Why, Do You Know, Why Reasons

Do you know the 'why' reasons, or, do the 'whys' often bother you for scientific explanations? For instance, you do know that stars twinkle, but do you know the reasons why, and how? Or, do you know the 'why' reasons behind falling in love? Or, do you know the reasons why dogs bury bones? Probably many of you don’t! Why Corner – the 'why' blog, answers these 'whys' for basic knowledge, with real reasons for the 'why' facts. So, just know them all here if you have the 'why' urge, that is!

Feb 25, 2008

Do you know why the Great Wall of China was built?

Prof. Know Why answers:

The Great Wall of China is probably the China's best-known monument and one of its most popular tourist destinations. In 1987 it was designated a World Heritage Site by the United Nations Educational Scientific and Cultural Organization (UNESCO) and in 2007 it was elected one of the New 7 Wonders of the world.

Wonder! –It certainly is, stretching so many miles. But, contrary to the popular belief, the Great Wall of China is not a single, continuous structure. Rather, it consists of a network of walls with watch-towers at intervals that leave the frontier open in places. Estimates of the total length of the monument vary, depending on which sections are included and how they are measured. According to conservative estimates, the Great Wall of China is about 2,400 km long. While, other estimates cite a length of 6,400 km or even longer. From Hebei Province on the gulf of Bo Hai (a gulf of the Yellow Sea) in the east, the Great Wall of China stretches to Jiayuguan in Gansu Province in the west. The top of the walls have space, designed for soldiers to march. The Wall, at its most impressive site around Beijing, measures at least 7.6 m in height and up to 9 m in width, tapering from the base to the top. However, these dimensions vary greatly at other points.

But why was the Great Wall of China built? The natural answer that passes our mind at the first thought is protection or safe-guard from invaders and enemies. Well, that’s true! The Great Wall of China was the greatest manmade military defense structure in ancient China. The Great Wall was built mainly to protect China’s northern border from the Mongolians and other invaders.

But the Great Wall of China was not built at one time. It took several dynasties to complete the work. Based on the technology available at different dynasties, the Great Wall was usually built with local materials, mostly earth and stones. Natural terrain such as mountain ridges was often taken advantage of to form part of the wall.

There were two major periods of construction of the Great Wall, one during the Qin dynasty, and the second during the Ming dynasty. The construction first started more than 3000 years ago during the Warring States period, before China was unified. In 221 B.C., under the first emperor of China, Qin Shihuangdi, sections of earlier fortifications were joined together to form a united defense system against invasions from the north. It was called the “Chang Cheng” (long wall) of Shihuangdi. From then on, all successive Chinese dynasties had a hand in repairing, re-building, lengthening, modifying and preserving the Great Wall. The construction continued up to the Ming dynasty (1368–1644), when the Great Wall became the world's largest military structure. Most of the Great Wall that we see today was built in the Ming Dynasty.

There is a long-standing myth about the Great Wall of China that it is visible from outer space. But, actually, it is not visible with the naked eye from outer space. The astronauts have confirmed this. However, some of the wall is recognizable in special radar images, taken by satellites.

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