1921: The Moon and the Great Wall

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The Moon and the Great Wall

Title text: And arguably sunspots, on rare occasions. But even if they count, it takes ideal conditions and you might hurt your eyes.

Explanation

This is a reference to the myth that the Great Wall of China is the only manmade object^{[citation needed]} that can be seen from the Moon (or from space) with the naked eye. Sadly, it cannot. In fact, it's barely visible from the orbit of low satellites.

This comic mocks the myth by conflating it with another saying about the Moon, and how the Moon's craters and valleys are visible to the naked human eye. Indeed, the Moon is the only celestial body for which this is true, as all other bodies (with the potential exception of the Sun, see the title text) can only be seen as tiny points of light by the unaided human eye. There is nothing special about the Great Wall of China in this factoid, though; the Moon’s features can be seen equally well from practically any place on Earth with a view of the Moon.^{[citation needed]}

The title text states that one is sometimes able to see large sunspots if any are present and conditions are ideal. However, looking directly at the sun with the naked eye risks extensive damage to the eye and should NEVER be done. It could, however, be possible to see them when the Sun is seen through a thin cloud cover or maybe at sunset/sunrise. (It's possible to see very large sunspots with solar eclipse glasses or other adequate protection, but that's not unaided human eye.)

Transcript

[Megan is holding her arm up towards Ponytail as they stand atop a large brick wall with merlons along the top. They are standing to the left of a tower with three small windows as well as merlons on the top.]

Megan: Did you know that the moon's craters and plains are the only structures on the surface of a celestial body that can be seen with the naked eye from the Great Wall of China?

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Discussion

https://www.nasa.gov/vision/space/workinginspace/great_wall.html

gives something like an authoritative explanation togeter with photos taken from the ISS.

Summary: the great wall can't really be seen from space. But you may be able to spot its shape if the conditions are right. Such as light from the right direction (see the shadow), or snow accumulating on one side of the wall but not the other.

Jyrki Lahtonen

"The statement in the comic, however, is actually true." - It might be, but the part about the Great Wall in it is somewhat irrelevant - it is equally true also from anywhere else in the world. 162.158.210.88 09:49, 27 November 2017 (UTC)

Yeah it's simply a reversal of the myth. "The Great Wall of China" could be replaced with "anywhere on Earth". But that would be less funny. Jdluk (talk) 10:27, 27 November 2017 (UTC)

The Great Wall is 13,000+ miles long, but only 35 feet wide. It's the narrowness that make it impossible to see from space. If we use thread (approx 1/100th of an inch wide) as an analogue, the GWC can be represent by a piece of thread 732 ft long (1.5 inches equals one mile), viewed from 5.5 feet away (equivalent to the 100 miles "edge of space"), or 1222 ft (22,000 miles geosynchronious orbit) or 2.5 miles (238,855 miles orbit of the moon) JamesCurran (talk) 15:07, 27 November 2017 (UTC)

732 feet long viewed from 5.5 feet away doesn't sound credible. And the "edge of space" is 100 kilometres up, not 100 miles. https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line 198.41.238.40 03:50, 29 November 2017 (UTC)

What part of that don't you find credible? Are you questioning my math? And I guess, the definition of "Edge of Space" has been revised since I first did the calculations when I was in college. JamesCurran (talk) 17:26, 29 November 2017 (UTC)

"The wall is a maximum 9.1 m (29 ft 10 in) wide ... The apparent width of the Great Wall from the Moon is the same as that of a human hair viewed from 3 km (2 mi) away." - Wikipedia. 198.41.238.40 03:59, 29 November 2017 (UTC)

That's simply false. The Great Wall of China is another structure on the surface of a celestial body that can be seen with the naked eye from the Great Wall of China. --172.68.54.34 19:05, 27 November 2017 (UTC)

definition of celestial body: "A natural object which is located OUTSIDE OF EARTH'S ATMOSPHERE, such as the Moon, the Sun, an asteroid, planet, or star."

https://en.wiktionary.org/wiki/celestial_body http://www.dictionary.com/browse/celestial?s=t 172.68.65.168 21:04, 27 November 2017 (UTC)

As opposed to terrestrial body, which is, well, the earth XD 172.68.2.22

Actually, there are four terrestrial bodies in our solar system alone: https://en.wikipedia.org/wiki/Terrestrial_planet https://www.space.com/17028-terrestrial-planets.html 141.101.104.239 15:27, 28 November 2017 (UTC)

Could be possibly correct if they were referring to the Celestial Empire (China). Can't tell with mixed case. Probably unlikely.162.158.79.227 03:30, 30 November 2017 (UTC)

Those merlons are way too small. They are not going to protect Megan & Ponytail from incoming arrows. --172.68.54.34 19:08, 27 November 2017 (UTC)

Depends how high the wall is... Perhaps in order to reach the top of the wall archers might need to be so close that the merlons are actually sufficient. NiceGuy1 (talk) 05:19, 28 November 2017 (UTC)

Looking at the pictures on the wiki-page, the merlons are indeed taller than what one would infer from the comic. Obviously the characters are standing on loose stones or crates or something. 141.101.76.22 18:23, 13 December 2017 (UTC)

So the moral of this comic is that Randall doesn't classify cometary tails as celestial bodies? 172.70.110.230 03:30, 22 January 2023 (UTC)

Are they structures, though? (Either of the two tails, from any given comet.) Insofar as sunspots, arguably as structural as anything 'on' the Sun, in terms of plasma/magnetic-field interactions, but tails are particulates/ions set adrift from the solid nucleus that don't really form a body, per se, and practically are uncordinated individual ejecta in a way that (arguably, loosely) the formation of sunspot material is not. But IANAAstrophysicist, and I imagine the definition boundary is even fuzzier than a comet's (or a star's) corona, amongst those experts who study the various phenomena with great intensity! 172.69.79.158 15:33, 22 January 2023 (UTC)

(I meant to add, there are "structures" in nebulae, and even at the scale of galactic superclusters there are signs of something (to appropriate telescopes, at least) described as a "structure". And you might even consider The Milky Way to be a Mk1 Eyeball-visible structure of our home galaxy that is formed of a myriad of stars. But the filaments of gas/dust (at whatever scale), or the tight grouping of not-entirely-just-asterism neighbouring stars, are tied to multiple other node-bodies within the whole, not flailing loose as briefly visible streaming detritus/evaporates as transient and unstructural as a meteor's trail also is. But, again, analogistic and technical terminology might well not entirely agree on a consistent standard.) 172.70.85.200 15:52, 22 January 2023 (UTC)