1738: Moon Shapes

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Moon Shapes

Title text: Whenever I see a picture of the moon where the points go more than halfway around, I assume it's being eclipsed by one of those Independence Day ships and interpret the rest of the image in light of that.

Explanation

This explanation may be incomplete or incorrect: Table needs pictures. Title text needs explaining. Needs overall more detail. If you can address this issue, please edit the page! Thanks.

The phases of the moon are created by sunlight reflecting off the moon's surface. This means that the bright side of the moon always needs to be facing towards the sun. However, the moon often appears in works of art in ways that are very dramatic, but violate this rule. This comic lists some of the some common mistakes. In some cases, a depiction may be unrealistic in multiple ways - for example, the Flag of Tunisia has both unrealistic horns and a star visible between the horns, while the Charles VI tarot shows a moon with over-long horns pointing towards the horizon.

Explanation of individual items in the list

Image	Explanation	Example
Full moon	Normal	-
Gibbous moon	Normal	-
Crescent moon with points away from horizon	Normal	-
Crescent moon with points towards horizon	This can only happen when the sun is above the horizon. This isn't necessarily only during a solar eclipse, but since a crescent moon means that the Sun and Moon are relatively close in the sky, it's hard to see at other times.	Van Gogh, Landscape with Couple Walking and Crescent Moon
Crescent-like moon where the black area doesn't touch the poles	The moon is a nearly-perfect sphere, so when it's lit from one side, the dark side will always cover precisely 50% of its surface, and the dark area should begin and end on the moon's axis. If the moon looks like this, the shadows are in the wrong place. This is only possible during a partial solar eclipse, the start of an annular eclipse, or if the Earth is casting an extra shadow on the moon, a lunar eclipse. Randall labels the lunar eclipse "dubious", since the shadow during would be much fuzzier than shown here.	Van Gogh, Starry Night
Crescent-like moon where the horns extend well past the poles	Again, the shadow should just touch the poles. This situation is even harder to create than the previous one - the Earth's shadow is too big to cover the moon but leave an edge like this - a huge Independence Day spaceship (as per the Title text) might be the right size. It does however resemble a partial annular eclipse if you imagine that the black area is the moon covering up the white sun.	Alcoholic Blues
Crescent moon blocking stars	Normal	-
Crescent moon with stars between horns	As the moon is a huge ball, it should block the stars behind it. Many people seem to forget this[1][2]. If stars are visible, there are either one or more holes, or a light-source on the moon. As the Star and Crescent, the image is sometimes considered a symbol of Islam, although it's relatively recent and there's no traditional basis for putting the star between the horns - as originally used on the Flag of Turkey, the star appears in a realistic position.	Edwin Blashfield, Spring Scattering Stars, the Dreamworks logo

Transcript

[Caption above the panel:]

Interpreting the shape of the moon in art

[The left part of the panel shows a two column chart is shown with labels above the columns. The left side shows the moons shape as white on a black square. These types of moons could be seen in certain art pieces. The right side saying whether this is normal or not as indicated with a green check mark or a red X. Right of the second column there are explanations of why the specific type of moon is marked as it is and what it could be called or how it could be possible even with the red X. The upper three moons have one common explanation as indicated with a bracket that covers all three with the text on the middle part of the bracket. Similarly moon five and six also have a bracket and only one explanation.]

Shape Normal?

[Shape #1-3 shows a white circle (full moon), a more than half full moon (Gibbon) and a thin seal at the bottom right of the square.]

✓

✓ "Full" or "Quater" or "Harvest" or "Wax Gibbon" or whatever

✓

[Shape #4 same as #3 but with the seal in the upper part of the square.]

✗ Only possible during a solar eclipse

[Shape #5-6 shows a full moon with a circular section taken out of the right side and a seal that goes almost all the way around the circumference of the moon with almost a full circle taken out of the top left part of the moon.]

✗

✗ Only possible during a lunar eclipse (#1 only, dubious) or a solar eclipse (bright part is the Sun)

[Shape #7 same as #3 but with the seal a little smaller and more to the top and less to the left. Around the moon there are several starts represented with 29 small white dots. In the center of the black square there is a black circle, coinciding with the outer rim of the seal. Within this circle (the dark side of the moon) there are no stars!]

✓ Look OK

[Shape #8 same as #7 but apart from the 29 small white dots from before there are now also 6 more dots inside the dark circle with no stars in #7.]

✗ There's either a hole in the Moon or a nuclear war on its surface.

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Discussion

It's a reflection of the nuclear war on the sun's surface. Mikemk (talk) 08:08, 26 September 2016 (UTC)

I can't find any photoshopped Moon that looks like the last image. Somebody has to make one. --162.158.92.207 13:22, 26 September 2016 (UTC)

Randall uncharacteristically missed an opportunity for pointing out additional errors that people make: It's interesting to note that you can get a decent estimate of the artist's latitude by looking at how they draw a crescent moon. In equatorial cultures, the crescent looks like a cup or a boat - and they interpret it like that. But if you look at most english language children's books, the crescent looks like a letter 'C' or a 'D' with a human face - suggesting that they were probably made in the tradition of northern Europe. When I first moved from the UK (more or less a 'C'-shaped crescent moon) to the southern USA (more like Randall's depiction of the correctly-drawn crescent with the points at a roughly 45 degree angle to the horizon) - I subconsciously felt that the moon "looked wrong" - it was only much later that I understood the reason.

Furthermore, this rotation of the moon relative to the observer also explains why "The man in the moon" is a common trope caused by the pareidolia interpretation of the cratering patterns of the moon in northern cultures. But in southern cultures, people tend to see a rabbit in those full-moon patterns - and that has become the source of many of their stories.

Now that I'm more acutely aware of this - it's interesting to note how many movies get the orientation of the moon wrong for the location that their story is supposedly set in! SteveBaker (talk) 13:41, 26 September 2016 (UTC)

In Japan, for example, the patterns are interpreted as a rabbit making mochi (a sort of dense dumpling made from rice pounded into a powder) on the moon - the Sea of Tranquillity forming the head, and the Sea of Clouds forming part of the pestle in which the rabbit is pounding the rice. 188.114.102.167 (talk) (please sign your comments with ~~~~)

Considering how many movies features the famous Mountains of Illinois, I would be more surprised when they get it right. -- Hkmaly (talk) 13:38, 27 September 2016 (UTC)

Not quite sure how to add this but Gibbon is the author of The Decline and Fall of the Roman Empire - or a type of Ape. It is not a phase of the moon. Also I think the moon depicted is Waning. 141.101.98.113 14:02, 26 September 2016 (UTC)

I think the correct expression is gibbous - "having the illuminated part greater than a semicircle and less than a circle" 141.101.98.68 (talk) (please sign your comments with ~~~~)

Yes, the one he says is correct has me thinking: "OMG, the moon is drunk and has fallen over on its ass." No self-respecting moon lies on its back like that.162.158.114.222 14:17, 26 September 2016 (UTC)

Indeed - but that's pretty much how it looks down here in sunny Texas. It's one of those things you never think about - but once the fact of it clicks in your head, you get this visceral feeling of how you're standing on a large ball rather than a flat plane! Ha! Take that flat-earthers! :-) SteveBaker (talk) 18:46, 26 September 2016 (UTC)

Living in Florida, our crescent moons are almost horizontal. 108.162.212.60

"Wax gibbon" is probably nothing more than a joke on mispronouncing "waxing gibbous". As drawn, it is the way a waning gibbous would appear in the northern hemisphere, but a waxing gibbous in the southern hemisphere. Harperska (talk) 16:18, 26 September 2016 (UTC)

Link to the DreamWorks logo image please? There seem to be multiple versions. 108.162.237.216 15:16, 26 September 2016 (UTC)

I'm surprised Randall missed the chance to include a joke about guys with fishing rods. --162.158.85.141 15:41, 26 September 2016 (UTC)

http://www.roadtovr.com/wp-content/uploads/2014/11/dreamworks-logo.jpg... Here's the link to the Dreamworks logo. You're welcome. --JayRulesXKCD (talk) 16:17, 26 September 2016 (UTC)

neither of the examples for the "stars in the moon" apply here. both randall's examples imply a spherical moon. spring and the dreamworks child are supported on a crescent moon for which only the light section actually exists. better examples, please. --141.101.98.84 12:26, 27 September 2016 (UTC)

While the dreamworks logo features a child sitting on the crescent moon as though the dark portion wasn't there, none of the versions of the logo which contain stars in the sky actually show stars 'inside' the moon's disk, so the logo probably isn't a good example of what Randall is complaining about. See https://www.youtube.com/watch?v=xPpy8mYHQps. Harperska (talk) 17:16, 27 September 2016 (UTC)

The first "wrong" image is also only possible if the bright portion is presumed to be the sun during a solar eclipse, assuming the sky is actually depicted as black. You can only have a crescent moon during a solar eclipse if the solar system suddenly acquired a second sun. Harperska (talk) 16:28, 26 September 2016 (UTC)

Here's a good counter-example: EXAMPLE. The bright dot is actually the ISS transiting the moon - but it certainly looks like an impossibility! SteveBaker (talk) 18:50, 26 September 2016 (UTC)

The article doesn't mention the "nuclear war" joke. Does it need explaining? 141.101.98.49 19:29, 26 September 2016 (UTC)

It does now. WingedCat (talk) 22:24, 27 September 2016 (UTC)

your welcome ;-) NotLock (talk) 22:30, 27 September 2016 (UTC)

I've always wanted to create a story, and have the horns of the moon connect on the other side, so you have a blackbody in front of the moon, in parody of this tendency. Also, interesting how the moon is at different rotations in different locations. I never did see the rabbit in the moon. Now I know why. 108.162.245.74 04:34, 27 September 2016 (UTC)

Some of the examples of "incorrect" moons are kinda questionable - like, how relevant is the position of the moon when there's literally a giant divine skyperson standing on it, grabbing stars and scattering of them? 172.68.35.80 23:09, 26 September 2016 (UTC)

I fixed part of the explanation by mentioning the title text. --JayRulesXKCD (talk) 14:41, 26 September 2016 (UTC)

I think that's enough detail for an explanation, so I removed the "incomplete" bar. --JayRulesXKCD (talk) 14:52, 27 September 2016 (UTC)

Should the table of explanations include the text in the comic? NotLock (talk) 22:30, 27 September 2016 (UTC)

The comic has been updated on xkcd. Randall revised the description of #4. Maybe this should be updated? 108.162.242.135 21:55, 27 September 2016 (UTC)

for trivia doesn't mass bend light so IMHO probably still possible for star light on that position 162.158.163.61 05:07, 28 September 2016 (UTC)

Nope - if a distant star's light were being gravitationally lensed by the moon, then its light would appear adjacent to the moon's disk, not on it. A star's light could only appear to originate on the moon's disk if its light were being lensed by another massive object between the earth and the moon (such as a second moon). Whoop whoop pull up (talk) 17:10, 16 October 2016 (UTC)

For the Dreamworks logo, it seems that the static versions don't sport the stars-through-the-moon problem, but I suspect the animated versions (the ones showing at the beginning of their movies) might and probably do. As it so happens, I'm watching Kung Fu Panda 2 for the first time right now, - the fishing kid is a turtle in this case, LOL! - and I note that this problem isn't present here, though there are no stars at all during the logo, so that might be the only reason why. (Of course, if a kid can sit there fishing, the rest of the moon is clearly absent, why wouldn't we see stars there, LOL!) - NiceGuy1 108.162.218.239 18:40, 28 September 2016 (UTC) I finally signed up! This comment is mine. NiceGuy1 (talk) 11:12, 9 June 2017 (UTC)

I swear to god I've seen an Upside down moon before.... both in the day and at night the cusps were pointed down or towards the horizon heres an example of one https://www.flickr.com/photos/dcysurfer/14631243979 i'm 100% sure this is not fake and that there is no reason why one would use a dslr upsidedown or rotate it in post (this is in the southern hemisphere so that may be why... i also swear that many times i've seen the cusps pointed directly to the side (northern hemisphere) heres a nasa photo http://www.nasa.gov/centers/wallops/news/InOMN.html Needforsuv (talk) 06:57, 3 October 2016 (UTC)

You haven't, at least not at night. The Flickr photo isn't evidence at all -- people often rotate pictures for best effect. 172.68.55.80 15:55, 3 October 2016 (UTC) i swear it was at night. also the nasa photo looks the same...

i'll take a photo of it one day... it could've been dusk/ last light and maybe it was just a touch rotated down without accounting for the slope the user is standing on but its not impossible -- Needforsuv (talk) (please sign your comments with ~~~~)

'If the Moon is in the night sky, the Sun must be somewhere "below" the horizon on the other side of the Earth.' Funny how people still talk as if Earth is the center of the universe. More correct would have been to say something about "Earth's rotation" and stuff. 162.158.83.144 (talk) (please sign your comments with ~~~~)

Not funny at all. There is no concept of 'down' except from the point of view of a person on the Earth.

The moon that does look like the last one is the one in the old Proctor and Gamble logo. https://goo.gl/images/4UE6n6 162.158.10.4 (talk) (please sign your comments with ~~~~)

Phil Plait reads xkcd

Has anyone else noticed the Phil Plait message in the news section (up top) ? In case it changes: "Thank you to Phil Plait for the correction on #4!" Blagae (talk) 20:16, 4 June 2017 (UTC)

UPSIDE down moon PROOF:

[3] 
I took the photos MYSELF Needforsuv (talk) 09:26, 28 March 2018 (UTC)