Gaocheng Astronomical Observatory

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Gaocheng Astronomical Observatory. It was built in 1276. Dengfeng Observatory.jpg
Gaocheng Astronomical Observatory. It was built in 1276.
Gaocheng Astronomical Observatory
Simplified Chinese 登封观星台
Literal meaningGaocheng Astronomical Observatory

Gaocheng Astronomical Observatory, also known as the Dengfeng Observatory, is a World Heritage Site in Duke of Zhou's shrine, Gaocheng Town, near Dengfeng in Henan province, China. This site has a long tradition of astronomical observations, from the time of the Western Zhou up to the early Yuan dynasty. There is also a gnomon used for the Da Yan calendar in 729 AD and the great observatory of the Yuan Dynasty.

World Heritage Site place listed by the UNESCO as of special cultural or natural significance

A World Heritage Site is a landmark or area which is selected by the United Nations Educational, Scientific and Cultural Organization (UNESCO) as having cultural, historical, scientific or other form of significance, and is legally protected by international treaties. The sites are judged important to the collective interests of humanity.

Duke of Zhou Duke of Zhou

Dan, Duke Wen of Zhou, commonly known as the Duke of Zhou, was a member of the royal family of the Zhou dynasty who played a major role in consolidating the kingdom established by his elder brother King Wu. He was renowned for acting as a capable and loyal regent for his young nephew King Cheng, and for successfully suppressing the Rebellion of the Three Guards and establishing firm rule of the Zhou dynasty over eastern China. He is also a Chinese culture hero credited with writing the I Ching and the Book of Poetry, establishing the Rites of Zhou, and creating the yayue of Chinese classical music.

Dengfeng County-level city in Henan, Peoples Republic of China

Dengfeng is a county-level city under the jurisdiction of Zhengzhou, the capital of Henan Province, China. In ancient times, it was known as Yangcheng.

Contents

History

Western Zhou

It is believed that the Duke of Zhou (c. 1042 BC) had erected at this place a Ceyingtai (observatory measuring the shade or gnomon) to observe the Sun. His interest in mathematics, astronomy/astrology is reported in the Zhoubi Suanjing.

Gnomon part of a sundial

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.

<i>Zhoubi Suanjing</i> literary work

The Zhoubi Suanjing, or Chou Pei Suan Ching (周髀算经), is one of the oldest Chinese mathematical texts. "Zhou" refers to the ancient Zhou dynasty (周) c. 1046–771 BCE; "Bi" means thigh and according to the book, it refers to the gnomon of the sundial. The book is dedicated to astronomical observation and calculation. "Suan Jing" or "classic of arithmetic" were appended in later time to honor the achievement of the book in mathematics.

Tang Dynasty

The astronomer Yi Xing (683–727) of the Tang Dynasty built 20 standardized gnomons spread out over China to measure the equation of time 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 from Central Asia down to Vietnam in order to determine the circumference of the Earth and derivations from a perfect sphere. One of these 10 observatories was situated at Gaocheng. The observations were used to establish the Da Yan calendar.

Yi Xing, born Zhang Sui, was a Chinese astronomer, mathematician, mechanical engineer and Buddhist monk of the Tang dynasty (618–907). His astronomical celestial globe featured a clockwork escapement mechanism, the first in a long tradition of Chinese astronomical clockworks.

Equation of time

The equation of time describes the discrepancy between two kinds of solar time. The word equation is used in the medieval sense of "reconcile a difference". 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 with uniform motion. Apparent solar time can be obtained by measurement of the current position of the Sun, as indicated by a sundial. Mean solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time would resolve to zero.

Greenwich town in south-east London, England

Greenwich is an area of south east London, England, located 5.5 miles (8.9 km) east-southeast of Charing Cross. It is located within the Royal Borough of Greenwich, to which it lends its name.

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) this place is the center of the Earth.

The Rites of Zhou, originally known as "Officers of Zhou" is actually 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 work, it was included along with the Book of Rites and the Etiquette and Ceremonial – becoming one of three ancient ritual texts listed among the classics of Confucianism.

Yuan Dynasty

The great observatory was built in 1276 in the early Yuan dynasty on the order of Kublai Khan and was used by Guo Shoujing (1231–c.1215) and Wang Xun (1235–1281) to observe the movement of the sun, the stars and record time.

Yuan dynasty former Mongolian-ruled empire in Eastern and Northeastern Asia

The Yuan dynasty, officially the Great Yuan, was the empire or ruling dynasty of China established by Kublai Khan, leader of the Mongolian Borjigin clan. It followed the Song dynasty and preceded the Ming dynasty. Although the Mongols had ruled territories including modern-day North China for decades, it was not until 1271 that Kublai Khan officially proclaimed the dynasty in the traditional Chinese style, and the conquest was not complete until 1279. His realm was, by this point, isolated from the other khanates and controlled most of modern-day China and its surrounding areas, including modern Mongolia. It was the first foreign dynasty to rule all of China and lasted until 1368 which ended in Ming dynasty defeating the Yuan dynasty, the rebuked Genghisid rulers retreated to their Mongolian homeland and continued to rule the Northern Yuan dynasty. Some of the Mongolian Emperors of the Yuan mastered the Chinese language, while others only used their native language and the 'Phags-pa script.

Kublai Khan founding emperor of the Yuan Dynasty, grandson of Genghis Khan

Kublai was the fifth Khagan of the Mongol Empire, reigning from 1260 to 1294. He also founded the Yuan dynasty in China as a conquest dynasty in 1271, and ruled as the first Yuan emperor until his death in 1294.

Guo Shoujing Medieval Chinese astronomer and mathematician

Guo Shoujing, courtesy name Ruosi (若思), was a Chinese astronomer, engineer, and mathematician born in Xingtai, Hebei who lived during the Yuan Dynasty (1271–1368). The later Johann Adam Schall von Bell (1591–1666) was so impressed with the preserved astronomical instruments of Guo that he called him "the Tycho Brahe of China." Jamal ad-Din (astronomer) cooperated with him.

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. The length of the tropical year was determined to 365 d 5 h 49 m 20 s, a value in accord with the value of the Gregorian Calendar, but obtained 300 years earlier.

A tropical year is the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice. Because of the precession of the equinoxes, the seasonal cycle does not remain exactly synchronized with the position of the Earth in its orbit around the Sun. As a consequence, the tropical year is about 20 minutes shorter than the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars.

In 1787, Laplace 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.

Heritage status

As part of the "Dengfeng Historic Monuments of Dengfeng 'in the Center of Heaven and Earth'" the observatory has been listed as UNESCO World heritage in 2010. [1]

See also

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References

  1. Centre, UNESCO World Heritage. "Historic Monuments of Dengfeng in "The Centre of Heaven and Earth"". whc.unesco.org. Retrieved 2017-08-19.

Coordinates: 34°24′10″N113°08′27″E / 34.40278°N 113.14083°E / 34.40278; 113.14083