In China, as in many other cultures, there is evidence of interest and observation of the sky from many years earlier than written documentation suggests. Examples of pottery now held at the Beijing Ancient Observatory and dated to the Neolithic period (over 5000 years ago) show images of the sun, and intricately carved animal shells and bones depict images of the stars as well as astronomical events such as star explosions which may date back as far as 1400 BC.
It is possible that the observation of the sky in a scientific sense was first undertaken as a way of marking time and recording events within a recurring pattern in order to create a calendar. A calendar marks the seasons and helps farmers to know when to plant and harvest their grain. Like many ancient societies, China based its calendar upon the phases of the moon but then added extra months. This was because a solar year is not evenly divisible by an exact number of lunar months – there are about 12.37 lunar months during a solar seasonal year – so without the extra months the seasons would drift each year. This is called a luni-solar calendar. The Chinese calendar therefore had a thirteen-month year every two or three years. In May 2005, some relics of this early astronomical activity were uncovered with the discovery of the oldest astronomical observatory known in China today. This structure is located in the Shanxi 山西 province of China and dates from the Longshan 龙山 period (2300–1900 BC). This vast carved platform, measuring sixty metres in diameter, was used to locate the rising of the sun at the different periods of the year.
As tradition dictated that the rulers of China, first kings and later emperors, should receive their political mandate from the sky, astronomy soon became a dominant science in China. The main responsibility of political power was to keep the Earth in total harmony with the sky. This obligation was called the ‘Mandate of Heaven’ and the emperor himself was called Tian Zi 天子, the Son of Heaven. The stars themselves were bestowed with astrological meaning, both enabling predictions that influenced daily life as well as major political strategies, and thus astronomy swiftly became a powerful political tool.
One very positive consequence of the Mandate of Heaven on Chinese history was the appointment of a special group of imperial officers who included astronomers, astrologers and meteorologists. These officials were ordered by the emperor to monitor the sky, looking for astrological omens and astronomical phenomena. Unlike any other country, China is the only place where astronomical observations took place uninterrupted for 4000 years and this surveillance led to many important astronomical discoveries. Special care was taken in China to record the appearance of unexpected events in the sky, such as eclipses, comets or star explosions. The most ancient document known to exist on comets is a spectacular drawing, now called the Silk Atlas of Comets that was found in a tomb from the Mawangdui site near Changsha, in Hunan province, south China in 1973. The Atlas dates from around 185 BC, and is now held at the Hunan Provincial Museum. It depicts a variety of comet formations that demonstrate careful observations made over several centuries earlier, including astronomical phenomena such as ‘cloud vapour divinations’ and ‘star divinations’ which would have aided the prediction of victory or defeat in battle. Different kinds of comet heads and tails are painted on the manuscript, showing that comet observation at this time was already very precise, and done according to scientific classification.
Silk Atlas of Comets from the Hunan Provincial Museum
Source image taken from Album of Relics of Ancient Chinese Astronomy, Zhongguo Gudai Tianwen Wenwu Tuji, CASS (Chinese Academy of Social Sciences, Institute of Archaeology), 1980. Beijing. 8, 57.
Regular observations also led to the discovery of star explosions. Known today as ‘supernovae’, these explosions, that signal the death of a star, are visible only briefly in the sky, appearing as a transitory ‘new’ star that suddenly appears and then fades after a few weeks. Ancient Chinese astronomers poetically named these explosions ‘guest stars’ and a full catalogue of them, maintained over centuries, carefully notes their various appearances and offers accurate information about their positions which has enabled modern astronomers to find remnants of these explosions in the sky today.
To locate events such as these easily, Chinese astronomers took care to describe the visible stars with great accuracy. The first star catalogues may have been produced during the Warring States period (475–221 BC) and were transmitted to us by the famous historian Sima Qian 司马迁, from the early Han dynasty. From this period we can first date the division of the sky into numerous small constellations, all associated with memorable images from the Chinese empire. Using simple instruments known as armillary spheres, a combination of a sighting tube with graduated circles that enabled measurement of the positions of the stars, astronomers first produced lists of stars with associated numbers which corresponded to their positions in the sky.
Armillary sphere at the Beijing Ancient Observatory. Image taken from Wikipedia
An armillary sphere, dated 1771, from plate LXXVII of the 12th edition of the Encyclopedia Britannica.
Later on, the first star maps were also produced. These showed the relative positions of the stars as they appeared in the sky as a drawing. But evidence for drawn star maps does not appear until many years later. In historical texts, an early star map is attributed to the astronomer Chen Zhuo 陈桌 living in the third century AD but unfortunately this map has not survived. At the turn of the twentieth century, Marc Aurel Stein, a Hungarian-born, British archaeologist uncovered a hand drawn star chart in a Buddhist cave complex in Dunhuang 敦煌, China. This chart, now known as the Dunhuang Star Atlas and probably dating from before AD 700, is the earliest known preserved star map in existence in the world.
The long tradition of mapping the sky in China continued with the production of other spectacular star maps. Preserved today in the city of Suzhou 苏州 is a carved stone example that was designed in AD 1193 as a teaching aid for the young future emperor Ningzong 宁宗 (1168–1224).