Academic journal article Transactions of the American Philosophical Society

Indian Astronomy in Medieval Spain

Academic journal article Transactions of the American Philosophical Society

Indian Astronomy in Medieval Spain

Article excerpt

Indian astronomy entered early Islam through several routes1. The ûrdharûtrikapaksa that had been initiated by Äryabhata of Kusumapura in about 500 influenced the Zlk-i Shûhriyûrûn composed in PahlavT at the Sasanian court in Ctesiphon under Khusrö Anüshirwän in 556. This is known to us now through the astrological computations made by Mäshä'alläh ibn AtharT, a Persian Jew from Basra, for the several astrological histories that he wrote in the decades before and after 800:. From the works of Mäshä'alläh extant in Arabic, Greek, and Latin, and from the discussions of them by al-Häshiml in his Kitûb cilal al-zfjût and by al-Blrünï in his Kitûb tamhfd al-mustaqirr li-macnû al-mamarry we know that Khusrö's zfk utilized the ûrdharûtrika's apogees of Saturn, Jupiter, and the Sun; and its equations of the center of Jupiter and, within one minute, Mars and the Sun. This Zfk-i Shûhriyûrûn already employed the Persian calendar, and was probably influenced by Ptolemy4.

The zfk of Khusrö strongly influenced that produced under the last of the Sasanian Shäh~i Shähs, Yazdijird III, which was translated into Arabic as the Zfj al-Shûh by al-Tamïmï in about 800. This also is now lost, but much concerning it may be learned from the Zfj al-mumtahan (Tabulae Probatae), the zfjts of Habash al-Häsib, and again, al-Häshimi and al-BTrüní5. While some modifications were made in the parameters - e.g., in Mars' equation of the center - the structure and calendar of Khusrö's ztk were retained, and the influence of Ptolemy may even have been expanded.

In the early eighth century the earliest Arabic zfjes were composed on the basis of Indian methods: the Zfj al-Jûmic and the Zfj al-Hazür at Qandahar, the Zfj ai-Arkand at Sind in 735 largely on the basis of the ûrdharûtrikapaksa as expounded in Brahmagupta's Khandakhûdyaka, and the Zfj al-Harqan on the basis of the ûryapaksa of Aryabhata's Âryabhatfya in 7426. None of these was wildly popular outside of Sind and Afghanistan; we know of them only through al-Häshiml and al-Bïrünï. More significant for the transmission of Indian astronomy to the Islamic world was the translation of a Sanskrit text, apparently entitled Mahûsiddhùnta, into Arabic at the court of al-Mansur in Baghdad in the early 770's7. Two of those involved in the popularization of this translation, the Zfj al-Sindhind, were Muhammad ibn Ibrâhîm al-Fazarl8, who, according to one story, was involved in the translation itself, and Ya'qub ibn Tariq9.

Al-Fazärl, in about 775, wrote on the basis of the Zfj al-Sindhind, the Zfj al-Shûh, and the Ptolemaic tradition (probably as represented by the Handy Tables in their Pahlavï version)10, a Zfj al-Sindhind al-kabfr. Basically, al-Fazârï's mean motions of the planets (including the Sun and the Moon), their nodes, and their apogees were derived from the brûhmapaksa through Brahmagupta's Brâhmasphutasiddhûnta, the equations of the center and of the anomaly from the Zfj al-Shûh, and the table of declinations of the Sun from the Handy Tables; other computations, involving three different values for the radius, R, in a sine-table - 150 from the KhandakhOdyaka, 3270 from the Brûhmasphutasiddhûnta, and 3438 from the Paitûmahasiddhanta and the Äryabhatfya - were derived from various Indian and Sasanian sources. Al-Fazârï in some instances - e.g.y in the mean motions of Saturn and of the lunar node, and in some of the equations - differs from his identifiable sources. Some of his tables, as had been Ptolemy's for Chords and declinations, were entered with arguments of 0;30°, while the equation tables imitated the Indian practice of intervals of 90724 or 3;45° (and its multiples 7;30° and 15°). Though the brûhmapaksa does not allow for precession, al-Fazârï used Ptolemy's value of Io per 100 years. It appears that al-Fazârï's Zfj al-Sindhind al-kabfr followed the Zfj al-Shäh in using the epoch of Yazdijird III (16 June 632) and the Persian calendar, though in about 788 he published a Zfj calû sintal-cArab which utilized the epoch of the Hijra (16 July 622) and the Muslim calendar. …

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