explain xkcd - User contributions [en]

3146: Fantastic Four

2025-10-07T01:19:38Z

Sophocrat: /* Explanation */ copy edit

{{comic
| number = 3146
| date = September 24, 2025
| title = Fantastic Four
| image = fantastic_four_2x.png
| imagesize = 343x388px
| noexpand = true
| titletext = One perk of being born at 0.88c is that your birthday is over two days long.
}}

==Explanation==
{{incomplete|Fix the citation needed.}}

The comic is a pun on the {{w|Oberth effect}}, which causes orbital maneuvers to be more efficient when deep into a gravitational well.
The movie referenced is ''{{w|The Fantastic_Four:_First_Steps|The Fantastic Four: First Steps}}'', released in 2025. The comic says that there is a boost because of the propulsion produced by the baby (a 'birth', rather than a 'berth'). In the movie, they do indeed go around a neutron star, and she does give birth to a baby while on board, but doesn't do that to get a boost.{{Actual citation needed}}

This effect is probably zero, as the change in the centre of mass of the ship and crew would not constitute a form of effective reaction-based propulsion.{{cn}} 

The title text states that being born at 88% the speed of light results in a birthday that's over two days long. This is due to {{w|time dilation|time dilation}}: from the perspective of Earth, at 0.88 c, the dilation factor γ is 2.1. So one day is 2.1 days seen from Earth.

The Oberth effect was also mentioned as a key to escaping Origin in [[2765: Escape Speed]].

==Transcript==
:[Ponytail is facing Cueball with one of her hands out, facing up and towards Cueball.]
:Ponytail: In the new ''Fantastic Four'' movie, their ship doesn't have enough fuel to get home and Sue Storm goes into labor, so they slingshot around a neutron star and fire their engines at periapsis — as Sue has her baby — to get a boost.
:Cueball: Ah yes, the Obirth effect.
{{comic discussion}}<noinclude>

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Movies]]
[[Category:Physics]]

3136: Pull

2025-09-30T05:08:57Z

Sophocrat: /* Explanation */ copy edit

{{comic
| number = 3136
| date = September 1, 2025
| title = Pull
| image = pull_2x.png
| imagesize = 650x220px
| noexpand = true
| titletext = Be careful fighting gravity. If you win, it's a long way down.
}}

==Explanation==
[[Megan]] and [[Cueball]] are lying in the grass on an orb – possibly a stylized Earth, though the curvature suggests a ''much'' smaller body. However, instead of the conventional frame orientation where gravity points towards the bottom of the image, the viewpoint is stationary outside the Earth while we see it slowly rotating, reminiscent of the alternate frame of reference apparently in use in [[2800: Down]]. Shown this way, we may have the intuitive feeling that the protagonists should fall off, and this makes a point how weird it is that gravity keeps us stuck to an orb, continuing with the theme of "how reality is odd" last seen in the prior comic, [[3135: Sea Level]].

In the first panel, Cueball expresses that he doesn't like being stuck there, possibly because he wants to explore other worlds or because he finds Earth limiting. The alternative would be "falling off", as in succumbing to the [[123|centrifugal force]] that results from the Earth's rotation – this would appear in the comic's perspective as both characters slowly "falling" away towards the right side of the panel. As this centrifugal effect is quite slight compared to the gravitational acceleration we're used to (0.34% of it at the equator), Megan and Cueball would have roughly three more minutes until they "fell" off-panel, assuming their position is of a mid-northern latitude typical to the US – unless they're able to fly under their own power now that they're no longer constrained by gravity, or unless the rest of Planet Earth also has its gravity turned off and violently explodes as a result.

In the second panel, Megan uses a more metaphorical sense of the word pull, she is attracted to lying on the grass doing nothing and blames her inability to get up and do things on gravity. This could also mean that if the pull (aka gravity) is less, she could get up more easily and get to where she wants to go.

Cueball replies that the pull might weaken over time. In a literal sense, gravity will not decrease significantly even in the long term and is likely not an actual obstacle to Megan getting up (assuming the sphere is Earth, which is the only known planet with humans on it{{cn}} as of the comic's publication). [https://www.cbc.ca/radio/quirks/sept-1-2018-gene-editing-in-dogs-wildfire-prediction-zika-fizzles-and-more-1.4804892/is-earth-getting-heavier-or-lighter-1.4804900 Earth gains mass] from dust and meteorites but also loses mass, mainly due to escaping hydrogen and helium. The net effect of these is for Earth to lose about 50,000 tonnes per year; in the 5‑minute period Megan mentions, equivalent to 500 kg out of the Earth's mass of 5.972 × 1024 kg, changing gravity by a factor of about 10-22 (1 part in 10 sextillion). Locally, gravity can also change due to mass redistribution. The Earth's core is very slowly cooling, leading to decreasing radius and thus increasing gravity at the surface. Towards the end of its life, the Earth's water will be boiled off due to the expanding Sun, leading to a decrease in gravity. Metaphorically, Cueball seems to just be saying that so she will stay a bit longer. Megan agrees.

Fighting the gravity in the title text is reminiscent of the Ancient Greek story of {{w|Icarus}}, who fell down after flying too close to the Sun, where flying might be seen as fighting gravity. It might also just be a rephrasing of the truism "The higher you go, the longer the fall". On the other hand, "it's a long way down" may not refer to falling back to Earth, but rather falling off the Earth, if one were no longer "stuck" to it. In that case, "down" would presumably mean toward the Sun, the center of gravitational pull in the solar system – a very long way away. If one "defeated" ''all'' gravity, "down" would mean "away from the Earth into space" endlessly, unless one happened to collide with some object.

However, you could avoid this if you had a method of self-propulsion, which brings to mind Superman, who is a good example. He can "defeat" gravity and has some method of self-propulsion (which is, obviously, how he flies). While humans don't have any natural means of self-propulsion while in a gravity free environment{{cn}}, they can use artificial methods (eg a jetpack).

==Transcript==
:[Cueball and Megan lying on a surface with grass, and the surface is round. They are orientated sideways, slightly facing up.]
:Cueball: I don't like being stuck to this orb,
:Cueball: but I guess falling off would be worse.

:[Cueball, Megan, and the surface are now rotated a little bit from the first panel.]
:Megan: I wouldn't mind if it pulled a little less hard, though.
:Megan: I have places to be.
:Megan: I shouldn't just lie around in the grass.

:[Cueball, Megan, and the surface are now rotated a little bit more from the second panel, slightly facing down.]
:Cueball: Maybe the pull will weaken if you wait around a little longer.
:Megan: Good idea. I'll give it another five minutes.

{{comic discussion}}<noinclude>

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Physics]]
[[Category:Astronomy]]

3113: Fix This Sign

2025-08-11T23:56:58Z

Sophocrat: /* Transcript */ removed {{incomplete transcript}} as it seems complete to me (feel free to revert if you disagree)

{{comic
| number = 3113
| date = July 9, 2025
| title = Fix This Sign
| image = fix_this_sign_2x.png
| imagesize = 448x405px
| noexpand = true
| titletext = We're building on our earlier success getting web developers to pay to change the backslashes in our displayed payment URL to forward slashes.
}}

==Explanation==
[[Randall Munroe|Randall]] has created a sign with a number of issues, such as bad kerning and alignment, that {{w|graphic designer}}s might be disturbed by. Fortunately these graphic designers can donate money to have the sign's issues fixed (which is possibly an improvement upon the situation invoked in the case of [[2598: Graphic Designers]]). [[2008: Irony Definition|Ironically]], once all the errors are fixed, the sign won't make sense any more, requesting money for fixes that have already been made.

The relative values assigned to each 'fix' are presumably proportional to at least one observer's perceived degree of issue with each 'mistake'. Given the costs of printing a sign of this size, Randall may have severely underpriced his fixes and set up his business to fail, if he intends to honour the pledges. He may be relying on there being a ''lot'' of passing graphic designers, generating multiple 'doanations' for each issue. Perhaps he will only fix them if a certain total amount of money is raised. This would be similar to the {{w|Kickstarter}} model, where people can donate at different levels and multiple people can donate at the same level, but the project will only be undertaken if a certain total amount of money is raised. If that total is not raised, nobody gets charged and the project is cancelled. One would hope the QR code would lead to a page detailing whether that's the case, what the total amount raised would need to be to be worth undertaking the fixes, or otherwise explaining how the <s>scam</s> project works. The following paid solutions to deliberate issues are advertised:

;Fix kerning ($10) :{{w|Kerning}} refers to the spacing between letters in a {{w|typeface}}, previously addressed in [[1015: Kerning]]. Kerning issues can result in letters in text appearing too far apart, as if there were a space in between, or too close, as if the letters were merged. In some instances, combinations of letters can appear like other letters. A well known example of this is the r and n merging into an m. (For example, "kerning" might appear as "keming", which is hinted at in the comic with the R and N close together, although here they are in uppercase, so this merging doesn't happen.)
:In this instance, the N and I in this word are very close together in this actual item, as a self-demonstrating issue. In the sign's title, the I and S (in "THIS") are too far apart and the S and the I (in "SIGN") are too close to each other. 

;Align columns ($20) :Here the dollar amount and the text itself do not {{w|typographic alignment|align}} in columns with the other entries, which disrupts the flow of the eye down the list, making it harder to read.

;Fix text size ($20) :The {{w|Point_(typography)|size}} of this entry is smaller than the rest of the other entries. As with the misaligned columns, such variances could be displeasing to the eye or distracting.

;Fix typo ($50) :The title of the sign says "'''Doanate''' to fix this sign!" Someone who is easily annoyed by random typos could be compelled to donate just to get the typo fixed.

;Fix centering ($50) :The content of the sign is off-center, leaving larger gaps to the left than to the right.

;Fix rotation ($100): The content of the sign slopes slightly down from left to right. For example, in the title "doanate" is higher than "sign", and the {{w|QR code}} 'graphic' is noticeably off-square.

;Title text: The title text refers to another common annoyance in a different field: that of website developers and, specifically, weblinks. {{w|URL}}s are defined to use forward slashes (/) rather than {{w|backslash}}es (\), which are used in Windows {{w|Path_(computing)|pathnames}}. Due to the widespread usage of both URLs and Windows pathnames, it is not uncommon for someone to mistakenly use backslashes in URLs, which isn't always supported. This annoyance was also discussed in [[727: Trade Expert]].

==Transcript==
:[A single panel containing a large, elevated sign with Ponytail standing in front of it.]

:[Title, slightly off horizontal, more to the right than central and the character spacing is not entirely consistent/aesthetic:] <big>Doanate[sic] to fix this sign!</big>

:[To the left of the lower part of the sign there is an 'QR code', tilted slightly with a plaintext link beneath it:] https://[illegible].com

:[To the right are several dollar values, in one column, and 'fixes', in a second, some of which have their own self-demonstrating quirks.]
::[The letters "R" and "N" may be too close together:] $10 fix kerning
::[Both dollar value and fix text are shifted left of their respective columns:] $20 align columns
::[This line is in a smaller font:] $20 fix text size
::$50 fix typo
::$50 fix centering
::$100 fix rotation

:[Ponytail stands looking at the sign, apparently in the process of using a smartphone:] Grrr...

:[Caption below panel:] My new company's business model is based on extorting graphic designers.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Ponytail]]
[[Category:Graphic designers]]

3110: Global Ranking

2025-08-11T23:56:53Z

Sophocrat: /* Transcript */ removed {{incomplete transcript}} as it seems complete to me (feel free to revert if you disagree)

{{comic
| number = 3110
| date = July 2, 2025
| title = Global Ranking
| image = global_ranking_2x.png
| imagesize = 740x280px
| noexpand = true
| titletext = Starting a meta-leaderboard for tracking who holds the record for ranking behind the most distinct people on an online leaderboard.
}}

==Explanation==
[[Cueball]] comments on his ranking on a {{w|chess}} platform, such as {{w|chess.com}} or {{w|lichess}}, which both have millions of chess players. He notices that being ranked so low is quite remarkable. Indeed, most sports only rank the best, most professional participants. Especially before computerization, nobody bothered to rank more than a few hundred or thousand competitors, largely because it would have been impractical. Even in chess, up to the mid-1990s, the FIDE rating floor (the lowest possible rating in a rating system) used to be 2200, which only included some of the best players.

As of 2025, the {{w|FIDE}} floor is 1400, which allows intermediates to be rated and ranked. However, platforms such as chess.com and lichess, which have appeared since the creation of the Internet, do not abide by the FIDE floor limitation, with chess.com placing the floor at 100 and lichess at 400, allowing even complete beginners to be rated and ranked. Ranking placements on chess.com go into the millions. Specifically, chess.com currently has about 218 million users, about 58 million of which have a [https://www.chess.com/leaderboard/live/rapid Rapid] rating. Being 7,145,000 would put Cueball just shy of the best 10% of players, with an Elo rating of about 900.

If being in the same ranking placement in different leaderboards has the same meaning to anyone, it is possible that being the lowest rated player on chess.com makes one worse than anyone in any other activity where rankings are applied. Cueball then explains that he enjoys playing chess for communicative reasons, to gain friends. [[White Hat]] points out the toxicity that appears to be rampant among the people he is playing with, which may be found in many hobbyist online communities, especially ones that are related to gaming. But Cueball, while aware of the issue, seems to take the abuse he is getting as an expression of a complicated kind of friendship.

In the title text, Cueball has managed to flip his terrible ranking into a great one, by creating a combined ranking of online leaderboards, where a lower ranking elsewhere translates into a high ranking in the meta-ranking.

==Transcript==
:[Cueball is seated at a desk, and uses a laptop. White Hat is standing right behind him.]
:Cueball: I'm ranked 7,145,000th globally on this chess platform.
:Cueball: It's hard to be ranked that low in '''''any''''' activity.

:[Zoom on Cueball talking]
:Cueball: Few pastimes even '''''have''''' 7 million rated players. Until the Internet, it wasn't really possible. You could be this bad, but only unofficially.

:[Cueball is now facing White Hat]
:Cueball: So in a sense, I'm worse at chess than anyone was at '''''anything''''' for most of human history.
:White Hat: Why are you still doing it?

:[Cueball is back on the laptop]
:Cueball: Well, no human has ever had this many friends to play with.
:White Hat: That person is calling you some very obscene names.
:Cueball: Our friendship is complicated.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]
[[Category:Chess]]
[[Category:Internet]]

2932: Driving PSA

2025-08-11T23:56:48Z

Sophocrat: /* Transcript */ removed {{incomplete transcript}} as it seems complete to me (feel free to revert if you disagree)

{{comic
| number = 2932
| date = May 13, 2024
| title = Driving PSA
| image = driving_psa_2x.png
| imagesize = 414x538px
| noexpand = true
| titletext = This PSA brought to you by several would-be assassins who tried to wave me in front of speeding cars in the last month and who will have to try harder next time.
}}

==Explanation==
A PSA is a {{w|Public Service Announcement}}. Some drivers, when having {{w|Traffic#Passage_priority_(right_of_way)|priority}} by the rules of the road (termed "right of way" in US legal statutes), will let others take it before them. However, yielding the right of way when it is not required does not legally grant the other driver the right of way -- they may still be required to yield to other vehicles on the road. (Hence the title of the PSA: "Random drivers can't grant you the right of way as a gift.")

At a 4-way stop, giving another driver the right of way is usually safe and courteous, but in other cases it can be dangerous. This comic is saying that people who exhibit this behavior dangerously can be assumed to be {{w|The_Terminator|Terminator}}-style assassins, sent to kill you by sending you into contention with other traffic to make it look like an accident, and thereby prevent some future act on your part that is not to their liking.

In this comic, the deferential driver is holding up a queue of vehicles (including a large tractor-trailer truck) that is obscuring the immediate view of oncoming traffic. Instead of simply turning left and reducing the queue, they are waving Randall's car into that traffic, perhaps because they forgot that the other lanes have priority over the crossing driver. The effect could be to wave him through right into the path of another car traveling at full speed — a clever way for a time-traveling assassin to take down one's target without arousing suspicion.

Not pulling into traffic when your view is obstructed is good advice, and Randall's comical exaggeration may make the advice more memorable. Always check for yourself that your way is clear, and if your view is blocked, sit tight.

However, Randall seems to be assuming that the waving gesture can only ever mean one thing: Pull all the way into traffic. It may be that a "waving out" gesture is intended to give the waiting car a chance to turn into the median strip (see details below). Viewing courteous behavior as conclusive evidence of a temporal assassination conspiracy is humorously ego-centric and improbable.

The title text explains that Randall made this PSA because he has experienced this multiple times in the last month, and that the assassins should try harder next time.

===Alternate interpretation of the waving gesture===

Note that in this comic, as currently illustrated, there appears to be sufficient room in the median strip for the waiting car to pass the first set of lanes and stop in the median strip, protected from passing traffic on both sides, to legally wait for the second stream of traffic to safely subside. Waiting in this median turning area is a normal maneuver in suburban and exurban US areas where these types of non-signaled intersections are common. There's no reason to assume that the supposed would-be assassin is not simply waving the waiting car to the safety of the median strip. Randall's message of caution is still sound, but he accidentally illustrated an intersection diagram that fails to optimally support his case.

[[File:2932 Alt.png|frameless|Illustration showing room to safely turn left halfway, stopping in the median strip]]

'''Legality'''

Median strips are typically used to allow vehicles to safely make left turns without impeding the flow of traffic. When emerging from a side road, vehicles can cross the first lane(s) of traffic and wait in the median strip until it is safe to merge into the opposite lane(s).
* In Texas, using the median strip to wait for a gap in traffic is generally acceptable. The Texas Department of Public Safety suggests that drivers use the median strip when appropriate. Source: [https://www.texashighwayman.com/laws.shtml Texas laws]
* [https://le.utah.gov/xcode/Title41/Chapter6A/41-6a-S801.html?v=C41-6a-S801_2015051220150512 The state of Utah also allows this to happen.]
* In {{w|Denmark}}, it is considered bad practice to pause in the median strip when crossing; left turns should be carried out in a continuous maneuver.

==Transcript==
:Driving PSA:
:Random drivers can’t grant you the right of way as a gift.
:[A T-intersection with a major road separated by a concrete median going from top to bottom, and a minor road coming from the left]
:[A car is stopped at the end of the minor road]
:First car [arrow pointing to car]: You, waiting to turn left
:[A second car is stopped in the dedicated left turn lane of the right major road, with a third car, a truck hauling cargo, and a fourth car lined up behind it]
:Second car [in a speech bubble]: You go ahead! I’m feeling generous.
:Second car [arrow pointing to car]: Time traveler pretending to be polite
:[In the second lane is a black arrow pointing upwards, with text below it reading 45 MPH, and a fifth car below the text]
:Fifth car [arrow pointing to car]: Car that they are waving you into the path of
:If someone waves you out, assume that they are an assassin sent from the future to kill you and make it look like an accident.

{{comic discussion}}

[[Category:Time travel]]
[[Category:Public service announcement]]

3116: Echo Chamber

2025-08-11T23:40:11Z

Sophocrat: added Trivia section about the faint grey letters behind the caption

{{comic
| number = 3116
| date = July 16, 2025
| title = Echo Chamber
| image = echo_chamber_2x.png
| imagesize = 383x296px
| noexpand = true
| titletext = This is almost as bad as the time I signed up for a purely partisan fishing expedition.
}}

==Explanation==
An {{w|echo chamber}} is a structure designed to maximise acoustic reverberation, and therefore echoes. In cultural terms, and particularly with social media, a ''metaphorical'' {{w|Echo chamber (media)|echo chamber}} reverberates the opinions of a group of individuals so that those individuals perceive those opinions as being the social norm. This has resulted in {{w|political polarisation}} and to conspiracy theories such as {{w|Pizzagate conspiracy theory|Pizzagate}}.

[[Cueball]] appears to have confused the two and built a physical chamber designed to echo back the sound of videos he is watching on social media. Unsurprisingly to the reader, but apparently not to Cueball, this turns out to be very annoying. Specifically, he appears to be watching cat videos, which are stereotypical social media content, but not usually the kind that produces accusations of 'echo chambers'. The "Mittens" mentioned in the audio is a stereotypical cat name.

Similarly, the "partisan fishing expedition" referenced in the title text has differing metaphorical and real-life interpretations. A metaphorical "fishing expedition" is an investigation begun on flimsy or no evidence to try to find unsavory or incriminating behavior. When such an investigation is motivated by political considerations in favor of one particular political party, it may be referred to as a "partisan fishing expedition". A "purely partisan fishing expedition" would involve a trip to catch actual fish where all the people on the fishing trip were either {{w|partisan (politics)|committed members of one political party}}, {{w|partisan (military)|members of domestic irregular military forces}}, or possibly one where such people were the intended catch. Alternatively, it could be a {{w|spearfishing}} expedition, as a {{w|partisan (weapon)|partisan}} is a type of polearm. It is unclear what strange mashup of the above Cueball found himself involved in, but at the very least it turned out to be deeply unsatisfying, if not actually dangerous.

==Transcript==
:[Cueball is sitting on a chair with his hands covering his ears. He is in a circular room with a phone on a stand. All words coming out of the phone are repeated everywhere, getting larger and less opaque]

:Phone: Here's Mittens falling into the laundry hamper for the third time today!
:[Caption below panel:]
:Now that I've built one, I finally get why people complain about social media echo chambers.

==Trivia==
Faint grey letters can be seen behind the letters of the comic caption. This is presumably a mistake, although it could be intentional as further "echoes".

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]