Introduction of Solar Terms and Pentads in Spring:the Rain Water,the Spring Equinox,the Grain Rain.

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24 Solar Terms and The Seventy-Two Pentads.

 Spring Introduction:The Seventy-Two Pentads system is one of China's earliest calendar, it is also a combination of astronomy, meteorology, phenology of knowledge, and used as the calendar of agricultural activities. It originated from the Yellow River basin, its complete version literature record was found in an ancient book of the 2nd century BC, its name is known as the Yi Zhou Shu(the Lost Book of the Zhou Dynasty).The Seventy-Two Pentads is an important pentad calendar of ancient China, the system defined 5 days as one Pentads, 3 Pentads as 1 solar term or 1 lunar term, 3 solar term as 1 Season, 4 Season as 1 Year, total 12 solar terms plus 12 middle solar terms, total 24 solar terms, added up total 72 pentads. Each Pentad is corresponding to one phenomenon of natural things, which known as Hou Yin(or the natural phenomena pair of the Pentad), to represent the general change conditions of the natural things and climate. The Hou Yin(or the natural phenomena pair of the Pentad) could be classified into 3 types, one type defined according to natural creatures, such as activities of birds,insects,earthworms,etc, a second type defined according to plants, such as peach blooming,duckweed grow out,grain crops mature, etc, a third type defined according to climate changes, such as water frozen, storm and thunder heard, soil turn moisture,etc.The change in the 72 pentads in orders reflects the general situation of climate change in the year.
 the Earth and the Celestial Equator The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space.As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane.Directly above the Earth’s equator lies the celestial equator, a circle which goes all the way around the sky and which divides the northern half of the celestial sphere from the southern half.In the precession of the equinoxes, motion of the equinoxes along the ecliptic (the plane of Earth’s orbit) caused by the cyclic precession of Earth’s axis of rotation.The Celestial Sphere "rotates" on the Celestial Axis, which goes through earth’s north and south poles and extends out to the Celestial Sphere intersecting it at the North Celestial Pole (NCP) and the south Celestial Pole (SCP).The Celestial Equator is an imaginary line around the middle of the Celestial Sphere, equidistant from the NCP and SCP and on the same plane as the earth's equator. It intersects the Circle of the Horizon at East and due West.


 Li Chun,the Beginning of Spring Li Chun,the Beginning of Spring 1.The solar term "Li Chun", or the Beginning of Spring, is the 1st solar term in the lunar calendar twenty-four solar terms. The Beginning of Spring is defined by the astronomical knowledge, that is, when the sun reaches the celestial longitude 315 degrees. Its date is February 3rd or 4th of each year. The Beginning of Spring is one of the important traditional Chinese festivals. "Li" means "the beginning", since the Qin Dynasty, China had formed an official tradition and set the solar term "the Beginning of Spring" as the start of the spring season. The so-called "The plan of one year start since the Spring", the climate warming up, flowers starts blooming, birds begin twittering, farmers started cultivating and planting crops.

 Yu Shui,the Rain Water Yu Shui,the Rain Water 2.The solar term "Yu Shui", or the Rain Water, is the 2nd solar term of the 24 solar terms, its date is around the 15th of the first lunar month(Gregorian calendar February 18-19th), the sun reaches the celestial longitude 330 degrees. At this date, the temperature keeps elevating, snow and ice start melting, precipitation and rains increased, so it named the Rain Water. The solar term "Yu Shui, or the Rain Water" starts from February 18th or 19th, lasting till March 4th or 5th. Indicated by its name, the Rain Water, is a solar term which name reflects the precipitation.

 Jing Zhe,the Awakening from Hibernation Jing Zhe,the Awakening from Hibernation 3.The solar term "Jing Zhe", or the Awakening from Hibernation, is the 3rd solar term of the 24 solar terms, its date is around the 5th or the 6th of March, the sun reaches the celestial longitude 345 degrees. Before the solar term Jing Zhe or the Awakening from Hibernation, small animals still hidden in soil and in Hibernation, do not eat and not drink, so it was named "蛰(Hibernation)", once the spring thunder wakes up those small animals, it was named "惊(shocking)". At the date of the "Jing Zhe" or the Awakening from Hibernation, small animals wake up, the temperature turns warm, spring thunder comes, most areas of China and the Northern Hemisphere enter into the plowing seasons.

 Chun Fen,the Spring Equinox Chun Fen,the Spring Equinox 4.The Chun Fen, or the Spring Equinox(also known as the Vernal equinox), is the midpoint of the 90 spring days. It is the 4th solar terms of the 24 solar terms, its date is around the 20th or 21nd of March, the sun reaches the celestial longitude 0°(the Vernal equinox).

 the Spring Equinox:Position of the Sun and the celestial equator  At the date of the Vernal equinox, the sun shining directly on the Earth equator, the north and south hemisphere season is opposite, in the northern hemisphere it is the Spring equinox(or the vernal equinox), in the southern hemisphere it is the Autumnal equinox. The day of the Spring equinox is also the new year festival of some countries(Iran, Turkey, Afghanistan, Uzbekistan and other countries). In the period terms, the Spring equinox(or the Vernal equinox) also refers to the period in which the sun moves between the celestial longitude 0 ° and 15 °, that is, from the Vernal equinox day to the next solar term the QingMing(the Pure Brightness), in the Gregorian calendar it is from the March 20th to April 5th.

 the Spring Equinox:Length of Daylight and Angle of the Sun On the day of the Spring Equinox, the sun is almost shining direct to the Earth's equator, and all the areas of the planet Earth almost share the same day time and night time. After the Spring Equinox(the vernal equinox), the Subsolar point moves from the equator to the northern hemisphere, day time longer and night time shorter(the day is longer than the night) at the northern hemisphere, daytime turns shorter and nighttime turns longer(the day shorter than the night) at the southern hemisphere.

 QingMing,the Pure Brightness QingMing,the Pure Brightness 5.The QingMing, or the Pure Brightness, also named "Tomb-Sweeping Day", it is the 5th solar term of the 24 solar terms, its date is around the 4th to 6th of April, the sun reaches the celestial longitude 15°.The QingMing festival, is also a traditional vacation of China, one of the most important Sacrifice Festival, during the QingMing festival, folks sacrifice to ancestors and sweeping tombs. As a tradition of Chinese, the Qingming festival starts from the Zhou Dynasty and already has over 2500 years history, it was announced as a national public vacation since the year 1935, also bears a name National Tomb-Sweeping Festival. Once the QingMing festival approach, the Qi turns clear and Scenes become bright, all things in nature show themselves, thus the solar term also known as "the Pure Brightness", in the days of the Pure Brightness, the temperature keeps elevating, spring cultivation season comes.

 Gu Yu,the Grain Rain Gu Yu,the Grain Rain 6.The GuYu, or the Grain Rain, is the 6th solar term of the 24 solar terms, its date is around 19th to 21st of April, the sun reaches the celestial longitude 30°. Ancient folks told "Rains give birth of grains", thus it got the name the Grain Rain, the Grain Rain is the best period for sowing seeds and planting trees, sowing beans.In the days of the Grain Rains, the temperature keeps elevating quickly, rains frequently at the North Hemisphere.

  • 1.Introduction of Solar Terms and Pentads in Spring:the Rain Water,the Spring Equinox,the Grain Rain.
  • 2.Shang Han Za Bing Lun:the Treatise on Cold-induced and Miscellaneous Diseases.By Zhāng Zhòngjǐng.
  • 3.Yi Zhou Shu(the Lost Book of the Zhou Dynasty).

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