2000-year old earthquake detector

Image Source: ZME Science

This ornate object was actually an instrument to detect earthquakes.

Yes, it is not possible to accurately predict earthquakes. However, over the centuries, we have come a long way in detecting, recording and estimating the severity of seismic shocks.

But this device, the doomwatch dragons as it was called, was remarkably accurate in detecting earthquakes, and did not rely on movement in the location where it was placed. Invented by Chinese astronomer Zhang Heng in 132 AD, it was indirectly the forerunner of the modern seismograph.

Zhang Heng (Chinese: 張衡; AD 78–139)

It is due to the shifting of the tectonic plates in the Earth’s crust that primarily causes earthquakes, but the Chinese neither understood nor believed this. Instead, they suggested that earthquakes are a result of the disturbances with cosmic yin and yang, along with the heaven’s displeasure with act’s committed or grievances ignored by the current ruling dynasty. As they believed that these seismic events were important signs from heaven, it was very important for the leaders to be alerted to occurring anywhere in their kingdom.


The Doomwatch Dragons was a giant vessel (8 ft high and almost 6 ft in diameter) made of bronze, with eight serpent faced dragons facing down along the outside of the vessel. These were aligned along primary directions of the compass. Each dragons mouth contained a small bronze ball. Beneath these dragons sat eight toads, also aligned along points of the compass, with gaped mouths to receive the balls.

In case of a seismic activity, an oscillating pendulum inside would dislodge one of the eight horizontal arms, opening the jaws of one of the eight dragons, releasing the ball from the dragons’ mouth into the mouth of the frog below the particular drag. Since the frogs were aligned along points of the compass, the frog that contains the ball would indicate the direction of the disaster. Furthermore, the sound of the ball striking one of the toads was loud enough to alert observers.

Nobody believed that this would actually work. The direction in which the dragon had dropped the ball indicated that a quake had occurred to the west of Luoyang, the capital city. People were sceptical because no one had sensed anything in Lyoyang. But a few days later, a messenger from the west of Luoyang, reported an earthquake there. The people were greatly impressed by the device as it had also predicted the exact time of the disaster.

In 2005, scientists in Zengzhou, China (which was also Zhang’s hometown) decided to replicate Zhang’s device and succeeded. They used it to detect simulated earthquakes based on waves from four different real-life earthquakes in China and Vietnam. The doomwatch dragons detected all of them. As a matter of fact, the data gathered from testing the 2000-year old device corresponded accurately with that gathered by modern-day seismometers.

Image Source: Pinterest

No doubt, the doomwatch dragons was a device way ahead of its time.


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