# Great Wall of China
**URL:** https://boards.straightdope.com/t/great-wall-of-china/78213
**Category:** Cecil's Columns/Staff Reports
**Created:** [August 26, 2001, 6:59pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213 "2001-08-26T18:59:43Z")
**Posts on this page:** 15
**Page:** 1
### Author:  [@Landiao](https://boards.straightdope.com/u/Landiao)
#### Post date: [August 26, 2001, 6:59pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/1 "2001-08-26T18:59:43Z")
About Cecil’s Classic Question about the Great Wall of China & the moon. . .
I’ve lived in China & been to the great wall nine times. At parts, it’s barely five feet high & about a foot wide, at least where it’s unreconstructed. I figured no way is this thing visible from the moon.
Then I found a book called “Japan/China” by Nikos Kazantzakis, renowned Greek author, who wrote “The Last Temptation of Christ,” “Zorba the Greek,” and “Oddysey: a Modern Sequel.” “Japan/China” is something of his travelogue from trips to Japan & China; in it, he mentions that the Great Wall is the only man-made object visible from the moon.
“Japan/China” was published for the first time in 1936. Kazantzakis himself died in 1957. Just how old is this Great-Wall-visible-from-the-moon belief, anyhow?
LRK
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### Author:  [@samclem](https://boards.straightdope.com/u/samclem)
#### Post date: [August 26, 2001, 8:24pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/2 "2001-08-26T20:24:43Z")
[Great Wall Visible?](http://www.straightdope.com/classics/a2_092.html) would be the link to Cecil’s column. They really appreciate it when you add this as it allows readers to better understand what you are saying.
There is an earlier discussion. I’ll try to find in and add it here momentarily.
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### Author:  [@samclem](https://boards.straightdope.com/u/samclem)
#### Post date: [August 26, 2001, 8:35pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/3 "2001-08-26T20:35:50Z")
Found it. Here is a quote that I added to [Ask Jeeves vs. Cecil](http://boards.straightdope.com/sdmb/showthread.php?threadid=34077)
> [@](#):
>
> The Great Wall of China", by William Edgar Geil, published by
> Sturgis & Walton, New York, 1909, p.17
>
> The National Geographic Magazine, Vol. XLIII, No. 2 - February
> 1923, p.113, article “A Thousand Miles Along the Great Wall of
> China” by Adam Warwick
In both of these sources it is said that the Great Wall is visible from the Moon.
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### Author:  [@Montfort](https://boards.straightdope.com/u/Montfort)
#### Post date: [August 26, 2001, 11:26pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/4 "2001-08-26T23:26:58Z")
Stupid question… how would people know what was visible from the moon in the early 20th C. when no one visited the moon until 1969?
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### Author:  [@samclem](https://boards.straightdope.com/u/samclem)
#### Post date: [August 26, 2001, 11:43pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/5 "2001-08-26T23:43:28Z")
They couldn’t _know_, of course; they could only make guesses.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 27, 2001, 12:41am UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/6 "2001-08-27T00:41:33Z")
They knew how far away the Moon is, they knew what angular size can be resolved by the human eye, and they knew the sizes of various Earthly objects. The rest is just trig.
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### Author:  [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)
#### Post date: [August 27, 2001, 4:37pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/7 "2001-08-27T16:37:45Z")
> [@](#):
>
> \*Originally posted by Chronos \*
> \*\*They knew how far away the Moon is, they knew what angular size can be resolved by the human eye, and they knew the sizes of various Earthly objects. The rest is just trig. \*\*
But–according to Cecil, NASA, and Alan Bean, their trig was wrong.
So, where exactly did they misplace their decimal point?
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 27, 2001, 5:28pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/8 "2001-08-27T17:28:08Z")
I’m more inclined to think that the folks who got the wrong answers didn’t do the math at all. There’s a grand old tradition in journalism of making up numbers out of thin air. What might be interesting, is seeing if there’s a response to any of those early claims, by someone who actually did do the math.
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### Author:  [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)
#### Post date: [August 27, 2001, 8:46pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/9 "2001-08-27T20:46:48Z")
Welcome to the SDMB, and thank you for posting your comment.
Please include a link to Cecil’s column if it’s on the straight dope web site. To include a link, it can be as simple as including the web page location in your post (make sure there is a space **before** and **after** the text of the URL).
Cecil’s column can be found on-line at the link provided by our esteemed poster **samclem**.
* * *
moderator, «[**Comments on Cecil’s Columns**](http://boards.straightdope.com/sdmb/forumdisplay.php?forumid=1)»
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### Author:  [@samclem](https://boards.straightdope.com/u/samclem)
#### Post date: [August 28, 2001, 1:06am UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/10 "2001-08-28T01:06:13Z")
**Arnold** said
> [@](#):
>
> Cecil’s column can be found on-line at the link provided by our esteemed poster samclem.
Damn, Arnold. You’re gonna lose you Mod license if you don’t keep it straight: Posters suck up to _Mods_, not the other way around. So, I guess those chocolates I got in the mail today were from you. 😃
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### Author:  [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)
#### Post date: [August 29, 2001, 7:24pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/11 "2001-08-29T19:24:14Z")
Yes they were. Whizzo chocolates are the best. I particularly recommend the Ram’s Bladder Cup and the Spring Surprise.
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### Author:  [@DanBlather](https://boards.straightdope.com/u/DanBlather)
#### Post date: [September 4, 2001, 4:19pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/12 "2001-09-04T16:19:31Z")
I doubt that the Great Wall itself is visible, but I could imagine that the _effects_ of a wall could be seen from space. Isn’t there a several thousand mile long fence in Australia to keep rabbits out of pasture? I imagine the vegetation on the two sides could vary enough to be visible from space.
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### Author:  [@Irishman](https://boards.straightdope.com/u/Irishman)
#### Post date: [September 5, 2001, 3:08pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/13 "2001-09-05T15:08:11Z")
From space? Yes. From the MOON? No.
Think about it. From the Moon, the Earth looks like a big ball of white, with blue marbling. There’s occasionally a _hint_ of brown from a desert peeking out or maybe some dark green from trees. We’re talking the difference between the Sahara and the Congo, not between you and your neighbor’s lawns. No fence line will stand out - even the Great Wall.
What _might_ have inspired people to think it could be visible is the length of the wall is sufficient that it could be discernable. However, that fails to recognize that the _width_ of the wall is tiny, so it would not have enough width to show up as a line. Ergo, the wall should not be visible.
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### Author:  [@partyofone](https://boards.straightdope.com/u/partyofone)
#### Post date: [September 5, 2001, 11:04pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/14 "2001-09-05T23:04:30Z")
One thing that most posters have ignored is that part of the visibility of an object is its contrast against the background. The smaller the subtense, the more contrast required to see it. For something that’s close to the visual acuity limit, you need white on a black background or vice versa to see anything at all. This is clearly not the case for objects on the Earth. You’re only getting gray on brown or green, which are pretty similar in brightness and therefore provides minimal contrast.
Moreover, your ability to see stuff from Earth orbit takes advantage of color differences, but your color vision is considearbly worse than your monochrome vision. From the moon, you are only able to use your monochrome vision, and at that range everything looks to be at the same contrast.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [July 16, 2007, 4:23pm UTC](https://boards.straightdope.com/t/great-wall-of-china/78213/16 "2007-07-16T16:23:29Z")
> [@](#):
>
> Damn, Arnold. You’re gonna lose you Mod license if you don’t keep it straight: Posters suck up to Mods, not the other way around.
Man, this quote looks funny now, from the space of six years away.