 |
| A replica of an ancient Chinese seismoscope from the Eastern Han Dynasty
(25-220 A.D.), and its inventor, Zhang Heng. (Wikimedia Commons) |
The universe is full of mysteries that challenge our current
knowledge. In "Beyond Science" Epoch Times collects stories about these
strange phenomena to stimulate the imagination and open up previously
undreamed of possibilities. Are they true? You decide.
In 132
A.D., Zhang Heng presented the Han court with the world’s first
seismoscope. A 2005 replica was even said to detect earthquakes with the
same precision as modern instruments.
Historical accounts tell of its great accuracy, though its precise design remains a mystery. The
outer appearance and functioning is known for certain, but its inner
workings remain open to speculation. The replicas have been built on the
best guesses from such speculation.
The most common theory states that a pendulum inside the copper urn
would move when an earthquake occurred, even if the quake was hundreds
of miles away. The pendulum would hit a system of levers to open the
mouth of one of the eight dragons on the outside of the urn. Each
dragon’s mouth contained a bronze ball. This ball would roll out,
landing in the mouth of a toad figurine below, making a loud clang.
A historical account described the ringing in the toad’s mouth to be so loud it could rouse the whole court from sleep,
wrote Dr. Jan Pajak of the Wellington Institute of Technology in a paper prepared for the 2005 International Conference on Sensing Technology.
The dragon that had its mouth opened would be the one pointing in the
direction of the earthquake. The eight dragons pointed east, west,
north, south, northeast, northwest, southeast, and southwest
respectively.
The invention was initially met with skepticism in its day, though
Zhang was already a renowned scientist, selected to be the court’s chief
astronomer. In 138 A.D., a bronze ball sounded the first alarm.
It indicated that the earthquake happened west of Luoyang, the
capital city. No one had felt a quake in Luoyang, so the alarm was
ignored, but a few days later, a messenger from west of Luoyang arrived
in the city to report that his region had experienced an earthquake. The
earthquake had occurred at the same time Zhang’s machine sounded the
alarm. This city of Longxi, some 300 miles away, lay in ruins.
Feng Rui and Yu Yan-Xiang of the Institute of Geophysics, China
Earthquake Administration, deduced in 2006 that this first earthquake
detected by Zhang’s machine was magnitude 7 in Longxi, with an epicenter
at Tianshui on Dec. 13, 134 A.D.
The machine’s purpose was to detect earthquakes in distant regions so
aid could be deployed. It worked until the death of its inventor, but
apparently the device was so complex only Zhang could keep up with its
maintenance effectively.
The seismoscope was called
Houfeng didong yi, the
“instrument for measuring the seasonal winds and the movements of the
Earth.” Modern attempts at replication have met with varying success,
and all were built on the use of inertia, a principle integral to modern
seismographs.
Dr. Pajak explains this use of intertia: “In this
principle an earthquake shakes a frame of an instrument, so that this
frame is displaced in relation to an inertial pendulum, while this
displacement is registered as the indication of an earthquake.”
Attempts to Replicate
In 1939, Japanese scientist Akitsune Imamura built a replica showing
the device to be effective, according to Hong-Sen Yan in the book
“Reconstruction Designs of Lost Ancient Chinese Machinery.”
However, wrote Hong-Sen, “in some circumstances the direction of an
earthquake’s epicenter was found to be at right angles to the dropped
ball.”
In 2005, several scientists from various disciplines at the Chinese
Academy of Sciences, the National Museum, and China Earthquake
Administration declared a new replica to be the best yet.
“It represents our current utmost understanding of the ancient Didong
instrument,” said Teng Jiwen, a research fellow at the Institute of
Geology and Geophysics,
according to a report from that time by state-run media People’s Daily.
The replica reportedly responded to the reproduced waves of four
actual earthquake events in Tangshan, Yunnan, the Qinghai-Tibet Plateau,
and Vietnam. Tested against modern earthquake graphs, the replica was
shown to be accurate and its shape fit that described in historical
texts.
The Inner Workings
Hong-Sen cited a passage from a contemporary biography of Zhang, the
first design specification left to us in historical texts: “There is one
pillar (du zhu) in the center of the interior and eight transmitting
rods near the pillar.”
Transmitting rods would refer to channels through which some object
would be transported, explained Hong-Sen, but nothing more specific is
written about the rods.
Dr. Pajak has another theory. He wrote that the machine has been
described in historical texts as containing water, as having water flow
out of the dragons’ mouths like a fountain.
He hypothesized that the water flowed smoothly (as opposed to
turbulently), a characteristic known as laminar flow. The shape of the
chamber (parabolic) was designed to deflect vibrations coming from the
earthquake zone. The deflected vibrations would focus on the inlet of
the pipe in the appropriate direction, causing the water that had been
washing around the metal ball to push the ball out of the dragon’s
mouth.
Robert Reitherman, executive director of the Consortium of
Universities for Research in Earthquake Engineering, expressed
skepticism concerning the historical accounts of the machine’s accuracy
in his book, “Earthquakes and Engineers: An International History.”
He wrote: “At a close distance, the whole instrument would be so
severely shaken that the balls on multiple perches would have jostled
loose. … At a [far] distance, ground motion from an earthquake does not
leave clear footprints indicating the direction from whence those
vibrations came, because the ground shakes in various directions rather
chaotically by the time it reaches the instrument.”
If this machine worked as well as historical accounts describe, and
if the successes of some modern replicas hint that the machine could
work with such precision, it seems Zhang’s genius remains out of our
grasp for now.
Some of Zhang’s other accomplishments include calculating pi (π) as
being between 3.1466 and 3.1622, refining a time-keeping device know as
an “inflow clepsydra,” and applying hydraulic motive power to rotate an
astronomical instrument known as an armillary sphere.
Link:
http://www.theepochtimes.com/n3/808002-2000-year-old-earthquake-detector-worked-with-accuracy-in-china/
