The Great Wall of China, as seen from the space shuttle. Contrary to popular belief, an unaided viewer cannot see it from the moon. One shuttle astronaut said, “We can see things as small as airport runways, [but] the Great Wall is almost invisible from only 180 miles up.” An Apollo astronaut said no human structures were visible at a distance of a few thousand miles. And — most tellingly — Chinese astronaut Yang Liwei couldn’t see it at all.