The winter solstice is the shortest day in a year, and the winter solstice in the northern hemisphere is generally between1February 2 1 day and1February 23, and November is defined by the month of the winter solstice in the lunar calendar.
Around June 2 1 every year (20th ~ 22nd), the sun starts to reach 90 degrees of the yellow meridian. It is the first solar term to be determined. In the 7th century BC, the ancients used Tugui to measure the sun's shadow, and the summer solstice was the shortest day, so it was called the "summer solstice".
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On the summer solstice, the sun shines almost directly on the Tropic of Cancer, and the day is the longest in the northern hemisphere. The sun does not set all day in the Arctic Circle and its northern area, forming the largest polar day area.
After this day, the position of direct sunlight moved to the south, the daytime in the northern hemisphere gradually shortened, and the direction of sunrise and sunset began to move to the south. In the Tropic of Cancer and its north, the height of the sun at noon is also decreasing, and the shadow of the sun is gradually elongated. However, because the energy radiated by the sun to the ground is still much more divergent than that from the ground to the air, the temperature continues to rise in a short time.
According to "New Records of Xiongxian County" in the early years of the Republic of China, the traditional Chinese people would erect eight-foot table trees on the winter solstice to test the flood and drought in the coming year. In the Han dynasty, there was also a standard to judge flood and drought, that is, "water comes when you advance, and drought comes when you retreat."
In addition, Chinese people will observe the changes of clouds and gas at sunrise and sunset on the winter solstice, and judge the weather during the Spring Festival with the prediction of rain and shine. Zhejiang agricultural proverb says: "The winter solstice is sunny and the year is rotten, and the sloppy winter solstice is sunny for the New Year." It means that it won't rain and snow in the winter solstice, but it will rain and snow during the Spring Festival, making the road slippery and muddy; or vice versa, Dallas to the auditorium
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