Yu Xi (虞喜; 307–345 AD),

courtesy name A courtesy name ( zh, s=字, p=zì, l=character), also known as a style name, is an additional name bestowed upon individuals at adulthood, complementing their given name. This tradition is prevalent in the East Asian cultural sphere, particula ...

Zhongning (仲寧), was a Chinese astronomer, politician, and writer of the

Jin dynasty Jin may refer to: States Jìn 晉 * Jin (Chinese state) (晉國), major state of the Zhou dynasty, existing from the 11th century BC to 376 BC * Jin dynasty (266–420) (晉朝), also known as Liang Jin and Sima Jin * Jin (Later Tang precursor) ...

(266–420 AD). He is best known for his discovery of the

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...

of the

equinox A solar equinox is a moment in time when the Sun appears directly above the equator, rather than to its north or south. On the day of the equinox, the Sun appears to rise directly east and set directly west. This occurs twice each year, arou ...

es, independently of the earlier ancient Greek astronomer

Hipparchus Hipparchus (; , ; BC) was a Ancient Greek astronomy, Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry, but is most famous for his incidental discovery of the precession of the equinoxes. Hippar ...

. He also postulated that the Earth could be spherical in shape instead of being flat and square, long before the idea became widely accepted in Chinese science with the advances in circumnavigation by Europeans from the 16th-20th centuries, especially with their arrival into the capital's imperial court in the 17th century.

Background and official career

The life and works of Yu Xi are described in his biography found in the ''

Book of Jin The ''Book of Jin'' is an official Chinese historical text covering the history of the Jin dynasty (266–420), Jin dynasty from 266 to 420. It was compiled in 648 by a number of officials commissioned by the imperial court of the Tang dynasty, ...

'', the

official history An official history is a work of history which is sponsored, authorised or endorsed by its subject. The term is most commonly used for histories which are produced for a government. The term also applies to commissions from non-state bodies includi ...

of the Jin dynasty.Knechtges and Chang (2014), p. 2010. He was born in Yuyao, Guiji (modern

Shaoxing Shaoxing is a prefecture-level city on the southern shore of Hangzhou Bay in northeastern Zhejiang province, China. Located on the south bank of the Qiantang River estuary, it borders Ningbo to the east, Taizhou, Zhejiang, Taizhou to the south ...

Zhejiang ) , translit_lang1_type2 = , translit_lang1_info2 = ( Hangzhounese) ( Ningbonese) (Wenzhounese) , image_skyline = 玉甑峰全貌 - panoramio.jpg , image_caption = View of the Yandang Mountains , image_map = Zhejiang i ...

province, China).

Yu Song Yu Song (234 - 280), courtesy name Shilong, was an official of the Jin dynasty of China. He previously served in the state of Eastern Wu during the Three Kingdoms period. He wrote the ''Qiong Tian Lun'' (穹天論), an essay on astronomy. Life ...

, son of

Yu Fan Yu Fan ( zh, t= , , ; 164–233), courtesy name Zhongxiang, was a Chinese essayist, politician, and writer of the state of Eastern Wu during the Three Kingdoms period of China. Initially a minor officer under Wang Lang, the Administrator of ...

, was recorded to be his clan elder. His father Yu Cha (虞察) was a military commander and his younger brother Yu Yu (虞預; fl. 307–329 AD) was likewise a scholar and writer. During the reign of

Emperor Min of Jin Emperor Min of Jin (; 300 – February 7, 318), personal name Sima Ye (司馬鄴 or 司馬業), courtesy name Yanqi (彥旗), was an emperor of the Jin dynasty and the last of the Western Jin. Emperor Min surrendered in 316 to Liu Yao, a gen ...

(r. 313–317 AD) he obtained a low-level position in the administration of the governor of Guiji

commandery In the Middle Ages, a commandery (rarely commandry) was the smallest administrative division of the European landed properties of a military order. It was also the name of the house where the knights of the commandery lived.Anthony Luttrell and G ...

. He declined a series of nominations and promotions thereafter, including a teaching position at the imperial university in 325 AD, an appointment at the imperial court in 333 AD, and the post of cavalier attendant-in-ordinary in 335 AD.

Works

In 336 AD Yu Xi wrote the ''An Tian Lun'' (安天論; ''Discussion of Whether the Heavens Are At Rest'' or ''Disquisition on the Conformation of the Heavens''). In it he described the

of the

es (i.e.

axial precession In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In parti ...

).Needham and Ling (1995), p. 220. He observed that the position of the Sun during the

winter solstice The winter solstice, or hibernal solstice, occurs when either of Earth's geographical pole, poles reaches its maximum axial tilt, tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern Hemisphere, Northern and So ...

had drifted roughly one degree over the course of fifty years relative to the position of the stars.Sun (2017), p. 120. This was the same discovery made earlier by the ancient Greek astronomer

(c. 190–120 BC), who found that the measurements for either the Sun's path around the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

to the vernal equinox or the Sun's relative position to the stars were not equal in length. Yu Xi wrote a critical analysis of the ''huntian'' (渾天) theory of the

celestial sphere In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, ...

, arguing that

the heavens Heaven, or the Heavens, is a common religious cosmological or supernatural place where beings such as deities, angels, souls, saints, or venerated ancestors are said to originate, be enthroned, or reside. According to the beliefs of some r ...

surrounding the earth were infinite and motionless. He advanced the idea that the shape of the Earth was either square or round, but that it had to correspond to the shape of the heavens enveloping it. The ''huntian'' theory, as mentioned by Western Han dynasty astronomer Luoxia Hong (fl. 140–104 BC) and fully described by the Eastern Han dynasty polymath scientist and statesman

Zhang Heng Zhang Heng (; AD 78–139), formerly romanization of Chinese, romanized Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty#Eastern Han (25–220 AD), Eastern Han dynasty. Educated in the capital citi ...

(78–139 AD), insisted that the heavens were spherical and that the Earth was like an egg yolk at its center. Yu Xi's ideas about the infinity of outer space seem to echo Zhang's ideas of endless space even beyond the celestial sphere. Although mainstream Chinese science before European influence in the 17th century surmised that the Earth was flat and square-shaped, some scholars, such as Song dynasty mathematician Li Ye (1192–1279 AD), proposed the idea that it was spherical like the heavens. The acceptance of a spherical Earth can be seen in the

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

and

geographical Geography (from Ancient Greek ; combining 'Earth' and 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding o ...

treatise ''Gezhicao'' (格致草) written in 1648 by Xiong Mingyu (熊明遇).Needham and Ling (1995), p. 499. It rejects the square-Earth theory and, with clear European influence, explains that ships are capable of circumnavigating the globe. However, it explained this using classical Chinese phrases, such as the Earth being as round as a

crossbow A crossbow is a ranged weapon using an Elasticity (physics), elastic launching device consisting of a Bow and arrow, bow-like assembly called a ''prod'', mounted horizontally on a main frame called a ''tiller'', which is hand-held in a similar f ...

bullet, a phrase Zhang Heng had previously used to describe the shape of both the Sun and Moon. Ultimately, though, it was the European

Jesuits in China The history of the missions of the Jesuits in China is part of the history of relations between China and the Western world. The missionary efforts and other work of the Society of Jesus, or Jesuits, between the 16th and 17th century played a si ...

of the 17th century that dispelled the Chinese theory of a flat Earth, convincing the Chinese to adopt the spherical Earth theory established by the ancient Greeks

Anaxagoras Anaxagoras (; , ''Anaxagóras'', 'lord of the assembly'; ) was a Pre-Socratic Greek philosopher. Born in Clazomenae at a time when Asia Minor was under the control of the Persian Empire, Anaxagoras came to Athens. In later life he was charged ...

(c. 500–428 BC),

Philolaus Philolaus (; , ''Philólaos''; ) was a Greek Pythagorean and pre-Socratic philosopher. He was born in a Greek colony in Italy and migrated to Greece. Philolaus has been called one of three most prominent figures in the Pythagorean tradition and ...

(c. 470–385),

Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...

(384–322 BC), and

Eratosthenes Eratosthenes of Cyrene (; ; – ) was an Ancient Greek polymath: a Greek mathematics, mathematician, geographer, poet, astronomer, and music theory, music theorist. He was a man of learning, becoming the chief librarian at the Library of A ...

(c. 276–195 BC).Cullen (1993), pp. 269–270; see also Song and Chen (1996), p. 308. Yu Xi is known to have written commentaries on the various

Chinese classics The Chinese classics or canonical texts are the works of Chinese literature authored prior to the establishment of the imperial Qin dynasty in 221 BC. Prominent examples include the Four Books and Five Classics in the Neo-Confucian traditi ...

. His commentaries and notes were mostly lost before the

Tang dynasty The Tang dynasty (, ; zh, c=唐朝), or the Tang Empire, was an Dynasties of China, imperial dynasty of China that ruled from 618 to 907, with an Wu Zhou, interregnum between 690 and 705. It was preceded by the Sui dynasty and followed ...

, but the fragments preserved in other texts were collected in a single compendium by

Qing-dynasty The Qing dynasty ( ), officially the Great Qing, was a Manchu-led imperial dynasty of China and an early modern empire in East Asia. The last imperial dynasty in Chinese history, the Qing dynasty was preceded by the Ming dynasty and s ...

scholar Ma Guohan (1794–1857).

Citations

References

* Cullen, Christopher. (1993). "Appendix A: A Chinese Eratosthenes of the Flat Earth: a Study of a Fragment of Cosmology in Huainanzi", in Major, John. S. (ed), ''Heaven and Earth in Early Han Thought: Chapters Three, Four, and Five of the Huananzi''. Albany: State University of New York Press. . * Knechtges, David R.; Chang, Taiping. (2014). ''Ancient and Early Medieval Chinese Literature: a Reference Guide'', vol 3. Leiden: Brill. . * Needham, Joseph; Wang, Ling. (1995) 959 ''Science and Civilization in China: Mathematics and the Sciences of the Heavens and the Earth'', vol. 3, reprint edition. Cambridge: Cambridge University Press. . * Song, Zhenghai; Chen, Chuankang. (1996). "Why did Zheng He’s Sea Voyage Fail to Lead the Chinese to Make the ‘Great Geographic Discovery’?" in Fan, Dainian; Cohen, Robert S. (eds), ''Chinese Studies in the History and Philosophy of Science and Technology'', translated by Kathleen Dugan and Jiang Mingshan, pp 303-314. Dordrecht: Kluwer Academic Publishers. . * Sun, Kwok. (2017). ''Our Place in the Universe: Understanding Fundamental Astronomy from Ancient Discoveries'', second edition. Cham, Switzerland: Springer. {{ISBN, 978-3-319-54171-6.

External links

"Yu Xi 虞喜 (fl. 307–46) (Zhongning 仲寧) - Astronome et érudit érémitique des Jin de l'Est" Archives-Ouvertes
(French) 4th-century Chinese astronomers 4th-century Chinese writers 4th-century Confucianists Equinoxes Jin dynasty (266–420) science writers Politicians from Shaoxing Scientists from Shaoxing Writers from Shaoxing

Background and official career

Works

See also

Citations

References

External links