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[[Image:Great_wall.jpg|right|180px|thumb|The Great Wall Of China.  Image by [http://philip.greenspun.com/ Philip Greenspun]]]

[[Image:Great_wall.jpg|right|thumb|The Great Wall Of China.  Image by [http://philip.greenspun.com/ Philip Greenspun]]]

The '''Great Wall of China''' is a long wall in [[China]]. It was constructed in ancient times as a barrier against invading armies. This was unsuccessful as the Mongols simply bribed the guards.<ref>Hucker, Charles O.  ''China's Imperial Past: An Introduction to Chinese History and Culture.''  Stanford UP, 1997.</ref>  It is 4,000 miles long and more than 20 feet tall.  

The '''Great Wall of China''' is any of several extended frontier fortifications in northern China. These were constructed in ancient times as barriers against invading armies. The original wall was built in 220–206 BC by [[Qin Shi Huang]], the emperor who unified China. In modern times, this wall is no longer recognizable from the the ground, but it has been mapped using satellite photography. The modern form of the Great Wall was built during the [[Ming dynasty]]

Work started in 500 BC under [[Qin Shi Huang]], connecting older walls which were constructed by individual states. Most of the work was done in the [[Ming Dynasty]]. <ref>Susan Wise Bauer, ''The History of the Ancient World''</ref>Towers were built; originally as watchtowers, but later [[cannon]]s<ref>http://factsanddetails.com/china.php?itemid=27&catid=2&subcatid=1</ref> were added.

This was unsuccessful as the Mongols simply bribed the guards.<ref>Hucker, Charles O.  ''China's Imperial Past: An Introduction to Chinese History and Culture.'' Stanford UP, 1997.</ref> It is 4,000 miles long and more than 20 feet tall.  

The Great Wall of China is not the only [[human|man-made]] structure visible from space, or the [[Moon]]. This legend probably originated with [[Richard Halliburton]]'s 1938 "Second Book of Marvels". It has been disputed whether it is even visible from low earth orbit. A 2008 article in Scientific American stated: "The unglamorous truth is that the wall is only visible from low orbit under a specific set of weather and lighting conditions. And many other structures that are less spectacular from an earthly vantage point—desert roads, for example—appear more prominent from an orbital perspective."<ref>[http://www.sciam.com/article.cfm?id=is-chinas-great-wall-visible-from-space Scientific American, ''Is China's Great Wall Visible from Space? Though it stretches for some 4,500 miles, the ancient Chinese fortification is not as visible from orbit as modern desert roads'', by Mara Hvistendahl, February 21, 2008]</ref> In 2005 an [[American]] astronaut (of [[Chinese]] descent) succeeded in [[photograph]]ing the Wall. <ref>BBC News, Shanghai ''Great Wall visible in space photo'', by Francis Markus, 19 April, 2005 [http://news.bbc.co.uk/1/hi/world/asia-pacific/4459311.stm BBC News report of "China Daily" article 4/19/2005]</ref>  

 

The Great Wall is not the only [[human|man-made]] structure visible from space, or the [[moon]]. This claim was popularized by a May 1932 ''Ripley's Believe it or not'' cartoon which stated that the wall is "the mightiest work of man, the only one that would be visible to the human eye from the moon." The claim also appears in Richard Halliburton's ''Second Book of Marvels'' (1938).<ref name=Hvistendahl>Hvistendahl, Mara, [http://www.sciam.com/article.cfm?id=is-chinas-great-wall-visible-from-space Is China's Great Wall Visible from Space? Though it stretches for some 4,500 miles, the ancient Chinese fortification is not as visible from orbit as modern desert roads]", ''Scientific American'', February 21, 2008.</ref>

 

 

In 2005 an [[American]] astronaut (of [[Chinese]] descent) succeeded in [[photograph]]ing the Wall. <ref>BBC News, Shanghai ''Great Wall visible in space photo'', by Francis Markus, 19 April, 2005 [http://news.bbc.co.uk/1/hi/world/asia-pacific/4459311.stm BBC News report of "China Daily" article 4/19/2005]</ref>  

There is no truth to the notion that there are ''few'' human structures visible from space; Cecil Adams comments:

There is no truth to the notion that there are ''few'' human structures visible from space; Cecil Adams comments:

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Any number of man-made structures can be seen from space, provided we mean "structure" to mean "anything built." Many of these are things that look like long, straight lines when seen from far off, such as [[highway]]s, [[railroad]]s, [[canal]]s, and of course walls. If the orbit is low enough you can see even more, I have here a photo of [[Cape Canaveral]] taken during the Gemini V flight in which the big Launch Complex 39, used for the Apollo missions, is clearly visible. Another photo of the Nile delta, taken from a height of 100 miles, shows an extensive road network. Gemini V astronauts Gordon Cooper and Charles Conrad were able to spot, among other things, a special checkerboard pattern that had been laid out in [[Texas]], a rocket-sled test in [[New Mexico]], and the [[aircraft carrier]] that would later pick them up in the Atlantic, along with a destroyer trailing in its wake.<ref>[http://www.straightdope.com/classics/a2_092.html Is the Great Wall of China the only man-made object you can see from space?] Cecil Adams, ''The Straight Dope''</ref>

Any number of man-made structures can be seen from space, provided we mean "structure" to mean "anything built." Many of these are things that look like long, straight lines when seen from far off, such as [[highway]]s, [[railroad]]s, [[canal]]s, and of course walls. If the orbit is low enough you can see even more, I have here a photo of [[Cape Canaveral]] taken during the Gemini V flight in which the big Launch Complex 39, used for the Apollo missions, is clearly visible. Another photo of the Nile delta, taken from a height of 100 miles, shows an extensive road network. Gemini V astronauts Gordon Cooper and Charles Conrad were able to spot, among other things, a special checkerboard pattern that had been laid out in [[Texas]], a rocket-sled test in [[New Mexico]], and the [[aircraft carrier]] that would later pick them up in the Atlantic, along with a destroyer trailing in its wake.<ref>[http://www.straightdope.com/classics/a2_092.html Is the Great Wall of China the only man-made object you can see from space?] Cecil Adams, ''The Straight Dope''</ref>

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