explain xkcd - User contributions [en]

Talk:2552: The Last Molecule

2021-12-12T02:07:07Z

172.70.98.153: circles/spirals

Unsuccessfully tried to search for a match to the image of the chemical compound. Did find this, which is difficult to use on a cellphone: OSRA: Optical Structure Recognition: https://cactus.nci.nih.gov/cgi-bin/osra/index.cgi [[Special:Contributions/172.70.211.172|1 not72.70.211.172]] 07:43, 9 December 2021 (UTC)
:I've tried to search for SMILES of the molecule, but also got nothing: https://pubchem.ncbi.nlm.nih.gov/#query=C1(C2CC(CCC)C(CC)C2(CCCC))C%3DCC(C(%3DCCC(%3DC)CC)C(C)C)%3DC1 [[Special:Contributions/162.158.222.137|162.158.222.137]]
::Let's name it Excacidin ;) [[User:256 256.256.256|256.256.256.256]] ([[User talk:256 256.256.256|talk]]) 07:19, 10 December 2021 (UTC)

I truly don't understand the God part of the current explanation. [[Special:Contributions/172.68.110.121|172.68.110.121]] 07:55, 9 December 2021 (UTC)
:There is an article at [https://www.smithsonianmag.com/smart-news/humans-make-110000th-earths-biomass-180969141/ Smithonian Magazine] that sums it up quite nicely: Of the 550 gigatons of biomass carbon on Earth, animals make up about 2 gigatons, with insects comprising half of that and fish taking up another 0.7 gigatons. Everything else, including mammals, birds, nematodes and mollusks are roughly 0.3 gigatons, with humans weighing in at 0.06 gigatons.
::About half of all known living species on earth are insects. Therefore if there was a god who created all life, it would be reasonable to assume he likes them. [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 08:26, 9 December 2021 (UTC)
::: 1 Ton = 10^3 kg = 1 Mg → 1 gigaton = 1 Pg (note, not pentagram!) --[[User:Slashme|Slashme]] ([[User talk:Slashme|talk]]) 02:27, 10 December 2021 (UTC)

Chemistry. I love chemistry :-) There is a concept called "Chemical Space" that I learned about in school. https://en.wikipedia.org/wiki/Chemical_space may help, in short: Chemical space is a huge but finite space of all possible atom arrangements in molecules. [[Special:Contributions/162.158.91.106|162.158.91.106]] 07:59, 9 December 2021 (UTC)

I've heard the claim, that we know less about our own ocean floor than we do about the surface of Mars several times before. Is there actually a credible source for this and how do we even quantify how much we know about either area? [[User:Bischoff|Bischoff]] ([[User talk:Bischoff|talk]]) 08:26, 9 December 2021 (UTC)
:This essay might shed some light on the question. [[https://www.scientificamerican.com/article/just-how-little-do-we-know-about-the-ocean-floor/ Just How Little Do We Know about the Ocean Floor?]] From a geographical perspective, our maps of the ocean floor are much less detailed than those covering Mars. (5km resolution for ocean floor, 100m resolution for Mars - radar doesn't work underwater). [[Special:Contributions/162.158.107.18|162.158.107.18]] 09:25, 9 December 2021 (UTC)

The current explanation says that there are an infinite number of chemicals. Is that true? Source? Explanation how that is possible?
Obviously the number of possible molecules is huge, but is it actually a literal, mathematical infinite? Given a finite observable universe, with presumably a finite number of atoms in it. There appear to be a finite number of elements which are stable for any appreciable amount of time and capable of forming molecules.
It seems like there might be practical limitations to the size of a molecule, so that you can't keep making bigger and bigger ones just by adding more atoms/subunits?
If you just keep adding carbon atoms to a diamond will you eventually reach a point where forces such as gravitation become a factor and the molecular bonds fail? I can imagine that long chain molecules light years long might reach point where other forces overwhelm the bond strength? [[Special:Contributions/108.162.246.76|108.162.246.76]] 09:10, 9 December 2021 (UTC)
:For obvious reasons, as long as you limit the number of atoms involved the number of possible "molecules" is - in a mathematical sense - finite. (As there is only a finite number of reasonable stable elements.) But already simple things like polymers can bind millions of atoms in a single molecule. Together with the possible variations intrinsic to such polymers a simple "material" like phenolic resin [[https://en.wikipedia.org/wiki/Phenol_formaldehyde_resin]] is a mixture of more different chemical compounds (in a strict sense) than mankind can ever describe. For all practical application this compexity is not relevant, so no one really cares about.
Additionally there is no clear boundary between typical molecules and other types of condensed matter, like crystals. Same applies to biochemistry. Does chemistry include bio-molecules? If yes, the chemistry guy have to include all the gene sequencing in their to-do list.

"how fast does light travel in one direction?" is not a good example for incompleteness in physics, because this question was settled by Michelson and Morley in the 19th century (answer: it travels with the speed of light)
: It's not clear to me either what was meant here - seems out of place.
:We know how fast light travels when it goes somewhere and comes back – that's ''c'' – but we don't know how fast it goes when only traveling in one direction. For example, light going at ''c''/2 in one direction and returning instantaneously in the other would still match our observations. We also can't reliably synchronize clocks over a distance because we'd either have to do it with a speed-of-light delay, or separate two clocks and find that relativity changed the timings. Of course, Occam's razor indicates that a consistent speed is more likely, but that's not proof. [[Special:Contributions/172.70.126.87|172.70.126.87]] 12:42, 9 December 2021 (UTC)
:Observing two points (nominal source and nominal destination) from a third point perpendicularly off the mid-point between thoss two points, at an arbitrary distance, you ought to see if there's slowness or instaneity involved (at least make a comparison between bidirectional traversal). This does not remove a response bias in the signal from either end as sent towards the recorder at the observation point, but as the stand-off is increased it makes both observation paths nearer and nearer to parallel and so significantly removes the quantifiable initial 'sideways bias' that may exist.
:I leave it as an excercise to the reader to produce the reasons why this might not practically work to quash all such 'inbuilt universal asymmetry', but it's a good start! [[Special:Contributions/172.70.90.141|172.70.90.141]] 13:21, 9 December 2021 (UTC)
:I genuinely don't understand the confusion being proposed here; in practice it's trivial to synchronize a single photon emitter with a single photon detector (such as a PMT) and confirm the speed of light across a single path, with no return trip involved. As far as I know there is know precidence in QM to suspect bidirectional travel could be a special case.
:I like Veritasium as much as the next guy, but I don't think that this one is a serious debate like the other examples. If you're going to consider something like this a great unsolved mystery in physics, I'm sure there are countless other questions just like this for almost every topic in physics and not everything can be a great unsolved mystery.[[Special:Contributions/172.70.134.23|172.70.134.23]] 17:37, 9 December 2021 (UTC)

To quote Randall Munroe in https://what-if.xkcd.com/114/, "The whole universe is matter, as far as we can tell. No one is sure why there is more matter than antimatter, since the laws of physics are pretty symmetrical, and there's no reason to expect there to be more of one than the other. Although when it comes down to it, there's no reason to expect anything at all." Antimatter aside, this shows that the laws of the universe are sometimes asymmetrical. I also like the point that "when it comes down to it, there's no reason to expect anything." Why should we expect the speed of light to be symmetrical? There's no real reason to. [[User:Beret|Beret]] ([[User talk:Beret|talk]]) 14:53, 9 December 2021 (UTC)
:On the contrary, without any such thing as the æther (the fundament through which we would be passing) there is no reason to expect the speed of light (in any given frame of reference) to be asymmetrical. Relativistic frame-dragging and other distortions due to (or resulting in!) accelerative forces will act accordingly, but not change ''c'' itself, in proper calculations, as a function to direction. [[Special:Contributions/172.70.86.12|172.70.86.12]] 16:02, 9 December 2021 (UTC)

::https://en.wikipedia.org/wiki/One-way_speed_of_light In any case, the point is that there is no reason to expect light speed to be symmetrical, either. Asymmetry in this case is not due to frame dragging, it would be some fundamental feature of photons or the universe. There is currently no experimental way to test this. [[User:Beret|Beret]] ([[User talk:Beret|talk]]) 17:00, 9 December 2021 (UTC)

Maybe we can cite one of some famous declarations of physicist saying the physics is almost done [https://nautil.us/blog/the-comforting-certainty-of-unanswered-questions (taken from this site)] :

:The British scientist William Cecil Dampier recalled his apprenticeship at Cambridge in the 1890s: “It seemed as though the main framework had been put together once for all, and that little remained to be done but to measure physical constants to the increased accuracy represented by another decimal place.” British physicist J. J. Thomson: “All that was left was to alter a decimal or two in some physical constant.” American physicist Albert A. Michelson: “Our future discoveries must be looked for in the sixth place of decimals.”
:My physics professor from freshman year: "If you're ever in a room with physicists who say that the physics of Earth are done, and there's nothing else left to calculate, ask them "what about turbulence?". You'll be sure to get some dirty looks."[[Special:Contributions/108.162.246.122|108.162.246.122]] 21:08, 9 December 2021 (UTC)
--[[User:Marceluda|Marceluda]] ([[User talk:Marceluda|talk]]) 15:32, 9 December 2021 (UTC)

I'd argue that fusion on earth is an engineering problem, not a matter of physics completeness (yeah, engineering is just applied physics and math just theoretical physics and biology what happens when you close two physicists in a room for too long, but still). Also, the problem of the symmetry of light speed is, from the present understanding of physics, a matter of metaphysics. [[Special:Contributions/172.68.94.143|172.68.94.143]] 13:42, 10 December 2021 (UTC)
:Having worked in fusion research, I'd say it's still a physics problem because we don't yet know if it's physically possible for a burning plasma to be confined for long enough on a small enough scale to create a viable power plant. It's not necessarily just a question of designing the right machine, if you see what I mean. And if it was, I'd like to think we'd find a few hundred billion of dollars of funding and just get it done. IMO the reason it's not a funding priority is that we can't be sure it would work with _any_ amount of money. That said, while it's potentially a question of great value to humanity, I don't think it's significant in terms of the completeness of physics as a field. --[[User:192·168·0·1|192·168·0·1]] ([[User talk:192·168·0·1|talk]]) 15:18, 10 December 2021 (UTC)
:To rant further about fusion funding, we don't know whether we can win any given war either but that doesn't stop us spending trillions of dollars on them. Maybe if we called fusion research "the war on paying for electricity / wrecking the environment" maybe we'd get it sorted. --[[User:192·168·0·1|192·168·0·1]] ([[User talk:192·168·0·1|talk]]) 15:23, 10 December 2021 (UTC)

Regarding the final molecule, using the above mentioned cactus website optical recognition I got: *[C@H](*CC[C@H](C)[C@H](C1CC1C[C@H](CC)CCC)C2[C@H](*)[C@@H]2C)CC3C*(CCC)C(CCC)[C@H]3CCCCC, which isn't recognized as a molecule. Anyone have any better ideas on if there is a similar known molecule? [[User:Stickfigurefan|Stickfigurefan]] ([[User talk:Stickfigurefan|talk]]) 17:16, 10 December 2021 (UTC)

Regarding the completeness of chemistry, I see no reason why a DNA molecule can't be longer than observable universe (it definitely wouldn't collapse into black hole ; obviously, tugging on it would break it somewhere). Regarding the completeness of biology, what organism would such molecule encode? While, mathematically speaking, observable universe is finite, I would consider this idea alone to ensure chemistry and biology can't ever be complete. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 23:35, 10 December 2021 (UTC)

Should we really use "citation needed" for a quotation, where we might actually want a citation? We're only supposed to use that ironically here. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 17:46, 10 December 2021 (UTC)

== Why citation needed? ==

I saw a citation needed about the Higgs Boson. Is it needed for humor? The higgs boson isn't obvious.--[[Special:Contributions/172.70.34.191|172.70.34.191]] 19:14, 10 December 2021 (UTC)

== Circular reasoning ==

I think something could be added about how determining how "complete" is a discipline already requires a complete knowledge of that discipline, even if we limit this to the inappropriate "number of known entities" approach. Some plausible estimates are naturally possible and a historic example seems to be more in line with the current explanation. A good fit seems to be how in physics the proton, neutron and electron model seemed at some point quite complete and was less crowded than the current one, still not sure how much of this understanding is a myth or how to put it in the explanation, so I prefer to leave it to someone else. For biology Wikipedia has {{w|Biological dark matter}} and the more theoretical {{w|Shadow biosphere}}, in case the number of unstudied multicellular organisms isn't sobering enough. [[Special:Contributions/172.70.98.153|172.70.98.153]] 02:07, 12 December 2021 (UTC)

2534: Retractable Rocket

2021-10-28T17:24:18Z

172.70.98.153:

{{comic
| number = 2534
| date = October 27, 2021
| title = Retractable Rocket
| image = retractible_rocket.png
| titletext = Hard to believe that for so many years once they were fully extended we just let them tip over.
}}

==Explanation==
{{incomplete|Created by a RETRACTABLE ROCKET SCIENTIST - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic documents another of [[Beret Guy]]'s [[:Category:Strange powers of Beret Guy|absurdist ventures]]. He explains to [[Megan]] that "we" (possibly [[:Category:Beret Guy's Business|his company]]) are testing their new "retractable" rocket.

{{w|Reusable launch system|Reusable rockets}} are a growing industry, as they are more economically viable in the long run – though technically much more difficult to operate – than rocket boosters that are just discarded after use (which have been standard throughout the majority of space-faring history). Thus, Megan is understandably confused about Beret Guy's assertion that theirs is "retractable", asking if he misspoke. In typical fashion, he assures her that he did not misspeak, with a single "No" without further explanation.

They proceed to watch the rocket "launch", proving that it is indeed ''retractable''. In fact the rocket does not launch, but merely ''extends'' – apparently all the way to the {{w|International Space Station}} (ISS), a height of over 250 miles (over 400 km) – before retracting, as promised, to its original position. The top part, with the astronauts in it, has been left in space. Presumably, it is docked to the ISS, as the crew onboard the ISS say hello to them in panel 4.

Of course, it would not be possible to extend anything this far.{{Citation needed}} The top would be moving very fast compared to the bottom part, and even with the strongest material a fully extended, very thin, presumably, hollow structure with a payload on top would break very soon after extension began. Also, the ISS moves at 17,100 mph (27,600 km/h) compared to the ground under it, making an orbit in about one and a half hour. So making the tip follow this long enough to dock would be even more impossible.

A possibility of making a {{w|space elevator}} has been discussed, but it would not extend like this with a payload on top. Randall has for instance referenced space elevators in [[697: Tensile vs. Shear Strength]].

The title text parodies the 'old' single-use boosters. It appears that the predecessors to the 'retractable rockets' were capable of controlled extension only. Once they had lofted the payload to orbit, they were then allowed to fall over, destroying them in the process so they could not be used again just like booster rockets. However, if a 250 mile/400 km high construction just fell over, it would be much more difficult to avoid other damage, than to the rocket (booster), than for just a few small booster rockets falling out of the sky.{{Citation needed}}

This comic was released four days before (and possibly refers to) SpaceX's {{w|SpaceX Crew-3|Crew-3 mission}} to send astronauts to ISS with a reusable rocket on 31 October 2021.

==Transcript==
:[Beret Guy and Megan is talking. Behind them near the horizon is a tall rocket on a launchpad.]
:Beret Guy: We're testing our new retractable rocket.
:Megan: You mean reusable?
:Beret Guy: No.

:[A zoom in on the launchpad and rocket. It has the appearance of having a long first stage, a second stage with slightly wider fairing and an Apollo-style capsule with escape-tower atop it all. There is a directionless speech-bubble at the top depicting a count down voice.]
:Count down: Three...Two...One...Liftoff!

:[Same view as before, but while the base of the rocket-stack remains stationary, the first stage is apparently elongated, with a hint of a bend to the right, to raise the total height to which the upper-stage and capsule assembly reaches almost to the top of the panel.]

:[In a wider panel, with the base to the left, the first stage is now elongated far enough to disappear off the top of the center of the frame, thus clearly bending to the right. Two peoples voices are indicated as coming from the space capsule far above, as it reaches it destination.]
:Voice 1: Hi, welcome to the ISS!
:Voice 2: Hello!

:[The final panel shows the same view as in the third panel. The first stage is now retracting, and has similar length as in the third panel, but the capsule is no longer atop the 'second stage' fairing. Four movement lines above the top of the retracting rocket indicates that it is returning back to the original position.]

==Trivia==
*The [https://web.archive.org/web/20211028014542/https://xkcd.com/ original comic] misspelled "retractable" as "retractible". Has been documented on the web archive.
**This was done both in the [https://www.explainxkcd.com/wiki/images/archive/5/57/20211028040721%21retractable_rocket.png comic itself], and [https://www.explainxkcd.com/wiki/index.php?title=2534:_Retractible_Rocket&redirect=no the title].
**This was soon corrected, but has left its mark on explain xkcd as can be seen in the links above.

{{comic discussion}}

[[Category:Comics featuring Beret Guy]]
[[Category:Comics featuring Megan]]
[[Category:Beret Guy's Business]]
[[Category:Strange powers of Beret Guy]]
[[Category:Space]]

Talk:44: Love

2021-09-07T22:01:46Z

172.70.98.153:

This comic made me go ''OOF'' and wince. [[User:SilverMagpie|SilverMagpie]] ([[User talk:SilverMagpie|talk]]) 05:29, 14 December 2018 (UTC)

:Now, that's epic. [[Special:Contributions/172.70.98.153|172.70.98.153]] 22:01, 7 September 2021 (UTC)

Talk:673: The Sun

2021-09-02T17:26:35Z

172.70.98.153:

Interesting (or deliberate?) that there's no reference at all in the explanation to [[wikipedia:Sunshine_(2007_film)|Sunshine]], released two years previously. [[Special:Contributions/178.99.247.73|178.99.247.73]] 21:07, 20 May 2013 (UTC)
* I just want to know if Randall knew the film Sunshine existed when he made the comic.

Can't "to spring" be thought of as a physical movement? [[Special:Contributions/108.162.212.196|108.162.212.196]] 00:49, 7 January 2014 (UTC)
: Yes; that's why the mnemonic works. [[User:Zowayix|Zowayix]] ([[User talk:Zowayix|talk]]) 16:08, 15 January 2014 (UTC)
:: Also, the mnemonic works because physically it is relatively easier to spring (i.e., jump) forward and to fall (through the simple action of gravity, without being able to catch yourself with your arms) back(ward) than it is to do the reverse. --[[User:Bedunkel|BD]] ([[User talk:Bedunkel|talk]]) 01:09, 20 November 2014 (UTC)
the fusion reactions are well understood
By whom?

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 22:12, 27 January 2015 (UTC)

Okay, I'm too lazy to figure out a rewrite, but honestly...it seems pretty durned obvious that it's making fun of "The Core" which is actually mentioned in the comic, not making fun of some random British film not mentioned. Also look at the movie poster for "The Core" on Wikipedia; the similarities to the last panel with the group of people and the silhouettes is pretty obvious. [[Special:Contributions/108.162.215.150|108.162.215.150]] 23:11, 12 April 2015 (UTC)MW

I think "not on my watch" is being used as another pun, as daylight savings would not happen on your watch if you couldn't adjust it. [[Special:Contributions/173.245.52.127|173.245.52.127]] 12:19, 28 April 2015 (UTC)

It's not incorrect to say that this comic makes fun of science fiction disaster movies, but that's not right place to start. The comic is really about the fact that there are two ways to interpret the term "daylight saving time", and one of those ways sounds like the over-adrenalized style that one sees in action movie posters. That's the central joke, and the mockery of science fiction disaster movies is there in order to make that joke funny

The statement that "Even in the nearly impossible event of the sun's fusion is failing in the traditional sense, the sun would collapse causing a supernova." is incorrect as the Sun does not have enough mass to fuel a supernova. IIRC it's mass would have to be about 40% higher for that to happen
: Removed it. [[Special:Contributions/162.158.238.236|162.158.238.236]] 02:29, 30 October 2020 (UTC)