# List of Chinese discoveries

Aside from many original inventions, the Chinese were also early original pioneers in the discovery of natural phenomena which can be found in the human body, the environment of the world, and the immediate solar system. They also discovered many concepts in mathematics. The list below contains discoveries which found their origins in China.

## Discoveries

### Ancient and imperial era

Han Dynasty (202 BC – 220 AD) paintings on tile of Chinese guardian spirits representing 11 pm to 1 am (left) and 5 am to 7 am (right); the ancient Chinese, although discussing it in supernatural terms, acknowledged circadian rhythm within the human body
• Chinese remainder theorem: The Chinese remainder theorem, including simultaneous congruences in number theory, was first created in the 3rd century AD by the mathematician Sunzi, whose Mathematical Classic by Sun Zi (孙子算经, Sunzi suanjing) posed the problem: "There is an unknown number of things, when divided by 3 it leaves 2, when divided by 5 it leaves 3, and when divided by 7 it leaves a remainder of 2. Find the number."[1] This method of calculation was used in calendrical mathematics by Tang Dynasty (618–907) mathematicians such as Li Chunfeng (602–670) and Yi Xing (683–727) in order to determine the length of the "Great Epoch", the lapse of time between the conjunctions of the moon, sun, and Five Planets (those discerned by the naked eye).[1] Thus, it was strongly associated with the divination methods of the ancient Yijing.[1] Its use was lost for centuries until Qin Jiushao (c. 1202–1261) revived it in his Mathematical Treatise in Nine Sections of 1247, providing constructive proof for it.[1]
• Circadian rhythm in humans: The Huangdi Neijing, compiled by the 2nd century BC during the Han Dynasty (202 BC – 220 AD), noted the symptoms, behavior, and reactions of people with different diseases (i.e. of the liver, heart, spleen, lung, or kidneys) during different times of a 24-hour day.[2] The idea of any organism following a daily circadian rhythm was not accepted in mainstream modern medical science even up until the 1960s, yet it is now well established that patients with Parkinson's disease lose much of their debilitating symptoms between 9 pm and midnight, while paroxysms of patients with asthma usually occur at night when secretion of hormones from the cortexes of the adrenal glands falls to a minimum.[3] Although the ancient Chinese explained symptoms of diseased patients that followed the pattern of their circadian rhythms in terms of superstitious numerology and cyclic lore, they still documented such cases and expounded on them long before anyone else.[4] The observation of a circadian or diurnal process in humans is mentioned in Chinese medical texts dated to around the 13th century, including the Noon and Midnight Manual and the Mnemonic Rhyme to Aid in the Selection of Acu-points According to the Diurnal Cycle, the Day of the Month and the Season of the Year.[5]
• Decimal fractions: As proven by inscriptions from the 13th century BC, the decimal system existed in China since the Shang Dynasty (c. 1600–c. 1050 BC).[6] The earliest evidence of a decimal fraction, where the fraction's denominator is a power of ten, appears on an inscription of a standard measure of volume used by the mathematician and astronomer Liu Xin (c. 46 BC–23 AD), dated precisely 5 AD.[7] The first significant piece of Chinese literature to feature decimal fractions was The Nine Chapters on the Mathematical Art.[8] This text was first mentioned in 179 AD,[9] although Liu Hui (fl. 3rd century AD) asserts that some of its material predates the infamous Qin book burning in 213 BC (i.e. older than the oldest surviving Chinese mathematical treatise, the Book on Numbers and Computation, 202–186 BC).[10] Liu Hui used decimal fractions with measurements and as solutions to equations.[8] At first decimal fractions were written in word form, since it was Han Yan (fl. late 8th century) of the Tang Dynasty (607–907) who first used modern decimal notation to write out decimal fractions.[8] Decimal fractions were vital to the work of Song (960–1279) mathematicians such as Yang Hui (1238–1298) and Qin Jiushao (c. 1201–1261).[8] Jamshīd al-Kāshī (1380–1429), director of the astronomical observatory at Samarkand, adopted the use of decimal fractions; they were first mentioned in Europe by Christoff Rudolff of Augsburg in his Exempel-Buechlin of 1530, yet not given serious attention until the 1585 work of the Flemish mathematician Simon Stevin (1548–1620).[8]
The frontispiece to Hu Sihui's Principles of Correct Diet published in 1330 (Yuan Dynasty); the caption reads "Many diseases can be cured by diet alone," a belief which spanned back to at least the 3rd century AD in China.[11]
• Deficiency diseases, correction by proper diet: As early as the 4th century BC, Warring States period (403–221 BC), records indicate that Imperial Dieticians were appointed at royal courts.[11] The first explicit description of a regulated diet used to curb certain diseases is found in the Systematic Treasury of Medicine written by Zhang Zhongjing (c. 150 – c. 219) during the late Han Dynasty.[11] Although Zhang did not understand the true nature of vitamins, he prescribed foods now known to be rich in certain vitamins, which were discovered to be useful after much trial and error.[11] The Yuan Dynasty (1271–1368) physician and Imperial Dietician Hu Sihui (fl. 1314–1330) published his book Principles of Correct Diet which compiled a large amount of previous material written on the subject.[11]
• Diabetes, recognition and treatment of: The Huangdi Neijing compiled by the 2nd century BC during the Han Dynasty identified diabetes as a disease suffered by those who had made an excessive habit of eating sweet and fatty foods, while the Old and New Tried and Tested Perscriptions written by the Tang Dynasty physician Zhen Quan (died 643) was the first known book to mention an excess of sugar in the urine of diabetic patients.[12][13] While his book is now lost, quotations of it were preserved in the Important Medical Formulae and Prescriptions Now Revealed by the Governor of a Distant Province, written by Wang Tao in 752.[12] The Tang physician Sun Simiao (581–682) wrote in his Thousand Golden Remedies of 655 that for diabetic patients "three things must be renounced, wine, sex, and eating salted, starchy cereal products; if this regimen can be observed, cure may follow without drugs."[14] Robert Temple writes that this is similar to the modern method of avoiding alcohol and starchy foods.[14] The sweetness of urine in diabetic patients is also noted in an ancient text of India, but unlike the Chinese texts its date is ambiguous.[14]
• Endocrinology, isolation of sex and pituitary hormones from urine: In 1110, a Chinese medical text specified the use of gypsum (containing calcium sulfate) as well as saponin from the beans of Gleditschia sinensis to extract hormones from urine, a process of using natural soaps which was not discovered elsewhere until the use of digitonin by Adolf Windaus (1876–1959) in 1909.[15] In 1927, Selmar Ascheim (1878–1965) and Bernhard Zondek (1891–1966) discovered that urine of pregnant women had a high concentration of steroid sex hormones; a subsequent discovery was made that urine contained sex hormones of androgens and estrogens, as well as the pituitary hormone gonadotrophin.[16] In modern medicine, the extraction of these hormones from urine is a standard practice, yet centuries before this the Chinese had used it to treat hypogonadism, impotence, spermatorrhea, dysmenorrhea, leukorrhea, and even stimulating the growth of beards (since they knew that castration resulted in the loss of ability to grow a beard).[17]
Each bronze bell of Marquis Yi of Zeng (433 BC) bears an inscription describing the specific note it plays, its position on a 12-note scale, and how this scale differed from scales used by other Chinese states of the time; before this discovery in 1978,[18] the oldest known surviving Chinese tuning set came from a 3rd-century BC text (which alleges was written by Guan Zhong, d. 645 BC) with five tones and additions or subtractions of ⅓ of successive tone values which produce the rising fourths and falling fifths of Pythagorean tuning.[19]
• Equal temperament: During the Han Dynasty (202 BC–220 AD), the music theorist and mathematician Jing Fang (78–37 BC) extended the 12 tones found in the 2nd century BC Huainanzi to 60.[20] While generating his 60-divisional tuning, he discovered that 53 just fifths is approximate to 31 octaves, calculating the difference at $\tfrac{177147}{176776}$; this was exactly the same value for 53 equal temperament calculated by the German mathematician Nicholas Mercator (c. 1620–1687) as 353/284, a value known as Mercator's Comma.[21][22] The Ming Dynasty (1368–1644) music theorist Zhu Zaiyu (1536–1611) elaborated in three separate works beginning in 1584 the tuning system of equal temperament; in an unusual event in music theory's history, the Flemish mathematician Simon Stevin (1548–1620) discovered the mathematical formula for equal temperament at roughly the same time (within 1 to 25 years of Zhu), yet he did not publish his work and it remained unknown until 1884; therefore, it is debatable who discovered equal temperament first, Zhu or Stevin.[23][24][25] In order to obtain equal intervals, Zhu divided the octave (each octave with a ratio of 1:2, which can also be expressed as 1:212/12) into twelve equal semitones while each length was divided by the 12th root of 2.[26] He did not simply divide the string into twelve equal parts (i.e. 11/12, 10/12, 9/12, etc.) since this would give unequal temperament; instead, he altered the ratio of each semitone by an equal amount (i.e. 1:2 11/12, 1:210/12, 1:29/12, etc.) and determined the exact length of the string by dividing it by 122 (same as 21/12).[26] The Harmonie Universelle (1636) written by Marin Mersenne (1588–1648) was the first publication in Europe outlining equal temperament, a new system of tuning that was passionately defended by J.S. Bach (1685–1750) in his Well-Tempered Clavier of 1722.[25]
• First law of motion, partial description: The Mohist philosophical canon of the Mojing, compiled by the followers of Mozi (c. 470 – c. 390 BC), provides the earliest known attempt to describe inertia: "The cessation of motion is due to the opposing force...If there is no opposing force...the motion will never stop. This is as true as that an ox is not a horse."[27] However, like many of the Hundred Schools of Thought during the Warring States period (403–221 BC), the doctrine of the Mohist sect had little impact on the course of later Chinese thought, while this passage and others from the Mojing were only given serious attention by modern scholarship after the work of Joseph Needham in 1962.[27]
• Gaussian elimination: First published in the West by Carl Friedrich Gauss (1777–1855) in 1826, the algorithm for solving linear equations known as Gaussian elimination is named after this Hanoverian mathematician, yet it was first expressed as the Array Rule in the Chinese Nine Chapters on the Mathematical Art, written at most by 179 AD during the Han Dynasty (202 BC–220 AD) and commented on by the 3rd century mathematician Liu Hui.[28][29][30]
Aware of underground minerals associated with certain plants by at least the 5th century BC, the Chinese extracted trace elements of copper from Oxalis corniculata, pictured here, as written in the 1421 text Precious Secrets of the Realm of the King of Xin.
Bamboo and rocks by Li Kan (1244–1320); using evidence of fossilized bamboo found in a dry northern climate zone, Shen Kuo hypothesized that climates naturally shifted geographically over time.
• Geomorphology: In his Dream Pool Essays of 1088, Shen Kuo (1031–1095) wrote about a landslide (near modern Yan'an) where petrified bamboos were discovered in a preserved state underground, in the dry northern climate zone of Shanbei, Shaanxi; Shen reasoned that since bamboo was known only to grow in damp and humid conditions, the climate of this northern region must have been different in the very distant past, postulating that climate change occurred over time.[33][34] Shen also advocated a hypothesis in line with geomorphology after he observed a stratum of marine fossils running in a horizontal span across a cliff of the Taihang Mountains, leading him to believe that it was once the location of an ancient shoreline that had shifted hundreds of km (mi) east over time (due to deposition of silt and other factors).[35][36]
• Horner scheme: Although named after English mathematician William George Horner (1786–1837), the Horner scheme, an algorithm used to estimate the root of an equation and evaluate polynomials in monomial form, was actually first invented in China to find the cube root of the number 1,860,867 (the answer given being 123).[37] This is found in the Han Dynasty (202 BC–220 AD) work The Nine Chapters on the Mathematical Art, commented on by Liu Hui (fl. 3rd century) in 263 AD.[37] The original Nine Chapters found the root of equations through continued fractions, just like the later Italian mathematician Joseph Louis Lagrange (1736–1813), while Liu Hui achieved this by increasing decimals, just like William George Horner in his work of 1819.[37]
• Jia Xian triangle: This triangle was the same as Pascal's Triangle, discovered by Jia Xian in the first half of the 11th century, about six centuries before Pascal. Jia Xian used it as a tool for extracting square and cubic roots. The original book by Jia Xian titled Shi Suo Suan Shu was lost; however, Jia's method was expounded in detail by Yang Hui, who explicitly acknowledged his source: "My method of finding square and cubic roots was based on the Jia Xian method in Shi Suo Suan Shu."[38] A page from the Yongle Encyclopedia preserved this historic fact.
Mohandas Karamchand Gandhi tends to a leper; the Chinese were the first to describe the symptoms of leprosy.
Iron plate with an order 6 magic square in Arabic numbers from China, dating to the Yuan Dynasty (1271-1368).
With the description in Han Ying's written work of 135 BC (Han Dynasty), the Chinese were the first to observe that snowflakes had a hexagonal structure.
Oiled garments left in the tomb of Emperor Zhenzong of Song (r. 997–1022), pictured here in this portrait, caught fire seemingly at random, a case which a 13th-century author related back to the spontaneous combustion described by Zhang Hua (232–300) around 290 AD
• Snowflake, observation of its hexagonal structure: In his Moral Discourses Illustrating the Han Text of the Book of Songs of 135 BC, the Han Dynasty (202 BC– 220 AD) author Han Ying wrote: "Flowers of plants and trees are generally five-pointed, but those of snow, which are called ying, are always six pointed."[56] This was the first explicit reference in world history to the hexagonal structure of snowflakes.[56] From then on, Chinese writers throughout the centuries mentioned the hexagonal structure of snowflakes, including the crown prince and poet Xiao Tong (501–531) and the Neo-Confucian philosopher Zhu Xi (1130–1200).[56] In contrast to Western ideas of snowflakes, Olaus Magnus (1490–1557) wrote in his A Description of the Northern Peoples in 1555 that snowflakes could take on many shapes, including crescents, arrows, nails, bells, and even the shape of the human hand.[27] It was not until 1591 that Thomas Hariot (1560–1621) recognized the snowflake's hexagonal structure, but he did not publish his jotted private notes on the subject.[27] Finally, the astronomer Johannes Kepler (1571–1630) wrote the first known European publication on the subject in 1611, the fifteen-page A New Year's Gift, or On the Six-Cornered Snowflake.[56]
• Solar wind, observation of via comet tails: In the Book of Jin compiled during the Tang Dynasty (618–907), a passage written in 635 AD states: "In general, when a comet appears in the morning, its tail points towards the west, and when it appears in the evening, its tail points towards the east. This is a constant rule. If the comet is north or south of the Sun, its tail always points following the same direction as the light radiating from the Sun."[57] In other words, as Robert Temple states, "the Chinese observations of comet tails had been refined enough to establish the principle that comet tails always point away from the sun."[57] Furthermore, the text reveals that astronomers by at least the Tang Dynasty understood that, like the Moon, the light shining from a comet was merely reflected sunlight;[57] from the writings of Jing Fang (78–37 BC), Wang Chong (27–100), Zhang Heng (78–139), and others it is apparent that the Chinese already by the Han Dynasty (202 BC – 220 AD) understood that the Moon was illuminated solely by the Sun's rays of light.[58] Although the Chinese explained this constant rule about comets in terms of supernatural qi, it is now understood in modern astronomy as the concept of 'solar wind', where the powerful force of radiation from the Sun causes comets to turn away from it.[57]
• Spontaneous combustion, recognition of: In his Record of Strange Things written sometime before 290 AD, the Jin Dynasty official and poet Zhang Hua (232–300) wrote the earliest known account acknowledging spontaneous combustion: "If ten thousand piculs of oil are accumulated in store, the oil will ignite itself spontaneously. The calamitous fire which occurred in the arsenal of the time of the Emperor Wu [of the Jin Dynasty] in the Taishi reign-period [265–74 AD] was caused by the stored oil."[59] There were other mentionings of spontaneous combustion in early Chinese literary works, while more often than not fires were blamed on arsonists.[60] The 13th-century work Parallel Cases Solved by Eminent Judges recounts an event in 1050 where imperial guards were charged in a court of law with the crime of allowing a fire to spread in the palace at Kaifeng; their sentence was commuted from the death penalty to a light punishment when artisans confessed that the chemical-enhanced (perhaps quicklime) oily curtains they made had the propensity to catch fire spontaneously when left out in the open, a statement which convinced Emperor Renzong (r. 1022–1063) since a random fire had recently started in oiled garments of Emperor Zhenzong's (r. 997–1022) mausoluem.[60] The author of Parallel Cases Solved by Eminent Judges noted that Zhang Hua had once believed oil stored in an arsenal spontaneously combusted, yet he concludes that what happened in that ancient arsenal was most likely the result of oiled garments, not just oil by itself.[60] The first acknowledgement of spontaneous combustion anywhere else in the world was made by J. P. F. Duhamel in a French scientific paper published in 1757, in which he described oiled canvas sails catching fire after being left out in the summer sun for only a few hours.[60]
• Sunspots, recognition of as solar phenomena: The astronomer Gan De (fl. 4th century BC) from the State of Qi during the Warring States period (403–221 BC) was the first known writer to attribute sunspots as characteristics of the sun and true solar phenomena.[61] The next known recording of a sunspot in China was in 165 BC, yet the first precisely dated sunspot observed from China occurred on May 10, 28 BC, during the Han Dynasty (202 BC – 220 AD).[61] From 28 BC to 1368 AD, a total of 112 other instances of sunspots were recorded by the Chinese.[62] In the West, from the time of Aristotle (384–322 BC) of ancient Greece to the time of Galileo Galilei (1564–1642), it was commonly believed that the heavens were perfect, including the sun.[61] After the first written observation in the West of sunpots by Einhard (d. 840) in his Life of Charlemagne in 807 AD, the sun's periodic blemishes were explained by Western thinkers as being small invisible satellites or transits of Mercury and Venus; it was only in the 17th century that these beliefs were overturned.[63]
• True north, concept of: The Song Dynasty (960–1279) official Shen Kuo (1031–1095), alongside his colleague Wei Pu, improved the orifice width of the sighting tube to make nightly accurate records of the paths of the moon, stars, and planets in the night sky, for a continuum of five years.[64] By doing so, Shen fixed the outdated position of the pole star, which had shifted over the centuries since the time Zu Geng (fl. 5th century) had plotted it; this was due to the precession of the Earth's rotational axis.[65][66] When making the first known experiments with a magnetic compass, Shen Kuo wrote that the needle always pointed slightly east rather than due south, an angle he measured which is now known as magnetic declination, and wrote that the compass needle in fact pointed towards the magnetic north pole instead of true north (indicated by the current pole star); this was a critical step in the history of accurate navigation with a compass.[67][68][69]

## Notes

1. Chern later acquired American citizenship in 1961. He was born in Jiaxing, Zhejiang.
2. Yang later acquired American citizenship in 1964, Lee in 1962. Both men were born in China.

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