explain xkcd - User contributions [en]

Talk:875: 2009 Called

2026-02-07T21:04:23Z

Jjj: Add comment

I was too busy trading fashion tips, and they hung up before I could tell them. '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 00:38, 11 January 2013 (UTC)

The '90s called. They wanted my pogs back. But, due to inflation, they couldn't offer me enough money for me to be willing to sell. I told them my friend, Oscar, has some Pokémon stuff, but the '90s had no interest in that crap. I made the right choice to choose pogs over Pokémon. Society made the wrong one. But, I digress. The '90s are doing rather well, and they miss us.[[Special:Contributions/76.29.225.28|76.29.225.28]] 18:20, 14 July 2013 (UTC)
:The only Pokémon stuff I ever had was a bunch of pogs, so... --[[Special:Contributions/172.68.10.172|172.68.10.172]] 18:26, 31 December 2016 (UTC)

2017 called, but I couldn't understand what they were saying over all the screams. I bet it was something about them being attacked by 4 Replicants. [[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 23:49, 23 January 2015 (UTC)

Well, that title text is feeling pretty prophetic now...[[Special:Contributions/141.101.98.185|141.101.98.185]] 00:08, 12 November 2016 (UTC)

'''Hello it's 2017, please send help.''' [[Special:Contributions/108.162.237.202|108.162.237.202]] 21:23, 7 February 2017 (UTC)
:This is 2018 calling in, you'll be alright on your own. At least for the time being. --[[Special:Contributions/108.162.241.130|108.162.241.130]] 05:05, 14 January 2018 (UTC)
::2020 here. We're hosed. [[Special:Contributions/172.68.189.127|172.68.189.127]] 20:52, 6 April 2020 (UTC)
:::2021 says, I miss 2020, please send time machine[[Special:Contributions/172.70.206.205|172.70.206.205]] 03:13, 27 November 2021
::::2022 says, oh my god send help Covid is playing mix-and-match. 1:53, 1 Apr 2022 (UTC)
:::::2023 here, no comment. [[Special:Contributions/162.158.35.8|162.158.35.8]] 13:10, 13 November 2023 (UTC)
::::::2024 here, MatPat's gone and that war is still ongoing. --[[Special:Contributions/172.69.79.130|172.69.79.130]] 08:18, 11 March 2024 (UTC)
:::::::2025 calling in. There's another war now. But the RTX 5090 is cool.
::::::::2026 here. We, um. Yeah... --[[User:Jjj|Jjj]] ([[User talk:Jjj|talk]]) 21:04, 7 February 2026 (UTC)
This now stands as a piece of horrifying foreshadowing. Seriously, we're barely in april and things alredy look terrifying. I blame Randall for everything. {{unsigned ip|198.41.226.124}}

The screaming in 2017 was just an echo of everybody's collective screams from 2016 when almost everybody's favorite musician or celebrity died. We now refer to it as 'The Year Who's Number Shall Not be Spoken' [[Special:Contributions/172.69.68.225|172.69.68.225]] 05:59, 15 February 2018 (UTC)

The explanation mentioned Trump, but it doesn't actually attack him too much. Good. We don't need all the Trump hate here. [[Special:Contributions/162.158.74.165|162.158.74.165]] 22:28, 25 September 2018 (UTC)
:I've removed the sentence because Randall is no clairvoyant. This comic is from 2011 and 2017 was not only a Trump year. And guessing about Clinton doesn't explain the comic at all. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 19:01, 27 September 2018 (UTC)
::Shouldn't there be a {{Citation needed}} after the statement that Randall isn't clairvoyant? --[[Special:Contributions/108.162.210.214|108.162.210.214]] 20:41, 6 January 2020 (UTC)
:::Well, clearly, he isn't. I mean, he was off by three whole years! But I guess you didn't know that, did you, 108.162.210.214 20:41 6 January 2020 (UTC)? [[Special:Contributions/162.158.62.75|162.158.62.75]] 14:19, 8 June 2020 (UTC)
::::The notion that 2017 was a bad year seems comical in retrospect. I suspect by this time next year, we will feel the same way about 2020.
::::For the benefit of anyone reading this far enough in the future that the topical reference isn't obvious: There's a new virus and half a million people have died so far. It is still increasing exponentially. If you didn't hear about it it's because whatever happens after this is worse, probably. {{unsigned|Singlelinelabyrinth}}
:::::It's also possible that person reading it from future would still consider 2020 bad but for different reason. After all, historically speaking, the epidemic is not THAT bad (yet): it just shows how unprepared we were for it despite thinking otherwise. Just now, I'm little worried about how big temperature {{w|Donald Trump|the person currently in charge of US nuclear weapons}} has. Sure, they SAY [https://www.bbc.com/news/election-us-2020-54427390 he's getting better] ... I still think he should've transfer the codes to {{w|Mike Pence|vicepresident}} at least for time he was in hospital. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 03:10, 6 October 2020 (UTC)
::::::1) *pandemic, 2) ??! Not that bad? Over twice as many people have died in the United States from COVID-19 than those who fought in World War I! I get that, with respect to the world, it's not been as devastating due to early restrictions, but it's still making a sizeable impression on people right now. Also, Singlelinelabyrinth is likely more correct than she/he thinks: a good contributor to it, and literally everything else happening right now, is the [[1732: Earth Temperature Timeline|global warming]] of recent years. On the other hand, so as not to appear like your run-of-the-mill pugnacious liberal, I will agree with you that the codes should've been transferred to Pence during Trump's stay at the hospital.

3015: D&D Combinatorics

2024-11-25T00:12:27Z

Jjj: /* Explanation */ Added bold and italic style to the numbers with yellow backgrounds to help with colorblind accessibility.

{{comic
| number = 3015
| date = November 22, 2024
| title = D&D Combinatorics
| image = dnd_combinatorics_2x.png
| imagesize = 328x446px
| noexpand = true
| titletext = Look, you can't complain about this after giving us so many scenarios involving N locked chests and M unlabeled keys.
}}

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

Dungeons and Dragons (D&D) is a role-playing game that usually has a "Dungeon Master" (narrator) that takes a team of players through scenarios where they attack monsters and go on quests.

Often, there will be semi-random events: e.g., when attacking a monster, often a player will roll a die and deal damage based on the result. D&D uses a variety of dice, from regular d6 (6-sided, cubic dice) to other polyhedral dice, with the number of faces denoted by dX (e.g., d10 is a 10-sided die, with numbers from 1 to 10 on it). Common sets include: d4, d6, d8, d10, d12, d20, and occasionally d100 (typically not, however, the [[2626:_d65536|d65536]]).{{cn}}

With these, you can simulate events with a wide variety of denominators. In this case, Cueball gives a {{w|combinatorics|combinatorial}} problem:

* There are 10 arrows.
* 5 arrows are cursed.
* You randomly take two.
* What are the odds that neither of them are cursed?

Calculating using {{w|binomial coefficients}}, there are “10 choose 2” (45) ways to choose two arrows, of which there are “5 choose 2” (10) ways to choose 2 arrows that are non-cursed. As a result, the odds of taking all non-cursed arrows is 10/45, which simplifies to 2/9.

To see this in a different way, the probability of choosing one non-cursed arrow is 5/10, which then must be multiplied by the probability of choosing the second non-cursed arrow, which is now 4/9, giving 20/90 or 2/9, the same result as before.

The Dungeon Master (DM) in this case [[356: Nerd Sniping|has to]] map that probability into rolling multiple dice, whose sums are also not evenly distributed: i.e. if rolling 3d6 (3 six-sided dice) and a d4 (1 four-sided die), the sums can range from 4 to 22. It's pretty hard to do this in one's head, but it does happen that the odds of rolling 16 or more with this combination is 2/9, matching the probability that we want to simulate. Here's a table of all the 6*6*6*4=864 possible outcomes -

{| class="wikitable"
|+ All possible combinations of rolls for 3d6 + 1d4
|-
!Total!!4!!5!!6!!7!!8!!9!!10!!11!!12!!13!!14!!15!!16!!17!!18!!19!!20!!21!!22
|-
|Ways to roll it||1||4||10||20||34||52||71||88||100||104||100||88
| style="background:#ffffcc;" | ''' ''71'' '''
| style="background:#ffffcc;" | ''' ''52'' '''
| style="background:#ffffcc;" | ''' ''34'' '''
| style="background:#ffffcc;" | ''' ''20'' '''
| style="background:#ffffcc;" | ''' ''10'' '''
| style="background:#ffffcc;" | ''' ''4'' '''
| style="background:#ffffcc;" | ''' ''1'' '''
|}

71+52+34+20+10+4+1 = 192

192/864 = 2/9, which matches the desired probability from earlier. The table of outcomes can either be bruteforced with a program, or can be derived using generating functions.

The caption elaborates that the DM has a degree in the relevant field, and is unable to resist applying this to the D&D game when the opportunity arises - opportunities that Cueball eagerly provides for this very reason.

There are several much easier ways of implementing this operation, without coming up with a more complex solution:
#Do not even attempt to abstract the chances with dice-rolls. Literally present 10 similar-looking arrows, or other objects that are taken to represent arrows (face-down playing cards, for example), where the assigned information of whether each one is cursed initially hidden away from Cueball, and then just let Cueball pick any two.
#Even just with D&D dice, the DM could ask Cueball to roll a 1d10 for the first arrow, and then again for the second, re-rolling the second so long as Cueball gets the same number as before (which emulates the same sort of process, but with a non-zero chance of having to make and reject an arbitrary number of extra dice-rolls). One could specify that 1-5 represents the cursed arrows and 6-10 represents the non-cursed arrows, following the convention that lower rolls are bad in D&D.
#If understanding the actual odds, but wishing to keep the dice in use simple, a 2/9 probability can also be found by saying Cueball would succeed when 2D6 produces a 9, 10, or 12 (4/36, 3/36, and 1/36 probability, respectively, giving 8/36, i.e. 2/9).
#Alternatively, approximate the odds by using a d100 (or equivalent roll of two D10s) and seeking an 78 or higher (78-99), assuming double-zero is not taken as 100, which gives a 22% percent chance (substantially similar to 2/9 = 22.222...%), which may be sufficiently acceptable.
The first two options also instantly reveal cases of whether ''two'' cursed arrows are nominally chosen (at identical odds to the possibility of neither being so), should this be useful information on top of merely failing to avoid them. The third option could also be used to suggest this if (for example) the complementary results of 2, 4 or 5 are rolled, and the fourth in the event that the 'percentage' given is 0-21.

One could argue that the above solutions do not have the "polished" D&D feel of rolling a certain number of dice, adding them up, and seeing if the result is greater than or equal to an entirely correct required total. This is a commonly used mechanic for difficulty checks, hit calculations, and other such chance-based events in D&D. The DM may feel that this dice format is a requirement, but this approach is far too clunky for most DMs to be practical. It may be inferred that as the DM's mind tends towards more combinatorial solutions, she is either unable or unwilling to consider more straightforward and less time-consuming solutions to this cursed arrow problem.

The title text claims that Randall only started doing this to the DM after she herself insisted on forcing another combinatorial puzzle on the players several times, involving a bunch of locked treasure chests and a multitude of keys to unlock them with. This might be a reference to an M-of-N encryption system, where a system has ''n'' valid passwords (instead of just one) but requires ''m'' of those passwords to be given before it will open; it is assumed m is greater than 1 but less than n. While this is easy enough to implement in a computer system, it would be extremely cumbersome to build for a physical lock with keys, and spreading the mechanism across multiple separate treasure chests would be impossible without literal magic (luckily, magic is in plentiful supply in a typical Dungeons and Dragons game).{{cn}}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Cueball, Megan, Ponytail, White Hat, and Knit Cap are sitting at a table. Everyone is looking at Cueball. Ponytail is facepalming. The table is covered in sheets of paper and assorted dice.] 
:Cueball: I grab 2 of the 10 arrows without looking and fire them, hoping I didn't grab one of the 5 cursed ones. Did I?
:Ponytail: Sigh. Umm. Okay.
:Ponytail: Roll... Uh... Hang on...
:Ponytail: Roll 3d6 and a d4. You need... 16 or better to avoid the cursed arrows.

:[Caption below the panel:]
:I got '''''way''''' more annoying to play D&D with once I learned that our DM has a combinatorics degree and can't resist puzzles.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Knit Cap]]
[[Category:Games]]
[[Category:Math]]

1711: Snapchat

2024-08-11T08:08:16Z

Jjj: /* Explanation */ Fixed tense of 2016 pullitzer prize

{{comic
| number = 1711
| date = July 25, 2016
| title = Snapchat
| image = snapchat.png
| titletext = For obvious reasons, the prize is awarded at a different time of year from the others, while it's still fresh in the committee's memory.
}}

==Explanation==
''{{w|Snapchat}}'' is a photo-sending app that allows the receiving user to view the photo (known as a "snap") only within 24 hours of its posting, and for only 10 seconds before it is deleted. The {{w|Pulitzer Prize}} is famously awarded for exceptional journalism and photojournalism (there are many categories; see {{w|Pulitzer Prize#Categories|here}}).

[[Cueball]] reads that the ''Snapchat Pulitzer Prize'' has just been awarded but then, when [[Megan]] states that she heard the picture was really good, Cueball becomes disappointed because he realises he has already missed out on the chance to see the prize winning entry due to the temporary nature of Snapchat. Note that Megan also missed the opportunity to see the snap.

A given snap can be sent to a semi-public "Story" and the user decides how long any user can see the snap in a range from {{w|Snapchat#Core_functionality|1-10 s}}. In principle, any specific snap is only accessible for {{w|Snapchat#Stories_and_Discover|24 hours}} even if it is a story. A committee of users could have more than 10 seconds to access the snap, by viewing in sequence. Given the time it might take for a committee to decide which snap wins the prize, it is realistic that Cueball learns about the winner after the 24 hours is up; Thus even a user following the outcome might not be able to see the winning entry after that time. In practice it is possible to circumvent the Snapchat rule and {{w|Snapchat#Screenshots_and_FTC|take a screen shot}} or in other ways save the content of the snap. In the case of a Pulitzer Prize winning photo, someone would probably have saved it, if it was in real life. On the other hand, the only way for the photo to be recognised as a snap, eligible to win the prize, would be if no one could see it for more than 10 seconds. So one of the possible rules might be that any picture which was saved would not be able to win the prize.

The title text extends this ephemeral nature of Snapchat's content to the prize awarded for it: The other Pulitzer prizes are announced annually in April and awarded in May (except for 2016, the centennial year, when an awards dinner was held in October). The Snapchat Pulitzer Prize alone must be awarded as quickly as possible after the winner has been decided, before the prize committee forgets what the winning picture looked like. This of course underlines how silly this idea is, because only images seen during the assembly of the prize committee can be seen and remembered, and it is not possible to arrange this based on any knowledge of when a Pulitzer Prize "worthy" snap will be released.

[[Randall]] could be making fun of Snapchat (see the title), and the idea that you cannot save the images for later; As mentioned regarding screenshots, it is actually very easy to save pictures from Snapchat - to many a user's regret after having sent something very personal, such as naked pictures of themselves. The comic could also be seen as mocking the Pulitzer Prize for having too broad a spectrum of categories. Alongside the (photo)journalistic and prose awards, the Pulitzers also honor a variety of artistic pursuits, including Poetry, Drama and Music.

The new medium of Snapchat is certainly a hybrid form of art and information/opinion dispersal, both at its best and at its worst, but it is too ephemeral for awarding prizes to be logistically possible even if it were taken seriously enough for someone to want to award them.

The very next comic, [[1712: Politifact]], features an organization which was awarded the {{w|Pulitzer Prize for National Reporting}} in 2009.

==Transcript==
:[Cueball and Megan standing together. He holds a smartphone in his left hand and looks at it.]
:Cueball: Oh, the Pulitzer Prize for Snapchat was just awarded.
:Megan: Yeah.
:Megan: I hear the photo was really good.
:Cueball: Aw, ''maaaan''...

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Smartphones]]
[[Category:Social networking]]
[[Category:Photography]]

2924: Pendulum Types

2024-04-24T16:05:42Z

Jjj: The pendulum is depicted as vibrating vertically in the comic.

{{comic
| number = 2924
| date = April 24, 2024
| title = Pendulum Types
| image = pendulum_types_2x.png
| imagesize = 589x302px
| noexpand = true
| titletext = The creepy fingers that grow from a vibrating cornstarch-water mix can be modeled as a chain of inverted vertical pendulums (DOI:10.1039/c4sm00265b) and are believed to be the fingers of Maxwell's Demon trying to push through into our universe.
}}

==Explanation==
{{incomplete|Created by CREEPING TENDRILS OF STARCH - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic shows and describes several {{w|pendulums}}. The first three are actual physics models, while the last one is made up for the comic.

The simple pendulum consists of a joint, rod, and weight, and when released, it swings in a regular fashion. These are used commonly in pendulum clocks to keep time.

The {{w|double pendulum}} consists of 2 joints, 2 rods, and a weight, and when released, it swings in a chaotic fashion. Interestingly, this follows by the mathematical definition of chaotic, being that small changes result in vast differences. This pendulum is thus nearly unpredictable, and due to this chaotic nature, real life applications are very limited.

The {{w|inverted pendulum}} consists of a simple pendulum that is placed upside down, with some apparatus underneath vibrating it vertically to keep it upwards. If left unpowered (or improperly controlled from positional feedback) it will fall, hence the "unstable" part. (The comic, however, appears to depict {{w|Kapitza's pendulum}}, a powered version that does not rely upon monitoring and feedback-control.)

The nightmare pendulum appears to be an inverted double pendulum, with an additional uninverted pendulum swinging within its much more substantial weight (which is also adorned with archaic/mystical symbols). The comic claims that this pendulum summons {{w|Maxwell's Demon}}, and jokingly implies that Maxwell’s Demon is an actual entity, and not a thought experiment.

The title text continues this joke explicitly, by referencing a real paper titled [https://pubs.rsc.org/en/content/articlelanding/2014/sm/c4sm00265b Vibro-levitation and inverted pendulum: parametric resonance in vibrating droplets and soft materials] and implying that the paper ties the [https://www.youtube.com/watch?v=3zoTKXXNQIU "creepy fingers"] to Maxwell's (real) Demon. The paper only actually suggests that the phenomenon is related to inverted pendulum dynamics

==Transcript==
:[Four types of pendulums are shown in a single panel. Each has a bullet list below the depiction.]

:[Label:]
:Simple pendulum
:[A basic pendulum consisting of a joint, rod, and weight swinging in a regular arc]
:* Periodic
:* Stable
:* Useful for timekeeping

:[Label:]
:Double pendulum
:[A pendulum consisting of 2 joints, 2 rods, and a weight swinging in a more loopy arc]
:* Aperiodic
:* Chaotic
:* Moderately cursed

:[Label:]
:Inverted pendulum
:[An upside-down basic pendulum with some apparatus underneath]
:* Finely balanced
:* Unstable
:* Becomes stable when vibrated

:[Label:]
:Nightmare pendulum
:[An inverted double pendulum, with an additional uninverted pendulum swinging within a large weight adorned with archaic/mystical symbols]
:* Forbidden
:* Unphysical
:* Summons Maxwell's Demon

{{comic discussion}}

[[Category:Comics with cursed items]] 
[[Category:Physics]]