Gaocheng Observatory

The Gaocheng Observatory

The Gaocheng Observatory is a historic solar and observatory in the central Chinese province of Henan . It is called after its location in the village of Gaocheng ( Chinese  告成 ), 8 km east of the city of Dengfeng ( 登封 ) in the east of today 's People's Republic of China . The observation station goes back to the time of the Mongol rule and is the oldest preserved observatory in China.

It is also known as the Old Dengfeng Observatory ( 登封 古 观象台 , Dēngfēng gǔ guānxiàngtái ). In a temple district dedicated to the memory of Duke Zhou of the Western Zhou dynasty , the Mongol prince Kublai Khan had the first of 27 large observatories built in the early Yuan dynasty in 1276 for the creation of the new Shoushi calendar . At the position of this historical observatory, Zhou Gong already had in the 11th century BC. A large gnomon (shadow staff) erected. A smaller predecessor from the Tang Dynasty to the creation of the Da-Yan calendar can also be seen.

Since 2010, the observatory has been recognized as a UNESCO World Heritage Site as part of Dengfeng's monuments .

Western Zhou Dynasty

According to Chinese tradition, Duke Zhou Gong Dan, who lived around 1100 BC. BC, a gnomon was set up here to observe the course of the sun. His interest in mathematics and astronomy / astrology is documented in one of the oldest Chinese collections of mathematical tasks " Zhoubi suanjing " (Gnomon of the Zhou), which he presents to the official Shang Gao. This also includes the calculation of the position of the sun from the shadow of the gnomon, a theory of the horizontal sundial .

Tang Dynasty

In the Tang Dynasty, the influence of the earth's elliptical orbit should be included in the calendar calculation. To determine the equation of time necessary for this , the astronomer Yi Xing (一行) (683 - 727) had 20 solar observatories with standardized “8- Chi ” -nomons (approx. 1.98 m) built all over China and North Vietnam. The Da-Yan calendar of AD 729 is based on the dates.

Following a suggestion by the astronomer Liu Zhuo from the year 604, 10 of the gnomons were distributed approximately along the meridian 114 ° east of Greenwich from Central Asia to Huế in Vietnam , in order to determine the size and any deviation of the earth from the spherical shape. One of these gnomons was in Gaocheng. Due to the difficulty of recognizing the umbra, the meridian degree was determined to be 131.29 km instead of the modern value of 111.12 km. The same idea underlies the definition of the meter .

Yuan Dynasty

Like almost all new dynasties in China that came to power, the Great Khan Kublai Khan , the founder of the Yuan dynasty , intended to have an improved calendar drawn up. To this end, he had several solar observatories built. The first was built by the astronomers Guo Shoujing (1231-1316) and Wang Xun (1235-1281) in Gaocheng in 1276 to follow the course of the sun and stars. It consists of 2 parts, a tower with 2 cabins and the "Shigui" (called "yardstick for measuring the sky"). The tower platform has a height of 9.46 m, together with the two measuring huts 12.62 m. The unconventional gnomon consists of a pole at "40 Chi" (approx. 10 m) height, which is stretched between the two huts.
The length of its shadow is read off the "Shigui" at lunchtime . It is aligned along the meridian and consists of 36 stone slabs with two parallel water channels that serve as a spirit level. Its dimensions are 31.19 m long and 0.53 m wide. To avoid reading errors due to the difficulty of recognizing the transition between umbra and penumbra , which hindered the measurements of the Tang time, a pinhole is placed on the stone slabs. The length of the shadow at the winter solstice is approximately 31 m. This distance can be determined with an uncertainty of only 2 mm.

These high-precision measurements were used for the Shoushi calendar of 1281 , which was valid for 364 years. The tropical year was determined to be 365 days, 5 hours 49 minutes and 20 seconds. This corresponds almost exactly to the year length of the Gregorian calendar of 1583. In
1787, Pierre-Simon Laplace used these measurements to check his calculations of the secular changes in the ecliptic skewness and the eccentricity of the earth's orbit.

Kublai Chan's brother, Ilchan Hülegü , had the Rasad-e-Chan observatory built in northern Iran for the astronomer Nasīr ad-Dīn at-Tūsī as early as 1259 , where Chinese astronomers also worked.

Web links

• Early Chinese Astronomy
• Ancient Observatories
• Article on the Shoushi calendar from the National University of Singapore (PDF; 509 kB)
• World Heritage

Individual evidence

1. ↑ UNESCO World Heritage Center: Historic Monuments of Dengfeng in “The Center of Heaven and Earth”. Retrieved August 19, 2017 . 

Coordinates: 34 ° 24 ′ 8.7 "  N , 113 ° 8 ′ 26.6"  E