ancient seismometer

grabcad

This Iranian magazine model features a description of Zhang Heng's invention, the first seismoscope, dating back to AD 132 during China's Han dynasty. Known as Houfeng Didong Yi, which translates to "instrument for measuring seasonal winds and Earth movements," it was a large bronze vessel with dragon heads at its top, each holding a ball. An earthquake would trigger the opening of one dragon's mouth, causing its ball to fall into a bronze toad below, signaling the quake's direction. In AD 143, the seismoscope accurately detected an earthquake in Gansu despite no felt tremors. Its central column moved along eight tracks, possibly using a pendulum mechanism, with the first recorded earthquake reportedly originating from the east. Please share your thoughts on this fascinating invention!