And here’s the ongoing “classic” Straight Dope discussion in which Cecil Adams argues that the Great Wall, among many, many other manmade structures, is visible from space:
Without getting into what “space” means (15 miles high, 100? from the moon?), what do we make of this revelation? And Mr. Adams, if you’re out there, what can we really see from space if we can’t count on the Great Wall? The Fresh Kills landfill on Staten Island? The Interstate Highway System? Help!
The problem with this question is it leaves a huge amount for error. Namely “What is Space?” Where does it began. If you orbit low enought there are man made objects visable. But is that “outer space?” Depends on who you ask.
I was direly disapointed with the article by Cecil. Anyone who has actually seen the Great Wall would know that:
-Most of it is in ruin and over-run by vegetation. I had a hard time seeing it from a low-flying airplane. The pretty pictures you see are usually of a very short segment that was entirely renovated in the 1950s.
-Most of it is made out of mud. The colour of which is fairly similar to the surrounding areas.
“You can see the Great Wall,” Lu says. But it’s less visible than a lot of other objects. And you have to know where to look.
“You can see an awful lot from space,” says astronaut Ed Lu, the science officer of Expedition Seven aboard the international space station. (October 6, 2003)
Yang Liwei said HE didn’t see the wall. NOT that it couldn’t be seen. Forty years ago when it was first observed conditions would have been much better also. The past twenty years have been detrimental to the Great Wall. Milions of tourists every year and decades of neglect have taken its toll. Hundreds of miles have fallen into disarray. Much of it has been destroyed by locals, the bricks used to build other structures. It has been allowed to grow over with vegetation and decay.
That element combined with the fact that earth’s atmosphere has been polluted significantly in the last thirty years gives reason enough for me to question the validity of this OP.
If Ed Lu is to be taken seriously, then perhaps the media has made another blunder. The Chinese government is supposedly going to rewrite/update their textbooks because of this. Will they change them again when this error is discovered?
As the Great Wall is an average of only 10-12 feet wide, OF COURSE it would not be visible from any great height (let alone space, which is usually defined as beginning where the detectable atmosphere ends - 40-50 miles up)
If it were visible, then the Interstate roadway systems would also be visible, being about the same width - and usually in multiple pairs.
Of course, certain conceptual object are visible from a great height (the continents, Long Island, Cuba, Iceland) but apparently no man-made object is visible from orbit with the unaided human eye - unless we count artificial lighting visible at night from the dark side of the planet. And nuclear explosions!
If you click the “lots of manmade structures are visible from Earth” link in t-keela’s article, you go to a page that talks almost exclusively about the use of binoculars or long camera lenses.
and Lu says:
So it’s not clear to me what Lu is seeing unaided and what requires a lens in front of his eyes even on the first page.
Actually what he said was that it (the Great Wall) could be seen with the naked eye, but especially with binoculars. I agree that his wording could be taken that way. He was responding a specific question (can the Wall be seen from the Space Station and commenting on how the press had taken Liwei’s observation out of context. The Chinese government was concerned about the myth being taught in school.
How 'bout a few cites? http://geography.about.com/gi/dynamic/offsite.htm?site=http://lheawww.gsfc.nasa.gov/users/jacob/qa_earth.html
See Great Wall from the Moon?
Can you see the Great Wall of China from the Moon?
The Great Wall can barely be seen from the Shuttle, so it would not be possible to see it from the Moon with the naked eye.
Beth Jacob
http://www.vibrationdata.com/space/greatwall.htm
Space Shuttle Astronaut Jay Apt reported the following: …“the Great Wall is almost invisible from only 180 miles up!”
At 300 miles above the Earth astronaut William Pogue could see the Great Wall with the use of binoculars but not without.
So, apparently the Great Wall IS visible from space dependant upon certain conditions such as weather, altitude, and the observer’s ability. Ed Lu said He could see it. He also said “especially” when using binoculars. This does not diminish his point that he could still see the Wall even without binoculars. He has answered this question several times. NASA says the Great Wall is visible from the shuttle BUT not the moon. We’re not talking about the moon in this OP. So, I’ll take that as another confirmation. Jay Apt said he could see the Wall from space as well. Cecil Adams said the Wall was visible from space…
I guess the questionable quote by a one time astronaut has more weight than the decades of expertise and numerous sightings by far more experienced people than Yang Liwei. Who didn’t say the Great Wall was not visible from space. He said that he didn’t see it. The myth involved is that the Great Wall can be seen from the Moon. That is obviously incorrect.
Now, I think I’ll submit a bit of IMHO to this. People who say, “the Wall is only a few yards wide…etc.” You may very well be correct in the sense that the actual wall itself isn’t being seen. The Great Wall of China is in many places a division of landscapes and a barrier or windblock against nature. It has in many places caused distinct differences in the land on either side of the wall. Instead of an object 15 or 20 feet wide, the wall’s appearance including landscape distinctions and shadows even, could be greatly increased. In remote/barren regions where the wall is the only object around, no trees, rivers, mountains…etc. the wall would appear as a small line a bit off colored from the rest. I saw a photo (not from space) but it was an aerial shot. Pretty cool in fact, there was a storm blowing across the wall (from the west IIRC) and on East side of the wall it was calm for what appeared at least three or four times the width of the wall itself.
I know this observation won’t stand as evidence. It might however be part of how/why the Great Wall can be seen sometimes from space.
Hopefully I haven’t been too redundant on some points in this response. I noticed that I repeated myself here and there, but I’m gonna post it as is. It’s late, g-nite.
Also because the Wall is raised above its surroundings, it could cast a shadow much wider than itself, near sunrise or sunset. It’s perhaps debateable whether seeing the Wall’s shadow counts as seeing the Wall, but certainly you’re seeing evidence of it.
But you have to take into account that a lot of the Great Wall is sitting atop mountainous ridges that are often fairly steep and much, much higher than the wall. You’d be much more likely to see the mountains’ shadows than the wall’s.
