Zhang Heng 张衡

A scientist who specializes in astronomy and geosciences


Chinese Name: 张衡

English Name: Zhang Heng

Other Names: Zhang Pingzi 张平子

Born: 78

Died: 139


The pioneer in the study of astronomy and geography in China 开创中国天文、地理研究之先河

Invent seismograph 发明地动仪

One of the four masters of Han Fu 汉赋四大家之一

Main Works:

Lingxian 灵宪

Zhang Hejian Ji 张河间集

Gui Tian Fu 归田赋

Er Jing Fu 二京赋

Zhang Heng 张衡
Zhang Heng 张衡

Brief Biography of Zhang Heng

Zhang Heng was an outstanding astronomer, mathematician, inventor, geographer and writer in the Eastern Han Dynasty.

Zhang Heng (78-139 years), courtesy name Pingzi 平子, was born in Xi’e County 西鄂县, Nanyang Prefecture 南阳郡 (now Shiqiao Town 石桥镇, Nanyang City 南阳市, Henan Province 河南省). In the Eastern Han Dynasty, he successively served as a doctor, imperial official, servant, and Hejian. In his later years, he joined the imperial court as minister due to illness and died in the fourth year of Yonghe 永和 (139) at the age of 62. In the Northern Song Dynasty 北宋, he was granted the title of Xi’ebo 西鄂伯.

Zhang Heng 张衡
Zhang Heng Museum 张衡博物馆

Zhang Heng has written Lingxian 灵宪 and Hunyi Tuzhu 浑仪图 in astronomy; Mathematical works include Suanwang Theory 算罔论; The literary works are represented by Er Jing Fu 二京赋 , Gui Tian Fu 归田赋, etc., and he was called “Four Great Poets of Han Fu” together with Sima Xiangru 司马相如, Yang Xiong 扬雄 and Ban Gu 班固. There are 14 volumes of Zhang Heng Collection 张衡集 in Sui Shu·Jing Ji Zhi 隋书·经籍志, which have been lost for a long time. Zhang Pu 张溥 of the Ming Dynasty 明朝 compiled Zhang Hejian Collection 张河间集.

Zhang Heng made outstanding contributions to the development of astronomy, mechanical technology and seismology in China. He invented the seismometer and improved the armillary sphere. He was one of the representatives of the theory of armillary sphere in the middle of the Eastern Han Dynasty. He is known as the “Wooden Sage 木圣” by later generations.

Because of his outstanding contributions, the International Astronomical Union named a circular mountain on the back of the moon “Zhang Heng Circular Mountain”, and the 1802 asteroid in the solar system “Zhang Heng Star”. In memory of Zhang Heng, later generations built the Zhang Heng Museum in Nanyang 南阳.

Personal Life and Major Contributions

Step into an official career

During the reign of Emperor Yongyuan of the Han Dynasty 汉 (89-105), Zhang Heng was elected to be a filial and honest man, but he did not accept the recruit of government several times. At that time, the country was in peace for a long time, and there was no one who was not extravagant below the princes.

He then imitated Ban Gu’s “Liangdu Fu 两都赋”, and after ten years of exhausted thinking, he wrote the “Erjing Fu” to satirize the imperial court. Deng Zhi 邓骘, the great general, appreciated his talent. He was recruited many times, but Zhang Heng didn’t answer his orders.

Zhang Heng 张衡
The statue of Zhang Heng 张衡塑像

In AD 100 (the 12th year of the Yongyuan era), Zhang Heng, at the request of Nanyang Prefecture Magistrate Bao De 鲍德, was in charge of his clerical work. Eight years later, Bao De was transferred to the capital, and he resigned from office and stayed at home.

Be a foreign minister

In 133 AD (the second year of Yangjia 阳嘉 era), he was promoted to the rank of servant, and Emperor Shun 顺帝 appointed him to give advice on the state’s political affairs. Emperor Shun once asked him who the world hated. The eunuchs were afraid that he would speak ill of them, so they stared at him with their eyes. He answered with some unpredictable words and came out. However, eunuchs were worried that Zhang Heng would become their scourge in the future, so they gathered together to slander him.

Zhang Heng often thought about how to act. He thought that bad luck were dark and difficult to understand, so he wrote Sixuan Fu 思玄赋 to express and repose his feelings.

Zhang Heng 张衡
Seismograph 地动仪

In 136 AD (the first year of Yonghe), he was transferred as the minister of Liu Zheng 刘政, the king of Hejian. Liu Zheng is extravagant and dissolute, and does not obey laws and disciplines; There are also many powerful people who gather together to make trouble. After Zhang Heng came to office, he tightened the law and discipline, cracked down on the powerful and secretly discovered the name of the traitor party. He was famous for his clean government. After three years in office, he applied for resignation and returned home, and was called up as a minister.

The inventions of Zhang Heng


In 132 AD (the first year of Yangjia era), Zhang Heng invented the earliest seismograph, called the Hou Feng Seismograph 候风地动仪, during his tenure as the imperial historian. Earthquakes are frequent in the world, but it is after the 19th century that we can really use instruments to observe earthquakes abroad. Houfeng seismograph is the ancestor of seismographs in the world. Although its function is still limited to measuring the approximate location of the epicenter, it has surpassed the development of world science and technology for about 1800 years.

Zhang Heng 张衡
Armillary sphere浑天仪

Armillary sphere

On the basis of the armillary sphere invented by Geng Shouchang 耿寿昌 in the Western Han Dynasty, he created a more accurate and comprehensive “armillary sphere” than ever before according to his own theory of armillary sphere.

Video: Zhang Heng was a Chinese mathematician, astronomer and geographer

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