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What scientific and technological achievements are associated with the Han dynasty?

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Map showing the Han Empire's territory around 100 BCE, shaded in orange, covering much of eastern China and extending westward. The map also marks the boundary of modern China and highlights the Great Wall running along the northern frontier, built for protection against the Huns. Major rivers and the capital, Chang'an (Xi'an), are labeled. — Han dynasty Map showing the extent of the Han empire c. 100 bce.

The Han dynasty (206 BCE–220 CE) was a period of significant scientific and technological progress, as the imperial government actively encouraged advancements to support its administration and cultural development.12

Key achievements include:

Papermaking: Traditionally credited to the court official Cai Lun around 105 CE, the invention of paper provided a superior and more affordable writing surface compared to silk or bamboo.123
Seismology: The polymath Zhang Heng developed an innovative seismograph (or seismoscope). This device used a system of dragons and frogs to detect and register the direction of distant earthquakes.124
Timekeeping: Han scientists utilized water clocks and sundials to measure time with greater precision.12
Mathematics and Astronomy: The era produced foundational works such as the Jiuzhang suanshu (Nine Chapters on the Mathematical Procedures), which remained a classic text for centuries. Additionally, the frequent publication of calendars reflected the dynasty's commitment to astronomical observation.52

These innovations, alongside advancements in lacquerwork and silk production, established a high standard of technology that subsequent Chinese dynasties sought to emulate.12