Chinese Astronomy
Chinese Astronomy
How did ancient Chinese determine seasons? Ancient Chinese determined seasons and the passage of time through the astronomical phenomena at early evening, mansions (also known as lunar lodges, lunar mansions, constellations, xiu) in the southern sky and the Big Dipper (the Plough).The following is taken from chapter THE CANON OF YAO of SHU JING [SHU CHING].
.... Yao separately commanded Xizhong to reside at Yanggu .... The day is of the medium length and the star (mansion, constellation) is Niao. You may thus exactly determine mid-spring ....
.... He further commanded Xishu to reside at Nanjiao .... The day is at its longest, and the star is in Huo. You may thus exactly determine mid-summer....
.... He separately commanded Hezhong to reside at Meigu, .... The night is of the medium length, and the star is Xu. You may thus exactly determine mid-autumn....
.... He further commanded Heshu to reside at Youdu, .... The day is at its shortest, and the star is Mao. You may thus exactly determine mid-winter....
(mid-winter, winter solstice, mansion Mao)
(mid-spring, spring equinox, mansion Niao)
(mid-summer, summer solstice, mansion Huo)
(mid-autumn, autumnal equinox, mansion Xu)The above pictures show the simulated phenomena in the southern sky at early evening around 1700 BC.
Ancient Chinese also determined seasons and the passage of time through the pointing direction of the handle of the Big Dipper (the Plough). In the winter the "handle" points north at early evening, in the spring the "handle" points east at early evening, and so on. The following animated picture shows the astronomical phenomena in northern sky at early evening of 24 Jieqi around 450 BC. For the detail of twenty-four Jieqi, please refer to the page Chinese Calendar.
The above pictures were produced with Home Planet .
12 Houses of the Yellow Path
(the path along which the sun seems to move, or ecliptic)
It was great convenience to use lunar months for civil purposes in ancient times because moon phases were obvious. Each year has approximately twelve lunar months, which is the real reason why the Yellow Path
Ancient Chinese determined seasons through the pointing direction of the handle of the Big Dipper (the Plough). In the winter the "handle" points downward, north, at early evening. In the spring the "handle" points east at early evening, and so on. Accordingly, ancient Chinese divided the horizon into twelve sections and gave them names for linking the directions to which the "handle" of Big Dipper points in twelve months. Twelve names of these sections are Zi (north), Chou, Yin, Mao (east), Chen, Si, Wu (south), Wei, Shen, You (west), Xu and Hai, and are known as twelve Terrestrial/Earthly Branches. Each branch has its meaning, e.g.. Zi means to nurture. Finally, the twelve Terrestrial/Earthly Branches were applied to the 12 houses of the Yellow Path and arranged in clockwise direction.
Why was the direction of Chinese zodiac in reverse to western zodiac? It is because what ancient Chinese drew were what they saw.
Ancient Chinese determined the passage of time through the astronomical phenomena, mansions, in the southern sky at early evening. Stars move from east to west every night. The order of mansions, zodiacal constellations, on the Chinese zodiac just only describes the order of appearances of mansions according to actual phenomena in southern sky.
Ancient Chinese astronomers divided the sky into three Enclosures, twenty-eight Mansions and four Images/Symbols/Quadrantal Xiu. Seven Mansions form one Image. The Four Images are the Azure Dragon, the Vermilion Bird, the White Tiger and the Murky Tortoise.
The three Enclosures are Purple Forbidden Enclosure, Supreme Palace Enclosure and Heavenly Market Enclosure. The following is angular measurements of 28 mansions recorded in one manuscript from caves of Dunhuang.
Mansion (Xiu) Angular Distance apart on Red Path
(Equator, ancient Chinese unit, degree)Angular Distance from Pole
(ancient Chinese unit, degree)Horn 12 91.5 Neck 9 89 Root 15 94 Room 5 108 Heart 5 108.5 Tail 18 120 Winnowing-basket 11 118 Dipper 26.25 116 Ox 8 106 Girl 12 106 Emptiness 10 104 Rooftop 17 90 Encampment 16 85 Wall 9 86 Legs 16 70 Bond 12 80 Stomach 14 72 Hairy head 11 74 Net 16 78 Turtle beak 2 84 Three stars 9 94 Well 33 70 Ghosts 4 68 Willow 15 77 Star 7 97 Extended net 18 97 Wings 18 99 Chariot 17 98 According to historical books, at least one Armillary Sphere at the Ancient Observatory is graduated in ancient Chinese unit of angles (degree, Du,
), 365.25 degrees to the circumference, to match the year length. It was convenience to set a circumference of 365.25 degrees for astronomical calculation and prediction, because ancient astronomers used to believe that the sun moved among the stars (mansions) and returned to the same star (mansion) after 365.25 days, and the sun moved along the equator at constant speed.
Water clock, clepsydra with 100 markings (also known as Ke/Tu/ Du/degrees), were the earliest timekeeper for measuring the passage of time, the lengths of day and night, midnight especially. This device divided a day into 100 parts.
It seems probable that before Han dynasty ancient Chinese only determined the coordinates of the sun on the year's shortest day and longest day. Ancient Chinese determined the equatorial coordinate of the sun through the observation of the star (mansion) in the southern sky at the midnight when the gnomon showed the year's longest day. At the midnight the sun was right on the opposite side to the star (mansion) which crossed the meridian.
12 Ci means twelve sections on the celestial equator. The Sun, Moon and the planets apparently move through them in seasonal order. These sections are Xingji, Xuanxiao, Zouzi, Jianglou, Daliang, Shichen, Chunshou, Chunhuo, Chunwei, Shouxing, Dahuo and Ximu. The following table was compiled according to the chapter CI DU ( The Order and The Measurements) of HAN SHU (History of the Han Dynasty). For the detail of Jie and Zhong mentioned in the following table, please refer to the page Chinese Calendar.
Begins with (Mansion, degree, Jie) Middle (Mansion, degree, Zhong) Xing Ji Dipper, 12, Great Snow Ox, 0, Winter Solstice Xuan Xiao Girl, 8, Slight Cold Rooftop, 0, Great Cold Zou Zi Rooftop, 16, Beginning of Spring Encampment, 14, Waking of Insects Jiang Lou Legs, 5, Rain Water Bond, 4, Spring Equinox Da Liang Stomach, 7, Grain Rain Hairy head, 8, Pure Brightness Shi Chen Net, 12, Beginning of Summer Well, 0, Grain Full Chun Shou Well, 16, Grain in Ear Well, 31, Summer Solstice Chun Huo Willow, 9, Slight Heat Extended net, 3, Great Heat Chun Wei Extended net, 18, Beginning of Autumn Wings, 15, Limit Heat Shou Xing Chariot, 12, White Dew Horn, 10, Autumnal Equinox Da Huo Root, 5, Cold Dew Room, 5, Descent of Frost Xi Mu Tail, 10, Beginning of Winter Winnowing-basket, 7, Slight Snow The above table actually means that
At the Sun enters the Sun reaches Great Snow Xing Ji 12 degrees Dipper Winter Solstice 0 degree Ox Slight Cold Xuan Xiao 8 degrees Girl Great Cold 0 degree Rooftop Beginning of Spring Zou Zi 16 degrees Rooftop Waking of Insects 14 degrees Encampment Rain Water Jiang Lou 5 degrees Legs Spring Equinox 4 degrees Bond Grain Rain Da Liang 7 degrees Stomach Pure Brightness 8 degrees Hairy head Beginning of Summer Shi Chen 12 degrees Net Grain Full 0 degree Well Grain in Ear Chun Shou 16 degrees Well Summer Solstice 31 degrees Well Slight Heat Chun Huo 9 degrees Willow Great Heat 3 degrees Extended net Beginning of Autumn Chun Wei 18 degrees Extended net Limit Heat 15 degrees Wings White Dew Shou Xing 12 degrees Chariot Autumnal Equinox 10 degrees Horn Cold Dew Da Huo 5 degrees Root Descent of Frost 5 degrees Room Beginning of Winter Xi Mu 10 degrees Tail Slight Snow 7 degrees Winnowing-basket The following shows the simulated phenomena around 428 BC.
By S. Y. Ho
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