explain xkcd - User contributions [en]

2993: Ingredients

2024-10-04T02:36:31Z

172.69.195.112: /* Explanation */ darnit

{{comic
| number = 2993
| date = October 2, 2024
| title = Ingredients
| image = ingredients_2x.png
| imagesize = 417x473px
| noexpand = true
| titletext = Add main-belt asteroids to taste.
}}

==Explanation==
{{incomplete|Created by a THE FIVE BEST EXPLAINXKCD USERS COMBINED INTO ONE - Table of each moons with its special ingredients as well as the volume and surface area, and compare the combined volume and combined surface area to that of Mars (also check both the actual surface area of the five as well as the surface area of a sphere with the total moons volume, which would be a much smaller surface area than of the five moons sum of surface area... Do NOT delete this tag too soon.}}

This comic jokes that it is possible (and perhaps intended) to use the five largest moons in the outer solar system (the {{w|Galilean moons}} and {{w|Titan (moon)|Titan}}) as ingredients to create a “better” planet that has the “coolest features”. Apparently, though, Randall couldn't actually think of anything cool that {{w|Ganymede (moon)|Ganymede}} and {{w|Callisto (moon)|Callisto}} could contribute, so these have just been used as 'filler'. (Though Ganymede has a magnetic field, which is kind of cool...)

Note that {{w|Moon|Earth's moon}} is the fifth-largest moon of the solar system overall ({{w|Europa (moon)|Europa}} is the sixth), so it would have been included had "outer solar system" not been specified.

{| class=wikitable
! scope="col" | Name of Moon
! Scope=“col” | Ingredient
! scope="col" | Volume (km3)
! Scope=“col” | Surface Area (km2)
! scope="col" | Mass (kg)
|-
| Io || Sulfur || 2.53×1010 || 4.17×107 || 0.894×1023
|-
| Europa || Oceans || 1.59×1010 || 3.09×107 || 0.480×1023
|-
| Titan || Hydrocarbons || 7.16×1010 || 8.33×107 || 1.345×1023
|-
| Ganymede || Filler || 7.66×1010 || 8.72×107 || 1.482×1023
|-
| Callisto || Filler || 5.87×1010 || 7.30×107 || 1.076×1023
|-
|}

If all of these moons were lumped together, the total volume of “Randall's planet” would be 2.48×1011 km3, assuming no further material compaction, with a surface area of 1.91×108 km2. This is about 1½ times the volume of Mars, or roughly a 15% larger diameter. The combined mass, however, is smaller than that of Mars.

The title text takes it further, treating asteroids as a “to-taste” ingredient in this “recipe”, treating it more like preparing a food dish rather than making a new {{w|Mars}}-sized planet.

There are a number of science fiction works that posit that advanced alien civilizations left puzzles in the solar system for future humans to solve. Examples for this trope would be {{w|Pushing Ice}} by Alastair Reynolds or {{w|Rogue Moon}} by Algis Budrys. The Arthur C. Clarke stories {{w|The Sentinel (short story)|The Sentinel}}, {{w|Encounter in the Dawn}} (and the more well-known {{w|2001: A Space Odyssey (novel)|book}} and {{w|2001: A Space Odyssey|film}} treatments that together they later helped inspire) each feature various different partial treatments of this concept.

==Transcript==
:[A planet is shown with several different features like oceans and large lakes as well as and craters. It seems like the continent is fused together from five different segments, with cracks between where there is either ocean or rivers. There are four labels above the planet with lines going down to different areas of the planet, but not necessarily pointing to any particular part on the surface, but rather to the entire planet:]
:Sulfur chemistry from Io
:Cool oceans from Europa
:Hydrocarbons from Titan
:Ganymede and Callisto (filler)

:[Caption beneath the panel:]
:Scientists now think the five biggest outer solar system moons are actually just ingredients; we're supposed to combine them to create a single Mars-sized planet that's cooler than any of them.

{{comic discussion}}

[[Category:Space]]
[[Category:Food]]

2883: Astronaut Guests

2024-01-24T09:59:37Z

172.69.195.112:

{{comic
| number = 2883
| date = January 19, 2024
| title = Astronaut Guests
| image = astronaut guests 2x.png
| imagesize = 331x391px
| noexpand = true
| titletext = They didn't bring us a gift, but considering the kinetic energy of a bottle of wine at orbital speed, that's probably for the best.
}}

==Explanation==
{{incomplete|Created by ELEVEN RUSSIAN ASTRONAUTS OVER YOUR HEAD RIGHT NOW DESTROYING USA - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this comic, [[Cueball]], [[Megan]], [[Ponytail]], and [[Hairbun]] can all be seen eating dinner together. Presumably, Ponytail and Hairbun were invited over for dinner, as, to impress them, [[Cueball]] misleadingly claims that they previously "had six {{w|astronaut}}s over for dinner." Normally, this would be interpreted as the astronauts being friends with the hosts (which confers social prestige), going inside their house, and eating. As it turns out, the astronauts only briefly passed overhead while in {{w|orbit}}, and, by chance, this happened during dinnertime. This is a pun on the word "over", as the personnel of the {{w|International Space Station}} are overhead when it passes above you; yet they did not go "over ''to'' someone's house" in the sense that English speakers would usually assume.

Cueball may also be considering the property lines to extend up indefinitely (just like in "What If?" article "{{what if|161|Star Ownership}}"), causing the astronauts to [[1475: Technically|technically]] be at their house despite being hundreds of miles away, vertically.

The astronauts in question were presumably occupying the International Space Station, which has an orbital period of between 90 and 93 minutes (depending on its altitude) or 5400 to 5580 seconds.[https://eol.jsc.nasa.gov/Tools/orbitTutorial.htm] If the astronauts were "over" for 7½ milliseconds, that would be somewhere between 1.34x10⁻⁶ and 1.39x10⁻⁶ of an orbit. Earth's circumference (at the equator) being approximately 40,000 kilometres (24,850 miles), the station was apparently "over" for a ground distance of between 53.9 m and 55.7 m (177 to 183 feet). That would imply quite a large property, but may also consider the astronauts' locations within the ISS, which is 109 m (356 feet) long. (The effect of [[1276: Angular Size|angular size]] is small in this case because the ISS's elevation is small compared to the radius of the Earth. The route traced by the ISS in orbit is only slightly larger than its projection at ground level.)

The caption makes Cueball's statement even less impressive, alleging that statements like it are correct in many places. This would make it uninteresting as a {{w|coincidence}}. It can only happen for latitudes of less than 51.64° north or south, which is as far as the orbital inclination of the ISS takes it, leaving almost 21.6% of the Earth's surface never directly "over"ed. Nonetheless, these areas of the globe will be, overall, significantly more sparsely populated than those that are "over"ed, meaning that the claim could be made in much more than 88.4% of places, assuming that by "places" we mean "properties where people are likely to be having dinner".

The title text suggests that Cueball didn't want a gift (a bottle of wine) from the astronauts. The kinetic energy of a 1.2 kg (full) bottle of wine travelling at the linear velocity of the International Space Station (8000 m/s) is on the order of [https://www.wolframalpha.com/input?i=1%2F2*%288km%2Fs%29%5E2*1.2kg 40 megajoules]. The gravitational potential energy of that mass on the Earth's surface (equatorial radius of 6,378 km) is 75.08 MJ, and its gravitational potential energy at an elevation of 408 km is 70.56 MJ, a difference of 4.52 MJ[https://physics.icalculator.com/gravitational-potential-energy-physics-calculator.html], and that would be converted to kinetic energy if it were to fall. For comparison, the kinetic energy of a fully loaded semi-truck (max legal weight 80,000 pounds or ~36 tonnes) at 70mph (110km/h; a typical highway speed limit for passenger cars) is around [https://www.wolframalpha.com/input?i=1%2F2*%28110km%2Fh%29%5E2*80000+pounds 17 megajoules]. A bottle with more than 2½ times the kinetic energy of that would be hard to keep on the table, and would likely do damage to people or things that tried to keep it there. {{Citation needed}} However, this would assume that the bottle somehow survives its descent through the Earth's atmosphere intact, which seems unlikely.

This comic was posted the same day as the American release of a film set on the ISS (conveniently named ''{{w|I.S.S. (film)|I.S.S.}}''), and just a day after the latest flight to the station by a {{w|Axiom Mission 3|Crew Dragon flight}} had temporarily increased the occupants from the normal seven residents to eleven.

==Transcript==
:[Cueball, Megan, Ponytail, and Hairbun are eating around a table. Cueball is leaning on the back of his chair and has his palm out.]
:Cueball: We don't have houseguests often, but we once had six astronauts over for dinner.
:Hairbun: Oh, wow!
:Cueball (muttering): ''…for 7½ milliseconds in mid-August 2012.''

:[Caption below the panel:]
: If you spend enough time looking at orbital records and property lines, you can make this claim in a lot of places.

{{comic discussion}}
[[Category: Comics featuring Cueball]]
[[Category: Comics featuring Ponytail]]
[[Category: Comics featuring Megan]]
[[Category: Comics featuring Hairbun]]
[[Category: Space]]

Talk:928: Mimic Octopus

2024-01-12T04:43:30Z

172.69.195.112: Added comment on possible identification of unknown silhouette.

How does the mimic octopus manage to mimic multiple fish? Does it split it's own body up or something? '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 13:30, 8 January 2013 (UTC)
:"When under attack, some octopuses can perform arm autotomy, in a similar manner to the way skinks and other lizards detach their tails. The crawling arm serves as a distraction to would-be predators. Such severed arms remain sensitive to stimuli and move away from unpleasant sensations.[23]"[http://en.wikipedia.org/wiki/Octopus#Defense] {{unsigned ip|173.245.48.113}}
::Fine, but in the SCUBA diver depiction, would it really need to rip parts out of itself to mimic bubbles? I don't think that that is quite necessary. {{unsigned ip|108.162.241.131}}
:::It could also hypothetically mimic bubbles by *actually blowing bubbles*. (No word on how it does this.) [[Special:Contributions/108.162.216.30|108.162.216.30]] 02:36, 2 January 2016 (UTC)Anon
::::Simple: This is a 2D {{w|Tomography|cut-out}} of the octopus mimicking the fishes or the scuba '''in 3D'''. It assumes a very complex figure, so that in the cut-out we only see the 2D pictures above. {{unsigned ip|162.158.83.144}}
:i always thought it was just a point of humour in the absurdity that a single octopus could mimic a group of fish -- just the same as it is for a rather small creature to mimic a full-size submarine [[User:Eurydice|Eurydice]] ([[User talk:Eurydice|talk]]) 17:37, 31 December 2021 (UTC)

For the record, octopus is from the Greek ὀκτάπους, a compound of ὀκτά (eight) and πούς (foot); πούς is a third declension masculine noun, whose plural is πόδες. Therefore, the etymologically correct plural of octopus should be octopodes, not (as Orson Scott Card suggests) octopoda, since πούς is not a neuter.
:Actually, it would be "octopuses", as it showed up ''after'' the regularization of English plurals to a final -s. As the video in the explanation explains, someone in the Victorian Grammarian Era "realized" it was "Latin" and pluralized it as such. This caught on and still haunts us to this day. "Octopdes" was coined around the same time by a more observant someone, who realized it was actually Greek. Personally, I avoid the whole trichotomy by saying "octopods". Unrelated etymologically, but has the same meaning and is unequivocally regular. Anonymous 08:08, 5 December 2013 (UTC)

Has anyone checked to see if the title text is true? Whether it is or not, this should be added to the description. [[Special:Contributions/108.162.212.18|108.162.212.18]] 11:53, 16 October 2015 (UTC)

What exactly is the pun here? [[Special:Contributions/199.27.133.78|199.27.133.78]] 00:53, 13 July 2016 (UTC)
:I don't know, either!?! "''Too many'' octopuses"??? {{unsigned ip|108.162.237.172}}

I had a very different impression of this comic when I first read it. I had never heard of a mimic octopus, and I assumed that the comic was making fun of calling a food dish "octopus" when it really wasn't. As in, a restaurant might feed you whatever they caught in a net and call it octopus, no matter how absurd it was. And if they ever did catch an octopus, they split it in two. Very cynical, but not nearly as cool. {{unsigned ip|108.162.246.115}}

I believe the third fish silhouette is actually a [https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjo1rua25jSAhWJ1IMKHU3XCUUQFggcMAA&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FGrouper&usg=AFQjCNGCdz2_bYFBDimJvFpFdG8sju4ljw&sig2=2D3silMR1tstIRSBihTGPA grouper], not a tuna. Sorry, Charlie.--[[Special:Contributions/162.158.74.237|162.158.74.237]] 03:26, 18 February 2017 (UTC)

I am not getting the "pun" of two mimic octopuses. Could anyone elaborate a little bit more? I never thought it as a pun, but rather implying that a mimic octopus, or any creature mirroring what it see, can only reveal its natural form by mimicking other mimic octopus. Though I think it makes sense, this is a bit different from other topics in xkcd, so I doubt it. 12:37, 22 August 2017 (UTC)

I agree with the above comment. Where's the "pun"? "Two Mimic Octopuses" doesn't sound like any other phrase. Maybe, at a stretch, "too many octopuses"? Moreover I don't think "… which is the pun of this comic" makes sense in any way. Comics don't all have puns, and comics with puns aren't limited to one. Perhaps it's a typo for "the point of this comic" or something? I'm going to remove that clause in 24 hours unless someone comes up with a convincing justification. [[User:AmbroseChapel|AmbroseChapel]] ([[User talk:AmbroseChapel|talk]]) 02:05, 13 September 2017 (UTC)

I am surprised that nobody mentioned the very similar mock identification charts such as [http://i.imgur.com/4ufx1.jpg this one] or [https://imgur.com/gallery/O5jlE7U that one]. Given the silhoutetted style of Randall's drawing, I'm pretty sure he had one or both in mind. [[Special:Contributions/141.101.105.204|141.101.105.204]] 15:36, 19 October 2017 (UTC)

The (visual) pun is that the one image out of all of them that actually looks like it could be an octopus, is actually not a (single) octopus. See the identification charts in the comment above for similar concept. [[Special:Contributions/172.69.62.148|172.69.62.148]] 20:38, 11 October 2019 (UTC)

Wait, they’re all mimic octopuses?

Always has been.

Is it possible that the second “unknown” figure is a coral grouper? (Link to image examples:(https://reefguide.org/indopac/pixhtml/coralgrouper9.html) It resembles an outline of some smaller examples.