Zu Chongzhi  Zu Chongzhi (; 429–500 AD), courtesy name Wenyuan (), was a Chinese astronomer, mathematician, politician, inventor, and writer during the Liu Song and Southern Qi dynasties. He was most notable for calculating pi as between 3.1415926 and 3.1415927, a record which would not be surpassed for 800 years. Chongzhi's ancestry was from modern Baoding, Hebei. To flee from the ravage of war, Zu's grandfather Zu Chang moved to the Yangtze, as part of the massive population movement during the Eastern Jin. Zu Chang () at one point held the position of Chief Minister for the Palace Buildings () within the Liu Song and was in charge of government construction projects. Zu's father, Zu Shuozhi () also served the court and was greatly respected for his erudition. Zu was born in Jiankang. His family had historically been involved in astronomy research, and from childhood Zu was exposed to both astronomy and mathematics. When he was only a youth his talent earned him much repute. When Emperor Xiaowu of Liu Song heard of him, he was sent to an Academy, the Hualin Xuesheng (), and later at the Imperial Nanjing University (Zongmingguan) to perform research. In 461 in Nanxu (today Zhenjiang, Jiangsu), he was engaged in work at the office of the local governor. Zu Chongzhi, along with his son Zu Gengzhi wrote a mathematical text entitled "Zhui Shu" (; ""Methods for Interpolation""). It is said that the treatise contains formulas for the volume of the sphere, cubic equations and an accurate value of pi. This book has not survived, but has been lost since the Song Dynasty. His mathematical achievements included:  In Chinese literature, this fraction is known as "Zu's ratio". Zu's ratio is a best rational approximation to , and is the closest rational approximation to from all fractions with denominator less than 16600. Zu was an accomplished astronomer who calculated the time values with unprecedented precision. His methods of interpolationg and the use of integration were far ahead of his time. Even the results of the astronomer Yi Xing (who was beginning to utilize foreign knowledge) were not comparable. The Sung dynasty calendar was backwards to the "Northern barbarians" because they were implementing their daily lives with the "Da Ming Li".