China resurrects world's earliest seismograph
13/6/2005 15:15
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 Henan Province, 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 was a "historic step"
towards complete reconstruction.
"We believe the newly restored seismograph
model is the best at present," 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 central pendulum. 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, can respond 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
modern earthquake 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's splendid 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 did not 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 can testify the existence of Zhang Heng's
seismograph through collection of historical data and simulated
analysis.
Xinhua News
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