Invention of China: Seismometer

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Ancient Chinese Seismometer A seismometer -- an earthquake detector, also called a seismograph -- was invented in 132 A.D., by Chang Heng, a brilliant mathematician and scientist in the Han Dynasty of China. The ancient Chinese believed seismic events, with their death and destruction, were important signs from heaven. So it was important to the Chinese leaders to be alerted to earthquakes occurring anywhere in the kingdom. A correct call about an earthquake occurring won a person immortal fame, as in Chang Heng’s case. A wrong call about an earthquake resulted in disgrace and punishment. What did the original seismometer look like? Cheng Heng’s original seismometer was lost. Luckily, its description survived. It was a cast bronze vessel with a domed lid, resembling a wine jar. The working insides, of were hidden. The surface of the vessel was decorated with motifs of mountains, tortoises, birds, animals and antique writing. Around the vessel were eight dragons whose mouths each held a ball. Around the base of the vessel sat eight corresponding toads with their mouths open, looking upwards. (Fig. 1) Fig. 1 – Ancient Chinese seismometer. Notice the dragons around the vessel and the toads beneath them. The sign for an earthquake was the falling of a ball from the dragon into the mouth of a toad. The direction of the earthquake is indicated by the position of the toad which swallowed the ball. This instrument was most remarkable. On one occasion one of the dragons let fall a ball from its mouth though no perceptible shock could be felt. All the scholars at the capital were astonished at this strange effect occurring without any evidence of an earthquake to cause it. But several days later a messenger arrived, bringing news of an earthquake in Lung-Hsi (400 miles away). Upon this everyone admitted the mysterious power of Chang Heng’s instrument.The workings of

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