Great Wall of China from space (Part I)
The Great Wall Of China has been around for a long time; long enough for some tall tales to grow up around it. Dr Karl reckons some of them are really stretching the truth.
There's a story that was around long before the Internet. It claims that you can easily see the Great Wall of China from the Moon. It is such a simple sentence, and yet, it is so wrong, in so many ways, that it is hard to know where to begin.
So first, let me start with the Wall itself. Most of us have the mental image of a huge and monolithic wall – but it's not quite that straightforward.
The Chinese have been building major Walls for at least 2,500 years. Chinese chronicles describe various long Walls to separate one internal feudal kingdom from another, or to protect against foreign enemies.
In 221 BC, the Emperor Shih huang-ti, the so-called First Emperor, came to power after unifying many small states into the single country we now call China.
China was so huge that he had to build an extensive network of highways to shift his troops around quickly. And to protect his farmers against invading nomads from the north, he connected and fortified all the existing walls, and added signal towers and garrison stations. His so-called "Long Rampart" stretched from the ocean in the east, and across Inner Mongolia to the edge of Tibet in the west. The Long Rampart was begun in 219 BC, and finished 15 years later, seven years after his death.
The labour force needed was immense. The workers included some 300,000 soldiers, prisoners-of-war and even criminals from the jails. The distances were so huge, that it was extremely difficult to get supplies to the distant reaches of the Rampart. One chronicle writes that, "of 182 loads of grain dispatched, only one would reach its destination, the rest being eaten or sold along the road."
Some of the Wall was built of stone, but much of it was built of mud, and so it crumbled with time. By only 7 centuries later, so much had eroded away that the Tungustic Wei and Tsi Dynasties wrote not of rebuilding the Great Wall – but of building it.
But their work also decayed with time.
And so the Great Wall had to be built (or rebuilt) yet again during the Ming Dynasty (1368 to 1644). The Ming Emperors had to repel frequent attacks by the barbarians from the north - so the Great Wall was a military necessity. Not only did the Ming emperors repair the entire length of the Great Wall, they added new loops. But this time, they used bricks and stones. They added some 20,000 towers (mini-fortresses) and 10,000 signal beacons.
A Chinese general reported in the Cheng Hua period (1465 to 1488) that "to guard 300 miles he had 25 camps, but each contained only from 100 to 200 men, and one man could not guard 200 yards of frontier day and night." So Cheng Hua cleverly offered the soldiers large grants of land near the Wall, so they would be happy to be permanently garrisoned there.
After the Ming Dynasty, the Manchus allowed the wall to fall into disrepair. The Emperor Kang Hsi ordered a Jesuit Priest, Father Regis, to map his empire. It took him from 1708-1716. Part of Father Regis' task was to travel along the entire length of the wall. He said that in the Chihli Province, there was only a facing of brick left, and that in other parts, it was just a sand ridge. "Along the northern border of Shansi, the Wall is made of clay without battlements, and is only about 5 feet high. West of Shansi it is a narrow mud rampart, sometimes even only a ridge of sand."
So today, some sections cannot even be recognised as having once been a wall, while others are in as-new condition. A good example of this is one specific part of the Wall, at Pa-ta-ling, about 70 km northwest of Beijing – it's the bit that most Westerners visit. It was rebuilt in the 1950s, and today, it's in absolutely superb condition. This section of the Wall is a magnificent structure built of stone and rock, about 10 metres wide and 10 metres high, but higher at the watch towers. But most of the Great Wall is nothing like this.
We do have personal anecdotal evidence from a British athlete who ran along long stretches of the Wall to raise money for charity. In 1988, Edward Ley-Wilson and David Wightman ran some 1,900 kilometres of the Great Wall. Over the 47 days, they averaged about 41 kilometres per day. Mr. Ley-Wilson wrote this about the integrity of the Great Wall:
"Wall clearly discernible and only moderately eroded or broken along its length - 22% of the 1,900 kilometre run.
Wall usually discernible but frequently broken/eroded 41%.
Wall scarcely discernible, almost totally eroded and running by reference to maps 37%."
So the Great Wall of China is not a single huge structure, but a whole bunch of smaller structures in various stages of repair, ranging from mint condition to absolute decay. And the other myth that you can see it from the Moon – well, I'll deal with that, next time...
Published 30 August 2007
© 2015 Karl S. Kruszelnicki Pty Ltd