Because the earth is turning, the starry sky is different every day; Every day the starry sky is four minutes apart, that is, 20: 00 today is the same as 20: 04 yesterday. The average difference between a month and a season is about 2 hours, 1/4 days.
By analogy, the bucket handle of the Big Dipper faces east, south, west and north respectively in spring, summer, autumn and winter;