Zhang Heng

Zhang Heng (AD 78 – 139) was a Chinese scientist and government leader who lived during the Eastern Han dynasty. He was known for his skills in astronomy, math, and inventing new things. Zhang Heng began his work as a small officer but later became an important astronomer and advisor.

He made several important inventions. Zhang created the world's first water-powered armillary sphere to watch the stars. He also invented the first seismoscope, a tool that could sense earthquakes from far away. In addition to his inventions, Zhang improved math calculations for numbers like pi and wrote about the Moon and the Sun.

Zhang's poems and writings were very well-known in his time. He was honored after his death for his clever ideas and inventions. Some modern experts compare his astronomy work to that of the Greco-Roman scientist Ptolemy.

Life

Further information: History of the Han dynasty

Zhang Heng was born in a town called Xi'e in Nanyang Commandery, north of modern Nanyang City in Henan. His family was respected but not very wealthy. His grandfather helped lead the country after Wang Mang was in charge.

When Zhang was young, he studied in the cities of Chang'an and Luoyang. He became good at writing and made many friends. At 23, he went home and worked for the local government. At 30, he started studying astronomy and writing about it.

Zhang later worked in the court of Emperor An. He became the Chief Astronomer and kept track of the stars to help make the calendar. He also tested young people who wanted government jobs. Zhang also had other important jobs, like receiving messages for the emperor.

Zhang invented a machine that could detect earthquakes from far away. One day, the machine showed an earthquake had happened, but no one in the capital felt it. Later, a message arrived saying an earthquake had occurred far to the northwest.

Zhang also wrote about problems in the government and shared his thoughts and feelings in his writing.

Literature and poetry

Further information: Chinese literature and Society and culture of the Han dynasty

Zhang Heng liked to write and could read many books in the capital. He wrote poems and stories that showed his knowledge of old books and ideas. His poems often described cities, nature, and everyday life.

He wrote famous poems like "Western Metropolis Rhapsody" and "Eastern Metropolis Rhapsody." These poems described life in big cities. In another poem, "Four Sorrows," he wrote about feeling far from someone important to him. Zhang’s writings also talked about city layouts and different people’s customs. This showed his interest in learning about the world.

Achievements in science and technology

Zhang Heng made important contributions to science and technology.

In mathematics, he worked on calculating the value of pi.

In astronomy, Zhang developed ideas about the universe and stars. He made detailed star maps and explained events like solar and lunar eclipses.

Zhang also invented useful devices. He designed a water-powered armillary sphere, an early version of a seismoscope to detect earthquakes, and helped develop tools like the odometer and a south-pointing chariot. These inventions showed his skill in using science to solve problems.

Legacy

Zhang Heng’s inventions inspired many later inventors in China. For example, Su Song used Zhang’s water-powered armillary sphere for his clock tower in the 11th century. People admired Zhang for his clever designs and many talents.

Zhang was also a well-known poet. Even after his death, people honored him for his achievements. Today, several things are named after him, like a lunar crater and a mineral. In 2018, China launched a satellite named Zhangheng-1 in his honor.

Main article: Zhang Heng