Take the Beijing Subway and go through various transfers in the road network to arrive at Jianguomen Station. As soon as you come out of Exit C of Jianguomen Subway Station, you can see a high platform in Jiebier.

The poet Li Bai is the most intimate drinker. Even if no one is with him, he still wants to "raise his glass to invite the bright moon, and make three people face each other". Li Bai said at the end of this batch of "Four Poems of Drinking Alone under the Moon", "You must drink fine wine and ride the moon to climb the high platform". Although it is true that the high platform in front of us has been climbed by people on the moon, Li Bai is not among them. Li Bai was a native of the Tang Dynasty, and this high platform was built in the seventh year of Zhengtong in Zhu Qizhen, Emperor Yingzong of the Ming Dynasty, that is, it was built in 680 years after Li Bai's death.

What is Li Bai doing on the high platform? Su Dongpo in the Song Dynasty said that it was "the blue sky, the evening clouds. The high platform on the city is really transcendent." That is to say, Li Bai went to the high platform to find detachment, to play a drunken fist, and to write two drunken poems. Those other people on the high platform are not to drink, but to engage in another very romantic behavior, which is to look at the stars, "to see the meteor shower fall on this earth."

Before this high platform in the Ming Dynasty, someone in the Yuan Dynasty rammed a mound here, and then went up to watch the stars at night. Among these people is a well-known one named Guo Shoujing, who is a regular astronomer. During the Eastern Han Dynasty more than a thousand years before Guo Shoujing, Zhang Heng was studying astronomy and geography. Before Zhang Heng, fortunetellers usually knew how to look at the stars. During the Five Hu and Sixteen Kingdoms period after the Eastern Han Dynasty, watching the stars has become a profession, called astrologer. Last time I saw astrologers on the eaves in an ancient Zhangbi castle of that period in Shanxi.

You see, this astrologer didn't have a high platform to climb up at that time, so he had to build a ladder on the gable wall outside his house to climb up to see the stars. The astrologer of Zhangbi Ancient Castle has left the profession of a fortuneteller. He is neither counting human life nor fortune of the country. He wanted to see clearly the position of the stars in the sky, and then guide the building layout in the village.

In the Zhengtong period of the Ming Dynasty, Zhu Qizhen, Emperor Yingzong of the Ming Dynasty ordered people to build the high platform we see now for experts who can see the stars. He asked experts to go up to the high platform to calculate the fate of people and the fate of the country, of course it was all his own; he could also do some scientific research by the way. At this time, society is already very advanced, and divination is already a fringe theory, and it is difficult to be considered elegant. Zhu Qizhen asked the experts to give Gaotai an academic official name. In the Yuan Dynasty before this, the rammed earth mound that Guo Shoujing climbed was called "Sitiantai". Astronomers in the Ming Dynasty were very ashamed of the name "Sitiantai". How can ordinary people be able to control the sky? But anyone who can drive is very good. They believe that the sky cannot be controlled but can only be observed, so they named this high platform "observation platform", which is a high platform for observing the sky. The engraved stone of this "observatory" is still above the arch of the gate. Because of the age, the red color on the words has faded.

The earliest regular celestial observer in China may be Zhou Wen Wang Jichang. In the "Book of Changes" he edited and performed, there is "the image of the sky, see good and bad, and the sage looks like it". This observatory in Beijing was used until 1927 when the Nanjing Zijinshan Observatory was established, and was later identified as the second batch of national key cultural relics protection units in 1982.

On the day when I came to the stage, the sky was high and the clouds were light, and there were few guests. There is no old gatekeeper at the door everywhere, and there is no house with a "ticket office" plaque. The doors of the stage are fully open, and it is said that it has been like this since 9:00 in the morning, and it is free to visit.

When I walked to the door and was about to step onto the stage, I saw a big man throwing himself on the steps as if he was digging something.

Although I thought that someone was poaching the wall in broad daylight, I still asked him if he was an Internet celebrity touching Captain Jin? He said no, he was here to shoot Chaoyun Feidu in the sky. He complained to me that in the middle of the filming just now, because he didn’t protect the equipment like this, an old man came over and pressed the button on his machine, and all the previous pictures were taken for nothing, and the clouds in the sky flew away . Don't tell me, some old men really have obsessive-compulsive disorder, and they can't help but press the button when they see it. Therefore, the soldiers of the missile force are all young people, otherwise, if any old soldier comes over and presses any missile launch button, the missile will fly out casually? Fly to any place, and the US troops there will suffer?

When I climbed onto the high platform, I didn't see the old man, but a locked gatehouse.

There are seven, seven, eight or eight observation instruments.

When the Eight-Power Allied Forces invaded Beijing in 1900, these instruments were robbed by the French and German armies. The French army hid several of them in the embassy in China, and it took two years to return them. The German army shipped several other pieces back to China and put them in the New Palace behind the Sanssouci Palace in Potsdam to show off. After the defeat in World War I, they were returned to China in 1921.

Look at the observation instrument on the stage, this is called "Jiheng Fuchen Instrument".

Look at its beauty in cast copper.

This Jiheng Fuchen instrument is also called the equatorial theodolite, which was cast by imperial order in the 19th year of Qianlong (1754) in the Qing Dynasty. Jiheng comes from "Shangshu" "Xuanji Yuheng, Qiqizheng". This celestial instrument is a little more complicated than the general equatorial theodolite, with some more components, mainly to measure the position of celestial bodies (equatorial longitude and latitude) and solar time. There were no atomic clocks in ancient times, and accurate timekeeping relied on astronomical observations. In fact, the time of astronomical observations is now the standard, and atomic clocks must also be calibrated with astronomical time.

This is called the zodiac theodolite.

In the twelfth year of Kangxi (1673), the Belgian missionary Nan Huairen was ordered to build it to measure the ecliptic latitude and longitude of celestial bodies.

The following astronomical instrument was also built by Nan Huairen.

This celestial instrument is used to demonstrate the position of celestial bodies on the ecliptic, equator, and when viewed from the ground. Nan Huairen built several meteorological instruments together in those years, as did the Jixian instrument below.

A sextant, also called a sextant, is used to measure the angle between two stars. Although we don't know its mystery, we often see people holding such a sextant in their hands while sailing on the sea in pictures. In addition to having a compass to guide the course, ancient navigation also relied on astronomical observation for positioning.

This one below is the horizon.

This horizon instrument was also built by Nan Huairen, and it was used to measure the azimuth of celestial bodies. At that time, Nan Huairen made a total of six instruments, including the quadrant instrument below.

A quadrant is used to measure the altitude angle of a celestial body.

Below is the horizon theodolite.

This horizontal theodolite was also built in the Kangxi period, in the fifty-fourth year of Kangxi (1715). You can see that there is no copper dragon on it, but a Western style. This one was not built by Nan Huairen, but by a German missionary named Gillian. Horizon theodolite integrates the functions of quadrant and horizon theodolite.

On the high platform, most of the observation instruments are made by foreigners; what about domestic instruments? I walked down the high platform with questions, and saw ancient Chinese observatories in the yard. Check out this one below.

Linglongyi, which was made by Guo Shoujing's students in the Yuan Dynasty according to the teacher's drawings. The metal spherical surface is a layer of eggshell, with many small eyes on it. When people drill into the eggshell and look around, they can see the sky full of stars. Because those small eyes are chiseled according to the regulations, the starry sky seen inside is very realistic. There is a planetarium opposite the Beijing Zoo, which has a projection hall. Modern astronomers use magic lanterns to project the starry sky on the dome of the projection hall, which is more realistic than the starry sky seen in this exquisite instrument.

There is also an armillary sphere in the yard.

The earliest armillary sphere in ancient China was built by Luo Xiahong, an astronomer in the period of Emperor Wu of the Western Han Dynasty. This is also the earliest armillary sphere in the world. Armillary spheres can be used to measure the equatorial coordinates of celestial bodies. Since Luo Xiahong invented the armillary sphere, later generations have made many improvements. The armillary sphere here is from the Ming Dynasty, which has added many functions, and can also measure the ecliptic coordinates and horizon coordinates of celestial bodies. Sixty years after Luoxiahong's armillary sphere, similar observatory instruments appeared in Greece.

There is also a Jianyi in the yard.

Jianyi is a simplified armillary sphere, designed by Guo Shoujing in Yuan Dynasty. Three hundred years after Guo Shoujing simplified the armillary sphere, a simplified version of the Greek armillary sphere appeared in the West, made by a Dane.

The following one I know is the shadow measurement.

This is called Guibiao, the standing copper pillar is "Gui"; the lying copper plate is "Biao". At twelve o'clock in the noon, you can appreciate the scale of the length of the shadow cast by Kei on the watch, and you can know which season of the four seasons it is.

Guibiao can tell the season, and there is also an instrument called "sundial" for watching the time. The pronunciation of sundial and Gui is similar.

Since there is a sundial for timekeeping during the day, there should be a moon dial for timekeeping at night, right? Don't tell me, there really are, but not here. The Moondial is visible only through the Moon Gate below.

Well, here it is.

There is actually a star dial as the adjutant of the moon dial. Because the timekeeping of the moon dial is not very accurate, an adjutant is needed as an assistant. China had the word "star dial" in the Southern and Northern Dynasties, which represented the meaning of time; but it was not until the Qing Dynasty that the instruments of moon dial and star dial appeared. How do you know the time at night without moon and star dials? Then it depends on listening to the old man knocking on the clapper.

There were many astronomers in ancient China, the one we are most familiar with is Zhang Heng in the Eastern Han Dynasty.

Zhang Heng promoted the armillary sphere theory founded by the predecessors, and also upgraded the technology of the armillary sphere invented by the predecessors, and installed a hydraulic transmission system. This new armillary sphere is called "Leaky Turning Armillary Sphere", which can act by itself and demonstrate the movement of celestial bodies in chronological order, which is very magical.

Of course, the invention of Zhang Heng that we are most familiar with is the "seismograph".

When the observatory was built during the orthodox years, it was necessary to build some small rooms so that the astronomical officer could rest after going on the stage sooner or later. That house is still there, and it is still the one from the Ming Dynasty. Because this observatory has been in use, the house has been constantly repaired and is in good condition.

The main hall is called "Ziwei Hall". In ancient Chinese astronomy, the area around the Polaris was called Ziwei Yuan, and the "Ziwei" on the plaque here should have the meaning of observing the sky. In ancient divination, there is also the saying of "Ziwei Doushu", which is a technique for calculating people's luck based on the horoscope of birth, so this phenomenon also means guessing the fate of the royal family and the fate of the country. Haha, look, I really hit the spot. These sky watchers really have the function of calculating the luck of the royal family.

Although this is an institution for the emperor, the specifications of this house are not high. From the outside, it looks like a five-room, five-gray-tile hard top. This kind of roof can be found in both east and west urban areas, even in Xuanwu and Chongwen. What shows the noble status here is the huge main ridge and the brick-carved owl kisses at both ends. When entering the house, it is a private house with a beam-lifting roof.

There is an exhibition of "China's Starry Sky" in this hall.

There are also some precision machines inside.

The one above is a taxi, and the fare is not paid by the mileage, but by how many miles you have run. Every time the car traveled a mile, the wooden man on the car would beat the drum. "Eight thousand miles of cloud and moon", that is, Caiyun rides this car to chase the moon, and the wooden man on the car beats the drum eight thousand times. Why not hire a living man to sit in a car and beat the drums? Who among the living can do this job? Who can bear the endless beating of eight thousand drums? This taxi was also invented by the great Zhang Heng, earlier than Zhuge Liang's wooden cow and horse.

I have been passing by Jianguomen for so many years, but I have always missed this ancient observatory. Today's trip finally saw the back of its neck and the bronzes on its back. Of course, these bronzes are all contemporary replicas.