Many significant developments in the history of science and technology in China took place during the Han dynasty (202 BCE – 220 CE). The Han period saw great innovations in metallurgy. Following the inventions of the blast furnace and cupola furnace during the Zhou dynasty (256 BCE) to make pig iron and cast iron respectively, the Han period saw the development of steel and wrought iron by use of the finery forge and puddling process. With the drilling of deep boreholes into the earth, the Chinese used not only derricks to lift brine up to the surface to be boiled into salt, but also set up bamboo-crafted pipeline transport systems which brought natural gas as fuel to the furnaces.

Smelting techniques were enhanced with inventions such as the waterwheel-powered bellows; the resulting widespread distribution of iron tools facilitated the growth of agriculture. For tilling the soil and planting straight rows of crops, the improved heavy-moldboard plough with three iron plowshares and sturdy multiple-tube iron seed drill were invented in the Han, which greatly enhanced production yields and thus sustained population growth. The method of supplying irrigation ditches with water was improved with the invention of the mechanical chain 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 operating trip hammers in pounding grain and in rotating the metal rings of the mechanical-driven astronomical armillary sphere representing the celestial sphere around the Earth.

People of the Han Empire initially wrote on hemp-bound bamboo scrolls; by the 2nd century CE, they had invented the papermaking process which created a writing medium that was both cheap and easy to produce. The invention of the wheelbarrow aided in the hauling of heavy loads. The maritime junk ship and stern-mounted steering rudder enabled the Chinese to venture out of calmer waters of interior lakes and rivers and into the open sea. The invention of the grid reference for maps and raised-relief map allowed for better navigation. In medicine, they used new herbal remedies to cure illnesses, calisthenics to keep physically fit, and regulated diets to avoid diseases. Authorities in the capital were warned ahead of time of the direction of sudden earthquakes with the invention of the seismometer that was tripped by a vibration-sensitive pendulum device.

To mark the passing of the seasons and special occasions, the Han used two variations of the lunisolar calendar, which were established due to efforts in astronomy and mathematics. Han-era Chinese advancements in mathematics include the discovery of square roots, cube roots, the Pythagorean theorem, Gaussian elimination, the Horner scheme, improved calculations of pi, and negative 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 as beam bridges, arch bridges, simple suspension bridges, and pontoon bridges. Han ruins of defensive city walls made of brick or rammed earth still stand.

Modern perspectives

Jin Guantao, a professor at the Chinese University of Hong Kong, Fan Hongye, a research fellow with the Chinese 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 the history of premodern Chinese science and technology.Jin, Fan, & Liu (1996), 178–179. They compare it to the incredible pace of scientific and technological growth during the Song dynasty (960–1279). However, they also argue that without the influence of proto-scientific precepts in the ancient philosophy of Mohism, Chinese science continued to lack a definitive structure:

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.

Joseph Needham, a professor from the University of Cambridge and author of the Science and Civilisation in China series, stated that the "Han time (especially the Later Han) was one of the relatively important periods as regards the history of science in China."Needham (1972), 111. He noted the advancements during Han of astronomy and calendrical sciences, the "beginnings of systematic botany and zoology", as well as the philosophical skepticism and rationalist thought embodied in Han works such as the Lunheng by the philosopher Wang Chong.

Writing materials

The most common writing mediums found in archaeological digs from ancient sites predating the Han period are shells and bones as well as bronzewares.Loewe (1968), 89. In the beginning of the Han period, the chief writing mediums were bamboo () and clay tablets, silk cloth, strips of soft wood, and rolled scrolls made of strips of bamboo sewn together with hempen string passed through drilled holes (册) and secured with clay stamps.Tom (1989), 99; Cotterell (2004), 11–13; Loewe (1968), 94–95. The written characters on these narrow flat strips of bamboo were arranged into vertical columns.Loewe (1968), 92–93.

While maps drawn in ink on flat silk cloths have been found in the tomb of the Marquess of Dai (interred in 168 BCE), the earliest known paper map found in China, dated 179–141 BCE and located at Fangmatan, is incidentally the oldest known piece of paper.Buisseret (1998), 12. Chinese hempen paper of the Western Han and early Eastern Han eras was of a coarse quality and used primarily as wrapping paper.Needham (1986e), 1–2, 40–41, 122–123, 228. The papermaking process was not formally introduced until the Eastern Han court eunuch Cai Lun created a process in 105 where mulberry tree bark, hemp, old linens, and fish nets were boiled together to make paper pulp.Tom (1989), 99; Day & McNeil (1996), 122; Needham (1986e), 1–2, 40–41, 122–123, 228. The oldest known piece of paper with writing on it comes from the ruins of a Chinese watchtower at Tsakhortei, Alxa League, Inner Mongolia, dated to 110 CE when the Han garrison abandoned the area following a nomadic Xiongnu attack.Cotterell (2004), 11. By the 3rd century, paper became one of China's chief writing mediums.Needham (1986e), 1–2.

Ceramics

The Han ceramics industry was upheld by private businesses as well as local government agencies.Wang (1982), 146–147. Ceramics were used in domestic wares and utensils as well as construction materials for roof tiles and bricks.Wang (1982), 147–149.

Han dynasty grey pottery—its color derived from the clay that was used—was superior to earlier Chinese grey pottery due to the Han people's use of larger kiln chambers, longer firing tunnels, and improved chimney designs.Wang (1982), 142–143. Kilns of the Han dynasty making grey pottery were able to reach firing temperatures above . 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. Glazed pottery of the Shang () and Zhou ( – 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 , followed by a green-glazed ceramic which became popular in the Eastern Han (25–220 CE).Wang (1982), 143–145.

Wang Zhongshu states that the light-green stoneware known as celadon was thought to exist only since the Three 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.Wang (1982), 145. However, Richard Dewar argues that true celadon was not created in China until the early Song dynasty (960–1279) when Chinese kilns were able to reach a minimum furnace temperature of , with a preferred range of for celadon.Dewar (2002), 42.

Metallurgy

Furnaces and smelting techniques

A blast furnace converts raw iron oxide into iron, which can be remelted in a cupola furnace to produce cast iron. The earliest specimens of cast iron found in China date to the 5th century BCE during the late Spring and Autumn period, yet the oldest discovered blast furnaces date to the 3rd century BCE and the majority date to the period after Emperor 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 merely foundries which recast iron that had been smelted elsewhere).Wagner (2001), 7, 36–37, 64–68; Pigott (1999), 183–184. 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.Wagner (2001), 75–76. Cupola furnaces utilized a cold blast traveling through tuyere pipes from the bottom and over the top where the charge of charcoal and pig iron was introduced. The air traveling through the tuyere pipes thus became a hot blast once it reached the bottom of the furnace.

It was initially believed that Chinese civilization lacked the bloomery, however, bloomeries were discovered in large quantities in regions such as Southwestern China, and bloomery iron actually predominated over blast furnace iron in some places in China.Li, Gaobo; et al. (2026)

The Han Chinese were able to make wrought iron when they injected too much oxygen into the cupola furnace, causing decarburization.Pigott (1999), 177 & 191. The Han-era Chinese were also able to convert cast iron and pig iron into wrought iron and steel by using the finery forge and puddling process, the earliest specimens of such dating to the 2nd century BCE.Wang (1982), 125; Pigott (1999), 186. The semisubterranean walls of these furnaces were lined with refractory bricks and had bottoms made of refractory clay.Wang (1982), 125. Besides charcoal made of wood, Wang Zhongshu states that another furnace fuel used during the Han were "coal cakes", a mixture of coal powder, clay, and quartz.Wang (1982), 126.

Use of steel, iron, and bronze