Su Song

Su Song (Chinese: 蘇頌; Pe̍h-ōe-jī: So͘ Siōng, 1020–1101), courtesy name Zirong (Chinese: 子容; Pe̍h-ōe-jī: Chú-iông), was a Chinese polymathic scientist and statesman who lived during the Song dynasty (960–1279). He excelled in numerous fields including but not limited to mathematics, astronomy, cartography, geography, metallurgy, mechanical engineering, hydraulic engineering, poetry, and statesmanship.

Su Song was the engineer for a hydro-mechanical astronomical clock tower located in Kaifeng. It employed an early escapement mechanism. The escapement mechanism of Su's clock tower was invented by the Tang dynasty Buddhist monk Yi Xing and government official Liang Lingzan in 725 AD to operate a water-powered armillary sphere, however Su's armillary sphere was the first to utilize a mechanical clock drive. Su's clock tower also featured the oldest known endless power-transmitting chain drive, called the tian ti (天梯), or "celestial ladder", as depicted in his horological treatise. The clock tower had 133 different clock jacks to indicate and sound the hours. The clock was dismantled by the invading Jurchen army in 1127 AD, and although attempts were made to reassemble it, the tower was never successfully reinstated.

Su Song's treatise about the clock tower, Xinyi Xiangfayao (新儀象法要), was written in 1092 and received its official printed publication in 1094. The Xinyi Xiangfayao was Su's best-known treatise, but the polymath compiled other works as well. He completed a large celestial atlas of several star maps, several terrestrial maps, as well as a treatise on pharmacology. The latter discussed related subjects on mineralogy, zoology, botany, and metallurgy.

Su Song was of Hokkien ancestry who was born in modern-day Fujian, near medieval Quanzhou. Like his contemporary, Shen Kuo (1031–1095), Su Song was a polymath, a person whose expertise spans a significant number of different fields of study. It was written by his junior colleague and Hanlin scholar Ye Mengde (1077–1148) that in Su's youth, he mastered the provincial exams and rose to the top of the examination list for writing the best article on general principles and structure of the Chinese calendar. From an early age, his interests in astronomy and calendrical science led him onto a distinguished path as a state bureaucrat. In his spare time, he was fond of writing poetry, which he used to praise the works of artists such as the painter Li Gonglin (1049–1106). He was also an antiquarian and collector of old artworks from previous dynasties.

In matters of administrative government, he had attained the rank of Ambassador and President of the Ministry of Personnel at the capital of Kaifeng, and was known also as an expert in administration and finance. After serving in the Ministry of Personnel, he became a Minister of Justice in 1086. He was appointed as a distinguished editor for the Academy of Scholarly Worthies, where in 1063 he edited, redacted, commented on, and added a preface for the classic work Huainanzi of the Han dynasty (202 BC–220 AD). Eventually, Su rose to the post of Vice President of the Chancellery Secretariat. Among many honorable positions and titles conferred upon him, Su Song was also one of the 'Deputy Tutors of the Heir Apparent'. At court, he chose to distance himself from the political rivalries of the Conservatives, led by Prime Minister Sima Guang (1019–1086), and the Reformists, led by Prime Minister Wang Anshi (1021–1086); although many of his associates were of the Conservative faction.

In 1077, he was dispatched on a diplomatic mission to the Liao dynasty of the Khitan people to the north, sharing ideas about calendrical science, as the Liao state had created its own calendar in 994 AD. In a finding that reportedly embarrassed the court, Su Song acknowledged to the emperor that the calendar of the Khitan people was in fact a bit more accurate than their own, resulting in the fining and punishment of officials in the Bureau of Astronomy and Calendar. Su was supposed to travel north to Liao and arrive promptly for a birthday celebration and feast on a day which coincided with the winter solstice of the Song calendar, but was actually a day behind the Liao calendar. Historian Liu Heping states that Emperor Zhezong of Song sponsored Su Song's clocktower in 1086 in order to compete with the Liao for "scientific and national superiority." In 1081, the court instructed Su Song to compile into a book the diplomatic history of Song-Liao relations, an elaborate task that, once complete, filled 200 volumes. With his extensive knowledge of cartography, Su Song was able to settle a heated border dispute between the Song and Liao dynasties.

Su Song also created a celestial atlas (in five separate maps), which had the hour circles between the xiu (lunar mansions) forming the astronomical meridians, with stars marked in an equidistant cylindrical projection on each side of the equator, and thus, was in accordance to their north polar distances. Furthermore, Su Song must have taken advantage of the astronomical findings of his political rival and contemporary astronomer Shen Kuo. Su Song's fourth star map places the position of the pole star halfway between Tian shu (−350 degrees) and the current Polaris; this was the more accurate calculation (by 3 degrees) that Shen Kuo had made when he observed the pole star over a period of three months with his width-improved sighting tube. There were many star maps written before Song's book, but the star maps published by Su represent the oldest extant star maps in printed form.

In 1070, Su Song and a team of scholars compiled and edited the Bencao Tujing ('Illustrated Pharmacopoeia', original source material from 1058 to 1061), which was a groundbreaking treatise on pharmaceutical botany, zoology, and mineralogy. In compiling information for pharmaceutical knowledge, Su Song worked with such notable scholars as Zhang Yuxi, Lin Yi, Zhang Dong, and many others.