Unit test The sun shines directly into the Tropic of Cancer. What is the solar term of China?

On the winter solstice, the direct position of the sun on the ground reaches the southernmost point of the year and almost directly reaches the Tropic of Capricorn (23 26' south latitude). On this day, the northern hemisphere gets the least sunshine, 50% less than the southern hemisphere. The days in the northern hemisphere are the shortest, and the farther north they are, the shorter they are. For example, at the southernmost tip of China-Zengmu shoal (2 33' north latitude), the daytime time is 1 1 hour 59 minutes, Haikou time is about1hour 55 minutes, Hangzhou time is about1hour 12 minutes and Beijing time is about 9 hours and 25 minutes. After the winter solstice, the stars in the night sky are completely replaced by the winter stars. From today, they will enter the ninth. At this time, the southern hemisphere is in a hot summer.

Climatic characteristics

Astronomy regards the winter solstice as the beginning of winter, which is obviously late for most parts of China. The solstice in winter is the shortest day in a year. After the winter solstice, the direct point of the sun gradually moves northward, and the days in the northern hemisphere gradually lengthen and the nights gradually shorten. Therefore, there is a saying that "eating the winter solstice makes the day longer."

Climatically, during the winter solstice, the average temperature in the northwest plateau is generally below 0℃, and the southern region is only about 6℃ to 8℃. In addition, the winter solstice begins to count to nine, and the winter solstice becomes the first day to count to nine. As for "Counting Nine", there is a folk song that goes like this: "Don't do it in September, walk on the ice in March and April, watch the willows along the river in May and June, open the river in July and September, geese come in August and September, and cows go everywhere in September and September." However, in the southwest low-altitude valley area, even in the coldest local165438+ in early October, the average temperature is still above 10℃. It can be said that autumn goes and spring comes, and there is no winter all year round.

The ancients in China divided the winter solstice into three stages: "One stage is earthworm knot; Second, wait for the elk horn to solve; Waiting for the spring to gush out. " Legend has it that earthworms are creatures with yin bending and yang stretching. At this time, although the yang has increased, the yin is still very strong, and the earthworms in the soil are still curled up. Elk and deer belong to the same family, but yin and yang are different. The ancients thought that the elk's horns were facing the afterlife, so they were cloudy, and the winter solstice was born in the sun. The elk felt that the yin gradually receded and solved their horns. Because of the birth of yang, the spring water in the mountain can flow and be warm at this time.