Zu Chongzhi (Chinese:祖沖之; 429 – 500[1]),courtesy nameWenyuan (Chinese:文遠), was a Chinese astronomer, inventor, mathematician, politician, and writer during theLiu Song andSouthern Qi dynasties. He was most notable for calculatingpi as between 3.1415926 and 3.1415927, a record in precision which would not be surpassed for nearly 900 years.
| Zu Chongzhi | |||||||||
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| Traditional Chinese | 祖沖之 | ||||||||
| Simplified Chinese | 祖冲之 | ||||||||
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| Wenyuan(courtesy name) | |||||||||
| Traditional Chinese | 文遠 | ||||||||
| Simplified Chinese | 文远 | ||||||||
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Chongzhi's ancestry was from modernBaoding, Hebei.[2] To flee from the ravages of war, Zu's grandfather Zu Chang moved to theYangtze, as part of the massive population movement during theEastern Jin. Zu Chang (祖昌) at one point held the position of Chief Minister for the Palace Buildings (大匠卿) within the Liu Song[3] and was in charge of government construction projects. Zu's father, Zu Shuozhi (祖朔之), also served the court and was greatly respected for his erudition.
Zu was born inJiankang. His family had historically been involved in astronomical research, and from childhood Zu was exposed to both astronomy and mathematics. When he was only a youth, his talent earned him much repute.[4] WhenEmperor Xiaowu of Song heard of him, he was sent to the Hualin Xuesheng (華林學省) academy, and later the Imperial Nanjing University (Zongmingguan) to perform research. In 461 in Nanxu (todayZhenjiang, Jiangsu), he was engaged in work at the office of the local governor. In 464, Zu moved to Louxian (today Songjiang district, Shanghai), there, he compiled the Daming calendar and calculated π.
Zu Chongzhi, along with his sonZu Gengzhi, wrote a mathematical text entitledZhui Shu (綴述; "Methods for Interpolation"). It is said that the treatise contained formulas for the volume of a sphere, cubic equations and an accurate value ofpi.[5] This book has been lost since theSong dynasty.
His mathematical achievements included
Zu was an accomplished astronomer who calculated the time values with unprecedented precision. His methods of interpolation and the use of integration were far ahead of his time. Even the results of the astronomerYi 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 theDa Ming Li.[clarification needed] It is said that his methods of calculation were so advanced, the scholars of the Sung dynasty and Indo influence astronomers of the Tang dynasty found it confusing.
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The majority of Zu's great mathematical works are recorded in his lost text theZhui Shu. Most schools argue about his complexity since traditionally the Chinese had developed mathematics as algebraic and equational. Logically, scholars assume that theZhui Shu yields methods of cubic equations. His works on the accurate value of pi describe the lengthy calculations involved. Zu usedLiu Hui'sπ algorithm described earlier byLiu Hui to inscribe a 12,288-gon. Zu's value of pi is precise to six decimal places and for almost nine hundred years thereafter no subsequent mathematician computed a value this precise.[9] Zu also worked on deducing the formula for the volume of a sphere with his son Zu Gengzhi. In their calculation, Zu used the concept that two solids with equal cross-sectional areas at equal heights must also have equal volumes to find the volume of a Steinmetz solid. And further multiplied the volume of the Steinmetz solid with π/4, therefore found the volume of a sphere as πd^3/6 (d is the diameter of the sphere).
In 488, Zu Chongzhi was responsible for erecting water powered triphammer mills which was inspected byEmperor Wu of Southern Qi during the early 490s.[10][11][12]
Zu is also credited with inventing Chinese paddle boats orQianli chuan in the late 5th century AD during the Southern Qi dynasty.[13][14][15][12] The boats made sailing a more reliable form of transportation and based on the shipbuilding technology of its day, numerous paddle wheel ships were constructed during the Tang era as the boats were able to cruise at faster speeds than the existing vessels at the time as well as being able to cover hundreds of kilometers of distance without the aid of wind.[13]
Thesouth-pointing chariot device was first invented by the Chinese mechanical engineerMa Jun (c. 200–265 AD). It was a wheeled vehicle that incorporated an early use ofdifferential gears to operate a fixed figurine that would constantly point south, hence enabling one to accurately measure their directional bearings. This effect was achieved not bymagnetics (like in acompass), but through intricate mechanics, the same design that allows equal amounts of torque applied to wheels rotating at different speeds for the modernautomobile. After theThree Kingdoms period, the device fell out of use temporarily. However, it was Zu Chongzhi who successfully re-invented it in 478, as described in the texts of theBook of Song and theBook of Qi, with a passage from the latter below:
WhenEmperor Wu of Liu Song subduedGuanzhong he obtained the south-pointing carriage of Yao Xing, but it was only the shell with no machinery inside. Whenever it moved it had to have a man inside to turn (the figure). In the Sheng-Ming reign period, Gao Di commissioned Zi Zu Chongzhi to reconstruct it according to the ancient rules. He accordingly made new machinery of bronze, which would turn round about without a hitch and indicate the direction with uniformity. Since Ma Jun's time such a thing had not been.[16][17]
Zu'sparadoxographical workAccounts of Strange Things [述異記] survives.[18][19]
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