The Great Wall of China – A Wonder
The Great Wall of China is a series of fortifications made
of stone, brick, tamped earth, wood, and other materials,
generally built along an east-to-west line across the historical
northern borders of China in part to protect the Chinese Empire
or its prototypical states against intrusions by various nomadic
groups or military incursions by various warlike peoples or
forces. Several walls were being built as early as the 7th century
BC; these, later joined together and made bigger, stronger,
and unified are now collectively referred to as the Great Wall.
Especially famous is the wall built between 220–206 BC by the
first Emperor of China, Qin Shi Huang. Little of that wall remains.
Since then, the Great Wall has on and off been rebuilt, maintained,
and enhanced; the majority of the existing wall was reconstructed
during the Ming Dynasty.
Other purposes of the Great Wall have included border
controls, allowing the imposition of duties on goods transported
along the Silk Road, regulation or encouragement of trade and
the control of immigration and emigration. Furthermore, the
defensive characteristics of the Great Wall were enhanced by
the construction of watch towers, troop barracks, garrison
stations, signalling capabilities through the means of smoke or
fire, and the fact that the path of the Great Wall also served as a
The Chinese were already familiar with the techniques of wallbuilding by the time of the Spring and Autumn Period between the 8th and 5th centuries BCE. During this time and the subsequent Warring States Period, the states of Qin, Wei, Zhao, Qi, Yan and Zhongshan all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were made mostly by stamping earth and gravel between board frames. Qin Shi Huang conquered all opposing states and unified China in 221 BCE, establishing the Qin Dynasty. Intending to impose centralized rule and prevent the resurgence of feudal lords, he ordered the destruction of the wall sections that
Dr. R. Kuberan,divided his empire along the former state borders. To protect the empire against intrusions by the Xiongnu people from the north, he ordered the building of a new wall to connect the remaining fortifications along the empire’s new northern frontier. Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources. Stones from the mountains were used over mountain ranges, while rammed earth was used for construction in the plains. There are no surviving historical records indicating the exact length and course of the Qin Dynasty walls. Most of the ancient walls have eroded away over the centuries, and very few sections remain today.
The Great Wall concept was revived again during the Ming Dynasty in the 14th century, and following the Ming army’s defeat by the Oirats in the Battle of Tumu. The Ming had failed to gain a clear upper hand over the Manchurian and Mongolian tribes after successive battles, and the long-drawn conflict was taking a toll on the empire. The Ming adopted a new strategy to keep the nomadic tribes out by constructing walls along the northern border of China. Acknowledging the Mongol control established in the Ordos Desert, the wall followed the desert’s southern edge instead of incorporating the bend of the Huang He. Unlike the earlier Qin fortifications, the Ming construction was stronger and more elaborate due to the use of bricks and stone instead of rammed earth. Up to 25,000 watchtowers are estimated to have been constructed on the wall. As Mongol raids continued periodically over the years, the Ming devoted considerable resources to repair and reinforce the walls. Sections near the Ming capital of Beijing were especially strong. Qi Jiguang between 1567 and 1570 also repaired and reinforced the wall, faced sections of the ram-earth wall with bricks and constructed 1,200 watchtowers from Shanhaiguan Pass to Changping to warn of approaching Mongol raiders. Towards the end of the Ming Dynasty, the Great Wall helped defend the empire against the Manchu invasions that began
around 1600. Even after the loss of all of Liaodong, the Ming army under the command of Yuan Chonghuan held off the Manchus at the heavily fortified Shanhaiguan pass, preventing the Manchus from entering the Chinese heartland. In 2009, an additional 290 km (180 mi) of previously undetected portions of the wall, built during the Ming Dynasty, were discovered. The newly discovered sections range from the Hushan mountains in the northern Liaoning province, to Jiayuguan in western Gansu province. The sections had been submerged over time by sandstorms which moved across the arid region.
Early Western Reports of the Wall
The North African traveller Ibn Battuta, who was in Guangzhou ca. 1346, inquired among the local Muslims about the wall that, according to the Qur’an, Dhul-Qarnayn had built to contain Gog and Magog. Ibn Battuta reported that the wall was “sixty days’ travel” from the city of Zeitun (Quanzhou); Hamilton Alexander Rosskeen Gibb noted Ibn Battuta has confused the Great Wall of China with that built by Dhul-Qarnayn. This indicated that Arabs may have heard about China’s Great Wall during earlier periods of China’s history, and associated it with the Gog and Magog wall of the Qur’an. But, in any event, no one of Ibn Battuta’s Guangzhou interlocutors had seen the wall or knew anyone who had seen it, which implies that by the late Yuan the existence of the Great Wall was not in the people’s living memory, at least not in the Muslim communities in Guangzhou. Soon after Europeans reached the Ming China in the early 16th century, accounts of the Great Wall started to circulate in Europe, even though no European was to see it with his own eyes for another century.
Some of the following sections are in Beijing municipality, which were renovated and which are regularly visited by tourists today.
- “North Pass” of Juyongguan pass, known as the Badaling. When used by the Chinese to protect their land, this section of the wall had many guards to defend China’s capital Beijing. Made of stone and bricks from the hills, this portion of the Great Wall is 7.8 metres (26 ft) high and 5 metres (16 ft) wide.
- “West Pass” of Jiayuguan (pass). This fort is near the western edges of the Great Wall.
- “Pass” of Shanhaiguan. This fort is near the eastern edges of the Great Wall.
- One of the most striking sections of the Ming Great Wall is where it climbs extremely steep slopes. It runs 11 kilometres (6.8 mi) long, ranges from 5 to 8 metres (16–26 ft) in height, and 6 metres (20 ft) across the bottom, narrowing up to 5 metres (16 ft) across the top. Wangjinglou is one of
Another notable section lies near the eastern extremity of the wall, where the first pass of the Great Wall was built on the Shanhaiguan (known as the “Number One Pass Under Heaven”). 3 km north of Shanhaiguan is Jiaoshan Great Wall, the site of the first mountain of the Great Wall. 15 km northeast from Shanhaiguan, is the Jiumenkou, which is the only portion of the wall that was built as a bridge.
Before the use of bricks, the Great Wall was mainly built from rammed earth, stones, and wood. During the Ming Dynasty, however, bricks were heavily used in many areas of the wall, as were materials such as tiles, lime, and stone. The size and weight of the bricks made them easier to work with than earth and stone, so construction quickened. Additionally, bricks could bear more weight and endure better than rammed earth. Stone can hold under its own weight better than brick, but is more difficult to use. Consequently, stones cut in rectangular shapes were used for the foundation, inner and outer brims, and gateways of the wall. Battlements line the uppermost portion of the vast majority of the wall, with defensive gaps a little over 30 cm (12 in) tall and about 23 cm (9.1 in) wide.
While some portions north of Beijing and near tourist centres have been preserved and even extensively renovated, in many locations the Wall is in disrepair. Those parts might serve as a village playground or a source of stones to rebuild houses and roads. Sections of the Wall are also prone to graffiti and vandalism. Parts have been destroyed because the Wall is in the way of construction. More than 60 km (37 mi) of the wall in Gansu province may disappear in the next 20 years, due to erosion from sandstorms. In places, the height of the wall has been reduced from more than five metres (16.4 ft) to less than two metres. The square lookout towers that characterize the most famous images of the wall have disappeared completely. Many western sections of the wall are constructed from mud, rather than brick and stone, and thus are more susceptible to erosion. In August 2012, a 30 metre section of the wall in north China’s Hebei province collapsed after days of continuous heavy rains. Watchtowers and barracks: Communication between the army units along the length of the Great Wall, including the ability to call reinforcements and warn garrisons of enemy movements, was of high importance. Signal towers were built upon hill tops or other high points along the wall for their visibility.
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. 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 colour as the soil surrounding it. Based on the optics of resolving power (distance versus the width of the iris: a few millimetres for the human eye, metres 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 Lu, Expedition 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.”
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