A specific dynasty or time determined by the 24 solar terms.

It is reported that as early as the Spring and Autumn Period and the Warring States Period, China can already measure the length of the midday sun shadow with a soil gauge (erect a pole on the plane) to determine the four solar terms of winter solstice, summer solstice, vernal equinox and autumn equinox. 1 year, the shortest day at noon is the summer solstice, the longest day is the winter solstice, and the shadow length is the vernal equinox or autumnal equinox. By the Qin and Han Dynasties, the complete concept of the 24 solar terms had been formed.

In ancient times, 1 year was divided into 12 months, and each month had two solar terms. The former is solar terms, while the latter is neutral. Later generations collectively referred to solar terms and neutral gas as solar terms.

It can be seen from the naming of 24 solar terms that the division of solar terms fully considers the changes of natural phenomena such as seasons, climate and phenology. Among them, beginning of spring, Changxia, beginning of autumn, beginning of winter, vernal equinox, autumnal equinox, summer solstice and winter solstice are used to reflect the seasons. The vernal equinox, autumnal equinox, summer solstice and winter solstice are divided from an astronomical point of view, reflecting the turning point of solar height change. Beginning of spring, Changchun, beginning of autumn and beginning of winter reflect the beginning of the four seasons.

Five solar terms, such as slight summer heat, great summer heat, intense summer heat, slight cold and severe cold, reflect the change of temperature. The four solar terms of rain, Grain Rain, light snow and heavy snow reflect the phenomenon of precipitation, indicating the time and intensity of rainfall and snowfall. The three solar terms, White Dew, Cold Dew and First Frost, on the surface reflect the phenomenon of condensation of water vapor, but in essence reflect the process and degree of gradual temperature drop: when the temperature drops to a certain extent, water vapor condenses. The continuous drop in temperature not only increases condensation, but also gets colder and colder. When the temperature drops below zero degrees Celsius, water vapor condenses into frost.

Xiaoman and awn seeds reflect the maturity and harvest of related crops; Frightening and Qingming reflect natural phenological phenomena, especially stinging, which indicates that spring will return with the recovery of early thunder in the sky and underground stinging insects.

I. Formation of the Twenty-four Solar Terms

In ancient times, people noticed that the position of the sun at noon in different seasons was different in elevation.

People erected a bamboo pole on the ground. According to the observation results throughout the year, it seems that the shadow of bamboo poles is shorter in summer and longer in winter. Obviously, with the change of seasons, the length of bamboo shadow caused by sunlight will also change.

Therefore, the shortest shadow day at noon is the summer solstice, also known as the north solstice or the long solstice, and the longest shadow day is the winter solstice, also known as the south solstice or the short solstice.

About the Yin and Shang Dynasties, people already knew how to determine the seasons by measuring shadows with poles. In addition, in the spring and autumn, it is found that one day is equal to day and night, so these two days are designated as the vernal equinox and the autumn equinox.

According to Zuo Zhuan, it was mentioned in the Spring and Autumn Period that time-sharing was observed. After the equal share, although it is beneficial to the arrangement of agricultural production, the climate changes greatly in a year, and the time between equal share and equal share is very long, which inevitably cannot meet the actual needs of farmers' production, so some solar terms have been formulated one after another.

Presumably, we must first add the beginning of the four seasons, namely, beginning of spring, Changxia, beginning of autumn and beginning of winter, which are collectively called four stands, and four stands and two halves are called "opening and closing", also known as eight sections.

With the development of agriculture, more and more solar terms are needed to guide farming. By the Qin Dynasty, the names of beginning of spring, Rain, Long Summer, Xiaoshu, beginning of autumn, Chushu, Bailu and Chushuang had been included in Lu Chunqiu.

In the Han Dynasty, due to the further development of agriculture, Liu An, the king of Huainan, in the astronomical training in Huainanzi, the 24 solar terms were complete, and the names were exactly the same as now, so it can be concluded that the 24 solar terms were complete in the Han Dynasty.

Second, the meaning and naming of solar terms

When the earth revolves around the sun, the axis of the earth runs obliquely, and the equatorial plane of the earth and the orbital plane are 23? Five degrees.

Therefore, in a certain area of the earth, the amount of sunlight received by the earth at different positions in the orbit of revolution varies due to direct or oblique light. When the sun shines directly, the area receives more light and heat, and the climate will be hot. When the sun is tilted, the area receives less light and heat, and the climate will be cold.

The twenty-four solar terms are simply the twenty-four points on the earth's orbit around the sun, just like the mileage sign on the orbit. When the solar term arrives, what kind of climate will there be, which reflects the climate change in different periods of the year.

Since most of the fields in Qin and Han Dynasties were located near the Central Plains, that is, in the Yellow River valley, the names of the 24 solar terms were named according to the climate change and the farming time of planting and sowing in the region, except for the four vertical and eight sections indicating the seasonal changes and the division of the four seasons, which were closely combined with agricultural production.

The names of the 24 solar terms are beginning of spring, Rain, Sting, Vernal Equinox, Qingming, Grain Rain, Changxia, Xiaoman, Mangzhong, Summer Solstice, Xiaoshu, beginning of autumn, Chushu, Bailu, Autumn Equinox, Cold Dew, Chufrost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold.

In order to remember the names and order of the 24 solar terms, people take out one or two words from each solar term name to form a song formula.

There is also because the dates of the 24 solar terms in the solar calendar have not changed much. Some people have compiled the dates of the 24 solar terms as "every Saturday and 21st in the first half of the year, and every August and 23rd in the second half of the year, with only one or two days before and after. For example, in 1988, beginning of spring is on February 4th, summer solstice is on June 22nd, beginning of autumn is on August 8th, and winter solstice is on1February 22nd. If you remember the above songs and formulas, you can know the names of solar terms and the approximate dates in the solar calendar.

Twenty-four solar terms can be divided into four categories according to their meanings.

Changes in cold and summer are: beginning of spring, vernal equinox; Long summer, summer solstice; Beginning of autumn, autumnal equinox; Beginning of winter, the solstice of winter.

Signs of temperature change are: slight summer heat, severe summer heat, intense summer heat, slight cold and severe cold.

Rainfall is reflected in rain, Grain Rain, white dew, cold dew, first frost, light snow and heavy snow.

Farming activities include: Jingzhe, Qingming, Xiaoman and Mangzhong.

Due to the uneven movement speed of the earth, the faster revolution speed around perihelion and the slower movement speed of apohelion, the dates are often one or two days apart.

Calculation of solar terms

The ancient method of calculating the time of 24 solar terms is to divide the time from the winter solstice of the current year to the winter solstice of the following year into 12 equal parts, each equal part is called zhongqi, and then divide the length of two zhongqi into equal parts, the number of points is called solar terms, and twelve zhongqi plus twelve solar terms are commonly known as 24 solar terms.

The solar terms obtained by dividing a year into twenty-four equal parts are called flat solar terms, but because the earth's orbit around the sun is elliptical, the speed of the earth's orbit is not constant, and the date of the flat solar terms obtained by dividing the tropical year into twenty-four equal parts cannot reflect the real position of the earth on the orbit.

Therefore, from the constitutional calendar of the early Qing Dynasty (A.D. 1645), the calculation of solar terms time was changed from flat solar terms to fixed solar terms. The so-called solar terms are set from the vernal equinox. The orbit of the earth around the sun is to set a solar term every 15 degrees, and there are 24 solar terms in a 360-degree week. The solar terms calculated by this method can better represent the position of the earth in the orbit of revolution and reflect the climate at that time.

The significance of individual representatives of four or twenty-four solar terms

Each of the 24 solar terms reflects the seasonal change, climate change, phenological characteristics and crop growth, so it has its own unique meaning, as follows:

Beginning of spring: Spring begins. beginning of spring means the beginning. Spring is stupid, which means that everything begins to come alive.

Rain: When spring comes to the world, the rain begins to increase and the spring rain keeps coming.

Sting: Insects hibernate or hide, which is called sting. Spring thunder will awaken the dormant and hibernating insects underground, and the excavation activity will begin.

Equinox: In the middle of spring, the sun shines directly on the equator. On this day, the sun rises in the east and sets in the west. The northern hemisphere and the southern hemisphere of the earth receive equal light, and the length of day and night is equal. In ancient times, it was called vernal equinox, and autumn was divided into day and night.

Qingming: The weather is getting warmer and warmer, spring is blooming, vegetation is beginning to sprout and flourish, and the earth is clear and beautiful.

Grain Rain: Rain gives birth to a hundred grains. At this time, farmers have just finished spring ploughing, and the seedlings in the field need a lot of rain. Timely and sufficient rain can make the grain grow sturdily. But the climate at this time is sunny, rainy and hot, which is the most unpredictable.

Long summer: Since early summer, the climate has been warm and everything has grown rapidly.

Xiaoman: Full refers to the full grain, and summer crops such as rice and wheat are about to bear fruit, waiting for maturity, but not yet full.

Ear seed: crops with awns begin to mature and bear ears. At this time, it is also a suitable season to sow crops in autumn.

Summer solstice: the hot summer is coming innocently. At this time, the sun shines directly on the Tropic of Cancer, and the northern hemisphere receives the most light, with the longest day and the shortest night. At noon, the elevation of the sun is the highest in a year, so the sun shadow is the shortest in a year. After the summer solstice, the days get shorter and the nights get longer.

Slight summer heat: summer heat is hot. At this time, the weather is getting hotter, but it is not hot enough. Although the northern hemisphere is exposed to the sun for the longest time from summer to Sunday, the heat from the sun must first warm the ground and the atmosphere before it can be stored in the atmosphere, so the weather starts to heat up slowly from summer to Sunday, and the heat will gradually rise to the extreme from summer to the future.

Summer heat: the climate is extremely hot, reaching its peak.

Beginning of autumn: From beginning of autumn, the temperature will change from hot to cold, and cool and comfortable autumn is coming.

Summer heat: It means that the summer heat is over, but sometimes a sunny afternoon is as hot as the summer heat, which can be regarded as the return of summer.

The Millennium: It's getting cold. At night, the water vapor contained in the air comes into contact with the objects cooled rapidly by radiation on the ground, so some of them condense into water droplets and attach to the flowers and leaves on the ground. These transparent and sparkling water drops are called white dew.

Autumnal Equinox: Autumn is halfway through, just like the vernal equinox. At this time, the sun shines directly on the equator, and the northern hemisphere and the southern hemisphere on the earth receive equal light and the length of day and night is equal.

Cold dew: It's already late autumn, and the weather is getting colder. The fog and dew you come into contact with in the morning and evening feel chilly, and the vegetation will wither.

First frost: It's getting cold. When the temperature of an object on the ground drops to zero degrees Celsius or below, the contacted water vapor directly frosts and adheres to it.

Beginning of winter: Winter begins and ends, crops have been harvested and stored, and farming has been completed.

Xiaoxue: The climate is cold. At this time, when the temperature in the air is below zero degrees Celsius, the water vapor in the air will condense into crystalline solids and fall from the air. This is called snowfall, but the amount of snowfall is not much or great.

Heavy snow: it's colder, heavy snow, and there is snow on the ground.

Winter solstice: when winter comes, the sun shines directly on the tropic of Capricorn, and the northern hemisphere receives the least light, the shortest day and the longest night. At noon, the sun has the lowest elevation angle and the longest shadow in a year.

Xiao Han: It's quite cold. Although it has entered the severe winter, it has not yet reached the coldest time.

Great cold: The weather is extremely cold, which is the coldest day of the year.

When the 24 solar terms were formulated in Qin and Han dynasties, it reflected the climate change in the Yellow River basin and the relationship between climate and crops. However, after the management of various dynasties, China is now a vast country with a distance of about 3,000 kilometers from north to south. Not only is the climate different in different places, but also the crop species, ecology and farming time are different in different places, so the literal meaning of the 24 solar terms is not applicable everywhere.

However, because the climate change in every place is almost fixed throughout the year, farmers everywhere know what kind of climate will appear in that place according to the accumulation of long-term experience, so they use the name of solar terms, but not limited to the literal meaning, and summarize the changes that will occur when different solar terms arrive, so as to adjust their daily lives and carry out farming in time, so the 24 solar terms are still often used by ordinary farmers.

Respondents: Master of the World-Scholar II11614:11.

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The twenty-four solar terms originated from the twenty-four solar terms attached to taichu calendar and were created in the first year of Emperor Wu of Han Dynasty (before 104). Twenty-four solar terms are completely stipulated in taichu calendar, and each solar term lasts about fifteen days. In fact, it is a 24-solar calendar. It has real practical value in our traditional calendar, which is conducive to guiding agricultural production and is welcomed by farmers.