Ancient Chinese Astronomy: New insights from old information

China has the world’s longest-running observations of the sky: though based in astrology, they are of unique importance to astronomy today.

In 210 BC, the great First Emperor of China was buried near Xi’an with his famous Terracotta Army of full-sized clay warriors. According a contemporary account, his own tomb – yet to be excavated – was even more lavish, containing a fabulous double map: “Below was a map of the Earth. The hundred rivers of the Empire were modeled in mercury: cleverly designed machines made the rivers flow. Above everything was the starry vault.”

This map reflected the crucial role that the sky played in ancient Chinese thought. The heavens weren’t remote from everyday life. The sky was a mirror of the Earth.

Every time that something unexpected occurred in the sky, it showed a disruption on the Earth – which, in effect, meant somewhere in China. To pinpoint exactly where, the Chinese split the stars into 283 small constellations, representing different parts of the Empire.

On 7 December, AD 185, for instance, Chinese astronomers spotted a brilliant new star and reported: “A guest star appeared within the Southern Gate. It was as large as half a mat; it showed the five colours and it scintillated.”

The Astronomer Royal alerted the Emperor, and decisive action was taken against the region corresponding to the Southern Gate. “The governor of the metropolitan region Yuan Shao punished and eliminated the middle officials… and several thousand people were killed.”

The Chinese astronomers kept watch from a raised platform, where four observers faced north, south, east and west; while a fifth lay on his back and looked straight upwards – surely the best job! The next morning they reported to the Astronomical Bureau, which kept records from 206 BC to AD 1912 – the longest-lived bureaucracy the world has ever seen.

Today, astronomers can mine this ancient archive for unique information on astronomical events.

Read more about how modern astronomers put ancient information to use...