Zhang Heng (78–139 AD), a native of Xi’e, Nanyang (in present-day Henan Province), was an astronomer, mathematician, inventor, and an accomplished scholar. He began his career as an official during the Eastern Han dynasty (25–220). Controversy about his views and political rivalry with other officials led him to retire and return to Nanyang, but in 138 he was recalled to serve in the capital. He died a year later. He received posthumous honors for his scholarship and creativity. Two of his representative works are Hun yi (Armillary sphere) and Ling xian (The spiritual constitution of the universe). Zhang Heng adhered to the ancient cosmic Huntian theory of the celestial sphere, on which Chinese astronomers relied. He believed that the universe is round, that the Earth is square and motionless, and that the stars, the sun, and the moon circled in the universe. The National Central Library has copies of two different editions of this work. This is a revised copy, in one juan, with supplements, dated 1883 and printed in Changsha at the workshop of Langxuanguan (Library of the Celestial Emperor). The library’s other edition is dated 1884. Both are included in the catalog of the private library of Qing scholar Ma Guohan (born 1794), entitled Yu han shan fang ji yi shu (Catalog of missing books in the collection of Yuhan Shanfang). In 117, Zhang Heng created the world’s first water-powered armillary sphere. The celestial globe was connected to a timing clepsydra, from which water dropped to make the globe turn on a regular basis. It made a circuit in one day, so people watching the globe indoors would be able to locate celestial bodies at different times. The armillary sphere had both an outside and an inside sphere that rotated. On the surface were carved the South Pole, the North Pole, the equator, the ecliptic, the 24 solar terms, the sun, the moon, and certain stars. The sphere was moved to one of the imperial halls during the reign of Emperor Wu of Liang (464–546) of the Southern Dynasties. Zhang Heng also invented the world's first seismometer, called Hou feng di dong yi (Instrument for measuring the seasonal winds and the movements of the Earth), which could discern the direction of an earthquake some 500 kilometers away. In his extensive star catalogue, Zhang Heng documented approximately 2,500 stars. He also posited theories about the moon and its relationship to the sun and the nature of solar and lunar eclipses. Although he thought that the heavens had a hard external shell, he believed that the cosmos outside the shell was infinite in space and time.
Langxuanguan, Changsha, China
Title in Original Language
Type of Item
- Included in the collection Yu han shan fang ji yi shu (Catalog of missing books in the collection of Yuhan Shanfang)
- Only preface and partial text are included in the WDL presentation.
Last updated: January 3, 2018