Demystifying The Black Technology Of Ancient Chinese Navigation-compass (compass)

China and the West have long discovered the mutual attraction, repulsion and iron absorption of magnets. However, the Chinese early used magnets or magnets to point north and south in the geomagnetic field to distinguish the direction.

Sinan was mentioned in the Warring States "Han Feizi" and the Eastern Han Dynasty Wang Chong's "Lunheng" and other documents. Some scholars believe that Sinan was the earliest magnetic pointer made by polishing with natural magnets, and proposed a plan for the restoration of spoon-shaped Sinan and a copper square site, using magnetized tungsten steel and natural magnets to make objects with significant directivity.

Definite evidence of the compass was first seen in the Tang Dynasty from the 9th to the 10th century AD. "Guan's Geographical Guide to Mongolia" mentions that the iron needle can be magnetized to guide north, and it also mentions the declination of the geomagnetic field. The "Nine Heavens Profound Girl Qingnang Cape Sutra" contains the "Floating Needle Fangqi Map", which is the disk map of the water compass.

There are two ways to magnetize the iron needle. The Northern Song Dynasty "Wu Jing Zong Yao" records that fish-shaped thin iron flakes are burnt red, and the head of the fish is clamped with iron tongs and placed in the water to cool in the north-south direction to prepare a water-floating guide fish. The principle is: the coercive force of the iron sheet is reduced after the temperature is raised, and then magnetized by the surface magnetism of the iron clamp head, and post-quenching increases the coercive force to form a higher remanence. Shen Kuo's "Mengxi Bi Tan" talked about the compass made by the geomancy master using a magnet to grind the iron needle. It mentioned four methods of positioning, such as water floatation, suspension, nails, and bowl lips, as well as geomagnetic declination. Zhu Yu's "Pingzhou Ketan" first recorded that the compass was used for navigation.

The compass was first seen in the Southern Song Dynasty. A figurine of Zhang Xianren holding a compass was found unearthed from the Southern Song Dynasty tomb in Linchuan, Jiangxi Province, with a supporting structure on the magnetic needle. "Shi Lin Guang Ji" records that natural magnets and iron needles are installed in wooden turtles and wooden fish, which are supported by brackets and floated in the water as guides. After the Yuan Dynasty, the compass followed the Song system, and most of the existing objects are water compasses, and the disc body is made of painted lacquered wood or bronze.

The compass is hailed as one of China's "Four Great Inventions" that have influenced the world. The development of navigation has created a navigation method. In Europe at the end of the 12th century, the use of magnetic needle navigation has been documented, and this method has been popularized in the 13th century.