When we look at the Polaris, we usually see other stars turning around the North Star, but the North Star is still motionless. Why? Is the Polaris really not moving?
In fact, the rise and fall of the stars is an illusion caused by the rotation of the earth. The earth rotates from west to east around an imaginary axis at a moment. The result of the rotation is the alternation of day and night, and it also causes the stars in our naked eyes to rise and fall. If you extend the imaginary rotation axis infinitely on both sides, then it will intersect with the celestial sphere above our head at two points. The point above the Earth’s north pole is the northern celestial pole, which corresponds to the north; and the point above the earth’s south pole. It is called Nantianji, and the corresponding one is Zhengnan. The east and west of the stars are caused by the rotation of the earth, and the northern celestial pole is the direction of the Earth’s rotation axis. The North Star is less than 1 degree away from the northern celestial pole. Therefore, the illusion is that the stars seem to rotate around the North Star.
In fact, the North Star is not equal to the North celestial pole. The North Star is actually rotating around the North celestial pole along a small circle. But this circle is too small, our naked eyes are usually invisible, so we feel that the Polaris seems to be in the sky. It is always motionless.
