We’ve all heard that the Great Wall of China is the only man made structure visible from space with the naked eye but is it? I’m a scientist, trained to be sceptically in all things but I never even questioned this ‘fact’ until I stumbled upon this report from NASA. If anyone should know the truth of this it’s NASA so what do they say about this.
First of all when we say ‘visible form space’ what do we mean exactly? Visible from low earth orbit? Visible from the moon? or further. Well lets take low earth orbit (LEO) first and work out from there. LEO is generally defined as 160 – 2,000 km but the International Space Station orbits at between 319.6 km and 346.9 km so If we can’t see it from here then then we don’t need to worry about seeing it from the moon!
Who better to find out about this myth than from one of China’s astronauts, Yang Liwei who was sent into space in the Shenzhou 5 spacecraft on October 15, 2003 and orbited at a height of 343 km. He completed fourteen orbits before landing in Inner Mongolia on October 16th. No doubt he was looking out for the Great Wall but he said on a television interview that the Earth was ‘very beautiful’ but he didn’t see the Great Wall.
Photos taken from the International Space Station by Leroy Chiao do seem to show some small sections of the Great Wall although the photographer himself says he couldn’t see the wall and is not sure if the picture really shows it.
What does NASA’s chief scientist for Earth observation say? The wall is very hard to see from space as it is made of materials which are almost the same texture and colour as the surrounding land. It is also very narrow at just ten meters wide and is very hard to pick out from its surroundings.He agreed that one photograph taken on November 24 1904 does seem to show a small section of the moon due to some conditions, such as snow on the wall and sunshine, that helped to make it more visible.
So if you can’t see the Wall from LEO it definitely won’t be visible from the moon which is around 370,000 kms away but let’s see what the first man on the moon says about it. Neil Armstrong was asked many times if he could see the Great Wall from the moon and his answer was he could not see any man made objects. The moon is a visible as a sphere from earth with continents, oceans and lakes visible but is the Great Wall visible? No says Armstrong. Other astronauts that also said they couldn’t see the Great wall from space include Buzz Aldrin and Jeffrey Hoffman. Armstrong also said he’d asked shuttle guys if any of them had seen the wall from space but no one had.
One way to see the Great Wall from space however is to use radar imagery. The wall shows up clearly in images taken from the shuttle Endeavour using Spaceborne Imaging Radar and can be seen in the image above as an a orange line. The wall can also be seen using ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) below which uses fifteen difference electromagnetic spectrum bands to produce images.
What man made structures can you see from space? The most famous are the pyramids at Giza which are clearly visible in photographs taken from the International Space Station. You can also see reservoirs and dams, large city buildings, airports and other large structures. But the Great Wall of China? No sorry that myth is clearly just that, a myth!