The history of science and technology in China is both long and rich with many contributions to science and technology. In antiquity, independently of Greek philosophers and other civilizations, ancient Chinese philosophers made significant advances in science, technology, mathematics, and astronomy. The first recorded observations of comets, solar eclipses, and supernovae were made in China. Traditional Chinese medicine, acupuncture and herbal medicine were also practiced.
Among the earliest inventions were the abacus, the "shadow clock," and the first flying machines such as kites and Kongming lanterns. The four Great Inventions of ancient China: the compass, gunpowder, papermaking, and printing, were among the most important technological advances, only known in Europe by the end of the Middle Ages. The Tang Dynasty (AD 618 - 906) in particular, was a time of great innovation. A good deal of exchange occurred between Western and Chinese discoveries up to the Qing Dynasty.
The Chinese invented technologies involving mechanics, hydraulics, and mathematics applied to horology, metallurgy, astronomy, agriculture, engineering, music theory, craftsmanship, nautics, and warfare. By the Warring States Period (403–221 BC), they had advanced metallurgic technology, including the blast furnace and cupola furnace, while the finery forge and puddling process were known by the Han Dynasty (202 BC – AD 220). A sophisticated economic system in China gave birth to inventions such as paper money during the Song Dynasty (960–1279). The invention of gunpowder by the 10th century led to an array of inventions such as the fire lance, land mine, naval mine, hand cannon, exploding cannonballs, multistage rocket, and rocket bombs with aerodynamic wings and explosive payloads. With the navigational aid of the 11th-century compass and ability to steer at high sea with the 1st-century sternpost rudder, premodern Chinese sailors sailed as far as East Africa and Egypt. In water-powered clockworks, the premodern Chinese had used the escapement mechanism since the 8th century and the endless power-transmitting chain drive in the 11th century. They also made large mechanical puppet theaters driven by waterwheels and carriage wheels and wine-serving automatons driven by paddle wheel boats.
The contemporaneous Peiligang and Pengtoushan cultures represent the oldest Neolithic cultures of China and were formed around 7000 BC.[4] Some of the first inventions of Neolithic, prehistoric China include semilunar and rectangular stone knives, stone hoes and spades, the cultivation of millet, rice and the soybean, the refinement of sericulture, the building of rammed earth structures with lime-plastered house floors, the creation of the potter's wheel, the creation of pottery with cord-mat-basket designs, the creation of pottery tripods and pottery steamers, and the development of ceremonial vessels and scapulimancy for purposes of divination. Francesca Bray argues that the domestication of the ox and buffalo during the Longshan culture (c. 3000–c. 2000 BC) period, the absence of Longshan-era irrigation or high-yield crops, full evidence of Longshan cultivation of dry-land cereal crops which gave high yields "only when the soil was carefully cultivated," suggest that the plow was known at least by the Longshan culture period and explains the high agricultural production yields which allowed the rise of Chinese civilization during the Shang Dynasty (c. 1600–c. 1050 BC). With later inventions such as the multiple-tube seed drill and heavy moldboard iron plow, China's agricultural output could sustain a much larger population.
Four Great Inventions
The following is a list of the Four Great Inventions of ancient China—as designated by Joseph Needham (1900–1995), a sinologist known for his research on the history of Chinese science—in the chronological order that they were established in China.
Fragments of hemp wrapping paper dated to the reign of Emperor Wu of Han (141–87 BC)
The Diamond Sutra, the oldest printed book, published in AD 868 during the Tang Dynasty (618–907)
Paper
Although it is recorded that the Han Dynasty (202 BC–AD 220) court eunuch Cai Lun (b.c.50–AD 121) invented the pulp papermaking process and established the use of new raw materials used in making paper, ancient padding and wrapping paper artifacts dating to the 2nd century BC have been found in China, the oldest example of pulp papermaking being a map from Fangmatan, Tianshui; by the 3rd century, paper as a writing medium was in widespread use, replacing traditional but more expensive writing mediums such as strips of bamboo rolled into threaded scrolls, scrolls and strips of silk, wet clay tablets hardened later in a furnace, and wooden tablets. The earliest known piece of paper with writing on it was discovered in the ruins of a Chinese watchtower at Tsakhortei, Alxa League, where Han Dynasty troops had deserted their position in AD 110 following a Xiongnu attack. In the papermaking process established by Cai in 105, a boiled mixture of mulberry tree bark, hemp, old linens, and fish nets created a pulp that was pounded into paste and stirred with water; a wooden frame sieve with a mat of sewn reeds was then dunked into the mixture, which was then shaken and then dried into sheets of paper that were bleached under the exposure of sunlight; K.S. Tom says this process was gradually improved through leaching, polishing and glazing to produce a smooth, strong paper.
Printing
Woodblock printing: The earliest specimen of woodblock printing a single-sheet dharani sutra in Sanskrit that was printed on hemp paper between 650 and 670 AD; it was unearthed in 1974 from a Tang tomb near Xi'an. A Korean miniature dharani Buddhist sutra discovered in 1966, bearing extinct Chinese writing characters used only during the reign of China's only self-ruling empress, Wu Zetian (r.690–705), is dated no earlier than 704 and preserved in a Silla Korean temple stupa built in 751. The first printed periodical, the Kaiyuan Za Bao was made available in AD 713. However, the earliest known book printed at regular size is the Diamond Sutra made during the Tang Dynasty (618–907), a 5.18 m (17 ft) long scroll which bears the date 868 AD, or the "fifteenth day of the fourth moon of the ninth year" of Emperor Yizong's (859–873) Xiantong 咸通 reign period. Joseph Needham and Tsien Tsuen-Hsuin write that the cutting and printing techniques used for the delicate calligraphy of the Diamond Sutra book are much more advanced and refined than the miniature dharani sutra printed earlier. The two oldest printed Chinese calendars are dated 877 and 882; they were found at the Buddhist pilgrimage site of Dunhuang; Patricia Ebrey writes that it is no surprise that some of the earliest printed items were calendars, since the Chinese found it necessary to calculate and mark which days were auspicious and which were not.
An illustration published in Wang Zhen's (fl. 1290–1333) book of AD 1313 showing movable type characters arranged by rhyme scheme in round table compartments
Movable type: The polymath scientist and official Shen Kuo (1031–1095) of the Song Dynasty (960–1279) was the first to describe the process of movable type printing in his Dream Pool Essays of 1088, attributing this innovation to a little-known artisan named Bi Sheng (990–1051). With the use of fired clay characters, Shen described Bi's technical process of making the type, type-setting, printing, and breaking up the type for further use. Bi had experimented with wooden type characters, but their use was not perfected until 1297 to 1298 with the model of the official Wang Zhen (fl. 1290–1333) of the Yuan Dynasty (1271–1368), who also arranged written characters by rhyme scheme on the surface of round table compartments. It was not until 1490 with the printed works of Hua Sui (1439–1513) of the Ming Dynasty (1368–1644) that the Chinese perfected metal movable type characters, namely bronze. The Qing Dynasty (1644–1912) scholar Xu Zhiding of Tai'an, Shandong developed vitreous enamel movable type printing in 1718.
The earliest artistic depiction of a fire lance gunpowder weapon, a painting at Dunhuang, dated Five Dynasties and Ten Kingdoms Period (907–960 AD)
Effects on bookbinding: The advent of printing in the 9th century revolutionized bookbinding, as late Tang Dynasty paper books evolved from rolled scrolls of paper into folded leaves like a pamphlet, which developed further in the Song Dynasty (960–1279) into 'butterfly' bindings with leaves of paper folded down the center like a common book, then during the Yuan Dynasty (1271–1368) wrapped back bindings had two edges of the leaves attached to the spine and secured with a stiff paper cover on the back, and during the Ming Dynasty (1368–1644) books finally had thread-stitched bindings in the back. It was not until the early 20th century that traditional Chinese thread-stitched bookbinding was replaced by Western-style bookbinding, a parallel to the replacement of traditional Chinese print methods with the modern printing press, in the tradition of Johannes Gutenberg (c. 1400–1468).
Gunpowder
Although evidence of gunpowder's first use in China comes from the Five Dynasties and Ten Kingdoms Period (907–960),[30] the earliest known recorded recipes for gunpowder were written by Zeng Gongliang, Ding Du, and Yang Weide in the Wujing Zongyao military manuscript compiled in 1044 during the Song Dynasty (960–1279); the gunpowder formulas described were used in incendiary bombs lobbed from catapults, thrown down from defensive walls, or lowered down the wall by use of iron chains operated by a swape lever. Bombs launched from trebuchet catapults mounted on forecastles of naval ships ensured the victory of Song over Jin forces at the Battle of Caishi in 1161, while the Mongol Yuan Dynasty (1271–1368) used gunpowder bombs during their failed invasion of Japan in 1274 and 1281. During the 13th and 14th centuries, gunpowder formulas became more potent (with nitrate levels of up to 91%) and gunpowder weaponry more advanced and deadly, as evidenced in the Ming Dynasty (1368–1644) military manuscript Huolongjing compiled by Jiao Yu (fl. 14th to early 15th century) and Liu Ji (1311–1375), completed before the latter's death with a preface added by the former in a 1412 Nanyang publication of the work.
Compass
A model in Kaifeng of a Chinese ladle-and-bowl type compass used for geomancy in the Han Dynasty (202 BC–220 AD); the historical authenticity of the model has been questioned by Li Shu-hua (1954).
Although an ancient hematite artifact from the Olmec era in Mexico dating roughly 1000 BC indicates the possible use of the lodestone compass long before it was described in China, the Olmecs did not have iron which the Chinese would discover could be magnetized by contact with lodestone. Descriptions of lodestone attracting iron were made in the Guanzi, Master Lu's Spring and Autumn Annals and Huainanzi. The Chinese by the Han Dynasty (202 BC–220 AD) began using north-south oriented lodestone ladle-and-bowl shaped compasses for divination and geomancy and not yet for navigation. The Lunheng, written by Wang Chong (27–c. 100 AD) stated in chapter 52: "This instrument resembles a spoon, and when it is placed on a plate on the ground, the handle points to the south". There are, however, another two references under chapter 47 of the same text to the attractive power of a magnet according to Needham (1986), but Li Shu-hua (1954) considers it to be lodestone, and states that there is no explicit mention of a magnet in Lunheng. Shen Kuo (1031–1095) of the Song Dynasty (960–1279) was the first to accurately describe both magnetic declination (in discerning true north) and the magnetic needle compass in his Dream Pool Essays of 1088, while the author Zhu Yu (fl. 12th century) was the first to mention use of the compass specifically for navigation at sea in his book published in 1119. Even before this, however, the Wujing Zongyao military manuscript compiled by 1044 described a thermoremanence compass of heated iron or steel shaped as a fish and placed in a bowl of water which produced a weak magnetic force via remanence and induction; the Wujing Zongyao recorded that it was used as a pathfinder along with the mechanical South Pointing Chariot.
China has been the source of many significant inventions, including the Four Great Inventions of ancient China: papermaking, the compass, gunpowder, and printing (both woodblock and movable type). The list below contains these and other inventions.
Discoveries
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
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.
Chinese remainder theorem: The Chinese remainder theorem, including simultaneous congruences in number theory, was first created by the mathematician Sunzi in the 3rd century AD, 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." 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). Thus, it was strongly associated with the divination methods of the ancient Yijing. ts 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.
Circadian rhythm, recognition of: 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. 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. 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. Chinese works on acupuncture also dealt with circadian rhythm, 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 (compiled from circa 419 to circa 930 AD).
Climate change, concept of: 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. It should be noted that Shen also advocated a hypothesis in line with geomorphology after he observed a strata 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).
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). 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. The first significant piece of Chinese literature to feature decimal fractions was the The Nine Chapters on the Mathematical Art. This text was first mentioned in 179 AD, 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). Liu Hui used decimal fractions with measurements and as solutions to equations. 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. Decimal fractions were vital to the work of Song (960–1279) mathematicians such as Yang Hui (1238–1298) and Qin Jiushao (c. 1201–1261). 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).
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, 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 5 tones and additions or subtractions of ⅓ of successive tone values which produce the rising fourths and falling fifths of Pythagorean tuning.
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. While generating his 60-divisional tuning, he discovered that 53 just fifths is approximate to 31 octaves, calculating the difference at ; this was the exact 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.[17][18] 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. 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. 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 12√2 (same as 21/12). 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.
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."[23] 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.
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 least by 179 AD during the Han Dynasty (202 BC–220 AD) and commented on by the 3rd century mathematician Liu Hui.
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.
Geobotanical prospecting: Geobotanical prospecting can be defined as the connection made between the types of vegetation that grow in certain areas and the minerals that can be found underground in those same areas; this observation was first made in China. It is now established in modern geobotany that only certain plants can grow in soils which are rich in certain types of minerals, such as Viola calaminaria and Thlaspi which grow in soils rich in zinc. The Zhou Dynasty (c. 1050–256 BC) Chinese Classic of Mountains and Rivers, compiled from the 6th to 2nd centuries BC, states that a certain "huitang" plant only grows near ore deposits of gold. As seen in the 5th century BC text Tribute of Yu, geobotanical prospecting in ancient China was mainly concerned with describing the nature of soil in different regions for agricultural purposes. The Book of Master Wen, compiled by 380 AD and containing material from as far back as the 3rd century BC, states that the branches of trees tend to droop in soils where an abundance of jade is to be found. In about 290 AD, Zhang Hua (232–300) wrote that hematite was found in abundance in any soil where smartweed grew. In the Illustrated Mirror of the Earth, written in the early 6th century AD, there is a description of a plant with an elegant yellow stalk which was found to grow above copper, and another description of a plant with green leaves and a red stalk where lead is often found below.[28] In his Miscellaneous Morsels from Youyang, the Tang Dynasty (618–907) author Duan Chengshi (d. 863) noted that silver could often be found in the soil where ciboule onion grew, gold where a certain kind of shallot grew, and copper where ginger grew. Su Song (1020–1101) of the Song Dynasty (960–1279) described how Portulaca oleracea could yield mercury if pounded, dried, and allowed to decay. The Precious Secrets of the Realm of the King of Xin, written in 1421 during the Ming Dynasty (1368–1644), described how mineral trace elements were observed and could be extracted from certain plants, such as copper from Oxalis corniculata, gold from rape turnip, silver from weeping willows, and lead and tin from mugwort, chestnut, barley, and wheat. Geobotanical prospecting was unknown in the rest of the world until about 1600 when Sir Thomas Challoner and his first cousin Thomas Challoner discovered alum mines on the former's property of Belman Bank, Guisborough, Yorkshire, England. Both Challoner relatives realized here (and later in Italy) that leaves of oak trees were a much darker, richer green and their branches stronger and more spread out where the alum was to be found.
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).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. 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.
Mohandas Karamchand Gandhi tends to a leper; the Chinese were the first to describe the symptoms of leprosy.
Leprosy, first description of its symptoms: The Feng zhen shi 封診式 (Models for sealing and investigating), written between 266 and 246 BC in the State of Qin during the Warring States Period (403–221 BC), is the earliest known text which describes the symptoms of leprosy, termed under the generic word li 癘 (for skin disorders). This text mentioned the destruction of the nasal septum in those suffering from leprosy (an observation that would not be made outside of China until the writings of Avicenna in the 11th century), and according to Katrina McLeod and Robin Yates it also stated lepers suffered from "swelling of the eyebrows, loss of hair, absorption of nasal cartilage, affliction of knees and elbows, difficult and hoarse respiration, as well as anaesthesia." Leprosy was not described in the West until the writings of the Roman authors Aulus Cornelius Celsus (25 BC – 37 AD) and Pliny the Elder (23–79 AD). Although it is alleged that the Indian Sushruta Samhita, which describes leprosy, is dated to the 6th century BC, India's earliest written script (besides the then long extinct Indus script)—the Brāhmī script—is thought to have been created no earlier than the 3rd century BC.
Negative numbers, symbols for and use of: In the Nine Chapters on the Mathematical Art compiled during the Han Dynasty (202 BC–220 AD) by 179 AD and commented on by Liu Hui (fl. 3rd century) in 263, negative numbers appear as black rods and positive numbers as red rods in the Chinese counting rods system. Liu Hui also used slanted counting rods to denote negative numbers. Negative numbers denoted by a "+" sign also appear in the ancient Bakhshali manuscript of India, yet scholars disagree as to when it was compiled, giving a collective range of 200 to 600 AD. Negative numbers were known in India certainly by about 630 AD, when the mathematician Brahmagupta (598–668) used them. Negative numbers were first used in Europe by the Greek mathematician Diophantus (fl. 3rd century) in about 275 AD, yet were considered absurd in the West until The Great Art written in 1545 by the Italian mathematician Girolamo Cardano (1501–1576).
Pi calculated as : The ancient Egyptians, Babylonians, Indians, and Greeks had long made approximations for π by the time the Chinese mathematician and astronomer Liu Xin (c. 46 BC–23 AD) improved the old Chinese approximation of simply 3 as π to 3.1547 as π (with evidence on vessels dating to the Wang Mang reign period, 9–23 AD, of other approximations of 3.1590, 3.1497, and 3.1679). Next, Zhang Heng (78–139 AD) made two approximations for π, by proportioning the celestial circle to the diameter of the earth as = 3.1724 and using (after a long algorithm) the square root of 10, or 3.162. In his commentary on the Han Dynasty mathematical work The Nine Chapters on the Mathematical Art, Liu Hui (fl. 3rd century) used various algorithms to render multiple approximations for pi at 3.142704, 3.1428, and 3.14159. Finally, the mathematician and astronomer Zu Chongzhi (429–500) approximated pi to an even greater degree of accuracy, rendering it , a value known in Chinese as Milü ("detailed ratio"). This was the best rational approximation for pi with a denominator of up to four digits; the next rational number is , which is the best rational approximation. Zu ultimately determined the value for π to be between 3.1415926 and 3.1415927. Zu's approximation was the most accurate in the world, and would not be achieved elsewhere for another millennium,[42] until Madhava of Sangamagrama and Jamshīd al-Kāshī in the early 15th century.
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." This was the first explicit reference in world history to the hexagonal structure of snowflakes. 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). 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. 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. 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.
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." 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." 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; 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. 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.
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." There were other mentionings of spontaneous combustion in early Chinese literary works, while more often than not fires were blamed on arsonists. 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. 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. 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.
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. 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).[50] From 28 BC to 1368 AD, a total of 112 other instances of sunspots were recorded by the Chinese.[51] 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. 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.
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. 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. 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.
