Gaocheng Astronomical Observatory
The Gaocheng Observatory is a historic solar observatory and in the central Chinese province of Henan. It is named after its location in the village 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 surviving observatory in China.
It is also known as Observatory of Dengfeng and Old Observatory of Dengfeng (登封 古 观象台, Dengfeng gu guanxiangtai ). In the memory of Duke Zhou consecrated by the Western Zhou Dynasty temple district was the Mongol ruler Kublai Khan in 1276 the first of 27 Großobservatorien for the creation of the new Shoushi calendar built in the early Yuan Dynasty. At the position of this historic observatory already Zhou Gong v. in the 11th century BC a large gnomon (shadow bar ) had built. A smaller predecessor of the Tang Dynasty to the creation of the Da Yan calendar can also be seen. In 2004, China made the request to UNESCO to include the observatory in the list of world cultural heritage.
Western Zhou Dynasty
According to Chinese tradition already had Duke Zhou Gong Dan, who lived around 1100 BC, set up a gnomon to observe the passage of the sun here. 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 said officials Shang Gao is in it. Including the calculation of the sun from the shadow of the gnomon, ie a theory of the horizontal sundial.
Tang Dynasty
In the Tang Dynasty, the influence of the elliptical orbit of the earth should be included in the calendar calculation. To determine the time required for this equation was the astronomer Yi Xing (一行) ( 683-727 ) 20 solar observatories with standardized "8- Chi " gnomons (approx. 1.98 m) build distributed all over China and North Vietnam. On the data of the Da Yan calendar based on 729 AD
Following a suggestion of the astronomer Liu Zhuo from the year 604, 10 of the gnomons approximately along the meridian 114 ° east of Greenwich from Central Asia were to spread to Hue in Vietnam to determine size and any deviation from the spherical shape of the earth. One of these was in gnomons Gaocheng. Due to the difficulty of recognizing the umbra, certain to the degree to Meridian 131.29 kilometers instead of the modern value of 111.12 kilometers. The same idea underlies the definition of the meter.
Yuan Dynasty
Like almost all newly coming to power dynasties in China also intended the Great Khan Kublai Khan, the founder of the Yuan Dynasty, to let develop an improved calendar. To this end, he had several solar observatories built. The first was built by the astronomer Guo Shoujing (1231-1316) and Wang Xun (1235-1281) in 1276 in Gaocheng to track the movement of the sun and stars. It consists of 2 parts, a tower with 2 cabins and the " Shigui " ( " scale for measuring of Heaven" mentioned ). The tower platform has a height of 9.46 m, together with the two huts measuring 12.62 m. The unconventional gnomon consists of a bar in " 40 Chi " (approx. 10 m) high, which is stretched between the two cabins. The length of her shadow is read at lunch time on the " Shigui ". It is oriented along the meridian and consists of 36 stone plates with two parallel gullies, which are used as a spirit level. Its dimensions are 31.19 m long and 0.53 m wide. In order to avoid reading errors due to the difficulty to detect the transition between core and penumbra, the disabled, the measurements of the Tang dynasty, a pinhole is placiert on the flagstones. The length of the shadow at the winter solstice is about 31 m. This distance can be determined with an uncertainty of only 2 mm.
This high-precision measurements were used for the Shoushi calendar of 1281, which remained 364 years valid. The tropical year was determined to be 365 days 5 hours 49 minutes and 20 seconds. This corresponds to the length of the year in the Gregorian calendar of 1583rd 1787 Laplace related these measurements to check his calculations of the secular changes in the obliquity and eccentricity of Earth's orbit.
The brother of Kublai Khan, the Ilkhan Hulagu, had already in 1259 erected the observatory Rasad -e- Khan in Northern Iran for the astronomer Nasir al- Din al - Tusi, the Chinese astronomers had well.