Chinese seismologists and replica of ‘Didong Yi’
Chinese seismologists and archeologists have announced that they’ve created
a replica of ‘Didong Yi,’ the world’s first seismograph.

    The announcement in Zhengzhou, capital of central
China’s HenanProvince, also home to the seismograph’s original inventor
Zhang Heng (78-139 AD), came almost two months after the device passed relevant
appraisal and examination by a scientific committee in April.

    Seven scientists in seismology, archeology and
mechanical engineering from Chinese Academy of Sciences, the National Museum
and China Earthquake Administration confirmed that the replica wasa ‘historic
step’ towards complete reconstruction.

    ‘We believe the newly restored seismograph model
is the best atpresent,’ said Academician Teng Jiwen, a research fellow at
the Institute of Geology and Geophysics under the Chinese Academy of Sciences,
China’s top scientific research body.

    ‘It represents our current utmost understanding
of the ancient Didong instrument,’ said Teng, who was among the seven-member
appraisal and examination panel.

    According to the History of Later Han Dynasty (25-220
AD), Zhang Heng’s seismograph was an urn-like instrument with a centralpendulum.
An earth tremor would cause the pendulum to loose balance and activate a
set of levers inside. Then, one of the eight dragons placed in eight directions
outside the urn would release a bronze ball held in its mouth. The ball
would fall into the mouth of a toad and give off a sound in the meantime,
letting people know when and in which direction an earthquake had occurred.

    The Han-style wine goblet-like replica with a ridgy
coping, canrespond to the reproduced waves of four actual earthquake events
in Tangshan, Yunnan, the Qinghai-Tibet Plateau and Vietnam, according to
scientists and designers.

    They say the test of the model’s internal mechanism
with modernearthquake graphs is scientific and accurate and the shape of
the replica is very close to the original one described in history books.

    ‘What we are exhibiting is a scientific device,
not a toy,’ said Tian Kai, deputy curator of Henan Museum, where a smaller-sized
new replica is on show.

    ‘If we put a seismograph that is unable to move
or detect on exhibition,’ Tian said, ‘we will not only deceive our audience,
but also show our apathy and irresponsibility towards our nation’ssplendid
cultural legacy.’

    Invented by Zhang Heng in 132 AD and rejoiced in
the Chinese name ‘Houfeng Didong Yi’ (Instrument for inquiring into the wind
and the shaking of the earth), the original of the seismograph didnot survive
history. It is recorded as detecting an earthquake in February in the year
138 about 600 kilometers away from Luoyang, then China’s capital,according
to the History of the Later Han.

    The Didong Yi was first reconstructed by a Japanese
scholar in 1875 based on the description about the device in Zhang’s biography
in the History of the Latter Han and archaeological research findings. The
currently well-known model was redesigned by noted Chinese museum researcher
Wang Zhenduo in 1951. None of the replicas could detect an earthquake.

    ‘As a treasure of our Chinese nation, Didong Yi
is an attractive goal for reconstruction to scientists around the globe,’
Teng said. ‘If we can’t get the job done, it will be our fault.’

    However, there has been some scholarly disagreement
about the exact scientific principles applied on the seismograph and how
precisely the instrument originally worked.

    Some foreign seismologists argue that if Zhang
Heng’s seismograph worked on principles of inertia, then two (not one) ‘pearls’
should fall out from mouths of dragons on opposite sides of the device.

    Others hold that all the replicas are just reconstructed
from our guess and imagination rather than from our true knowledge as to
how the real device used to look like. A few Western scholars even contend
Zhang Heng’s device was lost because it was never a reality.

    Feng Rui, a China Seismological Networks Center
research fellow who heads the restoration team, believes he and his colleagues
cantestify the existence of Zhang Heng’s seismograph through collection
of historical data and simulated analysis.

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