revised res paper

Earthquake predictor?

Ancient Chinese has many inventions, but it looks like many of them only appear on book but never have a solid evidence of their existence. In other words, we lack visual evidences.

One great example is the seismometer, or “Didongyi”, its original name. Roughly around 132 A.D, earthquakes took place in the northern China frequently, leading to tremendous damage to residents and the government. Experiencing the earthquake, a scientist known as Zhangheng invented an earthquake predictor.

Didongyi refers to “a device based on the movement of the ground.”  The mechanism inside of the device remains mystery until recent decades. From the historical descriptions, Zhang’s “dragon jar” sounds pretty fantastic–an enormous vase, six feet in diameter, with eight dragon heads arranged around the rim, each facing one of the eight directions (east, west, north, south, northeast, northwest, southeast and southwest) and each holding a ball in its mouth (Earthquake Detection Past and Present).

In general, the device can detect the direct in which the earthquake comes. According to an official chronological book named Houhanshu, in 138 A.D, one of the balls in a dragon (as shown on the left) fell into an east-pointed toad’s month. The predictor thus indicated that the earthquake came from the east of the capital city, Luoyang. At first people doubted the predictor’s accuracy because no one sensed an earthquake in a short range of the city. However, a few days later messengers from a city far east from Luoyang reported an earthquake occurred. People, even the emperor, then began to believe the predictor.

Interesting thing here is that the seismometer received controversies recently. While the device keeps astonishing us, many scholars in China now skeptic the reality of the seismometer. As mentioned before, one critical factor is that we lack a visual evidence of its existence. Images we find now on the internet are replicas, and even ones that look like an “ancient drawing” is also contemporary products. In Houhanshu, an authoritative book recording many events in Han dynasty, historians only found 196 words regarding the seismometer. Therefore, we may have exaggerated it during the way we visualize it. Consequently, experts are now calling to remove the seismometer from all textbooks in school to stop misleading students.

Nevertheless, the predictor does exist, and it helps us better understand the history in that period. Recovering regions that suffer from natural disasters was one of the most important jobs of “government” in the ancient China. Although the device can not actually detect the earthquake in advance, it helped the authority distribute assistance to impacted areas rapidly. Just like the firework, which served as a cultural and religious purpose, the seismometer could also play a role in enhancing the emperor’s authority rather than “predict” the earthquake.


Words: 458


“The incredible earthquake detector invented nearly 2,000 years ago”, April Holloway


“Earthquake Detection Past and Present”, Wall Street Journal, Jun 5, 2008


2,000-Year-Old Earthquake Detector Worked with Accuracy in China, Tara Macisaac, Epoch Times



“Seismology in Ancient China.” Science and Its Times: Understanding the Social Significance of Scientific Discovery. Dec. 2018


“World’s first earthquake detector was invented 2000 years ago in China”, Dragos Mitrica, last updated on April 26, 2017.

The ancient earthquake detector that puzzled modern historians, Jamie Rigg, 09/28/2018

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