1201-1274

Arab astronomer and mathematician who established an observatory at Maragheh (now in Azerbaijan) under the patronage of the Mongol conqueror Hulagu Khan. Al-Tusi designed a number of instruments for the observatory, which became a center of scientific learning in Muslim Central Asia. There al-Tusi prepared the Ilkhanic Tables, which contained 12 years worth of astronomical observations. He also developed new hypotheses on the movement of planets, ideas some scholars consider the most important contributions to the understanding of cosmology between the time of Ptolemy (second century A.D.) and that of Nicolaus Copernicus (1473-1543).