the son of the royal falconer who trained birds such as falcons to catch pray. Let us begin by explaining that 'Ali Qushji' is basically a nickname meaning 'Ali the Falconer', the name Qushji having been given to the father of the subject of this biography. Although his name was Ala al-Din Ali ibn Muhammed, he is always known as Ali Qushji.

Samarkand, the city where Ali Qushji was born, had been conquered by Tamerlane in 1370 and it became the capital of the Timurid Empire. Tamerlane was a patron of the arts and under his rule Samarkand became a centre for culture. Tamerlane died in 1405 and his son Shah Rukh, like his father a great patron of the arts and sciences, moved the capital of the Timurid Empire to Herat. Shah Rukh's son Ulugh Beg, a grandson of Tamerlane, became the ruler of Samarkand in 1409. Ali Qushji's father became Ulugh Beg's falconer and Ali Qushji grew up in the atmosphere of culture, particularly mathematics and astronomy, around Ulugh Beg who was himself an outstanding mathematician and astronomer. Ulugh Beg built a Madrasa, a research and teaching institute, on Registan Square in Samarkand between 1417 and 1420. Around sixty leading scholars were invited to the Madrasa by Ulugh Beg where the leading teacher was Qadi Zada al-Rumi and leading researcher was Jamshid al-Kashi.

Ulugh Beg was only 17 years old when Qadi Zada, who was 46 years old, met him at Samarkand in 1410. Ulugh Beg was far more interested in science and culture than in politics or military conquest but he was, nevertheless, deputy ruler of the whole empire and, in particular, sole ruler of the Mawaraunnahr region. Qadi Zada became the leading teacher at Ulugh Beg's Madrasa and he spend the rest of his life working there. He became one of Ali Qushji's teachers and Ulugh Beg, who also taught at the Madrasa, became another. Ali Qushji was also taught by Jamshid al-Kashi who had been invited to the Madrasa by Ulugh Beg. There is little doubt that al-Kashi was the leading astronomer and mathematician at Samarkand and he was called the second Ptolemy by an historian writing later in the same century. F Jamil Ragep writes [11]:-
One thing that seems to have been emphasised in the Samarqand School was the importance of the mathematical sciences. Biographical accounts of Qadi Zada al-Rumi, for example, highlight his difficulties with his teacher al-Sayyid al-Sharlf al-Jurjani, who thought his student overly interested in mathematics at the expense of philosophy. Jamshid al-Kashi is also noted for his embrace of the mathematical sciences, as we can see from his letters to his father, and Ulugh Beg, like a number of Mongol/Turkic rulers, was predisposed to support the mathematical sciences; in addition, he himself became proficient in them. It was in this atmosphere that the young Ali Qushji was raised, and this seems to have had a profound effect upon his intellectual outlook.
After his studies in Samarkand, Ali Qushji went to Kerman in Persia (now in Iran), where he conducted some research on storms in the Oman sea and wrote a work on this topic. Moving on, he reached Herat (now in Afghanistan) around 1423. Herat, under the rule of Ulugh Beg's father, was, like Samarkand, a centre for scholarship with many leading artists, mathematicians and astronomers. There Ali Qushji taught astronomy, wrote a work about the Moon (Explanations on the Periods of the Moon) and another on mathematics. He then returned to Samarkand and presented Explanations on the Periods of the Moon to Ulugh Beg. It is claimed that Ulugh Beg found the work so fascinating that he read the whole manuscript while standing up. He was certainly impressed with Ali Qushji's work and appointed him as an astronomer at the Samarkand Observatory, a vast observatory which was nearing completion at this time.

The Samarkand Observatory became the world-leading observatory of its day. Ulugh Beg appointed around sixty astronomers to the observatory including Ali Qushji, Qadi Zada al-Rumi and Jamshid al-Kashi. It was not until Tycho Brahe set up his observatory at Uraniborg about 150 years later, that the world had a more impressive observatory than that at Samarkand. The Observatory was a three-storey cylindrical building covered with glazed tiles which had been designed to house three enormous astronomical instruments. The main instrument, a large part of which has survived, in now called the Fakhri sextant [15]:-
The so-called "sextant" obviously would have extended well above the ground ... and likely was closer to being a quadrant. ... the instrument "was by far the largest meridian instrument ever built." Fragments of the curved measuring track have survived with markings for around 20 degrees; this is about the highest point that observations likely would have been made. The "sextant" would have been used to measure the angle of elevation of major heavenly bodies, especially at the time of the winter and summer solstices. Light from the given body, passing through a controlled opening, would have shone on the curved track, which is marked very precisely with degrees and minutes. "It could achieve a resolution of several seconds of arc - on the order of a six-hundredth of a degree ... . It is not clear whether more than the sun and moon could have been measured in this fashion, since planets, for example, would not have cast sufficient light. The observatory was equipped with a variety of other instruments, which probably accounted for the largest part of its scientific measurement.
Ali Qushji worked at the Samarkand Observatory until 1449 when, following a civil war, Ulugh Beg was assassinated. Beg's political skills were not up to his mathematical skills and, after his father's death in 1447, he was unable to retain power despite being an only son. He was eventually put to death at Samarkand at the instigation of his own son Abd al-Latif. The Samarkand Observatory did not survive long after Ulugh Beg was assassinated as the building was destroyed, its contents were stolen and the astronomers were driven away. Ali Qushji left Samarkand and went to Herat where he had been working before he was employed at the Samarkand Observatory. He wrote works which he presented to the Timurid Sultan Abu Said. In 1469, however, Abu Said was defeated by Uzun Hasan and Ali Qushji moved to Tabriz, the capital of the Qara Qoyunlu state in Azerbaijan. There he met the ruler of the Qara Qoyunlu state, Uzun Hasan, who asked Ali Qushji to go to Constantinople to act as a good will ambassador between himself and Mehmed II, who had captured Constantinople in 1451. Mehmed II welcomed Ali Qushji, who arrived in Constantinople in 1470, and offered him a position in Constantinople as a teacher at the Madrasa.

The position in Constantinople looked very attractive to Ali Qushji but he had promised Uzun Hasan that he would carry out his duty as a good will ambassador and return to Tabriz to report on his mission. He explained to Mehmed II [7]:-
I would like to go back to Tabriz if you let me. The true reason of my existence here is to be the good-will Messenger of Akkoyunlu Ruler, Sultan Hasan. It is necessary for me before I accept the gracious invitation of my Sultan to turn back and inform the person who sent me here and who trusted me that I carried my duty with a good result ...
This was agreed and Ali Qushji returned to Tabriz and reported the success of his mission to Uzun Hasan. He then made preparations to move to Constantinople [5]:-
... around 1472 Ali Qushi, together with his family and students, left permanently for Constantinople ... When Ali Qushji and his entourage approached Constantinople, Sultan Mehmed sent a group of scholars to welcome them. Sources say that in crossing the Bosporus to Constantinople, a discussion ensued about the causes of its ebb and flow. Upon arrival in Constantinople, Ali Qushji presented his mathematical work 'al-Muhammadiyya fi al-hisab' to the sultan, which was named in his honour.
Once in Constantinople, Ali Qushji taught at the Sahn-i Thaman Madrasa. He was then made head of the Ayasofya Madrasa but his time in that role was short lived since he died suddenly two years after settling in Constantinople. He was buried in the cemetery of the Eyyub mosque. Despite his short time in Constantinople, he was highly successful there [5]:-
In this brief period Ali Qushji educated and influenced a large number of students, who, along with his writings, were to have an enormous impact on future generations.
Let us now mention some of the many contributions to mathematics and astronomy that Ali Qushji made while working at the Samarkand Observatory and at the Constantinople Madrasas. We give information first about what must be considered his most important contribution, namely the belief that it was Ali Qushji's results that, indirectly, influenced Copernicus allowing him to put forward his heliocentric theory. This is argued convincingly in [11] and is now widely accepted. We give a few extracts from the introduction of [11] to explain how Ali Qushji may have had a vital role in the heliocentric revolution:-
In 1973, Noel Swerdlow presented a new and significant reconstruction of how Copernicus arrived at the heliocentric theory. This reconstruction was based upon several bits of newly-interpreted information, most importantly a set of notes in Copernicus's hand contained in an Uppsala University manuscript. These notes provided compelling evidence that Copernicus had transformed Ptolemy's epicyclic models of the planets into eccentric models as a first step in developing a Sun-centred astronomy. But this transformation depended upon a general proposition that one could indeed convert all the epicycle models into eccentric ones. Curiously, Ptolemy denied this, claiming in Book XII of the Almagest that this was possible only for the outer planets (Mars, Jupiter, and Saturn) but not the inner ones (Mercury and Venus). ...

... it would seem that no one else recognised this until the fifteenth century. Swerdlow found what he believed to be the source for the propositions Copernicus needed to begin his conversions, namely Book XII, Chapters I and 2 of Regiomontanus's 'Epitome of the Almagest'. In Chapter 2, Regiomontanus gives a brief sketch and proof of the crucial theory for the inner planets, which would allow Copernicus to convert all the planets from epicyclic to eccentric models. Though Copernicus is sparing in his references and nowhere cites Regiomontanus for these propositions, his use of the 'Epitome' is well-documented, and there would seem to have been no other European source that he could have depended upon.

Whatever subsequent use was made of them, Regiomontanus's own motivation for including these propositions at the beginning of Book XII has remained unclear. ... What is especially odd about Regiomontanus's interest is that it is apparently so unprecedented. Neither in Europe nor in the Islamic world does this eccentric alternative alluded to by Ptolemy seem to have generated much interest. And the motivation to extend this alternative to the lower planets, after being rejected by the great authority himself, is even more puzzling. Finally, there is the odd way in which Regiomontanus presents the two propositions. He himself gives no motivation - he just presents them. There is no mention of Ptolemy, no statement that Ptolemy was wrong, no explanation of why Ptolemy made his mistake, no claim of credit.

One possibility is that Regiomontanus does not claim credit because he was not in fact the originator of the proposition. Indeed, it would seem, based on evidence presented in the sequel, that an older contemporary of Regiomontanus named Ali Qushji may well have been the discoverer of this crucial proposition and that Regiomontanus learned of it either while in Italy or through the intermediation of Cardinal Bessarion , who had originally suggested to Regiomontanus and his collaborator Georg Peurbach that they write the 'Epitome'.

Most readers of this journal will be acquainted with Regiomontanus and Peurbach, and perhaps even Bessarion, but Ali Qushji is most likely an unknown figure. This is regrettable since he is, at least in my opinion, one of the major figures in astronomy of the fifteenth century.
The work by Ali Qushji which contains these vital propositions is Treatise on the Eccentric Model Being Possible for the Two Lower Planets Just as for the Others. The article [11] contains an English translation of Ali Qushji's paper, while the thesis [8] contains another English translation with annotations.

We must now look to see why Ali Qushji is prepared to contradict Ptolemy. He had rejected Aristotle's approach to the philosophy of science and produced his own philosophical principles of the [5]:-
... conception of existence, existents, nature, knowledge, and language. As for the mathematical sciences, Ali Qushji in general tried to free them from Hermetic-Pythagorean mysticism and to provide an alternative to Aristotelian physics as the basis for astronomy and optics.
It was this philosophy, which pervades all his work, which allowed him to suggest that Ptolemy was wrong and he could consider the possibility that the earth moved, in particular that it rotated. It also encouraged him to consider mathematics as a tool in understanding the physical world and not as an abstract subject of interest in its own right. As Mustapha Kara-Ali writes in [8], Ali Qushji thought that:-
... mathematical entities are not abstracted from sensory data, but are rather attained through human activity such as counting, ordering, comparing, etc.
Although what we have described above may be the most important of Ali Qushji's contributions, we note that he was in fact a prolific author with interests in a wide range of topics. Today at least 270 manuscript copies of his writings are extant covering works with 43 distinct titles. There are 13 distinct works on mathematics and astronomy, 7 on theology and jurisprudence, and 24 on literary topics especially grammar and linguistics. Before the recent discovery of his indirect influence on Copernicus, his most important work was considered to be a major work on Islamic philosophy which, in fact, is a commentary on a work by Nasir al-Din al-Tusi (1201-1274). Latin translations of Ali Qushji's Tract on Arithmetic and his Tract on Astronomy were made by John Greaves and published in 1650. Annotated English translations of the following two works by Ali Qushji are given by Mustapha Kara-Ali in [8]: Treatise on the Eccentric Model Being Possible for the Two Lower Planets; and Treatise Regarding the Solution to the Equant Problem.

Finally, we note that he calculated the longitude of Constantinople as 41°14', close to the modern value of 41°01'. He was a major figure in assisting in compiling Ulugh Beg's star catalogue, the Zij-i Sultani. This was the most accurate star catalogue of its time and was only surpassed by the work of Tycho Brahe 150 years later. There is some doubt about the extent of Ali Qushji's contributions to the star catalogue, however, since he published Sharh-i Zij Ulugh Beg which was a commentary on Ulugh Beg's Zij-i Sultani in which Ali Qushji made criticisms of it and pointed out some mistakes.

Let us end with the following quote from [8]:-
Ali Qushji's views were debated for centuries after his death, and he exerted a profound influence on Ottoman-Turkish thought and scientific inquiry, in particular through the madrasa and its curriculum. His influence also extended to Central Asia and Iran, and it has been argued that he may well have had an influence, either directly or indirectly, upon early modern European science, to which his ideas bear a striking resemblance.

References (show)

  1. Ali Kuscu, Ottoman History.
  2. S Ali Shahbaz, Ali Qushji, the famous Iranian theologian, astronomer and mathematician.
  3. T R Dergisi, Turkish Scientist from Past to Present.
  4. I Fazlioglu, Ali Al-Qushji (Abu Al-Qasim Ala Al-Din Ali Ibn Muhammad Qushji-Zade),
  5. I Fazlioglu, Ali Al-Qushji (Abu Al-Qasim Ala Al-Din Ali Ibn Muhammad Qushji-Zade), in Thomas Hockey et al. (eds.), The Biographical Encyclopedia of Astronomers (Springer, New York, 2007, 946-948.
  6. I Ileri, Ali Al-Qushji and His Contributions to Mathematics and Astronomy, Muslim Heritage (12 August 2011).
  7. I Ileri, Ali Al-Qushji and His Contributions to Mathematics and Astronomy, Journal of the Center for Ottoman Studies, Ankara University (OTAM) 20 (2006), 175-183.
  8. M Kara-Ali, Constructivism at the Birth of the Scientific Revolution: A Study of the Foundations of Qushji's Fifteenth Century Astronomy (Ph.D. thesis, International Islamic University of Malaysia, 2-14).
  9. S Mutlu, 546 years on death of 15th-century Turkish astronomer. Ali al-Qushji was also famous for his works on mathematics and linguistics, Anadolu Agency.
  10. Qushji: an anti-Aristotelian astronomer, a Muslim genius of Hagia Sophia, TRW World (6 August 2020).
  11. F J Ragep, Ali Qushji and Regiomontanus: Eccentric Transformations and Copernican Revolutions, Journal History of Astronomy 36 (2005), 359-371.
  12. G Saliba, Al-Qushji's Reform of the Ptolemaic Model for Mercury, Arabic Sciences and Philosophy 3 (1993), 161-203.
  13. S Shahriar and I Nikseresht, Qushji's Cosmology, Saving the Phenomena instead of Making Theory about the Motion of Celestial Bodies, Philosophy of Science, Institute for Humanities and Cultural Studies (IHCS) Biannual Journal 11 (1) (2021), 63-93.
  14. M B Vosooghi, Geographical Location of Silla in Muslim Astronomical Literature of the Thirteenth to Sixteenth Centuries CE, Acta Koreana 21 (1) (2018), 65-79.
  15. D C Waugh, Ulugh Beg and His Observatory, University of Washington (2002).

Additional Resources (show)

Other pages about Ali Qushji:

  1. Miller's postage stamps

Other websites about Ali Qushji:

  1. zbMATH entry

Cross-references (show)

Written by J J O'Connor and E F Robertson
Last Update March 2022