Changes

The '''Great Wall of China''' is a long wall located in [[China]], constructed in ancient times to act as a barrier against unlawful trespass. It is about 4,000 miles long and at several points it is more than 20 feet tall.  

The '''Great Wall of China''' is a long wall located in [[China]], constructed in ancient times to act as a barrier against unlawful trespass. It is about 4,000 miles long and at several points it is more than 20 feet tall.  

Work on the wall started in 500 BC during the rule of the first Chinese emperor, [[Qin Shi Huang]], and continued for 2,000 years. Most of the work was done during the [[Ming Dynasty]]. At regular intervals towers were built; at first they functioned purely as watchtowers but later on they were modified to include [[cannon]]s and defenses against aerial attacks.

Work on the wall started in 500 BC during the rule of the first Chinese emperor, [[Qin Shi Huang]], connecting many older walls which were constructed by individual pre-unified Chinese states to keep out northern barbarians. Most of the work was done during the [[Ming Dynasty]]. <ref>Susan Wise Bauer, ''The History of the Ancient World''</ref>At regular intervals towers were built; they originally functioned purely as watchtowers, but later on they were modified to include [[cannon]]s and defenses against aerial attacks.

A long-standing legend holds that the Great Wall of China is the only [[human|man-made]] structure visible from space, or even that it is visible from the [[Moon]].  This legend probably originated with [[Richard Halliburton]]'s 1938 "Second Book of Marvels," which made this claim. In fact, it has been disputed whether it is even visible to the naked eye from low earth orbit. A 2008 article in Scientific American stated that, "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>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 [http://www.sciam.com/article.cfm?id=is-chinas-great-wall-visible-from-space]</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>  

A long-standing legend holds that the Great Wall of China is the only [[human|man-made]] structure visible from space, or even that it is visible from the [[Moon]].  This legend probably originated with [[Richard Halliburton]]'s 1938 "Second Book of Marvels," which made this claim. In fact, it has been disputed whether it is even visible to the naked eye from low earth orbit. A 2008 article in Scientific American stated that, "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>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 [http://www.sciam.com/article.cfm?id=is-chinas-great-wall-visible-from-space]</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>