World's Oldest Seismometer made by Chinese

According to modern calendar calculations, a strange instrument was made in the royal court of China in the second century.From a distance, it looks like a huge pot.A total of 8 heads of the dragon, the symbol of Chinese tradition, came out of that pot.Just below the head of the dragon, there are 8 metal frogs staring at the sky with hungry expressions.Designed by frogs and dragons, many mistakenly think of it as an artistic representation of the emperor's merriment.But it can be said with certainty that this instrument is not a work of art and has nothing to do with the entertainment of the emperor.Even then, the device has been kept under strict surveillance by the royal guards at a certain place in the emperor's court for a long time.The guards' job was to keep an eye on the dragon's face.They keep an eye on the faces of those dragons day after day.There seems to be no end to this surveillance.

But one day a metal sphere came out of the mouth of a dragon in front of the eyes of the guards.It went straight into the mouth of a hungry frog.At once the walls of the preserved cell trembled at the sound of the spoon hitting the cassava.The royal guards immediately rushed to the emperor's court.On the way, the news reached the ears of the people, "The dragons of 'Hu-fang Didong E' have woken up."

 Instrumentation techniques:--

Zhang Hang's instrument looks like an 8-foot-diameter bronze vessel from the outside.In China at that time, such pots were usually used to hold wine and beverages.There were 6 dragons on the pot.  In Chinese culture, it was customary to determine the position of an object using a total of six aspects.Each dragon's face pointed in those six directions.Just below the dragon's head were six metal frogs.This is the description of the outside of the pot.Inside the pot, Zhang Hang put across a delicate pendulum.He filled the empty space inside the pot with a liquid that scientists are still in the dark about.It is not possible to know the technique of this instrument and the nature of the liquid it contains from the vague text of the ancient Chinese manuscript.

Researchers are still confused about the fine-tuning of the device.However, in simple terms, they said, the pendulum inside the pot would move in a certain direction as soon as the vibration caused by the earthquake was felt.As a result, the metal sphere placed on that side would hit the pendulum and fall into the mouth of the frog placed below the dragon's mouth.Surprisingly, the device would not have been affected by the vibrations except for earthquakes in its vicinity.But how Zhang Hang accomplished this complex task at the time is beyond the comprehension of scientists.After the metal sphere fell into the frog's mouth, it would alert the guards with a loud noise.It would not only indicate an earthquake, but also its direction and location.