Yi Xing , born
Zhang Sui (张遂), was a
ChineseChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
astronomerAn 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...
,
mathematicianA mathematician is a person whose primary area of study and/or research is the field of mathematics. Mathematicians are concerned with particular problems related to logic, space, transformations, numbers and more general ideas which encompass these concepts...
,
mechanical engineerMechanical Engineering is an engineering discipline that was developed from the application of principles from physics and materials science. Mechanical engineering involves the analysis, design, manufacturing, and maintenance of various systems...
, and Buddhist monk of the
Tang DynastyThe 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
escapementIn mechanical watches and clocks, an escapement is a device which converts continuous rotational motion into an oscillating or back and forth motion....
mechanism, the first in a long tradition of Chinese
astronomical clockworksAn 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:...
.
In the early 8th century, the Tang court put Yi Xing in charge of a
terrestrial-astronomical surveySurveying or land surveying is the technique and science of accurately determining the terrestrial or three-dimensional space 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 eclipseA solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth,...
s.
Yi Xing , born
Zhang Sui (张遂), was a
ChineseChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
astronomerAn 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...
,
mathematicianA mathematician is a person whose primary area of study and/or research is the field of mathematics. Mathematicians are concerned with particular problems related to logic, space, transformations, numbers and more general ideas which encompass these concepts...
,
mechanical engineerMechanical Engineering is an engineering discipline that was developed from the application of principles from physics and materials science. Mechanical engineering involves the analysis, design, manufacturing, and maintenance of various systems...
, and Buddhist monk of the
Tang DynastyThe 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
escapementIn mechanical watches and clocks, an escapement is a device which converts continuous rotational motion into an oscillating or back and forth motion....
mechanism, the first in a long tradition of Chinese
astronomical clockworksAn 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:...
.
Terrestrial-astronomical survey
In the early 8th century, the Tang court put Yi Xing in charge of a
terrestrial-astronomical surveySurveying or land surveying is the technique and science of accurately determining the terrestrial or three-dimensional space 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 eclipseA solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth,...
s. The survey was also initiated so that flaws in the
calendar systemThe Chinese calendar is lunisolar, 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. It is often referred to as the Chinese calendar because it was first perfected by the Chinese around 500 BCE...
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 a portion of the
meridian-Earth science:* Meridian , imaginary circle perpendicular to the celestial equator and horizon* Meridian , an imaginary arc on the Earth's surface from the North Pole to the South Pole-United States geography:* Meridian, California...
. 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
EratosthenesEratosthenes of Cyrene was a Greek mathematician, elegiac poet, athlete, geographer, and astronomer. He made several discoveries and inventions including a system of latitude and longitude...
(276–196 BC).
Yi Xing had thirteen test sites established throughout the empire, extending from
JiaozhouJiaozhou is a county-level city of Qingdao sub-provincial city, Shandong Province, China....
in
VietnamVietnam , 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 to the east...
— at
latitudeLatitude, usually denoted by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the imaginary horizontal lines shown running east-to-west on maps that run either north or south of the equator...
17°NThe 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 BaikalLake Baikal is the world's second most voluminous lake, after the Caspian Sea. It is the most voluminous freshwater lake in the world with an average depth of 744.4 m and contains a total of roughly 20 percent of the world's surface fresh water...
— latitude
50°NThe 50th parallel north is a circle of latitude that is 50 degrees north of the Earth's equatorial plane.Starting at the Prime Meridian and heading eastwards, the parallel 50° north passes through:-Karafuto:...
. There were three observations done for each site, one for the height of
polarisPolaris 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.Polaris is about 430 light-years from Earth...
, 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 was a Tang Dynasty military engineer and government official of the Kaiyuan era who 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
escapementIn mechanical watches and clocks, an escapement is a device which converts continuous rotational motion into an oscillating or back and forth motion....
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 HengZhang Heng was an astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar from Nanyang, Henan, and 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 minor...
(78–139) of the
Han DynastyThe 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 peasant 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 JunMa Jun , styled Deheng , was a Chinese mechanical engineer and government official during the Three Kingdoms era of China...
(200–265) of the
Three KingdomsThe Three Kingdoms period is a period in the history of China, part of an era of disunity called the Six Dynasties following immediately the loss of de facto power of the Han Dynasty emperors. In a strict academic sense it refers to the period between the foundation of the Wei in 220 and the...
, and the Daoist Li Lan (c. 450) of the
Southern and Northern DynastiesThe Southern and Northern Dynasties following the Jin Dynasty and followed by the Sui Dynasty in China. It was an age of civil war and political disunity. However it was also a time of flourishing in the arts and culture, advancement in technology, and the spread of foreign Mahayana Buddhism and...
period.
It was the earlier Chinese inventor Zhang Heng who was the first to apply hydraulic power (ie. a waterwheel and
clepsydraClepsydra may refer to*Clepsydra , the Greek word for water clock.* Clepsydra Geyser in the Lower Geyser Basin of Yellowstone*Clepsydra, a genus of protists....
) in mechanically-driving and rotating his
equatorialEquatorial has different meanings:* In geography it relates to the equator of the Earth.* In meteorology, an Equatorial climate is the type of climate experienced near the equator....
armillary sphereAn armillary sphere is a model of the celestial sphere.- Description and use of the armillary sphere :This section refers to labels in the diagram below....
). The arrangement followed the model of a water-wheel using the drip of a clepsydra (see
water clockA 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 being...
), 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 towerA clock tower is a tower built with one or more clock faces. The clock tower is usually part of a church or municipal building such as a town hall, but many clock towers are free-standing....
engineered and erected by
Su SongSu Song was a renowned Chinese 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 water-driven astronomical clock tower in...
(1020–1101), Yi Xing's celestial globe employed water-power in order for it to rotate and function properly. The historian
Joseph NeedhamNoel Joseph Terence Montgomery Needham, CH, FRS, FBA , also known as Li Yuese , was a British academic and sinologist known for his research and writing on the history of Chinese science. He was elected a fellow of the Royal Society in 1941; and he was elected a fellow of the British Academy in 1971...
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 SixunZhang 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 DynastyThe 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 examinationThe Imperial examinations in Imperial China determined who among the population would be permitted to enter the state's bureaucracy. The Imperial Examination System in China lasted for 1300 years, from its founding during the Sui Dynasty in 605 to its abolition near the end of the Qing Dynasty in...
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 is one of the important schools of Buddhism in China, Korea and Japan, also called the Lotus School because of its emphasis on the Lotus Sutra. It was founded by Zhiyi during the Sui Dynasty in China...
-Buddhist
Guoqing TempleThe Guoqing Temple of Tiantai Mountain, Zhejiang province, China is a Buddhist temple originally built in 598 AD during the Sui Dynasty, and renovated during the reign of the Yongzheng Emperor of the Qing Dynasty. It is located roughly 220 km from the city of Hangzhou...
of
Tiantai MountainTiantai Mountain is in Tiantai County in Zhejiang Province in China, near the city of Taizhou. The mountain was made a national park on August 01, 1988. The Gouqing-si temple on the mountain is the headquarters of the Tiantai sect of Buddhism and also a tourist destination.Tiantai Buddhism, named...
in
ZhejiangZhejiang 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 pagodaChinese Pagodas are a traditional part of Chinese architecture, and is evolved from the stupa from the Indian subcontinent. 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...
erected directly outside of the temple, known as the Memorial Pagoda of Monk Yi Xing. His tomb is also located at Tiantai Mountain.
See also
- List of Chinese people
- List of inventors
- List of mechanical engineers
- Verge escapement
The 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 Honnecourt
Villard de Honnecourt lived in 13th century France and may have been an itinerant master-builder of Picardy in northern France. His fame rests entirely on his surviving portfolio of 33 sheets of parchment containing about 250 drawings from about the 1230s, which is in the Bibliothèque Nationale,...
External links