Why is the winter solstice in the northern hemisphere the shortest day of the year?

From the winter solstice, the direct sunlight position moves northward, and the daylight gradually extends, with an average increase of more than 90 seconds per day.

Winter solstice is a solar term divided by astronomy, which was called "short day" and "short day" in ancient times. From winter to the sun, the sun is located at 270 degrees of the Yellow Meridian, and the sun shines almost directly to the Tropic of Capricorn, which has the shortest day in the northern hemisphere. There is no 10 hour from sunrise to sunset in all parts of our province. From winter to the future, as the earth orbits the sun, the direct sunlight belt gradually moves northward, making the days in the northern hemisphere gradually longer and the nights gradually shorter.

Extended data:

In winter solstice, although the height of the sun is the lowest, the sunshine time is the shortest, and the heat absorbed by the ground is less than the heat lost, the heat accumulated on the ground for a long time continues to be lost, and the temperature near the ground layer has not dropped to the lowest, so it is not the coldest time of the year.

After the winter solstice, although the days are getting longer and shorter, the days are getting shorter and shorter, and the nights are getting longer and longer in the short term. The heat absorbed by the ground every day is still less than the heat lost, so the temperature did not rise immediately.

The masses are used to counting nine from the solstice in winter, and every nine days is a "nine". Before and after "March 9th", the area was the least hot and the weather was the coldest, so it was said that "March 9th was cold".

Astronomy regards the winter solstice as the beginning of winter, which is obviously late for most parts of China. During the winter solstice, the average temperature in the western Sichuan Plateau is generally below 0℃, while the average temperature in the Sichuan Basin is only about 6℃ to 8℃. In the low-altitude valley area of southwest Sichuan, even in the coldest local165438+ in early October, the average temperature is still above 10℃, so it can be said that autumn comes and spring comes, and there is no winter all year round.