Al-Faz?r?, Mu?ammad Ibn Ibr?h?m

(fl. second half of the eighth century)

astronomy.

Al-Faz?r? came from an old Arab family (his genealogy is traced back twenty-seven generations by Y?q?t) which had settled in K?fa. He is first heard of in connection with the building of Baghdad in the latter half of 762, when he was associated with the other astrologers—Nawbakht, M?sh??all?h and ?Umar ibn al-Farrukh?n al-?abar?—who were involved in that work. He apparently remained at the Abbasid court; for, when an embassy arrived from Sind which included an Indian astronomer (whose identity is unknown, although it was certainly not Kanaka), the Caliph al-Man??r asked al-Faz?r? to work with this Indian on an Arabic translation of a Sanskrit astronomical text. The date of this embassy is variously given as 771 or 773. Another Arab astronomer who worked with this Indian was Ya?q?bibn ??riq.

The Sanskrit astronomical text that was translated with the assistance of al-Faz?r? was apparently entitled Mah?siddh?nta and belonged to what later became known as the Brahmapak?a (see essay IV on Indian astronomy in supplement); its most immediate cognates were the Pait?mahasiddh?nta of the Vi??udharmottarapur??a and the Br?hmasphu?asiddh?ntaof Brahmagupta; but the Indian astronomer evidently also conveyed to his Arab collaborators information about the ?ryabha??ya of ?ryabhata I. The Arabic translation of this Sanskrit text was entitled Z?j al-Sindhind; from it descends a long tradition within Islamic astronomy, which survived in the East until the early tenth century and in Spain until the twelfth. The first derivative work was evidently the Z?j al-Sindhind al-kab?r of al-Faz?r? himself.

Already in this work the elements of the Brahmapaksa begin to be contaminated with those of other schools. Although the system of the kalpa and the mean motions of the planets, their apogees, and their nodes remain within the tradition of the Z?j al-Sindhind, the maximum equations are derived primarily from the Z?j al-Sh?h, which represents the ?rdhar?trika school in Indian astronomy (see essay VI), and also from the ?ryabha??ya; the geographical section of the work also reveals the influence of the ?ryabha??ya and of a Sassanian tradition ascribed to Hermes. Moreover, al-Faz?r? allows great inconsistencies in this z?j, as he extracted convenient rules from one source or another without trying to make them coincide. Thus, he displays three values of R—3, 438 (from the ?ryabha??ya), 3,270 (from the Z?j al-Sindhind), and 150 (from the Z?j al-Sh?h)—and two values of the maximum equation of the sun—2; 11, 15 ° and 2;14° (from the Z?j al-Sh?n).

After writing this z?j al-Faz?r? composed another, probably about 790, called the Z?j ?al? sin? al-?Arab (“Astronomical Tables According to the Years of the Arabs”). In this z?j he apparently tabulated the mean motions of the planets for one to sixty saura days, 1,0 to 6,0 saura days (6,0 saura days being equal to one sidereal year), one to sixty sidereal years, and an unknown number of sixty-year periods; and he evidently added tables for converting kalpa aharga?as into Hegira dates. Of this latter set of tables we still have copies of the Mujarrad table for finding the day of the week with which each Arab year and month begins. Moreover, we have al-Faz?r?’s list of the countries of the world and their dimensions from this z?j; the dimensions presuppose a much larger earth than that allowed by the circumference of the earth which he introduced into his Z?j al-Sindhind al-kab?r from the ?ryabha??ya.

Very little else is known of al-Faz?r?’s works. A few lines of his Qa??da f? ?ilm al-nuj?m (“Poem on the Science of the Stars”) are preserved by Y?q?t and al-?afad?, and the bibliographers record books on the use of the plane astrolabe (al-Faz?r? is said to have been the first in Islam to construct one) and the armillary sphere, and on the measurement of noon. But we do have enough of his z?jes to know that his work was almost entirely derivative and that he could not even combine his disparate sources into a unified system. His significance lies entirely in that he helped to introduce a large body of Indian astronomical parameters and computational techniques to Islamic scientists.

BIBLIOGRAPHY

The numerous references to al-Faz?r? are collected and discussed in D. Pingree, “The Fragments of the Works of al-Faz?r?,” in Journal of Near Eastern Studies, 29 (1970), 103–123.

David Pingree