In the year 132 CE, a brilliant Chinese astronomer, mathematician and engineer named Zhang Heng presented to the Han court an impressive invention—the world’s first seismoscope.

A seismoscope is an instrument that indicates the shaking of the earth during an earthquake. It should not be confused with a seismometer or a seismograph that also records the movement. In essence, any hanging pendulum or a delicately balanced object that can topple at the slightest disturbance will function as a seismoscope. It’s naïve to believe that such instruments didn’t exist before Zhang Heng’s invention. But what makes Heng’s seismoscope special is its sensitivity and its ability to tell the direction where the earthquake came from.

A replica of Zhang Heng’s seismoscope. Photo credit: Encyclopaedia Britannica