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Zhang Heng: seismoscope
Model of Zhang Heng's seismoscope (seismograph), which he invented about 132 ce to detect earthquakes.
Zhang Heng
Chinese mathematician, astronomer, and geographer
Also known as: Chang Heng
Quick Facts
Zhang Heng (born 78 ce—died 139) was a Chinese mathematician, astronomer, and geographer. His seismoscope for registering earthquakes was apparently cylindrical in shape, with eight dragons’ heads arranged around its upper circumference, each with a ball in its mouth. Below were eight frogs, each directly under a dragon’s head. When an earthquake occurred, a ball dropped and was caught by a frog’s mouth, generating a sound.