Zu Chongzhi

Zu Chongzhi

(born 429, Jiankang, China—died 500, China) Chinese astronomer, mathematician, and engineer. About 462 he proposed a new calendar system that would provide a more precise number of lunations per year and take into consideration the precession of the equinoxes. His Daming calendar was finally adopted in 510 through the efforts of his son, Zu Gengzhi. Li Chunfeng called Zu Chongzhi the best mathematician ever and gave him credit for three approximations of π: ²²⁄₇, ³⁵⁵⁄₁₁₃, and the interval 3.1415926 < π < 3.1415927; the third result remained the best in the world until improved by the Arab mathematician al-Kashi (fl. c. 1400). He also worked on the mathematical theory of music and metrology, and he constructed several devices, such as a semilegendary “south-pointing carriage.” The carriage was topped by a symbolic figure that, once properly aligned, would always point to the south.