Why are the days short and the nights long in winter?

This is a natural phenomenon caused by the earth's rotation and revolution. There is an included angle of more than 60 degrees between the rotation axis of the earth and the orbit of revolution. In summer, the sun shines on the Tropic of Cancer. In the northern hemisphere, the illumination time is long, the day is long and the night is relatively short. In winter, the sun shines on the tropic of Capricorn, and the days are long and the nights are short in the southern hemisphere.

China is in the northern hemisphere, but now spring has not reached the "vernal equinox" among the 24 solar terms. The days are getting longer and the nights are getting shorter and shorter. When the "vernal equinox" has passed, then day and night are almost as long, and in the future, day will be longer than night.

To the "summer solstice" solar term, it is the longest day and the shortest night in a year; The "autumnal equinox" solar term begins, and the day is as long as the night; When eating jiaozi during the "winter solstice", the days are the shortest and the nights are the longest. Then there is the vernal equinox, which repeats year after year, so there is a change in the length of day and night.

Extended data:

Pay attention to the naming of the 24 solar terms.

Twenty-four solar terms reflect the apparent movement of the sun in one year, so the dates of solar terms are basically fixed in the current Gregorian calendar, with the first half of the year being 6 days and 2 1, and the second half being 8 days and 23 days, with a difference of 1 ~ 2 days.

"Li" is the beginning of all seasons, and four "Li" in spring, summer, autumn and winter are the beginning of four solar terms.

Beginning of spring, Changsha, beginning of autumn and beginning of winter are also called "four seasons". The Gregorian calendar is generally around February 4th, May 5th, August 7th and165438+1October 7th every year. "Li Si" indicates the beginning of the astronomical season. As far as climate is concerned, it is still in the last season. For example, the Yellow River Basin in early spring is still in the middle of winter.

"Zhi" means extreme and most. The summer solstice and the winter solstice are called "the second solstice", which indicates the arrival of summer and winter. Summer solstice and winter solstice are generally on June 2 1 day and February 22 12 of the Gregorian calendar every year. On the summer solstice, the direct sunlight is 23.5 degrees north latitude and 90 degrees yellow longitude, which is the longest day in the northern hemisphere. On the solstice in winter, the direct sunlight is 23.5 degrees south latitude and 270 degrees yellow longitude, and the daytime in the northern hemisphere is the shortest.

"Points" here means equal distribution. The vernal equinox and autumnal equinox are called "equal share", which means that the length of day and night is equal. These two solar terms are generally around March 20 and September 23 of the Gregorian calendar every year. At the vernal equinox and autumnal equinox, the ecliptic intersects the equatorial plane. At this time, the ecliptic is 0 degrees and 180 degrees respectively, and the sun shines directly on the equator, and day and night are equal.

Baidu encyclopedia-24 solar terms in lunar calendar