How to judge which side of the compass points to the north?

Under the action of natural geomagnetic field, the magnetic needle can rotate freely and keep in the tangential direction of magnetic meridian, and the north pole of the magnetic needle points to the north pole, so the direction can be distinguished by this property.

Compass is the result of China ancient working people's understanding of magnet magnetism 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 geomantic omen.

Extended data:

Magnetic meridian:

Magnetic meridian changes with the seasons.

1. At the vernal equinox and autumnal equinox, magnetic meridian coincides with the meridian and the third meridian of the earth. The compass points directly to the north and south poles of the earth, and the error is only 0.08 axis eccentricity, which can be ignored.

2. In summer solstice and winter solstice, the magnetic meridian and meridian do not coincide, and the magnetic declination is the largest, with the maximum deviation of plus or minus 23.26, that is to say, the magnetic declination is the largest near the north and south poles of the earth. The circumference of the earth divided by the angle of 365 is plus or minus 23, which is equal to the distance between the magnetic deviation point and the north and south poles (plus or minus radian kilometers).

Baidu encyclopedia-compass