Yi Xing
Encyclopedia
Yi Xing born Zhang Sui , was a Chinese
astronomer
, mathematician
, mechanical engineer
,and Buddhist monk of the Tang Dynasty
(618–907). His astronomical celestial globe featured a clockwork escapement
mechanism, the first in a long tradition of Chinese astronomical clock
works.
. This survey had many purposes. It was established in order to obtain new astronomical data that would aid in the prediction of solar eclipse
s. The survey was also initiated so that flaws in the calendar system
could be corrected and a new, updated calendar installed in its place. The survey was also essential in determining the measurement of the length of meridian arc
. This would resolve the confusion created by the earlier practice of using the difference between shadow lengths of the sun observed at the same time at two places to determine the ground distance between them. This was the same process used by the ancient Greek Eratosthenes
(276–196 BC).
Yi Xing had thirteen test sites established throughout the empire, extending from Jiaozhou
in Vietnam
— at latitude
17°N
— to the region immediately south of Lake Baikal
— latitude 50°N
. There were three observations done for each site, one for the height of polaris
, one for the shadow lengths of summer, and one for the shadow lengths of winter. The latitudes were deciphered from this data, while the Tang calculation for the length of one degree of meridian was fairly accurate compared to modern calculations. Yi Xing understood the variations in the length of a degree of meridian, and criticized earlier scholars who permanently fixed an estimate for shadow lengths for the duration of the entire year.
(a government official), is best known for applying the earliest known escapement
mechanism to a water-powered celestial globe. However, Yi Xing's mechanical genius and achievements were built upon the knowledge and efforts of previous Chinese mechanical engineers, such as the statesman and master of gear systems Zhang Heng
(78–139) of the Han Dynasty
, the equally brilliant engineer Ma Jun
(200–265) of the Three Kingdoms
, and the Daoist Li Lan (c. 450) of the Southern and Northern Dynasties
period.
It was the earlier Chinese inventor Zhang Heng who was the first to apply hydraulic power (i.e. a waterwheel and clepsydra
) in mechanically-driving and rotating his equatorial
armillary sphere
). The arrangement followed the model of a water-wheel using the drip of a clepsydra (see water clock
), which ultimately exerted force on a lug to rotate toothed-gears on a polar-axis shaft. With this, the slow computational movement rotated the armillary sphere according to the recorded movements of the planets and stars. Yi Xing also owed much to the scholarly followers of Ma Jun, who had employed horizontal jack-wheels and other mechanical toys worked by waterwheels. The Daoist Li Lan was an expert at working with water clocks, creating steelyard balances for weighing water that was used in the tank of the clepsydra, providing more inspiration for Yi Xing. Like the earlier water-power employed by Zhang Heng and the later escapement mechanism in the astronomical clock tower
engineered and erected by Su Song
(1020–1101), Yi Xing's celestial globe employed water-power in order for it to rotate and function properly. The historian Joseph Needham
states (Wade-Giles spelling):
In regards to mercury instead of water (as noted in the quote above), the first to apply liquid mercury for motive power of an armillary sphere was Zhang Sixun
in 979 AD (because mercury would not freeze during winter). During his age, the Song Dynasty
(960–1279) era historical text of the Song Shi mentions Yi Xing and the reason why his armillary sphere did not survive the ages after the Tang Dynasty (Wade-Giles spelling):
Earlier Tang era historical texts of the 9th century have this to say of Yi Xing's work in astronomical instruments in the 8th century (Wade-Giles spelling):
-Buddhist Guoqing Temple
of Mount Tiantai in Zhejiang
Province, there is a Chinese pagoda
erected directly outside the temple known as the Memorial Pagoda of Monk Yi Xing. His tomb is also located on Mount Tiantai.
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
, mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, mechanical engineer
Mechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
,and Buddhist monk of the Tang Dynasty
Tang Dynasty
The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(618–907). His astronomical celestial globe featured a clockwork escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
mechanism, the first in a long tradition of Chinese astronomical clock
Astronomical clock
An astronomical clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.-Definition:...
works.
Terrestrial-astronomical survey
In the early 8th century, the Tang court put Yi Xing in charge of a terrestrial-astronomical surveySurveying
See Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...
. This survey had many purposes. It was established in order to obtain new astronomical data that would aid in the prediction of solar eclipse
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
s. The survey was also initiated so that flaws in the calendar system
Chinese calendar
The Chinese calendar is a lunisolar calendar, incorporating elements of a lunar calendar with those of a solar calendar. It is not exclusive to China, but followed by many other Asian cultures as well...
could be corrected and a new, updated calendar installed in its place. The survey was also essential in determining the measurement of the length of meridian arc
Meridian arc
In geodesy, a meridian arc measurement is a highly accurate determination of the distance between two points with the same longitude. Two or more such determinations at different locations then specify the shape of the reference ellipsoid which best approximates the shape of the geoid. This...
. This would resolve the confusion created by the earlier practice of using the difference between shadow lengths of the sun observed at the same time at two places to determine the ground distance between them. This was the same process used by the ancient Greek Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...
(276–196 BC).
Yi Xing had thirteen test sites established throughout the empire, extending from Jiaozhou
Jiaozhou (region)
Jiaozhou is an ancient Chinese region. The territory defined by the region has been changed in different eras. Normally included modern North Vietnam and Guangxi...
in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
— at latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
17°N
17th parallel north
The 17th parallel north is a circle of latitude that is 17 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, Central America, the Caribbean and the Atlantic Ocean....
— to the region immediately south of Lake Baikal
Lake Baikal
Lake Baikal is the world's oldest at 30 million years old and deepest lake with an average depth of 744.4 metres.Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the...
— latitude 50°N
50th parallel north
The 50th parallel north is a circle of latitude that is 50 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
. There were three observations done for each site, one for the height of polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....
, one for the shadow lengths of summer, and one for the shadow lengths of winter. The latitudes were deciphered from this data, while the Tang calculation for the length of one degree of meridian was fairly accurate compared to modern calculations. Yi Xing understood the variations in the length of a degree of meridian, and criticized earlier scholars who permanently fixed an estimate for shadow lengths for the duration of the entire year.
The escapement and celestial globe
Yi Xing was famed for his genius, known to have calculated the number of possible positions on a go board game (though without a symbol for zero he had difficulties expressing the number). He, along with his associate Liang LingzanLiang Lingzan
Liang Lingzan was a Tang Dynasty military engineer and government official of the Kaiyuan era. He invented a mechanized water clock with the Tantric monk and mathematician Yi Xing . It was actually an astronomical instrument that served as a clock, made of bronze in the capital of Chang'an in the...
(a government official), is best known for applying the earliest known escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
mechanism to a water-powered celestial globe. However, Yi Xing's mechanical genius and achievements were built upon the knowledge and efforts of previous Chinese mechanical engineers, such as the statesman and master of gear systems Zhang Heng
Zhang Heng
Zhang Heng was a Chinese astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar from Nanyang, Henan. He lived during the Eastern Han Dynasty of China. He was educated in the capital cities of Luoyang and Chang'an, and began his career as a...
(78–139) of the Han Dynasty
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...
, the equally brilliant engineer Ma Jun
Ma Jun
Ma Jun , style name Deheng , was a Chinese mechanical engineer and government official during the Three Kingdoms era of China...
(200–265) of the Three Kingdoms
Three Kingdoms
The Three Kingdoms period was a period in Chinese history, part of an era of disunity called the "Six Dynasties" following immediately the loss of de facto power of the Han Dynasty rulers. In a strict academic sense it refers to the period between the foundation of the state of Wei in 220 and the...
, and the Daoist Li Lan (c. 450) of the Southern and Northern Dynasties
Southern and Northern Dynasties
The Southern and Northern Dynasties was a period in the history of China that lasted from 420 to 589 AD. Though an age of civil war and political chaos, it was also a time of flourishing arts and culture, advancement in technology, and the spreading of Mahayana Buddhism and Daoism...
period.
It was the earlier Chinese inventor Zhang Heng who was the first to apply hydraulic power (i.e. a waterwheel and clepsydra
Clepsydra
Clepsydra may refer to:*Clepsydra , the Greek word for water clock. Also, in ancient Greece, a device for drawing liquids from vats too large to pour, which utilized the principles of air pressure to transport the liquid from one container to another.* Clepsydra Geyser in the Lower Geyser Basin of...
) in mechanically-driving and rotating his equatorial
Equatorial
Equatorial may refer to:* Equator of the Earth* Equatorial climate in meteorology* The ring-shaped outer boundary of the cross-section of a round three dimensional shape or object in geometry* The equatorial bond of a molecule in chemistry...
armillary sphere
Armillary sphere
An armillary sphere is a model of objects in the sky , consisting of a spherical framework of rings, centred on Earth, that represent lines of celestial longitude and latitude and other astronomically important features such as the ecliptic...
). The arrangement followed the model of a water-wheel using the drip of a clepsydra (see water clock
Water clock
A water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into or out from a vessel where the amount is then measured.Water clocks, along with sundials, are likely to be the oldest time-measuring instruments, with the only exceptions...
), which ultimately exerted force on a lug to rotate toothed-gears on a polar-axis shaft. With this, the slow computational movement rotated the armillary sphere according to the recorded movements of the planets and stars. Yi Xing also owed much to the scholarly followers of Ma Jun, who had employed horizontal jack-wheels and other mechanical toys worked by waterwheels. The Daoist Li Lan was an expert at working with water clocks, creating steelyard balances for weighing water that was used in the tank of the clepsydra, providing more inspiration for Yi Xing. Like the earlier water-power employed by Zhang Heng and the later escapement mechanism in the astronomical clock tower
Clock tower
A clock tower is a tower specifically built with one or more clock faces. Clock towers can be either freestanding or part of a church or municipal building such as a town hall. Some clock towers are not true clock towers having had their clock faces added to an already existing building...
engineered and erected by Su Song
Su Song
Su Song was a renowned Chinese polymath who specialized himself as a statesman, astronomer, cartographer, horologist, pharmacologist, mineralogist, zoologist, botanist, mechanical and architectural engineer, poet, antiquarian, and ambassador of the Song Dynasty .Su Song was the engineer of a...
(1020–1101), Yi Xing's celestial globe employed water-power in order for it to rotate and function properly. The historian Joseph Needham
Joseph Needham
Noel Joseph Terence Montgomery Needham, CH, FRS, FBA , also known as Li Yuese , was a British scientist, historian and sinologist known for his scientific research and writing on the history of Chinese science. He was elected a fellow of the Royal Society in 1941, and as a fellow of the British...
states (Wade-Giles spelling):
When the first escapement came, in +725 (AD), I-Hsing and Liang Ling-tsan arranged for two jacks to strike the hours, standing on the horizon surface of their sphere or globe.
In regards to mercury instead of water (as noted in the quote above), the first to apply liquid mercury for motive power of an armillary sphere was Zhang Sixun
Zhang Sixun
Zhang Sixun was a Chinese astronomer and military engineer from Bazhong, Sichuan during the early Song Dynasty . He is credited with creating an armillary sphere for his astronomical clock tower that employed the use of liquid mercury...
in 979 AD (because mercury would not freeze during winter). During his age, the Song Dynasty
Song Dynasty
The Song Dynasty was a ruling dynasty in China between 960 and 1279; it succeeded the Five Dynasties and Ten Kingdoms Period, and was followed by the Yuan Dynasty. It was the first government in world history to issue banknotes or paper money, and the first Chinese government to establish a...
(960–1279) era historical text of the Song Shi mentions Yi Xing and the reason why his armillary sphere did not survive the ages after the Tang Dynasty (Wade-Giles spelling):
A jade balancing mechanism (yu heng)(ie. the escapement) is erected behind (lit. outside) a curtain, holding and resisting (chhih o) the main scoops (shu tou). Water pours down rotating the wheel (chu shui chi lun). Lower, there is a cog-wheel (chi lun) with 43 (teeth). There are also hooks, pins, and interlocking rods one holding another (kou chien chiao tsho hsiang chhih). Each (wheel) moves the next without reliance on any human force. The fastest wheel turns round each day through 2928 teeth (chhih), the slowest one moves by 1 tooth in every 5 days. Such a great difference is there between the speed of the wheels, yet all of them depend on one single driving mechanism. In precision, the engine can be compared with Nature itself (lit. the maker of all things; tsao wu che). As for the rest, it is much the same as the apparatus made (long ago) by I-Hsing. But that old design employed mainly bronze and iron, which corroded and rusted so that the machine ceased to be able to move automatically. The modern plan substitutes hard wood for these parts, as beautiful as jade...
Earlier Tang era historical texts of the 9th century have this to say of Yi Xing's work in astronomical instruments in the 8th century (Wade-Giles spelling):
One (of these) was made in the image of the round heavens (yuan thien chih hsiang) and on it were shown the lunar mansions (hsiu) in their order, the equator and the degrees of the heavenly circumference. Water, flowing (into scoops), turned a wheel automatically (chu shui chi lun, ling chhi tzu chuan), rotating it (the sphere) one complete revolution in one day and night. Besides this, there were two rings (lit. wheels) fitted round the celestial (sphere) outside, having the sun and moon threaded on them, and there were made to move in circling orbit (ling te yun hsing). Each day as the celestial (sphere) turned one revolution westwards, the sun made its way one degree eastwards, and the moon 13 and 7/19 degrees (eastwards). After 29 and a fraction rotations (of the celestial sphere) the sun and moon met. After it made 365 rotations the sun accomplished its complete circuit. And they made a wooden casing the surface of which represented the horizon, since the instrument was half sunk in it. This permitted the exact determinations of the times of dawns and dusks, full and new moons, tarrying and hurrying. Moreover there were two wooden jacks standing on the horizon surface, having one a bell and the other a drum in front of it, the bell being struck automatically to indicate the hours, and the drum being beaten automatically to indicate the quarters.
All these motions were brought about (by machinery) within the casing, each depending on wheels and shafts (lun chu), hooks, pins and interlocking rods (kou chien chiao tsho), coupling devices and locks checking mutually (kuan so hsiang chhih)(ie. the escapement). Since (the clock) showed good agreement with the Tao of Heaven, everyone at that time praised its ingenuity. When it was all completed (in +725) it was called the 'Water-Driven Spherical Bird's-Eye-View Map of the Heavens (Shui Yun Hun Thien Fu Shih Thu) or 'Celestial Sphere Model Water-Engine' and was set up in front of the Wu Chheng Hall (of the Palace) to be seen by the multitude of officials. Candidates in the imperial examinationImperial examinationThe Imperial examination was an examination system in Imperial China designed to select the best administrative officials for the state's bureaucracy. This system had a huge influence on both society and culture in Imperial China and was directly responsible for the creation of a class of...
s (in +730) were asked to write an essay on the new armillary (clock). But not very long afterwards the mechanism of bronze and iron began to corrode and rust, so that the instrument could no longer rotate automatically. It was therefore relegated to the (museum of the) College of All Sages (Chi Hsien Yuan) and went out of use.
In his honor
At the TiantaiTiantai
Tiantai is an important school of Buddhism in China, Japan, Korea, and Vietnam. In Japan the school is known as Tendai, and in Korea it is known as Cheontae. Tiantai is also called the "Lotus School", due to its emphasis on the Lotus Sūtra as its doctrinal basis...
-Buddhist Guoqing Temple
Guoqing Temple
The Guoqing Temple is a Buddhist temple on Mount Tiantai, Zhejiang Province, People's Republic of China. Originally built in 598 AD during the Sui Dynasty, and renovated during the reign of the Qing Yongzheng Emperor , the temple is located roughly from the city of Hangzhou...
of Mount Tiantai in Zhejiang
Zhejiang
Zhejiang is an eastern coastal province of the People's Republic of China. The word Zhejiang was the old name of the Qiantang River, which passes through Hangzhou, the provincial capital...
Province, there is a Chinese pagoda
Chinese pagoda
Chinese Pagodas are a traditional part of Chinese architecture. In addition to religious use, since ancient times Chinese pagodas have been praised for the spectacular views which they offer, and many famous poems in Chinese history attest to the joy of scaling pagodas.-History:The pagoda is...
erected directly outside the temple known as the Memorial Pagoda of Monk Yi Xing. His tomb is also located on Mount Tiantai.
See also
- List of Chinese people
- List of inventors
- List of mechanical engineers
- Verge escapementVerge escapementThe verge escapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by advancing the gear train at regular intervals or 'ticks'. Its origin is unknown. Verge escapements were used from the 14th century until about 1800 in clocks...
- Villard de HonnecourtVillard de HonnecourtVillard de Honnecourt was a 13th-century artist from Picardy in northern France. He is known to history only through a surviving portfolio of 33 sheets of parchment containing about 250 drawings dating from the 1220s/1240s, now in the Bibliothèque Nationale, Paris...