Many significant developments in thehistory of science and technology in China took place during theHan dynasty (202 BCE – 220 CE[2]).
The Han period saw great innovations inmetallurgy. Following the inventions of theblast furnace andcupola furnace during theZhou dynasty (c. 1046 – 256 BCE) to makepig iron andcast iron respectively, the Han period saw the development ofsteel andwrought iron by use of thefinery forge andpuddling process. With the drilling of deepboreholes into the earth, the Chinese used not onlyderricks to liftbrine up to the surface to be boiled intosalt, but also set up bamboo-craftedpipeline transport systems which broughtnatural gas as fuel to the furnaces.
Smelting techniques were enhanced with inventions such as thewaterwheel-poweredbellows; the resulting widespread distribution of iron tools facilitated the growth of agriculture. Fortilling the soil and planting straight rows of crops, the improved heavy-moldboard plough with three ironplowshares and sturdy multiple-tube ironseed drill were invented in the Han, which greatly enhanced production yields and thus sustained population growth. The method of supplyingirrigation ditches with water was improved with the invention of the mechanicalchain pump powered by the rotation of a waterwheel or draft animals, which could transport irrigation water up elevated terrains. The waterwheel was also used for operatingtrip hammers in pounding grain and in rotating the metal rings of the mechanical-driven astronomicalarmillary sphere representing thecelestial sphere around the Earth.
The Han initially wrote on hemp-bound bamboo scrolls; by the 2nd century CE, they had invented thepapermaking process which created a writing medium that was both cheap and easy to produce. The invention of thewheelbarrow aided in the hauling of heavy loads. The maritimejunk ship and stern-mounted steeringrudder enabled the Chinese to venture out of calmer waters of interior lakes and rivers and into the open sea. The invention of thegrid reference for maps andraised-relief map allowed for better navigation.In medicine, they used newherbal remedies to cure illnesses,calisthenics to keep physically fit, and regulateddiets to avoid diseases. Authorities in the capital were warned ahead of time of the direction of sudden earthquakes with the invention of theseismometer that was tripped by a vibration-sensitivependulum device.
To mark the passing of the seasons and special occasions, the Hanused two variations of thelunisolar calendar, which were established due to efforts inastronomy andmathematics. Han-era Chinese advancements in mathematics include the discovery ofsquare roots,cube roots, thePythagorean theorem,Gaussian elimination, theHorner scheme, improved calculations ofpi, andnegative numbers. Hundreds of new roads and canals were built to facilitate transport, commerce, tax collection, communication, and movement of military troops. The Han-era Chinese also employed several types of bridges to cross waterways and deep gorges, such asbeam bridges,arch bridges,simple suspension bridges, andpontoon bridges. Han ruins ofdefensive city walls made ofbrick orrammed earth still stand.
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Jin Guantao, a professor at theChinese University of Hong Kong, Fan Hongye, a research fellow with theChinese Academy of Sciences, and Liu Qingfeng, a professor at the Chinese University of Hong Kong, assert that the latter part of the Han dynasty was a unique period in thehistory of premodern Chinese science and technology.[3] They compare it to the incredible pace ofscientific and technological growth during theSong dynasty (960–1279). However, they also argue that without the influence of proto-scientific precepts in the ancient philosophy ofMohism, Chinese science continued to lack a definitive structure:[3]
From the middle and late Eastern Han to the early Wei and Jin dynasties, the net growth of ancient Chinese science and technology experienced a peak (second only to that of the Northern Song dynasty) ...Han studies of the Confucian classics, which for a long time had hindered the socialization of science, were declining. If Mohism, rich in scientific thought, had rapidly grown and strengthened, the situation might have been very favorable to the development of a scientific structure. However, this did not happen because the seeds of the primitive structure of science were never formed. During the late Eastern Han, disastrous upheavals again occurred in the process of social transformation, leading to the greatest social disorder in Chinese history. One can imagine the effect of this calamity on science.[3]
Joseph Needham, a professor from theUniversity of Cambridge and author of theScience and Civilisation in China series, stated that the "Han time (especially the Later Han) was one of the relatively important periods as regards thehistory of science in China."[4] He noted the advancements during Han ofastronomy andcalendrical sciences, the "beginnings of systematicbotany andzoology", as well as thephilosophical skepticism andrationalist thought embodied in Han works such as theLunheng by the philosopherWang Chong.[4]
The most common writing mediums found in archaeological digs from ancient sites predating the Han period areshells and bones as well asbronzewares.[5] In the beginning of the Han period, the chief writing mediums were bamboo (Chinese:竹簡) andclay tablets,silk cloth, strips of soft wood,[6] and rolled scrolls made of strips ofbamboo sewn together withhempen string passed through drilled holes (册) and secured withclay stamps.[7] Thewritten characters on these narrow flat strips of bamboo were arranged into vertical columns.[8]
Whilemaps drawn in ink on flat silk clothshave been found in the tomb of the Marquess of Dai (interred in 168 BCE), the earliest knownpaper map found in China, dated 179–141 BCE and located atFangmatan, is incidentally the oldest known piece of paper.[9] Chinese hempen paper of the Western Han and early Eastern Han eras was of a coarse quality and used primarily aswrapping paper.[10] Thepapermaking process was not formally introduced until the Eastern Han court eunuchCai Lun created a process in 105 wheremulberry tree bark, hemp, old linens, and fish nets were boiled together to make paper pulp.[11] The oldest known piece of paper with writing on it comes from the ruins of a Chinesewatchtower at Tsakhortei,Alxa League, Inner Mongolia, dated to 110 CE when the Han garrison abandoned the area following a nomadicXiongnu attack.[12] By the 3rd century, paper became one of China's chief writing mediums.[13]
The Hanceramics industry was upheld by private businesses as well as local government agencies.[14] Ceramics were used in domestic wares and utensils as well as construction materials for rooftiles andbricks.[15]
Han dynasty greypottery—its color derived from theclay that was used—was superior to earlier Chinese grey pottery due to the Han people's use of largerkiln chambers, longer firing tunnels, and improved chimney designs.[16] Kilns of the Han dynasty making grey pottery were able to reach firing temperatures above 1,000 °C (1,830 °F).[16] However, hard southern Chinese pottery made from a dense adhesive clay native only in the south was fired at even higher temperatures during the Han.[16]Glazed pottery of theShang (c. 1600 – c. 1050 BCE) andZhou (c. 1050 – 256 BCE) dynasties were fired at high temperatures, but by the mid Western Han (206 BCE – 9 CE), a brown-glazed ceramic was made which was fired at 800 °C (1,470 °F), followed by a green-glazed ceramic which became popular in the Eastern Han (25–220 CE).[17]
Wang Zhongshu states that the light-greenstoneware known asceladon was thought to exist only since theThree Kingdoms period (220–265 CE), but argues that ceramic shards found at Eastern Han (25–220 CE) sites of Zhejiang province can be classified as celadon.[18] However, Richard Dewar argues that true celadon was not created in China until the earlySong dynasty (960–1279) when Chinese kilns were able to reach a minimum furnace temperature of 1,260 °C (2,300 °F), with a preferred range of 1,285 to 1,305 °C (2,345 to 2,381 °F) for celadon.[19]
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Ablast furnace converts rawiron oxide intoiron, which can be remelted in acupola furnace to producecast iron. The earliest specimens of cast iron found in China date to the 5th century BCE during the lateSpring and Autumn period, yet the oldest discovered blast furnaces date to the 3rd century BCE and the majority date to the period afterEmperor Wu of Han (r. 141–87 BCE)established a government monopoly over the iron industry in 117 BCE (most of the discovered iron works sites built before this date were merelyfoundries which recast iron that had been smelted elsewhere).[20] Iron ore smelted in blast furnaces during the Han was rarely if ever cast directly into permanent molds; instead, the pig iron scraps were remelted in the cupola furnace to make cast iron.[21] Cupola furnaces utilized acold blast traveling throughtuyere pipes from the bottom and over the top where the charge ofcharcoal and pig iron was introduced.[21] The air traveling through the tuyere pipes thus became ahot blast once it reached the bottom of the furnace.[21]
Although Chinese civilization lacked thebloomery, the Han Chinese were able to makewrought iron when they injected too muchoxygen into the cupola furnace, causingdecarburization.[22] The Han-era Chinese were also able to convert cast iron and pig iron into wrought iron andsteel by using thefinery forge andpuddling process, the earliest specimens of such dating to the 2nd century BCE.[23] The semisubterranean walls of these furnaces were lined withrefractory bricks and had bottoms made of refractory clay.[24] Besides charcoal made of wood,Wang Zhongshu states that another furnace fuel used during the Han were "coal cakes", a mixture ofcoal powder, clay, andquartz.[25]
Donald B. Wagner writes that most domestic iron tools and implements produced during the Han were made of cheaper and more brittle cast iron, whereasthe military preferred to use wrought iron and steel weaponry due to their more durable qualities.[26] During the Han dynasty, the typical 0.5 m (1.6 ft)bronze sword of theWarring States period was gradually replaced withan iron sword measuring roughly 1 m (3.3 ft) in length.[27] The ancientdagger-axe (ge) made of bronze was still used by Han soldiers, although it was gradually phased out by iron spears and ironji halberds.[28] Evenarrowheads, which were traditionally made of bronze, gradually only had a bronze tip and iron shaft, until the end of the Han when the entire arrowhead was made solely of iron.[28] Farmers,carpenters, craftsmen,stonemasons, andrammed earth builders had at their disposal iron tools such as theplowshare,pickaxe,spade,shovel,hoe,sickle,axe,adze,hammer,chisel,knife,saw,scratch awl, andnails.[29] Common iron commodities found in Han dynasty homes included tripods,stoves,cooking pots,belt buckles,tweezers, firetongs,scissors, kitchen knives,fish hooks, andneedles.[28]Mirrors andoil lamps were often made of either bronze or iron.[30]Coin money mintedduring the Han was made of eithercopper or copper andtin smelted together to make the bronze alloy.[31]
Modern archaeologists have unearthed Han iron farming tools throughout China, fromInner Mongolia in the north toYunnan in the south.[32] The spade, shovel, pick, andplow were used fortillage, the hoe forweeding, therake for loosening the soil, and thesickle for harvesting crops.[32] Depending on their size, Han plows were driven by one to two oxen.[33] Oxen were also used to pull the three-legged ironseed drill (invented in Han China by the 2nd century BCE), which enabled farmers to plant seeds in precise rows instead ofcasting them out by hand.[34] While artwork of theWei (220–266 CE) andJin (266–420) periods show use of theharrow for breaking up chunks of soil after plowing, it perhaps first appeared in China during the Eastern Han (25–220 CE).[35]Irrigation works for agriculture included the use ofwater wells, artificial ponds and embankments,dams,canals, andsluice gates.[36]
DuringEmperor Wu's (r. 141–87 BCE) reign, the Grain Intendant Zhao Guo (Chinese:趙過) invented the alternating fields system (daitianfa 代田法).[37] For everymou of land—a thin strip of land measuring 1.38 m (4.5 ft) wide and 331 m (1,086 ft) long, or an area of roughly 457 m2 (0.113 acres)[38][39]—three low-lyingfurrows (quan 甽) that were each 0.23 m (0.75 ft) wide were sowed in straight lines with crop seed.[37] While weeding in the summer, the loose soil of theridges (long 壟) on either side of the furrows would gradually fall into the furrows, covering the sprouting crops and protecting them from wind and drought.[37] Since the position of the furrows and ridges were reversed by the next year, this process was called the alternating fields system.[37]
This system allowed crops to grow in straight lines from sowing to harvest, conserved moisture in the soil, and provided a stable annual yield.[40] Zhao Guo first experimented with this system right outside the capitalChang'an, and once it proved successful, he sent out instructions for it to everycommandery administrator, who were then responsible for disseminating these to the heads of everycounty,district, andhamlet in their commanderies.[40]
Rich families who owned oxen and large heavy moldboard iron plows greatly benefited from this new system.[41] However, poorer farmers who did not own oxen resorted to using teams of men to move a single plow, which was exhausting work.[41] The author Cui Shi (Chinese:催寔) (d. 170 CE) wrote in hisSimin yueling (Chinese:四民月令) that by the Eastern Han Era (25–220 CE) an improved plow was invented which needed only one man to control it, two oxen to pull it, had three plowshares, a seed box for the drills, a tool which turned down the soil, and could sow roughly 45,730 m2 (11.30 acres) of land in a single day.[42]
During the reign ofEmperor Cheng of Han (r. 33–37 BCE), Fan Shengzhi wrote a manual (theFan Shengzhi shu) which described the pit field system (aotian 凹田).[43][44] In this system, everymou of farmland was divided into 3,840 grids which each had a small pit that was dug 13.8 cm (5.4 in) deep and 13.8 cm (5.4 in) wide and had good qualitymanure mixed into the soil.[43] Twenty seeds were sowed into each pit, which allegedly produced 0.6 L (20oz) of harvested grain per pit, or roughly 2,000 L (67,630 oz) permou.[43] This system did not require oxen-driven plows or the most fertile land, since it could be employed even on sloping terrains where supplying water was difficult.[45] Although this farming method was favored by the poor, it did require intensive labor, so only large families could maintain such a system.[46]
Han farmers in theYangzi River region of southern China often maintainedpaddy fields for growingrice. Every year, they would burn the weeds in the paddy field, drench it in water, sow rice by hand, and around harvest time cut the surviving weeds and drown them a second time.[47] In this system, the field laysfallow for much of the year and thus did not remain very fertile.[47] However, Han rice farmers to the north around theHuai River practiced the more advanced system oftransplantation.[48] In this system, individual plants were given intensive care (perhaps in the same location as the paddy field), their offshoots separated so that more water could be conserved, and the field could be heavily fertilized since winter crops were grown while the rice seedlings were situated nearby in a plant nursery.[48]
Evidence of Han-era mechanical engineering comes largely from the choice observational writings of sometimes disinterested Confucian scholars. Professional artisan-engineers (jiangChinese:匠) did not leave behind detailed records of their work.[49] Han scholars, who often had little or no expertise in mechanical engineering, sometimes provided insufficient information on the various technologies they described.[50]
Nevertheless, some Han literary sources provide crucial information. As written by Yang Xiong in 15 BCE, thebelt drive was first used for aquilling device which wound silk fibers onto thebobbins of weaver shuttles.[51] The invention of the belt drive was a crucial first step in the development oflater technologies during the Song dynasty, such as thechain drive andspinning wheel.[51]
The inventions of the artisan and mechanical engineer Ding Huan (Chinese:丁緩) are mentioned in theMiscellaneous Notes on the Western Capital.[52] The official and poetSima Xiangru hinted in his writings that the Chinese used acenser in the form of agimbal, a pivot support made of concentric rings which allow the central gimbal torotate on an axis while remaining vertically positioned.[53] However, the first explicit mention of the gimbal used as an incense burner occurred around 180 CE when the artisan Ding Huan created his 'Perfume Burner for use among Cushions' which allowed burning incense placed within the central gimbal to remain constantly level even when moved.[54] Ding had other inventions as well. For the purpose of indoorair conditioning, he set up a large manually operatedrotary fan which had rotating wheels that were 3 m (9.8 ft) in diameter.[55] He also invented a lamp which he called the 'nine-storied hill-censer', since it was shaped as a hillside.[56] When the cylindrical lamp was lit, theconvection of rising hot air currents caused vanes placed on the top to spin, which in turn rotated painted paper figures of birds and other animals around the lamp.[56]
WhenEmperor Gaozu of Han (r. 202–195 BCE) came upon the treasury ofQin Shi Huang (r. 221–210) following the downfall of theQin dynasty (221–206), he found an entire miniature musical orchestra ofpuppets 1 m (3.3 ft) tall who playedmouth organs if one pulled on ropes and blew into tubes to control them.[57] Zhang Heng wrote in the 2nd century CE that people could be entertained by theatrical plays of artificial fish and dragons.[57] Later, the inventorMa Jun (fl. 220–265) invented a theater of moving mechanical puppets powered by the rotation of a hidden waterwheel.[57]
From literary sources it is known that the collapsible umbrella was invented during Wang Mang's reign, although the simple parasol existed beforehand. This employed sliding levers and bendable joints that could be protracted and retracted.[58]
Modern archaeology has led to the discovery of Han artwork portraying inventions which were otherwise absent in Han literary sources. This includes thecrank handle. Han pottery tomb models of farmyards andgristmills possess the first known depictions of crank handles, which were used to operatethe fans of winnowing machines.[59] The machine was used to separatechaff from grain, but the Chinese of later dynasties also employed the crank handle for silk-reeling, hemp-spinning, flour-sifting, and drawing water from a well using thewindlass.[59] To measure distance traveled, the Han-era Chinese also created theodometer cart. This invention is depicted in Han artwork by the 2nd century CE, yet detailed written descriptions were not offered until the 3rd century.[60] The wheels of this device rotated a set of gears which in turn forced mechanical figures to bang gongs and drums that alerted the travelers of the distance traveled (measured inli).[61] From existing specimens found at archaeological sites, it is known that Han-era craftsmen made use of the sliding metalcaliper to make minute measurements. Although Han-era calipers bear incised inscriptions of the exact day of the year they were manufactured, they are not mentioned in any Han literary sources.[62]
By the Han dynasty, the Chinese developed various uses for thewaterwheel. An improvement of the simplelever-and-fulcrum tilt hammer device operated by one's foot, the hydraulic-poweredtrip hammer used for pounding,decorticating, and polishing grain was first mentioned in theHan dictionaryJijiupian of 40 BCE.[63] It was also mentioned in theRegional Speech (Fangyan) dictionary written byYang Xiong (53 BCE – 18 CE) in 15 BCE, the philosophicalXinlun 新論 written byHuan Tan (43 BCE – 28 CE) in 20 CE, the poetry ofMa Rong (79–166 CE), and the writings ofKong Rong (153–208 CE).[63]
In hisBalanced Discourse (Lunheng), the philosopherWang Chong was the first in China to describe the square-palletchain pump used to lift water (and other substances).[64] Although some models were operated manually by foot pedals, some chain pumps were powered by a horizontal waterwheel which rotated large toothed gears and a horizontal axis beam.[65] Their primary use was for lifting water into irrigation ditches, but chain pumps were also used inpublic works programs, such as whenZhang Rang (d. 189) had an engineer build several of them to lift water into pipes that provided the capitalLuoyang andits palaces with clean water.[66]
While acting as administrator ofNanyang in 31 CE,Du Shi invented a water-poweredreciprocator which worked the bellows of the blast furnace and cupola furnace in smelting iron; before this invention, intensive manual labor was required to work the bellows.[67]
Although the astronomicalarmillary sphere (representing thecelestial sphere) had existed in China since the 1st century BCE, the mathematician and court astronomerZhang Heng provided it with motive power by using the constantpressure head of an inflowwater clock to rotate a waterwheel that acted on a set ofgears.[68] Zhang Heng was also the first to address the problem of the falling pressure head in the inflow water clock (which gradually slowed thetimekeeping) by setting up an additional tank between the reservoir and inflow vessel.[69]
The Han court was responsible for the major efforts of disaster relief when natural disasters such asearthquakes devastated the lives of commoners.[70] To better prepare for calamities, Zhang Heng invented aseismometer in 132 CE, which provided instant alert to authorities in the capital Luoyang that an earthquake had occurred in a location indicated by a specificcardinal or ordinal direction.[71] Although no tremors could be felt in the capital when Zhang told the court that an earthquake had just occurred in the northwest, a message came soon afterwards that an earthquake had indeed struck 400 to 500 km (250 to 310 mi) northwest of Luoyang (in what is now modernGansu).[72] Zhang called his device the 'instrument for measuring the seasonal winds and the movements of the Earth' (Houfeng didong yi 候风地动仪), so-named because he and others thought that earthquakes were most likely caused by the enormous compression of trapped air.[73]
As described in theBook of the Later Han, the frame of the seismometer was a domed bronze vessel in the shape ofa wine jar, although it was 1.8 m (5.9 ft) in diameter and decorated with scenes of mountains and animals.[74] The trigger mechanism was aninverted pendulum (which theBook of the Later Han calls the "central column") that, if disturbed by the ground tremors of earthquakes located near or far away, would swing and strike one of eight mobile arms (representing the eight directions), each with a crank and catch mechanism.[75] The crank and a right angle lever would raise one of eight metal dragon heads located on the exterior, dislodging a metal ball from its mouth that dropped into the mouth of one of eight metal toads below arranged like the points on acompass rose, thus indicating the direction of the earthquake.[75] TheBook of the Later Han states that when the ball fell into any one of eight toad mouths, it produced a loud noise which gained the attention of those observing the device.[76] While Wang Zhenduo (Chinese:王振铎) accepted the idea that Zhang's seismometer had cranks and levers which were disturbed by the inverted pendulum, his contemporaryAkitsune Imamura argued that the inverted pendulum could have had a pin at the top which, upon moving by force of the ground vibrations, would enter one of eight slots and expel the ball by pushing a slider.[77] Since theBook of the Later Han states that the other seven dragon heads would not subsequently release the balls lodged up into their jaws after the first one had dropped, Imamura asserted that the pin of the pendulum would have been locked into the slot it had entered and thus immobilized the instrument until it was reset.[75]
One of the earliest surviving mathematical treatises of ancient China is theBook on Numbers and Computation (Suan shu shu), part of theZhangjiashan Han bamboo texts dated 202 to 186 BCE and found inJiangling County,Hubei.[78] Another mathematical text compiled during the Han wasThe Arithmetical Classic of the Gnomon and the Circular Paths of Heaven (Zhoubi Suanjing), dated no earlier than the 1st century BCE (from perhaps multiple authors) and contained materials similar to those described by Yang Xiong in 15 BCE, yet thezhoubi school of mathematics was not explicitly mentioned untilCai Yong's commentary of 180.[79] A preface was added to the text by Zhao Shuang (Chinese:趙爽) in the 3rd century.[80] There was also theNine Chapters on the Mathematical Art (Jiuzhang Suanshu); its full title was found on two bronze standard measurers dated 179 CE (with speculation that its material existed in earlier books under different titles) and was provided with detailed commentary byLiu Hui (fl. 3rd century) in 263.[81] It is worth noting in this context that many of the documents excavated from Qin and Han sites contain evidence of the practical mathematics used by administrators for inventories and taxes, as well as for calculating labor needed for public works projects, just as described in the mathematical treatises.[82]
TheSuan shu shu presents basic mathematics problems and solutions. It was most likely a handbook for day-to-day business transactions or affairs of government administration.[83] It contains problems and solutions for field measurements ofarea, proportionalexchange rates for agriculturalmillet andrice, distribution byproportion, short width division, and excess and deficiency.[84] Some of the problems found in theSuan shu shu appear in the later textJiuzhang suanshu; in five cases, the titles are exact matches.[84] However, unlike theJiuzhang suanshu, theSuan shu shu does not deal with problems involving right-angle triangles,square roots,cube roots, andmatrix methods, which demonstrates the significant advancements made in Chinese mathematics between the writings of these two texts.[85]
TheZhoubi suanjing is concerned with the application of mathematics toastronomy. In one problem which sought to determine the height of theSun from theEarth and thediameter of the Sun, Chen Zi (Chinese:陳子) instructs Rong Fang (Chinese:榮方) to wait until the shadow cast by the 8 chi tallgnomon is 6 chi (onechi during the Han was 33 cm), so that a 3-4-5 right-angle triangle can be constructed where the base is60,000li (oneli during the Han was the equivalent of 415 m or 1362 ft), thehypotenuse leading towards the sun is 100,000 li, and the height of the sun is 80,000 li.[86] Like theJiuzhang suanshu, theZhoubi suanjing also givesmathematical proof for the "Gougu Theorem" (Chinese:勾股定理; i.e. wherec is the length of the hypotenuse anda andb are the lengths of the other two sides, respectively, a2 + b2 = c2), which is known as thePythagorean theorem in the West after the Greek mathematicianPythagoras (fl. 6th century BCE).[87]
TheJiuzhang suanshu was perhaps the most groundbreaking of the three surviving Han treatises. It is the first known book to featurenegative numbers, along with theBakhshali manuscript (200? – 600? CE) ofIndia and the book ofthe Greek mathematicianDiophantus written in about 275 CE.[88] Negative numbers appeared asblack counting rods, while positive numbers appeared asred counting rods.[89] Although thedecimal system existed in China since theShang dynasty (c. 1600 – c. 1050 BCE), the earliest evidence of adecimal fraction (i.e. the denominatoris a power of ten) is an inscription on a standard volume-measuring vessel dated 5 CE and used by the mathematician and astronomerLiu Xin (46 BCE – 23 CE).[90] Yet the first book to feature decimal fractions was theJiuzhang suanshu, as a means to solveequations and represent measurements.[90]Gaussian elimination, analgorithm used to solvelinear equations, was known as the Array Rule in theJiuzhang suanshu.[91] While the book used continued fractions to find theroots of equations, Liu Hui built on this idea in the 3rd century when he increased the decimals to find the cube root of 1,860,867 (yielding the answer 123), the same method used in theHorner scheme named afterWilliam George Horner (1786–1837).[92]
For centuries, the Chinese had simply approximated the value ofpi as 3, until Liu Xin approximated it at 3.154 sometime between 1–5 CE, although the method he used to reach this value is unknown.[93] Standard measuring vessels dating to the reign ofWang Mang (9–23 CE) also showedapproximations for pi at 3.1590, 3.1497, and 3.167.[94] Zhang Heng is the next known Han mathematician to have made an approximation for pi. Han mathematicians understood that the area of a square versus the area of its inscribed circle had an approximateratio of 4:3, and also understood that the volume of a cube and the volume of its inscribed sphere would be 42:32.[94] WithD asdiameter andV as volume, D3:V = 16:9 or V=9⁄16D3, a formula Zhang found fault with since he realized the value for diameter was inaccurate, the discrepancy being the value taken for the ratio.[95] To fix this, Zhang added1⁄16D3 to the formula, thus V =9⁄16D3 +1⁄16D3 =5⁄8D3. Since he found the ratio of the volume of the cube to the inscribed sphere at 8:5, the ratio of the area of a square to the inscribed circle is√8:√5.[96] With this formula, Zhang was able to approximate pi as thesquare root of 10, or 3.162.[97] After the Han,Liu Hui approximated pi as 3.14159, while the mathematicianZu Chongzhi (429–500)approximated pi at 3.141592 (or355⁄113), the most accurate approximation the ancient Chinese would achieve.[98]
Mathematics were also used inmusical tuning andmusic theory. The 2nd-century BCEHuainanzi, compiled byeight scholars under the patronage of KingLiu An (179–122 BCE), outlined the use oftwelve tones on amusical scale.[99]Jing Fang (78–37 BCE), a mathematician and music theorist, expanded these to create a scale of 60 tones.[99] While doing so, Jing Fang realized that 53just fifths is approximate to 31octaves.[100] By calculating the difference at177147/176776, Jing reached the same value of53 equal temperament duly discovered by the German mathematicianNicholas Mercator (1620–1687) (i.e.353/284 353 / 284, known asMercator's comma).[100] Later, the princeZhu Zaiyu (1536–1611) inMing China andSimon Stevin (1548–1620) of theFlemish Region in Europe would simultaneously (but separately) discover the mathematical formula forequal temperament.[101]
The ancient Chinese made careful observations of heavenly bodies and phenomena since observations of the cosmos were used forastrology and prognostication.[102] The astronomerGan De (fl. 4th century BCE) from theState of Qi was the first in history to acknowledgesunspots as genuine solar phenomena (and not obstructingnatural satellites as thought in the West afterEinhard's observation in 807 CE), while the first precisely dated sunspot observation in China occurred on May 10, 28 BCE, during the reign ofEmperor Cheng of Han (r. 33–7 BCE).[103] Among theMawangdui Silk Texts dated no later than 168 BCE (when they were sealed in a tomb atMawangdui Han tombs site,Changsha,Hunan province), theMiscellaneous Readings of Cosmic Patterns and Pneuma Images (Tianwen qixiang zazhan 天文氣象雜占) manuscript illustrates in writings and ink drawings roughly 300 different climatic and astronomical features, including clouds,mirages,rainbows,stars,constellations, andcomets.[104] Another silk text from the same site reports the times and locations of the rising and setting of planets in the night sky from the years 246–177 BCE.[105]
The Han-era Chinese noted the passage of the same comet seen inPersia for the birth ofMithridates II of Parthia in 135 BCE,the same cometthe Romans observed close to theassassination of Julius Caesar in 44 BCE,Halley's Comet in 12 BCE, the same comet noted by Roman historianCassius Dio (c. 155 – c. 229 CE) for 13 CE, and (what is now known to have been)a supernova in AD 185.[106] For various comets discussed in the Han-era history booksRecords of the Grand Historian andBook of Han, details are given for their position in the sky and direction they were moving, the length of time they were visible, their color, and their size.[107]
The Han-era Chinese also madestar catalogues, such as historianSima Qian's (145–86 BCE)A Monograph on Celestial Officials (Tianguanshu 天官書) and Zhang Heng's 2nd-century-CE star catalogue which featured roughly 2,500 stars and 124 constellations.[108] To create a three-dimensional representation of such observations,[109] Astronomer Geng Shouchang (Chinese:耿壽昌) provided hisarmillary sphere with anequatorial ring in 52 BCE. By 84 CE, the elliptical ring was added to the armillary sphere, while Zhang Heng's model of 125 added thecelestial horizon ring andmeridian ring.[110]
The Han Chinese used astronomical studies mainly to construct and revise theircalendar. In contrast to theJulian calendar (46 BCE) andGregorian calendar (1582) ofthe West (but like theHellenic calendars ofClassical Greece), theChinese calendar is alunisolar calendar, meaning that it uses the precise movements of theSun andMoon as time-markers throughout the year.[111] During the spring and autumn periods of the 5th century BCE, the Chinese established the Sifen calendar (古四分历), which measured thetropical year at 3651⁄4 days (like the Julian calendar of Rome).[112] Emperor Wu replaced this with the new Taichu calendar (Chinese:太初历) in 104 BCE, which measured the tropical year at 365385⁄1539 days and thelunar month at 2943⁄81 days.[112] Since the Taichu calendar had become inaccurate over two centuries,Emperor Zhang of Han (r. 75–88 CE) halted its use and revived use of the Sifen calendar.[113] It was more than a millennium later that astronomerGuo Shoujing (1233–1316) would set the tropical year at 365.2425 days for his Shoushi calendar (Chinese:授時曆), the same value used in the Gregorian calendar.[114] Besides the use of the calendar for regulating agricultural practices throughout the seasons, it was also used to mark important dates in theSexagenary cycle—constructed bycelestial stems (gan 干) andEarthly Branches (zhi 支), each of the latter associated with an animal of theChinese zodiac.[115]
The Han-era Chinese discussed the illumination and shapes of heavenly bodies: were they flat and circular, or were they rounded and spherical?Jing Fang wrote in the 1st century BCE that Han astronomers believed the Sun, Moon, and planets were spherical like balls orcrossbow bullets.[116] He also wrote that the Moon and planets produce no light of their own, are viewable to people on Earth only because they are illuminated by the Sun, and those parts not illuminated by the Sun would be dark on the other side.[116]
In hisBalanced Discourse (Lunheng),Wang Chong wrote that some Han thinkers believed that rain fell from the Heavens (i.e. where the stars were located).[117] Wang argued that, although rain fell from above, this common theory was false.[117] He agreed with another theory that stated clouds were formed by theevaporation of water on Earth, and that since clouds disperse rain, clouds and rain are in fact one and the same; in essence, he accurately described thewater cycle.[117]
In the 2nd century CE,Zhang Heng drew a similar comparison to Jing's by stating that the Sun is like fire and the Moon and planets are like water, since fire produces light and water reflects it.[118] He also repeated Jing's comment that the side of the Moon not illuminated by the Sun was left in darkness.[118] However, Zhang noted thatsunlight did not always reach the Moon since the Earth obstructs the rays during alunar eclipse.[118] He also noted that asolar eclipse occurred when the Moon and Sun crossed paths to block sunlight from reaching earth.[118]
Zhao Shaung's 3rd-century commentary in theZhoubi suanjing describes two astronomical theories: in one, the heavens are shaped as a hemi-spherical dome extending over the Earth, while the other compares the Earth to the centralyolk of an egg, where the heavens are shaped as acelestial sphere around the earth.[80] The latter astronomical theory was mentioned by Yang Xiong in hisModel Sayings (Fayan 法言) and expounded on by Zhang Heng in hisSpiritual Constitution of the Universe (Lingxian 靈憲) of 120 CE.[119]
Timber was the chief building material in Han architecture.[120] It was used for grand palace halls, multi-story towers, multi-story residential halls, and humble abodes.[120] However, due to wood's decay over time and susceptibility to fire, the oldest wooden buildings found in China (i.e. several temple halls ofMount Wutai) date no earlier than theTang dynasty (618–907).[121] Architectural historian Robert L. Thorp describes the scarcity of Han-era archaeological remains, as well as the often unreliable Han-era literary and artistic sources used by historians for clues about non-existent Han architecture.[122] What remains of Han-dynasty architecture are ruins ofbrick andrammed earth walls (including aboveground city walls and underground tomb walls), rammed earth platforms for terraced altars and halls, funerary stone or brick pillar-gates, and scatteredceramic roof tiles that once adorned timber halls.[123] Sections of the Han-era rammed earthGreat Wall still exist inGansu province, along with the Han frontier ruins of thirtybeacon towers and two fortifiedcastles withcrenellations.[124] Han walls of frontier towns and forts inInner Mongolia were typically constructed with stamped clay bricks instead of rammed earth.[125]
Thatched or tiled roofs were supported by wooden pillars, since the addition of brick, rammed earth, or mud walls of these halls did not actually support the roof.[120] Stone andplaster were also used for domestic architecture.[120] Tiled eaves projecting outward were built to distance falling rainwater from the walls; they were supported bydougong brackets that were sometimes elaborately decorated.[120] Molded designs usually decorated the ends of roof tiles, as seen in artistic models of buildings and in surviving tile pieces.[126]
Valuable clues about Han architecture can be found in Han artwork of ceramic models, paintings, and carved or stamped bricks discovered in tombs and other sites.[120] The layout of Han tombs were also built like underground houses, comparable to the scenes ofcourtyard houses found on tomb bricks and in three-dimensional models.[120] Han homes had a courtyard area (and some had multiple courtyards) with halls that were slightly elevated above it and connected by stairways.[120] Multi-story buildings included the main colonnaded residence halls built around the courtyards as well aswatchtowers.[120] The halls were built with intersecting crossbeams and rafters that were usually carved with decorations; stairways and walls were usually plastered over to produce a smooth surface and then painted.[127]
The ruins of the walls of Han's first capitalChang'an still stand today at 12 m (39 ft) in height with a base width of 12 to 16 m (39 to 52 ft).[128] Modern archaeological surveys have proven that the eastern wall was 6,000 m (20,000 ft) long, the southern wall was 7,600 m (24,900 ft) long, the western wall was 4,900 m (16,100 ft) long, and the northern wall was 7,200 (23,622 ft) long.[128] Overall the total length of walls equalled 25,700 m (84,300 ft), and formed a roughly square layout (although the southern and northern walls had sections whichzigzagged due to topographical concerns: rough terrain existed along the southern wall and the course of theWei River obstructed the straight path of the northern wall).[128] The city'smoat was 8 m (26 ft) wide and 3 m (9.8 ft) deep; the remains of what were wooden bridges have been discovered along the moat.[129] Chang'an had twelvegatehouses leading into the city, three for each side of the wall, and acted as terminus points for the main avenues.[130] Every gatehouse had three gateway entrances that were each 6 m (20 ft) wide; Han-era writers claimed that each gateway could accommodate the traffic of four horse-drawn carriages at once.[130]The drainage system included many drainholes that were dug under these gates and lined with bricks that form arches, where ceramicwater pipes have been found that once connected to the ditches built alongside the major streets.[131] Only some wall sections and platform foundations of the city's once lavish imperial palaces remain.[132] Likewise, the stone foundations of the armory were also discovered, but its wooden architecture had long since disappeared.[132]
Some sections of the wall ruins of Han's second capitalLuoyang still stand at 10 m (33 ft) in height and 25 m (82 ft) in width at the base.[133] The eastern wall was 3,900 m (12,800 ft) long, the western wall was 3,400 m (11,200 ft) long, and the northern wall was 2,700 m (8,900 ft) long, yet the southern wall was washed away when theLuo River changed its course centuries ago; by using the terminus points of the eastern and western walls, historians estimate that the southern wall was 2,460 m (8,070 ft) long.[134] The overall walled enclosure formed a rectangular shape, yet with some disruptive curves due to topographical obstructions.[134] Like Chang'an, Luoyang had twelve gatehouses, three for each side of the wall, while each gatehouse had three gateway entrances which led to major avenues within the city.[135] The rammed earth foundational platforms of religious altars and terraces still stand today outside of the walled perimeter of Luoyang,dedicated to the worship of deities and where state sacrifices were conducted.[136] They were approached by long ramps and once had timber halls built on top with verandas on the lower levels.[136]
By the 1980s, over ten thousand brick-and-stone underground Han tombs had been discovered throughout China.[137] Earlier Chinese tombs dating to the Warring States were often vertically dug pits lined with wooden walls.[138] In digging the tomb sites, Han workers would first build vertical pits and then dig laterally, hence the name "horizontal pits" for Han tombs; this method was also used for tomb sites dug into the sides of mountains.[137] The walls of most Western Han tombs were built of large hollow bricks while the smaller, non-hollow brick type that dominated Eastern Han tomb architecture (with some made out of stone) appeared in the late Western Han.[139] The smaller brick type was better-suited for Han tombarchways at entrances,vaulted chambers, anddomed roofs.[140] Underground vaults and domes did not require buttress supports since they were held in place by earthen pits.[141] The use of brick vaults and domes in aboveground Han structures is unknown.[141]
The layout of tombs dug into the sides of mountains typically had a front chamber, side chambers, and a rear chambers designed to imitate a complex of aboveground halls.[138] The tomb of KingLiu Sheng (d. 113 BCE) inHebei province not only had a front hall with window drapes and grave goods, carriages and horses in the southern separate side chamber, and storage goods in the northern side chamber, but also the remains of real timber houses with tiled roofs erected within (along with a house made of stone slabs and two stone doors in the rear chamber).[138] Doors made completely out of stone were found in many Han tombsas well as tombs in later dynasties.[142]
A total of twenty-nine monumental brick or stone-carved pillar-gates (que) from the Han dynasty have survived and can be found in the aboveground areas around Han tomb and shrine sites.[143] They often formed part of outer walls, usually flanking an entry but sometimes at the corners of walled enclosures.[144] Although they lack wooden and ceramic components, they feature imitation roof tiles, eaves, porches, andbalustrades.[145]
On Han tomb brick reliefs ofSichuan province, scenes ofborehole drilling formining projects are shown.[146] They show toweringderricks lifting liquidbrine throughbamboo pipes to the surface so that the brine could bedistilled in evaporation pans over the heat of furnaces and producesalt.[146] The furnaces were heated bynatural gas brought by bamboo pipes, with gas brought up from 610 m (2,000 ft) below the surface.[146] The drill bit for digging boreholes was operated by a team of men jumping on and off a beam while the boring tool was rotated by a draft animal, usually oxen orwater buffaloes.[147] Han boreholes dug for collecting brine could reach hundreds of meters (feet) beneath the Earth's surface.[148]Mining shafts dating to the Han dynasty have been found which reach depths of hundreds of meters (feet) beneath the earth, complete with spacious underground rooms structured by timber frames along with ladders and iron tools left behind.[149]
There are Han-era literary references to tall towers found in the capital cities; they often served as watchtowers, astronomicalobservatories, and religious establishments meant to attract the favor ofimmortals.[150] The court eunuchsZhao Zhong andZhang Rang discouraged the aloofEmperor Ling of Han (r. 168–189 CE) from ascending to the top floors of tall towers (claiming it would cause bad luck), in order to conceal from him the enormous palatial mansions the eunuchs built for themselves in Luoyang.[151] It is not known for certain whether or not miniature ceramic models of residential towers and watchtowers found in Han-dynasty tombs are completely faithful representations of such timber towers, yet they reveal vital clues about lost timber architecture.[152]
There are only a handful of existing ceramic models of multi-story towers from pre-Han and Western Han eras; the bulk of the hundreds of towers found so far were made during the Eastern Han period.[152] Model towers could be fired as one piece in the kiln or assembled from several different ceramic pieces to create the whole.[153] No one tower is a duplicate of the other, yet they share common features.[153] They often had a walled courtyard at the bottom, a balcony with balustrades and windows for every floor, roof tiles capping and concealing the ceilingrafters, human figures peering out the windows or standing on the balconies,door knockers, andpets such as dogs in the bottom courtyard.[154] Perhaps the most direct pieces of evidence to suggest that miniature ceramic tower models are faithful representations of real-life Han timber towers are tile patterns.[155] Artistic patterns found on the circular tiles that cap the eave-ends on the miniature models are exact matches of patterns found on real-life Han roof tiles excavated at sites such as the royal palaces in Chang'an and Luoyang, and even the tiles of the originalWhite Horse Temple.[155]
Besides towers, other ceramic models from the Han reveal a variety of building types. This includes multi-storystorehouses such asgranaries, courtyard houses with multi-story halls,kiosks, walled gate towers, mills, manufactories andworkshops, animal pens,outhouses, and water wells.[156] Even models of single-storyfarmhouses show a great amount of detail, including tiled roofs, courtyards, steps leading to walkways, farmyards with troughs and basins, parapets, and privies.[157] Models of granaries and storehouses had tiled rooftops,dougong brackets, windows, and stilt supports raising them above ground level.[158] Han models of water wells sometimes feature tiny tiled roofs supported by beams that house the ropepulley used for lifting the bucket.[159]
In order to facilitate commerce and communication as well as speed the process of tax collection and movement of military troops, the Han government sponsored the building of new roads, bridges, andcanal waterways.[160] These include repairs and renovation work on theDujiangyan Irrigation System ofSichuan andZhengguo Canal ofShaanxi, both of which were built by the previousState of Qin.[38] Accepting the proposal ofNi Kuan, in 111 BCE Emperor Wu commissioned Er to lead the project of creating extensions to the Zhengguo Canal that could irrigate nearby terrain elevated above the main canal.[161] Since a large amount ofsilt had built up over time at the bottom of the Zhengguo Canal (causing flooding), in 95 BCE another project was initiated to tap irrigation waters from further up the Jing River, requiring the dredging of a new 100 km (62 mi) long canal following acontour line above the Zhengguo.[161] The Han state also maintained a system of dikes to protect farmland from seasonal floods.[162]
Roadways, wooden bridges, postal stations, and relay stations were occasionally repaired, while many new facilities such as these were established.[163] As written by Han authors, roads built during the Han were tamped down with metal rammers, yet there is uncertainty over the materials used;Joseph Needham speculates that they were rubble and gravel.[164] The widths of roads ranged from narrow footpaths where only a single horse or oxen could pass at once to large highways that could accommodate the simultaneous passage of nine horse-drawn chariots abreast.[165] Fortified Han roadways were built as far west asShanshan (Loulan) near theLop Desert, whileHan forces utilized routes that traversed north of theTaklamakan Desert towardsKashgar.[166] A vast network of roads, fortified passes, and wooden bridges built over rushing torrents in steep gorges of theQin Mountains was consolidated during the Han, known as thegallery roads.[167] During the reign of Emperor Wu, roads were built to connect newly conquered territories in what is nowYunnan in the far southwest as well as theKorean Peninsula in the far northeast.[168]
One of the most common bridge-types built during the Han was the wooden-trestlebeam bridge, described by literary sources and seen in reliefs carved on tomb bricks.[169] Evidence forarch bridges is elusive: one outside ofChengdu's south gate is claimed to date to the Han period, while that built by Ma Xian (Chinese:馬賢) (fl. 135 CE) was certainly a beam bridge.[170] A relief sculpture from a Han tomb in Sichuan province shows an arch bridge with a gradual curve, suggesting that it is segmental, although the use of such bridges are not entirely confirmed.[171] Although there are rare references tosimple suspension bridges in Han sources, these are only mentioned in connection with travels to foreign countries in theHimalaya,Hindukush andAfghanistan, demonstrating the antiquity of the invention there.[172] Floatingpontoon bridges made of boats secured by iron chains were built during the Han (some even spanning theYellow River andYangzi River) and were most often employed for military purposes since they could be easily assembled and then disassembled.[173]
Much of the beliefs held by Han-era physicians are known to modern historians through such texts as theYellow Emperor's Inner Canon (Huangdi neijing) medical corpus, which was compiled from the 3rd to 2nd century BCE and was mentioned in theBook of Later Han.[174] It is clear from this text and others that their metaphysical beliefs in thefive phases andyin and yang dictated their medical decisions and assumptions.[175] The Han-era Chinese believed that eachorgan in the body was associated with one of the five phases (metal 金, wood 木, water 水, fire 火, earth 土) and had two circulatory qi channels (Chinese:任督二脉).[174] If these channels were disrupted, Han medical texts suggest that one should consume an edible material associated with one of these phases that would counteract the organ's prescribed phase and thus restore one's health.[174] For example, the Chinese believed that when the heart—associated with the fire phase—caused one to become sluggish, then one should eat sour food because it was associated with the wood phase (which promoted fire).[174] The Han Chinese also believed that by usingpulse diagnosis, a physician could determine which organ of the body emitted "vital energy" (qi) and what qualities the latter had, in order to figure out the exact disorder the patient was suffering.[176] Despite the influence of metaphysical theory on medicine, Han texts also give practical advice, such as the proper way to performclinical lancing to remove anabscess.[177] TheHuangdi neijing noted the symptoms of people with various diseases of the liver, heart, spleen, lung, or kidneys in a 24-hour period, which was a recognition ofcircadian rhythm, although explained in terms of the five phases.[178]
In hisEssential Medical Treasures of the Golden Chamber (Jinkui yaolue),Zhang Zhongjing (c. 150 – c. 219 CE) was the first to suggest a regulated diet rich in certainvitamins could preventdifferent types of disease, an idea which ledHu Sihui (fl. 1314–1330) to prescribe a diet rich inVitamin B1 as a treatment forberiberi.[179] Zhang's major work was theTreatise on Cold Injury and Miscellaneous Disorders (Shanghan zabing lun).[180]Hua Tuo (d. 208 CE) was a physician who had studied theHuangdi neijing and became knowledgeable inChinese herbology.[181] Hua Tuo usedanesthesia on patients duringsurgery and created an ointment that was meant to fullyheal surgery wounds within a month.[181] In one diagnosis of an ill woman, he deciphered that she bore a deadfetus within her womb which he then removed, curing her of her ailments.[181]
Historical sources say that Hua Tuo rarely practicedmoxibustion andacupuncture.[181] The first mentioning of acupuncture in Chinese literature appeared in theHuangdi neijing.[182] Acupuncture needles made of gold were found in the tomb of the Han KingLiu Sheng (d. 113 BCE).[183] Some stone-carved depictions of acupuncture date to the Eastern Han Era (25–220 CE).[183] Hua Tuo also wrote about the allegedly life-prolonging exercises ofcalisthenics.[181] In the 2nd-century-BCE medical texts excavated from theMawangdui, illustrated diagrams of calisthenic positions are accompanied by descriptive titles and captions.[184] Vivienne Lo writes that the modern physical exercises oftai chi andqigong are derived from Han-era calisthenics.[185]
Map-making in China preceded the Han dynasty. Since two 4th-century-BCE silk maps from theState of Qin (found inGansu, displaying the region about theJialing River) showthe measured distance between timber-gathering sites, Mei-ling Hsu argues that these are to be considered the first knowneconomic maps (as they predate the maps ofthe Roman geographerStrabo, c. 64 BCE – 24 CE).[186] Maps from the Han period have also been uncovered by modern archaeologists, such as those foundwith 2nd-century-BCE silk texts atMawangdui.[186] In contrast to the Qin maps, the Han maps found at Mawangdui employ a more diverse use of map symbols, cover a larger terrain, and display information on local populations and even pinpoint locations of military camps.[187] One of the maps discovered atMawangdui shows positions ofHan military garrisons which were to attackNanyue in 181 BCE.[188]
InChinese literature, the oldest reference to a map comes from 227 BCE.[189] TheRites of Zhou (Zhouli), compiled during the Han and commented by Liu Xin in the 1st century CE, mentioned the use of maps for governmental provinces and districts, principalities, frontier boundaries, and locations of ores and minerals for mining facilities.[189] The first Chinesegazetteer was written in 52 CE and included information on territorial divisions, the founding of cities, and local products and customs.[190]Pei Xiu (224–271 CE) was the first to describe in detail the use of agraduated scale andgeometrically plotted reference grid.[191] However, historians Howard Nelson, Robert Temple, andRafe de Crespigny argue that there is enough literary evidence that Zhang Heng's now lost work of 116 CE established the geometric reference grid in Chinese cartography (including a line from theBook of Later Han: "[Zhang Heng] cast a network of coordinates about heaven and earth, and reckoned on the basis of it").[192] Although there is speculation fueled by the report in Sima'sRecords of the Grand Historian that a giganticraised-relief map representing the Qin Empire is located within the tomb of Qin Shi Huang, it is known that small raised-relief maps were created during the Han dynasty, such as one made out of rice by the military officerMa Yuan (14 BCE – 49 CE).[193]
In 1975, an ancientshipyard discovered inGuangzhou is now dated to the late 3rd century BCE, made during either theQin dynasty (221–206 BCE) or early Western Han dynasty.[29] It had three large platforms capable of building wooden ships that were 30 m (98 ft) long, 8 m (26 ft) wide, and had a weight capacity of 60 metric tons.[29] Another Han shipyard in what is nowAnhui province had a government-operated maritime workshop where battle ships were assembled.[194] The widespread use of iron tools during the Han dynasty was essential for crafting such vessels.[29]
Thesouthward expansion of the Han dynasty led to new trade routes and diplomatic contact with foreign kingdoms. In 111 BCE, Emperor Wuconquered the Kingdom ofNanyue in what is now modernnorthern Vietnam andGuangdong,Guangxi,Yunnan; thereafter he opened up maritime trade to bothSoutheast Asia and theIndian Ocean, as foreign merchants broughtlapis lazuli,pearls,jade, andglasswares to the Han Empire.[195] When a group of travelers from theRoman Empire (allegedly diplomats ofMarcus Aurelius but most likelyRoman merchants)came to the Han court in 166 CE, they allegedly came from this southern trade route.[196] By at least the 1st century CE—as proven by Eastern Han ceramic miniature models of ships found in various tombs—the Chinese would have been able to brave distant waters with the newsteering invention of the stern-mountedrudder. This came to replace the less efficientsteering oar.[197] While ancient China was home to various ship designs, including the layered and fortifiedtower ship meant for calm waters of lakes and river, thejunk design (jun 船) created by the 1st century was China's first seaworthy sailing ship.[198] The typical junk has a square-endedbow andstern, a flat-bottomedhull orcarvel-shaped hull with nokeel orsternpost, andsolid transverse bulkheads in the place ofstructural ribs found in Western seacrafts.[199] Since the Chinese junk lacked a sternpost, the rudder was attached to the back of the ship by use of either socket-and-jaw orblock and tackle (which differed from the later Europeanpintle andgudgeon design of the 12th century).[200] According to a 3rd-century author, junks hadfor-and-aft rigs andlug sails.[201]
Although horse and ox-drawncarts and spoke-wheeledchariots had existed in China long before the Han dynasty, it was not until the 1st century BCE that literary evidence pointed to the invention of thewheelbarrow, while painted murals on Han tomb walls of the 2nd century CE show the wheelbarrow in use for hauling goods.[202] While the 'throat-and-girth' harness was still in use throughout much of the ancient world (placing an excessive amount of pressure on horses' necks), the Chinese were placing a wooden yoke across their horses' chests with traces to the chariot shaft by the 4th century BCE in theState of Chu (as seen on a Chulacquerware).[203] By Han times, the Chinese replaced this heavy yoke with a softer breast strap.[204] In the final stage of evolution, the modernhorse collar was invented in China by the 5th century, during theNorthern Wei period.[205]
The pivotcatapult, known as the tractiontrebuchet, had existed in China since theWarring States period (as evidenced by theMozi).[206] It was regularly used during the Han dynasty by both besiegers and the besieged.[206] The most common projectile weapon used during the Han dynasty was the small handheld, trigger-activatedcrossbow (and to a lesser extent, therepeating crossbow), invented in China during the 6th or 5th century BCE.[207]
The Han Chinese also employedchemical warfare. In quelling a peasant revolt nearGuiyang in 178 CE, the imperial Han forces had horse-drawn chariots carryingbellows that were used to pump powdered lime (calcium oxide) at the rebels.[208] They also litincendiary rags tied to the tails of horses, so that the frightened horses would rush through the enemy lines and disrupt their formations.[208]
To deter pursuits of marching infantry or riding cavalry, the Han Chinese madecaltrops (barbed iron balls with sharp spikes sticking out in all directions) that could be scattered on the ground and pierce the feet or hooves of those who were unaware of them.[28]
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