History of Early Chinese Astronomy – by Albert Lim

Early Chinese astronomy was influenced to a large extend by religious, cultural as well as the political views of that prevailing time. To the Chinese, their early religion was such that god was the maker of the world and they rarely speak beyond it. The religious view as early as around 2 BC was that the Emperor of China was a devine appointment and that he was the "son of God" and ruler of  "all under the heavens".  China was thought to be at the centre of a flat and square earth (because of the 4 cardinal points, N,S,E and W ) and the middle of the Chinese empire under the emperor's rule corresponds to the North Celestial Pole which is supposingly also located at the center of a spherical heaven above.
The concept was that the Chinese god "Shang-ti" ( meaning "upper earth" - strictly “ti” here could also be translated as ground or land but it’ use in this instance refers to “earth”) was in control of the heavens, while the Emperor, who was supposingly "the son of God", rules the corresponding land under the heaven. The emperor's rule and events happening on Earth was thought to have a direct influence on the of events in heaven. The Chinese interpreted heavenly consequences as changes in the sky, sometimes with sudden sightings and appearances of new stars, comets or eclipses. The emperor is thought to maintain harmony of both heaven and earth - this is because heaven and earth are thought in such a way that all in it including the emperor, the people, the land, the god and the cosmos are intimately connected like a single living organism. Chaos in one brings about chaos in the other. As an example, it is widely believed among the Chinese that if an emperor is unjust or have governed badly and unwisely, the heavens will be affected by his bad behaviour on earth and will show it by sudden appearance of “Kho hxing” (Guest Star) or by unpredicted changes in the sky.

On the other hand, "When a wise prince occupies the throne, the moon follows the right way"  in accordance to the work of Shih-shen in 4 BC. Thus, the fate of man was not simply ruled by the Gods ; good or bad luck in accordance to Chinese culture was determined by virtue and by following correctly the commands of the heavens. Heaven was thus regarded as the highest god with the Emperor as heaven’s son and also the head of the state religion.

Fig 1 - The Chinese Tychonic Theory of the Solar System. Chinese characters from top down : Fixed Stars, Saturn, Jupiter and Mars. Across from centre to right : Sun, Mercury and Venus. Lower characters left to right : Earth and Moon.

In ancient China, astronomy was also a serious business intimately connected with the government and civil administration. Each emperor would therefore have a large staff of imperial astronomers, usually headed by a Chinese equivalent of an Astronomer Royal, who keep astronomical records and made predictions of celestial events. Considering the religious implications mentioned above, it is not surprising that astronomical records are often closely guarded political secrets. There is an interesting account dating to 855 A.D about the intellectual Chinese observer and monk I-Hsing pertaining to one his friend who was imprisoned on a charge of murder. At his temple of the Armillary sphere, I-Hsing ordered 7 pigs to be caught and put into a big pot. Subsequently, the emperor complained that the head of the Astronomical Bureau had found the constellation of the Great Bear missing. I-Hsing then told the emperor that since there were no previous record of any disappearance of the Great Bear, and that there was only 1 nearly similar occurrence when Mars was lost, that the Heavens must be giving the emperor an important warning - perhaps of  frost or drought. I-Hsing then suggested that the emperor with his great virtue could influenced the stars and thus avert the great disaster on earth. “What would most affect them (meaning heaven) would be a decision on your part in favour of life rather than death. So do we Buddhist preach forgiveness for all”. The emperor agreed and issued a general amnesty. Following, the seven stars of the Great Bear reappeared in their places in the heavens and when the pot was opened, the 7 pigs have disappeared. Such was the mastery of I-Hsing over the stars of the Great Bear. It becomes more comprehensible if we consider that now we know that I-Hsing actually wrote certain tracts and books about their astrological significance and astronomical relations.
As a consequence of an emperor’s devine connection to the heavens, it also became customary that with each change of rein and certainly with each change of dynasty, each new ruler would need to draw up a new Chinese calendar. The establishment of a calendar by the imperial ruler and it’s acceptance by the people who needed the calendar for agricultural reasons was firstly to establish a new mandate and secondly, to grant a fresh set of disposition of  celestial influences from the heavens. Since calendars were politically sensitive, it naturally follows that astronomical documentation of old calendars rarely survive.

Fig 2 - Tang Dynasty Mirror shows cycles in Chinese calendar. Innermost circle shows 4 cosmological animals depicting the 4 cardinal points N,S,E,W and the 4 seasons. Next ring shows 12 animals signifying the 12 year Jupiter cycle. Outer ring has 28 creatures representing the 28 Chinese ‘hsiu’ or stellar station.

Thus the science of Chinese astronomy came to be distinguished since very early times into what is known as lifa, (translated means 'calendrical methods') and tianwen  (translated in  some books as 'celestial patterns' but more correctly translated as 'astronomy'). ‘Lifa’ consisted of  measurements, record-keeping and calculations aimed at ascertaining regularities of celestial phenomena while ‘tianwen’ practitioners watched for new and unpredicted celestial phenomena and attempt to interpret their significance for the emperor and the people. Because of the many reins in China and the fact that the calendar is seen as a reflection political power for each rein, no fewer than 102 different calendars were produced between 370 BC and 1851. Many of these calendars also had star tables and ephemerides of the planets in addition to sometimes detailed lunar and solar information, making them excellent benchmarks for evaluating historical progress of astronomy through the ages. With the political climate from early times constantly favouring new calendars, the imperial astronomers first formulated their early calendars on lunar motion because changes in the moon were easily observed. Later, over longer observational periods of the sun, solar calendars which were more convenient for civil purposes and more closely follow the seasons were formulated. Besides these calendars, the Chinese also operated a Day Count system at a very early time.
The medieval tide of practical astronomy in China was such that it required astronomical observations to be recorded accurately and in great detail. This was because the Chinese system for predictions of celestial events was to a large extent empirical and relied on information cumulated from past astronomical records. This necessitated observations to be recorded in detail for them to be useful. Unlike the Greeks, the Chinese did not find it necessary to express observed celestial events in highly theoretical and or geometrical form. The result is that the Chinese now posses the longest continuous span of detailed astronomical records in the world. These voluminous Chinese observations are proving to be of significant importance to modern day astronomy in some key areas as described below.

a) Comets, Meteors and Meteorites
Compared to the rest of the world, the Chinese records of comets, meteors and meteorites are by far the most complete. This was pointed out by Oliver at the beginning of his excellent monograph on cometary phenomena. It should also be noted that the computation of approximate orbits for 40 comets based on observations earlier than AD 1500 were almost exclusively Chinese. A typical example would be the famous Halley's comet observed by Halley himself in 1682. Halley’s comet had a profound influence on astronomy not just because it's periodicity was established before any other but also because it's history could be traced accurately for over 2000 years ! This is almost entirely due to the fact that the Chinese made careful observations of all comets, which the Chinese called ‘hui hsing’ (meaning comet) or ‘sao hsing’ (meaning brush star), since very early times.  The earliest Chinese record of a comet which might be Halley’s was from 467 BC but historians are unable to confirm this due to a lack of data. Chinese record of the comet of 240 BC observed in the 7th year of Chhin Shih Huang Ti however, was known without doubt to be Halley's comet. Apart from the fact that the Chinese were the first to observed that a comet's tail always points away from the sun, nearly every reappearance of Halley's comet in it’s 76 year cycle since had been documented in Chinese astronomical history.

Fig 3 - Drawing of a comet passing between the ‘hsiu 1’ and ‘Chen’ on the night of 28th Oct 1664.

The Chinese also amassed a vast amount of highly detailed observation of ‘liu hsing’ (meteors) and ‘liu hsing yu’ (meteor showers). They also recorded actual falls of meteorites onto the earth's surface and called them ‘hsing yun’. It is interesting to note that a very intense Leonid shower was recorded as early as 931 AD. by the Chinese. The shower records were so complete that Biot was able to make a statistical account of frequencies for the Sung period from 960 and 1275 AD and conclude not only the direction towards the cardinal points but also the colours of the display. In all, Chinese history had recorded nearly 500 meteor showers !

b) Sunspots
Sunspots generally escaped records by the Europeans because of their intrinsic belief that the heavens must be perfect. In Europe, Galileo discovered sunspots from his telescopic observations at the end of 1610 AD. Again by comparison, the Chinese sunspot records were by far the most complete we have. The Chinese had sunspot records at the time of Liu Hsiang at 28 BC, nearly a thousand years before the first references were made to it by the West. Between then and 1638, the Chinese had accumulated 112 descriptions of outstanding spots in official history. The Chinese refer to these black spots as ‘hei chhi’, ‘hei tzu’ or ‘wu’. ( ‘hei’ in Chinese translates to ‘black’ ). de Moidrey in collaboration with P. Huang was also able to find a reasonable approximation to the 11 year sunspot cycle from ancient Chinese data on sunspots. S. Kanda of Japan later confirmed Moidrey's results and was able to conclude the cycle period as of between 10.38 to 11.28 years. Several modern astronomers are also attempting to use Chinese sunspot data to correlate between the periodicity of sunspot maxima and other phenomena such as aurorae.

c) Nova and Supernova
Nova and supernova phenomena are of extreme high importance to modern day astronomy in formulating current cosmological theories. The most ancient Chinese record of a nova is described in an oracle-bone dating back to about 1300 BC. An inscription on this oracle-bone ( see Fig 4 below ) reads in it's two central column of Chinese characters : "On the 7th day of the month, a chi-ssu day, a great new star appeared in the company with Antares." (hsin ta hsin ping Huo).

Fig 4 - The oldest record of a nova on an oracle-bone dating to early 1300 BC.

Another bone-inscription from the same time says that :"On the hsin-wei day the new star faded (or disappeared )." It seems highly probable that this second bone refers to the same star as the hsin-wei day is only 2 days after the first sighting. The Chinese used the term ‘hsin hsing’ ( meaning ‘new star’ ) for new stars appearing in the sky until sometime in the middle of the Han period. The Han astronomers replaced the term ‘hsin hsing’ with a technically better term ‘kexing’ meaning 'guest star'.
The great extent to which Chinese records of 'guest stars' are of high interests to modern day astronomers can be seen in the field of radio-astronomy.  In recent times, such collaboration among competent sinologist, practical astronomers and radio astronomers utilising Chinese records of 'guest stars' have greatly added to our astronomical knowledge. If the recorded position of a supernova were corrected for precession and corresponds well with a visible remnant, not only can the exact age of the remnant be determined but also it's rate of expansion. Specific exposition of these pertain to a Chinese record of the 'guest star' of 1054 AD which corresponds beyond any doubt to be the Crab Nebula (6,500 light years). Others recorded in 1006 and 1181 are now also known to correspond to PKS 1459-41 (between 5,500 to 10,000 light years) and 3C 58 (10,500 light years) respectively.

There have been prior arguments about the reliability of Chinese records of 'guest stars' and whether they were invented by the early astronomers to criticise the government. Lundmark seems to put the matter at rest by validating the reliability of Chinese records. He had plotted Chinese records of 'guest stars' in accordance to their galactic co-ordinates and found that they had a spatial distribution within our own galaxy. This agrees perfectly with our present day understanding of where novas should be located. Lundmark argues convincingly that if 'guest stars' were indeed invented by the early Chinese astronomers to criticise the government, then it is highly unlikely that they would all be located  in the correct part of the sky.

d) Eclipses & Earth’s Rotation
The early Shang people of China had recorded on oracle-bones 6 lunar eclipses at BC 1361, 1342, 1328, 1304 and 1217 and one solar eclipse at BC 1217. Although the Shang people had recorded lunar eclipses for calendarical rather than astrological reasons and all eclipse observations by the Chinese were largely empirical for prediction purposes, they nevertheless provide the most useful data for studying the long term change in the rotation of the Earth. By utilising Chinese pretelescopic eclipse records, astronomers today have deduced that the length of day (LOD) of the earth should be increasing at an average of 1.7 millisecond per century over the last 2,700 years. In reality, the figure is from nearly zero to about 5 milliseconds due to a number of reasons currently under investigation.