Modern seismographs are very sensitive and react even to the weakest tremors. Now all over the world thousands of devices are in constant service, which can record seismic activity with high accuracy. But, as it turned out, a similar device already existed in ancient China almost 2000 years ago.
Chinese scholar Zhang Heng lived during the Han Dynasty in the 2nd century AD. As a simple official at the imperial court, he studied astronomy, mathematics, mechanics, cartography, poetry and applied arts. However, he went down in history as the creator of the world's first known seismograph, which he presented to the emperor in 132 AD. e. 7 years before his death.
Unfortunately, the seismograph itself has not survived. Only a description of it has come down to us. In it, he is depicted in the form of a massive bronze urn or vase. Outside, it was decorated with eight dragons, placed upside down, in the mouth of which were balls. Directly under the dragons were 8 bronze toads with open mouths, where the balls were supposed to fall.
In ancient texts, the principle of operation of this device is described very vaguely. Scientists believe that inside the device was a pendulum and linkages associated with each dragon. When tremors occurred, the pendulum began to swing, setting one of the levers in motion.
As a result, a ball fell out of the mouth of the dragon corresponding to it directly into the mouth of the toad, informing others not only about the earthquake, but also the direction of propagation of seismic waves, since each toad was oriented towards a certain part of the world.
All attempts to accurately determine the principle of operation of the ancient device in the 19-20 centuries were unsuccessful. It remained unclear, for example, how the pendulum could “sense” earthquakes occurring hundreds of kilometers away.