The Greek Influence on Early Islamic Mathematical Astronomy

Abstract

Some concepts of Greek mathematical astronomy reached Islam in the eighth century through translations and adaptations of Sanskrit and Pahiavi texts. These represented largely non-Ptolemaic ideas and methods which had been altered in one way or another in accordance with the traditions of India and Iran. When to this mingling of Greco-Indian and Greco-Iranian astronomy was added the more Ptolemaic Greco-Syrian in the late eighth and early ninth centuries, and the completely Ptolemaic Byzantine tradition during the course of the ninth, the attention of Islamic astronomers was turned to those areas where these several astronomical systems were in conflict. This led to the development in Islam of a mathematical astronomy that was essentially Ptolemaic, but in which new parameters were introduced and new solutions to problems in spherical trigonometry derived from India tended to replace those of the Almagest.THE PROBLEM OF THE INFLUENCE of Greek mathematical astronomy upon the Arabs (and in the following I have generally excluded from consideration the related problems of astronomical instruments and star-catalogues) is immensely complicated by the fact that the Hellenistic astronomical tradition had, together with Mesopotamian linear astronomy of the Achaemenld and Seleucld periods and its Greek adaptations, already Influenced Use other cultural traditions that contributed to the development of the science of astronomy within the area In which the Arabic language became the dominant means of scientific communication in and after the seventh century a.d. An Investigation of this probelm, then, must begin with a review of those centers of astronomical studies in the seventh and eighth centuries which can be demonstrated to have influenced astronomers who wrote in Arabic. This limitation by means of the criterion of demonstrable influence will effectively exclude Armenia, where Ananias of Shirak worked in the seventh century,1 and China, where older astronomical techniques,* some apparently derived ultimately from Mesopotamian sources,* were partially replaced by Indian adaptations of Greek and Greco-Babylonian techniques rendered into Chinese at the T'ang court in the early eighth century.4 But it leaves Byzantium, Syria, Sasanian Iran, and India.While astronomy had been studied at Athens by Proclus* and observations had been made by members of the Neoplatonic Academy In the fifth and early sixth centuries,* and while Ammonius, Eutoclus, Philoponus, and Simplicius had written about astronomical problems at Alexandria in the early sixth century,7 a hundred years later the tradition was transferred to Constantinople, where Stephanus of Alexandria-perhaps in imitation of the Sasanian Zlk-i Shahriyârân-prepared in 617/618 a set of instructions with examples illustrating the use of the Handy Tables of Theon for the Emperor Ileraclius.8 Such studies, however, were soon abandoned, not to be revived in Byzantium till the ninth century, when their restoration seems to have been due to the stimulus of the desire to emulate the achievements of the Arabs. Except for the texts of the Little Astronomy* and some passages reflecting Greco-Babylonian astronomy in pseudo-Heliodorus10 and Rhe- torlus of Egypt, Byzantine astronomy !n this period was solidly Ptolemaic.The history of astronomical writings In Syriac before the rise of Islam Is difficult to trace. The works of Bar Dal?an, hls pupil Philip, and of George, the Bishop of the Arabs, indicate that sufficient knowledge of the subject must have existed to permit the casting of horoscopes; for this all that Is really needed, of course, are tables, and It Is certain that a Syriac version of the Handy Tables existed.14 There may also have been a Syriac translation of Ptolemy's Syntaxis since some of the Arabic versions arc said to have been made from that language.1* In fact, It has been claimed that Sergius of Rtsh'alnA, the early sixth century translator, was responsible for the Syriac version,1' and In any case he did write on astrology and on the motion of the Sun. …