Ancient emperors in China all claimed to be the sons of heaven, so they built a nine-story heaven, "facing south, the temple is connected with the sky", trying to construct the illusion that the monarch's power was "ordered by heaven". However, Kui Zhongyu, a researcher at the Chinese Academy of Surveying and Mapping, found that from the Yuan Dynasty to the demise of the Qing Dynasty, the Forbidden City in Beijing where 33 emperors worked and lived was not the direction of "due south and due north". ?

Kun Zhongyu, an expert in aerial remote sensing, likes to study large-scale Beijing satellite images and Beijing aerial images in his spare time. One day, when his eyes were "northward" along the central axis of Beijing on the image map, his head unconsciously tilted to the left, which surprised him-the central axis should be "due south and due north". Is there anything wrong with the aerial image? Verified by geographical coordinates, Zhong Yu Kui found that Beijing's central axis deviated from the meridian by more than ten points. ?

The central axis is the central symbol of Beijing architecture in Yuan and Ming Dynasties. It starts from Yongdingmen in the south and reaches the Bell and Drum Tower in the north, with a total length of 7.7 kilometers, which is the longest existing urban central axis in the world. Kui Zhongyu said that on the accurate topographic map, the central axis of Beijing presents a kind of "deviation": it starts to deviate from the meridian counterclockwise when extending from the southern starting point to the north, and the terminal position, that is, the actual distance after conversion, has left the meridian about 300 meters. ?

In most people's common sense, the central axis of Beijing coincides with the meridian, showing the direction of "due south and due north". Nowadays, in the measurement of Kui Zhongyu, the central axis is "crooked". Wei Xiao also wondered, did surveying and mapping experts and map makers make group mistakes? ?

Experts involved in map drawing told Kun Zhongyu that when they drew the map strictly according to the field measurement, they also found that the central axis was crooked. They are also very confused. During this period, someone proposed to "straighten" the central axis on the map. ?

In the process of searching, Zhong-yu Kui learned that in the early days of the People's Republic of China, surveying experts in Beijing discovered this "deviation" in order to plan municipal construction. It is said that they have reflected this problem to the relevant institutions, but historical facts cannot be changed.

In order to find out the direction of Beijing's central axis in reality, Zhong-yu Kui made an "instant" sundial experiment at the end of 2004. The experimental results are consistent with his previous findings on the map?

The existing central axis of Beijing is the central axis of the Yuan Dynasty. When Genghis Khan conquered Jinzhongdu (now Beijing), it was completely destroyed. Since then, Kublai Khan built Yuan Dadu on the original site; In order to guard against Mongols, the Ming Dynasty built Deshengmen on the basis of the Yuan Dynasty. The east and west city walls followed the Tucheng of the Yuan Dynasty, and the direction of the central axis remained unchanged. It has been more than 730 years since Ming Dynasty continued to use Ming City. ?

So, why is the central axis skewed? Some historians believe that Liu, a minister of the Han nationality, and his disciple Guo Shoujing were the supervisors of Beijing's construction at that time because of the national oppression policy of the Yuan Dynasty. In order to resist the rule of the Yuan Dynasty, they deliberately deviated the central axis from the meridian. Some scholars believe that it may be that the builder adopted the magnetic needle positioning method, which caused technical mistakes. ?

Kun Zhongyu believes that the evidence of the above two viewpoints is insufficient. After surveying and mapping maps and field trips. Kui Zhongyu was surprised to find that the central axis of Beijing continued to extend northward, and the extension line just passed through Gukaiping, which is more than 270 kilometers away from Beijing, that is, Zhaonaiman Sumer in Xilin Gol League, Inner Mongolia Autonomous Region (this is the site of the Yuanshangdu site).

That's where Kublai Khan moved to Beijing. Kublai Khan of Yuan Shizu implemented the "Two-Beijing Tour System" at that time: in Beijing in winter and in Du Yuan in summer. Therefore, Kui Zhongyu believed that the fact that the central axis deviated was intentional by Kublai Khan, the founding emperor of the Yuan Dynasty. ?

From Yuan Dynasty to Qing Dynasty, there were 33 feudal emperors with Beijing as their capital in history. These 33 so-called "the only thrill", except perhaps Kublai Khan himself, probably didn't know that their dragon chair was "crooked".

The central axis of the Forbidden City is not north-south, but northwest, which was left by the Yuan Dynasty.

The palaces of the Ming and Qing Dynasties were built on the basis of the palaces of the Yuan Dynasty, so this provision of the Yuan Dynasty remained basically unchanged.

What was the reason for setting the central axis in Yuan Dynasty? So far, it has not been confirmed. Some historians believe that due to the national oppression policy of the Yuan Dynasty, Liu Hanchen Zhong Bing and his disciple Guo Shoujing were the supervisors of Beijing construction at that time. In order to resist the rule of the Yuan Dynasty, they deliberately deviated the central axis from the meridian. Some scholars believe that it may be that the builder adopted the magnetic needle positioning method, which caused technical mistakes. ?

"China's first person in the basic theory of remote sensing" Kui Zhongyu thinks that the evidence of the above two viewpoints is insufficient. After surveying and mapping maps and field trips. Kui Zhongyu was surprised to find that the central axis of Beijing continued to extend northward, and the extension line just passed through Gukaiping, which is more than 270 kilometers away from Beijing, that is, Zhaonaiman Sumer in Xilin Gol League, Inner Mongolia Autonomous Region (this is the site of the Yuanshangdu site).

That's where Kublai Khan moved to Beijing. Kublai Khan of Yuan Shizu implemented the "Two-Beijing Tour System" at that time: in Beijing in winter and in Du Yuan in summer.

Therefore, Kui Zhongyu believed that the fact that the central axis deviated was intentional by Kublai Khan, the founding emperor of the Yuan Dynasty. Another inference is that the straight line pointing to this declination angle may be the direction of Genghis Khan's tomb.