alTusi

Nasir al-Din al-Tusi (c. 1201–1274), commonly referred to simply as al-Tusi, was a Persian polymath whose work spanned astronomy, mathematics, philosophy, theology, and the natural sciences. He was born in Tous, near modern-day Tehran, Iran, and became a leading scholar at the Ilkhanid court of Hulagu Khan. Around 1259 he helped found the Maragha Observatory, directing a team of scholars who produced refined astronomical tables and models.

A key achievement attributed to al-Tusi is the Tusi couple, a geometric device in which a small circle rolling inside a larger circle generates linear motion, used to address planetary models without invoking the Ptolemaic equant. He also oversaw the compilation and refinement of the Zij-i Ilkhani, a major astronomical table work. His mathematical and philosophical writings drew on Avicenna and other Islamic thinkers and contributed to the medieval scientific program in the Muslim world.

Al-Tusi's influence extended beyond his lifetime, shaping Islamic astronomy and, through later translations and contacts, influencing European scholars and the development of astronomy in the Renaissance. He died in 1274; exact burial details are uncertain, with sources placing his death in the late 13th century in or near his homeland. He remains a central figure in the history of medieval science.