Can the Great Wall be Seen From the Space

Listed into the World Culture Heritage on December 1987, the Great Wall also becomes one of the Seven Wonders in the world. For a long time, it was believed that the Great Wall could be seen from the space since it is the longest manmade project on the earth. But is it true? Can the Great Wall really be seen from the space? Would you please continue your read..

Astronaut’s Answer

With a total length of 8,851.8 kilometers, the Great Wall of China starts from Jiayuguan Pass within Gansu Province in the west and ends at Shanhaiguan Pass within Hebei Province in the east. Without any doubt, it is really majestic. Does this mean the Great Wall can be seen from the space? On October 15, 2003, China’s first astronaut Yang Liwei arrived at the outer space by the spacecraft named Shenzhou V. How about his answer upon come back from the outer space? It is ‘No’ in fact. The theory of visible was shaken.

In addition, Leroy Chiao from NASA (National Aeronautics and Space Administration) ISS (the International Space Station) once took pictures of the Great Wall twice. The first time he used a 180mm lens and a digital camera which was thought to be the first confirmed picture of the Great Wall. And the second time he took a 400 lens one. Did he see the Great Wall? Can the Great Wall be seen from his pictures? Answer to the former question is a negative one, and he was not sure about the later one.

Besides the above two, there are also some other astronauts said the Great Wall of China is invisible from the space. In 1969, one American aviator named Neil Alden Armstrong set foot on the moon firstly. And there is no manmade object on the earth he could see from the moon. What’s more, the other two American astronauts—Buzz Aldrin, and Jeffery Alan Hoffman and also the first American space tourist-Dennis Anthony Tito all offered a result once which was the Great Wall could not be seen from the space.

Proofs of Invisibility

Suppose the width of the Great Wall is 10 meters, and the space is 400 kilometers away from the earth which is based on the International Space Station. Then seeing the Great Wall from space, the width’s angle is only five arc-second (a kind of angular unit). What does it mean? It means to see a 0.25 mm string from 10 meters away. Can you find it? The answer must be ‘No’. In fact, people’s naked eyes can pick out about 36 arc-second’s angle. The five only one obviously is beyond people’s discrimination. That is to say, under normal condition, the Great Wall is invisible from the space.

There is a version - why we can see the thousands of stars from more than four light-away? Their angle is further. Why can we see them? The reason is they can shine in the dark sky and these lights would be transmitted. We will see if they are light enough. Hence, in the same way, if we add some lights to the Great Wall, it will be seen. Is this true? The answer is still unknown since there is no scientific experiment carried out. So, till now, we can say that the Great Wall of China can not be seen from the space.

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