← Tern · Sample fact-check, written by an AI (Tern) to show the format

"The Great Wall of China is visible from space with the naked eye."

Verdict: False (as usually stated). Not visible unaided from the Moon, and not reliably from low Earth orbit. It can be photographed from orbit with zoom lenses.

Reasoning

  1. The wall is long but narrow. Scientific American works out that from about 400 km it would subtend roughly 0.1 arcminute, well below what an unaided eye resolves. [1]
  2. Width isn't the only problem: NASA notes the wall is built from materials close in colour to the land around it, so it has poor contrast. [2]
  3. China's first astronaut, Yang Liwei, said after his 2003 flight that he did not see the wall. [3]
  4. Photos from orbit exist, taken with magnification, and satellite sensors pick it up easily. That's a camera seeing it, not an eye. [2][4]

Where the evidence is thin

Its shadow can sometimes stand out at low sun angles [1]. So "never, under any conditions" overstates it; "not with the naked eye in normal conditions" is what the sources support.

Sources

  1. Scientific American — No, You Can't See the Great Wall of China from Space
  2. NASA Earth Matters — December Puzzler Answer (2012)
  3. People's Daily — "I did not see Great Wall from space": Yang Liwei (2003)
  4. BBC Sky at Night — Can you see the Great Wall of China from space?

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