Shen Kuo

Shen Kuo was a Chinese scholar-official of the Northern Song dynasty whose interests ranged from astronomy and mathematics to geology, medicine and engineering. He served the court as astronomer, finance commissioner, diplomat and military commander before falling from favour. In retirement he wrote the Dream Pool Essays of 1088, which contain the earliest known description of the magnetic needle compass and much of what is known about early Chinese science and technology.

Shen Kuo was born in 1031 in Qiantang, the modern city of Hangzhou. His father held provincial posts, and his mother, a well-educated woman from Suzhou, gave him his early schooling. From about 1040 the family moved from post to post, including in Sichuan, and the boy took a lively interest in the landscapes he passed through.

After his father's death around 1051 he spent three years in mourning, then from 1054 served in minor local offices. An early success was a drainage and embankment scheme that turned a large area of swampland into farmland.

In 1063 Shen passed the imperial examinations with distinction. Recommended to the central government, he became a favourite of the chancellor Wang Anshi, leader of the reforming faction behind the New Policies. In 1072 he was made head of the Bureau of Astronomy and supervised the dredging of the Bian Canal near the capital. He later became finance commissioner and head of the Hanlin Academy.

In 1075 he went as envoy to the Khitan Liao dynasty, which was pressing territorial claims, and used archived records of earlier negotiations to rebut the Liao emperor's demands. In 1080 he was given military command at Yanzhou, modern Yan'an, against the Tanguts of the Western Xia, and in 1081 captured several of their fortified towns. But another commander ignored his advice, and the defeat that followed, which one historian puts at 60,000 dead, was blamed on Shen. He was dismissed and spent six years under restricted residence.

Freed from public duties, Shen turned to writing. He had bought a garden estate near modern Zhenjiang, which he named Dream Brook, and moved there in 1088, the year he finished the Dream Pool Essays. Its 507 or so short entries range across nature, technology and court life.

Its most famous passage describes a needle magnetised by rubbing with lodestone and suspended to show direction, and notes that it points not exactly south but slightly east, the first known recognition of magnetic declination. Elsewhere Shen preserved the only account of Bi Sheng, the commoner who invented movable type made of baked clay in the 1040s, and described the new pound locks on canals and an early drydock.

He also reasoned about the earth itself. Seeing bands of fossil shells in cliffs of the Taihang Mountains in 1074, he concluded that the area had once been a seashore and that land is built up over vast periods by erosion and the deposit of silt. Petrified bamboo found underground near Yanzhou, where bamboo no longer grew, led him to suggest that the climate had changed over time.

At the Bureau of Astronomy Shen improved the gnomon, armillary sphere and water clock, and by tracking the pole star for three months showed that it had shifted from its traditional position. Like Zhang Heng a thousand years earlier, he explained that the Moon is a sphere lit by the Sun. With his colleague Wei Pu he began a five-year programme of nightly observations of the Moon and planets, but opponents at court blocked most of the resulting corrections.

Shen died at Dream Brook in 1095 and was buried at Hangzhou; his tomb was rediscovered in 1983. Traditional historians criticised his part in the New Policies, but the historian Joseph Needham called him among the greatest scientific minds in China's history, while others note that he never organised his observations into general theories.

Shen Kuo served the Song dynasty at a time when it shared China with the Liao and Western Xia. Our 1000 and 1100 maps show this division of the Chinese world before and after his career.