Zhang Heng invents the seismoscope

Date

132 CE

Category

Science, technology & invention

Region

China (Luoyang)

Era

Classical Antiquity

Significance

In 132 CE the Han polymath Zhang Heng — astronomer, mathematician and court official at Luoyang — presented the houfeng didong yi, the world's first known seismoscope. The bronze instrument was a vessel ringed by eight dragon heads, each holding a ball above an upturned toad.

When a distant earthquake disturbed an internal pendulum-and-lever mechanism, one dragon released its ball into the toad below, indicating the direction from which the tremor came. Historical accounts report that the device detected an earthquake roughly 400 to 500 km away in Gansu before news of it reached the capital, vindicating the instrument against sceptics. Zhang Heng, who also catalogued stars and built water-powered armillary spheres, exemplified the scientific sophistication of Han China. While the original device is lost and its exact internal workings are debated, the seismoscope stands as a landmark in the history of instrumentation and the human effort to measure and understand natural phenomena.

Empires active in 132 CE

• Roman Empire
  27 BCE – 476 CE
• Han Dynasty
  202 BCE – 220 CE
• Kingdom of Funan
  50 CE – 550 CE
• Zapotec State of Monte Albán
  500 BCE – 800 CE
• Kushan Empire
  30 CE – 375 CE
• Parthian Empire
  247 BCE – 224 CE

Related science, technology & invention events

• Cai Lun standardises papermaking
  105 CE
• Ptolemy completes the Almagest
  c. 150 CE
• Compilation of the Charaka Samhita and the Codification of Ayurveda
  c. 100 CE
• Inauguration of the Colosseum (Flavian Amphitheatre)
  80 CE
• The Bakhshali manuscript and the earliest recorded zero
  c. 224–383 CE (carbon-dated)
• Earliest securely dated Maya/Mesoamerican Long Count inscription
  36 BCE (Long Count 7.16.3.2.13)

Further reading

A Little History of Science

The wider story

A Little History of Science

William Bynum

Warm, jargon-free tour of discovery from Babylonian stargazers to the genome.

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