Post #2074582

2026-05-05 10:35 UTC

@bodhipaksa - AI is getting improved. I asked Claude Opus 4.7 "Is it true that the Great Wall of China is the only artificial structure visible from Spain?" and the record of its so-called "thoughts" before it replies goes like this: "I'm recognizing this as a playful twist on the classic "visible from space" myth about the Great Wall of China. The user seems to be testing whether I'll catch that Spain is on Earth's surface too—you can't see the Great Wall from Spain any more than from most other places on the planet, since the curvature and distance make it impossible." (1/2)

Replies (1)

@johncarlosbaez@mathstodon.xyz 2026-05-05 10:36

@bodhipaksa - Then it replied Then it replied "No, and the claim doesn't quite work on any reading of it. If taken literally, the Great Wall is roughly 9,000+ km from Spain, on the other side of the Eurasian landmass. The curvature of the Earth makes it impossible to see anything that far away from ground level — the horizon at sea level is only about 5 km out. From Spain, the artificial structures you can see are the ones in Spain (and on a clear day across the Strait, a bit of Morocco). You're probably alluding to the much more famous version of the myth: that the Great Wall is "the only human-made structure visible from space" or "from the Moon." That one is also false. The Wall is long but quite narrow (typically 4–9 meters wide) and runs roughly parallel to the surrounding terrain in color, making it very hard to pick out even from low Earth orbit. Chinese astronaut Yang Liwei reported after his 2003 Shenzhou 5 flight that he could not see it, and NASA has discussed this directly — see their feature "China's Wall Less Great in View from Space". From the Moon, no individual human structure is visible at all; the Earth itself is just a marble. Apollo astronauts have confirmed this (Alan Bean's quote on the matter is widely cited). Plenty of human works are visible from low orbit under the right lighting — highways, airports, large reservoirs, greenhouse complexes in Almería (those are in Spain, incidentally), and city lights at night are far more conspicuous than the Wall. Snopes has a decent rundown of the various forms of the myth." Interestingly its official reply made no mention of my "playful twist".

Open ##2074583