Sculpture depicting an early Chinese invention: the magnetic compass. The spoon-shaped needle is also called a lodestone, made from ferrites (magnetic oxides).
The phenomenon of magnetism was discovered in ancient China. That discovery led to development of the compass in China. By the eleventh century the compass was in use in navigation and would be a tremendous aid to ocean-going vessels.
The discovery of magnetism and the development of the compass were among the greatest Chinese contributions to physics. Although references to magnetism in Chinese sources do not date before the third century BCE, knowledge of the phenomenon clearly was widespread by that time, and experiments were being conducted and documented by the first century CE. Many early lodestone (the mineral magnetite possessing polarity) devices existed, such as the “south-pointing spoon” of the first century CE (which may have been invented a century earlier), and there exist several intriguing references to the use of magnets to make “automatic” chessboards.
However, magnetism seems to have been used mainly in geomancy (divination by means of figures or lines or geographic features) until the tenth century. Geomancy (feng shui) was concerned with configuring human dwellings to harmonize with spiritual forces that inhabit them. The fact that knowledge of the compass was reserved for imperial magicians greatly limited its spread, and for many centuries the compass apparently served only as a tool for divination. Even after the compass passed into more general use, the primacy of river and canal traffic slowed the spread of the compass to ocean-going vessels. Nevertheless, many improvements and adaptations occurred in the form of compasses, culminating in their use in navigation by the eleventh century.
Chess and Magnetism
This excerpt from Thai-Phing Yu Lan, ch. 988 is followed by a discussion by China scholar Joseph Needham explaining that very early uses of magnetism can be found in the game of chess.
Take the blood of a cock and mix it with iron (filings) from the grinding of needles, pounding it will lodestone powder. In the day-time, put the paste on the heads of chess-men (chhi) and let it dry in the sun. Then put them on the board and they will constantly bounce against and repel one another.
Several things are noteworthy in the above. Exactly how it was that the magnetized chess-men were “animated” is not clear; they may have been lodestone balls with iron underneath the board, or some of them may have been lodestone while others were iron. Powdered magnetite would have little attractive power. The connection with needles is interesting, and suggests that the demonstration of polarity using needles may really have been older than we thought. But in any case the important thing is the association of the magnet with the men or pieces used in divinatory proto-chess.
Source: Needham, J.. (1962). Science & civilisation in China, Vol IV: 1. London and New York: Cambridge University Press, 316–317.
Two of the most important developments in the evolution of the compass were the use of a needle rather than a lodestone or piece of metal and the discovery of magnetic declination (the deviation between true or geographic north and the direction that a compass needle points). The magnetization of needles was an important step in the evolution of the compass because needles could float or be suspended by a thread and rotate with a great degree of freedom. Also, steel remains magnetized longer than iron, and it was relatively easy at an early date for people to make small needles of steel; compasses with steel needles could be used on long voyages. Steel came to China from India during the fifth century, but the Chinese quickly began to produce their own supplies. Evidence suggests that magnetized needles were used as early as the fourth century CE, and their superiority in the construction of compasses was quickly appreciated.
The discovery of declination also occurred relatively early, sometime between the seventh and tenth centuries. Although the influence of nonscientific divinatory practices was clearly prominent in the development of the compass, much research went into magnetism from the fifth century on.
Further Reading
Needham, J. (1986). Magnetism and electricity. In C.A. Ronan (Ed.), The shorter science and civilisation in China: Vol. 3. Cambridge, U.K.: Cambridge University Press.
Source: Forage, Paul (2009). Magnetism. In Linsun Cheng, et al. (Eds.), Berkshire Encyclopedia of China, pp. 1375–1376. Great Barrington, MA: Berkshire Publishing.
Magnetism (Cíxìng ??)|Cíxìng ?? (Magnetism)
