explain xkcd - User contributions [en]

Talk:3220: Rotational Gravity

2026-03-23T21:03:36Z

136.47.216.1:

Beep, Boop! nothing else here yet ;) [[Special:Contributions/216.25.182.141|216.25.182.141]] 03:06, 17 March 2026 (UTC)

Counterpoint the the action park thing; i think its referencing [[2935]] [[User:TheTrainsKid|TheTrainsKid]] ([[User talk:TheTrainsKid|talk]]) 03:26, 17 March 2026 (UTC)
:For sure. It is a direct reference to that comic. I wonder if they should be seen as a two comics series? I think there is a bit too little for it. If there ever comes a third comic where Cueball is fired from a cruise line I would say there should be made a category for it though. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:44, 17 March 2026 (UTC)

Is he saying that the ship is rolling? This would not give as much artificial G than pitch or yaw. [[User:SDSpivey|SDSpivey]] ([[User talk:SDSpivey|talk]]) 04:53, 17 March 2026 (UTC)
:It all depends on the rotation speed. It is more likely the ship would survive being rotated along that axis. Of course there would then only be gravity away from the central line of the ship. And of course the ship would not survive such a rotation. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:44, 17 March 2026 (UTC)
::I'm sure it could survive a few rotations. More than the people could. :) [[User:SDSpivey|SDSpivey]] ([[User talk:SDSpivey|talk]]) 14:34, 17 March 2026 (UTC)
:::What if it's a catamaran, rotating the main body of the ship like a barbecue spit? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 18:28, 17 March 2026 (UTC)

I'm wondering if this has to do with the imminent premiere of a science-based movie, Project Hail Mary? [[Special:Contributions/2601:601:D47C:3090:B80E:E250:C231:507A|2601:601:D47C:3090:B80E:E250:C231:507A]] 04:08, 18 March 2026 (UTC)
:Very likely. In the book, the ship also used rotation to simulate 1g gravity, using spin drives. And because the spin drives were in the engine compartment on the rear of the aircraft, and they didn't want to bolt all the equipment to the ceiling prior to takeoff, the crew compartment had to be rotated to enter centrifuge configuration. (See [[https://projecthailmary.fandom.com/wiki/Hail_Mary#Artificial_Gravity]].)[[Special:Contributions/136.47.216.1|136.47.216.1]] 21:03, 23 March 2026 (UTC)
The next number is prime! I wander if it will be a math one.

At this rate, around comic 3500 there will be enough about getting fired from cruise lines to maybe consider a category of its own [[User:R128|R128]] ([[User talk:R128|talk]]) 17:17, 18 March 2026 (UTC)

Cueball's plan would seem to be quite easy to replicate. Swim to the stern of the ship, plant your feet firmly, and grasp the propeller(s), thereby stopping them. The engines will rotate the ship around the crankshaft centerline until they run out of fuel. [[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 23:49, 21 March 2026 (UTC)

Talk:3201: Proof Without Content

2026-01-31T03:42:01Z

136.47.216.1:

First. Would be funny to have an explanation along the lines of "It is possible to give an explanation with no content. Here's how:" [[User:R128|R128]] ([[User talk:R128|talk]]) 17:44, 30 January 2026 (UTC)

Proof without Content seems to be a play of words for [https://en.wikipedia.org/wiki/Proof_without_words]Proof without Words

The comic pokes fun at a common situation found in mathematics books. The students sees a statement with a very short proof that doesn't make sense since it's been summarized in a way that is helpful for people already familiar with the theorem. For instance: "prime numbers larger than 2 are odd". Proof: "even numbers are divisible by 2". The student is expected to know that a number divisible by 2 is not prime, but that's most likely something that comes up later in the same book, or sometimes not explained at all.
In the comic the "short" proof is taken to the absurd level of being completely empty. What mathematical statement can be proven with a completely empty proof? The fact that there exists comics which have statements with empty proofs. It is both a joke about difficult to understand proof in math books and also a meta-mathematics joke as the proof is talking about itself.
The title text pokes even more fun at maths books where many important theorems are stated and are given to the students as useful facts but with no proof, stating that demonstrating the truth of the statement is so easy it is "left as an exercise for the reader". This common scenario frustrates students because in some cases the "exercise" is extremely difficult to do.
The only "proof without content of a conjecture without content" is a blank page altogether, which clearly exists, so the statement is true, even if meaningless.
:I don't recall that problem with such a proof. Usually the statement about primes being odd comes after giving the definition of prime and composite numbers. From that, being divisible by 2 clearly makes a number composite. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:31, 30 January 2026 (UTC)
::You must be very smart. [[Special:Contributions/2600:1700:2120:5880:C885:5DAF:EFD8:EADF|2600:1700:2120:5880:C885:5DAF:EFD8:EADF]] 22:12, 30 January 2026 (UTC)

I really do not get that title text. I put an attempt at understanding it down but it may have gone over my head [[User:R128|R128]] ([[User talk:R128|talk]]) 17:58, 30 January 2026 (UTC)

The comic demonstrates a proof without content, but is it a <i>convincing</i> proof? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:33, 30 January 2026 (UTC)
:If it is, then yes. QED. ;) [[Special:Contributions/81.179.199.253|81.179.199.253]] 21:14, 30 January 2026 (UTC)

I think the tautological nature of the proof could be better explained. If the blank image is interpreted as a correct proof, it proves the notion that a blank image can prove a conjecture. [[Special:Contributions/2600:4041:2E5:B900:6C41:5AFB:89D1:F216|2600:4041:2E5:B900:6C41:5AFB:89D1:F216]] 22:11, 30 January 2026 (UTC)

Isn't this proof using circular reasoning? The proof is only convincing if the conjecture that an empty proof can be convincing is correct. [[Special:Contributions/73.222.207.213|73.222.207.213]] 23:26, 30 January 2026 (UTC)
:Yeah, it is a circular argument. Maybe that’s part of the joke? [[User:Logalex8369|Logalex8369]] ([[User talk:Logalex8369|talk]]) 01:39, 31 January 2026 (UTC)
::I say it's only circular reasoning if it's circular reasoning. [[Special:Contributions/81.179.199.253|81.179.199.253]] 02:01, 31 January 2026 (UTC)
:Yes, it really begs the question... [[Special:Contributions/136.47.216.1|136.47.216.1]] 03:42, 31 January 2026 (UTC)

3173: Satellite Imagery

2025-11-26T21:59:55Z

136.47.216.1: /* Explanation */

{{comic
| number = 3173
| date = November 26, 2025
| title = Satellite Imagery
| image = satellite_imagery_2x.png
| imagesize = 429x526px
| noexpand = true
| titletext = Every weekend I take an ATV out into the desert and spend a day tracing a faint "(C) GOOGLE 2009" watermark across the landscape.
}}

==Explanation==
{{incomplete|This page's explanation has been obscured, and we're currently trying to figure out what it says. Don't remove this notice too soon.}}

A big image of a desert is shown, having large squares on the left side the two conspiracy theorists claim is blocky imagery of an unknown facility, but may be a square made from colored squares much larger than the accuracy of the imagery.

In the title text Cueball aims to further confuse the remote sensing people by drawing a {{w|Watermark}} in the sand, leading people to believe the picture was taken in 2009.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}

:[[Cueball]] and [[Ponytail]] are standing in front of a board, which is displaying a satellite image of an empty area. However, in the middle of the image there is a square area which is pixelated as if it had been redacted.]

:Cueball: Wait, when was this imagery taken? Is this censorship the work of the contractor? One of our people? '''''Foreign agents?'''''
:Ponytail: Do we know who's operating a facility at that location?
:Cueball: We can't find '''''anything'''''.

:[Caption:]
:My hobby: Setting up big colored panels in the middle of nowhere as a prank on remote sensing people.

{{comic discussion}}<noinclude>
[[Category:My Hobby]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Conspiracy theory]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
</noinclude>

Talk:3160: Document Forgery

2025-10-27T22:04:38Z

136.47.216.1:

Can someone please make a printable version of this, thank you! [[Special:Contributions/216.126.34.139|216.126.34.139]] 21:26, 27 October 2025 (UTC)

Reminds me of [https://www.bbc.co.uk/news/articles/c70650ely2eo the infamous fake certificate with "verify" spelt wrong]... [[Special:Contributions/2.98.65.8|2.98.65.8]] 21:47, 27 October 2025 (UTC)

It seems like my summary got added on top of the other one somehow. I don't know if anyone wants to try to merge them... [[Special:Contributions/136.47.216.1|136.47.216.1]] 22:04, 27 October 2025 (UTC)

3160: Document Forgery

2025-10-27T21:52:51Z

136.47.216.1: /* Explanation */

{{comic
| number = 3160
| date = October 27, 2025
| title = Document Forgery
| image = document_forgery_2x.png
| imagesize = 345x323px
| noexpand = true
| titletext = It comes with a certificate of authenticity, which comes with a certificate of authenticity, which comes with a...
}}

==Explanation==

{{incomplete|This page was created recently. Don't remove this notice too soon.}}
This comic depicts a diploma for a PhD in Document Forgery. While the diploma looks official, some things seem questionable. Document forgery is not typically offered as a discipline for doctoral study, likely because of its questionable legality [citation needed]. Moreover, the diploma is offered from the fictitious and exceedingly generic "East State University" (normally an institution with "State" in its name would also specify which "state" the campus is located in).

The caption claims that if you hang a diploma like this in your office and nobody notices, you've earned it (ie, the creation of such a credible-looking document without drawing any suspicion shows PhD-worthy skills in forgery).

The title text says that the diploma comes with a certificate of authenticity; however, since the diploma is questionable, this certificate is also somewhat questionable, so the certificate comes with its own certificate of authenticity, which also comes with a certificate of authenticity, ad infinitum. Of course, all of the certificates would likely be forged, and they really only show that the forger has a lot of time on their hands.

The comic shows a diploma for a doctorate from the non-existent "East State University", with the unusual program of "Document Forgery". The document is itself a forgery, and the legally questionable program name would lead most readers to look more closely at the rest of the document. The text below implies that if the document is realistic enough that no one uncovers these inconsistencies when posted in an office, then the person posting the document deserves the non-existent degree.

Many awards and educational programs are represented by a physical certificate presented to the person being recognized for the accomplishment. The creation of a such a document is normally much easier than the underlying accomplishment, so some people wanting the prestige without the effort and cost will forge a document. Fake university diplomas are sometimes used as a marketing tactic for individuals seeking jobs or customers - these are normally realistic to pass scrutiny and are considered fraud. Obviously and in some cases absurdly unrealistic diplomas are used for entertainment, and may be considered unregulated free speech.

The title text highlights the unreliability of certificates of authenticity. A product or document may come with an accompanying certificate that states that the product/document is "authentic". Since a certificate can also be forged, another certificate can attest to the authenticity of the first, and so on, because no number of pieces of paper will make the original claim true. Many important and legally binding documents lack any certificate of authenticity, but instead have something much harder to gain: the backing of a recognized and independent witness or organization that can confirm the truth when the paper is in doubt.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}

{{comic discussion}}<noinclude>

Talk:3111: Artificial Gravity

2025-07-04T17:34:19Z

136.47.216.1:

Note the motion lines around the main body of the spacecraft, showing that it is also shaking to a much lesser extent. [[Special:Contributions/181.214.218.76|181.214.218.76]] 15:26, 4 July 2025 (UTC)
@above That is just Newton's Third Law, which is very often taken into account in space obviously. [[User:Thehydraclone|Thehydraclone]] ([[User talk:Thehydraclone|talk]]) 16:04, 4 July 2025 (UTC)

Report: Total crew bone mass remains constant.

The spinning idea reminds me of the spin drive from Andy Weir's "Project Hail Mary."[[Special:Contributions/136.47.216.1|136.47.216.1]] 17:34, 4 July 2025 (UTC)

3098: Trojan Horse

2025-06-06T23:11:02Z

136.47.216.1: never mind it was just an awkwardly placed prepositional phrase

{{comic
| number = 3098
| date = June 4, 2025
| title = Trojan Horse
| image = trojan_horse_2x.png
| imagesize = 740x196px
| noexpand = true
| titletext = Ultimately, history would imperfectly record the story of the Foal of Troy.
}}

==Explanation==
{{incomplete|This page was created by a BABY BOT INSIDE A BOT. Don't remove this notice too soon.}}
This comic presents a brief retelling of the {{w|Trojan Horse}} story, the climactic event of the legendary {{w|Trojan War}}, one of the best-known epics of ancient Greece and Rome. The retelling is a {{w|Feghoot|feghoot}}, set up to deliver the pun in the title text.

The premise is that the Trojan Horse story's origin is mundane. The gift to the Trojans by the (supposedly) departing Greek army, we are told, was a normal-sized, living mare, which promptly and unexpectedly dropped a foal. According to the title text, this is the story of the "Foal of Troy", which "history imperfectly recorded". In the "imperfect record" (presumably the one by {{w|Virgil}}), the normal-sized live horse became a colossal wooden statue that "dropped" a commando unit of some 40 Greek soldiers, who opened the gates of Troy to the main Greek force (who had sailed back under the cover of darkness), resulting in the "''Fall'' of Troy". The pun is implicit, as "Fall of Troy" does not appear in the comic. Fall (∏τώση) and Foal (∏ουλάρι) begin with the same letter in Greek and are spelled even more similarly in English, as well as being near {{w|homophone}}s. This would correspond with history exaggerating a supposed attack upon the food supply into the fall of the entire city. Of course, in reality, people are willing to feed horses because horses can accomplish useful tasks but only if they haven't died of starvation, and the people in the comic do not seem disturbed by the mare's appetite, only the foal's.

Based on how Cueball calls the offspring an "inner horse" instead of a foal (the term for a child horse), the fact that he interprets the foal's interest in oats as an attack upon Troy's food supply even though all horses need to eat but are nonetheless considered useful by humans, and his overall surprise that the mare gave birth, it seems that he does not know very much about horses. Calling a foal an "inner horse" would be analogous to calling a baby an "inner human", thus reflecting a lack of knowledge of placental mammalian reproduction similar to [[441: Babies]].

The debate in the comic, about the mission of the "Foal of Troy" and its impact on the city, reflects the debate in the Trojan Horse legend about the purpose of the horse statue and whether it was safe to accept it. The consequence of accepting the "Foal of Troy", a minor assault on the city's oat store, is accepted with indignation in the comic. In the legend, the potential consequences of accepting the horse statue were rejected or ignored until after it was too late. This is the etymology that caused the story to lend its name to the act of trying to smuggle something unwanted past people's notice by hiding it within something larger and more innocuous, particularly {{w|Trojan horse (computing)|computer malware}}.

It is not made clear whether the gifter of the horse knew of/suspected the pregnancy or whether they'd have even chosen to hand it over under different circumstances. However, it is consistent with the story, and with the {{w|Beware_of_Greeks_bearing_gifts|"Greeks bearing gifts" trope}} that originated with it, that the Greeks intentionally gifted a gravid mare to annoy the (in the "mundane" version otherwise victorious) Trojans. Surprise foals, where a mare is purchased with a hitherto unknown pregnancy, actually occur. The pregnancy is typically excused as mundane weight gain, up until the point where a foal is discovered with its mother in the morning. Horses with rounder builds, like some pony breeds, are known for maintaining undetected pregnancies. The reason a surprise foal might be salient for the comic, beyond the "Foal of Troy" pun, is the non-trivial costs of horse ownership, which can amount to hundreds or thousands of dollars per month. Food costs are part of (but not all of) this, as the comic touches on.

Archaeological evidence of a military conquest of {{w|Troy}} during the Bronze Age, or even of a major war centered on the city, is lacking. Far better evidence exists for the destruction of several iterations of the city by earthquakes. It is not thought that these earthquakes were caused by horses. Possibly, the Trojan War legend arose as visitors attempted to explain the ruins of an earthquake-ravaged, deserted city. The "Foal of Troy" story, therefore, need not include a Greek conquest of Troy, or even a major military conflict with the Greeks.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[A horse is facing Cueball and Ponytail, who are standing in front of an entrance below a tower.]
:[In an inset panel, Cueball is talking to Megan and Hairy.]
:Cueball: When the Greeks departed, they left behind a horse as a gift.

:[Hairbun is standing behind a horse, with Cueball standing in front.]
:We took it as a gesture of peace, but it carried a secret payload.

:[A smaller horse is standing behind the horse from previous panel, which is looking behind at it.]
:One night, from within the horse, '''''another, smaller horse emerged!'''''

:[Close-up on Cueball.]
:Cueball: Our guards have been unable to determine the inner horse's objective, but it has begun to show an interest in our oats.
:Off-panel voice 1: An attack on Troy's food supply!
:Off-panel voice 2: How ''dare'' they!?

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hairy]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairbun]]
[[Category:Animals]]
[[Category:Food]]

3098: Trojan Horse

2025-06-06T23:09:03Z

136.47.216.1: removed extraneous comma

{{comic
| number = 3098
| date = June 4, 2025
| title = Trojan Horse
| image = trojan_horse_2x.png
| imagesize = 740x196px
| noexpand = true
| titletext = Ultimately, history would imperfectly record the story of the Foal of Troy.
}}

==Explanation==
{{incomplete|This page was created by a BABY BOT INSIDE A BOT. Don't remove this notice too soon.}}
This comic presents a brief retelling of the {{w|Trojan Horse}} story, the climactic event of the legendary {{w|Trojan War}}, one of the best-known epics of ancient Greece and Rome. The retelling is a {{w|Feghoot|feghoot}}, set up to deliver the pun in the title text.

The premise is that the Trojan Horse story's origin is mundane. The gift to the Trojans by the (supposedly) departing Greek army, we are told, was a normal-sized, living mare, which promptly and unexpectedly dropped a foal. According to the title text, this is the story of the "Foal of Troy", which "history imperfectly recorded". In the "imperfect record" (presumably the one by {{w|Virgil}}), the normal-sized live horse became a colossal wooden statue that "dropped" a commando unit of some 40 Greek soldiers, who opened the gates of Troy to the main Greek force (who had sailed back under the cover of darkness), resulting in the "''Fall'' of Troy". The pun is implicit, as "Fall of Troy" does not appear in the comic. Fall (∏τώση) and Foal (∏ουλάρι) begin with the same letter in Greek and are spelled even more similarly, as well as being near {{w|homophone}}s in English. This would correspond with history exaggerating a supposed attack upon the food supply into the fall of the entire city. Of course, in reality, people are willing to feed horses because horses can accomplish useful tasks but only if they haven't died of starvation, and the people in the comic do not seem disturbed by the mare's appetite, only the foal's.

Based on how Cueball calls the offspring an "inner horse" instead of a foal (the term for a child horse), the fact that he interprets the foal's interest in oats as an attack upon Troy's food supply even though all horses need to eat but are nonetheless considered useful by humans, and his overall surprise that the mare gave birth, it seems that he does not know very much about horses. Calling a foal an "inner horse" would be analogous to calling a baby an "inner human", thus reflecting a lack of knowledge of placental mammalian reproduction similar to [[441: Babies]].

The debate in the comic, about the mission of the "Foal of Troy" and its impact on the city, reflects the debate in the Trojan Horse legend about the purpose of the horse statue and whether it was safe to accept it. The consequence of accepting the "Foal of Troy", a minor assault on the city's oat store, is accepted with indignation in the comic. In the legend, the potential consequences of accepting the horse statue were rejected or ignored until after it was too late. This is the etymology that caused the story to lend its name to the act of trying to smuggle something unwanted past people's notice by hiding it within something larger and more innocuous, particularly {{w|Trojan horse (computing)|computer malware}}.

It is not made clear whether the gifter of the horse knew of/suspected the pregnancy or whether they'd have even chosen to hand it over under different circumstances. However, it is consistent with the story, and with the {{w|Beware_of_Greeks_bearing_gifts|"Greeks bearing gifts" trope}} that originated with it, that the Greeks intentionally gifted a gravid mare to annoy the (in the "mundane" version otherwise victorious) Trojans. Surprise foals, where a mare is purchased with a hitherto unknown pregnancy, actually occur. The pregnancy is typically excused as mundane weight gain, up until the point where a foal is discovered with its mother in the morning. Horses with rounder builds, like some pony breeds, are known for maintaining undetected pregnancies. The reason a surprise foal might be salient for the comic, beyond the "Foal of Troy" pun, is the non-trivial costs of horse ownership, which can amount to hundreds or thousands of dollars per month. Food costs are part of (but not all of) this, as the comic touches on.

Archaeological evidence of a military conquest of {{w|Troy}} during the Bronze Age, or even of a major war centered on the city, is lacking. Far better evidence exists for the destruction of several iterations of the city by earthquakes. It is not thought that these earthquakes were caused by horses. Possibly, the Trojan War legend arose as visitors attempted to explain the ruins of an earthquake-ravaged, deserted city. The "Foal of Troy" story, therefore, need not include a Greek conquest of Troy, or even a major military conflict with the Greeks.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[A horse is facing Cueball and Ponytail, who are standing in front of an entrance below a tower.]
:[In an inset panel, Cueball is talking to Megan and Hairy.]
:Cueball: When the Greeks departed, they left behind a horse as a gift.

:[Hairbun is standing behind a horse, with Cueball standing in front.]
:We took it as a gesture of peace, but it carried a secret payload.

:[A smaller horse is standing behind the horse from previous panel, which is looking behind at it.]
:One night, from within the horse, '''''another, smaller horse emerged!'''''

:[Close-up on Cueball.]
:Cueball: Our guards have been unable to determine the inner horse's objective, but it has begun to show an interest in our oats.
:Off-panel voice 1: An attack on Troy's food supply!
:Off-panel voice 2: How ''dare'' they!?

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Hairy]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairbun]]
[[Category:Animals]]
[[Category:Food]]