practice of the earliest artificial magnetization method in China
The artificial magnetization method of guiding fish in the 11th century of China's book "general essentials of Wujing" is the earliest practice of artificial magnetization method in the world.
The principle of this method is to burn the fish red to increase the kinetic energy of the molecules inside the fish, so that the molecular magnetic domain will change from the original fixed state to the moving state. Then, the iron fish is magnetized by forcing the moving molecular domains to rearrange along the direction of the earth's magnetic field (from irregular to regular) through the strong geomagnetic field; It can be cooled quickly and the regular arrangement of molecular magnetic domains can be fixed. At the same time, it is also a quenching process. Finally, it is possible to place the guide fish next to the natural magnet to keep it magnetized or continue to magnetize. This method of magnetizing steel needles by using the earth's magnetic field is more than 400 years ahead of Europe.