China

The Great Wall of China

by Jenny McGlone
Chapel Hill, NC, United States

Most students of history have heard of China’s Great Wall. Scholars seem to agree that this wall was constructed many centuries ago on an east-west orientation to protect China from neighboring invaders to its north. Much of the wall fell into ruin as the need for such protection subsided. In fact, one historian figured out that only 8.2 percent of it remains intact, while 22 percent of it has completely vanished.

How Long Was the Great Wall?

Did you know that nobody is sure how long the Great Wall really was? Until a few years ago, estimates centered on 5,500 miles. Recently, however, archaeologists have proposed that the actual original length was closer to 13,170 miles. Not all of this was built by humans, as rivers, steep mountains, and other natural barriers were incorporated into the Wall. Stretched out, this Wall could run more than halfway around the globe!

How and When Was It Built?

The first sections of the Wall were constructed as long ago as the 8th century BCE, using mud and gravel that was packed together. With the invention of brick-making during the Tang Dynasty (618-907 CE), these sturdier, lighter components were preferred. One of the ingredients in holding the bricks to each other was sticky rice juice!

You may be interested to know that the Wall was not just a wall. The builders thought of every possible defensive need, so they included watchtowers, drainage systems, parapets, horse ramps, armories, and barracks. In the best-preserved, Mutianyu section of the wall, reinforced with granite in 1569, there are 23 watchtowers among 2,250 meters.

How Tall Was the Wall?

The Mutianyu section’s average height is 7 to 8 meters in height, 4 to 5 meters in width. The top of the Wall is narrower than the bottom. In some places, now, the Wall has eroded to fewer than 2 meters.

Is the Urban Myth True?

Despite the Wall’s size and length, the popularly held belief that it can be seen from the moon is actually false. Scientists have estimated that it would need to be 70 miles wide to be viewed with the unaided eye from such a distance. Another comparison would be trying to see a human hair from 2 miles away. NASA has published photographs demonstrating the lack of evidence for this myth, so you can see (or rather, not see) for yourself.

The Great Firewall of China

A Global Math Story reader pointed out that anyone lucky enough to visit the Wall will be unable to post the evidence on social media until after leaving the country. China does not permit the public to access Facebook, Twitter, and other networks.

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Math Questions

  1. How many times back and forth across the US could the Great Wall go?
  2. If only 8.2 percent of the wall remains intact, how long is that?
  3. If 22 percent of the Wall has vanished, how much length is that?
  4. It took 500,000 people to build the Wall. Look up the population of China during the Ming Dynasty and figure out what percentage of the population that was.

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Social Justice Questions

  1. Many workers were seriously injured or killed during construction of the Wall. Since it was built for protection, was this loss of life justifiable?
  2. Do some research on internet access in China. What reasons does the government give for restricting use? What do you think of people using virtual private networks to get around firewalls?

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Resources

  1. Website on the Wall
  2. Information on the history of the Wall during the Ming Dynasty (1368 to 1644)
  3. Another website on the Wall

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