Why is the winter solstice the shortest day and the longest night?

Because the sun shines directly on the tropic of Capricorn from winter to the future, the sun moves south, and the sunlight depends on the position of the sun. As the sun moves northward in winter, the direct point of the sun will also move northward, so China is in the northern hemisphere, so the days are short and the nights are long in winter.

Because the earth's axis is inclined, the length of day and night varies in different parts of the earth. At the north and south poles of the earth, the sun is oblique all year round, and the length of day and night changes the most.

In the high latitudes of the northern and southern hemispheres, there will be a phenomenon that the sun never sets or stays out all day, that is, 24 hours a day is day or night, which is the polar "extreme day" and "extreme night" phenomenon. In the north and south poles, there are extreme days and nights for half a year.

Extended data:

Climatic characteristics:

The arrival of winter solstice solar terms marks the beginning of winter. On this day, although the northern hemisphere received the least solar radiation, it was about 50% less than the southern hemisphere. However, this is not the coldest time, so-called "March 9, April 9 cold." This is because there is atmosphere and water on the surface of the earth, which can store heat, not "save or lose" but "accumulate heat"

Therefore, the weather is usually not very cold before the winter solstice. From winter to the future, although the solar altitude angle gradually increases, it is a slow recovery process, and the heat lost every day is still greater than the heat received, showing a situation of "making ends meet".

On the day of "March 9 and April 9", the accumulated heat is the least, the temperature is the lowest, and the weather is getting colder and colder. If there is the influence of cold air at this time, the weather will be even colder. After this "cold front", the weather will gradually get warmer.