In 132 AD in China, the inventor Zhang Heng introduced the first seismoscope believed to be capable of predicting earthquakes with the precision of modern instruments.
Historical records have preserved an accurate description of its appearance and how it functioned, but the exact internal design is still a mystery. Scientists have repeatedly attempted to create a model of such a seismoscope, putting forward various theories about the principle of its operation.
The most common of them says that a pendulum inside a copper bulb starts to move during tremors, even if the epicenter of the earthquake is hundreds of kilometers away. In turn, the pendulum struck on a system of levers, with which the mouth of one of the eight dragons located outside was opened.
In the mouth of each animal was a bronze ball, which fell into an iron toad, making a loud ringing. Historical essays say that the sound produced was so loud that it could wake all the inhabitants of the imperial court.
The dragon, the mouth of which was opened, indicated in which direction the earthquake occurred. Each of the eight animals belonged to one of the directions: East, West, North, South, northeast, northwest, southeast and southwest, respectively.
The invention was initially met with skepticism, despite the fact that Zhang was already a famous scientist at that time, who was appointed by the imperial court to the post of chief astronomer. But around 138 AD, the bronze ball sounded the first alarm, indicating that the earthquake had occurred west of the capital Luoyang.
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The signal was ignored, as no one in the city felt the signs of an earthquake. A few days later, a messenger arrived from Luoyang with the news of severe destruction: the city, located at a distance of 300 km, lay in ruins as a result of a natural disaster.
A scientist from the Institute of Geophysics in China determined that the first earthquake detected by such a seismoscope occurred on December 13, 134, and had a magnitude of 7.
Thus, the apparatus was created to detect earthquakes in remote regions, but it functioned only during the lifetime of its inventor. Apparently, the device of the first seismoscope was so complex that only the scientist himself could keep it in working order.
Modern attempts to recreate a copy have met with mixed success, and all of them have been created using inertia, a principle that is used in modern seismographs.
In 1939, a Japanese scientist created a model of such a seismoscope, but not in all cases the ball fell exactly in the direction of the epicenter of the earthquake.
Scientists from the Chinese Academy of Sciences, the National Museum and the Chinese Seismological Bureau managed to create a more accurate reconstruction of the invention in 2005.
According to the Chinese media, the device reacted accurately to the reproduced waves of five earthquakes that occurred in Tangshan, Yunnan, Qinghai-Tibet Plateau and Vietnam. Compared to modern instruments, the seismoscope showed amazing accuracy, and its shape was the same as described in historical texts.
However, not everyone is inclined to believe in the efficiency of the first seismoscope. Robert Reiterman, executive director of the Universities Consortium for Earthquake Engineering Research, expressed skepticism about the accuracy of the historical narrative apparatus.
“If the epicenter of the earthquake was at a close distance, the whole structure was shaking so much that balls would fall out of all dragons at the same time. At a distant distance, the movements of the earth do not leave a clear trace to identify from which side the vibrations are emanating. Since until the moment when the vibrations of the earth's surface reach the seismoscope, they occur in different directions, most likely chaotically, "he writes in his book" Engineers and Earthquakes: An International History."
If the seismoscope really worked as accurately as it was described in the historical records, which is also hinted at by the functioning of modern copies, then Zhang's genius still remains inaccessible.
Zhang Heng (78 - 139) is a Chinese philosopher, encyclopedic thinker, writer, poet, statesman and scientist who owns world discoveries and inventions in mathematics, astronomy, mechanics, seismology and geography.