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Immaculate Misconceptions: I spy with my naked eye, not The Great Wall of China

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Another wonderful addition to our Immaculate Misconceptions feature! Isabelle Rogerson obliterates the myth that you can see ‘The Great Wall of China’ from outer space, with the naked eye.


You’re sitting comfortably. Having paid $250,000 for your seat on the Virgin Galactic, you were expecting this flight to be something quite special, and zero gravity did not disappoint. As you look out your window, you see that you are orbiting over China. You crane your neck, trying to make out the Great Wall, famously visible from Space … But can you see it?

136063main_bm4_high
nasa.gov

The myth that the Great Wall of China is visible from space has been one of the most persistent space-based legends, like an ugly barnacle clinging to the front of a shiny new boat. The myth dates back to the early 20th century: in 1932, Ripley’s
Believe It or Not! claimed that the wall was visible to the human eye from the moon. This would be impressive considering that from the moon, Earth looks more like a blue and white marble, and the smallest things you might be able to make out are large lakes. But, this didn’t stop Armstrong from being questioned about the Great Wall when he returned from the moon in 1969. When Yang Liwei, the first Chinese
astronaut, returned from orbit in 2003 and revealed that he had not been able to make out the wall, there was public uproar in China, and the Chinese Ministry of
Education had to revise their school textbooks. Some argued that shuttles pass too quickly to get a proper look. Let’s put this theory to the test. Here is the first photo of the Great Wall taken from low earth orbit in 2004:

Screen Shot 2015-05-26 at 18.55.31

Finding the wall in this photo is like playing Satan’s version of Where’s Wally?. The problem is that the wall is made from materials that are a similar colour to the elements around it, and it follows the natural geography of the
landscape, so it is hard to distinguish from rivers or mountains. In fact, the easiest man-made structures to make out from space are ones that contrast with nature’s curving lines, such as straight roads or bridges.

Amazingly someone did manage to find the wall, and has pointed it out to us mere mortals:

Screen Shot 2015-05-26 at 18.55.40
universetoday.com

Well now we’ve shown you it seems blindingly obvious … doesn’t it? We don’t think so either. To rub salt in the wound, this photograph was taken with a 180mm zoom lens. So unless you’re actually a cyborg with artificially
enhanced eyeballs, you probably won’t be able to make out the wall with your “naked eye” at this height.

Having said all this, there are specific conditions under which the wall might be visible. If the sun is low on the
horizon, the wall casts a long shadow that makes it easier to spot. If you use radar imagery, the wall stands out nicely against the background (the orange line in the photo below):

Screen Shot 2015-05-26 at 18.55.47
nasa.gov

But again, this goes somewhat against the legend of being able to see the wall “with the naked eye”.

So what does this mean for our lucky Virgin Galactic passenger? Well, Branson’s SpaceShipTwo is planned to fly at a height of 110km, which is 50km lower than the ‘low earth orbit’ that the astronauts were flying at. So you might be able to catch the Great Wall, if the sun is in exactly the right position, and you happen to be carrying a camera with a zoom lens and incorporated radar. But, this is a bit like telling someone that they look beautiful … at 100 feet … in a dark cave…from a blind person. On top of all that, the wall is only visible if the air above China is clear. With all the gases China is currently releasing into the atmosphere, our advice would be: don’t get your hopes up.

Isabelle Rogerson

Check out more of Isabelle’s work, as well as numerous other horrendous scientific & technological misconceptions here!

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