explain xkcd - User contributions [en]

Talk:2307: Alive Or Not

2020-05-19T00:28:03Z

162.158.93.27:

I'm pretty sure high-pressure fire hoses belong on this scale[[User:60sRefugee|60sRefugee]] ([[User talk:60sRefugee|talk]]) 21:47, 15 May 2020 (UTC)
:What about wacky waving inflatable tube guy? [[Special:Contributions/172.68.38.124|172.68.38.124]] 00:41, 16 May 2020 (UTC)

Funny, for once viruses are said to be alive. That's new... [[Special:Contributions/141.101.107.138|141.101.107.138]] 22:01, 15 May 2020 (UTC)
:Definitely new, and extremely angering! I could scream... [[Special:Contributions/172.68.143.30|172.68.143.30]] 22:47, 15 May 2020 (UTC)
::Jup. The nex disgusting piece of antiscience after Wednesday´s nonsense about handwashing helping against respirational diseases. I think Monroe has caught a bug from Potus Donald. --[[Special:Contributions/141.101.69.33|141.101.69.33]] 07:44, 16 May 2020 (UTC)
:::There was nothing unscientific about either one. The cold is spread in part by contact--it's why we cough into our elbows, not our hands now--it reduces spread. And whether or not viruses count as alive is debatable, not obviously wrong. They do have genetic material and reproduce, and you can kill them, making them inert in various ways. -->
:::But even if he had been incorrect, comparing someone to some other hated figure for some much smaller slight is just Godwin-lite. And, like the original, it contributes nothing of value to the conversation. In no way does it help determine who is correct. [[User:Trlkly|Trlkly]] ([[User talk:Trlkly|talk]]) 16:49, 18 May 2020 (UTC)

Do we want to bicker over the placement of the line (like "Why is it below viruses"), or the order things are placed in (like "Why are slime molds below plants")? [[User:GreatWyrmGold|GreatWyrmGold]] ([[User talk:GreatWyrmGold|talk]]) 22:06, 15 May 2020 (UTC)
: Oh, go on. If you insist. You go first, unless you already have. ;) [[Special:Contributions/162.158.154.31|162.158.154.31]] 22:46, 15 May 2020 (UTC)
: Seconded, I'm most interested which criterion (even a numeric one, as the diagram is suggestive of) Randall used. [[Special:Contributions/162.158.158.163|162.158.158.163]] 09:43, 16 May 2020 (UTC)

True fossils have remineralised so generally do not have DNA left. They are merely the shadow of a previous life.
: So fossils are closer to "Rocks with Faces," well, for the ancient vertebrate fossils anyway? [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 15:36, 16 May 2020 (UTC)

Surprised no one has noticed the typo yet. It's 'archaea', not 'archea'
:(Sign yourself(/ves), "True fossils" and "Surprised"?) I disagree. It's 'archæa'... [[Special:Contributions/162.158.154.31|162.158.154.31]] 22:46, 15 May 2020 (UTC)

Poor English and a mistake. It should say...
"...discussion about *whether* virus*es* are alive."
Also the (covid for starters) is wrong. Covid19 is the disease caused by the virus (as mentioned in the line above) not the virus itself

I am disappointed that sponges are not mentioned as an example of weird animals. I mean, come on, way weirder than jellyfish. But it is good that viruses get the recognition they deserve.[[User:Jkrstrt|Jkrstrt]] ([[User talk:Jkrstrt|talk]]) 13:34, 16 May 2020 (UTC)

When looking at viruses, I consider them made of the things of life (proteins, lipids, nucleic acids), but are not actually alive as they have no metabolism and can not reproduce on their own; they need to co-opt the protein production facility of truly living cells in order to reproduce. Without a host, they just sit there (or maybe blow around on the wind). Also without metabolism, they can not starve to death, like bacteria and other single-cell organisms that get into the wrong environment. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 15:36, 16 May 2020 (UTC)
:Agreed that the lack of metabolism is a big thing. On the other hand, ''all'' organisms need an acceptable habitat to be able to reproduce, and viruses are no different: their habitat is their target cells, where they can reproduce like mad. Furthermore, viruses can be infected and killed by other viruses, namely by {{w|virophages}}, and it's hard to see how they can be killed if they weren't alive to begin with. Whether they're "alive" depends only on one's definition of the word; it can be interesting to discuss this because it reveals what people think "alive" means, but not because there's a true answer. [[User:DKMell|DKMell]] ([[User talk:DKMell|talk]]) 22:18, 18 May 2020 (UTC)
:: technically, virophages do not directly infect other viruses, they rather co-infect a cell and use the reproduction machinery of the other virus, blocking it at the same time... [[Special:Contributions/162.158.93.27|162.158.93.27]] guest from outer space

Well, this raises the question where the sun (or any main sequence star) fall on this list. Is it just a really big thermonuclear fire?

This is not a COVID-19 comic. Just because it is biology-related, doesn't make it a COVID-19 comic. I have removed it from the category and its mention in the explanation.[[Special:Contributions/172.69.34.38|172.69.34.38]] 07:33, 17 May 2020 (UTC)
:Of course it is. The whole idea about this comic is to spark the discussion if Virus (covid) is alive or not. I put it back. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 21:59, 17 May 2020 (UTC)
::I fully disagree, this comic could have been published in previous years. This is only tangentially related to COVID-19, and is a general discussion about "life". Viruses are only barely mentioned in this comic. [[Special:Contributions/172.69.34.38|172.69.34.38]] 23:26, 17 May 2020 (UTC)
:::Agree it shouldn't be classified as COVID-19, but then there's a bunch of others that should be removed from the category: 2278, 2283, 2289, 2292, 2293.[[Special:Contributions/141.101.107.78|141.101.107.78]] 08:34, 18 May 2020 (UTC)
:::I wouldn't consider this comic about COVID-19, either. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 13:49, 18 May 2020 (UTC)

Somewhat disappointed that he didn't include any fictional items such as golems. For that matter, where to place Alexa? [[User:Cellocgw|Cellocgw]] ([[User talk:Cellocgw|talk]]) 10:51, 18 May 2020 (UTC)

I’m surprised this doesn’t include Schrödinger’s Cat at the origin. [[Special:Contributions/162.158.91.77|162.158.91.77]] 14:53, 18 May 2020 (UTC)

Missed joke opportunity: which type of cloud? because one type of cloud has AI in it..

Why are slime molds below plants and fungi? They actually move.--[[Special:Contributions/172.68.189.241|172.68.189.241]] 17:05, 18 May 2020 (UTC)

Talk:2123: Meta Collecting

2019-03-22T07:44:48Z

162.158.93.27:

RIP {{w|List of collectables}} and grammar. It’s collectable. Not collectible, collectable. [[User:Netherin5|Netherin5]] ([[User talk:Netherin5|talk]]) 16:07, 13 March 2019 (UTC)
:You may disagree, but collectable is also correct. https://en.oxforddictionaries.com/definition/collectable [[Special:Contributions/108.162.242.23|108.162.242.23]] 16:21, 13 March 2019 (UTC)
:I think we’re agreeing here? I also use collectable, and said so in my comment. At least it should be used in this case, because it’s what Wikipedia uses on said page. [[User:Netherin5|Netherin5]] ([[User talk:Netherin5|talk]]) 16:26, 13 March 2019 (UTC)
:My understanding was that the words had different meanings. Something is collectible if it would have a place in a collection; a Harley is collectible because it would have a place in Cueball's collection of items. Something is collectable if it can be collected; a court judgement may be collectable if the person ordered to pay has enough money to make the payment. [[User:D5xtgr|D5xtgr]] ([[User talk:D5xtgr|talk]]) 17:33, 13 March 2019 (UTC)
::Suspiciously enough, that’s the exact example I got when I googled it, but thank you for the collection. I only say this because of the article in question discussed. [[User:Netherin5|Netherin5]] ([[User talk:Netherin5|talk]]) 17:41, 13 March 2019 (UTC)
:::Yes, I was having a hard time wording my original example - it's rather easier to show why a debt or court judgement ''wouldn't'' be collectable than to explain why one ''would'' be. [[User:D5xtgr|D5xtgr]] ([[User talk:D5xtgr|talk]]) 18:54, 13 March 2019 (UTC)
: Googling "collectible define" or "collectable define", we get that both seem to be correct. https://writingexplained.org/collectible-vs-collectable-difference says collectable is typically the British spelling of the word.

First time posting here, so my format might be terrible. But looking at the list of collectables; Maytag is listed, and the reference is for antique scales, so definitely not dryers. [[Special:Contributions/173.245.54.7|173.245.54.7]] 16:13, 13 March 2019 (UTC)
:Antique washer models to scale? Fixed it. On a serious note, it’s just one source, there are probably people who would collect washers, or, the more likely option, they just saw Maytag and thought “washers” EDIT: As a formatting nerd, it’s good. [[User:Netherin5|Netherin5]] ([[User talk:Netherin5|talk]]) 16:20, 13 March 2019 (UTC)

Wikipedia intern: "Mr. Sanger? Randall made a comic about us again." Larry Sanger: "Godammit, what page do we have to lock this time?" [[User:GreatWyrmGold|GreatWyrmGold]] ([[User talk:GreatWyrmGold|talk]]) 04:21, 14 March 2019 (UTC)

I already suggested this [https://www.explainxkcd.com/wiki/index.php/2099:_Missal_of_Silos before] that I think we can have a new collected page of xkcd Wikipedia edit wars. I doubt the trivia in 2099 is the full list, or is it? Are there not that many cases as I think to be worth it? [[Special:Contributions/162.158.118.22|162.158.118.22]] 04:48, 14 March 2019 (UTC)
: Well, [https://en.wikipedia.org/wiki/Xkcd#Wikipedia_vandalism Wikipedia] has the list now, so I'm satisfied. [[Special:Contributions/162.158.118.46|162.158.118.46]] 05:59, 15 March 2019 (UTC)

As of right now, Randall has got his wish: the page is protected. Unfortunately, it's protected with "yachts" on it and, of course, it can't be reverted because of the protection. [[User:Jeremyp|Jeremyp]] ([[User talk:Jeremyp|talk]]) 10:45, 14 March 2019 (UTC)
:On the plus side, old yachts that are no longer seaworthy but still collectable are quite common on craigslist for under $10,000. Even cheaper yet, just ask any marina owner for abandoned sunken yachts you can have just for getting them out of the waterway.[[User:Seebert|Seebert]] ([[User talk:Seebert|talk]]) 13:06, 14 March 2019 (UTC)
:It's gone now. The edit history is quite entertaining though. "Added boating category" [[User:Linker|Linker]] ([[User talk:Linker|talk]]) 17:15, 14 March 2019 (UTC)
::Looks like one of the editors got a bit overzealous and deleted Element Collecting because they thought it was an xkcd reference. [[User:CJB42|CJB42]] ([[User talk:CJB42|talk]]) 05:38, 15 March 2019 (UTC)
:::That sucks. That is such a real hobby though. There is this guy who made a wooden periodic actual table and put elements on it in each of their places. He takes beautiful photos of them.

Interesting choice of username, xkcd2123. {{unsigned|103.22.200.210}}

It is disappointing that xkcd readers think it's funny to vandalize the wikipedia article because of this comic. I highly doubt that Randall himself did so, and I don't think he intended for anyone else to actually vandalize it either. Furthermore, giving these viewers any satisfaction by actually including this info in the comic discussion seems somehow inappropriate. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 13:11, 15 March 2019 (UTC)

:While I agree that Randall probably didn't vandalize it himself I don't think he is naive enough to think no one would after he posted the comic. Also, personally I don't see a big problem with a little harmless editing of a single Wikipedia article. If this was ongoing or involved more consequential edits I'd agree with you.[[Special:Contributions/162.158.93.27|162.158.93.27]] 07:44, 22 March 2019 (UTC)

I think that the second item on the top shelf may be a bottle of perfume.[[User:I prefer qwerty|I prefer qwerty]] ([[User talk:I prefer qwerty|talk]]) 20:49, 17 March 2019 (UTC)

Talk:2113: Physics Suppression

2019-02-19T12:30:01Z

162.158.93.27:

That's how mafia works. [[Special:Contributions/172.69.134.111|172.69.134.111]] 16:51, 18 February 2019 (UTC)
:But White Hat didn't mention anything about a Mafia...? [[Special:Contributions/162.158.74.153|162.158.74.153]] 14:31, 18 February 2019 (UTC)
::No, but to suppress people publishing their results, a body like the mafia would be needed, is what Megan jokes about. And then takes an example (and one more in title text) about annoying results that did not get suppressed. Her example turned out to win a noble prize, the title text was later shown to be an error. But a mafia might have stopped both sets of results to have not been published. Basically proving that you can not suppress such results wether relevant or not. If White Hat's model is not taken serious it is probably because he has no data to back it up. Wild claims demands extraordinary well documentation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 14:53, 18 February 2019 (UTC)
:::A "mafia" isn't the only candiate. "Inquistions" have also worked well for suppression, but (AFAIK) have less of a history of intramural violence. I think the image of a cabal of cloaked physics monks torturing dark energy heretics into recantation would have been striking enough, but RMMV (Randall's Mileage May Vary). [[Special:Contributions/172.69.70.23|172.69.70.23]] 17:12, 18 February 2019 (UTC)
::::if you need to spell out your initialism in full, you may not realize they're intended as shorthand.
:::Another fictional candidate may be "science by political committee" system — sending physicists that contest the "official" and "politically correct" theories and models to "corrective labour camps", where they would be forced to perform physical (sic!) work, until their untimely demise... Oh, wait, that actually happened! (See the fate of [[wikipedia:Nikolai Vavilov|Nikolai Vavilov]]) -- [[Special:Contributions/162.158.93.27|162.158.93.27]] 12:28, 19 February 2019 (UTC)
Dark energy isn't a direct consequence of the cosmological constant. The cosmological constant could potentially have been 0 or even negative. There's nothing that currently implies that it should be a positive number. That's exactly why it is annoying. If general relativity dictated it, people would just praise this as another result showing relativity is true. But since it doesn't, it needs an explanation. [[Special:Contributions/172.68.65.6|172.68.65.6]] 21:16, 18 February 2019 (UTC)

While it could be true that White Hat is ignored because of the lack of supporting data, Albert Einstein was in a similar situation when coming up with his Theory of Relativity. [[User:Mad max|Mad max]] ([[User talk:Mad max|talk]]) 06:56, 19 February 2019 (UTC)

Talk:2113: Physics Suppression

2019-02-19T12:28:52Z

162.158.93.27:

That's how mafia works. [[Special:Contributions/172.69.134.111|172.69.134.111]] 16:51, 18 February 2019 (UTC)
:But White Hat didn't mention anything about a Mafia...? [[Special:Contributions/162.158.74.153|162.158.74.153]] 14:31, 18 February 2019 (UTC)
::No, but to suppress people publishing their results, a body like the mafia would be needed, is what Megan jokes about. And then takes an example (and one more in title text) about annoying results that did not get suppressed. Her example turned out to win a noble prize, the title text was later shown to be an error. But a mafia might have stopped both sets of results to have not been published. Basically proving that you can not suppress such results wether relevant or not. If White Hat's model is not taken serious it is probably because he has no data to back it up. Wild claims demands extraordinary well documentation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 14:53, 18 February 2019 (UTC)
:::A "mafia" isn't the only candiate. "Inquistions" have also worked well for suppression, but (AFAIK) have less of a history of intramural violence. I think the image of a cabal of cloaked physics monks torturing dark energy heretics into recantation would have been striking enough, but RMMV (Randall's Mileage May Vary). [[Special:Contributions/172.69.70.23|172.69.70.23]] 17:12, 18 February 2019 (UTC)
::::if you need to spell out your initialism in full, you may not realize they're intended as shorthand.
:::Another fictional candidate may be "science by political committee" system — sending scientists that contest the "official" and "politically correct" theories and models to "corrective labour camps", where they would be forced to perform physical (sic!) work, until their untimely demise... Oh, wait, that actually happened! (See the fate of [[wikipedia:Nikolai Vavilov|Nikolai Vavilov]]) -- [[Special:Contributions/162.158.93.27|162.158.93.27]] 12:28, 19 February 2019 (UTC)
Dark energy isn't a direct consequence of the cosmological constant. The cosmological constant could potentially have been 0 or even negative. There's nothing that currently implies that it should be a positive number. That's exactly why it is annoying. If general relativity dictated it, people would just praise this as another result showing relativity is true. But since it doesn't, it needs an explanation. [[Special:Contributions/172.68.65.6|172.68.65.6]] 21:16, 18 February 2019 (UTC)

While it could be true that White Hat is ignored because of the lack of supporting data, Albert Einstein was in a similar situation when coming up with his Theory of Relativity. [[User:Mad max|Mad max]] ([[User talk:Mad max|talk]]) 06:56, 19 February 2019 (UTC)

Talk:828: Positive Attitude

2019-02-17T15:10:11Z

162.158.93.27: acks?

What is an IV instrument? It has to be explained. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:58, 30 November 2013 (UTC)

I've rewritten all the explanation, expanding it a bit, adding the title text part and the IV explanation. So I've also removed the incomplete tag. Hope it can be now considered "complete". [[Special:Contributions/173.245.53.117|173.245.53.117]] 02:49, 5 December 2013 (UTC)

I can't believe no one has mentioned the INT, CON and CHR stats on the monitor {{unsigned|CardaStcol}}

Maybe the Cueball on the bed is Megan after chemo (and associated hair loss )?

In related comics there is usually a Megan and Cueball character. Some whould say the personality is a little off to be Megan and fits Cueball better. [[Special:Contributions/162.158.255.117|162.158.255.117]] 18:16, 4 March 2016 (UTC)

Why INT/CON/CHR is listed as a reference to ACKS in particular, rather than to much more venerable D&D it is based on? D&D has the same attributes, except Charisma is abbreviated as CHA, not as CHR. Is it CHR in ACKS? [[Special:Contributions/162.158.93.27|162.158.93.27]] 15:10, 17 February 2019 (UTC)

Talk:603: Idiocracy

2019-02-13T09:20:03Z

162.158.93.27: Explained link of another user concerning reverse Flynn effect.

This explanation seems to be incorrect. The key point was that White Hat actually was wrong! The average education has gone up, and the average IQ ''cannot'' sink! By allowing Cueball to agree with clearly false laments, he baits him into revealing his stupidity. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 19:58, 20 August 2013 (UTC)
:The title text pretty much spells out that, in Randall's mind, White Hat is correct. [[Special:Contributions/199.27.128.66|199.27.128.66]] 06:14, 10 November 2013 (UTC)

I propose that the hatted figure is not in fact [[White_Hat|White Hat]], as neither the hat shape nor the personality are consistent with other appearances. ([[:Category:Comics featuring White Hat‏‎]]) The real White Hat, when he speaks, is generally a bit of a wet blanket or well-meaning buffoon. This one, whom I'll dub [[White_Derby|White Derby]], is speaking counter-buffoonery, what we may reasonably guess to be the actual thoughts of the author. Usually Cueball fills this role (eg [[258:_Conspiracy_Theories]]), and in fact if the roles here were reversed I'd tend to ignore the misshapen hat. But two and two, together, well... --[[Special:Contributions/66.114.70.139|66.114.70.139]] 18:39, 28 October 2013 (UTC)
:Eh. He hasn't appeared in any other strips, and it's not too harmful to put him under the umbrella of the real White Hat. I see your point; White Hat is no longer a generic character like [[Hairy]], but an actual recurring one.
:Also, have Black Hat and White Hat ever appeared in the same comic? (Click and Drag doesn't count.) [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 09:08, 11 November 2013 (UTC)
::White Hat is not this Safari Hat guy and this has been corrected recently. Also recently in [[1708: Dehydration]] White and Black Hat appears together and Black Hat actually reacts in a discussion White Hat has begun. See more under the explanation for [[:Category:Characters with Hats|Characters with Hats]]. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 19:56, 9 September 2016 (UTC)

So, does this page qualify for Complete now? [[Special:Contributions/199.27.128.66|199.27.128.66]] 05:36, 12 November 2013 (UTC)

Sorry Randall. You're wrong here. IQ can change. Just because there is a mean for the IQ of the current population, doesn't mean that average can't shift over time. And if we used to be cavemen then either the IQ did shift, or we've always been this smart, which means we couldn't have evolved.

In this case, IQ is exactly the same as morality. Both shift ever so slightly over time, such that the mean is always the acceptable "norm". You can't feel this shift unless you study it. The difference is that morality exhibits locality, so morality shifts slower or faster depending on the subsection of society. Thus you have people who believe they are more right than others, but no one believes they are outright wrong (as a culture). Proof in the pudding is doing a poll on the population as to how smart they think they are. They always rate themselves such that the mean is shifted 1 or 2 deviations up. Same thing with morality. People all espouse a morality that they think is 1 or 2 deviations greater than the standard, whether they are a religious sect or secularists.

But the short of it, a population mean doesn't imply the mean never changes.[[User:Cflare|Cflare]] ([[User talk:Cflare|talk]]) 21:12, 4 August 2014 (UTC)

:While IQ can change, the way you're explaining it is not the way the Cueball or "White Hat" is explaining it. In fact, "White Hat" never explicitly states that IQ doesn't evolve at all; just not to the depressing trend Cueball here thinks it does. Anonymous 23:04, 20 August 2014 (UTC)

In fact average IQ cannot change. The average IQ of humanity is always 100, because that is the definition of the IQ scale.[[Special:Contributions/108.162.216.129|108.162.216.129]] 01:15, 15 March 2015 (UTC)

"IQ" per se is simply what IQ tests measure. There's no law that says any specific test that purports to be the best measure of IQ is the gold standard. In the US and many (perhaps most) other English-speaking countries, the Wechsler and Stanford-Binet scales are the most popular. The Wechsler Adult Intelligence Scale is the IQ test most commonly used (for adults) by neuropsychologists. It's re-normed every few years (e.g., WAIS-III becomes WAIS-IV, then WAIS-V, etc.). In "re-norming" each question is studied and perhaps refined, some are dropped, and new questions--sometimes entirely new subtests--are added. The method of calculating the IQ is often tweaked as well. Re-norming involves administering versions of the test to thousands of people and using statistics to determine the one to keep. Obviously the same pool of test-takers is not used every time in a process that goes on decade after decade. It's not unusual for test questions to become more difficult and what's considered to be an average score to be a bit higher in the new edition than in the old. This has been interpreted to mean that people are getting more intelligent, but that's not the only possible explanation. (Also, the test is not normed on "humanity" but on a tiny subset of earth's humans.) Oh, and your IQ is not a number carved in stone, so to speak, but a best-guess that falls within the range of scores you'd be expected to earn if (theoretically) you took the same test multiple times.[[User:Npsych|Npsych]] ([[User talk:Npsych|talk]]) 10:20, 2 December 2015 (UTC)

If there is reason for climate change it is almost certainly due to the destruction of trees. Any ridiculous assertions about carbon dioxide can not be confirmed or denied and the political machinations about carbon dioxide stem from Margaret Thatcher's war on the coal miners in Britain.

It would be a simple matter to replant forests. All we would have to do is pay for that in higher latitudes and send in drones to deal with illegal loggers in lower latitudes. 20 years or so should sort out most of the problems.

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 17:03, 29 January 2015 (UTC)

: I see what you did there... This is the bit where you go "Everything I just said was wrong" --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 17:26, 29 January 2015 (UTC)

Elitism is an eminently more desirable trait than stupidity to breed into one's offspring. An elitist might be hated, but he will be *competent*; he will *accomplish things*, while a stupid person will harm themselves and others through their stupidity, often remaining well-liked in spite of being cancerous and toxic to everything nearby. Elitism is the bitter taste of medicine which will make you better; stupidity is the delicious candy to which you will become hopelessly addicted at a formative age, leading to a miserable lifetime of diabetes and an early death by heart failure. I only wish I intended to reproduce, so that I could practice what I preach on this regard. [[Special:Contributions/173.245.54.52|173.245.54.52]] 19:28, 30 October 2015 (UTC)

Changed the text in the first paragraph because the movie never implied that people with lower IQ were more fertile, it clearly stated that they were more likely to reproduce due to lack of education, absence of planning, and general negligence with regards to the consequences of their actions. If you disagree with me on this, go watch the movie again. Or just the first few minutes which explains this in detail. -Pennpenn [[Special:Contributions/108.162.250.162|108.162.250.162]] 05:08, 11 February 2016 (UTC)

So... what else does this explanation need to be considered complete? [[User:Edo|Edo]] ([[User talk:Edo|talk]]) 23:24, 11 February 2016 (UTC)

The explanation of the Dunning-Kruger effect is incorrect, insofar as it tries to apply the effect to intelligence, and mention here may be off topic entirely. The Dunning-Kruger effect is refers to bias in self assessment relative to the norm of low-skilled people in a given field to high skilled people in the same field. Proficiency in a field is not intelligence, nor does the theory allow generalization to intelligent people generally versus those less intelligent generally, irrespective of field, and while there is probably evidence of a correlation between IQ and and proficiency within some collection of fields, the Dunning-Kruger effect would require much stronger evidence to generalize to intelligence for specific proficiency, specifically it would require evidence of a causal, not correlative, (from skill to IQ, and not the reverse) link, and evidence that such link exists not just in general or at average, but that such link occurs in any hypothetical, non-specified area if proficiency. The wiki article that is linked is technically correct but somewhat misleading in use of the term 'cognitive ability,' which is in some contexts used to refer to intelligence, but in context refers to the specific, non-IQ domained, mental practice of effective megacognition and self-assessment, as well as a type of social awareness regarding group standards of passable performance. [[Special:Contributions/162.158.142.100|162.158.142.100]] 22:02, 24 March 2018 (UTC)

https://www.newsweek.com/iq-scores-are-declining-and-researchers-point-school-media-973040[[Special:Contributions/172.69.69.28|172.69.69.28]] 15:24, 5 October 2018 (UTC)
:What's your point? I can link thousands articles as well. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 19:24, 5 October 2018 (UTC)
The point, from the "Flynn effect" wikipedia article : "Research suggests that there is an ongoing reversed Flynn effect, i.e. a decline in IQ scores, in Norway, Denmark, Australia, Britain, the Netherlands, Sweden, Finland, France and German-speaking countries,[4] a development which appears to have started in the 1990s". This kind of nullifies the comic's point.

Talk:2093: Reminders

2019-01-04T09:57:40Z

162.158.93.27:

I added an explanation in which I extended Cueball's reaction from the reminders to Randall himself - I believe this is commonly done for many comics, but please feel free to modify it. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 17:25, 2 January 2019 (UTC)

Relevant SMBC: https://www.smbc-comics.com/comic/gmail [[Special:Contributions/162.158.63.214|162.158.63.214]] 13:33, 3 January 2019 (UTC)

I liked the rewrite of my original explanation but made a few additional changes. I re-added the intro about Cueball using an email client program, and I slightly modified the title text explanation - I don't think it's suggesting you'll end up friendless and alone, just with a level of friends that you can keep up with or who are willing to accept your lack of attention to the details of their lives. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 14:08, 3 January 2019 (UTC)
:Yeah, sorry, I kind of stomped all over your original write-up :) I felt it read a bit too much like the transcript and needed more explanation than description. I agree with your updates. [[User:Hawthorn|Hawthorn]] ([[User talk:Hawthorn|talk]]) 16:54, 3 January 2019 (UTC)
::No problem - it was just a starting point. [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 19:31, 3 January 2019 (UTC)

Is there a real email client capable of all three of these types of reminders? [[Special:Contributions/141.101.107.96|141.101.107.96]] 23:02, 3 January 2019 (UTC)
:Probably not the first one, but if not, there probably will be now! ;-) [[User:Ianrbibtitlht|Ianrbibtitlht]] ([[User talk:Ianrbibtitlht|talk]]) 04:51, 4 January 2019 (UTC)
::Gmail definitely can remind you to answer an email (I don't know what exactly triggers this, I have a lot of unanswered emails I do not get reminders about, but I definitely got such reminders in a few cases), and it also warns you about missing attachments. I don't know about birthday reminders, as I didn't tell Google about the birthdays of my contacts. --[[Special:Contributions/162.158.93.27|162.158.93.27]] 09:57, 4 January 2019 (UTC)

Talk:887: Future Timeline

2018-12-22T14:57:01Z

162.158.93.27: /* The link is bad */ new section

The explanation is really messed up. You can hardly tell where one year ends and the next begins. Can someone who's better at editing than me fix this, perhaps by putting a line across the page after each year? [[User:GizmoDude|GizmoDude]] ([[User talk:GizmoDude|talk]]) 19:11, 7 April 2016 (UTC)

This one slipped under the transcripting radar. I may do it. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 20:52, 17 August 2013 (UTC)
:Do not talk about radars, just do it. The transcript is done right now, but the explain section still does need a big radar!--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:20, 18 August 2013 (UTC)

Find the song! I have no idea so far but the repeating phrase "Social security trust fund exhausted" should match a refrain.--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 20:20, 18 August 2013 (UTC)

They now have the dogs driving cars... http://www.youtube.com/watch?v=BWAK0J8Uhzk Let's not wait for 2053.[[Special:Contributions/173.245.54.90|173.245.54.90]] 21:01, 20 March 2014 (UTC)

Out of curiosity (I'm new to the standards of explainxkcd), are out of date pages considered incomplete? Or is it up to editors to chose when to update a pages explination. I would assume the former, except that would make maintaining the pages significantly more difficult. Also, referencing the Linux takes over. Since Android is now a part of the libux kernel,should thia be changed? It would definently put linux over the 50% mark. [[User:Mrmakeit|Mrmakeit]] ([[User talk:Mrmakeit|talk]]) 05:03, 4 April 2014 (UTC)
:Pages can not become out of date, as they refrence the meening of the comic at the time of creation. [[Special:Contributions/108.162.216.209|108.162.216.209]] 15:24, 10 December 2014 (UTC)

I would change the 2nd paragraph to say that the entirety of the search results are a super long set-up and "All your base..." is the punch-line. [[User:Smperron|Smperron]] ([[User talk:Smperron|talk]]) 08:46, 10 November 2014 (UTC)

I would correct the entry in 2014 that says that the Taliban are the organisation responsible for the September 11th attacks. The more accurate explanation would be that The US believed Al Qaeda (the real organisation responsible) were hiding out in Afghanistan and that defeating the Taliban, and bringing stability to the country was an important stepping stone towards finding Osama Bin Laden. Of course we now know he was in Pakistan all along, but still that was the original rationale for invading Afghanistan.--[[Special:Contributions/141.101.98.192|141.101.98.192]] 15:27, 15 December 2014 (UTC)

This further details stuff is wrong about the comic. The lines are just random answers to Google searches. There is no explanation. I move to remove this table, or convert it into links or summaries of the articles in the links. This sucks. It is good enough as it is now without the table (as the table is random and the explanations on the table are incorrect. [[Special:Contributions/108.162.216.209|108.162.216.209]] 22:12, 15 December 2014 (UTC)
:Let's get to work on the table then. I'm adding suitable references to incomplete sections to aid as jumping off points, from where further expansion can be done on a case-by-case basis. Can you provide some inspiration as to which explanations are most egregiously in need of correction? [[User:Pmw57|Pmw57]] ([[User talk:Pmw57|talk]]) 01:44, 8 January 2015 (UTC)

As of 2014 I have noticed that a lot of US sites are moving from html to closed sources such as Adobe so the quote: "The prediction about GNU/Linux Operating Systems is ambiguous" is now fighting through government agencies. Users of Linux trying to access the volcano archive (once supplied by listserv using linux) now have to get access via Windows machines. This has to be the saddest computing news in a long time. [[User:Weatherlawyer|Weatherlawyer]] ([[User talk:Weatherlawyer|talk]]) 08:19, 4 January 2015 (UTC)

“The prediction about GNU/Linux Operating Systems is ambiguous, as Android (based on Linux) constitutes nearly 50% of the mobile OS market” — GNU/Linux refers to an operating system consisting of the GNU userland toolchain over the Linux kernel. Android is based on Linux but not GNU, therefore, it is irrelevant in GNU/Linux context. [[Special:Contributions/108.162.230.107|108.162.230.107]] 11:18, 23 January 2015 (UTC)

Can we change this to Incomplete explanation of the month? [[User:Foldark|Foldark]] ([[User talk:Foldark|talk]]) 22:03, 28 March 2015 (UTC)

2145:War... War never changes
(the Great War happens) {{unsigned ip|173.245.54.252}}

Is it just my reading, or does it say "ACHEIVE" instead of "ACHIEVE" where it says something about 192 UN member nations achieving millennium development goals in the comic? (It's under 2015.) --[[Special:Contributions/172.68.55.70|172.68.55.70]] 21:45, 10 November 2016 (UTC)
:No, it reads like this for me too. (Even on the original comic page, where I'd expect it to have been long fixed already.) --[[Special:Contributions/172.68.11.87|172.68.11.87]] 19:35, 11 November 2016 (UTC)

Some of these predictions seem very realistic. [[Special:Contributions/162.158.59.172|162.158.59.172]] 00:22, 25 December 2016 (UTC) Jawa457

I am not sure if this needs to be added or not since it was not happening when the comic was produced and it is not the government doing it but a private tech company microchipping its employees in 2017 [https://www.google.com/search?q=microchipping+workers&rlz=1C1OPRB_enUS709US709&oq=microchipping+workers&aqs=chrome..69i57j0.3111j0j7&sourceid=chrome&ie=UTF-8 Google results] since I do not know which news articles will disappear over time. [[Special:Contributions/162.158.62.231|162.158.62.231]] 12:03, 17 August 2017 (UTC)

== The link is bad ==

[//origo.hu/gazdasag/20180822-az-usa-allamadosaga-rekordot-dontott.html Here]'s a working one. [[Special:Contributions/162.158.93.27|162.158.93.27]] 14:57, 22 December 2018 (UTC)

566: Matrix Revisited

2018-11-20T11:41:57Z

162.158.93.27: /* Explanation */ add some explanation to first scene

{{comic
| number = 566
| date = April 8, 2009
| title = Matrix Revisited
| image = matrix_revisited.png
| titletext = I actually remember being entertained by both the sequels while in the theater. They just don't hold up nearly as well in later comparison.
}}

==Explanation==
In the first frame it is stated that the comic was released on the anniversary of the movie ''{{w|The Matrix}}''. This is not true. The Matrix was released 31 March 1999 in the US, although it was next released in Australia on 8 April 1999, ten years before the release of this comic. But maybe [[Randall]] drew the comic (and had watched the movie) on the true 10 year anniversary day.

[[Megan]] is shocked when she realizes it is already ten years ago that ''The Matrix'' came out. This is an effect Randall has used to [[:Category:Comics_to_make_one_feel_old|make you feel old]] several times (for instance he mentions The Matrix again two years later in [[891: Movie Ages]].)

In ''The Matrix'', almost all of humanity lives in a computer simulation. Many years ago, robots took over the real world (not the simulation), and placed humans into the simulation while their body heat generated power for the robots. A few people have escaped from the Matrix, and they are on a mission with others to free the human race from the robots. The title of the strip is a reference to the documentary on the filming of ''The Matrix'': ''{{w|The Matrix Revisited}}''.

In the first three rows of the comic we see three famous scenes from ''The Matrix'' parodied by Randall. The characters are {{w|Morpheus (The Matrix)|Morpheus}}, with sunglasses; {{w|Neo (The Matrix)|Neo}}, as [[Cueball]] in the first two scenes and with a black cape in the third scene; {{w|Trinity (The Matrix)|Trinity}}, as [[Hairbun]]; and a security guard in the third scene, as another Cueball-like guy.

In the first scene Morpheus tells Neo that one cannot explain what the Matrix is and that he must see it for himself to understand. Morpheus is very mysterious as he tempts Neo to take a look himself, which, in the movie, leads to the next scene. In this comic, however, Trinity makes Morpheus look foolish by clearly explaining the Matrix in a single, simple phrase, and then telling him that he must suck at explaining. (The actual quote from the movie is <q>no one can be told what the Matrix is</q>, which makes more sense: even after being rescued from the Matrix, Neo at first refuses to accept that his entire life has been a simulation, becoming highly distraught when confronted with that truth. Morpheus later mentions that for this reason, it is unusual to rescue people past a certain age.)

In the next scene Morpheus tries to ignore Trinity's remark and continues by showing Neo two pills, one red and one blue, and tells Neo that he can either take the blue pill and return to the simulation (the Matrix), never to hear about the Matrix again, or he can take the red pill and leave the Matrix, and "see how deep the rabbit hole goes" (a reference to "{{w|Alice in Wonderland}}"). In the movie, Neo takes the red pill. In the comic, however, he mixes the two pills then {{w|Insufflation_(medicine)|snorts}} the purple powder he has created as though it was an illegal drug such as cocaine, and apparently winds up in a bizarre upside down and inverted dimension, presumably caused by his 'Drug Trip'. Even Morpheus now has no idea where they are. Note that the inversion of both color and orientation could be intended to evoke the idea of capturing an image on film (i.e. a film negative), which is *really* the only place where Neo and Morpheus exist. It is possible that the combination of pills allowed Neo to break through another layer of the simulation. Alternatively, this could simply be Randall trying to explain that they are in an alternate dimension whilst still remaining within the constraints of stick figures on white and black backgrounds.

What leads up to the third scene is when Neo and Trinity must save Morpheus, who has been captured by {{w|Agent (The Matrix)|agents}} of the simulation. They obtain many guns and load them into trenchcoats. In the shown scene Neo is stopped at a security checkpoint in a building in the Matrix. A security guard tells him to remove any metallic items, since the scanner has shown him to have metal on his person, such as keys, and place them in a bin, then walk through the scanner again. In the movie, he opens his trenchcoat, revealing a myriad of weapons and dispatching all of the guards with the assistance of Trinity. In the comic, however, Neo opens his trenchcoat, but the guard's response of "eww" implies that Neo is otherwise naked and the guard is disgusted by his display of his genitals (This could seem ironic since the guard could be said to be even more naked than him. But in the xkcd version of the matrix, stick people are presumably fully dressed unless otherwise indicated. See Megan topless in [[864: Flying Cars]], naked Cueball in [[1977: Paperwork]], and Hairy in [[761: DFS]].)

When Randall (as Cueball) has seen the movie he turns to his friends (Megan and another Cueball-like guy) and exclaims that he had forgotten how great the movie is. When his friend suggests that they put on the other two sequels, there is a beat panel where Megan and Cueball look at each other, then they beat up the offender off-panel.

The two sequels to ''The Matrix'' are widely regarded as inferior to the original, with some fans {{tvtropes|FanonDiscontinuity|pretending they don't exist}}. This is what happens when Megan and Cueball return, and Cueball repeats his statement about how good it was. Then Megan is saddened by the fact they never made any sequels and Cueball agrees. Thus trying hard (even violently) to forget those sequels.

On {{w|IMDb}} the original movie was still in the top 20 on their [http://www.imdb.com/chart/top?tt0133093&ref_=tt_awd top 250 chart] in July 2015, with an average of [http://www.imdb.com/title/tt0133093/ 8.7] vs. only [http://www.imdb.com/title/tt0234215 7.2] and [http://www.imdb.com/title/tt0242653 6.7] to the sequels (though even those two scores are relatively high compared to other action titles).

9 years (and one day) later Randall made the comic [[1978: Congressional Testimony]] where the movie {{w|The Terminator}} is mentioned. In the title text a similar line of thought as the one in the bottom strip of this comic is made. The third movie in the Terminator Franchise was so great that Skynet sent back a robot to prevent James Cameron, the director of the first two Terminator movies, from directing it, and instead another (much worse) version of the movie was later directed by another director. This indicates that Randall would rather not have had the third movie made, and also fantasizes about how much better it could have been with the original director making T3.

==Transcript==
:[Megan stands below two pieces of text, in a panel that is without a frame.]
:Today was the ten-year anniversary of the release of ''The Matrix.''
:I sat down to watch it again.
:Megan: Holy fuck, ten years ago?

:[The next three panels of the first row and the next two rows spoofs three scenes from The Matrix.]

:[In scene 1 Morpheus with sunglasses and Trinity with hair bun are talking to Cueball-Neo. Morpheus has his hands together.]
:Morpheus: Unfortunately, no one can explain what the matrix is. You have to see it for yourself.

:[Trinity lifts her hand.]
:Trinity: Sure you can. It's a computer simulation in which you live, thinking it's reality.
:Neo: Oh.

:[Morpheus takes his hands down and turns around glaring at Trinity who has also taken her hand down.]
:Trinity: ...What?
:Trinity: Look, maybe you just suck at explaining.

:[In scene 2 Morpheus is talking to Neo while holding a red pill and a blue pill. To the far right is a part of a table.]
:Morpheus: ...Or you take the red pill, and I show you how deep the rabbit hole goes.

:[Neo takes both pills from Morpheus.]

:[Neo crushes both the red and blue pills on a table top.]
:''Crush''

:[Neo snorts the resulting purple powder through a pipe he holds up to his face (his nose).]
:''Snort''

:[Morpheus and Neo are shown upside down in a frame with inverted colors, i.e., black background with white lines.]
:Morpheus: Now look what you've done.
:Neo: Where are we?
:Morpheus: I have no idea.

:[In scene 3 Neo, wearing a long, black trench coat, at a metal detector, is accosted by the Cueball-like security guard.]
:Guard: Please remove any keys, metallic items, weapons—

:[Neo steps close to the guard and opens his trench coat towards the guard, who is facing the reader. The reader can't see what Neo has under his coat.]

:[Same scene as above, but side view: Neo, on the left, is opening his coat toward the guard, who is on the right and seems to be looking down. Nobody speaks.]

:[Same scene as above but the guard now looks up to Neos face and finally speaks:]
:Guard: Eww.

:[In the last row of the comic we see three characters that have obviously just finished watching The Matrix. Cueball is sitting on the floor nearest to the TV, Megan is sitting on the floor, farther from the TV and a Cueball-like friend is sitting on an armchair, farthest from the TV.]
:Cueball: I forgot how good that movie was.
:Friend: Wanna put on the other two?

:[Cueball, still sitting has turned to face Megan. They exchange looks without speaking.]

:[View of room, which is now empty, as is the chair. Sounds comes from off-screen to the right.]
:''Crash''
:''Wham''
:Friend (off-screen): Ow! Ow!

:[Cueball and Megan are back in the room, zoomed in so the TV is no longer visible, but the chair is and it remains empty. The friend is nowhere to be seen.]
:Cueball: I forgot how good that movie was.
:Megan: Too bad they never made any sequels.
:Cueball: True.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Comics with inverted brightness]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hairbun]]
[[Category:Comics featuring Cueball]]
[[Category:Multiple Cueballs]]
[[Category:The Matrix]]
[[Category:Comics to make one feel old]]

Talk:2066: Ballot Selfies

2018-11-01T00:55:53Z

162.158.93.27: sign comment

What harm do laws banning ballot selfies do? [[User:Ryanker|Ryanker]] ([[User talk:Ryanker|talk]]) 15:51, 31 October 2018 (UTC)ryanker
: I'm thinking the flavor text is talking as if from the point of view of someone who has grown used to sharing photos of themselves with others, to communicate, encourage, feel connected. Depicting their own behavior so directly might even seem a valid way to sway someone's opinion to such a person. I guess when thinking about it, it would support democracy better to share the act of voting rather than the actual vote made. Curious regarding other opinions. [[Special:Contributions/162.158.91.83|162.158.91.83]] 16:09, 31 October 2018 (UTC)
:: yes, fully agree with this. Just take all the selfies you want on the way there, in front of the place where you vote, on the way back. Just not during that one minute you spend inside the booth, and not showing your actual ballot. If you absolutely want to disclose what you actually voted for, you can still do so by writing a caption. It's that simple, and probably legal in most places around the world.--[[Special:Contributions/141.101.77.140|141.101.77.140]] 16:22, 31 October 2018 (UTC)
: Thought of another reason: if the government were to hack or misrepresent the vote, the people could use proof of voting to prove the fraud. [[Special:Contributions/172.68.50.136|172.68.50.136]] 16:12, 31 October 2018 (UTC)
:: If a government can hack your vote, couldn't they hack your phone? ;-) [[User:Kev|Kev]] ([[User talk:Kev|talk]]) 16:28, 31 October 2018 (UTC)
::: But you could just print out the photo, and it becomes physical, unhackable proof. {{unsigned ip|162.158.79.101}}
::: Additionally, to fake your vote, all they need to do is lie. [[Special:Contributions/162.158.93.27|162.158.93.27]] 00:55, 1 November 2018 (UTC)

In the United kingdom it is illegal to take a phtograph of the ballot paper even if no vote is recorded - as such an image could reveal the mark used to authenticate the ballot paper.
Until recently this was a pattern of holed stamped into the paper as it is issued, though now printed bar codes are used. Theoretically if you know the mark, you could then stuff a ballot box. Although if the number of papers does not match that recorded by the returning clerk then the entire box would be declared invalid and the election rerun. [[User:Arachrah|Arachrah]] ([[User talk:Arachrah|talk]]) 16:45, 31 October 2018 (UTC)
: I think you're saying that in states where vote selfies are legal, somebody might be able to use such a selfie to produce counterfeit ballots, and submit them. Also that the ballots are counted and a vote is rerun whenever the count is wrong, to additionally deter this. It's hard to believe that count is always correct for such huge numbers of physical objects each handled by a human being: does this rerun happen commonly? [[Special:Contributions/162.158.93.27|162.158.93.27]] 00:55, 1 November 2018 (UTC)

Talk:2066: Ballot Selfies

2018-11-01T00:55:18Z

162.158.93.27:

2066: Ballot Selfies

2018-10-31T16:05:28Z

162.158.93.27: Vote for ranked-choice.

{{comic
| number = 2066
| date = October 31, 2018
| title = Ballot Selfies
| image = ballot_selfies.png
| titletext = There were actually some good reasons for those laws, but IMO they now do more harm than good. Which raises a question: If there's a ballot measure to strike them down, how can I resist the urge to take a picture of my "yes" vote?
}}

==Explanation==
{{incomplete|Please only mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

"Ballot selfies" refers to the practice of taking a picture of oneself with a completed ballot. These have been declared illegal in many states as the proof that someone has voted a certain way can enable the buying or violent coercion of votes. Usually when an oil painting is made, a painter paints a subject, watching them. This solution solves the problem of being proof of the vote (since that part can be changed in the painting), while creating the additional problem of allowing extra people to watch the vote being cast, which can similarly be used to enable vote buying or coercion. As such, it's unlikely to be considered any more legal than ballot selfies. Ponytail here is attempting to solve both issues, by painting a self-portrait inside the booth. She appears to have forgotten a mirror, however.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

[Five people are standing in a line, from left to right: Megan, Ponytail, Cueball, White Hat, and Hairbun, with Hairbun at the front of the line. All are facing to the right except Cueball, who is looking to his left at Ponytail. Ponytail holds an easel under her right arm and a paintbrush in her right hand.]

:Ponytail: Ballot selfies are illegal in this state, so to immortalize my vote I'm doing an oil painting in the voting booth.

{{comic discussion}}

2064: I'm a Car

2018-10-27T09:37:15Z

162.158.93.27: added reference to pipe bomb suspect's sticker-covered van

{{comic
| number = 2064
| date = October 26, 2018
| title = I'm a Car
| image = im_a_car.png
| titletext = I'm the proud parent of an honor student, and the person driving me is proud, too!
}}

==Explanation==
{{incomplete|Please only mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

This comic was released eleven days before the {{w|United States midterm election|United States midterm elections}} on {{w|United States elections, 2018|Tuesday, November 6, 2018}} and even the [[Design_of_xkcd.com#Header|header text]] at the top of the xkcd page had changed a few days before by showing a link to [https://www.vote.org/ vote.org] to help US citizens to register and finding their polling places. [[Randall]] uses a neutral way to encourage people to use the right to rule their governmental representatives. Only before the {{w|United States presidential election, 2016|presidential election, 2016}} he took sides to one party as done in the comic [[1756: I'm With Her]].

This comic shows a car with a {{w|bumper sticker}}, which is generally a thin rectangle piece of plastic with a message on one side and adhesive on the other side in order to stick to a car. This allows the owner of the car to display a message they want to present to whoever is driving behind them or in their vicinity. Bumper stickers are usually used to express a viewpoint, whether personal or political, held by the owner or driver of the car. This comic makes literal the ones that include or allude to the personal pronoun "I" and its variations, i.e. {{w|Grammatical person|first person singular}} statements. Of course the intent is that "I" is referring to the person who put the bumper sticker on the car, but as the sticker is attached to the car the more literal interpretation is that "I" is referring to the car. So the humor is derived by the notion that the car itself is making these statements.

The bumper sticker on the car in the comic is a variation of a sticker used to both encourage people to vote, as well as express their political position: "I'm a ___, and I vote" (where the blank is traditionally filled in with "Democrat" or "Republican" or some other political affiliation). However here it is attributed to an automobile which is not capable of voting.[https://resources.lawinfo.com/civil-rights/right-to-vote/what-are-the-requirements-to-be-eligible-to-v.html]

The comic could be an indirect reference to the growing "intelligence" of {{w|self-driving cars}}, such that one day they might have the intellect to communicate, vote, and engage in other self-motivated activities. See ‘{{w|Sally (short story)|Sally}}’ by {{w|Isaac Asimov}}.

Possibly Randall is ironically referring to the car of the suspect in the pipe bomb case. His whole [https://cdn.cnn.com/cnnnext/dam/assets/181026125735-03-tarp-off-screengrab-1026-closer-exlarge-169.jpg van is covered with pro-Trump, anti-Democrat and anti-liberal stickers]. Or it's just particularly bad timing...

The title text seems to be another [https://www.positivepromotions.com/proud-parent-of-an-honor-student-bumper-sticker-personalization-available/p/os-3360/ typical message] on a bumper sticker, saying that the driver is a "Proud Parent Of An Honor Student". However, this sticker is a bit longer, since it continues to state that "the person driving me is proud, too". Thus once again it is the car who is the proud parent. And thus maybe it is a car that is the honor student?

==Transcript==
:[The bottom right rear end of a car is shown with a bumper sticker next to the unreadable license plate.]
:I'm a car
:''and I vote''

==Trivia==
*This is the third comic displaying a bumper sticker, after the comics [[80: My Other Car]] and [[1033: Formal Logic]] that came out in 2006 and 2012 respectively.
*Bumper stickers also are mentioned as a future milestone for self-driving cars in [[1925: Self-Driving Car Milestones]].
*Randall also sells bumper stickers with the word "OPINIONS!" on them at the [https://store.xkcd.com/products/opinions-bumper-sticker xkcd-store].

{{comic discussion}}

[[Category:Politics]]

2058: Rock Wall

2018-10-15T13:03:40Z

162.158.93.27: /* Explanation */

{{comic
| number = 2058
| date = October 12, 2018
| title = Rock Wall
| image = rock_wall.png
| titletext = I don't trust mantle/core geologists because I suspect that, if they ever get a chance to peel away the Earth's crust, they'll do it in a heartbeat.
}}

==Explanation==
{{incomplete|Created by a frustrated mantle geologist. Please edit the explanation below and only mention here why it isn't complete. Do NOT delete this tag too soon.}}

{{w|Mantle_(geology)|Mantle}} {{w|geologists}} study that {{w|Structure_of_the_Earth|part of the planet}} that's below the top "{{w|Crust_(geology)|crust}}" of the planet. The top layer of the planet, which is several dozen miles thick, is the only layer we've been able to explore, by {{w|mining|digging tunnels}}, {{w|spelunking}}, etc. The only way to study the mantle and other inner layers of the earth are through non-visual, non-tactile, indirect methods, and by analyzing old samples of the mantle that have made their way to the surface.

In this comic, [[Ponytail]], talking to [[Megan]], is describing her job as a mantle geologist as that of living on one side of a thick wall that is, and likely always will be, impossible to get through or around, but she has to study what is on the other side of the wall. In this case the wall is horizontal rather than vertical, the wall being the earth's crust.

In the title text [[Randall]] states that he doesn't trust mantle/core geologists. Because if they got the chance he believes they would not hesitate (even a heart beat) in stripping away Earth's crust to study the mantle or even worse the {{w|Inner core|core}} directly. Of course if they only did this locally to look at the mantle it would not shatter the Earth although that local area may become a volcano. But if they actually peeled the entire outer layer away, we humans would have no place to live, as the mantle is really hot and would melt easily (producing magmas and therefore lavas when magma’s exposed to surface, see title text of [[1405: Meteor]] to be more confused). However, after a while all these erupted lavas would solidify and become a new crust. Humanity needs to withstand just some millennia of active worldwide volcanism.

If they somehow exposed the core even locally something weird would be bound to happen{{Citation needed}}.

But Randall is afraid that their craving to get around that 20 mile wall would prevent the researchers from even hesitating if they did get that chance. Fortunately, we can study planetary cores in the solar system without stripping Earth's surface by visiting an asteroid which is thought to be the exposed iron core of a protoplanet. The [https://www.llnl.gov/news/lab-instrument-will-explore-asteroid-psyche Psyche mission] is scheduled to launch in 2023 and arrive at {{w|16 Psyche}} in 2030.

This comics seems to be a spin-off from the previous comic [[2057: Internal Monologues]], where Randall tried to find some interesting monologues from scientist from different research fields. Maybe he did not find an internal monologue he liked for geologists, but ended up with this idea instead. Thinking about the core or mantle, lava and Magma seems to be something Randall does a lot, and thus he must have some ideas about how a geologist would think, which was why this comic [[913: Core]], was also referenced in the previous comic as something geologist might have internal monologues about.

==Transcript==
:[Ponytail is gesturing towards Megan with her hand, while talking to her.]
:Ponytail: I live next to a wall of rock 20 miles thick. There's no way around or over it. I'm trapped on this side forever.
:Ponytail: I study the stuff on the other side.

:[Caption below the frame:]
:Mantle geology seems like the most frustrating field.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Science]]

2035: Dark Matter Candidates

2018-10-03T08:20:45Z

162.158.93.27: /* Maybe those orbit lines on space diagrams are real and very heavy */

{{comic
| number = 2035
| date = August 20, 2018
| title = Dark Matter Candidates
| image = dark_matter_candidates.png
| titletext = My theory is that dark matter is actually just a thin patina of grime covering the whole universe, and we don't notice it because we haven't thoroughly cleaned the place in eons.
}}

==Explanation==
{{w|Dark matter}} is a hypothetical, invisible form of matter used by the vast majority of astronomers to explain the far too high apparent mass of objects at large scales in our universe. In galaxies, stars are orbiting faster than the gravitational force of the sum of the masses of visible matter in the galaxy could cause, and entire galaxies are observed moving much faster around each other than their visible masses could explain. In galactic collisions, the mass can appear to separate from the visible matter, as if the mass doesn't collide but the visible matter does. A small handful of galaxies have been observed to not have this property, suggesting that it is a *thing* that a galaxy can have more or less of and is separable from. At scales of our solar system, those effects are too small and can't be measured. The most plausible explanation for all of these phenomena is that there is some "dark matter" that has gravity, but is otherwise undetectable. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities for what dark matter could possibly be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10-15 kg to 10-3 kg are given in grams together with appropriate prefixes, while the ton takes the place of 103 kg.

Only massive objects ranging from subatomic particles up to super massive ones are covered in this comic. There are also {{w|Dark matter#Alternative hypotheses|alternative hypotheses}} trying to modify general relativity with no need of additional matter. The problem is that these theories can't explain all different observations at once. Nonetheless dark matter is a mystery because no serious candidate has been found yet.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten, with explanations suggested by astronomers covering only some portions of that range. [[Randall]] fills the gaps with highly absurd suggestions.

==== Axion ====
An {{w|Axion|axion}} is a hypothetical elementary particle postulated in 1977 to resolve the strong CP problem in {{w|Quantum chromodynamics|quantum chromodynamics}}, a theory of the strong force between {{w|Quark|quarks}} and {{w|Gluon|gluons}} which form {{w|Hadron|hadrons}} like {{w|Proton|protons}} or {{w|Neutron|neutrons}}. If axions exist within a specific range of mass they might be a component of dark matter. The advantage of this particle is that it's based on a theory which could be proved or also disproved by measurements in the future. Other theories, not mentioned in this comic, like the {{w|Weakly interacting massive particles|Weakly interacting massive particles (WIMPs)}} are much more vague.

==== Sterile neutrino ====
{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter. The well known {{w|Neutrino|neutrinos}} are also charged under the {{w|Weak interaction|weak interaction}} and can be detected by experiments.

==== Electrons painted with space camouflage ====
{{w|Electron|Electrons}} are fundamental particles which compose the outer layers of atoms. A large number of electrons in the galaxy would be relatively easy to detect, as they not only interact with light (which dark matter does not appear to), but also have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say, this is not an actual candidate for dark matter.) The mass of an electron is about 0.5 MeV which fits well into the graph.

==== Neutralino ====
A {{w|Neutralino|neutralino}} is a hypothetical particle from {{w|Supersymmetry|supersymmetry}} and is also a current candidate for dark matter. But there is not evidence whether or not supersymmetry is correct and none of the predicted particles have been found yet.

==== Q-ball ====
In theoretical physics, a {{w|Q-ball}} is a stable group of particles. It's an actual candidate for dark matter.

(In billiards, a cue ball is the white (or yellow) ball hit with the cue in normal play. In addition, [[Cueball]] is the name explainxkcd uses for the most common xkcd character.)

==== Pollen ====
{{w|Pollen}} is a joke candidate, though people with seasonal allergies may suspect that the universe is genuinely made up entirely of pollen in the springtime.

==== No-See-Ums ====
{{w|Ceratopogonidae|No-See-Ums}} are a family (Ceratopogonidae) of small flies, 1–4 mm long, that can pass through most window screens. Another joke candidate, because dark matter is invisible and the name "no-see-ums" implies that the flies are invisible.

==== Bees ====
Insects of the clade {{w|Bee|Antophila}} are major pollinators of flowering plants. In recent years {{w|Colony collapse disorder|bees have been disappearing}} at an alarming rate; {{w|The Stolen Earth|Doctor Who explained}} that they are in fact aliens leaving Earth prior to a Dalek invasion.

==== 8-balls ====
In pool, the {{w|Pool (cue sports)|8-ball}} is a black ball numbered 8. It's a pun with Q-ball/cue ball. Unless undetected aliens have discovered billiards and become addicted to it, 8-balls are found only on Earth and are, hence, unlikely dark matter candidates. The 8-ball is also a popular unit of sale for black market pharmaceuticals like cocaine, where it stands for 1/8th of an ounce (3.5g). This doesn't make sense as a dark matter candidate either -- unless dark matter is hard to detect because it's illegal & trying to avoid the cops.

==== Space Cows ====
Cows are {{w|Bovinae|bovines}} extensively farmed on Earth for milk and meat. Although there is folklore concerning cows {{w|Hey diddle diddle|achieving circum-lunar orbits}}, not to mention their appearance on a {{w|Shindig (Firefly)|beloved space western TV show}}, as Muppet cow [http://muppet.wikia.com/wiki/Natalie Natalie] in the Sesame Street News Flash (and [https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWestern others less-remembered]), they have yet to be found elsewhere in the Universe. In the television show "Too Close for Comfort", one of the characters is the cartoonist of a comic strip called "Cosmic Cow". {{w|Spherical cow|Spherical cows}} have also been used (humorously) by physicists needing to simplify some source of mass in a given problem.

==== Obelisks, Monoliths, Pyramids ====
While those human constructions are huge on a human scale, they're negligible at universe-scale. It would take a large number of such constructions, distributed through space, to replicate the effects of dark matter; while a scenario could be envisioned where enough such constructs existed, with properties and distribution allowing them to match observations, this is obviously not a likely explanation.
They often show up in fiction and pseudo-scientific literature as alien artifacts generating immense unknown power out of nowhere, with the most famous and influential example being the three monoliths from {{w|2001: A Space Odyssey (film)|2001: A Space Odyssey}} (with the largest having a mass of about 500,000 tonnes).

==== Black Holes ruled out by: ====
{{w|Black hole|Black holes}} are known to occur in sizes of a few solar masses (about 1030-1031 kg) as remnants of the core of former big stars, as well as in quite large sizes at the centers of galaxies (millions or even billions of solar masses). But recent gravitational wave detections indicate that black holes at 50 or 100 solar masses also exist, though their origin is still not understood. Randall doesn't mention this but some astronomers hope that these could fill at least a part of the gap. While black holes are widely reported to be ruled out as a candidate for dark matter for various reasons Randall has listed, such constraints are based on "monochromatic" mass distributions -- meaning that all such black holes are assumed to have the same mass -- which is considered physically implausible for populations of merging bodies which are known to have vastly different masses. See: [https://arxiv.org/pdf/1709.07467.pdf Primordial Black Holes as Dark Matter (2017)] and [https://arxiv.org/pdf/1705.05567.pdf Primordial black hole constraints for extended mass functions (2017)] (That this is a common practice in cosmology may be part of the reference to "buzzkill" astronomers.) He rules out all black holes in the range of approximately 1010 kg to 1033 kg even when below some gaps at the bars appear.

Except the last item, all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four solar masses.
* Gamma rays: If dark matter were black holes of this size, the black holes could be evaporating by the predicted {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction if many of those objects would exist. Nonetheless this radiation is still hypothetical and not been observed on any known black holes. Furthermore those objects would be very small because the Schwarzschild radius of a 1012 kg black hole is approximately 148 fm (1.48×10−13 m), which is between the size of an atom and an atomic nucleus.
* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe and have been observed only in distant galaxies. While gravitational microlensing (see below) is an astronomical phenomenon, it doesn't make much sense here. GRBs are short (milliseconds to several hours) and are often detected only by space-borne sensors for gamma-rays -- rarely at any other wavelengths. Measuring lensing effects would be very difficult. This [https://arxiv.org/abs/1406.3102 paper] discusses the probability of detecting lensing effects caused by {{w|Dark matter halo|galactic halo objects}} among the known GRBs given sufficient objects to represent the missing mass.
* Neutron star data: {{w|Neutron star|Neutron stars}} aren't black holes, but they're also very small highly compact objects at about 1.4-2.16 solar masses. While black holes can't be observed directly, neutron stars are detectable in many wavelengths. The number of them gives a clue about the number of black holes close to the mass of the sun, a number which is far too low to make up dark matter.
* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect, (the path of radiation is changed by passing through space bent by nearby mass). This was predicted by Einstein's {{w|General Relativity|Theory of General Relativity}} and was first confirmed in 1919 during a solar eclipse, when a star which was nearly in line with the sun appeared more distant to the sun than usual. Astronomers have found many so called {{w|Einstein ring|Einstein rings}} or Einstein crosses where a massive object in front of other galaxies bends the light toward us. Those massive objects may be black holes, but the number is far too low to explain dark matter.
* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and has been very stable since shortly after its formation. If not, we wouldn't exist. If dark objects at 1024 kg - 1030 kg (mass of Earth up to mass of Sun) accounted for dark matter and were distributed throughout galaxies, there should be many of them in the vicinity of our solar system and the system wouldn't be stable at all.
* Buzzkill Astronomers: Black holes above a certain size are thought by some astronomers to be impossible to miss, due to the effects they have on nearby matter. At the mass of some 1030 kg there must be many supernova remnants we still haven't found. Black holes of about 1035 kg have long been considered dark matter candidates by a minority group of cosmologists, as could be seen here [https://arxiv.org/pdf/1001.2308.pdf Primordial Black Holes as All Dark Matter (2010)] and the Milky Way's first discovered intermediate mass black hole falling in this range shown here [https://www.nao.ac.jp/en/news/science/2016/20160115-nro.html Signs of Second Largest Black Hole in the Milky Way].
Not covered by this comic are {{w|Massive compact halo object|massive astrophysical compact halo objects (MACHOs)}} composed of hard to detect dim objects like black holes, neutron stars, brown dwarfs, and other objects composed of normal {{w|Baryon|baryonic}} matter. Nevertheless observations have shown that the total amount of baryonic matter in our universe on large scales is much smaller than it would be needed to explain all the measured gravitational effects.

==== Maybe those orbit lines on space diagrams are real and very heavy ====
Diagrams of our solar system (or any planetary system) often show lines representing the elliptical paths the planet takes around its sun. These lines don't show real objects, though. Astronomers just draw them on pictures of the solar system to show where the planets move. If you draw a line on a map to give someone directions, that line isn't an object in real life; it's just on the map. If these lines were real, they would be ''huge'' (Earth's would be 940 million km long (2π AU) and Neptune's would be 28 ''billion'' kilometers long). [https://www.youtube.com/watch?v=0fKBhvDjuy0 Powers of Ten (1977)] gives a good sense of just how large these orbit lines need to be in order to be visible in space diagrams. If these orbit lines were also very dense, they would have a huge mass and could possibly account for the missing 85% of the mass in the universe. But they would also constantly be impaling the planets, including the Earth, which would probably be a problem. Their mass would also affect planetary motions in ways which we would detect. A related worry about space travel was expressed in previous centuries; it was thought that the planets were embedded within {{w|Celestial spheres|crystal shells}} (spheres or Platonic solids), and a rocket into space could smash the shells and send planets plummeting to Earth. Another joke candidate.

Due to Gauss' shell theorem the orbit lines wouldn't contribute to gravitational binding energy of the orbiting bodies. Gauss's law for gravity states:

<blockquote>The gravitational flux through any closed surface is proportional to the enclosed mass.</blockquote>

As a result the systems would be unstable and would "Boil off". Consider the innermost orbiting body, since there is not enough observable mass to bind that body there must be dark matter, but no mass contribution comes from its own orbit line hence it escapes, now the second closest body has even less mass binding it so that body will also escape, by induction no body can be bound by massive orbit lines.

==== Title text ====
The title text refers to the fact that space is just vast emptiness where a little bit of dirt could be overlooked. Actually the mean density of detectable matter in the universe, according to NASA, is equivalent to roughly [https://map.gsfc.nasa.gov/universe/uni_matter.html 1 proton per 4 cubic meters]. And because this matter is mostly located in galaxies -- and inside there in stars and clouds -- the space between is even more empty. For comparison, one gram hydrogen consists of {{w|Avogadro constant|6.022 x 1023 atoms}}. Like at home wiping with a cleaning cloth in which we can see the dirt that wasn't clearly visible on the surface we have wiped, Randall believes that some few atoms more per cubic meter could stay undetected in the same way. This isn't true because in the space between galaxies astronomers can detect matter as it spreads over thousands or millions cubic light years. Atoms can't hide; there is always radiation.

==Transcript==
:Dark matter candidates:
:[A line graph is shown and labeled at left quarter in eV and further to the right in g together with some prefixes.]
:[The labels read:]
:µeV, meV, eV, keV, MeV, GeV, TeV, 10-18kg, ng, µg, mg, g, kg, TON, 106kg, 1012kg, 1018kg, 1024kg, 1030kg

:[All items are shown in bars ranging between two approximately values:]
:< 1 µeV - 10 meV: Axion

:1 eV - 10 keV: Sterile neutrino

:0.5 MeV (exactly): Electrons painted with space camouflage

:10 GeV - 10 TeV: Neutralino

:100 TeV - 10-17 kg: Q-ball

:1 ng - 100 ng: Pollen

:0.1 mg - 1 mg: No-See-Ums

:10-1 g (exactly): Bees

:10 g - 100 g: 8-balls

:100 kg - TON: Space cows

:TON - 109 kg: Obelisks, monoliths, pyramids

:109 kg - 1033 kg: Black holes ruled out by:
::109 kg - 1013 kg: Gamma rays
::1013 kg - 1017 kg: GRB lensing
::1015 kg - 1022 kg: Neutron star data
::1021 kg - 1030 kg: Micro lensing
::1024 kg - 1030 kg: Solar system stability
::1030 kg - 1033 kg: Buzzkill astronomers

:1033 kg - >1036 kg: Maybe those orbit lines on space diagrams are real and very heavy

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Line graphs]]

2035: Dark Matter Candidates

2018-10-03T08:14:52Z

162.158.93.27: /* Maybe those orbit lines on space diagrams are real and very heavy */

{{comic
| number = 2035
| date = August 20, 2018
| title = Dark Matter Candidates
| image = dark_matter_candidates.png
| titletext = My theory is that dark matter is actually just a thin patina of grime covering the whole universe, and we don't notice it because we haven't thoroughly cleaned the place in eons.
}}

==Explanation==
{{w|Dark matter}} is a hypothetical, invisible form of matter used by the vast majority of astronomers to explain the far too high apparent mass of objects at large scales in our universe. In galaxies, stars are orbiting faster than the gravitational force of the sum of the masses of visible matter in the galaxy could cause, and entire galaxies are observed moving much faster around each other than their visible masses could explain. In galactic collisions, the mass can appear to separate from the visible matter, as if the mass doesn't collide but the visible matter does. A small handful of galaxies have been observed to not have this property, suggesting that it is a *thing* that a galaxy can have more or less of and is separable from. At scales of our solar system, those effects are too small and can't be measured. The most plausible explanation for all of these phenomena is that there is some "dark matter" that has gravity, but is otherwise undetectable. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities for what dark matter could possibly be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10-15 kg to 10-3 kg are given in grams together with appropriate prefixes, while the ton takes the place of 103 kg.

Only massive objects ranging from subatomic particles up to super massive ones are covered in this comic. There are also {{w|Dark matter#Alternative hypotheses|alternative hypotheses}} trying to modify general relativity with no need of additional matter. The problem is that these theories can't explain all different observations at once. Nonetheless dark matter is a mystery because no serious candidate has been found yet.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten, with explanations suggested by astronomers covering only some portions of that range. [[Randall]] fills the gaps with highly absurd suggestions.

==== Axion ====
An {{w|Axion|axion}} is a hypothetical elementary particle postulated in 1977 to resolve the strong CP problem in {{w|Quantum chromodynamics|quantum chromodynamics}}, a theory of the strong force between {{w|Quark|quarks}} and {{w|Gluon|gluons}} which form {{w|Hadron|hadrons}} like {{w|Proton|protons}} or {{w|Neutron|neutrons}}. If axions exist within a specific range of mass they might be a component of dark matter. The advantage of this particle is that it's based on a theory which could be proved or also disproved by measurements in the future. Other theories, not mentioned in this comic, like the {{w|Weakly interacting massive particles|Weakly interacting massive particles (WIMPs)}} are much more vague.

==== Sterile neutrino ====
{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter. The well known {{w|Neutrino|neutrinos}} are also charged under the {{w|Weak interaction|weak interaction}} and can be detected by experiments.

==== Electrons painted with space camouflage ====
{{w|Electron|Electrons}} are fundamental particles which compose the outer layers of atoms. A large number of electrons in the galaxy would be relatively easy to detect, as they not only interact with light (which dark matter does not appear to), but also have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say, this is not an actual candidate for dark matter.) The mass of an electron is about 0.5 MeV which fits well into the graph.

==== Neutralino ====
A {{w|Neutralino|neutralino}} is a hypothetical particle from {{w|Supersymmetry|supersymmetry}} and is also a current candidate for dark matter. But there is not evidence whether or not supersymmetry is correct and none of the predicted particles have been found yet.

==== Q-ball ====
In theoretical physics, a {{w|Q-ball}} is a stable group of particles. It's an actual candidate for dark matter.

(In billiards, a cue ball is the white (or yellow) ball hit with the cue in normal play. In addition, [[Cueball]] is the name explainxkcd uses for the most common xkcd character.)

==== Pollen ====
{{w|Pollen}} is a joke candidate, though people with seasonal allergies may suspect that the universe is genuinely made up entirely of pollen in the springtime.

==== No-See-Ums ====
{{w|Ceratopogonidae|No-See-Ums}} are a family (Ceratopogonidae) of small flies, 1–4 mm long, that can pass through most window screens. Another joke candidate, because dark matter is invisible and the name "no-see-ums" implies that the flies are invisible.

==== Bees ====
Insects of the clade {{w|Bee|Antophila}} are major pollinators of flowering plants. In recent years {{w|Colony collapse disorder|bees have been disappearing}} at an alarming rate; {{w|The Stolen Earth|Doctor Who explained}} that they are in fact aliens leaving Earth prior to a Dalek invasion.

==== 8-balls ====
In pool, the {{w|Pool (cue sports)|8-ball}} is a black ball numbered 8. It's a pun with Q-ball/cue ball. Unless undetected aliens have discovered billiards and become addicted to it, 8-balls are found only on Earth and are, hence, unlikely dark matter candidates. The 8-ball is also a popular unit of sale for black market pharmaceuticals like cocaine, where it stands for 1/8th of an ounce (3.5g). This doesn't make sense as a dark matter candidate either -- unless dark matter is hard to detect because it's illegal & trying to avoid the cops.

==== Space Cows ====
Cows are {{w|Bovinae|bovines}} extensively farmed on Earth for milk and meat. Although there is folklore concerning cows {{w|Hey diddle diddle|achieving circum-lunar orbits}}, not to mention their appearance on a {{w|Shindig (Firefly)|beloved space western TV show}}, as Muppet cow [http://muppet.wikia.com/wiki/Natalie Natalie] in the Sesame Street News Flash (and [https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWestern others less-remembered]), they have yet to be found elsewhere in the Universe. In the television show "Too Close for Comfort", one of the characters is the cartoonist of a comic strip called "Cosmic Cow". {{w|Spherical cow|Spherical cows}} have also been used (humorously) by physicists needing to simplify some source of mass in a given problem.

==== Obelisks, Monoliths, Pyramids ====
While those human constructions are huge on a human scale, they're negligible at universe-scale. It would take a large number of such constructions, distributed through space, to replicate the effects of dark matter; while a scenario could be envisioned where enough such constructs existed, with properties and distribution allowing them to match observations, this is obviously not a likely explanation.
They often show up in fiction and pseudo-scientific literature as alien artifacts generating immense unknown power out of nowhere, with the most famous and influential example being the three monoliths from {{w|2001: A Space Odyssey (film)|2001: A Space Odyssey}} (with the largest having a mass of about 500,000 tonnes).

==== Black Holes ruled out by: ====
{{w|Black hole|Black holes}} are known to occur in sizes of a few solar masses (about 1030-1031 kg) as remnants of the core of former big stars, as well as in quite large sizes at the centers of galaxies (millions or even billions of solar masses). But recent gravitational wave detections indicate that black holes at 50 or 100 solar masses also exist, though their origin is still not understood. Randall doesn't mention this but some astronomers hope that these could fill at least a part of the gap. While black holes are widely reported to be ruled out as a candidate for dark matter for various reasons Randall has listed, such constraints are based on "monochromatic" mass distributions -- meaning that all such black holes are assumed to have the same mass -- which is considered physically implausible for populations of merging bodies which are known to have vastly different masses. See: [https://arxiv.org/pdf/1709.07467.pdf Primordial Black Holes as Dark Matter (2017)] and [https://arxiv.org/pdf/1705.05567.pdf Primordial black hole constraints for extended mass functions (2017)] (That this is a common practice in cosmology may be part of the reference to "buzzkill" astronomers.) He rules out all black holes in the range of approximately 1010 kg to 1033 kg even when below some gaps at the bars appear.

Except the last item, all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four solar masses.
* Gamma rays: If dark matter were black holes of this size, the black holes could be evaporating by the predicted {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction if many of those objects would exist. Nonetheless this radiation is still hypothetical and not been observed on any known black holes. Furthermore those objects would be very small because the Schwarzschild radius of a 1012 kg black hole is approximately 148 fm (1.48×10−13 m), which is between the size of an atom and an atomic nucleus.
* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe and have been observed only in distant galaxies. While gravitational microlensing (see below) is an astronomical phenomenon, it doesn't make much sense here. GRBs are short (milliseconds to several hours) and are often detected only by space-borne sensors for gamma-rays -- rarely at any other wavelengths. Measuring lensing effects would be very difficult. This [https://arxiv.org/abs/1406.3102 paper] discusses the probability of detecting lensing effects caused by {{w|Dark matter halo|galactic halo objects}} among the known GRBs given sufficient objects to represent the missing mass.
* Neutron star data: {{w|Neutron star|Neutron stars}} aren't black holes, but they're also very small highly compact objects at about 1.4-2.16 solar masses. While black holes can't be observed directly, neutron stars are detectable in many wavelengths. The number of them gives a clue about the number of black holes close to the mass of the sun, a number which is far too low to make up dark matter.
* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect, (the path of radiation is changed by passing through space bent by nearby mass). This was predicted by Einstein's {{w|General Relativity|Theory of General Relativity}} and was first confirmed in 1919 during a solar eclipse, when a star which was nearly in line with the sun appeared more distant to the sun than usual. Astronomers have found many so called {{w|Einstein ring|Einstein rings}} or Einstein crosses where a massive object in front of other galaxies bends the light toward us. Those massive objects may be black holes, but the number is far too low to explain dark matter.
* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and has been very stable since shortly after its formation. If not, we wouldn't exist. If dark objects at 1024 kg - 1030 kg (mass of Earth up to mass of Sun) accounted for dark matter and were distributed throughout galaxies, there should be many of them in the vicinity of our solar system and the system wouldn't be stable at all.
* Buzzkill Astronomers: Black holes above a certain size are thought by some astronomers to be impossible to miss, due to the effects they have on nearby matter. At the mass of some 1030 kg there must be many supernova remnants we still haven't found. Black holes of about 1035 kg have long been considered dark matter candidates by a minority group of cosmologists, as could be seen here [https://arxiv.org/pdf/1001.2308.pdf Primordial Black Holes as All Dark Matter (2010)] and the Milky Way's first discovered intermediate mass black hole falling in this range shown here [https://www.nao.ac.jp/en/news/science/2016/20160115-nro.html Signs of Second Largest Black Hole in the Milky Way].
Not covered by this comic are {{w|Massive compact halo object|massive astrophysical compact halo objects (MACHOs)}} composed of hard to detect dim objects like black holes, neutron stars, brown dwarfs, and other objects composed of normal {{w|Baryon|baryonic}} matter. Nevertheless observations have shown that the total amount of baryonic matter in our universe on large scales is much smaller than it would be needed to explain all the measured gravitational effects.

==== Maybe those orbit lines on space diagrams are real and very heavy ====
Diagrams of our solar system (or any planetary system) often show lines representing the elliptical paths the planet takes around its sun. These lines don't show real objects, though. Astronomers just draw them on pictures of the solar system to show where the planets move. If you draw a line on a map to give someone directions, that line isn't an object in real life; it's just on the map. If these lines were real, they would be ''huge'' (Earth's would be 940 million km long (2π AU) and Neptune's would be 28 ''billion'' kilometers long). [https://www.youtube.com/watch?v=0fKBhvDjuy0 Powers of Ten (1977)] gives a good sense of just how large these orbit lines need to be in order to be visible in space diagrams. If these orbit lines were also very dense, they would have a huge mass and could possibly account for the missing 85% of the mass in the universe. But they would also constantly be impaling the planets, including the Earth, which would probably be a problem. Their mass would also affect planetary motions in ways which we would detect. A related worry about space travel was expressed in previous centuries; it was thought that the planets were embedded within {{w|Celestial spheres|crystal shells}} (spheres or Platonic solids), and a rocket into space could smash the shells and send planets plummeting to Earth. Another joke candidate.

Due to Gauss' shell theorem the orbit lines wouldn't contribute to gravitational binding energy of the orbiting bodies. As a result the systems would be unstable and would "Boil off". Consider the innermost orbiting body, since there is not enough observable mass to bind that body there must be dark matter, but no mass contribution comes from its own orbit line hence it escapes, now the second closest body has even less mass binding it so that body will also escape, by induction no body can be bound by massive orbit lines.

==== Title text ====
The title text refers to the fact that space is just vast emptiness where a little bit of dirt could be overlooked. Actually the mean density of detectable matter in the universe, according to NASA, is equivalent to roughly [https://map.gsfc.nasa.gov/universe/uni_matter.html 1 proton per 4 cubic meters]. And because this matter is mostly located in galaxies -- and inside there in stars and clouds -- the space between is even more empty. For comparison, one gram hydrogen consists of {{w|Avogadro constant|6.022 x 1023 atoms}}. Like at home wiping with a cleaning cloth in which we can see the dirt that wasn't clearly visible on the surface we have wiped, Randall believes that some few atoms more per cubic meter could stay undetected in the same way. This isn't true because in the space between galaxies astronomers can detect matter as it spreads over thousands or millions cubic light years. Atoms can't hide; there is always radiation.

==Transcript==
:Dark matter candidates:
:[A line graph is shown and labeled at left quarter in eV and further to the right in g together with some prefixes.]
:[The labels read:]
:µeV, meV, eV, keV, MeV, GeV, TeV, 10-18kg, ng, µg, mg, g, kg, TON, 106kg, 1012kg, 1018kg, 1024kg, 1030kg

:[All items are shown in bars ranging between two approximately values:]
:< 1 µeV - 10 meV: Axion

:1 eV - 10 keV: Sterile neutrino

:0.5 MeV (exactly): Electrons painted with space camouflage

:10 GeV - 10 TeV: Neutralino

:100 TeV - 10-17 kg: Q-ball

:1 ng - 100 ng: Pollen

:0.1 mg - 1 mg: No-See-Ums

:10-1 g (exactly): Bees

:10 g - 100 g: 8-balls

:100 kg - TON: Space cows

:TON - 109 kg: Obelisks, monoliths, pyramids

:109 kg - 1033 kg: Black holes ruled out by:
::109 kg - 1013 kg: Gamma rays
::1013 kg - 1017 kg: GRB lensing
::1015 kg - 1022 kg: Neutron star data
::1021 kg - 1030 kg: Micro lensing
::1024 kg - 1030 kg: Solar system stability
::1030 kg - 1033 kg: Buzzkill astronomers

:1033 kg - >1036 kg: Maybe those orbit lines on space diagrams are real and very heavy

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Line graphs]]

2035: Dark Matter Candidates

2018-10-03T08:14:24Z

162.158.93.27: /* Maybe those orbit lines on space diagrams are real and very heavy */

{{comic
| number = 2035
| date = August 20, 2018
| title = Dark Matter Candidates
| image = dark_matter_candidates.png
| titletext = My theory is that dark matter is actually just a thin patina of grime covering the whole universe, and we don't notice it because we haven't thoroughly cleaned the place in eons.
}}

==Explanation==
{{w|Dark matter}} is a hypothetical, invisible form of matter used by the vast majority of astronomers to explain the far too high apparent mass of objects at large scales in our universe. In galaxies, stars are orbiting faster than the gravitational force of the sum of the masses of visible matter in the galaxy could cause, and entire galaxies are observed moving much faster around each other than their visible masses could explain. In galactic collisions, the mass can appear to separate from the visible matter, as if the mass doesn't collide but the visible matter does. A small handful of galaxies have been observed to not have this property, suggesting that it is a *thing* that a galaxy can have more or less of and is separable from. At scales of our solar system, those effects are too small and can't be measured. The most plausible explanation for all of these phenomena is that there is some "dark matter" that has gravity, but is otherwise undetectable. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities for what dark matter could possibly be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10-15 kg to 10-3 kg are given in grams together with appropriate prefixes, while the ton takes the place of 103 kg.

Only massive objects ranging from subatomic particles up to super massive ones are covered in this comic. There are also {{w|Dark matter#Alternative hypotheses|alternative hypotheses}} trying to modify general relativity with no need of additional matter. The problem is that these theories can't explain all different observations at once. Nonetheless dark matter is a mystery because no serious candidate has been found yet.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten, with explanations suggested by astronomers covering only some portions of that range. [[Randall]] fills the gaps with highly absurd suggestions.

==== Axion ====
An {{w|Axion|axion}} is a hypothetical elementary particle postulated in 1977 to resolve the strong CP problem in {{w|Quantum chromodynamics|quantum chromodynamics}}, a theory of the strong force between {{w|Quark|quarks}} and {{w|Gluon|gluons}} which form {{w|Hadron|hadrons}} like {{w|Proton|protons}} or {{w|Neutron|neutrons}}. If axions exist within a specific range of mass they might be a component of dark matter. The advantage of this particle is that it's based on a theory which could be proved or also disproved by measurements in the future. Other theories, not mentioned in this comic, like the {{w|Weakly interacting massive particles|Weakly interacting massive particles (WIMPs)}} are much more vague.

==== Sterile neutrino ====
{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter. The well known {{w|Neutrino|neutrinos}} are also charged under the {{w|Weak interaction|weak interaction}} and can be detected by experiments.

==== Electrons painted with space camouflage ====
{{w|Electron|Electrons}} are fundamental particles which compose the outer layers of atoms. A large number of electrons in the galaxy would be relatively easy to detect, as they not only interact with light (which dark matter does not appear to), but also have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say, this is not an actual candidate for dark matter.) The mass of an electron is about 0.5 MeV which fits well into the graph.

==== Neutralino ====
A {{w|Neutralino|neutralino}} is a hypothetical particle from {{w|Supersymmetry|supersymmetry}} and is also a current candidate for dark matter. But there is not evidence whether or not supersymmetry is correct and none of the predicted particles have been found yet.

==== Q-ball ====
In theoretical physics, a {{w|Q-ball}} is a stable group of particles. It's an actual candidate for dark matter.

(In billiards, a cue ball is the white (or yellow) ball hit with the cue in normal play. In addition, [[Cueball]] is the name explainxkcd uses for the most common xkcd character.)

==== Pollen ====
{{w|Pollen}} is a joke candidate, though people with seasonal allergies may suspect that the universe is genuinely made up entirely of pollen in the springtime.

==== No-See-Ums ====
{{w|Ceratopogonidae|No-See-Ums}} are a family (Ceratopogonidae) of small flies, 1–4 mm long, that can pass through most window screens. Another joke candidate, because dark matter is invisible and the name "no-see-ums" implies that the flies are invisible.

==== Bees ====
Insects of the clade {{w|Bee|Antophila}} are major pollinators of flowering plants. In recent years {{w|Colony collapse disorder|bees have been disappearing}} at an alarming rate; {{w|The Stolen Earth|Doctor Who explained}} that they are in fact aliens leaving Earth prior to a Dalek invasion.

==== 8-balls ====
In pool, the {{w|Pool (cue sports)|8-ball}} is a black ball numbered 8. It's a pun with Q-ball/cue ball. Unless undetected aliens have discovered billiards and become addicted to it, 8-balls are found only on Earth and are, hence, unlikely dark matter candidates. The 8-ball is also a popular unit of sale for black market pharmaceuticals like cocaine, where it stands for 1/8th of an ounce (3.5g). This doesn't make sense as a dark matter candidate either -- unless dark matter is hard to detect because it's illegal & trying to avoid the cops.

==== Space Cows ====
Cows are {{w|Bovinae|bovines}} extensively farmed on Earth for milk and meat. Although there is folklore concerning cows {{w|Hey diddle diddle|achieving circum-lunar orbits}}, not to mention their appearance on a {{w|Shindig (Firefly)|beloved space western TV show}}, as Muppet cow [http://muppet.wikia.com/wiki/Natalie Natalie] in the Sesame Street News Flash (and [https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWestern others less-remembered]), they have yet to be found elsewhere in the Universe. In the television show "Too Close for Comfort", one of the characters is the cartoonist of a comic strip called "Cosmic Cow". {{w|Spherical cow|Spherical cows}} have also been used (humorously) by physicists needing to simplify some source of mass in a given problem.

==== Obelisks, Monoliths, Pyramids ====
While those human constructions are huge on a human scale, they're negligible at universe-scale. It would take a large number of such constructions, distributed through space, to replicate the effects of dark matter; while a scenario could be envisioned where enough such constructs existed, with properties and distribution allowing them to match observations, this is obviously not a likely explanation.
They often show up in fiction and pseudo-scientific literature as alien artifacts generating immense unknown power out of nowhere, with the most famous and influential example being the three monoliths from {{w|2001: A Space Odyssey (film)|2001: A Space Odyssey}} (with the largest having a mass of about 500,000 tonnes).

==== Black Holes ruled out by: ====
{{w|Black hole|Black holes}} are known to occur in sizes of a few solar masses (about 1030-1031 kg) as remnants of the core of former big stars, as well as in quite large sizes at the centers of galaxies (millions or even billions of solar masses). But recent gravitational wave detections indicate that black holes at 50 or 100 solar masses also exist, though their origin is still not understood. Randall doesn't mention this but some astronomers hope that these could fill at least a part of the gap. While black holes are widely reported to be ruled out as a candidate for dark matter for various reasons Randall has listed, such constraints are based on "monochromatic" mass distributions -- meaning that all such black holes are assumed to have the same mass -- which is considered physically implausible for populations of merging bodies which are known to have vastly different masses. See: [https://arxiv.org/pdf/1709.07467.pdf Primordial Black Holes as Dark Matter (2017)] and [https://arxiv.org/pdf/1705.05567.pdf Primordial black hole constraints for extended mass functions (2017)] (That this is a common practice in cosmology may be part of the reference to "buzzkill" astronomers.) He rules out all black holes in the range of approximately 1010 kg to 1033 kg even when below some gaps at the bars appear.

Except the last item, all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four solar masses.
* Gamma rays: If dark matter were black holes of this size, the black holes could be evaporating by the predicted {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction if many of those objects would exist. Nonetheless this radiation is still hypothetical and not been observed on any known black holes. Furthermore those objects would be very small because the Schwarzschild radius of a 1012 kg black hole is approximately 148 fm (1.48×10−13 m), which is between the size of an atom and an atomic nucleus.
* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe and have been observed only in distant galaxies. While gravitational microlensing (see below) is an astronomical phenomenon, it doesn't make much sense here. GRBs are short (milliseconds to several hours) and are often detected only by space-borne sensors for gamma-rays -- rarely at any other wavelengths. Measuring lensing effects would be very difficult. This [https://arxiv.org/abs/1406.3102 paper] discusses the probability of detecting lensing effects caused by {{w|Dark matter halo|galactic halo objects}} among the known GRBs given sufficient objects to represent the missing mass.
* Neutron star data: {{w|Neutron star|Neutron stars}} aren't black holes, but they're also very small highly compact objects at about 1.4-2.16 solar masses. While black holes can't be observed directly, neutron stars are detectable in many wavelengths. The number of them gives a clue about the number of black holes close to the mass of the sun, a number which is far too low to make up dark matter.
* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect, (the path of radiation is changed by passing through space bent by nearby mass). This was predicted by Einstein's {{w|General Relativity|Theory of General Relativity}} and was first confirmed in 1919 during a solar eclipse, when a star which was nearly in line with the sun appeared more distant to the sun than usual. Astronomers have found many so called {{w|Einstein ring|Einstein rings}} or Einstein crosses where a massive object in front of other galaxies bends the light toward us. Those massive objects may be black holes, but the number is far too low to explain dark matter.
* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and has been very stable since shortly after its formation. If not, we wouldn't exist. If dark objects at 1024 kg - 1030 kg (mass of Earth up to mass of Sun) accounted for dark matter and were distributed throughout galaxies, there should be many of them in the vicinity of our solar system and the system wouldn't be stable at all.
* Buzzkill Astronomers: Black holes above a certain size are thought by some astronomers to be impossible to miss, due to the effects they have on nearby matter. At the mass of some 1030 kg there must be many supernova remnants we still haven't found. Black holes of about 1035 kg have long been considered dark matter candidates by a minority group of cosmologists, as could be seen here [https://arxiv.org/pdf/1001.2308.pdf Primordial Black Holes as All Dark Matter (2010)] and the Milky Way's first discovered intermediate mass black hole falling in this range shown here [https://www.nao.ac.jp/en/news/science/2016/20160115-nro.html Signs of Second Largest Black Hole in the Milky Way].
Not covered by this comic are {{w|Massive compact halo object|massive astrophysical compact halo objects (MACHOs)}} composed of hard to detect dim objects like black holes, neutron stars, brown dwarfs, and other objects composed of normal {{w|Baryon|baryonic}} matter. Nevertheless observations have shown that the total amount of baryonic matter in our universe on large scales is much smaller than it would be needed to explain all the measured gravitational effects.

==== Maybe those orbit lines on space diagrams are real and very heavy ====
Diagrams of our solar system (or any planetary system) often show lines representing the elliptical paths the planet takes around its sun. These lines don't show real objects, though. Astronomers just draw them on pictures of the solar system to show where the planets move. If you draw a line on a map to give someone directions, that line isn't an object in real life; it's just on the map. If these lines were real, they would be ''huge'' (Earth's would be 940 million km long (2π AU) and Neptune's would be 28 ''billion'' kilometers long). [https://www.youtube.com/watch?v=0fKBhvDjuy0 Powers of Ten (1977)] gives a good sense of just how large these orbit lines need to be in order to be visible in space diagrams. If these orbit lines were also very dense, they would have a huge mass and could possibly account for the missing 85% of the mass in the universe. But they would also constantly be impaling the planets, including the Earth, which would probably be a problem. Their mass would also affect planetary motions in ways which we would detect. A related worry about space travel was expressed in previous centuries; it was thought that the planets were embedded within {{w|Celestial spheres|crystal shells}} (spheres or Platonic solids), and a rocket into space could smash the shells and send planets plummeting to Earth. Another joke candidate.

Due to Gauss' shell theorem the orbit lines wouldn't contribute to gravitational binding energy of the orbiting bodies. As a result the systems would be unstable and ould "Boil off". Consider the innermost orbiting body, since there is not enough observable mass to bind that body there must be dark matter, but no mass contribution comes from its own orbit line hence it escapes, now the second closest body has even less mass binding it so that body will also escape, by induction no body can be bound by massive orbit lines.

==== Title text ====
The title text refers to the fact that space is just vast emptiness where a little bit of dirt could be overlooked. Actually the mean density of detectable matter in the universe, according to NASA, is equivalent to roughly [https://map.gsfc.nasa.gov/universe/uni_matter.html 1 proton per 4 cubic meters]. And because this matter is mostly located in galaxies -- and inside there in stars and clouds -- the space between is even more empty. For comparison, one gram hydrogen consists of {{w|Avogadro constant|6.022 x 1023 atoms}}. Like at home wiping with a cleaning cloth in which we can see the dirt that wasn't clearly visible on the surface we have wiped, Randall believes that some few atoms more per cubic meter could stay undetected in the same way. This isn't true because in the space between galaxies astronomers can detect matter as it spreads over thousands or millions cubic light years. Atoms can't hide; there is always radiation.

==Transcript==
:Dark matter candidates:
:[A line graph is shown and labeled at left quarter in eV and further to the right in g together with some prefixes.]
:[The labels read:]
:µeV, meV, eV, keV, MeV, GeV, TeV, 10-18kg, ng, µg, mg, g, kg, TON, 106kg, 1012kg, 1018kg, 1024kg, 1030kg

:[All items are shown in bars ranging between two approximately values:]
:< 1 µeV - 10 meV: Axion

:1 eV - 10 keV: Sterile neutrino

:0.5 MeV (exactly): Electrons painted with space camouflage

:10 GeV - 10 TeV: Neutralino

:100 TeV - 10-17 kg: Q-ball

:1 ng - 100 ng: Pollen

:0.1 mg - 1 mg: No-See-Ums

:10-1 g (exactly): Bees

:10 g - 100 g: 8-balls

:100 kg - TON: Space cows

:TON - 109 kg: Obelisks, monoliths, pyramids

:109 kg - 1033 kg: Black holes ruled out by:
::109 kg - 1013 kg: Gamma rays
::1013 kg - 1017 kg: GRB lensing
::1015 kg - 1022 kg: Neutron star data
::1021 kg - 1030 kg: Micro lensing
::1024 kg - 1030 kg: Solar system stability
::1030 kg - 1033 kg: Buzzkill astronomers

:1033 kg - >1036 kg: Maybe those orbit lines on space diagrams are real and very heavy

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Line graphs]]

2035: Dark Matter Candidates

2018-10-03T08:10:57Z

162.158.93.27: /* Maybe those orbit lines on space diagrams are real and very heavy */

{{comic
| number = 2035
| date = August 20, 2018
| title = Dark Matter Candidates
| image = dark_matter_candidates.png
| titletext = My theory is that dark matter is actually just a thin patina of grime covering the whole universe, and we don't notice it because we haven't thoroughly cleaned the place in eons.
}}

==Explanation==
{{w|Dark matter}} is a hypothetical, invisible form of matter used by the vast majority of astronomers to explain the far too high apparent mass of objects at large scales in our universe. In galaxies, stars are orbiting faster than the gravitational force of the sum of the masses of visible matter in the galaxy could cause, and entire galaxies are observed moving much faster around each other than their visible masses could explain. In galactic collisions, the mass can appear to separate from the visible matter, as if the mass doesn't collide but the visible matter does. A small handful of galaxies have been observed to not have this property, suggesting that it is a *thing* that a galaxy can have more or less of and is separable from. At scales of our solar system, those effects are too small and can't be measured. The most plausible explanation for all of these phenomena is that there is some "dark matter" that has gravity, but is otherwise undetectable. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities for what dark matter could possibly be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10-15 kg to 10-3 kg are given in grams together with appropriate prefixes, while the ton takes the place of 103 kg.

Only massive objects ranging from subatomic particles up to super massive ones are covered in this comic. There are also {{w|Dark matter#Alternative hypotheses|alternative hypotheses}} trying to modify general relativity with no need of additional matter. The problem is that these theories can't explain all different observations at once. Nonetheless dark matter is a mystery because no serious candidate has been found yet.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten, with explanations suggested by astronomers covering only some portions of that range. [[Randall]] fills the gaps with highly absurd suggestions.

==== Axion ====
An {{w|Axion|axion}} is a hypothetical elementary particle postulated in 1977 to resolve the strong CP problem in {{w|Quantum chromodynamics|quantum chromodynamics}}, a theory of the strong force between {{w|Quark|quarks}} and {{w|Gluon|gluons}} which form {{w|Hadron|hadrons}} like {{w|Proton|protons}} or {{w|Neutron|neutrons}}. If axions exist within a specific range of mass they might be a component of dark matter. The advantage of this particle is that it's based on a theory which could be proved or also disproved by measurements in the future. Other theories, not mentioned in this comic, like the {{w|Weakly interacting massive particles|Weakly interacting massive particles (WIMPs)}} are much more vague.

==== Sterile neutrino ====
{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter. The well known {{w|Neutrino|neutrinos}} are also charged under the {{w|Weak interaction|weak interaction}} and can be detected by experiments.

==== Electrons painted with space camouflage ====
{{w|Electron|Electrons}} are fundamental particles which compose the outer layers of atoms. A large number of electrons in the galaxy would be relatively easy to detect, as they not only interact with light (which dark matter does not appear to), but also have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say, this is not an actual candidate for dark matter.) The mass of an electron is about 0.5 MeV which fits well into the graph.

==== Neutralino ====
A {{w|Neutralino|neutralino}} is a hypothetical particle from {{w|Supersymmetry|supersymmetry}} and is also a current candidate for dark matter. But there is not evidence whether or not supersymmetry is correct and none of the predicted particles have been found yet.

==== Q-ball ====
In theoretical physics, a {{w|Q-ball}} is a stable group of particles. It's an actual candidate for dark matter.

(In billiards, a cue ball is the white (or yellow) ball hit with the cue in normal play. In addition, [[Cueball]] is the name explainxkcd uses for the most common xkcd character.)

==== Pollen ====
{{w|Pollen}} is a joke candidate, though people with seasonal allergies may suspect that the universe is genuinely made up entirely of pollen in the springtime.

==== No-See-Ums ====
{{w|Ceratopogonidae|No-See-Ums}} are a family (Ceratopogonidae) of small flies, 1–4 mm long, that can pass through most window screens. Another joke candidate, because dark matter is invisible and the name "no-see-ums" implies that the flies are invisible.

==== Bees ====
Insects of the clade {{w|Bee|Antophila}} are major pollinators of flowering plants. In recent years {{w|Colony collapse disorder|bees have been disappearing}} at an alarming rate; {{w|The Stolen Earth|Doctor Who explained}} that they are in fact aliens leaving Earth prior to a Dalek invasion.

==== 8-balls ====
In pool, the {{w|Pool (cue sports)|8-ball}} is a black ball numbered 8. It's a pun with Q-ball/cue ball. Unless undetected aliens have discovered billiards and become addicted to it, 8-balls are found only on Earth and are, hence, unlikely dark matter candidates. The 8-ball is also a popular unit of sale for black market pharmaceuticals like cocaine, where it stands for 1/8th of an ounce (3.5g). This doesn't make sense as a dark matter candidate either -- unless dark matter is hard to detect because it's illegal & trying to avoid the cops.

==== Space Cows ====
Cows are {{w|Bovinae|bovines}} extensively farmed on Earth for milk and meat. Although there is folklore concerning cows {{w|Hey diddle diddle|achieving circum-lunar orbits}}, not to mention their appearance on a {{w|Shindig (Firefly)|beloved space western TV show}}, as Muppet cow [http://muppet.wikia.com/wiki/Natalie Natalie] in the Sesame Street News Flash (and [https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWestern others less-remembered]), they have yet to be found elsewhere in the Universe. In the television show "Too Close for Comfort", one of the characters is the cartoonist of a comic strip called "Cosmic Cow". {{w|Spherical cow|Spherical cows}} have also been used (humorously) by physicists needing to simplify some source of mass in a given problem.

==== Obelisks, Monoliths, Pyramids ====
While those human constructions are huge on a human scale, they're negligible at universe-scale. It would take a large number of such constructions, distributed through space, to replicate the effects of dark matter; while a scenario could be envisioned where enough such constructs existed, with properties and distribution allowing them to match observations, this is obviously not a likely explanation.
They often show up in fiction and pseudo-scientific literature as alien artifacts generating immense unknown power out of nowhere, with the most famous and influential example being the three monoliths from {{w|2001: A Space Odyssey (film)|2001: A Space Odyssey}} (with the largest having a mass of about 500,000 tonnes).

==== Black Holes ruled out by: ====
{{w|Black hole|Black holes}} are known to occur in sizes of a few solar masses (about 1030-1031 kg) as remnants of the core of former big stars, as well as in quite large sizes at the centers of galaxies (millions or even billions of solar masses). But recent gravitational wave detections indicate that black holes at 50 or 100 solar masses also exist, though their origin is still not understood. Randall doesn't mention this but some astronomers hope that these could fill at least a part of the gap. While black holes are widely reported to be ruled out as a candidate for dark matter for various reasons Randall has listed, such constraints are based on "monochromatic" mass distributions -- meaning that all such black holes are assumed to have the same mass -- which is considered physically implausible for populations of merging bodies which are known to have vastly different masses. See: [https://arxiv.org/pdf/1709.07467.pdf Primordial Black Holes as Dark Matter (2017)] and [https://arxiv.org/pdf/1705.05567.pdf Primordial black hole constraints for extended mass functions (2017)] (That this is a common practice in cosmology may be part of the reference to "buzzkill" astronomers.) He rules out all black holes in the range of approximately 1010 kg to 1033 kg even when below some gaps at the bars appear.

Except the last item, all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four solar masses.
* Gamma rays: If dark matter were black holes of this size, the black holes could be evaporating by the predicted {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction if many of those objects would exist. Nonetheless this radiation is still hypothetical and not been observed on any known black holes. Furthermore those objects would be very small because the Schwarzschild radius of a 1012 kg black hole is approximately 148 fm (1.48×10−13 m), which is between the size of an atom and an atomic nucleus.
* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe and have been observed only in distant galaxies. While gravitational microlensing (see below) is an astronomical phenomenon, it doesn't make much sense here. GRBs are short (milliseconds to several hours) and are often detected only by space-borne sensors for gamma-rays -- rarely at any other wavelengths. Measuring lensing effects would be very difficult. This [https://arxiv.org/abs/1406.3102 paper] discusses the probability of detecting lensing effects caused by {{w|Dark matter halo|galactic halo objects}} among the known GRBs given sufficient objects to represent the missing mass.
* Neutron star data: {{w|Neutron star|Neutron stars}} aren't black holes, but they're also very small highly compact objects at about 1.4-2.16 solar masses. While black holes can't be observed directly, neutron stars are detectable in many wavelengths. The number of them gives a clue about the number of black holes close to the mass of the sun, a number which is far too low to make up dark matter.
* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect, (the path of radiation is changed by passing through space bent by nearby mass). This was predicted by Einstein's {{w|General Relativity|Theory of General Relativity}} and was first confirmed in 1919 during a solar eclipse, when a star which was nearly in line with the sun appeared more distant to the sun than usual. Astronomers have found many so called {{w|Einstein ring|Einstein rings}} or Einstein crosses where a massive object in front of other galaxies bends the light toward us. Those massive objects may be black holes, but the number is far too low to explain dark matter.
* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and has been very stable since shortly after its formation. If not, we wouldn't exist. If dark objects at 1024 kg - 1030 kg (mass of Earth up to mass of Sun) accounted for dark matter and were distributed throughout galaxies, there should be many of them in the vicinity of our solar system and the system wouldn't be stable at all.
* Buzzkill Astronomers: Black holes above a certain size are thought by some astronomers to be impossible to miss, due to the effects they have on nearby matter. At the mass of some 1030 kg there must be many supernova remnants we still haven't found. Black holes of about 1035 kg have long been considered dark matter candidates by a minority group of cosmologists, as could be seen here [https://arxiv.org/pdf/1001.2308.pdf Primordial Black Holes as All Dark Matter (2010)] and the Milky Way's first discovered intermediate mass black hole falling in this range shown here [https://www.nao.ac.jp/en/news/science/2016/20160115-nro.html Signs of Second Largest Black Hole in the Milky Way].
Not covered by this comic are {{w|Massive compact halo object|massive astrophysical compact halo objects (MACHOs)}} composed of hard to detect dim objects like black holes, neutron stars, brown dwarfs, and other objects composed of normal {{w|Baryon|baryonic}} matter. Nevertheless observations have shown that the total amount of baryonic matter in our universe on large scales is much smaller than it would be needed to explain all the measured gravitational effects.

==== Maybe those orbit lines on space diagrams are real and very heavy ====
Diagrams of our solar system (or any planetary system) often show lines representing the elliptical paths the planet takes around its sun. These lines don't show real objects, though. Astronomers just draw them on pictures of the solar system to show where the planets move. If you draw a line on a map to give someone directions, that line isn't an object in real life; it's just on the map. If these lines were real, they would be ''huge'' (Earth's would be 940 million km long (2π AU) and Neptune's would be 28 ''billion'' kilometers long). [https://www.youtube.com/watch?v=0fKBhvDjuy0 Powers of Ten (1977)] gives a good sense of just how large these orbit lines need to be in order to be visible in space diagrams. If these orbit lines were also very dense, they would have a huge mass and could possibly account for the missing 85% of the mass in the universe. But they would also constantly be impaling the planets, including the Earth, which would probably be a problem. Their mass would also affect planetary motions in ways which we would detect. A related worry about space travel was expressed in previous centuries; it was thought that the planets were embedded within {{w|Celestial spheres|crystal shells}} (spheres or Platonic solids), and a rocket into space could smash the shells and send planets plummeting to Earth. Another joke candidate.

Due to Gauss' shell theorem the orbit lines wouldn't contribute to gravitational binding energy of the orbiting bodies.
As a result the systems would be unstable and ould "Boil off". Consider the innermost orbiting body, since there is not enough observable mass to bind that body there must be dark matter, but no mass contribution comes from its own orbit line hence it escapes, now the second closest body has even less mass binding it so that body will also escape, by induction no body can be bound by massive orbit lines.

==== Title text ====
The title text refers to the fact that space is just vast emptiness where a little bit of dirt could be overlooked. Actually the mean density of detectable matter in the universe, according to NASA, is equivalent to roughly [https://map.gsfc.nasa.gov/universe/uni_matter.html 1 proton per 4 cubic meters]. And because this matter is mostly located in galaxies -- and inside there in stars and clouds -- the space between is even more empty. For comparison, one gram hydrogen consists of {{w|Avogadro constant|6.022 x 1023 atoms}}. Like at home wiping with a cleaning cloth in which we can see the dirt that wasn't clearly visible on the surface we have wiped, Randall believes that some few atoms more per cubic meter could stay undetected in the same way. This isn't true because in the space between galaxies astronomers can detect matter as it spreads over thousands or millions cubic light years. Atoms can't hide; there is always radiation.

==Transcript==
:Dark matter candidates:
:[A line graph is shown and labeled at left quarter in eV and further to the right in g together with some prefixes.]
:[The labels read:]
:µeV, meV, eV, keV, MeV, GeV, TeV, 10-18kg, ng, µg, mg, g, kg, TON, 106kg, 1012kg, 1018kg, 1024kg, 1030kg

:[All items are shown in bars ranging between two approximately values:]
:< 1 µeV - 10 meV: Axion

:1 eV - 10 keV: Sterile neutrino

:0.5 MeV (exactly): Electrons painted with space camouflage

:10 GeV - 10 TeV: Neutralino

:100 TeV - 10-17 kg: Q-ball

:1 ng - 100 ng: Pollen

:0.1 mg - 1 mg: No-See-Ums

:10-1 g (exactly): Bees

:10 g - 100 g: 8-balls

:100 kg - TON: Space cows

:TON - 109 kg: Obelisks, monoliths, pyramids

:109 kg - 1033 kg: Black holes ruled out by:
::109 kg - 1013 kg: Gamma rays
::1013 kg - 1017 kg: GRB lensing
::1015 kg - 1022 kg: Neutron star data
::1021 kg - 1030 kg: Micro lensing
::1024 kg - 1030 kg: Solar system stability
::1030 kg - 1033 kg: Buzzkill astronomers

:1033 kg - >1036 kg: Maybe those orbit lines on space diagrams are real and very heavy

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Line graphs]]