Eight Patriarchs of the Shingon Sect of Buddhism I Hsing Cropped

Yi Xing (, 683–727), born Zhang Sui (), was a Chinese astronomer, Buddhist monk, inventor, mathematician, mechanical engineer, and philosopher during the Tang dynasty. His astronomical

celestial globe Celestial globes show the apparent positions of the stars in the sky. They omit the Sun, Moon, and planets because the positions of these bodies vary relative to those of the stars, but the ecliptic, along which the Sun moves, is indicated. Th ...

featured a liquid-driven escapement, the first in a long tradition of Chinese

astronomical clock An astronomical clock, horologium, or orloj 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.

Science and technology

Astrogeodetic survey

In the early 8th century, the Tang court put Yi Xing in charge of an astrogeodetic survey.Hsu, 98. This survey had many purposes. It was established in order to obtain new astronomical data that would aid in the prediction of

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six month ...

s. The survey was also initiated so that flaws in the

calendar system A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A calendar date, date is the designation of a single and specific day within such a system. A calendar is ...

could be corrected and a new, updated calendar installed in its place. The survey was also essential in determining the

arc measurement Arc measurement, sometimes degree measurement (german: Gradmessung), is the astrogeodetic technique of determining of the radius of Earth – more specifically, the local Earth radius of curvature of the figure of the Earth – by relating the la ...

, i.e., the length of meridian arc-although Yi Xing, who did not know the Earth was spherical, did not conceptualize his measurements in these terms. 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. Yi Xing had thirteen test sites established throughout the empire, extending from Jiaozhou in

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

— at

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

17°N — to the region immediately south of

Lake Baikal Lake Baikal (, russian: Oзеро Байкал, Ozero Baykal ); mn, Байгал нуур, Baigal nuur) is a rift lake in Russia. It is situated in southern Siberia, between the federal subjects of Irkutsk Oblast to the northwest and the Repu ...

— latitude 50°N.Hsu, 99. 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 determined 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 as he had difficulties expressing the number). He, along with his associate, the mechanical engineer and politician

Liang Lingzan Liang Lingzan () was a Chinese artist, astronomer, inventor, mechanical engineer and politician of the Kaiyuan era during the Tang Dynasty. He invented a mechanized water clock with the Tantric monk and mathematician Yi Xing (). It was actually an ...

, is best known for applying the earliest-known escapement mechanism to a water-powered celestial globe. However, Yi Xing's mechanical 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 (; AD 78–139), formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, ma ...

(78–139) of the

Han Dynasty The Han dynasty (, ; ) was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–207 BC) and a warr ...

, the mechanical engineer Ma Jun (200–265) of the

Three Kingdoms The Three Kingdoms () from 220 to 280 AD was the tripartite division of China among the dynastic states of Cao Wei, Shu Han, and Eastern Wu. The Three Kingdoms period was preceded by the Han dynasty#Eastern Han, Eastern Han dynasty and wa ...

, and the Daoist Li Lan (c. 450) of the

Southern and Northern Dynasties The Northern and Southern dynasties () was a period of political division in the history of China that lasted from 420 to 589, following the tumultuous era of the Sixteen Kingdoms and the Eastern Jin dynasty. It is sometimes considered as ...

period. It was the earlier Chinese inventor Zhang Heng during the Han dynasty who was the first to apply

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

power (i.e. a

waterwheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...

and

water clock A water clock or clepsydra (; ; ) is a timepiece by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the amount is then measured. Water clocks are one of the oldest time-m ...

) in mechanically-driving and rotating his

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

armillary sphere An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of ...

. The arrangement followed the model of a water-wheel using the drip of a clepsydra (see

), which ultimately exerted force on a lug to rotate toothed-gears on a polar-axis shaft.Needham, Volume 4, 532. 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 Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies ...

clock tower Clock towers are a specific type of structure which house a turret clock and have one or more clock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another buildi ...

engineered and erected by

Su Song Su Song (, 1020–1101), courtesy name Zirong (), was a Chinese polymathic scientist and statesman. Excelling in a variety of fields, he was accomplished in mathematics, Chinese astronomy, astronomy, History of cartography#China, cartography, ...

(1020–1101), Yi Xing's celestial globe employed water-power in order for it to rotate and function properly.Needham, Volume 4, 470. The British biochemist, historian, and sinologist

Joseph Needham Noel Joseph Terence Montgomery Needham (; 9 December 1900 – 24 March 1995) was a British biochemist, historian of science and sinologist known for his scientific research and writing on the history of Chinese science and technology, in ...

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 Zhang Sixun (, fl. 10th century) was a Chinese astronomer and mechanical engineer from Bazhong, Sichuan during the early Song Dynasty (960–1279 AD).Liu, 577. He is credited with creating an armillary sphere for his astronomical clock tower that ...

in 979 AD (because mercury would not freeze during winter).Needham, Volume 3, 350.Needham, Volume 4, 471. During his age, the

Song dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the rest ...

(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 (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 scholarship

Yi Xing wrote a commentary on the ''

Mahavairocana Tantra Vairocana (also Mahāvairocana, sa, वैरोचन) is a cosmic buddha from Mahayana and Vajrayana Buddhism. Vairocana is often interpreted, in texts like the '' Avatamsaka Sutra'', as the dharmakāya of the historical Gautama Buddha. In Eas ...

''. This work had a strong influence on the Japanese monk

Kūkai Kūkai (; 27 July 774 – 22 April 835Kūkai was born in 774, the 5th year of the Hōki era; his exact date of birth was designated as the fifteenth day of the sixth month of the Japanese lunar calendar, some 400 years later, by the Shingon sec ...

and was key in his establishment of

Shingon Buddhism Shingon monks at Mount Koya is one of the major schools of Buddhism in Japan and one of the few surviving Vajrayana lineages in East Asia, originally spread from India to China through traveling monks such as Vajrabodhi and Amoghavajra. K ...

.Rethinking Japan p.330

In his honor

At the

Tiantai Tiantai or T'ien-t'ai () is an East Asian Buddhist school of Mahāyāna Buddhism that developed in 6th-century China. The school emphasizes the ''Lotus Sutra's'' doctrine of the "One Vehicle" (''Ekayāna'') as well as Mādhyamaka philosophy ...

-Buddhist

Guoqing Temple The Guoqing Temple () is a Buddhist temple on Mount Tiantai, in Taizhou, Zhejiang Province, China. Originally built in 598 CE during the Sui dynasty, and renovated during the reign of the Qing Yongzheng Emperor (r. 1722–1735), the temple is lo ...

of Mount Tiantai in

Zhejiang Zhejiang ( or , ; , also romanized as Chekiang) is an eastern, coastal province of the People's Republic of China. Its capital and largest city is Hangzhou, and other notable cities include Ningbo and Wenzhou. Zhejiang is bordered by Jiang ...

Province, there is a

Chinese pagoda A pagoda is an Asian tiered tower with multiple eaves common to Nepal, India, China, Japan, Korea, Myanmar, Vietnam, and other parts of Asia. Most pagodas were built to have a religious function, most often Buddhist but sometimes Taoist, ...

erected directly outside the temple known as the Memorial Pagoda of Monk Yi Xing. His tomb is also located on Mount Tiantai.

Notes

References

* *Ju, Zan
"Yixing"
''

Encyclopedia of China The ''Encyclopedia of China'' () is the first large-entry modern encyclopedia in the Chinese language. The compilation began in 1978. Published by the Encyclopedia of China Publishing House, the encyclopedia was issued one volume at a time, begin ...

'' (Religion Edition), 1st ed. *Needham, Joseph (1986). ''Science and Civilization in China: Volume 3''. Taipei: Caves Books, Ltd. *Needham, Joseph (1986). ''Science and Civilization in China: Volume 4, Part 2''. Taipei: Caves Books, Ltd. *Boscaro, Adriana (2003) ''Rethinking Japan: Social Sciences, Ideology and Thought''. Routledge. 0-904404-79-x p. 330

External links

Yi Xing at Chinaculture.org
{{DEFAULTSORT:Yi, Xing 683 births 727 deaths 8th-century Buddhists 8th-century Buddhist monks 8th-century Chinese astronomers 8th-century Chinese writers 8th-century engineers 8th-century inventors category:8th-century mathematicians Chinese inventors Chinese mechanical engineers Chinese scholars of Buddhism Engineers from Henan Hydraulic engineers Mathematicians from Henan Medieval Chinese mathematicians Philosophers from Henan Tang dynasty Buddhist monks Tang dynasty philosophers Writers from Puyang