Ancient Seismoscope – 132 AD
Earthquakes have long been a source of mystery for scientists, predicting them has proven to be a challenge and detecting them has been a process that scientists have been exploring for nearly 2,000 years. The first known evidence of a device used to detect earthquakes comes from Zhang Heng.
What was remarkable about Zhang Heng’s device was that it was able to detect earthquakes from long distances and was able to indicate which direction the earthquake was. The device was able to detect earthquakes even if there was no shaking in the area where it was located. This is certainly a marvel of engineering and the distances that earthquakes could be detected continues to amaze scientists to this day.
The ancient seismoscope consisted of a large bronze vessel that was six feet in diameter. Eight dragons were featured around the outside of the vessel and marked the main directions of the compass. In the mouth of each dragon was a small ball that was held in place solely by the clamped jaws of the dragon. Beneath each dragon were eight toads with their mouths open toward the dragon. When an earthquake happened one dragon would drop the ball into the mouth of the toad to indicate the direction of the earthquake. In 138 AD, the device indicated an earthquake west of Luoyang, the capital city, but no one had sensed an earthquake there. However, a few days later, a messenger from the western Long region brought news of an earthquake. This sufficiently proved the device to the people of the era.
There is still no real understanding of how the device worked. Some believed that there was a thin set loosely set in the barrel and then the force of the earthquake would cause the stick to topple in the direction of the seismic activity. In 2005, scientists recreated the device using this theory and found that it worked as well as modern seismometers in a series of tests.