The compass was called Sina in ancient times. Its main part includes a magnetic needle mounted on a shaft. At first, it was a spoon. Finally, it was converted into two thin magnetic sheets. Finally, it was converted into a magnetic needle. The direction was measured by the principle that the magnetic needle can freely rotate and remain in the tangential direction of magnetic meridian under the action of natural geomagnetic field, and the north pole of the magnetic needle points to the north pole. It is often used in navigation, geodesy, travel and military affairs. ? According to the Records of Ancient Mines, it first appeared in Cishan area during the Warring States Period.
In the Western Han Dynasty, there was an alchemist named Luan Da, who used the principle that like magnets repel each other and opposites attract each other to make magnets into two pieces. And the phenomenon of same-sex repulsion was called chess fighting. Later, Luan Dafang dedicated this chess fighting to Emperor Wu of Han Dynasty, and personally demonstrated it in front of Emperor Wu of Han Dynasty. Emperor Wu of Han Dynasty felt very novel and named Luan Da General of Wuli. Before the Northern Song Dynasty, China's compass was used in military war, sacrifice and wind and water. The application of military war was first seen in the appearance of the compass in the Yellow Emperor's period. Sacrifice and wind and water were the ancient people's belief that the magnetic field was the pulse, and according to five lines of gossip, the good or bad luck of a region was inferred.
Until the Northern Song Dynasty, due to the commercial development, a large number of merchants began to develop maritime trade. Because they could not tell the direction, the direction was too unstable only by the position of the stars. Therefore, Sina was simplified into a compass and a magnetic needle for maritime trade. Of course, it was still used in military affairs, and the compass was still used for sacrifice and geomantic omen. The appearance of the compass promoted the development of world navigation and made people discover many new continents.
In fact, the function of the compass seems to be mainly used. It's just that most people only know that it is widely used in navigation.
It is also because of the rise of modern navigation that the compass is used more and more in navigation.