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:Any number of man-made structures can be seen from space, provided we construe "structure" to mean "anything built." Many of these are things that look like long, straight lines when seen from afar, such as highways, railroads, canals, 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 manmade 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 construe "structure" to mean "anything built." Many of these are things that look like long, straight lines when seen from afar, such as highways, railroads, canals, 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 manmade object you can see from space?] Cecil Adams, ''The Straight Dope''</ref>

The work on the wall started in 5th century BC and continued for 2,000 years. It spans almost 4,00 miles is at points more than 20 feet tall. At regular intervals towers were built. At first they functioned purely as watchtowers but later on they were modified to include cannons and defenses against aerial attacks.

 

The work on the wall started in 5th century BC and continued for 2,000 years. It spans almost 4,00 miles and at points it is more than 20 feet tall. At regular intervals towers were built. At first they functioned purely as watchtowers but later on they were modified to include cannons and defenses against aerial attacks.

== References ==

== References ==

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