What did Chinese Astronomers Discover? Legacy of the Chinese AstronomersLearn about the fascinating history of Chinese astronomers and their contribution to astronomy from as far back as 2000BC.
One of those civilizations was the Babylonian Empire, and the other is China. Their astronomical contributions have been in some ways massively different, with the astronomy of ancient Babylon being the one brought to us by the Greeks, the astronomy of China grew up independently, steeped in tradition, its full glories coming to be recognized in the West only in the twentieth century.
The ancient civilisations of China and Babylon have been geographically distinct; however, they had several features in common, possibly the most significant being that they have been each vast river cultures. In China's case, this meant the Huang Ho (Yellow River) and the Yangtze Rivers. Could it be that the demanding situations concerned with controlling, and farming along, mighty rivers gave an early stimulus to that complicated and organised mode of living that we call civilisation? Great rivers have been additionally natural arteries for trade and communication, and the great skies that went with those flat landscapes must have made the ancients continuously mindful of the movement of the heavenly bodies. As cultures become more complicated and used written records, people started to understand that celestial rhythms may well be used to organise public and religious life.
As far back as 2000 BC, astronomy was having a long-lasting impact on Chinese tradition. The rock carvings at Jiangjunya, in modern Jiangsu, obviously depict the Sun, Moon, bright stars and the Milky Way, and most likely represent the oldest surviving star maps in the World. By the time of the Shang Kingdom in l500 BC, the shoulder blades of oxen and deer were being used for purposes of divination. Chinese archaeologists have discovered many such bones carrying ancient inscriptions recording astronomical events.
Chinese Astronomers in a Science of the Kings
China is unique in its astronomical historical past for the run of surviving observations its civilisation has produced, spanning thousands of years. This derives from the method by which traditional Chinese culture saw the heavens, the Earth and political balance as being interconnected. In this culture, the King, and later the emperor, have been seen as a divine personage who carried upon his shoulders the heavy burden of the peaceful ordering of the World.
If an Emperor was wise and just, then all went well, the rivers didn't burst their banks, there were no epidemics, and harvests were abundant. And what's more, the heavenly patterns proceeded with an ordered regularity. But if he was unjust, then even the heavens went out of kilter, as 'guest stars', such as comets or supernovae, disrupted the nightly peace, the Moon became blood-red, and the Sun was attacked by evil dragons.
It was as a result of its political and religious position in giving guidance to the emperor that serious astronomy in China was once kept very much inside of a specific organisation in the Mandarin class system: the Astronomy Bureau. Just as these days the CIA would not welcome outsiders picking up, interpreting, and broadcasting "top secret" intelligence, so Imperial China discouraged non-Mandarins from interfering with "sensitive" astronomical knowledge. It was because the Chinese have been keeping sky records for so long that they became mindful of emerging patterns.
By 500 BC they had recognised the presence of a 19-year trend in what we'd later come to name the Metonic cycle, and by AD 600 had advanced empirical methods enabling them to make quite dependable lunar and solar eclipse predictions. They have been, however, very much aware of an incompatibility between two necessary methods of reckoning time - the day-by-day convenience of a Moon phase calendar and the agricultural year of fixed seasons ruled by the Sun's movement through the solstices and equinoxes.
It was calendrical astronomy, with its purpose of advising the emperor in the ordering of creation that supplied the great and continuing stimulus to Chinese astronomy. From far-off antiquity to fairly modern times, records were compiled, studied and analysed, and great mathematics cycles were discerned inside them. It was through this method, for instance, that the imperial astronomers had, by AD 500 established the solar year as 365.24 days, which is within a tiny fraction of the value accepted by modern astronomers.
But how did Chinese court astronomers go about the study of the heavens in practical terms? Firstly, they divided the sky into five "palaces" or zones, consisting of the "purple palace" of the circumpolar stars and 4 extra representing the east, west, south, and north places respectively.
As the astronomical bodies moved through those palaces, their positions and any abnormality were assiduously recorded. Secondly, they divided the celestial equator into 12 zones determined by the locations at which Jupiter stood at different points in its 12-year orbit. The Chinese additionally recognised around 284 separate star groups or constellations, although Chinese asterisms were made up of much smaller groupings than the ones we inherited from the ancient Middle East.
Measuring the height of the Sun at different seasons is always very important to the assembling of calendrical knowledge. At first, the Chinese astronomers did this with a bamboo pole about 2.5m (8ft) long, noting precisely how long the shadow was for a given day in the year. With a sufficiently long run of observations - over decades or centuries in all probability - such shadow observations could be averaged out to provide some pretty accurate results. This could be carried out even better when bamboo poles were replaced by great stone instruments, where a ray of sunlight passing through a small hole in a high tower was made to fall upon a water-levelled scale set in the exact plane of the meridian. One example is the 40-foot-high tower built by the astronomer Guo Shoujing in AD 1276, which still survives just about intact at Gaocheng.
Like their Greek counterparts, yet wholly independently of them, the Chinese erected huge bronze armillary rings as reference points to delineate the celestial equator, meridian and ecliptic, one of the earliest of which was once set up by Luoxia Hong in 12O BC. These "armillary spheres" could be used for out-of-the-meridian angular sightings of astronomical bodies, giving the equivalents of what modern astronomers name right ascension and declination angles. Several of these great armillary continue to exist, and along with being instruments of great accuracy for the time (working on equatorial coordinates); they have been pieces of exquisite beauty.
Chinese craftsmanship has long been mythical, not just in the more familiar porcelain and jade working, but in the casting of huge bronze artefacts. Chinese geometry Like all Chinese circular graduated tools, armillary spheres have been divided not into 360 degrees, but into 365 and quarter digits deriving from the daily units of the Sun's path around the sky. This astronomically precise, but geometrically clumsy number (365 and 1/4 is impossible to subdivide into holes like 90°) could have been one explanation for why China never advanced geometric astronomy and cosmology based upon spherical triangles and points inside a sphere. Indeed, Chinese scholars by no means formulated a 'philosophical geometry' as a means of envisaging space in the manner the Greeks did, with their inheritance of the Babylonian 12 zodiac divisions, each broken into 30 daily parts. This is, perhaps, the foundation of our 360° circles.
Chinese Astronomers Document Patterns in the Stars
Western astronomy was once constructed around Ptolemy's 48 constellations, but Chinese astronomers recognised just about 300. These have been made of smaller groupings, frequently of not more than six or seven stars. By the time the definitive Chinese planisphere was complied, as an educating aid to the future emperor Nan Tsung in AD 1193, there were 1,565 individually named stars. Most Chinese constellations are very old, and few corresponded to Western groupings. The stars of the Greek constellation Hydra (the Water Snake), for instance, are divided into more than three groups in the Chinese system.
East and West do share certain conspicuous asterisms, such as Orion's Belt - referred to as Shen, or the 'Union of Three' to the Chinese, and the Great Bear, or Northern Bushel. Modern scholars have noted that China lacked 'maritime' constellations, equivalent to Cetus the Whale or Cancer the Crab, preferring agricultural or military names, similar to Thein Lecch'ng, or the 'Celestial Ramparts', close to Aquarius. And there are some delightful star myths: Altair and Vega had been the herd boy and the spinning girl; while Antares seems to have been Orion's brother, with whom he quarrelled.
Chinese Astronomers and Cosmology
The Chinese by no means had a geometrically based cosmology like the Greeks, and so they believed China and her Emperors to occupy the centre of Creation. But Chinese cosmological concepts however handed through a few major conceptual developments. Central to all three cosmological systems that evolved between circa 500 BC and AD 500 was the significance of the polar axis of the Universe, around which the sky turned around. The most ancient cosmological scheme was referred to as the Kai Thein. Here the sky was seen as a canopy arching over a curved Earth somewhat like an upturned bowl, and at the bottom was an ocean. Then there was the Hun Thein, promulgated by Loxia Hong and Zhang Heng between 130 BC and AD 100. This understood Earth as a sphere, most likely floating in a great ocean, and surrounded by a spherical sky. This idea had its critics, though, who asked how the fiery Sun could move from west to east at night if it was necessary to move beneath the ocean on which the Earth floated. But the Xuan Ye theory was the most remarkable of all: space was seen as an infinite realm, through which astronomical bodies moved under the direction of a kind of wind.
It is interesting how other cultures develop what could be termed different 'intellectual styles'. While the Chinese had a practical geometry for surveying, map-reading, and architecture, they never evolved a science of proofs and axioms. However, Chinese mathematics made great development in complicated mathematics and algebra in a way that the Greeks did not. Chinese astronomers and astronomy remained a closed book to the West until very contemporary times. Marco Polo, the medieval traveller to China, mentioned little about it, and it was not until Jesuit missionary scientists to China wrote their books in the late 17th century that even its most elementary details were disclosed to European scholars. It has been in the twentieth century that Chinese astronomical culture came to be studied by outsiders, in large part in the wake of pioneering research into the Chinese scientific historical past by Dr Joseph Needham of Cambridge.
Now, both Chinese and Western scholars are working in combination to make the richness of China's astronomical legacy available to the world.
