When was the compass invented? Was it invented during the Warring States Period or in the Song Dynasty? I want to write about the Warring States period, but I'm afraid he means Sina. When was the compass invented? Among the four great inventions of the Warring States Period, except movable type printing, which was invented in Song Dynasty, all of them were invented long ago.

The following information is provided for your reference: During the Warring States period, people used the characteristics of magnets to refer to the north and south, and made an instrument to distinguish the direction and measure the time, called "Sina", which was a primitive compass. However, because Sina is made of natural magnet, its magnetism is weak, and the friction with the chassis is large when it rotates, so the guiding effect is poor. In the early Northern Song Dynasty, people used artificial magnetization to turn steel sheets into magnets and make compasses. This invention is recorded in the magazine Meng Qian Bi Tan (Volume 24) in Shen Kuo, and four installation methods are introduced (see page 138 of the history teaching book for seventh grade teachers published by Beijing Normal University for details).