Gaocheng Astronomical Observatory, also known as the Dengfeng Observatory, is an observatory in

Duke of Zhou Dan, Duke Wen of Zhou, commonly known as the Duke of Zhou, was a member of the royal family of the early Zhou dynasty who played a major role in consolidating the kingdom established by his elder brother King Wu. He was renowned for acting as ...

's shrine, Gaocheng Town, near

Dengfeng Dengfeng (; postal: Tengfeng) is a county-level city of Henan Province, China. It is under the administration of the prefecture-level city of Zhengzhou. Dengfeng has an area of and a population of 630,000. It occupies the southwestern corner of ...

Henan province Henan; alternatively Honan is a province in Central China. Henan is home to many heritage sites, including Yinxu, the ruins of the final capital of the Shang dynasty () and the Shaolin Temple. Four of the historical capitals of China, Luo ...

, China. This site has a long tradition of astronomical observations, from the time of the

Western Zhou The Western Zhou ( zh, c=西周, p=Xīzhōu; 771 BC) was a period of Chinese history corresponding roughly to the first half of the Zhou dynasty. It began when King Wu of Zhou overthrew the Shang dynasty at the Battle of Muye and ended in 77 ...

up to the early

Yuan dynasty The Yuan dynasty ( ; zh, c=元朝, p=Yuáncháo), officially the Great Yuan (; Mongolian language, Mongolian: , , literally 'Great Yuan State'), was a Mongol-led imperial dynasty of China and a successor state to the Mongol Empire after Div ...

. There is also a

gnomon A gnomon (; ) is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields, typically to measure directions, position, or time. History A painted stick dating from 2300 BC that was ...

used for the Da Yan calendar in 729 AD and the great observatory of the Yuan dynasty. As part of the "Dengfeng Historic Monuments of Dengfeng 'in the Center of Heaven and Earth'" the observatory was listed as a

UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

in 2010.

History

Western Zhou

It is believed that the

(''c.'' 1042 BC) had erected at this place a ''Ceyingtai'' (observatory measuring the shade or

) to observe the Sun, as he believed the area to be the centre of heaven and earth. His interest in mathematics, astronomy/astrology is reported in the

Zhoubi Suanjing The ''Zhoubi Suanjing'', also known by many other names, is an ancient Chinese astronomical and mathematical work. The ''Zhoubi'' is most famous for its presentation of Chinese cosmology and a form of the Pythagorean theorem. It claims to pr ...

Tang dynasty

The astronomer

Yi Xing Yixing (, 683–727) was a Buddhist monk of the Tang dynasty, recognized for his accomplishments as an astronomer, a reformer of the calendar system, a specialist in the ''I Ching, Yijing'' (易經), and a distinguished Buddhist figure with exp ...

(683–727) of the

Tang dynasty The Tang dynasty (, ; zh, c=唐朝), or the Tang Empire, was an Dynasties of China, imperial dynasty of China that ruled from 618 to 907, with an Wu Zhou, interregnum between 690 and 705. It was preceded by the Sui dynasty and followed ...

built 20 standardized gnomons spread out over China to measure the

equation of time The equation of time describes the discrepancy between two kinds of solar time. The two times that differ are the apparent solar time, which directly tracks the diurnal motion of the Sun, and mean solar time, which tracks a theoretical mean Sun ...

dependent on the geographical location. Following a proposition of Liu Zhuo from 604 AD, 10 of these were aligned along the meridian 114° east of

Greenwich Greenwich ( , , ) is an List of areas of London, area in south-east London, England, within the Ceremonial counties of England, ceremonial county of Greater London, east-south-east of Charing Cross. Greenwich is notable for its maritime hi ...

from Central Asia down to Vietnam in order to determine the circumference of the Earth and deviations from a perfect sphere. One of these 10 observatories was situated at Gaocheng. The observations were used to establish the Da Yan calendar. South of the observatory, in the temple dedicated to Zhou Gong can be found a Shigui chart made by Yi Xing. According to the ''Zhou Li'' (

Rites of Zhou The ''Rites of Zhou'' (), originally known as "Officers of Zhou" (), is a Chinese work on bureaucracy and organizational theory. It was renamed by Liu Xin to differentiate it from a chapter in the '' Book of History'' by the same name. To rep ...

) this place is the center of the Earth.

Yuan dynasty

The great observatory was built in 1276 in the early

on the order of

Kublai Khan Kublai Khan (23 September 1215 – 18 February 1294), also known by his temple name as the Emperor Shizu of Yuan and his regnal name Setsen Khan, was the founder and first emperor of the Mongol-led Yuan dynasty of China. He proclaimed the ...

and was designed by astronomers

Guo Shoujing Guo Shoujing (, 1231–1316), courtesy name Ruosi (), was a Chinese astronomer, hydraulic engineer, mathematician, and politician of the Yuan dynasty. The later Johann Adam Schall von Bell (1591–1666) was so impressed with the preserved astro ...

(1231–''c.''1215) and Wang Xun (1235–1281) to observe the movement of the sun and the stars and to record time. It was built of stones and bricks. It has two parts: the body and ''shigui'' (also called ''the ruler to measure the sky''). It is 9.46 meters high by itself, and 12.62 meters high if the 2 cabinets on the top are included. The somewhat unconventional gnomon is a bar mounted horizontally between the two cabinets. The shigui extending to the far north is 31.19 meters long and 0.53 meters wide. It is made up of 36 square stones with two parallel waterways on it to check its levelness. The location of shigui is in accordance with the direction we take today to measure the meridian. During measurement, a beam is put across the grooves. Jingfu (an instrument with many holes) on the waterways is used to measure the shadow, whose precision is within 2 millimeters. At winter solstice, the length of the shadow at noon is nearly as long as the shigui. The very precise observations served for the new Shoushi calendar (Season-Granting Calendar) of 1281, which was in use for 364 years. It was by far the most advanced calendar for its time; the length of the

tropical year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronom ...

was determined to 365 d 5 h 49 m 20 s, a value in accord with the value of the

Gregorian Calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...

, but obtained 300 years earlier. In 1787,

Laplace Pierre-Simon, Marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French polymath, a scholar whose work has been instrumental in the fields of physics, astronomy, mathematics, engineering, statistics, and philosophy. He summariz ...

applied these measurements to check his calculations on the secular changes of the obliquity of the ecliptic and the eccentricity of the Earth's orbit. It is the first in a series of 27 observatories built in the early Yuan dynasty.

References

External links