The Big Dipper is the division of astronomical observations in ancient China!
Beidou is composed of seven stars: Tianshu, Tianxuan, Tianji, Tianquan, Yuheng, Kaiyang and Yaoguang. The ancient Han people connected these seven stars and imagined them to be in the shape of an ancient bucket for ladling wine.
The Big Dipper will appear in different directions in the northern hemisphere sky in different seasons and at different times of the night, so the ancients determined the seasons based on the direction in which the handle of the dipper pointed at dusk. The ancient book "He Guanzi" records: If the bucket handle points to the east, it will be spring all over the world; if the bucket handle points to the west, it will be autumn all over the world; if the bucket handle points to the west, it will be autumn all over the world; if the bucket handle points to the north, it will be winter all over the world. The alternation of seasons is closely related to the "yellow-red angle". The yellow-red angle is the fundamental reason for the changes in the four seasons and the distinction between the five zones on the earth. It affects the natural geographical phenomena that are closely related to it. Ancient people could guide agricultural production to the right time according to the direction of the Big Dipper in the night sky. There is an old saying, "You can know north and south by looking at the Big Dipper at night."