Обсуждение:Астрономия

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Encyclopaedia of Islam, Second Edition / ʿIlm al-Hayʾa

ʿIlm al-Hayʾa — the “science of the figure (of the heavens)” or astronomy (which is also known by several other names in Arabic), is that branch of knowledge which deals with the geometrical structure of the universe, which determines the laws governing the periodic motions of the celestial bodies, which devises cinematic models to describe these motions, which reduces them to tabular form so that a computer can, with as much precision and ease as possible, determine the positions of the heavenly bodies as seen from any particular locality on the surface of the earth, and which invents and employs the instruments necessary to guarantee the utmost accuracy in observations.

The geometrical structure of the universe, as conceived by Muslim astronomers after about 800 A.D., by and large coincides with that expounded by Ptolemy in his Almagest . The earth rests motionless near the centre of a series of eight spheres which encompass it. The eighth sphere, studded with the fixed stars which were duly catalogued by such scholars as al-Ṣūfī (d. 376/986), revolves daily from East to West; it also moves in the opposite direction at an appropriate rate of precession, or oscillates with a motion termed trepidation (this theory is primarily known through T̲h̲ābit b. Ḳurra and various Spanish astronomers). The spheres of the five “star-planets”, which are eccentric to the centre of the earth, revolve in such a fashion that their centres of uniform ¶ motion (equants) are not identical with their geometric centres; the model of Mercury has, as a special arrangement, a “crank mechanism” which produces two perigees in its orbit. On the surface of these spheres are situated the centres of the planets’ epicycles. The model of the Sun, however, involves only an eccentric circle, while that of the Moon utilizes both a “crank mechanism” which causes the centre of its deferent to revolve about the centre of the earth, and an epicycle in which the anomalistic motion is counted not from the epicyclic apogee, but from a point on the line extended from the “opposite point” on the circumference of the “crank mechanism” through the centre of the epicycle. Muslim astronomy is largely concerned with expounding the intricacies of this system and with refining the parameters which transform it from a qualitative to a quantitative model of celestial motions; the core of the zīd̲j̲es is constituted by the tables based on the regular motions of the various parts of the model and their determined parameters. It might be well to mention here that the translations of Indian and Sasanian astronomical books to which reference will shortly be made contributed methods of computation, parameters, and tables to Muslim astronomy rather than geometrical models of the planetary orbs (Yaʿḳūb b. Ṭāriḳ’s Tarkīb al-aflāk is an exception to this rule); thus they did not modify the Ptolemaic view of the heavens outlined above.

Following the author of the Almagest, Muslim astronomers generally regarded the whole system purely as a mathematical construct having no necessary physical counterpart. But Ibn al-Hayt̲h̲am [q.v.] (d. 430/1039), continuing a tradition already begun in the second book of Ptolemy’s own Hypotheses , argued that the models in the Almagest are in fact physical realities. The problem facing those who accepted this view was one of reconciling these models with Aristotelian physics, in which only uniform circular motion concentric with the centre of the earth is possible for celestial bodies. Spanish philosophers, beginning with Ibn Bād̲j̲d̲j̲a (d. 533/1138-9) and continuing with Ibn Ṭufayl, Ibn Rus̲h̲d, and al-Biṭrūd̲j̲ī [qq.v.], attempted to solve this problem either partially by eliminating the epicycles, or wholly by removing both epicycles and eccentric circles from the etherial parts of the universe. The results of their efforts were not astronomically impressive. But the problem was approached from a more realistic standpoint in Marāg̲h̲a, Tabrīz, and Damascus in the late 7th/13th century and the early 8th/14th. There the goal was only to eliminate the most non-Aristotelian elements in the Ptolemaic system—the equants and the Moon’s “opposite point”—so that the motions of the heavenly bodies might be explained exclusively as the combinations of uniform circular motions. The success of the School of Marāg̲h̲a and the later influence of its solutions will be touched upon below.

The Arabs had not always been endowed with a knowledge of Ptolemaic astronomy, however. In the pre-Islamic period and in the first century of Islam the only reflections of any ʿilm al-hayʾa among them are a very crude method of telling the time of night by means of the twenty-eight lunar mansions ( manāzil al-ḳamar ) and a rough estimation of the seasons by means of their heliacal risings or cosmic settings ( anwāʾ ). But in the 2nd and 3rd centuries from the Hid̲j̲ra—that is, at the end of the Umayyad Dynasty and in the first one hundred and fifty years of the ʿAbbāsid—numerous texts on astronomy (and ¶ on astrology involving à knowledge of astronomy) were translated into Arabic from Sanskrit, Pahlavi, Greek, and Syriac. For the first half or so of this period of translation Arabic astronomers were extremely eclectic, and this trend toward eclecticism continued to be strong for a much longer period in certain areas such as Spain. But the introduction of Ptolemy’s rigorous methods and geometrical proofs at the beginning of the 3rd/9th century led to a rapid growth of observational astronomy, designed partly to investigate the discrepancies among the Greek, Iranian, and Indian systems, and partly to improve the Ptolemaic parameters. With the gradual recognition of the superiority of the Ptolemaic system, at least within the terms of the strongly Greek-oriented intellectual atmosphere that developed in Islam, the Almagest usurped a position of unchallenged preeminence in the estimation of most Muslim astronomers. This process was completed by the time of the publication of his Zīd̲j̲ al-Ṣābiʾ by al-Battānī in about 900 A.D.; and, despite the Indianizing tendencies of the Andalusians, the attacks of the Aristotelians, and the successes of the School of Marāg̲h̲a, Ptolemy remained in his position of dominance until the introduction of modern Western astronomy in fairly recent times.

The translations from Sanskrit.

The earliest translation of a Sanskrit astronomical text into Arabic was apparently that of the Zīd̲j̲ al-Arkand ( arkand is a corruption of the Sanskrit ahargaṇa ) made in Sind shortly after 117/735; on it were based two other zīd̲j̲es , the Zīd̲j̲ al-Hazūr and the Zīd̲j̲ , al-Ḏj̲āmiʿ , both composed in Ḳandahār in the 2nd/8th century. The elements of the Zīd̲j̲ al-Arkand evidently were largely derived from the Khaṇḍakhādyaka written by Brahmagupta of Bhillamāla in A.D. 665, though it was also influenced by the Zīd̲j̲ al-S̲h̲āh of Yazdid̲j̲ird III (632-652), which, like the Khaṇakhādyaka , belongs to the Midnight School ( ārdharātrika ) of Āryabhaṭa (b. 476).

In 742 yet another Sanskrit zīd̲j̲ was translated into Arabic. This work, composed in verse in imitation of the Indian texts, was given the name Zīd̲j̲ al-Harḳan , wherein harḳan clearly represents another corruption of the Sanskrit ahargaṇa. This zīd̲j̲ was based on the Sunrise School ( audayika ) of Āryabhaṭa —i.e., on the Āryabhaṭīya that he wrote in 499.

The most important translation from Sanskrit into Arabic, however, was that of the Mahāsiddhānta belonging to the School of Brahma ( brāhmapakṣa ); the Mahāsiddhānta was primarily based on the Paitāmahasiddhānta (first half of the fifth century) of the Viṣṇudharmottarapurāṇa and on the Brāhmaspuṭasiddhānta written by Brahmagupta in 628, though some elements derived from the Āryabhaṭīya are discernible in its fragmentary remains. The occasion for the translation was provided by the visit to the court of al-Manṣūr at Bag̲h̲dād of an embassy from Sind in 154/771 or 156/773; the translator is alleged to have been al-Fazārī, who, in his Zīd̲j̲ al-Sindhind al-kabīr , mixes Iranian material in with the Indian. Al-Fazārī also wrote a Zīd̲j̲ ʿalā sinī al-ʿArab , based on his earlier work, which must have been the first set of astronomical tables to employ the Arabic calendar; the date of this work is c. 790. Another scholar who evidently had independent access to the Mahāsiddhānta, Yaʿḳūb b. Ṭāriḳ, composed a Tarkīb al-aflāk in 777 or 778 A.D. as well as a zīd̲j̲ and a Kitāb al-ʿilal , all of which reflect a mixture of Indian and Iranian elements. These works of al-Fazārī and of Yaʿḳūb constitute the ¶ basis of the Sindhind tradition, which will be discussed further below.

At some time around 800 another Arabic version of the. Āryabhaṭīya known as the Zīd̲j̲ al-Ard̲j̲abhat began to circulate among Muslim astronomers. The only one to follow it was apparently one Abu ’l-Ḥasan al-Ahwāzī, though it was also certainly known to Abu Maʿs̲h̲ar [q.v.] (d. 272/886). None of the works mentioned in this section or in the next, it should be noted, is extant; the account given here, then, may well be in need of some revision, and certainly will not be free from controversy.

The translations from Pahlavi.

Sasanian literature on astronomy, like that on astrology (both are known primarily through Arabic translations and adaptations), was an amalgamation of Greek and Indian material. Ptolemy’s Almagest existed in a Pahlavi translation already in the third century, and a text belonging to the Midnight School of Āryabhaṭa was available by 556; one belonging to the brāhmapakṣa may have been known as early as 450. The “Royal Astronomical Tables” or Zīk ī Šahriyārān as revised for Anūs̲h̲irwān in 556 was used by Mās̲h̲āʾallāh in c. 780-810 A.D., but may never have been translated into Arabic. The later version, published under Yazdid̲j̲ird III, was turned into Arabic, however, by one al-Tamīmī under the title Zīd̲j̲ al-S̲h̲āh. This was drawn upon by al-Fazārī (especially for its planetary equations) and by Abū Maʿs̲h̲ar; manuscripts of it were still circulating in the time of al-Birūnī [q.v.].

The translations from Greek and Syriac.

The most important Greek text on astronomy translated into Arabic was, of course, the Almagest of Ptolemy; translations were made from both the original Greek and a Syriac version. That due to al-Ḥad̲j̲d̲j̲ād̲j̲ in the first years of the 3rd/9th century exercised a strong influence over the astronomers gathered together by al-Maʾmūn; but the most authoritative version was that produced by Isḥāḳ b. Ḥunayn and corrected by T̲h̲ābit b. Ḳurra [qq.v.]. During the course of the 3rd/9th century Ptolemy’s Hypotheses , Theon’s “Handy Tables”, and the corpus of minor Greek astronomical writings known as the “Little Astronomy” (or later, when it became conventional to begin the study of astronomy by mastering Euclid’s Elements , as the “Middle Astronomy”) were also translated into Arabic, and a number of treatises on the astrolabe based on Greek and Syriac sources were published. This material, to a greater or lesser extent influenced by the translations from Sanskrit and Pahlavi (the most impressive influence is to be seen in the Muslim development of a trigonometry far more effective than Ptolemy’s out of the Indian system which employs only the sine, cosine, and versine functions), forms the central core of Islamic astronomy after the ninth century.

The Ptolemaic tradition.

Arabic texts on planetary theory and the structure of the universe, as indicated above, normally reflect the Ptolemaic system. But, because of the paucity of detailed studies, it is at present difficult to assess the extent to which any particular set of astronomical tables or zīd̲j̲ has depended on Indian, Persian, or Greek material. It is clear, however, that even in the majority of Ptolemaic zīd̲j̲es one will find parameters, methods of computation, or other elements derived from the Sindhind or the S̲h̲āh . This is true of the Zīd̲j̲ al-mumtaḥan of Yaḥyā b. Abī ’l-Manṣūr ¶ (c. 214/829) and in the several zīd̲j̲es of Ḥabas̲h̲ (c. 235/850); Abū Maʿs̲h̲ar in his Zīd̲j̲ al-hazārāt made a conscious effort to combine the three systems in order to substantiate his claim that they are all descended from a unique ante-Diluvian revelation.

The Zīd̲j̲ al-Ṣābiʾ of al-Battānī (c. 287/900), however, is almost entirely Ptolemaic; in this it presumably reflects the strong Hellenistic atmosphere of the Syrian, and particularly the Ḥarrānian, astronomical and astrological schools. Al-Battānī’s parameters were adopted by Kūs̲h̲yār b. Labbān (c. 400/1010), though Kūs̲h̲yār was generally a follower of Abū Maʿs̲h̲ar in his astrological works, and one suspects that this influence can also be traced in his zīd̲j̲es. The Zīd̲j̲ al-kabīr al-Ḥākimī written by Ibn Yūnis (c. 380/990) in Cairo is extremely important for the historical information it contains. Al-Ḳānūn al-Masʿūdī of al-Bīrūnī (421/1030), whose works are also of immense importance for their historical information, often reflects the author’s interest in Indian astronomy. The Zīd̲j̲ al-Sand̲j̲arī was composed by al-K̲h̲āzinī (c. 514/1120) in Iran; an epitome of it was translated into Greek by Gregory Chioniades, who obtained the manuscript at Tabrīz, in c. 700/1300. Al-K̲h̲āzinī, despite his interest in Abū Maʿs̲h̲ar’s Indian theory of cycles, continues to compute according to the Ptolemaic tradition. And the Zīd̲j̲ al-ʿAlāʾī of al-Fahhād (c. 545/1150), not extent in its original form, was one of the texts translated into Greek by Chioniades, and its elements were used by al-Fārisī (c. 658/1260) in his Zīd̲j̲ al-mumtaḥan al-Muẓaffarī .

The Sindhind tradition.

The foundation of this tradition lies in the works of al-Fazārī and Yaʿḳūb b. Ṭāriḳ, wherein already, as we have seen, some Sasanian and Greek elements had been mingled with the brāhmapakṣa and Āryabhaṭiya material. But the most influential representative of this tradition was the Zīd̲j̲ al-Sindhind of al-K̲h̲uwārizmī [q.v.] (c. 215/830). Only fragments of the original text survive, but we do have a Latin translation of the revision made by al-Mad̲j̲rīṭī in Cordova (c. 390/1000); the translator was Adelard of Bath (1126). We also have commentaries on al-K̲h̲uwārizmī’s zīd̲j̲ written by al-Masrūr (c. 261-875) and by Ibn al-Mut̲h̲annā (4th/10th century; this commentary survives only in Latin and Hebrew translations made in Spain) as well as fragments of the commentary composed by al-Farg̲h̲ānī [q.v.] (c. 235/850). The details of the preservation of al-K̲h̲uwārizmī’s work that have just been given are indicative of the strong Andalusian predilection for the Sindhind; this impression is strengthened by the fact that the Naẓm al-ʿiḳd of Ibn al-Adamī (c. 308/920), one of the principal Eastern representatives of the Sindhind tradition, is primarily known through a quotation in Ṣāʿid al-Andalusī. The two other Eastern zīd̲j̲es which followed the Sindhind after 900—the zīd̲j̲ of al-Nayrīzī (c. 287/900) and that of the Banū Amād̲j̲ur (c. 297/910)—are mainly known from citations in Ibn Yūnis and in al-Bīrūnī.

In Spain the tradition was continued by al-Mad̲j̲rīṭī’s pupil, Ibn al-Samḥ (416/1025), whose zīd̲j̲ is available in fragmentary form; the zīd̲j̲ of Ibn al-Ṣaffār is probably also lost, though a manuscript in Paris may contain it. But the principal zīd̲j̲ of Muslim Spain was the “Toledan Tables” of al-Zarḳālla (c. 473/1080); this work is a mixture of materials from al-K̲h̲uwārizmī and al-Battānī. It had an enormous influence among Muslim (Ibn Kammād, ¶ Ibn al-Bannāʾ, etc.), Jewish (Abraham ben Ezra, Profatius, etc.), and Christian (the “Alfonsine Tables” and its successors) astronomers in Western Europe until the end of the 15th century.

The School of Marāg̲h̲a.

Spain, as we have seen, was the home not only of the Sindhind tradition, but also of the Aristotelian assault on Ptolemy. Far more impressive astronomically was the effort generated at the observatory at Marāg̲h̲a (founded by Naṣīr al-Dīn al-Ṭūsī in 657/1259) to modify Ptolemaic theory, and continued at its successors at Tabriz and Damascus. At Marāg̲h̲a itself, where Chinese astronomers assisted their Muslim colleagues, the problem of revising Ptolemaic astronomy was seen as being essentially that of replacing the equant of each planet so that all celestial motions might be uniformly circular. The Ṭūsī couple invented by Naṣīr al-Dīn and explained in his Tad̲h̲kira provided the basic approach for the solutions later proposed by his pupil, Ḳuṭb al-Dīn al-S̲h̲īrāzī. in 680/1281 and 683/1284, and by Ibn al-S̲h̲āṭir of Damascus in c. 750/1350, though each of them advocated different numbers, dimensions, and arrangements of the epicycles. It was only Ibn al-S̲h̲āṭir who finally reached a satisfactory solution for the two most difficult planets, Mercury and the Moon; but by the middle of the 8th/14th century, then, Muslim astronomy had worked out planetary models that depended solely on combinations of uniform circular motions, eliminating the equants from the models of the five “star-planets”, and the “crank mechanism” and “opposite point” from that of the Moon.

This accomplishment of Ibn al-S̲h̲āṭir shares many features with the models proposed by Copernicus two centuries later; in particular, their models of the Moon and of Mercury are identical, they both employ the Ṭūsī couple, and they both eliminate the equants in essentially the same way. There can be little doubt, then, that Copernicus knew of Ibn al-S̲h̲āṭir’s work; the details of the transmission, however, remain obscure. It is true that manuscripts of the Greek translations of various Arabic zīd̲j̲es made by Gregory Chioniades in c. 1300 upon his return to Constantinople after his studies at the observatory at Tabriz were in Italy by the middle of the fifteenth century, and that they contain diagrams apparently illustrating the Ṭūsī couple, but they contain no details about Ḳuṭb al-Dīn’s work and are, of course, too early to have been influenced by Ibn al-S̲h̲āṭir. Some other intermediary must have existed.

The later observatories.

The observatory at Marāg̲h̲a and the zīd̲j̲ which it produced—the Zīd̲j̲-i Īlk̲h̲ānī —served as a model for later Muslim astronomical efforts, though the modifications of Ptolemaic theory that we have just described are not known to have been influential in Islam after the 8th/14th century. The most famous imitator was the observatory founded by Ulug̲h̲ Beg at Samarḳand in 823/1420, where a number of astronomers headed by al-Kās̲h̲ī and Ḳāḍīzāda prepared a Zīd̲j̲-i Sulṭānī (c. 844/1440); al-Kās̲h̲ī also published a zīd̲j̲ of his own, the Zīd̲j̲-i K̲h̲āḳānī . All three of these zīd̲j̲es are essentially Ptolemaic, though improvements are made in the parameters and in the structure of some of the tables, and material on the Chinese-Uyg̲h̲ur calendar is added to the other calendaric information common to all astronomical tables.

The last important Muslim observatory was built for Taḳī al-Dīn in Istanbul between 983/1575 and ¶ 985/1577. But the five observatories built in imitation of that at Samarḳand by D̲j̲ayasimha. the Mahārād̲j̲a of Amber from 1693 to 1743, at D̲j̲ayapura, Ud̲j̲d̲j̲ayinī, Delhi, Mathurā, and Varāṇasī deserve to be mentioned, as they represent an attempt, though an abortive one, to revise Indian astronomy so as to make it conform to the Muslim Ptolemaic tradition. A more fruitful influence of the later Muslim observatories on their neighbours was that exercised by Marāg̲h̲a, Samarḳand, and Istanbul upon European astronomy; several of the instruments and some of the organizational features of these establishments appeared at Tycho Brahe’s Uraniborg (1576) and Stjerneborg (1584) observatories. The development of the astronomical observatory, the achievement of the School of Marāg̲h̲a, the advances in trigonometry and in the structure of tables, and the constant attempts to improve parameters stand out as the most impressive accomplishments of Islamic astronomy.

Bibliography

The vastness of the field of Muslim astronomy obviously precludes any extensive listing of the relevant literature

the following notice mentions only standard reference works and the latest books and articles reflecting advances in our knowledge of specific aspects of the subject. The standard reference work for the astronomers themselves and their works remains, despite its age, H. Suter’s Die Mathematiker und Astrotwmen der Araber und ihre Werke, Abhandlungen zur Geschichte der Mathematischen Wissenschaften, x, Leipzig 1900 (reprinted Ann Arbor 1963)

this can be supplemented by H. P. J. Renaud’s article in Isis, xviii (1932), 166-83, by C. Brockelmann’s GAL, Pearson, and by the relevant articles in the Encyclopaedia of Islam and in the forthcoming Dictionary of Scientific Biography. The fullest account of the zīd̲j̲es is E. S. Kennedy’s A survey of Islamic Astronomical Tables, Transactions of the American Philosophical Society, NS xlvi/2, Philadelphia 1956. The best introduction to Islamic astronomy is C. A. Nallino’s ʿIlm al-falak, Rome 1911-12

there is an Italian translation by M. Nallino in C. A. Nallino, Raccolta di scritti editi e inediti, v, Rome 1944, 88-329.

For the literature concerning the period of translations the reader may refer to the references given in D. Pingree, The fragments of the works of al-Fazārī, in JNES, xxviii (1969). The history of Islamic astronomy in Spain and its influence on Latin and Hebrew astronomy is dealt with in a series of articles by O. Neugebauer, J. M. Millás Vallicrosa, B. Goldstein, P. Kunitzsch, G. Toomer, and others

there are articles on the influence of Muslim astronomy on Byzantium by O. Neugebauer, D. Pingree, and P. Kunitzsch. Muslim observatories are investigated in A. Sayili’s The Observatory in Islam, Publications of the Turkish Historical Society, series vii, no. 38, Ankara 1960. And a summary of the recent work on the School of Marāg̲h̲a together with the relevant bibliography will be found in E. S. Kennedy’s Late medieval planetary theory, in Isis, lvii (1966), 365-78. Each of the subjects mentioned in this paragraph is presently being intensively explored

any future reader of this article should expect to find that enormous advances have been made in our knowledge of them.

(D. Pingree)

Cite this page

Pingree, D., “ʿIlm al-Hayʾa”, in: Encyclopaedia of Islam, Second Edition, Edited by: P. Bearman, Th. Bianquis, C.E. Bosworth, E. van Donzel, W.P. Heinrichs. Consulted online on 10 January 2017 <http://dx.doi.org/10.1163/1573-3912_islam_COM_0365>