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 actin ...

's shrine, Gaocheng Town, near

Dengfeng Dengfeng (; postal: Tengfeng) is a county-level city of Henan Province, South Central 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 so ...

Henan province Henan (; or ; ; alternatively Honan) is a landlocked province of China, in the central part of the country. Henan is often referred to as Zhongyuan or Zhongzhou (), which literally means "central plain" or "midland", although the name is al ...

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

Western Zhou The Western Zhou ( zh, c=, p=Xīzhōu; c. 1045 BC – 771 BC) was a royal dynasty of China and 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 when the Quanrong n ...

up to the early

Yuan dynasty The Yuan dynasty (), officially the Great Yuan (; xng, , , literally "Great Yuan State"), was a Mongol-led imperial dynasty of China and a successor state to the Mongol Empire after its division. It was established by Kublai, the fif ...

. 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. History A painted stick dating from 2300 BC that was excavated at the astronomical site of Taosi is the ...

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 is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) aimed at promoting world peace and security through international coope ...

World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for ...

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'' () is one of the oldest Chinese mathematical texts. "Zhou" refers to the ancient Zhou dynasty (1046–256 BCE); "Bì" literally means "thigh", but in the book refers to the gnomon of a sundial. The book is dedicated to ...

Tang Dynasty

The astronomer

Yi Xing Yi Xing (, 683–727), born Zhang Sui (), was a Chinese astronomer, Buddhist monk, inventor, mathematician, mechanical engineer, and philosopher during the Tang dynasty. His astronomical celestial globe featured a liquid-driven escapement, the ...

(683–727) of the

Tang Dynasty The Tang dynasty (, ; zh, t= ), or Tang Empire, was an Dynasties in Chinese history, imperial dynasty of China that ruled from 618 to 907 AD, with an Zhou dynasty (690–705), interregnum between 690 and 705. It was preceded by the Sui dyn ...

built 20 standardized gnomons spread out over China to measure the

equation of time In mathematics, an equation is a formula that expresses the equality of two expressions, by connecting them with the equals sign . The word ''equation'' and its cognates in other languages may have subtly different meanings; for example, in F ...

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 a town in south-east London, England, within the ceremonial county of Greater London. It is situated east-southeast of Charing Cross. Greenwich is notable for its maritime history and for giving its name to the Greenwich ...

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 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 replace a lost ...

) 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 ; Mongolian script: ; (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 of the Yuan dynasty of China and the fifth khagan-emperor of ...

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 astr ...

(1231–''c.''1215) and Wang Xun (1235–1281) to observe the movement of the sun, the stars and 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 2 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 shade, 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 of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time ...

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 was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years d ...

, but obtained 300 years earlier. In 1787,

Laplace Pierre-Simon, marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French scholar and polymath whose work was important to the development of engineering, mathematics, statistics, physics, astronomy, and philosophy. He summarized ...

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