The twenty-four solar terms are introduced in detail, how to divide the non-solar terms in Song Dynasty and its origin.
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 autumnal 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 phenology, especially stinging, which indicates that spring will return with the recovery of early thunder in the sky and underground stinging insects.
The twenty-four solar terms divide the change of the position of the sun on the ecliptic and the evolution order of the ground climate caused by it into twenty-four segments, each of which is separated by about half a month and less than twelve months respectively. The beginning of the month is called "solar term" and the middle of the month is called "neutral gas". The so-called "qi" refers to meteorology and climate.
The names and order of these 24 solar terms are: beginning of spring, Rain, Creeping, Vernal Equinox, Qingming, Grain Rain, Long Summer, Xiaoman, Mango, Summer Solstice, Small Agency, Big Agency, beginning of autumn, Early Agency, Bailu, Autumn Equinox, Cold Dew, First Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold. Among them, beginning of spring, vernal equinox, long summer, summer solstice, beginning of autumn, autumnal equinox, beginning of winter and winter solstice are used to divide the four seasons of a year; "Dichotomy" and "two pairs" are the turning points of the season, and "four stops" indicate the beginning of the season.
Small, large, small, slight cold and severe cold represent the hottest and coldest periods of the year.
White dew, cold dew and first frost reflect the process and degree of cooling; Rain, Grain Rain, light snow and heavy snow reflect the degree of rainfall and snowfall; Stunning, clear, small full and awn grass reflect the season and the growth of crops.