explain xkcd - User contributions [en]

2651: Air Gap

2022-07-29T20:30:45Z

172.70.114.223: Undo revision 291091 by 172.71.146.97 (talk)

{{comic
| number = 2651
| date = July 27, 2022
| title = Air Gap
| image = air_gap.png
| titletext = You can still do powerline networking, but the bitrate does drop a little depending on the lightbulb warmup and cooldown delay.
}}

==Explanation==
{{incomplete|Created by an AIR GAP-PROTECTED BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This is another one of [[Randall|Randall's]] [[:Category:Tips|Tips]], this time an Energy Tip.

The comic conflates the concepts of computer network security and home electrical power safety to comical effect, resulting in a deeply impractical and ineffective proposed solution. In {{w|computer security}}, {{w|Air_gap_(networking)|air-gapping}} is a measure used to secure sensitive computers or networks of computers by isolating them from the broader internet, since computers are often breached through the internet. {{w|Energy security}} is the concern, typically expressed at a national, rather than domestic, level, with ensuring sufficient affordable and reliable sources of energy to meet demand. It has become an increasingly pressing issue due to the use of energy supplies as a geopolitical tool, exacerbated by the drive to reorient energy generation away from polluting fossil fuels. {{w|Lightning protection}} is a home fire safety practice. {{w|Power analysis}} in computer security is a form of {{w|side-channel attack}} where the attacker observes and/or manipulates the power use by a device for some reason — for example, to gain insight into an otherwise protected process, or to exfiltrate information without having to use a monitored network connection. Power analysis in fire safety means measuring the {{w|power factor}}, volts, and watts of electrical circuits.

[[Randall]] suggests increasing the security of your home power supply by air-gapping it, using the light from a powered lightbulb to power a solar panel which then supplies power to the home, such that there is no physical wired connection between your house and the public electricity network. This is a large and very inefficient version of an {{w|opto-isolator}}, but would protect equipment behind the solar panel from power surges such as lightning strikes (which in an improperly {{w|Ground (electricity)|grounded}} home could blow out the light bulb, but not so easily risk frying the equipment beyond the photovoltaic cell and its inverter). Due to its inefficiency, this approach would waste substantial amounts of energy, and therefore actually worsen problems of energy security.

The title text mentions that a computer can still be connected to the internet via the power supply by using {{w|powerline networking}}, but that the bandwidth would be reduced by the lightbulb's warmup and cooldown delay, which would reduce the signalling rate the lightbulb could accomplish to no more than hundreds of bits per second, if that, for incandescent bulbs. However, as the solar panel cannot emit signals, the unidirectional link would be useless for traditional networking, because essential requests and acknowledgments would be unable to travel from behind the solar panel to the lightbulb. Early {{w|communication satellite}} systems for data networking used high bandwidth unidirectional {{w|downlink}}s paired with low bandwidth ground telephone lines for outbound transmission, but such network configurations remain very uncommon.{{cn}}

Randall's solution is of course a joke. But in reality he could have used {{w|isolation transformer}}s which serve to allow the transfer of power via changing {{w|electromagnetic field}}s without an electrically conductive path. Most transformers, including "wall wart" power adapters, provide this form of isolation and protect devices from noise, voltage transients, most surges, and shock hazard, with fuses and other circuitry. They also limit powerline networking bandwidth by filtering high frequencies.

The look and subject of this comic is reminiscent of the [[:Category:Cursed Connectors|Cursed Connectors]] series. But without the numbered cursed connector in the comic, this is not one of those connectors.

===Why this would be inefficient and impractical===
* Even energy-efficient LED lightbulbs are only about 35% efficient at turning electricity into light, with the rest emitted as heat.
* The air gap is inefficient at passing light from the bulb to the panel, causing some of the light from the lightbulb to be lost to places other than the solar panel, such as to the eye of the observer. A rough guess might be that in the configuration shown less than 60% of light produced will reach the panel, even assuming a perfect reflector.
* Solar panels are generally around 20% efficient at converting light into electricity, with claims at the world record from a single light source at around 40%.

All these efficiency-reducing factors, and others, multiply together. Therefore, only a small fraction of energy would be transmitted between the two ends of the air gap, making the circuit require much more electricity and be much less cost-efficient. (for instance the generous assumptions above lead to 96% of the power being lost)

The solution as illustrated shows a single apparently-normal lightbulb, the highest-powered of which usually draw under 250 watts of power. Given the above efficiency issues, it would provide less than a tenth as much power.

===How this could have a theoretical benefit===
* There are exotic situations where malware on a computer should not be able to communicate with the outside world. Electricity usage is a simple to use side channel which would be made much less practical by such a contraption. The power draw of the lamp would be independent of the power consumption of the device.

==Transcript==
:[A solar panel and a lamp are pictured together, with the lamp pointed at the solar panel, and electronic equipment connected to the solar panel. Lines point outward from the bulb, indicating that it is shining.]
:[Caption below the panel]
:Energy tip: Increase the security of your home power supply by installing an air gap.

{{comic discussion}}

[[Category:Tips]]
[[Category:Computer security]]

2648: Chemicals

2022-07-22T12:18:21Z

172.70.114.223: added this back without reverting everything, although on reread i can see that it could be off-topic. happy to be more accepting of removals that include commentary or discussion.

{{comic
| number = 2648
| date = July 20, 2022
| title = Chemicals
| image = chemicals.png
| titletext = It's hard to believe, but lots of kids these days ONLY know how to buy prepackaged molecules.
}}

==Explanation==
{{incomplete|Created by BIG ISOMER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this comic, [[Megan]] mentions to [[Cueball]] that their company spends a lot on chemicals for which you can find formulas online. She suggests assembling chemicals from atoms "bought in bulk," holding a sheet of paper with the {{w|empirical formula}} C6H5NO2, which designates [https://pubchem.ncbi.nlm.nih.gov/#query=C6H5NO2 hundreds of compounds] including {{w|nitrobenzene}}, {{w|niacin}}, {{w|isonicotinic acid}}, and {{w|picolinic acid}}, followed by their component elements listed with prices. The ambiguity of chemical formulae is one of the jokes in the comic.

While many expensive chemicals are composed of inexpensive and easily available elements, "assembling" those elements into specific molecules is rarely as simple as Megan implies. That work is the primary purpose of the global chemical industry. In-house {{w|chemical synthesis}} is usually not cost effective, because end users have limited time and are generally unable to leverage the {{w|economies of scale}} inherent in bulk manufacturing by specialist industrial firms.[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2880393/] However, we don't know whether Megan and Cueball work in a laboratory, factory, or some other industrial setting. If they need chemicals in bulk, or only very small quantities, synthesizing them might be cost effective. In any case, producing chemicals from their constituent elements or {{w|Precursor (chemistry)|precursor compound}}s is difficult and time-consuming, usually requires expensive equipment, and is often fraught with peril.[https://www.youtube.com/watch?v=5QwW2owNWgc] {{w|Nitrobenzene}}, one of the C6H5NO2 compounds, is an excellent example because it is explosive and extremely toxic, and its synthesis is highly exothermic, making it one of the most dangerous syntheses in the chemical industry.[https://www.icheme.org/media/10339/xiii-paper-36.pdf] Such issues answer Cueball's question as to why more places don't manufacture their own compounds from atoms. Usually chemicals are derived from precursor chemicals instead of constituent elements. Megan seems to be imagining synthesis as a much simpler process without reactivity, energy release, or hazardous intermediate substances. The characters' naivety also gives rise to the humor of the comic, which could also be seen as relating to DIY lifehacks where the immediate cost savings only make sense if their time and learning investment is ignored.

"Big Molecule" is an [[2130: Industry Nicknames|industry nickname like Big Oil or Big Pharma]], amusing in its own right, and conceivably implying that the chemical industry is conspiring to prevent end users from synthesizing their own compounds. Big Oil and Big Pharma are real industrial nicknames; with "Big Pharma", huge corporations invest in research and then charge immensely high prices for medicines. This became more notable when the coronavirus vaccine was released, with media and commerce being focused on large pharmaceutical manufacturers rather than community labs, where community labs could possibly have distributed vaccines directly to their surrounding communities, and recruited from these communities to aid manufacturing, if supported by their governments and economies. Comparatively, "Big Molecule" is fictitious.

Megan is holding a note that shows how many of the four type of atoms she needs to build one of those she wish to assemble. It seems like the paper lists prices for buying 6 carbon, 5 hydrogen, 1 nitrogen and 2 oxygen atoms. Although the (very small?) prices cannot be read. But the numbers are for certain from the formulae, so the $ sign must refer to the unreadable bit coming after. Also she sums the number of atoms up, to find that she only needs 14, but still with an unreadable price sum to the right of the number of atoms. She thus suggest buying atoms in bulk, which should be even cheaper than buying them individually. However, this is another layer of humor, as you can neither buy individual atoms or get a price for them. Just showing her complete lack of understanding of chemistry.

The title text refers to the fact that older people often complain that "kids these days" don't know how to do things that seemed fundamental to past generations. Randall may have expressed that he dislikes other statements like these in [[2165: Millennials|previous comics]]. It may also refer to the decline of home {{w|chemistry set}}s popular from the late 1700s through the early 1980s that encouraged kids to experiment with basic chemical reactions like generating esters or polymers, or the even older decline in home manufacture of gunpowder as was common in the 1800s. Chemical engineering was more widely practiced during the development of plastics, but far fewer people understand how they are made today. Similarly with automobiles, domesticated crops, and many other technologies that progressed through a period of popular attention but became siloed into industries, corporations, governments, or branches of academia. This is happening now with some software, circuitry, and other technologies, where fewer people know how to build and troubleshoot complex devices and systems. Technology users thus lose their ability to build and repair machines and modify their tools themselves, having to rely on paid services instead.

This comic may have been prompted by recent news that [https://english.elpais.com/science-tech/2022-07-15/for-the-first-time-in-history-we-can-modify-atomic-bonds-in-a-single-molecule.html scientists have found a way to assemble and change atoms in individual molecules] by modifying their bonds.

==Transcript==
:[Megan and Cueball standing next to each other. Megan has her palms raised.]
:Megan: You know how our company spends a lot on expensive chemicals?
:Cueball: Yeah?

:[Zoom in on Megan who is holding piece of paper up in one hand. The paper has a large chemical formula at the top. Below is a list of the atoms needed, with amount and a price tag in dollars but with unreadable amount. There is a sum total at the bottom beneath a line.]
:Megan: Well, I just learned you can look up all of the formulas online!
:Megan: We can just buy the atoms in bulk and assemble them here!
:Paper:
::<big>C6H5NO2</big>
::Carbon 6 $...
::Hydrogen 5 $...
::Nitrogen 1 $...
::Oxygen 2 $...
::Total 14 $...

:[Cueball is now on the left of Megan as she is walking past him to the right holding her arms outstretched with her palms up.]
:Cueball: I wonder why more places don't do that.
:Megan: People have no idea they're getting ripped off by Big Molecule!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Chemistry]]

Talk:2648: Chemicals

2022-07-22T12:10:32Z

172.70.114.223:

I think the site itself is hijacked, since the edits don't show properly.[[Special:Contributions/162.158.48.127|162.158.48.127]] 06:07, 21 July 2022 (UTC)

Does anyone know the significance of nitrobenzen, the compound indicated? Per Wikipedia " The production of nitrobenzene is one of the most dangerous processes conducted in the chemical industry because of the exothermicity of the reaction (ΔH = −117 kJ/mol)" but I wonder if there's something else too.
[[Special:Contributions/108.162.237.221|108.162.237.221]] 20:07, 20 July 2022 (UTC)
: It's almost certainly the exothermic (read: potentially explosive) reaction that he's going for. [[Special:Contributions/172.70.110.207|172.70.110.207]] 20:11, 20 July 2022 (UTC)

: It is also the formula of Niacin, one of the B vitamins (same atoms, different arrangement) Possibly this is the point: the molecular formula is ambiguous, there are several well-known chemicals with this formula, with very different properties [[User:Zeimusu|Zeimusu]] ([[User talk:Zeimusu|talk]]) 20:58, 20 July 2022 (UTC)

I wouldn't know which way to put this, but "make your own molecules" could be parodying the "build your own PC from bits", "compile your own OS distro", "actually cook food from raw ingredients, not packets" or various other supply/consumer things that some people (those who know enough about what they're doing) will actually do, many people (who don't care to know) won't even consider and some (with a little bit of knowledge, but not actually enough) might find the revelation that they ''could'' do some things themselves far more compelling than the valid question of whether they ''should'' just leap in and try to do it (making all kinds of mistakes/reinventing various wheels along the way) without further research. [[Special:Contributions/141.101.99.32|141.101.99.32]] 21:14, 20 July 2022 (UTC)
:There are also a lot of make-your-own-film-developer nerds, which is a little bit closer in that you're using household items to try to recreate the reactions created by otherwise expensive chemicals. [[Special:Contributions/172.70.130.217|172.70.130.217]] 22:37, 20 July 2022 (UTC)
::I never even heard of those. I used to live in a household where there was darkroom equipment, even, so know a little of the process of doing that (more so than academic chemistry lessons) but I'd shy away from trying to substitute like that. If it's a thing, then might be worth linking (when and by who it can be). [[Special:Contributions/172.70.162.155|172.70.162.155]] 10:33, 21 July 2022 (UTC)
: Equally could be parodying fallacious thinking in corporate procurement that says 'if we build system x in-house, we won't have have to pay some supplier loads of money to do it', which ignores that the supplier is likely leveraging economies of scale by developing for multiple clients, and ignores the costs of supporting and maintaining the system. [[Special:Contributions/172.70.85.135|172.70.85.135]] 12:14, 21 July 2022 (UTC)

It would appear we have a vandal on the loose again. [[Special:Contributions/172.70.110.135|172.70.110.135]] 22:42, 20 July 2022 (UTC)

: How exactly do we block these people? [[Special:Contributions/108.162.246.196|108.162.246.196]] 04:05, 21 July 2022 (UTC)

:: Maybe the an option is to find out which Reddit forum they're launching from and get it banned from Reddit. They'll do that if the forum is brigading too much [[Special:Contributions/172.70.130.91|172.70.130.91]]

::: i'm pretty sure the vandals are calling ''us'' redditors and they don't use reddit themselves --[[Special:Contributions/172.69.69.66|172.69.69.66]] 06:58, 21 July 2022 (UTC)

:::: It seems to be typical 4chan terminology. Someone who spent some time being influenced there, or maybe one step removed in their own little chan-wannabe dark cave sitting in some other area of the twilight internet taking most of their prompts from the 'real rebels' who are probably just egging them on for their own meta-amusement, but that the stooge(s) would know it. And the repetitious interleving of vandalism modes employed (which are fairly discernible as different until you find the same source has done two or more of the things at once, unifying their identity) indicate a singular whim, if not a singular actor to perform them, who gradually has added new variations to the repertoir of damage to try to be 'clever'. If anything, it just shows how limited they are. [[Special:Contributions/172.70.162.155|172.70.162.155]] 10:33, 21 July 2022 (UTC)

: Request for the wiki: require special permissions to post an image that isn't from xkcd.com, and auto-ban any IP that spams racial slurs. [[User:Thecat|Thecat]] ([[User talk:Thecat|talk]]) 04:48, 21 July 2022 (UTC)

WHAT HAPPENED?!

: undo wasn't working apparently so someone undid the vandalism by blanking the page entirely instead of just manually opening an earlier version and restoring the source from there? i don't get it either --[[Special:Contributions/172.69.69.66|172.69.69.66]] 06:58, 21 July 2022 (UTC)

:: It's 2 AM and 110 where I live, and most of my computer usage is accounting software. I'm not very smart at wiki stuff. Sorry [[Special:Contributions/172.70.130.217|172.70.130.217]] 07:05, 21 July 2022 (UTC)

<s>I wonder if we should mention the economic difference between small quantities of chemicals typically used in laboratory experiments compared to bulk quantities for industrial manufacturing. The latter often ''is'' cost-effective to do in-house, and the current version of the explanation doesn't make that clear at all. We have no idea if Megan and Cueball work in a lab or a factory! [[Special:Contributions/172.69.33.229|172.69.33.229]] 00:37, 21 July 2022 (UTC)</s> Resolved. [[Special:Contributions/172.70.210.233|172.70.210.233]] 00:44, 21 July 2022 (UTC)

https://www.explainxkcd.com/wiki/index.php/Special:Contributions/108.162.246.196 Seems to be the vandal's IP for doing more than just clicking the undo button, as it also vandalized a few talk pages. Almost everything that looks like typing it wasn't fully automated came from that IP[[Special:Contributions/172.70.178.103|172.70.178.103]] 07:41, 21 July 2022 (UTC)
:Not sure it will make any difference but I blocked the IP for three days. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:08, 21 July 2022 (UTC)

I have semi protected this page for one day. Have not so much knowledge about how it worked. But set up so only auto confirmed users can edit this page. This was requested in the admin portal... --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:07, 21 July 2022 (UTC)

;(RESOLVED) Edit request
:The link that says, "more than a hundred compounds and ions" should be, "hundreds of compounds" -- that was my fault because I got the original URL wrong; thanks to whomever fixed it. [[Special:Contributions/172.69.33.177|172.69.33.177]] 08:39, 21 July 2022 (UTC)

I wonder if this could be referencing the video game Spacechem? The premise is exactly this, of chemical engineering using individual atoms to form desired chemicals, and it's the type of nerdy game Randall might enjoy - or at least have heard of. -- [[Special:Contributions/162.158.162.113|162.158.162.113]] 09:54, 21 July 2022 (UTC)

I removed "Similar to the makerspace movement, community chemical labs have been cropping up, where people work together to perform chemical synthesis and other chemistry acts by sharing community resources," because it doesn't seem to be true; see [https://peer.asee.org/the-design-and-impact-of-a-combined-makerspace-wet-lab-and-instructional-design-studio-for-chemical-engineering-curriculum.pdf]. Maybe someone can think of something similar but less misleading from that paper? [[Special:Contributions/172.69.33.123|172.69.33.123]] 11:52, 22 July 2022 (UTC)
: I actually was a very fringe part of a group synthesizing coronavirus tests at a community lab, and have elesewhere participated in groups with community labs. I have some neurological issues and have not yet found a citation or reviewed your reference, but the statement is indeed very true. [[Special:Contributions/172.70.110.135|172.70.110.135]] 12:04, 22 July 2022 (UTC)
: From your link: "In this work I describe the design and impacts of a makerspace at the University of Utah, created specifically for chemical engineering curriculum." -- is your concern the phrasing "cropping up", that the statement implies more labs here than your experience is that there actually are? [[Special:Contributions/172.70.114.223|172.70.114.223]] 12:10, 22 July 2022 (UTC)

2646: Minkowski Space

2022-07-17T03:35:32Z

172.70.114.223: /* Explanation */

{{comic
| number = 2646
| date = July 15, 2022
| title = Minkowski Space
| image = minkowski_space.png
| titletext = My liege, we were able to follow the ship into Minkowski space, but now they've jumped to Hilbert space and they could honestly be anywhere.
}}

==Explanation==
{{incomplete|Created by A RELATIVISTIC QUANTUM STATE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In science fiction, {{w|faster than light travel}}, an impossibility in our universe, is often portrayed by having spaceships enter (or "jump") into some different realm, termed "hyperspace" or similar {{w|technobabble}}, where superluminal travel can occur prior returning to the ordinary universe. In this comic, a spaceship is being chased by an enemy ship. The crew attempt to escape by jumping into {{w|Minkowski space}} which is actually just conventional 3-D space together with time combined into a mathematical object called a {{w|manifold}} used in {{w|special relativity}}. Because Minkowski space is merely a representation of real physical {{w|spacetime}}, "jumping" into it is meaningless and offers no benefit for escaping pursuit, providing the humor of the comic's absurdist joke.

The visual depiction of the spaceships skewed diagonally is based on the graphical {{w|Minkowski diagram}} representation of objects in Minkowski space, where the {{w|world line}} of matter is bounded inside its diagonal {{w|light cone}}.

The mention of distance depending on the observer's frame of reference refers to distances changing when measured in different {{w|inertial frame of reference|inertial frames of reference}}, a concept called the {{w|relativity of simultaneity}}. Here are [https://www.youtube.com/watch?v=asW78vToNLQ some videos] intended [https://www.youtube.com/watch?v=Xrqj88zQZJg to explain] that concept. The skewing depicted changes the distance between the spaceships in such a way that the tip of the pursuer comes closer to the pursued spaceship, but their centers move further apart. So the question of whether they have come closer is indeterminate for the reader of the comic.

The title text is a status report from someone in the pursuing spaceship to their leader (whom they call "my {{w|Homage (feudal)|liege}}.") They tell their superior that following the spaceship to Minkowski space was not a problem, implying (as with fictional hyperspace examples) that they also chose to shift themselves into this other form of perspective. But they cannot now find them after the persued ship subsequently jumped to Hilbert space, as they could now be anywhere. As in the [[2577:_Sea_Chase|Sea Chase]] comic, there was also more than one type of space to jump to here.

Whereas trying to hide in Minkowski space failed, it turned out that hiding in {{w|Hilbert space}} is much easier. This is because of the potential of Hilbert spaces to have an infinite number of dimensions, and thus are clearly much more complicated than four-dimensional Minkowski space. However, Hilbert space is a mathematical construct used to describe objects such as functions of various parameters and complexity, not physical spatiotemporal reality, so it would be very unusual for a physical object to be represented in Hilbert space. Quantum states can be represented as vectors in Hilbert spaces, so it might relate to the {{w|uncertainty principle}} concerning how the escaped spaceship could be anywhere.

==Transcript==
:[A spaceship is being pursued by another spaceship. Both ships have a black part in the front representing a window. They are the same size but different designs. The pursued spaceship to the right has two engines below and a big engine behind. The pursuing spaceship to the left has a V-shaped rear end, and what seems like two weapons on either side pointing forward. At least two persons inside the pursued spaceship are talking to each other, and their text comes out from two starburst on top and bottom of the spaceship.]
:Voice 1: The enemy ship is right behind us!
:Voice 2: Prepare to jump to Minkowski space on my mark.

:[Same setting, with star burst above only. The sound coming from the pursued spaceship is written inside a burst of small lines below the spaceship. Voice 2, by context, is the same as in panel 1.]
:Voice 2: Three... two... one... ''mark!''
:Click

:[Both spaceship are tilted upwards and becomes distorted so they become longer and thinner.]

:[The tilting increases and the distortion is now so pronounced that the spaceships are almost unrecognizable, almost just lines with structure. The distance between the tip of the pursuing spaceship and the pursued becomes shorter in the last two panels, but the distance between their center parts becomes larger. Up to three distinct voices are shown, here, which may include those seen in Panel 1 but with no clear relation.]
:Voice 3: Are they still getting closer?
:Voice 4: I can't tell.
:Voice 5: I think it depends on your frame of reference.

{{comic discussion}}

[[Category:Space]]
[[Category:Math]]
[[Category:Physics]]

2644: fMRI Billboard

2022-07-12T03:09:34Z

172.70.114.223: Transcript written

{{comic
| number = 2644
| date = July 11, 2022
| title = fMRI Billboard
| image = fmri_billboard.png
| titletext = [other side] If the first word of an instruction you're given starts with the same letter as your crush's name, for that step imagine the experimenter is your crush.
}}

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

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
(A giant billboard rises over what appears to be a college campus. It reads: /!\ Student fMRI volunteers /!\ if you see a slide similar to one they already showed you, think as hard as you can about your scariest memory.)

The image is subtitled: A rival neuroscience department keeps trying to sabotage our experiments.
{{comic discussion}}
[[Category: Science]]
[[Category: Psychology]]
[[Category: Biology]]

Talk:2643: Cosmologist Gift

2022-07-10T14:48:44Z

172.70.114.223:

- The explanation mentions “Eight zeptograms” although Randall’s box says “4 zeptograms of dark matter.”

- The 4,800 daltons in the explanation is roughly the size of a small protein; for example, insulin is about 5,800 daltons.

- Randall’s box says it contains 4 zeptograms of dark matter. Could someone explain this? My incomplete (biologist’s) understanding of dark matter is that astrophysicists do not yet know what it is. So how could Randall claim the box contains 4 zeptograms of it?

Thanks!

:Fixed; thank you. [[Special:Contributions/172.70.210.125|172.70.210.125]] 01:18, 9 July 2022 (UTC)

[https://arxiv.org/abs/2204.09143 Here's] a more recent PBH DM source than those already cited which could comport with Randall's 0.4% DM particles implication, but doesn't do so explicitly. [[Special:Contributions/172.70.206.213|172.70.206.213]] 02:35, 9 July 2022 (UTC)
:With the math corrected per 162.158.134.89 below, the figure is 34% ubiquitous particles. [[Special:Contributions/172.70.211.36|172.70.211.36]] 09:44, 9 July 2022 (UTC)

And this comic was the perfect birthday gift for me. [[Special:Contributions/108.162.245.203|108.162.245.203]] 02:42, 9 July 2022 (UTC)

* How was the 23,000 neutrinos/m³ figure obtained? A flux of 7e10/(s·cm²), or 7e14/(s·m²), at a speed of close to 3e8 m/s, gives 2.3e6/m³. That would correspond to a box size of about 0.013 m³, or a bit larger than a typical shoe box. [[Special:Contributions/162.158.134.89|162.158.134.89]] 07:19, 9 July 2022 (UTC)
::Corrected. [[Special:Contributions/172.70.211.52|172.70.211.52]] 09:40, 9 July 2022 (UTC)

To note {and I've summarised in an edit) that photons from the Sun can have been travelling for 100,000 years from its core to space, before their 8ish minute trip to the box (assuming you let them in, e.g. leave the lid off, or filter out all but the hard X-rays/etc), whilst neutrinos hardly notice so are 8 or 9 minutes old (before being adjusted for time dilation) regardless. And you can still put as much lead-lined wrapping paper on your present as you want, to keep it a surprise! [[Special:Contributions/172.69.79.211|172.69.79.211]] 14:45, 9 July 2022 (UTC)
:I saw your very interesting source was from 1997 and mostly about neutrino cycles -- which surprisingly match the menstrual cycle better than the orbit of the moon does -- but not mostly about energy migration out of the sun. It looks like the sun actually has multiple layers that engage in different forms of energy transformation. I added a link to the radiative zone (where gamma rays spend 171 thousand years colliding with matter, getting longer wavelength at each collision, until they leave) but somebody should probably learn about all the different zones at some point and make sure the text is correct. I never knew the sun was so complex! I partly imagine high-energy ancient civilizations somewhere deep inside, having their own forms of night and day and seasons. [[Special:Contributions/162.158.62.23|162.158.62.23]] 14:44, 10 July 2022 (UTC)

446: In Popular Culture

2022-07-09T18:00:17Z

172.70.114.223: /* Explanation */

{{comic
| number = 446
| date = July 7, 2008
| title = In Popular Culture
| image = in_popular_culture.png
| titletext = Someday, the 'in popular culture' section will have its own article with an 'in popular culture' section. It will reference this title-text referencing it, and the blogosphere will implode.
}}

==Explanation==
{{w|Wikipedia}} is a popular online encyclopedia with articles that are created and edited by the general public{{Citation needed}}. Wikipedia entries have many sections, with the first few explaining the general concept and details behind the subject.

When this comic was written, many Wikipedia articles had a section at the end entitled "in popular culture," listing TV shows, movies, songs, and so on that made reference to the subject at hand. In many cases, this list was extensive, possibly because the people editing the articles were such fans of the subject or the pop culture in which it is referenced. They couldn't help but go into great detail, listing many esoteric and seemingly irrelevant elements of pop culture that were peripherally related to the subject of the article. As an example, see the old article [https://en.wikipedia.org/w/index.php?title=Apollo_in_popular_culture&oldid=153446837 Apollo in popular culture], which as of August 2007 redirects to {{w|Apollo}}. This comic caused a lot of vandalism adding an "In popular culture" section to the {{w|wood}} page.

The joke in this case is that even such a mundane article such as one on {{w|wood}} could have an "in popular culture" section, and, obviously, wooden items are common enough that there are any number of instances of popular culture that could be considered to "reference it," even if that's something as basic as a wooden item being used as a prop in a TV show. Such information would be of little or no use to anybody, and only somebody obsessed with wood, a particular element of pop culture in which wood makes an appearance, or the concept of placing pop culture references in encyclopedia articles would bother to create or maintain such a section.

Also, wood being such a popular material, the list of references could be virtually endless. This is a reference to the fact that the "in popular culture" sections of many Wikipedia articles contained dozens of items, even for articles on fairly arcane subjects. Note that the end of this particular "in popular culture" section is not visible, so we don't know how long it is.

The title text states that in the future, there will even have to be a wiki page with the subject "In popular culture." This article will also need an "in popular culture" section, and it will be obvious to make a reference directly to this title text, as xkcd is part of popular culture and because this title text predicted the creation of and a need for such a page. However, this would then create a circular reference. This could be considered a form of infinite loop, which is one way to cause a computer to crash (lock up). The joke is that the blogosphere could follow this endless train of circular links and itself crash, causing an "implosion."

This comic ''was'' actually mentioned in {{w|Wikipedia:"In popular culture" content}} (however, the blogosphere did not implode){{citation needed}}. However, on April 23, 2014, the reference was edited out, although it was added back in May 2015. It has also been added under the external links section of {{w|Wikipedia:xkcd in popular culture}}.

==Transcript==
:[A fictional screen capture of the Wikipedia article for "wood" is shown. There is a picture of wooden boards labeled "wooden boards."]
:'''Wood''' is a hard, fibrous tissue found in many plants. It has been used for centuries for both fuel and as a construction material for... [cut in page.]

:In popular culture:
:In episode 6 of ''Firefly'', "''Our Mrs. Reynolds''," Jayne is given a wooden rain stick by a villager.
:In the Buffyverse, Buffy often slays Vampires using stakes made of wood.
:The wand used by Harry Potter is made of wood from a holly tree.
:The fence around the back yard of the house in ''The Simpsons'' is wooden.
:In the 2004 TV series ''Battlestar Galactica'' [rest of page is cut.]

{{comic discussion}}

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[[Category:Fiction]]
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