One claim, checked: “The Great Wall is visible from space.”
Sample check, posted so you can see what one looks like.
The claim: “The Great Wall of China is the only man-made object visible from space” (and its louder cousin: “visible from the Moon”).
Verdict: fails as told, both versions, with one small true piece inside: it can be photographed from orbit. The more interesting part: the myth predates spaceflight by two centuries, so nobody who repeated it could have checked it.
The paper trail starts in 1754. The earliest known version is a 1754 letter by the English antiquary William Stukeley, who likens Hadrian's Wall to “the Chinese Wall... [which] may be discerned at the Moon.” By 1895 it's a travel-book commonplace: “the only work of human hands on the globe visible from the Moon.” A 1932 Ripley's Believe It or Not! strip turns it into a catchphrase. First human spaceflight: 1961.
From the Moon: no. NASA, 2005: “It certainly isn't visible from the Moon.” Neil Armstrong, asked after Apollo 11, described continents, lakes, colors, and no man-made structures. Even the Moon version was never anything but repetition.
From orbit, naked eye: barely, rarely. NASA: the wall “generally isn't [visible], at least to the unaided eye in low Earth orbit.” Scientific American, 2008: both legends are false; the wall shows “only... under a specific set of weather and lighting conditions,” and desert roads and runways turn out to be more conspicuous. Astronaut Jeffrey Hoffman, five shuttle flights: “I never saw the wall.”
What is true, and the textbook problem. It can be photographed from orbit: Leroy Chiao's 2004 ISS photos were the first confirmed ones, and Chiao himself “didn't see the wall, and wasn't sure if the picture showed it.” Radar images pick out sections easily. In 2003 Yang Liwei, China's first astronaut, said he couldn't see it; there was talk of rewriting school textbooks. In 2004 the European Space Agency published a satellite photo it said showed the wall; it later admitted the image was actually a river near Beijing.
The point. The claim is nearly three centuries old and has never needed to be true. It just needed to be repeated.
Sources. – Stukeley, The Family Memoirs of the Rev. William Stukeley, vol. 3, p. 142 (letter of 1754; printed 1887); Henry Norman, The Peoples and Politics of the Far East, p. 215 (1895). – Ripley's Believe It or Not!, 1932 (strip scan, linked above). – NASA, “China's Wall Less Great in View from Space,” May 9, 2005 (archived, linked above). – Scientific American, “Is China's Great Wall Visible from Space?”, Feb 21, 2008 (linked above). – BBC News, “Great Wall visible in space photo,” Apr 19, 2005. – People's Daily, “ESA admits 'Great Wall' on satellite photo a mistake,” May 21, 2004 (archived, linked above).
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