How many of the 24 solar terms in a year do you know?

Solar terms are precious scientific heritage created by Chinese ancestors after thousands of years of practice. They are tools to reflect changes in weather, climate and phenology, and to control farming seasons.

As early as the Spring and Autumn Period and the Warring States Period, China had been able to use Tugui (a pole erected on a flat surface) to measure the length of the shadow of the sun at noon to determine the four solar terms of winter solstice, summer solstice, vernal equinox, and autumnal equinox.

In a year, the day with the shortest shadow of Tugui at noon is the summer solstice, the longest day is the winter solstice, and the day with moderate shadow length is the vernal or autumnal equinox.

The solar terms are described in the book "Shangshu" from the Spring and Autumn Period.

There is a complete record of the twenty-four solar terms in the book "Huainanzi" written by Liu An of the Western Han Dynasty.

In ancient my country, the lunar calendar (lunar calendar) was used to record time, and the solar calendar (solar calendar) was used to divide the twenty-four solar terms of spring, summer, autumn and winter.

Our ancestors called 5 days one period, and 3 periods were called solar terms. The whole year was divided into 72 periods and 24 solar terms.

With continuous observation, analysis and summary, the division of solar terms gradually became richer and more scientific. By the Qin and Han Dynasties, more than 2,000 years ago, a complete concept of the twenty-four solar terms had been formed.

In ancient times, a year was divided into twelve months, and each month had two solar terms.

The first one is the solar term, and the last one is the middle Qi. For example, the beginning of spring is the first lunar month, and the rain is the middle of the first lunar month. Later generations collectively referred to the solar terms and the middle Qi as solar terms.

The names of the twenty-four solar terms are: Beginning of Spring, Rain, Waking of Insects, Vernal Equinox, Qingming, Grain Rain, Beginning of Summer, Xiaoman, Ear Grain, Summer Solstice, Minor Heat, Great Heat, Beginning of Autumn, End of Heat, White Dew, Autumnal Equinox, Cold Dew, Frost Descent, Beginning of Winter, Light Snow, Heavy Snow,

Winter Solstice, Minor Cold, and Major Cold.

The twenty-four solar terms are divided according to the position of the sun on the ecliptic (that is, the earth's orbit around the sun).

As the sun starts from the vernal equinox (zero degrees of ecliptic longitude, when the sun shines vertically on the equator), every 15 degrees it advances is a solar term; it travels for one week and returns to the vernal equinox, which is a tropical year, totaling 360 degrees, so it is divided into 24 solar terms.

The dates of solar terms are relatively fixed in the solar calendar. For example, the beginning of spring is always between February 3rd and 5th in the solar calendar.

However, in the lunar calendar, the dates of solar terms are not easy to determine. Taking the beginning of spring as an example, it can be on December 15 of the previous year at the earliest and on the 15th of the first lunar month at the latest.

It can be seen from the naming of the twenty-four solar terms that the division of solar terms fully takes into account changes in natural phenomena such as seasons, climate, and phenology.

Among them, the beginning of spring, the beginning of summer, the beginning of autumn, the beginning of winter, the vernal equinox, the autumnal equinox, the summer solstice, and the winter solstice are used to reflect the seasons, and the year is divided into four seasons: spring, summer, autumn, and winter.

The vernal equinox, autumnal equinox, summer solstice, and winter solstice are divided from an astronomical perspective and reflect the turning points of the sun's altitude changes.

The beginning of spring, the beginning of summer, the beginning of autumn, and the beginning of winter reflect the beginning of the four seasons.

Because China has a vast territory and a very obvious monsoon and continental climate, the weather and climate vary greatly from place to place, so the four seasons changes in different areas also vary greatly.

The five solar terms of minor heat, major heat, severe heat, minor cold, and major cold reflect the changes in temperature and are used to indicate the degree of cold and heat at different times of the year; the four solar terms of rain, grain rain, light snow, and heavy snow reflect precipitation phenomena and indicate the time of rainfall and snowfall.

and intensity; the three solar terms of white dew, cold dew, and frost fall superficially reflect the phenomenon of water vapor condensation and sublimation, but in essence reflect the process and degree of gradual decline in temperature: when the temperature drops to a certain level, water vapor condenses; temperature

As the temperature continues to decline, not only does the condensation increase, but it also becomes cooler and cooler; when the temperature drops below zero degrees Celsius, the water vapor condenses into frost.

Xiaoman and Mangzhong reflect the maturity and harvest of relevant crops; Jingzhe and Qingming reflect natural phenological phenomena, especially Jingzhe, which uses the first thunder in the sky and the resurgence of underground stinging insects to herald the return of spring.

The comparison list of the twenty-four solar terms and the solar calendar dates is as follows: Solar term month date Solar term month date Solar term month date Xiaohan January 5 or 6 Beginning of summer May 6 or 7 Bailu September 8 or 9 Dahan 20 or 21

Xiaoman 21st or 22nd Autumn Equinox 23rd or 24th Beginning of Spring February 4th or 5th Ear Grain June 6th or 7th Cold Dew October 8th or 9th Rain 19th or 20th Summer Solstice 21st or 22nd Frost 23

July 7 or 8, Beginning of Winter, November 7 or 8, Spring Equinox on November 7 or 8, Great Heat on 21 or 22, Great Heat on 23 or 24, Light Snow on 22 or 23, Tomb Sweeping Day, April 5

August 8 or 9, heavy snowfall, December 7 or 8, Grain Rain, 20 or 21, end of heat, 23 or 24, winter solstice, 23 or 24, introduction to the twenty-four solar terms (1) Beginning of Spring since the Qin Dynasty

Since ancient times, our country has always regarded the beginning of spring as the beginning of spring.

The beginning of spring is astronomically divided, but in nature and in people's minds, spring means warmth, birds singing and flowers fragrant; spring means growth, cultivation and sowing.