Al-Fazārī, Muḥammad Ibn Ibrāhīm
(fl. second half of the eighth century)
Al-Fazārī came from an old Arab family (his genealogy is traced back twenty-seven generations by Yāqūt) which had settled in Kūfa. 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, Māshāʾallāh and ʿUmar ibn al-Farrukhān al-Ṭabarī—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-Manṣūr asked al-Fazārī 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 Yaʿqūbibn Ṭāriq.
The Sanskrit astronomical text that was translated with the assistance of al-Fazārī was apparently entitled Mahāsiddhānta and belonged to what later became known as the Brahmapakṣa (see essay IV on Indian astronomy in supplement); its most immediate cognates were the Paitāmahasiddhānta of the Viṣṇudharmottarapurāṇa and the Brāhmasphuṭasiddhāntaof Brahmagupta; but the Indian astronomer evidently also conveyed to his Arab collaborators information about the Āryabhaṭīya of Āryabhata I. The Arabic translation of this Sanskrit text was entitled Zīj 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 Zīj al-Sindhind al-kabīr of al-Fazārī 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 Zīj al-Sindhind, the maximum equations are derived primarily from the Zīj al-Shāh, which represents the ārdharātrika school in Indian astronomy (see essay VI), and also from the Āryabhaṭīya; the geographical section of the work also reveals the influence of the Āryabhaṭīya and of a Sassanian tradition ascribed to Hermes. Moreover, al-Fazārī allows great inconsistencies in this zīj, 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 Āryabhaṭīya), 3,270 (from the Zīj al-Sindhind), and 150 (from the Zīj al-Shāh)—and two values of the maximum equation of the sun—2; 11, 15 ° and 2;14° (from the Zīj al-Shān).
After writing this zīj al-Fazārī composed another, probably about 790, called the Zīj ʿalā sinī al-ʿArab (“Astronomical Tables According to the Years of the Arabs”). In this zīj 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 ahargaṇas 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-Fazārī’s list of the countries of the world and their dimensions from this zīj; the dimensions presuppose a much larger earth than that allowed by the circumference of the earth which he introduced into his Zīj al-Sindhind al-kabīr from the Āryabhaṭīya.
Very little else is known of al-Fazārī’s works. A few lines of his Qaṣīda fī ʿilm al-nujūm (“Poem on the Science of the Stars”) are preserved by Yāqūt and al-Ṣafadī, and the bibliographers record books on the use of the plane astrolabe (al-Fazārī 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 zījes 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.
The numerous references to al-Fazārī are collected and discussed in D. Pingree, “The Fragments of the Works of al-Fazārī,” in Journal of Near Eastern Studies, 29 (1970), 103–123.