Science and technology of the Han dynasty

The Han dynasty (206 BC – 220 AD) of ancient China, divided between the eras of Western Han (206 BC – 9 AD, when the capital was at Chang'an), Xin dynasty of Wang Mang (r. 9–23 AD), and Eastern Han (25–220 AD, when the capital was at Luoyang, and after 196 AD at Xuchang), witnessed some of the most significant advancements in premodern Chinese science and technology.

There were great innovations in metallurgy. In addition to Zhou-dynasty China's (c. 1050 BCE – 256 BC) previous inventions of the blast furnace and cupola furnace 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.

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