Zhang Heng's seismoscope
Sismoscopio de Zhang Heng
- Date
- 132 CE · confidence high
- Place
- Luoyang, Henan, China
- Credited to
- Zhang Heng, astronomer of the Han court
- People
- 👤 Zhang Heng78–139
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
A bronze vessel with an internal pendulum that, on sensing a seismic wave, drops a ball from the mouth of one of eight dragons into the corresponding toad, indicating the direction of the earthquake. The first instrument for detecting distant earthquakes.
The internal mechanism has not survived; modern reconstructions (Wang Zhenduo, Feng Rui) work with an inverted pendulum. It detected an earthquake in Gansu in 138 CE according to the Hou Hanshu.
What it led to
- Detection of earthquakes in distant provinces so imperial aid could be sent
- Instrumental science of phenomena invisible to the senses
- A conceptual precedent for instrumental seismology (19th century)
Built on
- China's documentary earthquake record (from c. 780 BC)desde c. 780 BCE
- Pendulum clock1656
- Chinese bronze casting
- Lever and trigger
Made possible
- Horizontal-pendulum seismograph1880
- Modern seismograph
- Zhang Heng's hydraulic armillary sphere