When is the longest night?

During the winter solstice, the days in the northern hemisphere are the shortest and the nights are the longest, while the southern hemisphere is the opposite.

The winter solstice is the 22nd solar term in the "24 solar terms", and the solar calendar reaches 270 degrees. Every year, the festival is held on 65438+February 2 1-23 in the Gregorian calendar. The solstice in winter is the extreme point of direct sunlight spreading to the south. From winter to the sun, the sun shines directly on the tropic of Capricorn, and the sun is most inclined to the northern hemisphere, and the elevation angle of the sun is the smallest. In all parts of the northern hemisphere, the days are the shortest and the nights are the longest.

The solstice in winter is also the turning point of direct sunlight returning to the north. After this day, it went back, and the direct sunlight began to move northward from the Tropic of Capricorn (23 26' s), and the sunlight in the northern hemisphere (China is located in the northern hemisphere) increased day by day.

Extended data:

In winter solstice, although the sun is low and the days are short, the temperature in winter solstice is not the lowest in meteorology. In fact, because there is still "accumulated heat" on the surface, it is usually not very cold before the winter solstice, and the real cold is after the winter solstice.

Because of the huge climate difference in China, this climatic winter is obviously late for most parts of China. The winter solstice marks the beginning of the cold season, and people begin to count to nine to calculate the cold weather (folk proverb: "The summer solstice is the third watch, and the winter solstice is the ninth watch").