It was also his astronomical as well as his religious teachings that triggered the interest of his own student Niẓām al-Dīn al-Nīsābūrī (d. 1328), known as al-A'raj (The Lame), to write on these two subjects as well. Nīsābūrī's two voluminous astronomical works, Sharḥ al-tadhkira (Commentary on the Tadhkira), and Sharḥ al-majisṭī (Commentary on the Almagest), both commented on the two works of Ṭūsī's that are mentioned in the titles. And both of Nīsābūrī's works continued to be taught in schools well after the death of the author. A remark made in a fifteenth-century text about the astronomical education in the school of the most famous potentate and astronomer Ulugh Beg (d. 1449) attests to the use of Nīsābūrī's astronomical texts in the instruction.[298] But Nīsābūrī's commentary on the Qur'ān, Gharā'ib al-qur'ān wa-raghā'ib al-furqān (the Unusual [expressions] in the Qur'ān and the appealing [features] of the Furqan [a synonym of the Qur'ān]) is by far the most elaborate of his works as it falls in several volumes in the printed version.[299]
Ibn al-Shāṭir (d. 1375) of Damascus, of the great astronomical fame, was only a muwaqqit (Timekeeper) at the Umayyad mosque in the same city.[300]As a functionary of the mosque he must have derived his livelihood from the religious endowment of the mosque, and just like a judge was also considered a religious functionary. He apparently conducted his theoretical research on planetary motions in perfect synchronism with his religious duties. Naturally, he also developed instruments, such as sundials and the like, to tell the appropriate times of prayers as part of his religious duties, but also must have enjoyed developing them for their mathematical projection interest. His astronomical work, however, has now become of great interest after it was demonstrated, in the late 1950's, that his lunar model was identical to that of Copernicus, and his technical treatment of the motion of the planet Mercury used the same Ṭūsī Couple that was used by Copernicus as well. His model for the upper planets, which was also adopted by Copernicus after shifting the center of the universe to the sun, also included the use of 'Urḍī's Lemma, and continues to be at the center of the ongoing research that will one day determine the routes by which Copernicus knew of this astronomer's work and of the work of his colleagues from the Islamic domain.
Mullā Fatḥallāh al-Shirwānī (c. 1440) who also wrote a commentary on Ṭūsī's Tadhkira, also called Sharḥ al-tadhkira, from which we know a great deal about the astronomical activities at Ulugh Beg's school, was obviously first and foremost a religious functionary as his title Mullā implies. In addition he was apparently one of the brightest students of Qāḍīzādeh al-Rūmī in astronomy. Some of his religious works have also survived to attest to his engagement in the religious fields as well.[301]
Finally, the works of the most prolific astronomer of the sixteenth century, Shams al-Dīn al-Khafrī (d. 1550), which we have considered at more than one occasion before as examples of the latest sophistication in Islamic astronomy, were at the same time the best examples of the use of mathematics as a language of science. This brilliant astronomer was also a renowned religious scholar in his own right.[302] His biographers, who speak of him mainly as a religious scholar, only marginally mention his most famous astronomical work al-Takmila fī sharḥ al-tadhkira (Completing the Commentary on the Tadhkira). At one point in his career he apparently fulfilled the function of the official Shfite jurist in Safavid Iran. The same biographers also report his issuing juridical opinions (fatwas) on matters pertaining to the Shi'ī doctrines before the arrival of al-Muḥaqqiq 'Alī b. Al-Ḥusain al-'Āmilī (d. 1553) from Lebanon to that country in the early part of the sixteenth century.[303]
The intersections between theoretical astronomy with philosophy and with religion are too numerous to recount. It is certain, however, that both of those disciplines had a very fruitful interaction with Islamic theoretical astronomy, thus allowing the latter to cast doubt on much of the Aristotelian cosmology in the first instance, and to reconstruct itself as a religiously acceptable science in the eyes of religious authority in the second. This association with religion, contrary to what one would expect when using the
European paradigm of conflict between science and religion, was apparently very healthy, and continued to support astronomers, one after the other, even at times when the astronomers' only source of income was provided by the religious institutions in which they served.
With this image, it becomes very difficult to document a paradigm of conflict between religion and science in Islamic society. But this does not mean that all astronomical disciplines were treated in the same fashion. One can easily document a conflict between religion and astrology as we have said several times before, since astrology was perceived early on as the purpose of astronomical research in the first place in full conformity with the Greek tradition.[304] But this does not mean that astrology was completely banished from Islamic society.
One can also consider the tenuous relationship between the production of zījes that served as ephemerid tables for the astrologers, and the later production of mīqāt tables that served only religious purposes. Ibn al-Shāṭir's al-Zīj al-jadīd, for example, can function as a tool for astrologers, despite the author's original intention to use it mostly for his religious timekeeping activities. It is in such areas that the disciplinary borders begin to be blurred, and the difficulty arises when attempting to characterize a specific production one way or the other.
6. Islamic Science and Renaissance Europe: The Copernican Connection
The new mathematical tools that were developed by the astronomers of the Islamic world did not only prove to be very useful for the emergence of new ways of looking at theoretical astronomy, as we have already seen, but also allowed astronomers to manipulate mathematical models so that they could meet the observational requirements. We have also seen this trend culminate in the works of Khafrī who demonstrated a total mastery of mathematics so much so that he attained complete freedom to use whatever mathematical configuration he wished in order to represent the same physical observational phenomenon. Mathematics became a new language, and became an efficient tool of astronomy, at least as far as the works of Khafrī were concerned.
The works of Ibn al-Shāṭir, on the other hand, with their emphasis on the strict Aristotelian cosmological requirements of abolishing eccentrics, also liberated astronomical models from the often cumbersome multiplicity of shapes and forms and unified all the planetary models with one geocentric format that could be easily applied to one planet at a time by simply changing the parameters of the two epicyclic spheres deployed in each model. In a roundabout way, the unintended consequences of these unified models produced the "strange" development that allowed them to be transferred into heliocentric models, despite the fact that there was no shred of support for such heliocentrism in the then reigning Aristotelian cosmology. All that someone like Copernicus had to do was to take any of Ibn al-Shāṭir's models, hold the sun fixed and then allow the Earth's sphere, together with all the other planetary spheres that were centered on it, to revolve around the sun instead. As we shall soon see that was the very step that was taken by Copernicus when he seemed to have adopted the same geocentric models as those of Ibn al-Shāṭir and then translated them to heliocentric ones whenever the situation called for it.
298
See G. Saliba, "Reform of Ptolemaic Astronomy at the Court of Ulugh Beg",
300
See David King,
301
See George Saliba, "Reform", and Tashküprüzadeh (d. 1561),