Zhang Heng

Zhang Heng (78-139), courtesy name Pingzi, was a native of Xi'e County, Nanyang County (now south of Nanzhao County, Nanyang City, Henan Province). He was a scholar-bureaucrat of the Eastern Han Dynasty, an astronomer, geographer, mathematician, scientist, inventor and writer. He held the rank of Taishi Ling, Shizhong and Shangshu. Zhang Heng made extraordinary achievements in his life. He made a water-driven armillary sphere, invented a seismometer and compass that can detect the direction of earthquake sources, discovered the causes of solar and lunar eclipses, drew a star map recording 2,500 stars, and calculated pi accurately. To one decimal place, he explained and established the cosmology of Hun Tian Theory; in terms of literature, he created poetry works such as "Er Jing Fu" and "Guitian Fu", which expanded the style and subject matter of Han Fu, and was listed as one of the "Four Masters of Han Fu". He created the poetic genre of seven-character ancient poetry and made great contributions to Chinese culture.