Sunday, August 4, 2013

Facts you didn't know about The Great Wall of China

You think you know The Great Wall of China? Think Again!
Sunrise at the Great Wall of China
Sunset at the Great Wall of China

Yesterday I was reading about The Great Wall of China only to discover that I know nothing about it. One of the most common "facts" I though was true, was actually false!
I decided to do a research about The Great Wall and share my findings with you.
Here is a list of 7 interesting facts you may NOT know about The Great Wall of China:


1- Longest Cemetery Ever Built: When Emperor Qin Shi Huang ordered construction of the Great Wall around 221 B.C., the labor force that built the wall was made up largely of soldiers and convicts. It is said that as many as 400,000 people died during the wall's construction; many of these workers were buried within the wall itself.It took over 2,000 years to build the Great Wall. The legend has it, “for every brick laid down, one laborer’s life was lost.”
The Great Wall of China at Jinshanling
The Great Wall of China at Jinshanling
2- "The Great Walls" Why? because it is not a single continuous wall, it is a collection of wall segments built by various dynasties over the time.
Construction of the Great Wall during Chinese History            
Map: Construction of the Great Wall during Chinese History

3- New InventionDuring the construction of the Great Wall, the Chinese invented the wheelbarrow and used it extensively.
Chinese sitting on a wheelbarrow posing for a picture
Chinese sitting on wheelbarrows posing for a picture
Wheelbarrow is still used till today and can be seen around any construction site or farms.


Chinese Wheelbarrow
Chinese Wheelbarrow
Modern Wheelbarrow
Modern Wheelbarrow


4- Watchtowers are strategically placed along the entire 5,500 miles of wall and each watchtower has its own name (like Fairy Tower, Wangjing Tower and East Tower with Five Holes)
Watchtower   
Watchtower


5- The Marathon: There is an annual marathon along the wall.




6- The Great Wall is the longest man-made structure in the world.
The Great Wall Summer 2004           
The Great Wall Summer 2004
   
7- Now to the main reason why I wrote this article about The Great Wall of China.
Believe it or not, you actually CAN'T see the Great Wall of China from Space! 
I have always heard this phrase "The Great Wall of China is the only human-made object that can be seen from outer-space." Turns out it's not even true.

The first known publishing of this "fact" was back in 1938, long before anyone was traveling in space. Since then lots of people have gone into outer space and looked at the Earth and haven't found the Great Wall.
The Great Wall is huge (5500 miles long) but in order to be visible from far away it would also have to be very wide and distinct looking from the ground. The Great Wall is very thin. If it were visible from space, every interstate highway would be too!


East Asia | Google earth
East Asia


Visibility from the Moon
One of the earliest known references to this myth appears in a letter written in 1754 by the English antiquary William Stukeley. Stukeley wrote that, "This mighty wall of four score miles in length (Hadrian's Wall) is only exceeded by the Chinese Wall, which makes a considerable figure upon the terrestrial globe, and may be discerned at the Moon." The claim was also mentioned by Henry Norman in 1895 where he states "besides its age it enjoys the reputation of being the only work of human hands on the globe visible from the Moon." The issue of "canals" on Mars was prominent in the late 19th century and may have led to the belief that long, thin objects were visible from space. The claim that the Great Wall is visible also appears in 1932's Ripley's Believe It or Not! strip and in Richard Halliburton's 1938 book Second Book of Marvels.
Earth from Space
Earth from space | Virtually by Google earth (can you spot the great wall?)

The claim the Great Wall is visible has been debunked many times, but is still ingrained in popular culture. The wall is a maximum 9.1 m (30 ft) wide, and is about the same color as the soil surrounding it. Based on the optics of resolving power (distance versus the width of the iris: a few millimeters for the human eye, meters for large telescopes) only an object of reasonable contrast to its surroundings which is 70 mi (110 km) or more in diameter (1 arc-minute) would be visible to the unaided eye from the Moon, whose average distance from Earth is 384,393 km (238,851 mi). The apparent width of the Great Wall from the Moon is the same as that of a human hair viewed from 2 miles (3.2 km) away. To see the wall from the Moon would require spatial resolution 17,000 times better than normal (20/20) vision. Unsurprisingly, no lunar astronaut has ever claimed to have seen the Great Wall from the Moon.

Visibility from low Earth orbit
A more controversial question is whether the Wall is visible from low Earth orbit (an altitude of as little as 100 miles (160 km)). NASA claims that it is barely visible, and only under nearly perfect conditions; it is no more conspicuous than many other man-made objects. Other authors have argued that due to limitations of the optics of the eye and the spacing of photoreceptors on the retina, it is impossible to see the wall with the naked eye, even from low orbit, and would require visual acuity of 20/3 (7.7 times better than normal).
Astronaut William Pogue thought he had seen it from Skylab but discovered he was actually looking at the Grand Canal of China near Beijing. He spotted the Great Wall with binoculars, but said that "it wasn't visible to the unaided eye." U.S. Senator Jake Garn claimed to be able to see the Great Wall with the naked eye from a space shuttle orbit in the early 1980s, but his claim has been disputed by several U.S. astronauts. Veteran U.S. astronaut Gene Cernan has stated: "At Earth orbit of 100 miles (160 km) to 200 miles (320 km) high, the Great Wall of China is, indeed, visible to the naked eye." Ed LuExpedition 7 Science Officer aboard the International Space Station, adds that, "it's less visible than a lot of other objects. And you have to know where to look."
In 2001, Neil Armstrong stated about the view from Apollo 11: "I do not believe that, at least with my eyes, there would be any man-made object that I could see. I have not yet found somebody who has told me they've seen the Wall of China from Earth orbit. ...I've asked various people, particularly Shuttle guys, that have been many orbits around China in the daytime, and the ones I've talked to didn't see it."
In October 2003, Chinese astronaut Yang Liwei stated that he had not been able to see the Great Wall of China. In response, the European Space Agency (ESA) issued a press release reporting that from an orbit between 160 and 320 km, the Great Wall is visible to the naked eye. In an attempt to further clarify things, the ESA published a picture of a part of the “Great Wall” photographed from Space. However, in a press release a week later (no longer available in the ESA’s website), they acknowledged that the "Great Wall" in the picture was actually a river.
Leroy Chiao, a Chinese-American astronaut, took a photograph from the International Space Station that shows the wall. It was so indistinct that the photographer was not certain he had actually captured it. Based on the photograph, the China Daily later reported that the Great Wall can be seen from space with the naked eye, under favorable viewing conditions, if one knows exactly where to look. However, the resolution of a camera can be much higher than the human visual system, and the optics much better, rendering photographic evidence irrelevant to the issue of whether it is visible to the naked eye. 
Source: http://en.wikipedia.org/wiki/Great_Wall_of_China

On the other hand, you 
can see the Pyramids of Giza from space. You can also see Minutemaid Park, the Toyota Center, and the George R. Brown Convention Center in Houston, TX 

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