Polaris can point to the north. Didn't Polaris move?

At present, the most commonly used method is to find the bright Big Dipper in the night sky, and then connect the two stars "Tian Xuan" and "Shu Tian" at the end of the "spoon" of the Big Dipper, and extend the position five times to point to the star, which is the North Star. Of course, because of the movement of the stars, the Big Dipper is not always spoon-shaped, but it takes a long time, so it is enough to remember the spoon at this stage. The brightness of Polaris is not in the front row in the night sky, but it is clear enough to show people the north perfectly.

Why can Polaris accurately indicate the north for mankind? This is mainly because the earth rotates around a virtual "earth axis". The extension line at the northern end of this earth axis points to a star, and the general orientation of this star is the north. Although the earth keeps going around the sun, its relative position with Polaris will change theoretically.

But the distance between the sun and the earth, relative to the distance between the earth and Polaris hundreds of light years, is too small to be ignored. For thousands of years, humans have used Polaris to point the way in the wild and in navigation. Even in modern times, it can be used for stargazing, astrophotography and precise positioning of the equatorial plane.

In ancient times, Polaris was fixed because of its position. Seen from the north of the earth, the stars always revolve around it. It is the center of everything, so it is regarded as the symbol of the emperor, also known as the emperor star. In modern times, it is also used to symbolize unswerving love.

Why does Polaris take turns to sit in the village? The earth keeps rotating around its axis, but this axis, which is not fixed at one end, rotates in the same place. Just like a spinning top, it has a deflection angle to draw a circle, but the period of drawing this circle is very long. The sky pointing to the north pole of the earth's rotation axis moves at the speed of 15 arc seconds per year, and it takes about 25,800 years to complete a circle.

When the original Polaris is gradually farther away from the North Pole of the earth than another planet because of the deflection of the earth's axis, it will be replaced. The current Polaris is called Gouchenyi, also known as Alpha Ursa minor, which became the Polaris of mankind in the Ming and Qing Dynasties. In 3000 BC, Polaris was Alpha Draco, and in 1000 BC, Polaris was Beta Ursa minor. In the Sui and Tang Dynasties, 50% of the Arctic was Polaris.

Of course, there are many different Polaris, which changes every few hundred to one thousand years. Let's choose a famous place. The brightness of these stars is not the same. It was very dark at the beginning of the Sui and Tang Dynasties.

In a word, Polaris can point the way for mankind, mainly because it takes too long to change it once every few hundred thousand years. Humans don't need to change their memory in a short time, so it is very easy to use.