explain xkcd - User contributions [en]

3257: Beam Pipe

2026-06-12T14:43:57Z

82.132.236.149: /* Explanation */

{{comic
| number = 3257
| date = June 10, 2026
| title = Beam Pipe
| image = beam_pipe_2x.png
| imagesize = 309x397px
| noexpand = true
| titletext = 'If you keep trying to spray your collaborators with the beam when they're not looking, I'm turning off the ion source and NO one will get to play with the beam!' --Physics's mom
}}

==Explanation==
{{incomplete|This page was found with a Physics Nobel Prize. Don't remove this notice too soon.}}
With pipes such as hosepipes, you can make the water come out in a more rapid and (if done right) more concentrated stream by covering up part of the exit nozzle with your finger (or anything, for that matter). This forces the water to come out of a smaller space, increasing the effect pressure. As the {{w|Large Hadron Collider}} (LHC) can be considered a sort of 'pipe' (a beam pipe, as pointed out in the comic title) this comic makes the ridiculous assumption that the same logic applies there, and its beam can be made stronger by partially covering the hole — something which obviously wouldn't work in real life.{{Citation needed}} In reality, the relativistic particles would not behave as a liquid. It may be that they would annihilate the thumb (or possibly just mildly irradiate it, depending upon intensity) and create a broad spray, instead of narrowing the beam. Although the pipe being open-ended (or partly so, with the thumb half over it) would already have destroyed the vacuum-like conditions necessary to properly maintain the partical beam, without some vacuum-sealing cap or internal bulkhead, which the beam already must have passed through.

The title text expands the joke, once more treating the LHC as if it were a hosepipe. Making the hose squirt a more intense stream is a common thing for children to do — often to spray family and friends with the pressurized water. This applies the same logic to the LHC, imagining the mother of "Physics" (the science, as opposed to a person) telling off their (presumably adult) child for 'spraying their colleagues with the beam' — something very incomprehensible in real life.

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

:[A picture shows a (partly obscured by the panel) particle accelerator (namely this one being the Large Hadron Collider at CERN). Megan is shown on a stepladder, covering the beam pipe with her thumb. Cueball is shown standing behind the ladder, watching.]
:[Caption below the panel:]
:This year's physics Nobel will go to the scientists who figured out that you could make the Large Hadron Collider more powerful by covering part of the beam pipe with your thumb.

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

3253: Sunbeam

2026-06-12T14:26:13Z

82.132.236.149: /* Explanation */

{{comic
| number = 3253
| date = June 1, 2026
| title = Sunbeam
| image = sunbeam_2x.png
| imagesize = 398x347px
| noexpand = true
| titletext = While weather control is typically thought of as a superpower, the unconscious ability of astronomers and astrophotographers to summon clouds is more properly classified as a curse.
}}

==Explanation==

{{w|Astrophotography}} is the act of taking pictures of very distant objects. Common subjects of astrophotography include celestial bodies like planets and moons of the solar system, faraway galaxies, nebulae, spacecraft, or even {{w|Hubble Deep Field|empty patches of the sky}}.

In order to take such photos, one needs to know where these objects are in the sky. One major problem faced by Earth-based astrophotographers (most of them) is the fact that the Earth rotates.{{Citation needed}} As the Earth rotates, it creates the illusion that the celestial objects being photographed are rotating through the night sky. In order to get clear pictures of their subjects, astrophotographers must develop a strong understanding of how objects like a galaxy or the Sun move through the sky, so that their cameras can compensate for this rotation and produce clear pictures.

This understanding of how objects move through the sky due to the Earth's rotation is the minor superpower referred to in the comic. As the Sun is an example of an object in the sky, the intuition of astrophotographers allows them to predict where the Sun will be in the future, and by extension, where the light flooding in through the window will be in the future. With this knowledge, [[Cueball]], who presumably has this minor superpower, can advise his friends to sit at the far table to avoid the light from the window hitting them. Though extra light may sometimes be considered desirable, in this case such direct sunlight would probably be considered problematic as there may be excessive heat and/or light. By contrast, the table currently beyond the beams of sunlight would be a perfectly acceptable place to sit and would remain so. There is a chance however that it doesn't actually matter in this scenario which table to sit at, and Cueball is just saying it to show off his ability.

This comic probably takes place in the Northern Hemisphere, more specifically being north of the Sun's current ground-track (i.e. the line through the tropics which experience the Sun being directly overhead on any given day of the year, which changes over the course of the year, due to the axial tilt of the Earth). In both hemispheres, the Sun can be found rising in the east in the morning, at its highest at around midday (exactly at true local midday, but must be adjusted for timezone issues such as the [[1799: Bad Map Projection: Time Zones|offset from the nominal local datum]] and [[:Category:Daylight saving time|DST]] effects), then setting in the west in the evening (at least until you get close enough to the poles to experience no, or barely any, day or night according to the time of year). Therefore, in the subtropical and temperate latitudes of the Northern Hemisphere, a shadow (and, by being framed by shadows, the light flooding in through windows) typically moves in a clockwise direction, from westerly, then north, then easterly. Similarly, shadows in the Southern Hemisphere move counter-clockwise, from a western direction, via south, eventually towards east. The light from the window in the comic is predicted to move from the center to the left, a clockwise rotation, consistent with the comic being set in the Northern Hemisphere, especially as this comic has been released almost in the middle of the time of the year where this scenario happens only to places north of the equator.

(The declinated angle of the Sun through the window is hard to measure, and without even knowing the time of day we cannot hope to further narrow down the true latitude of the location and which direction the window faces. It is typical that, in temperate northern latitudes, major windows like the one shown are set to face as close to south as the orientation of buildings/rooms allow, to make the best use of daylight, particularly in the winter months. It is also not an unreasonable assumption that this meeting (or perhaps meal) is occurring not long before/after noon, or even during it, with the Sun then approaching its zenith. Overall, it would be possible to see something very like this scene play out for [[Randall]] in his current home location, of around 42°N, at this time of year.)

The title text talks about another minor "superpower" that astrophotographers have, which makes clouds always seem to show up in front of the night sky. This "ability" is really just an example of {{w|Murphy's Law}}: astrophotographers may feel that clouds always appear when they do because they interfere with their work by ruining their photos, making their presence more noticeable than their absence. This unhelpful effect is why it is claimed that this is more accurately considered {{tvtropes|BlessedWithSuck|a curse}}. If it was a conscious ability it could sometimes helpful, by giving them the power to move clouds in front of the Sun to provide shade.

==Transcript==
:[Cueball, Megan, and White Hat are in a large, relatively dim room, presumably a restaurant, with two tables and a large window with 4 panels and an integrated semi-circular 'fanlight' top-section. The window is casting a large window-shaped sunbeam between the two tables.]
:Cueball: Let's take the far table.
:Cueball: The closer one will be in the sun soon.
:[Caption below the panel:]
:Astrophotography gives you exactly one extremely minor superpower.
{{comic discussion}}<noinclude>

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Photography]]

413: New Pet

2026-06-12T14:10:38Z

82.132.236.149: /* Explanation */ There are three CNs in here... Probably too much.

{{comic
| number = 413
| date = April 21, 2008
| title = New Pet
| image = new pet.png
| titletext = ONE LAPTOP PER HAMSTER!
}}

==Explanation==
[[Megan]] and [[Cueball]] create a new pet by putting an {{w|Eee PC}} into a {{w|hamster ball}}, allowing it to roll around. They teach it various commands, and it appears to learn and make friends, despite neither Eee PCs nor {{w|Roombas}} - the 'friend' in question, having feelings.{{Citation needed}} Pleased with their creation, Megan then expresses disapointment it cannot be given a soul. However, Cueball instead uses made-up Python command 'import soul' to give it one. {{w|Python (programming language)|Python}} is a programming language popular among geeks running Linux. Among other features, it has a large number of easily installed 3rd-party libraries that make it easy to add features (stored in ''modules'') to programs - though a 'soul' module is not one of them!{{Citation needed}}. This section is a reference to [[353: Python]], in which Cueball is able to fly by importing the (''then'' fictional) <code>antigravity</code> module.

The {{w|Asus Eee PC}} was one of the first subnotebook computers available on the American market, noted for its small size and coming pre-installed with Linux. With a diagonal size of 11 inches, it would take a big hamster ball to carry it like this.

{{w|Omniwheel}}s are wheels with rollers mounted on the edge to allow the wheel to slide sideways. The wheels in the drawing look more like {{w|Mecanum wheel}}s, which have rollers mounted at an angle to the edge. Both omniwheels and Mecanum wheels are used in omni-directional drive systems, like you would use to drive a hamster ball from the inside. A {{w|webcam}} is connected magnetically to the top of the hamster ball, which connects to an rf link to transmit wirelessly to the computer.

TCO is {{w|total cost of ownership}}, which is exactly what it sounds like: the purchase price of something, plus all costs of keeping, operating, and/or maintaining that something. It's used in accounting to determine something's true cost-to-value evaluation. In the case of a cat, TCO would primarily consist of food, litter, veterinary care, etc. Refer to [[#Trivia|trivia for more details]]. For the device in the comic, there would be a small ongoing cost (occasional recharges for the batteries) after the initial investment.

{{w|Python (programming language)|Python}} is a programming language popular among geeks running Linux. Among other features, it has a large number of easily installed 3rd-party libraries that make it easy to add features (stored in ''modules'') to programs. In this case, [[Cueball]] is importing the (fictional){{Citation needed}} <code>soul</code> module to give the new pet a soul. This is a reference to [[353: Python]], in which Cueball is able to fly by importing the (''then'' fictional) <code>antigravity</code> module.

The title text refers to the {{w|One Laptop per Child}} project spearheaded by Nicholas Negroponte around 2005, with the goal of building an inexpensive, durable sublaptop that could be distributed to children in developing countries to give them an educational edge.

==Transcript==
:[Megan is placing EEE PC inside hamster ball. Cueball scratches his head.]
:Cueball: What are you doing?
:Megan: Mounting your EEE PC in a hamster ball.

:Megan: Well, the TCO of a cat is like $1,000/year, so we're saving money.

:[Cueball is typing.]
:Megan: Microcontrollers are all wired up! How's the brain coming?
:Cueball: I've taught it obstacle avoidance and blogging.

:Cueball: Aww, look, it's making friends with the Roomba.
:EEE PC: ''RRRRR''
:Roomba: ''Beep!''

:[A blueprint in the background shows a webcam, RF links, bearings, omni wheels, magnets, EEE PC, omni wheels, and a battery all hooked up to Megan and Cueball's "pet."]

:[Hamster ball bounces down a flight of stairs.]
:Hamster ball: ''Bonk bonk''
:Off-panel: Man, I hope it's okay that we're laughing at this.

:[Megan picks up a ball.]
:Megan: I think my mothering instinct took a wrong turn somewhere.
:Cueball: You mean an <u>awesome</u> turn.

:[Cueball is typing.]
:Megan: Too bad we can't give it a soul.
:Cueball: Sure we can.
:Cueball types: import soul
:Megan: Oh, right. Python.

==Trivia==
*According to [http://www.peteducation.com/article.cfm?c=1+2137&aid=1542 Pet Education's list], the TCO for a cat is between 310 and 1169 USD per year.
*In January 2020, Samsung named the pet{{Citation needed}} [https://www.youtube.com/watch?v=c7N5UDZX7TQ "Ballie"] ([https://web.archive.org/web/20200107091102/https://www.youtube.com/watch?v=c7N5UDZX7TQ WayBack archive]), while Python support has not been confirmed yet.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics with inverted brightness]]
[[Category:Comics with color]]
[[Category:Charts]]
[[Category:Hamster balls]]
[[Category:Programming]]
[[Category:Robots]]
[[Category:Roomba]]

Talk:3257: Beam Pipe

2026-06-12T12:53:40Z

82.132.236.149:

Ok why did this take so long to be created? [[User:GSLikesCats307|GSLikesCats307]] ([[User talk:GSLikesCats307|talk]]) 12:58, 11 June 2026 (UTC)
:I think it was because explainxkcd was down when this comic was published (agian :/) --[[User:Clarkexckd8|Clarkexckd8]] ([[User talk:Clarkexckd8|talk]]) 13:01, 11 June 2026 (UTC)
::It was like that with the last comic as well. What's causing these outages? [[User:GSLikesCats307|GSLikesCats307]] ([[User talk:GSLikesCats307|talk]]) 13:03, 11 June 2026 (UTC)
::: Maybe it's something with the servers. I have no clue why it took until 12:00 (UTC) to upload though.--[[User:Clarkexckd8|Clarkexckd8]] ([[User talk:Clarkexckd8|talk]]) 13:15, 11 June 2026 (UTC)
::::I'm going to theorise that some third party, out there, is running something that hammers our servers. From the little information the change-logs gives, they're starting it around 22:00 (server time) and it only ends (or people, including the comic-update-BOT, only realise it has ended) at around 12:00 (server time, again).
::::While this inconsiderate thing is happening, everyone else (and probably themselves, if they're running their hammering massivelg in parallel) is finding it ''almost'' impossible to connect, as the back-end is too busy serving the site-database results to the hammerer. (Some edits were made ~05:00ish, the other day. Might have been lucky/persistent to do that. Or hit a rare pause by the bad-actor's efforts.)
::::Probably not a deliberate DDOS, as these other periods of sanity wouldn't be in such a plan by someone. I suggest it's either someone/something doing (or trying to do) a lot of webscraping, without any though to throttling it down to a less disruptive level, or even an intended auto-spammer (getting thwarted by the initial hurdles that protect this site, but their spamming algorithm just keeps trying).
::::And the inconvenience to us mere mortals is as applicable to the comic-upload-BOT. The only difference being that it can (in a way programmed specifically ''not'' to self-defeatingly DDOS the site) just try again, perhaps every half an hour or so, so is more likely to be the first contributor to the site (when there's a new comic still to post, in its backlog) once the data-pummelling has stopped for the day.
::::What can we do about it? Not much. Curse the person who (intentionally or otherwise) did this? But it seems to not involve any traces of activity that aren't purely server-log level, or maybe on the prody servers that we also don't control. With any luck, they'll realise their (unintended) mistake and rethink it. Or just have no more reason to do so. Not very comforting, but the best outcome I can imagine happening easily. [[Special:Contributions/82.132.236.149|82.132.236.149]] 12:53, 12 June 2026 (UTC)

This is probably nitpicking, but covering the opening of a hose doesn't increase the pressure of the stream, it increases flow rate instead, and with it the nozzle velocity. The pressure at the end of a hose is equal to ambient pressure, and the flow rate adjusts itself to achieve this. (At least in sub-sonic conditions that you would normally encounter, though this may not apply to the LHC...) [[Special:Contributions/2A02:590:1404:9301:2CAC:E347:73BF:C11|2A02:590:1404:9301:2CAC:E347:73BF:C11]] 14:30, 11 June 2026 (UTC)
:Yeah, I noticed that... decreasing the diameter should actually decrease the pressure by bernoulli's law, right? [[Special:Contributions/12.159.97.176|12.159.97.176]] 14:31, 11 June 2026 (UTC)
::Yeah I was about to mention that too [[User:GreaterDog6065|GreaterDog6065]] ([[User talk:GreaterDog6065|talk]]) 14:55, 11 June 2026 (UTC)[https://www.explainxkcd.com/wiki/index.php/User:GreaterDog6065 GreaterDog6065] 09:54, 11 June 2026 (CDT)

What if you put your hand in a particle accelerator: https://www.youtube.com/watch?v=8UgKki1tCKI
Also, LHC actually has two adjacent parallel beamlines (or beam pipes) each containing a beam, which travel in opposite directions. Cf. https://en.wikipedia.org/wiki/Large_Hadron_Collider#Design
--[[Special:Contributions/134.102.219.31|134.102.219.31]] 12:40, 12 June 2026 (UTC)