Zhang Heng

Zhang Heng was born in China in 78 ce. He left home to study literature and found his gift for writing poetry. At the age of 30, he became interested in astronomy and was later appointed the CHIEF ASTRONOMER at the Han emperor’s court. He observed the stars, mapped the planets, and tracked lunar eclipses. His cosmic contribution included a catalogue of 2,500 stars and more than 100 constellations.

Heng recognized that the Moon’s shiny surface was the reflection of sunlight.

The Chinese poet whose far-flung INVENTIONS reached for the stars

Disaster warning

Concerned by earthquakes in China, Heng designed the FIRST SEISMOMETER in 132 ce. His machine could detect movements 640 km (400 miles) away. Heng also studied sets of numbers called magic squares, placed the first mathematical grid system over a map, and invented a device called an odometer to record the distance travelled by a wheeled cart.

During an earthquake, a ball from a dragon’s head falls into the mouth of a frog to reveal the earthquake’s direction.

The astronomical and mathematical innovations of Zhang Heng transformed ancient Chinese science. the wor ld How he changed…