Why are the latest sunrise and the earliest sunset not on the winter solstice, and the earliest sunrise and sunset not on the summer solstice?
But in fact, due to the influence of the ecliptic angle and the elliptical orbit of the earth, the earliest sunset will not fall on the winter solstice, but in early February. The latest time of sunset will not fall on the summer solstice, but at the end of June.
Even in the equatorial region, the time of sunrise and sunset will change a little throughout the year, and these changes can be expressed by daily trajectories. By tracking the trajectory of the sun, the time of sunrise and sunset can be calculated. In addition, sunlight will be refracted by the influence of the earth's atmosphere, so the sun can still be seen after it drops below the horizon, which is an illusion generated at sunset every day.
Extended data
The solstice of winter is about to enter the cold season, so people begin to count nine to calculate the cold days. Counting nine is a folk method to calculate the date of cold and hot summer in China. As the folk proverb says, "The solstice in summer is three years old, and the solstice in winter is nine years old."
The number nine is counted from the winter solstice, every nine days is counted as a "nine", and so on. Generally speaking, "March 9 and April 9" are the coldest times of the year. When you count to nine "nine days" (998 1 day), spring will be deep and warm, and everything will be full of vitality. It's time for spring ploughing.
The number nine method is passed down from mouth to mouth among the people in our country, which has a history and lacks records. As for when it originated, there is no exact information. The number nine is the experience summarized by the ancients on the basis of generations of production and life practice, using some ecological reflections and weather signs in nature.
In the course of historical development, people all over the country have also compiled various proverbs, ballads and jingles according to different climatic conditions, scenic features, agricultural phenology and customs. There are several nine songs all over the country, but the lyrics are slightly different.