The Great Wall of China is one of The New Seven Wonders of the World and the most famous building of China. It is so majestic, beautiful and charming. Whether it can be seen from space? It always be a hot-discussed problem. Below is some point of view :

Popular beliefs ranging from Ripley’s Believe It or Not!’s cartoons from 1930s, which claimed that the Great Wall is “the mightiest work of man, the only one that would be visible to the human eye from the moon,” to Richard Halliburton’s 1938 book Second Book of Marvels which makes a similar claim, have persisted, assuming urban legend status, and sometimes even appearing in school textbooks. Arthur Waldron, author of The Great Wall of China: From History to Myth, has speculated that the belief might go back to the fascination with the “canals” once believed to exist on Mars.

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 is only exceeded by the Chinese Wall, which makes  a considerable figure upon the terrestrial globe, and may be discerned at the moon.”

The Great Wall is a maximum 9.1 m wide and is about the same color as the soil surrounding it. Based on the optics of resolving power only an object of reasonable contrast to its surroundings 70 miles or more in diameter would be visible to the unaided eye from the moon, whose average distance from Earth is 238,857 miles. The apparent width of the Great Wall from the moon is the same as that of a human hair viewed from 2 miles 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 seeing 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, i.e., an altitude of as little as 100 miles. 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).

Have read too much opinions above, I think that whether the Great Wall can be seen from the space is not important, it’s great is not reflected in here, it’s the treasure of human history and civilization, and this is enough! Let us stop arguing this silly questions  forever.