Are the 24 solar terms scientific?

How are the 24 solar terms determined?

The earth revolves around the sun at 5: 48: 46 every 365 days and rotates once every 24 hours. Because the orbital plane of the earth's rotation is not the same as the equatorial plane, but maintains a certain inclination angle, the position of the direct sunlight on the earth is different all the year round. In the northern hemisphere, when the sun is directly at 23.5 degrees north latitude, it is called summer solstice in astronomy; When the sun shines directly at 23.5 degrees south latitude, it is called the winter solstice; The solstice in summer and the solstice in winter mean that it is halfway between summer and winter. Twice a year, when the sun shines directly on the equator, it is the vernal equinox and the autumnal equinox, in the middle of spring and autumn. The day is as long as the night. The solar terms reflecting the changes of the four seasons are: beginning of spring, Spring Equinox, Long Summer, Summer Solstice, beginning of autumn, Autumn Equinox, beginning of winter and Winter Solstice. Among them, beginning of spring, Changsha, beginning of autumn and beginning of winter are called "Li Si", which means the beginning of the four seasons. There are five solar terms reflecting temperature changes: slight summer heat, great summer heat, summer heat, slight cold and severe cold. There are seven solar terms reflecting weather phenomena: rain, Grain Rain, white dew, cold dew, first frost, light snow and heavy snow. There are four solar terms reflecting phenological phenomena: Jing Zhe, Qing Ming, Xiaoman and Mang Zi.

Beginning of Spring

Since the Qin Dynasty, beginning of spring has been the beginning of spring in China. Beginning of spring is divided from astronomy, but in nature and people's minds, spring is warm and flowers are fragrant. Spring is growth, cultivation and sowing. In climatology, spring refers to the period when the average temperature is between 10℃ and 22℃. Speaking of beginning of spring, people obviously feel that the days are getting longer and the sun is getting warmer. Temperature, sunshine and rainfall are often at the turning point of the year and tend to rise or increase. The growth of crops in early spring is accelerated, and the water consumption for bolting rape and jointing wheat is increased. Irrigation and topdressing should be done in time to promote growth. Agricultural proverbs remind people: "When it begins to rain in spring, get up early and go to bed late." Da Chun also began to prepare for farming. Although "spring" has been established, frost will still appear in most areas of the basin. In a few years, there will be a scene of "snow can't reach spring, so it flies through trees". These climatic characteristics should be taken into account when arranging agricultural production. Where is the information that people often look for in spring? The buds protruding from the wicker are "softer than gold and softer than silk"; The eager grass in the soil is waiting for "they grow taller in the spring breeze"; In order to win a new harvest, people who work hard in the fields are creating real spring with their hands.

Rain Water

The rainy season means that it begins to rain and the rainfall gradually increases. In the Yellow River valley, the birthplace of the 24 solar terms, it was cold before the rain, but it was snowing and raining unpleasantly. After the rain, the temperature can generally rise above 0℃, with less snow and more rain. However, in the warm climate of Sichuan Basin, even in the dead of winter, rainfall is not uncommon. During this period, the average climate temperature in our province is mostly above 10℃, peaches and plums are in bud, and cherries are in full bloom. It is indeed a climatic spring. Except for a few years, the frost period is over. It is timely to graft fruit trees and plant trees. After the dry winter, there are many droughts in spring all the year round, especially in the west of the basin. In agriculture, attention should be paid to moisture conservation and timely irrigation to meet the water supply at jointing and booting stage of wheat and at the critical stage of bolting and flowering of rape. The mountainous area of western Sichuan Plateau is still in the dry season, with low temperature and high wind speed, which is prone to forest fires. In addition, the invasion of cold wave will cause strong cooling and snowstorm, which will do great harm to the old, weak and young animals. These should pay special attention to prevention. Time flies and the seasons remind people. "A year's plan lies in spring". The management of Koharu and the preparations for Da Chun should be carried out quickly, so as to make this year better than previous years.

Too many words.

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