How did the twenty-four solar terms that have been circulating for a long time come from?

Lu You, a poet in the Southern Song Dynasty, said in his poem "Time Rain": "When it rains, awns are planted all over the world. Every family is beautiful in wheat and rice, and the songs are long everywhere. " The poem describes the situation of farmers planting awn seeds, from which we can see the importance of the twenty-four solar terms.

In fact, solar terms were born as early as 2000 years ago, and only the exploration and improvement of working people have made it what it is today.

Farming gives birth to solar terms

The formation of the 24 solar terms is a gradual process. Yang Quan, a philosopher in the Western Jin Dynasty, recorded in "On Things": "In the past, Shennong began to treat farming, regulate solar terms, and judge cold and heat, thinking that it was a period of morning and evening, so it was a calendar day." These words show that the original intention of setting up solar terms is to "manage farming." The solar term is a year, and about 15 days is a solar term, which is divided into 24 different solar terms.

During the Spring and Autumn Period, Shangshu, one of the Five Classics, had an allusion to Emperor Yao's command to "measure moderately", and established solar terms such as summer solstice, winter solstice, vernal equinox and autumn equinox. In Guanzi Zhongqing Collection, solar terms such as spring, summer, autumn and winter have been added. In the Warring States Period, the solar terms in Lv's Spring and Autumn Annals increased to 22, and the solar terms took shape. At the beginning of the Han Dynasty, two solar terms, Xiaoman and Heavy Snow, were added to Huainanzi Astronomical Training, forming a complete solar term system.

There are eight sections in Zhou Pian Shu Jing, a work of the Western Han Dynasty. This paper introduces the 24 solar terms in detail, discusses the phenological changes caused by the changes of the four seasons, summarizes the reasonable order of sensory cognition, and guides farmers to produce in time through the combination of the 24 solar terms and agricultural production. The release of the twenty-four solar terms is a beneficial attempt to conquer nature in ancient agricultural society.

From the perspective of various solar terms, we can also spy on its interpretation of natural changes and agricultural production. Four stands represent the arrival of four seasons, the vernal equinox and autumnal equinox represent equal division of day and night, and the summer solstice and winter solstice represent the arrival of hot and cold peaks. Grain Rain means plenty of rain, which is good for grain growth. Small fullness means that the grain of summer grain begins to be full. Mango in Lu You's poems symbolizes the busyness of summer sowing and summer harvest. Twenty-four solar terms are formed in agricultural activities and fed back to agricultural activities. The two complement each other and live in harmony.

Astronomical restrictive solar terms

In addition to internal factors, the 24 solar terms are also manipulated by external factors. As we all know, the earth's rotation produces day and night, and it takes 365 days 5: 48: 46 to make a revolution around the sun. Because there is always an included angle of 66 34' between the earth's rotation axis and its revolution orbit, the difference between direct sunlight and oblique sunlight is caused. For this reason, astronomers in the Western Zhou Dynasty measured the time of summer solstice and winter solstice with the method of standard table mapping.

In ancient times, astronomers called the annual orbit of the sun "the ecliptic". The whole ecliptic is divided into 360 degrees, and every 15 degree is listed as a solar term, and the ecliptic is divided into 24 equal parts. For example, influenced by the included angle, the sun will move north and south in a year. When it appears at 90 degrees and 270 degrees of the ecliptic, it is summer solstice and winter solstice respectively, reaching the extreme value of the day and night duration in the northern and southern hemispheres of the earth. When the sun is located at 0 and180 of the ecliptic, it points directly to the equator, and day and night are equal, that is, the vernal equinox and the autumnal equinox. The sun reaches the ecliptic 120 and 255, which are the great summer heat and the great cold respectively.

In fact, sunlight determines the growth rhythm of living things, which is phenology. Solar terms not only indicate the duration of light, but also reveal the intensity of light. The thickness of the earth's atmosphere is about 1300 km. The radiation of the sun will be absorbed by water vapor, dust, carbon dioxide and other substances in the air, resulting in heat attenuation, so the intensity of sunlight is related to the thickness of the atmosphere. During the summer solstice, the sun shines directly in the northern hemisphere, and the light intensity is relatively high. During the winter solstice, the sun shines obliquely in the northern hemisphere and is absorbed by the atmosphere, and the light intensity is relatively low.

Sunlight acts on the earth and is influenced by land and sea, so the distribution of heat energy is uneven. The sea is colder than the land in summer, and the land is colder than the sea in winter. Air usually flows from cold to hot, which is one of the main reasons for the alternation of cold and warm. In this way, there are four seasons in a year, and the solar terms come into being. The complex reaction caused by the sun radiating the earth makes the birth of solar terms more meaningful.

Calendar realizes solar terms

A complete solar term needs an accurate calendar to practice. The solar term Song said: "Spring rains shake the valley days in spring, summer is full and summer is hot, autumn is cold and frost is falling, and winter snow is raining." The two festivals have not changed every month, with a difference of one or two days at most. There were 621 in the first half of the year and 823 in the second half. " It is strange that the second half of the Song formula uses the modern solar calendar instead of the traditional lunar calendar.

The reason is that the 24 solar terms are distributed in a year, and there are two solar terms every month. The former is called "solar terms" and the latter is called "neutral gas". In the solar calendar1-July, there are 365,438+0 days in a single month, 30 days in a double month, and the opposite is true after July, but there are 28 or 29 days in February, which is consistent with the revolution time of the earth around the sun. Therefore, the 24 solar terms are relatively fixed in the solar calendar.

The average lunar month is only 29.5 days, and the "solar terms" and "neutral atmosphere" in one month will be delayed by one or two days compared with the previous month. By analogy, if it is postponed month by month, it will be postponed for one year 1 1 day. Therefore, the lunar calendar uses the leap method to make up for the missing days. Compared with the solar calendar, the solar terms in the lunar calendar are calculated. With the help of the calendar, solar terms are more scientific and convincing.

Folk custom sets off solar terms

The solar term is quite grounded among the people, which accelerates its popularization. In rural areas, there are many agricultural proverbs related to solar terms, such as: "After the Scare Festival, spring ploughing will not stop", "Before and after Tomb-Sweeping Day, point melons and plant beans", "Tomb-Sweeping Day will be sunny, Grain Rain will be drenched", "When the summer is full, the rain will catch up", "After the canopy, you can't plant strong crops", "Little summer surprises the east wind, and big summer surprises the hongxia" and so on. These agricultural proverbs are closely related to solar terms, which embodies the guiding value of solar terms in agriculture.

With the rise of modern meteorology, meteorological departments have integrated meteorological observation data, various forecast information and 24 solar terms, compiled agricultural meteorological calendars or agricultural activity tables, and combined the experience of ancient solar terms with modern scientific and technological means to complement each other and learn from each other, thus continuing to play a role in modern agricultural production.

In addition to agriculture, solar terms have also evolved into popular folk customs. It is clearly recorded in The Book of Rites and the Monthly Order that in the Zhou Dynasty, beginning of spring wanted to "dig cows and send air conditioners". The folk "spring cow" is derived from this. This custom has been followed throughout the ages, especially in the Tang and Song Dynasties. Men "whip spring" and pray for good weather, while women "Dai Chun" wish a happy life. This custom shows a strong tension in life.

The Qingming Festival every year is a day for people to visit their ancestors. Du Mu, a poet in the Tang Dynasty, said, "It rains a lot during the Qingming Festival, and pedestrians on the road want to break their souls. Excuse me, where is the restaurant? " The poem "The Shepherd Fingers the Xinghua Village" shows the special atmosphere of Tomb-Sweeping Day. From Shang and Zhou Dynasties to the early Han Dynasty, the winter solstice was the beginning of the year. In Taiwan Province Province and the southeast coastal areas, the winter solstice is the day to worship ancestors, but the saying that "the winter solstice is as big as a year" is still circulating in Chinese mainland. The proverb "winter solstice wonton, summer solstice noodles" is widely known and deeply rooted in people's hearts. The combination of solar terms and life has injected great vitality into it.

China's original solar terms show the wisdom of working people and the development level of ancient astronomy, combine time, climate and phenology, and condense the knowledge system of natural rhythm change, which is known as "the fifth invention of China" in the international meteorological community. 2065438+0165438 On October 30th, 2006/KLOC-0, the 24 solar terms lasting for thousands of years were listed in the Representative List of Intangible Cultural Heritage of Humanity. No matter now or in the future, the 24 solar terms still play an indispensable role in society.