Great Wall of China
The Great Wall of China is an ancient wall in China. It is made of stone, pounded dirt, and other things. It was built to protect the north of the empire of China from enemy attacks. It is the longest structure humans have ever built. It is about 21,196 kilometres (13,171 miles) long, 9.1 metres (30 feet) wide and 15 metres (50 feet) high. The earlier sections on the wall are made of compacted dirt and stone. Later in the Ming Dynasty they used bricks. There are 7,000 watch towers. There are block houses for soldiers. There are beacons to send smoke signals.
Several walls have been built that were called the Great Wall of China. The first was built in the 7th century BC. The most famous wall was built between 220–200 BC by the first Emperor of Imperial China, Qin Shi Huang. Not much of this wall remains. It was much farther north than the current wall. The current wall was built during the Ming Dynasty.
History[change | change source]
The First Emperor of China started the Qin Dynasty. The Xiongnu tribes in the north of China (who are also called the Huns) were his enemies. The land in some parts of China is easy to cross, so Qin Shi Huang started building the Great Wall to make it more difficult for the Xiongnu to invade China.
Other dynasties in China worked more on the wall and made it longer. The Han, Sui, Northern and Jin Dynasties all repaired, rebuilt or expanded the Great Wall. During the Ming Dynasty, major rebuilding work took place. Sections of the wall were built with bricks and stone instead of earth.
Construction and rebuilding of the Great Wall[change | change source]
Builders used materials that were nearby. Some parts of the wall were made of mud, straw, and twigs. Thousands of workers died from giant falling stones, exhaustion, disease, animal attacks, and starvation. The idea that workers who died were buried in and under the Great Wall is a myth.
Visibility from space[change | change source]
Rumors about astronauts being able to see the Great Wall from the moon are not scientifically proven. The Great Wall has shown up in radar images taken from space, but scientists are not sure whether it would be possible for astronauts to see the wall with a naked eye. One astronaut who spoke about not being able to see the Great Wall from space was Neil Armstrong.
References[change | change source]
- Construction of the Great Wall
- Paul and Bernice Noll's Window on the World. History of The Great Wall of China. 
- Norberto López-Gil. "Is it Really Possible to See the Great Wall of China from Space with a Naked Eye?". Journal of Optometry 1 (1): 3–4. http://www.journalofoptometry.org/Archive/vol1/pdf/02%20Vol1-n1%20Letter%20to%20the%20Editor.pdf.
- "China's Wall Less Great in View from Space". NASA. 2005. http://www.nasa.gov/vision/space/workinginspace/great_wall.html. Retrieved 2008-11-21.