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As in the other
sciences, astronomers in the Muslim lands built upon and greatly expanded
earlier traditions. At the House of Knowledge founded in Baghdad by the
Abbasid caliph Mamun, scientists translated many texts from Sanskrit,
Pahlavi or Old Persian, Greek and Syriac into Arabic, notably the great
Sanskrit astronomical tables and Ptolemy's astronomical treatise, the
Almagest. Muslim astronomers accepted the geometrical structure
of the universe expounded by Ptolemy, in which the earth rests motionless
near the center of a series of eight spheres, which encompass it, but
then faced the problem of reconciling the theoretical model with Aristotelian
physics and physical realities derived from observation.
Some of the most
impressive efforts to modify Ptolemaic theory were made at the observatory
founded by Nasir al-Din Tusi in 1257 at Maragha in northwestern Iran and
continued by his successors at Tabriz and Damascus. With the assistance
of Chinese colleagues, Muslim astronomers worked out planetary models
that depended solely on combinations of uniform circular motions. The
astronomical tables compiled at Maragha served as a model for later Muslim
astronomical efforts. The most famous imitator was the observatory founded
in 1420 by the Timurid prince Ulughbeg at Samarkand in Central Asia, where
the astronomer Ghiyath al-Din Jamshid al-Kashi worked out his own set
of astronomical tables, with sections on diverse computations and eras,
the knowledge of time, the course of the stars, and the position of the
fixed stars. Essentially Ptolemaic, these tables have improved parameters
and structure as well as additional material on the Chinese Uighur-calendar.
They were widely admired and translated even as far away as England, where
John Greaves, professor at Oxford, called attention to them in 1665.
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