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Compass

The compass is one of the great inventions in Chinese history and a major contribution of China to the development of world civilization. A compass is a pointing instrument made by using the north-south polarity of a magnet in the earth's magnetic field. The picture above is the Sinan model.

This characteristic of magnets was used by ancient people to make guide tools. The earliest guide was called Sinan, which was widely used during the Warring States Period. It is made of natural magnets and looks like a spoon. The center of gravity is in the center of the bottom. The chassis is smooth and engraved with twenty-four directions on all sides. When using it, place the long spoon on the chassis and gently push it with your hands to make it rotate and stop. The long handle at the back points to the south. Wang Chong of the Eastern Han Dynasty (Lunheng. Shiying Chapter) recorded its shape and usage. (Guiguzi. Plan) also talks about the people of Zheng going to a distant place to pick jade, so they took Sinan with them to avoid losing their way. In addition, the invention of the compass further elevated this instrument to a higher level. The pictures below are an imaginary drawing of a guide fish and a restored model of a compass-type compass.

However, the finished product of Sinan, which is made of natural magnets, is low and the magnetism is weak. In the Song Dynasty, people invented the artificial magnetization method and produced compasses and compasses. The compass was simpler and more practical. It is made of natural magnet friction steel needle, which maintains the compass function under the action of geomagnetism. Later, when it is installed on the azimuth plate, it is called a compass. This is a big leap in the history of compass development. The picture below is a navigation compass used in the Qing Dynasty.

Shen Kuo also made detailed research on the compass placement method, summarized four different methods and made a comparison:

First, the water float method. The compass was floated on the water to indicate the direction. As for the specific method, Shen Kuo did not explain. It was not until the late Northern Song Dynasty that pharmacologist Kou Zong's (Compendium of Materia Medica: Magnet Strips) introduced it. It turned out that by putting rushes on the compass, the needle could float. The disadvantage of the water float method is that the magnetic needle will sway with the water.

Two, nail rotation method. Putting the magnetic needle on the nail can move flexibly, but the disadvantage is that it easily slips off.

Third, bowl lip rotation method. If the magnetic needle is placed on the edge of the bowl, it can rotate freely, but it is also easy to fall.

Fourth, hanging wire method. Take a new piece of cotton silk, stick it to the center of the magnetic needle with a little wax, and hang it in a windless place. The magnetic needle can indicate the direction.

In comparison, Shen Kuo believes that this method is the most ideal. The figure below shows the four experimental restoration designs of Shen Kuo's compass.

The compass was already a commonly used directional instrument in the 11th century AD. The greatest contribution of the compass is to greatly promote the development of navigation. According to research, the compass began to be used for navigation at the end of the 11th century AD. Around the end of the 12th century and the beginning of the 13th century, the compass was introduced to Arabia by sea, and then to Europe from Arabia.

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