Talk about the principle and usage of compass.

Compass, also known as compass, is mainly composed of magnetic needles installed on the shaft. Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangent direction of magnetic meridian, and the north pole of the magnetic needle points to the geographical north pole, so the direction can be distinguished by this property. It is often used in navigation, geodesy, tourism and military affairs. The invention of compass with physical direction indication consists of trilogy: Sina, magnetic needle and compass. All belong to China's invention.

Compass is the result of the understanding of the magnetism of objects by the working people of ancient Han nationality in long-term practice. As one of four great inventions of ancient china, its invention has played an inestimable role in the development of human science, technology and civilization. In ancient China, the compass was first used for rituals, etiquette, military affairs and divination, and to determine the orientation when looking at Feng Shui. 1 1 At the end of the century or at the beginning of the 2nd century, China ships began to use compasses for navigation. Zhou Ping can talk in the Northern Song Dynasty: "The shipowner (helmsman) knows geography, watches the stars at night, watches the sun by day, and watches the compass in the dark."

Compass is an all-weather navigation tool applied to navigation, which makes up for the shortcomings of astronomical navigation and geographical navigation and opens a new era in the history of navigation. At the same time, navigation activities further promoted the development of compass.