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.
...
featured a
liquid-driven escapement
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to ...
, 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
Geodetic astronomy or astronomical geodesy (astro-geodesy) is the application of astronomical methods into geodetic networks and other technical projects of geodesy.
Applications
The most important applications are:
* Establishment of geodetic da ...
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 mon ...
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
arc measurement, i.e., the length of
meridian arc
In geodesy and navigation, a meridian arc is the curve between two points on the Earth's surface having the same longitude. The term may refer either to a segment of the meridian, or to its length.
The purpose of measuring meridian arcs is to ...
-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 ...
— 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 ...
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 ...
— latitude
50°N.
[Hsu, 99.] There were three observations done for each site, one for the height of
polaris
Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris ( Latinized to ''Alpha Ursae Minoris'') and is commonly called the North Star or Pole Star. With an apparent magnitude th ...
, 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, 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, mat ...
(78–139) of the
Han Dynasty
The Han dynasty (, ; ) was an Dynasties in Chinese history, imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Emperor Gaozu of Han, Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by th ...
, 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 Eastern Han dynasty and was followed by the West ...
, and the Daoist Li Lan (c. 450) of the
Southern and Northern Dynasties 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 counte ...
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 bucke ...
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- ...
) in mechanically-driving and rotating his
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
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- ...
), 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, galaxi ...
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 (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, i ...
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).
[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 res ...
(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 E ...
''. This work had a strong influence on the Japanese monk
Kūkai and was key in his establishment of
Shingon Buddhism.
[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 of
Mount Tiantai
Tiantai Mountain (also Tí Taî in the local language) is a mountain in Tiantai County, Taizhou, Zhejiang Province, China. Its highest peak, Huading, reaches a height of . The mountain was made a national park on 1 August 1988. One of nine r ...
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 Ji ...
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.
See also
*
List of Chinese people
*
List of inventors
*
List of mechanical engineers
*
Verge escapement
The verge (or crown wheel) escapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'. Its origin is unknown. V ...
*
Villard de Honnecourt
Villard de Honnecourt (''Wilars dehonecort'', ''Vilars de Honecourt'') was a 13th-century artist from Picardy in northern France. He is known to history only through a surviving portfolio or "sketchbook" containing about 250 drawings and designs ...
Notes
References
*
*Ju, Zan
"Yixing" ''
Encyclopedia of China'' (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