Gaocheng Astronomical Observatory
Encyclopedia
Gaocheng Astronomical Observatory, also known as the Dengfeng Observatory, is a World Heritage Site
in Duke Zhou Gong'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
. Actually, one can see a gnome used for the Da Yan calendar in 729 AD and the great observatory of the Yuan Dynasty.
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 Chou Pei Suan Ching
.
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.
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.
on the order of Kublai Khan
and was used by Guo Shoujing
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. 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.
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 and oldest surviving observatory in China.
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...
in Duke Zhou Gong's shrine, Gaocheng Town, near Dengfeng
Dengfeng
Dengfeng is a county-level city in Zhengzhou, Henan province. In ancient times, it was known as Yangcheng .Dengfeng has an area of 1220 square kilometers and a population of 630,000....
in Henan Province, China. This site has a long tradition of astronomical observations, from the time of the Western Zhou
Western Zhou
The Western Zhōu period was the first half of the Zhou Dynasty of ancient China. It began when King Wu of Zhou overthrew the Shang Dynasty at the Battle of Muye. C.H...
up to the early Yuan Dynasty
Yuan Dynasty
The Yuan Dynasty , or Great Yuan Empire was a ruling dynasty founded by the Mongol leader Kublai Khan, who ruled most of present-day China, all of modern Mongolia and its surrounding areas, lasting officially from 1271 to 1368. It is considered both as a division of the Mongol Empire and as an...
. Actually, one can see a gnome used for the Da Yan calendar in 729 AD and the great observatory of the Yuan Dynasty.
Western Zhou
It is believed that the Duke of ZhouDuke of Zhou
The Duke of Zhou played a major role in consolidating the newly-founded Zhou Dynasty . He was the brother of King Wu of Zhou, the first king of the ancient Chinese Zhou Dynasty...
had erected at this place a Ceyingtai (observatory measuring the shade or gnomon
Gnomon
The gnomon is the part of a sundial that casts the shadow. Gnomon is an ancient Greek word meaning "indicator", "one who discerns," or "that which reveals."It has come to be used for a variety of purposes in mathematics and other fields....
) to observe the Sun. His interest in mathematics, astronomy/astrology is reported in the Chou Pei Suan Ching
Chou Pei Suan Ching
The Zhou Bi Suan Jing, or Chou Pei Suan Ching, is one of the oldest and most famous Chinese mathematical texts. The title literally means The Arithmetical Classic of the Gnomon and the Circular Paths of Heaven....
.
Tang Dynasty
The astronomer Yi XingYi Xing
Yi Xing , born Zhang Sui , was a Chinese astronomer, mathematician, mechanical engineer,and Buddhist monk of the Tang Dynasty...
of the Tang Dynasty
Tang Dynasty
The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
built 20 standardized gnomons spread out over China to measure the equation of time
Equation of time
The equation of time is the difference between apparent solar time and mean solar time. At any given instant, this difference will be the same for every observer...
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
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...
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.
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
Rites of Zhou
The Rites of Zhou , also known as Zhouguan, is one of three ancient ritual texts listed among the classics of Confucianism. It was later renamed Zhouli by Liu Xin to differentiate it from a chapter in the Classic of History which was also known as Zhouguan.Though tradition ascribed the text of the...
) this place is the center of the Earth.
Yuan Dynasty
The great observatory was built in 1276 in the early Yuan DynastyYuan Dynasty
The Yuan Dynasty , or Great Yuan Empire was a ruling dynasty founded by the Mongol leader Kublai Khan, who ruled most of present-day China, all of modern Mongolia and its surrounding areas, lasting officially from 1271 to 1368. It is considered both as a division of the Mongol Empire and as an...
on the order of Kublai Khan
Kublai Khan
Kublai Khan , born Kublai and also known by the temple name Shizu , was the fifth Great Khan of the Mongol Empire from 1260 to 1294 and the founder of the Yuan Dynasty in China...
and was used by Guo Shoujing
Guo Shoujing
Guo Shoujing , courtesy name Ruosi , was a Chinese astronomer, engineer, and mathematician born in Xingtai, Hebei who lived during the Yuan Dynasty...
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. The length of the tropical year
Tropical year
A tropical year , for general purposes, is the length of 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...
was determined to 365 d 5 h 49 m 20 s, a value in accord with the value of the Gregorian Calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...
, but obtained 300 years earlier.
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 and oldest surviving observatory in China.