Chinese Astronomy

Copyright by S.Y. Ho

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 (ecliptic in Western astronomy) are divided into twelve sections.

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 clepsydra showed the midnight. At the midnight the sun is right on the opposite side to the star (mansion) which crossed the meridian.

Through observations, ancient astronomers found that the sun and planets seems to move in an anticlockwise direction along zodiac. Because 12 branches were arranged in a clockwise direction, astronomers set up the 12 Ci system for measuring the locations of sun and planets.

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.


Ninefold Heavens   "....Whose compass measured out the ninefold heavens?  ......" Heavens Questions by Qu Yuan (c. 340-278 B.C.)  Ninefold heavens are


(Pingyin)


The outermost
Zongdong

the following heavens are carried along by this spherical shell as it rotates
8th
Liexiu

contains three Enclosures and twenty-eight Mansions (Fixed stars)
7th
Tianxing

contains Saturn
6th
Suixing

contains Jupiter
5th
Yinghuo

contains Mars
4th
Taiyang

contains Sun
3rd
Taibai

contains Venus
2nd
Chenxing

contains Mercury
1st
Taiyin

contains Moon


12 Zodiac Animals are rat, ox, tiger, rabbit, dragon, snake, horse, sheep, monkey, rooster, dog and pig. There are many legends in the Chinese folklore about 12 zodiac animals, but the Rishu (almanacs) of bammbo slips excavated from tombs at Yunmeng Shuihudi and Tianshui Fangmatan show that the 12 zodiac animals were probaly used as a predictive tool for thief. Slips also show that the twelve animals are different from today's signs.

The rotating cycle of twelve animal signs was a folk method for naming the years in traditional China. Everybody knows which animal sign he or she is born under. Instead of asking directly how old a person is, people often ask for animal signs to simply know who is older among friends and acquaintances.




By S. Y. Ho
Astronomy Page