When was the earliest observatory built?

As early as 2600 BC, the ancient Egyptians established the earliest observatory in the world to better observe Sirius. Similarly, by 2000 BC, the Babylonians set up an observatory for the same reason. China also began to build an observatory about 2,500 years ago, but at that time it was called Taiqing, Mourning and Observatory. In many ancient countries, the observatory is not only a place for observing astronomy, but also a place for divination and sacrifice, so the observatory is generally one of the most important places for rulers.

With the constant changes of the times, the architecture of the Observatory is also constantly changing and improving. The famous observatory in history was established by Danish astronomer Tycho in Copenhagen on 1576, equipped with the most advanced astronomical instruments at that time. The earliest astronomical observatory in China was built in the Yuan Dynasty, and now it is located in Gaocheng Town, southeast of Dengfeng County13km. Guo Shoujing, a famous astronomer in Yuan Dynasty, observed celestial bodies here and calculated an astronomical result: the tropic year is 365 days, 5 hours, 49 minutes and 20 seconds, which is only 26 seconds away from the modern determination of tropic year. The chronicle he compiled was born 300 years earlier than the current Gregorian calendar, which shows that the scientific research level of ancient astronomical calendars in China has been quite superb.