What can be seen on Earth from space has always been a topic of conversation. In the past, many people believed that the Great Wall could be seen from the moon. In fact, this statement did not come from the mouths of the Chinese, but the American historical geographer and popular writer Hendrick William Van Long in his book “The Earth’s As soon as the book was published in 1932, it caused a sensation all over the world, was translated into 14 languages, and was regarded as one of the best popular science books at the time. The book speculates: “The Great Wall of China is the only building on the moon that astronauts can see.” After the reform and opening up, Fang Long’s works were successively introduced to our country, and the saying “the Great Wall can be seen from the moon” It also spread. When he wrote “Story of the Earth”, human beings had not yet entered space, let alone landed on the moon, but everyone felt that the Great Wall was so majestic and long, if it could be seen from the moon, it would be quite credible Yes, take a step back, even if you can’t see it from the moon, you can always see it from space. So this saying has been passed down.
In the past, all those who entered space were foreigners, and it was not easy to verify this matter. Until my country’s first manned spaceflight was successful in 2003, Yang Liwei, the first person in my country to enter space, finally gave everyone an accurate answer: from space The Great Wall cannot be seen. In fact, this is easy to understand, because although the Great Wall is very long, its average width is only about 10 meters. Looking at the Great Wall in space is like looking at a long hair from a few kilometers away. Even if the hair is a few meters long, it is still invisible. of.
Which landscapes have crossed the “space threshold”?
So, what can people see in space? It starts with what space is. We all know that the earth is surrounded by a thick atmosphere, and the atmosphere is divided into troposphere, stratosphere, mesosphere and so on. Physicist and aerospace engineer Theodore von Kármán first proposed that an altitude of 100 kilometers can be considered as the dividing line between space and atmosphere. Later, this dividing line was named “Kamen Line”, which is generally considered to be space. threshold. It is not easy for a building to be seen from space. First of all, the speed of flying in space is very fast. Usually, the speed can reach about 7,000 meters per second. It is difficult to look at a place. Secondly, space and the ground are separated by a thick atmosphere, and natural phenomena such as clouds or thunder, lightning, snow and fog will have an impact on observations. Therefore, if you want to see the buildings on the earth clearly, you can only see a clue when the weather is clear and there is no obstruction.
To be seen in space, you must first be big. For example, American astronauts claim that the Bingham Canyon gold and copper mine that can be observed in space is the largest and deepest open-pit mine in the world. This mine in Utah, USA, has a width of 4 kilometers and an area of nearly 8 square kilometers. Because it is a mine, the depth also reaches 1.2 kilometers. More than 100 years of mining has destroyed the vegetation around the mine, and almost no grass can grow within a range of tens of kilometers. Therefore, on the bare Gobi Plain, this spiral mine is particularly conspicuous. of mines can be seen from space. But judging from satellite photos, the mine looks like a deep scar on the earth. Although it can be seen from space, it is not glorious for the United States. As environmental pressure and protests intensified, the mining giant that owned the mine decided to close it down in 2013, with a series of environmental restoration plans. However, hundreds of years of damage cannot be easily repaired. Water resources, vegetation, and ecosystems have all been irreversibly damaged. According to scientists’ estimates, it may take dozens of hours to restore the ecology here. years or even longer. So, today this huge scar of the Earth can still be easily seen from space.
Although the Great Wall cannot be seen from space, another wonder of China can be seen from space, which is a modern engineering marvel – the Three Gorges Dam. The Three Gorges Dam is more than 2,000 meters long. Although it is only half the width of the Bingham Canyon gold and copper mine, and the slender dam should have been hard to see like the Great Wall, the Three Gorges Dam has a unique topographical advantage. ——There are mountains on both sides. The difference in the width and velocity of the water flow on both sides of the dam makes the area of the dam an obvious dividing point, so it is easy to judge the location of the dam through the terrain, but it is only a judgment of the location. The body is still invisible to the naked eye in space.
Also able to be seen with the help of terrain are the two famous man-made islands in Dubai, the “city of tyrants”, one of which is the well-known “Palm Jumeirah”. Named for its shape resembling a palm tree, this huge artificial island has luxury hotels, shopping malls, parks and hundreds of luxury villas on an artificial island of more than 560 hectares. After the great success of Palm Island, Dubai has built a more ambitious artificial island – World Island, which is composed of more than 300 artificial islands to form a world map. This is another man-made island visible from space. Because of its unique shape, Dubai’s artificial islands are easy to see from space. After all, the color difference between the island and the sea is still very obvious, especially the distinctive shape.
There is also a building that is highly debated over whether it can be seen from space, the famous Pyramids of Giza in Egypt. British astronaut Tim Peake claimed that the pyramids could not be seen from space at all and could only be seen through a super telephoto lens, but American astronaut Roy Joe insisted that the pyramids could be seen with the naked eye. This debate has not yet come to a conclusion, but most astronauts and scientists believe that the pyramids are invisible from space, because the pyramids are still too small from space, and the yellow pyramids are too similar in color to the surrounding desert. Difficult to distinguish.
A Unique Perspective on Fragile Planets
So, can people still see these buildings from further space station orbit? The answer is invisible. Astronaut and photographer Scott Kelly took a famous selfie on the International Space Station. In this photo, Kelly took a photo with the earth through the porthole of the space station. The area of the earth he saw was the Bahamas in the Caribbean Sea. The total land area of this archipelago consisting of 700 islands is about 14,000 square kilometers, but from space, only some small yellow dots can be seen in the middle of the sea of different depths. From the height of the space station, let alone man-made buildings, Even a city is just like a newspaper on the ground seen from a high-rise building. It is impossible to read the words on the newspaper.
After returning to the earth, Yang Liwei said in an interview that the earth is very beautiful from space, which made him feel the greatness of human beings. “Human beings are so small, but they can leave the earth and enter space, which is very remarkable.” Astronaut Zhai Zhigang was “very worried” when he first looked at the earth from space, because watching the earth like a big balloon floating in the dark space, he was worried that the earth would be “blown away” or suddenly float away . In fact, as early as 1961, when Gagarin became the first person to enter space, he said that from space, the earth is so beautiful and fragile. I hope that people all over the world can protect the earth and let this beauty exist in the universe. There has been.
If you look at the earth from a distance of 380,000 kilometers from the moon, it will be another scene. From the earth, the size of the moon is similar to that of the sun, so the ancients always thought that the sun and the moon were the same size. However, looking at the earth from the moon is nearly 14 times larger than the moon we see from the earth, and due to the principle of tidal locking, the earth does not move from the moon, neither rising nor falling, only The rotation of the earth is seen through the alternation of day and night. All the astronauts who landed on the moon expressed their great shock when they described watching the earth from the moon: a solitary planet was spinning quietly and alone in the universe. The civilization-rich planet appears so lonely and so fragile.
In 1977, the Voyager space probe began human exploration of the universe. In 1990, after Voyager 1 completed its scheduled mission, it was arranged to rush out of the influence of the solar wind to explore interstellar space. To save energy, the scientist is ready to turn off its camera. After hearing the news, the famous American astronomer Carl Sagan suggested that Voyager should look back at the earth again and take the last photo of farewell to the earth. At this time, Voyager was 6 billion kilometers away from the earth and had just left the orbit of Neptune. In this photo, the earth is just a small dot. If it is not specially marked, people can’t find the location of the earth at all, and they will only think that it is a normal noise.
For human beings, such a huge world is just an inconspicuous point of light from this point of view, and all the buildings and wonders of human beings are just smaller things on this point. And 6 billion kilometers is about the distance that light travels in a few hours. The closest star to us takes more than 4 years for light to travel. On that scale, even such a huge sun may only be a point.
”Earth is a tiny stage in the vast theater of the universe. It has been said that astronomy is a source of inferiority and a development of character. There is probably no better way to do this than this distant image of our tiny world. It can reveal how stupid human beings are.” This is how Carl Sagan felt after seeing the Voyager photo. A point in the universe is everything for human beings. Maybe only by standing on the scale of the universe, people will understand their own How small and fragile the home is. It is only at this time that people may know that they should give up fearless fighting and destruction, and try their best to protect our only earth.