A Brief Overview Of Muslim Astronomers
Much has been written regarding the historical progression that the early and medieval astronomy of Islam served, in a role of transmitting ancient Greek works to early unique Europe. Others have countered this with expositions of the greatness of Islamic astronomy itself. The reality of Islamic astronomical achievements exists somewhere in between, within a complex system of intellectual exchange, debate, and controversy generated over the course of several centuries. Certainly Muslim astronomers contributed greatly to their field during the so-called golden age of Islam between the ninth and fifteenth centuries. Starting in the eight century, Muslim scientists integrated the astronomical traditions of not just the Greeks but other ancient cultures including the Persians, the Indians, and the ancient Near East. and astronomy together were known as the "science of the stars" ('ilm al-nujum), while astronomy was known as the "science of the spheres" ('ilm al-falak) or more commonly, "science of the heavenly configurations" ('ilm al-hay'a).
Intelligent developments in immense instruments and impressive observatories marked astronomical development in the medieval Muslim world. One of the most notable in his varied scientific achievements was al-Battani (ca AD 853 - 929) who recorded detailed observations of the stars and planets in astronomical tables (zij). The astronomical tables recorded by various Muslim astronomers also included those of al-Ma'mun observed in Baghdad, the Hakimite zij of Cairo, the Toledan Tables of al-Zarqali and his associates, the el-Khanid zij of Nasir al-Din al-Tusi observed in the famous Maragha observatory, and the zij of Ulugh-Beg from Samarkand had likely (but yet not properly researched) influence on European astronomy at least up to the time of astronomer Tycho Brahe. Meanwhile, the works of Ibn Sina, Abu al-Barakat al-Baghdadi, Ibn Bajjah and others led to the development of the understanding of impetus and momentum, principles in physics that are applied to motion of bodies in astronomy. The Arab astrolabe was a crucial invention well known and used in Christian societies.
The Ptolemaic model was deconstructed by Muslim astronomers long before it began to fully unravel in Europe's "Copernican revolution." Spanish Muslim al-Bitruji (Latinized as Alpetragius) wrote Kitab fi' l-hayat (De motibus celorum) around 1185 which "made the reform of Ptolemaic astronomy a necessity." (Saliba, p 63) His motivation was the conviction that Ptolemy's system could not physically exist, instead describing the cosmos as it was including all appearances. Ptolemaic eccentrics and epicycles were replaced with spiral motions. Al-Bitruji hypothesized that the poles of each sphere rotated on small circles around the poles of other spheres. While he retained the Aristotelian concept of spherical heavens, he rejected the view that movement was caused by some intelligence in favor of a mechanical devolution of energy from outermost spheres. The lowest sphere was water, which no longer moved much but whose movement could be seen in the tides, according to al-Bitruji. According to Dales, this work was "well known to the more serious thinkers of the thirteenth century." (p 539) The work of al-Bitruji was a culmination of traditions started with Ibn Tufayl (Latinized as Abubacer), who is credited in Kitab fi' l-hayat. Other attempts to formulate non-Ptolemaic astronomical theories were made by Mu'ayyad al-Din al-'Urdi (d. 1266), Nasir al-Din al-Tusi (d. 1274), Qutb al-din al-Shirazi (d. 1311) and Ibn al-Shatir al-Dimashqi (d. 1375).
The end result of al-Bitruji's work was in many ways inferior to that of Ptolemy's, but indicates the general dissatisfaction with veteran systems and the search for new explanations of heavenly movements. Translations of Ptolemy, Aristotle, and other extinct cosmologists were always subject to lengthy interpretations and commentaries. Even the basic purpose of translation was not enough to satisfy Islamic astronomers. By the time Aristotle was transmitted to Europe, his writings came accompanied by a such vast corpus of text that the general view of early novel scholars was not the one of Aristotle, but one of medieval Islamic Aristotelianism. While no closer to the truth, this questioning of the existing order is symptomatic of a scholarly culture in the dar al-Islam that encouraged scientific innovation.
This culture of innovation is perhaps best exemplified in the Maragha School, named after the observatory in northern Iraq. This "group of very original astronomers" (Saliba, p 145) included its director Naris al-Din al-Tusi (d. 1274) who who wrote an account of the Almagest while adding improvements and propositions by later astronomers. The observatory was founded in AD 1259 and survived until at least 1316. The astronomer Maghribi worked at the observatory and shows in his work a sophistication in the general program to update Ptolemaic parameters. According to Saliba "no other similar activity before the Copernican observations" (p 229) took space. The main purpose of the observatory was the improvement of Ptolemaic data, and activities included building necessary instruments in order to produce updated zij to improve astrological results.
Efforts to resolve what is commonly referred to as the "problem of the equant" in Ptolemy's work began in earnest sometime around the mid- thirteenth century. Astronomers focused on inventing non-Ptolemaic mathematical models that would fit celestial motions to observations while consistent with the physical properties of the pretty spheres. Two new systems were put together by Mu'ayyad al-Din al-Urdi (d. 1266) and Nasir al-Din al-Tusi, developing two theorems that are now known in the literature as the Tusi Couple and the Urdi Lemma. in the fourteenth century, Ibn al-Shatir (d. 1375) made use of these earlier mathematical theorems and went on to devise a fresh set of models to meet the criteria of consistency between physical properties and mathematical descriptions.
The ninth through fifteenth centuries was the prime era of current radiant production in the Islamic world. During this time the Maragha School revolution exemplified a high point, the culmination of Ptolemaic critique that began in the eleventh century. Saliba refers to the mid-thirteenth to mid-fourteenth century as the "Golden Age of Arabic Astronomy" in light of activities both at the Maragha observatory specifically and in the dar al-Islamgenera. Original astronomical achievements abounded, as seen in the two influential theories known as the Tusi couple and the Lemma of Urdi.
There were several other major attempts at resolving the Ptolemaic problem. According to al-Haytham (d ca 1048) there could not be a sphere that moved uniformly around an axis within a physical universe. The Ptolemaic equant violated this opinion and thus the Almagestcould not be describing a precise physical universe. His ideas were put forth in a monumental observe of the Ptolemaic universe (al'Shukuk 'ala Batlamyus). Abu 'Ubayd al-Juzjani (d. ca AD 1070) wrote in a similar vein. The work of Abu 'Ubayd attempted to resolve the problematic equant, and various others followed these early writers to create new solutions. The four most influential astronomical theories throughout the medieval and early modern Islamic world were those created by al-'Urdi, al-Tusi, al-Shatir, and Ptolemy.
According to the standard historical belief, now going out of favor, the Muslim world was strengthened by the application of shari'a and the growth of Sufi mysticism and institutions after the mid-fourteenth century. Religious tribunals (ulema) issued fatwahs or religious rulings to guide legal opinions. Lewis writes that "if the strengthening of the shari'a dealt with the minds and social needs of Moslems, the Sufis dealt with the hearts and emotional needs." (p 836) Meanwhile the European Church was losing ground, first with the papacy moving to Avignon and later the split instigated by Martin Luther. Simultaneously the sciences had begun to flourish in Europe, where formal universities were established, while in the Muslim world the sciences including astronomy were losing momentum from previous centuries.
According to Charles Issawi, the Muslim world remained trustworthy to the Christian world until around the seventeenth century, witnessed in their comparative military abilities. While Europe has not yet caught up with Islamic sciences in early modern times, as in technological and agricultural advances "...[h]ere, too, something new had emerged, perhaps best exemplified by Henry the Navigator (1394-1460) and Leonardo da Vinci (1452-1519)." (Issawi, p 419) Issawi's description follows the common view that the scientific spirit slowly migrated from the Muslim world while awakening in Europe although he pushes the date to the fourteenth century instead of the twelfth century.
This standard model of Muslim scientific and intellectual decline has been seriously challenged by recent scholars in the last fourty years in light of new research into medieval manuscripts. According to George Saliba the period usually referred to as a decline was very productive for scientific astronomy with a variety of astronomical theories produced. The typically accepted dated decline of Islamic vivid work is the fall of the Abbasid caliphate after Baghdad was decimated by Mongols in 1258. More significantly, the standard cultural divisions of history has been challenged with new information showing stronger relationships between worlds in defiance of standardized hegemonies.
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Ihsanoglu, Ekmeledding. Ottomans and European Science. Science and Empires: Historical Studies about Scientific Development and European Expansion. Ed. Petitjean, Patrick. Jami, Catherine. Moulin, Anne-Marie. Boston: Kluwer Academic Publishers, (1992), pp. 37-48.
Carmody, Francis J. The Planetary Theory of Ibn Rushd. Osiris, Vol. 10. (1952), pp. 556-586.
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Lewis, Archibald R. The Islamic World and the Latin West, 1350-1500. Speculum, Vol. 65, No. 4. (Oct., 1990), pp. 833-844.
Martin, Richard C. Understanding the Qu'ran in Text and Context. History of Religions, Vol. 21, No. 4. (May, 1982), pp. 361-384.
Ragep, F Jamil. Freeing Astronomy from Philosophy: An Aspect of Islamic Influence on Science. Osiris, 2nd Series, Vol. 16, Science in Theistic Contexts: Cognitive Dimensions. (2001), pp. 49-64+66-71.
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