The Great Wall of China is often thought as being the only man-made object visible from the moon. In reality no single, man-made object on Earth can be seen with a naked eye from the Earth's moon. Given good circumstances one might be able to discern the result of some human activity such as the changing of the Netherlands' coast or the partial drying out of the Aral Sea, but even that would not be easy. Some astronauts have reported seeing the Great Wall from low earth orbit, among a number of man-made structures. In reality, a viewer would need visual acuity 17,000 times better than normal (20/20) to see the Wall from the Moon, and vision 8 times better than normal to see it from low earth orbit.