Can the Great Wall Be Seen from the Space?
Measuring about 21,196 kilometers (13,170 miles) long, the Great Wall of China is no doubt the longest manmade project on the earth. It was once widely believed that it can be seen from the space. Many astronauts have verified this saying and taken photos as evidence. Some medium even reported with affected seriousness, "The biggest building the astronauts could see from the space is the wall, which looks very much like a black worm." Consequently, this statement has gone deep into people's minds and become an honor that Chinese people enjoyed for years.
Is the Great Wall truly visible from the moon? Yang Liwei, China's first astronaut who was lifted into the outer space by the spacecraft Shenzhou V on Oct.15, 2003, gave a definite answer "No" to a reporter after he reached the ground. Yang's negative response in a practical way may probably put out a fair number of people's passion. But it powerfully corrected the misconception. The wall is indeed majestic, but you won't see it from the space!
In fact, besides Yang Liwei, there are a lot of astronauts said the Wall could not be seen from the space. Neil Alden Armstrong, the American aviator who first set foot on the moon in 1969, was asked a thousand times whether or not he had seen the Great Wall from the moon. Recently from a sound recording that announced by NASA Johnson Space Center, Armstrong said that he had seen the continent, lakes and blue spots touched with red. But he could not make out any manmade object on the earth from the moon.
What's more, Buzz Aldrin, one of the two American astronauts besides Neil Alden Armstrong that first landed on the moon, insisted that the wrong statement was from people's misunderstanding. Jeffrey Alan Hoffman, the former American astronaut claimed that he had not seen the Wall though much time was spent to overlook the earth including many moments skimming over China's airspace. Dennis Anthony Tito, the first space tourist from America who spent the space vacation in 2001, also said the Wall is invisible from the space.
Theoretically speaking, the Great Wall is absolutely invisible from the space. It is narrow and irregular. In space, something irregular is hard to be observed. Measuring about 10 meters (11 yards) wide on average, it is easily to be immerged from the surrounding environment. Depended solely on the unaided eyes, it is hardly distinguished at an altitude of 65,617 feet. It is totally invisible at a height of 196,850 feet. To watch the wall on the moon is equivalent to seeking for a single hair from 2,688 meters (2,940 yards) away. To say an astronaut can see the it from space is obviously not true.
To add, some people introduced an idea to make the Great Wall visible from the space. If we install bright spotlights on the wall, no matter they are big or small, astronauts can see the lights at night. Therefore, some believe that the wall can be showed up from the surrounding environment as long as the angle of the sunlight is appropriate. But this suggestion has not been carried out by scientific experiment. In conclusion, it is generally accepted that the wall cannot be seen from the space.
Hope this helps!
The wall we saw today were mostly built during the Ming Dynasty. It's about 3 meters tall and 10 to 15 meters wide.