How are the 24 solar terms in China divided? Why is it so divided?

The twenty-four solar terms are the summary of thousands of years. In the past, there was a division. The 24 solar terms were divided into 72 periods, that is, each solar term had 15 days, with one period every 5 days and 72 periods in a year. Later, it was found that the division was too fine, because our country is vast and the climatic conditions and topography vary greatly from place to place. If the division is too fine, it may not be easy to use. Finally, it is better to use 24 solar terms. The division of the 24 solar terms is mainly based on the earth's revolution around the sun and its specific position in a year. A year turns to 360, and every 15 is a solar term. In ancient times, there were probably several ways to divide it: for example, about 3,000 years ago, one way was to watch the Big Dipper at dusk and set the solar terms with bucket handle. Bucket handle points to the east as the vernal equinox, to the south as the summer solstice, to the west as the autumnal equinox, and to the north as the winter solstice. There is also a way to row a boat, that is, at dusk, look at what constellation is at the zenith, such as the star at the zenith at dusk, which is called "fire" in ancient books, that is, "Antares", that is, summer has arrived; In addition, if the constellation you see at dusk is the Pleiades, which is now the Pleiades cluster of Taurus in astronomy, it is the winter solstice. The third painting method has just been shown in the film, that is, measuring the shadow with a soil gauge, that is, standing on a pole to see the length of the shadow, and watching the length of the shadow at noon. If the shadow is the shortest, it is the summer solstice; The longest shadow is the winter solstice. There are several ways.

However, these ancient strokes are rough. Today's astronomy can be accurately calculated according to the position of celestial bodies. Therefore, the date of each of the 24 solar terms, especially the start time and moment of the festival, can be calculated strictly and can be calculated long ago. For example, the vernal equinox in 2000, its solar term date is March 2 1, and the time is 3: 06 am, which can be calculated so accurately.

The 24 solar terms in PS are beginning of spring, Rain, Sting, Equinox, Qingming, Grain Rain, Changxia, Xiaoman, Mangzhong, Summer Solstice, Xiaoxia, Daxia, beginning of autumn, Chushu, Bailu, Autumn Equinox, Cold Dew, First Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold. It has two solar terms every month.