Zhang Heng Invents the Seismoscope

Timeline

1. 132Luoyang · ChinaZhang Heng designed and cast the houfeng didong yi, with a bronze vessel as the main body, an internal central column and eight trigger mechanisms, and eight dragons and toads on the outside, to detect earthquakes and indicate direction.
2. 138Luoyang · ChinaThe seismoscope triggered in Luoyang with the western bronze ball dropping; days later, a courier report confirmed an earthquake in Longxi, while Luoyang itself felt no tremor, proving the instrument's long-range detection capability.