Discover the World’s First Earthquake Detector, Invented in China 2,000 Years Ago
The Renaissance did not, strictly speaking, occur in China. Yet it seems that the Middle Kingdom did have its Renaissance men, so to speak, and in much earlier times at that. We find one such illustrious figure in the Han dynasty of the first and second centuries: a statesman named Zhang Heng (78–139 AD), who managed to distinguish himself across a range of fields from mathematics to astronomy to philosophy to poetry. His accomplishments in science and technology include inventing the first hydraulic armillary sphere for observing the heavens, improving water clocks with a secondary tank, calculating pi further than it had been in China to date, and making discoveries about the nature of the moon. He also, so records show, put together the first-ever seismoscope, a device for detecting earthquakes.
A visual explanation of Zhang’s design appears in the ScienceWorld video above. His seismoscope, its narrator says, “was called hòufēng dìdòngyí, which means ‘instrument for measuring seasonal winds and movements of the earth,’ ” and it could “determine roughly the direction in which an earthquake occurred.”
Each of its eight dragon heads (a combination of number and creature that, in China, could hardly be more auspicious) holds a ball; when the ground shook, the dragon pointing toward the epicenter of the quake drops its ball into the mouth of one of the decorative toads waiting below. At one time, as history has recorded, it “detected an earthquake 650 kilometers, or 400 miles away, that wasn’t felt at the location of the seismoscope.”
Not bad, considering that neither Zhang nor anyone else had yet heard of tectonic plates. But as all engineers know, practical devices often work just fine even in the absence of completely sound theory. Though no contemporary examples of hòufēng dìdòngyí survive from Zhang’s time, “researchers believe that inside the seismoscope were a pendulum, a bronze ball under the pendulum, eight channels, and eight levers that activated the dragons’ mouths.” Moving in response to a shock wave, the pendulum would release the ball in the opposite direction, which would roll down a channel and release the mouth at the end of it. However innovative it was for its time, this scheme could, of course, provide no information about exactly how far away the earthquake happened, to say nothing of prediction. Fortunately, centuries of Renaissance men still lay ahead to figure all that out.
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Based in Seoul, Colin Marshall writes and broadcasts on cities, language, and culture. He’s the author of the newsletter Books on Cities as well as the books 한국 요약 금지 (No Summarizing Korea) and Korean Newtro. Follow him on the social network formerly known as Twitter at @colinmarshall.