The Persian polymath who built the great Maragha observatory, reformed planetary astronomy with the "Tusi couple," and wrote across mathematics, ethics, and theology.
Life
Nasir al-Din al-Tusi (1201–1274) survived the Mongol conquests to serve Hulagu Khan, persuading him to found the Maragha observatory, which he directed. His mathematical device, the "Tusi couple," improved on Ptolemaic models and later echoed in Copernican astronomy. He also wrote the influential Akhlaq-i Nasiri on ethics and advanced trigonometry as an independent discipline, ranking among the greatest scientists of the medieval world.