Reviving a legend: China rebuilds 2,000-year-old ancient earthquake device

Scientists recreate 2000-year-old Chinese quake sensor (Image: SCMP)

For centuries, earthquakes have posed a serious threat to humanity. Today, scientists use satellites, supercomputers, and artificial intelligence to monitor seismic activity and improve earthquake prediction.

Remarkably, nearly 2,000 years ago, Chinese scholar Zhang Heng is believed to have invented a groundbreaking device called the Houfeng Didong Yi - an ancient seismoscope said to detect distant earthquakes and even indicate their direction.

A team of researchers in China is working to recreate Zhang Heng's ancient seismoscope using modern science, aiming to prove the invention was real.

Although the device is mentioned in historical texts like The Book of the Later Han, some scholars question its authenticity, calling it a myth. In fact, it was removed from China’s school curriculum in 2017 due to these doubts.
But now after getting support from modern science and fresh clues, a research team in China is now seeking to restore this lost wonder of antiquity – the Houfeng Didong Yi seismoscope – to its rightful place.

Ancient tech meets modern science

This machine had a very simple mechanism. Imagine an elaborately crafted wine jar, encircled by eight dragons, each gripping a bronze ball in its mouth, with open-mouthed toads poised below. When seismic tremors occurred, an internal mechanism would trigger one dragon to release its ball into a toad’s mouth with a distinct clang - revealing the direction of the quake.

Created in 132 AD during China’s Eastern Han dynasty, it was one of the earliest seismoscopes - built over 1,700 years before similar European devices.

According to The Book of the Later Han, its name signifies is a instrument for measuring the seasonal winds and the movements of the Earth, it was “as accurate as the gods” as per the books.

Alrthopugh, its physical existence later faded from historical records, fueling scholarly debate.

Associate Professor Xu Guodong of the Institute of Disaster Prevention in Hebei is attempting to change that. Using advanced knowledge in seismic science and structural dynamics, his team has proposed a new functional model of Zhang Heng’s legendary invention.

Xu’s research, initially published in March in the Chinese journal Progress in Geophysics, outlines a reconstruction that incorporates three key elements: an excitation structure, a transmission system, and a shutdown mechanism.

Drawing inspiration from historical descriptions, Xu explained that “in the centre stands the capital pillar, with eight channels radiating outward” - a line that has guided previous reconstruction attempts. However, interpretations of the “capital pillar” have varied widely.

“The interpretation of this ‘capital pillar’ has been pivotal in deducing the seismoscope’s detection principle,” Xu told the South China Morning Post in a recent interview.

“But our analysis of the literature suggests the ‘capital pillar’ connotes centrality and grandeur, [and it is] unlikely to be an unstable or easily toppled rod. This ‘column’ should actually be understood as a pendulum-style cantilever, resembling a giant chopstick anchored in the ground.”

Though doubts remain, Xu’s model aims to bridge the gap between ancient ingenuity and modern science, potentially reviving one of history’s most mysterious inventions.

Xu’s research, published in Progress in Geophysics in March, aims to restore the Houfeng Didong Yi’s place as a marvel of ancient engineering.