Zu Chongzhi
Native spelling: 祖沖之
429–501, Jiankang (present-day Nanjing), Liu Song dynasty, China (exact location unknown)
Chinese mathematician and astronomer who bounded pi between 3.1415926 and 3.1415927 using a polygon method with a 24576-sided figure, and devised the milü fraction 355/113 as an extremely accurate rational approximation.
Zu Chongzhi was born in 429 CE, during the Liu Song dynasty, in the region of present-day China, and died around 500 CE under the succeeding Southern Qi dynasty. He served at the imperial courts of both dynasties, working on mathematics, astronomy and mechanical engineering, including the design of a south-pointing chariot and other devices, and compiled the Daming calendar, which accounted for the precession of the equinoxes more accurately than earlier Chinese calendars.
Zu Chongzhi's best-known mathematical achievement extended Liu Hui's polygon method for computing pi. By working with an inscribed regular polygon of 24576 sides, he established that pi lies strictly between 3.1415926 and 3.1415927 — correct to seven significant decimal digits — a remarkable level of precision for his era. He also gave two convenient rational approximations: the coarser yuelü, 22/7, and the far more accurate milü, 355/113, which agrees with pi to six decimal places and was not rediscovered in Europe until Adriaan Anthonisz published it in 1585, more than a thousand years later.
Working with his son Zu Geng, Zu Chongzhi is also credited with refining the derivation of the volume of a sphere using dissection arguments related to those later formalized in the West as Cavalieri's principle. Much of his original mathematical writing, including a treatise known as the Zhui Shu, was lost; his results are known mainly through later citations and the official histories of the Southern and Northern Dynasties.
Workplaces: Liu Song and Southern Qi imperial courts, China
China