Astronomy and Calendar in Ancient China


Astronomy is almost as old as the history of human kind. When primitive men were using simple tools to hunt and fish for food, they observed the position of the sun to decide when they would set forth and how far they should go. When they moved into an agricultural age, every action from tilling, sowing, and weeding to harvesting and storage had to be closely synchronized with the seasonal changes.


In the beginning, men determined the seasons solely by watching for changes in nature such as melting snow and budding willow trees. Gradually, they realized that the movement of the heavenly bodies were closely related to these seasonal changes and they were then able to determine the seasons and months by observing the sun, moon, and stars.


Divination based on celestial observations began when people contemplated the sun and how it provided light and warmth and when they wondered at the bright light of the moon in the darkness of night. It is easy to understand how primitive people might have admired and worshiped these two giant lights in the sky. Perhaps they imagined these celestial lamps were moved by magical creatures and, if that were so, it would be in their interests to study them. In the end, it did not matter if they were benign or evil for they had total control of the fate and well-being of humankind. This early interest in the sky was the first step in the development of astronomy.


Legend has it that in ancient times, Gongong and Zhuanxu fought one another in a territorial battle. Gonggong lost and, in his anger, he ran to the northwest corner of the earth and broke Mount Buzhou which was one of the eight pillars holding up the sky. The sky in the northwest collapsed, as did the ground in the southeast. As a result, the sun, moon, and stars in the sky glided towards the northwest corner, and the rivers, mud and sand flowed to the southeast corner. When ancient people could not understand the natural phenomena they observed, they made up various legends and myths to try to surmise the probable reasons.


The names of several stars can be seen early on in the Shang dynasty (ca. 1600–ca. 1100 BCE), carved onto oracle bones. In the Shi jing (Classic of songs), the oldest anthology of poems in China, there is the line, “In the seventh month the Big Fire descends; in the ninth month we hand out clothes.” This line refers to the Big Fire, which in Western astronomy is the star Antares in the constellation of Scorpius. The poem says it descended quickly in the southwest at dusk and that people took it as a sign that warm clothing would be needed in the ninth month. In the Warring States period (475–221 BCE), Shi Shenfu (nd) of the state of Wei observed and began to plot the stars. Shi’s Canon of Stars appeared during the Han dynasty (206 BCE–220 CE) and is considered the earliest set of star catalogue in the world.


Years, months, and days form the basic elements of the calendar. Early on, it was thought that the calendrical elements should be reasonably arranged. In the earliest times, the cycle from warm weather to cold and back again was one year and months were calculated by the cyclical waxing and waning of the moon. By the Qin dynasty (221–206 BCE), this gave way to a more precise method of calculation. Astronomers concluded that a year was 365.25 days, and a month was 29.53 days.


The Chinese calendar, which has been in use since the Shang dynasty, combined both the solar and the lunar calendars. Such a combination was necessary to maintain a consistency between months and seasons. If only the lunar calendar were used, the seasons would occur in different months from year to year.


In ancient China, a number of instruments were used for astronomical observation. For celestial measurement, there were sundials (both vertical and horizontal), and armillary spheres. Time keeping was done with sundials, water clocks and even incense clocks. To demonstrate the movement of heavenly bodies, astronomers had at their disposal celestial globes and orreries which could simulate the movements of planets and stars. There were also instruments that combined two or more of the above, such as the water-powered automatic armillary clock that measured and demonstrated celestial movement as well as kept time. These instruments were often built exclusively for the imperial observatory; not only were they the best of their kind, but they were built with the finest materials and pleasing decorations.

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