Physics in Ancient China


“The innate laws of things,” physics, are, as the ancients said, “the hows and whys of things.” Knowledge of them was highly valued by the great scholars and renowned officials in the past. The ancient Chinese not only recorded many physical phenomena, they also discovered certain laws or theorems. Knowledge of physics was even passed down to later generations through poetry or other rhymed writing. Strictly speaking, the ancient world had no conception of physics equivalent to our modern one, but this does not mean that physics is not the product of historical development. For more than twenty centuries, ancient Chinese physics has always held a leading position in the world. It was only during the Ming (1368–1644) and Qing (1644–1911) dynasties that modern European physics seemed to eclipse China’s long tradition; some might say the latter was in decline. Starting from the May Fourth New Culture Movement in the early twentieth century, Chinese physics and modern physics converged. 


Ancient Chinese physics has a long history and its principal achievements are embodied in the fields of mechanics, acoustics, electromagnetism, optics, and thermodynamics. Mechanics is the science of studying the laws of motions. An object’s change in time and position is called mechanical movement. The principle of the lever, pulleys, sliding, and wheel-turning were all discovered and invented through the exploration of mechanics. Acoustics studies all sound phenomena, including its use and elimination. Wang Chong (27–ca. 100) was the first scientist to demonstrate sound-waves; he further identified that the intensity of sound was related to the distance the waves traveled. During the Eastern Han period (25–220), about the first century, Wang Chong in the “Bian xu” chapter (Falsity of catastrophic changes) of his Lun heng (Balanced discourses) pointed out that the propagation of sound in the air is the same as in the water. Using as an example the water waves stirred up by fish, he explains that just like human sound the intensity of the wave diminishes with the corresponding distance. As early as the Han dynasty, the ancients already knew that although magnets could attract iron, they could not attract copper, tile, or stone. They also knew the phenomenon of magnetic repulsion, and applied such force to leisure activities such as playing chess. Magnets were also used for theft-prevention and military affairs: for example, the main gate of Qin Shihuang’s (First Emperor of Qin, 259–210 BCE) Epang Palace was installed with magnets to prevent thieves wielding iron-instrument from entering. The ancient Chinese discovered static electricity from the experience of distinguishing genuine amber and hawksbill turtle shell from fakes. Ancient pharmacologists noticed that by rubbing the amber with a piece of cloth or one’s palm it would attract bits of straw; this phenomenon was noted as a distinguishing feature of genuine amber. The origin of optics, just like mechanics and thermodynamics, can be traced back to two- or three-thousand years ago. Mozi, (a collection of Mohist teachings), recorded numerous optical phenomena, such as projection, aperture imaging, and plane, convex, and concave mirrors. The Mohist school, founded by Mo Di (ca. 468–376 BCE), achieved great scientific accomplishments in early China. In the Mozi, eight consecutive texts document optical phenomena. As far back as primitive society, people knew how to use fire. They could produce it by drilling wood: using two wood chips and rubbing the ends fiercely. They would place flammables near the point of friction so that when sparks were produced from the wood chips, the flammables would catch fire right away. In the pre-Qin era (times before 221 BCE), people valued the concept of the wuxing (five elements)—metal, wood, water, fire, and earth. Therefore, the view that fire is a substance has a long history. China was the first country in the world to discover and use high-temperature fuels. The development and utilization of coal, fossil oil, and natural gas were often recorded in Chinese ancient documents. 


There are numerous scientific works in ancient China documenting ancient science and technologies; these are just some of them Mozi, “Kaogong ji” (Record of the scrutiny of crafts) of the Zhou li (Rites of Zhou), Huainan wang shu (a.k.a. Huainanzi, King of Huainan), Lun hengMengxi bitan (Dream pool essays), Tiangong kaiwu (The exploitation of the works of nature), and Wuli xiao zhishi (A little knowledge about physics). Among them Tiangong kaiwu by Song Yingxing (1587–ca. 1666) is a comprehensive work, covering all aspects of science and technology. Some foreign scholars have called it “the encyclopedia of technology in the seventeenth century of China.” The author in the book emphasizes that humans should work in harmony with nature, and that human power should cooperate with natural forces. Even today, these works continue to influence the development of the sciences in China.      

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