explain xkcd - User contributions [en]

1145: Sky Color

2022-09-29T09:45:26Z

B jonas: link 1818

{{comic
| number = 1145
| date = December 10, 2012
| title = Sky Color
| image = sky_color.png
| titletext = Feynman recounted another good one upperclassmen would use on freshmen physics students: When you look at words in a mirror, how come they're reversed left to right but not top to bottom? What's special about the horizontal axis?
}}

==Explanation==
The point of this comic is that often, curious children ask their parents simple questions about understanding how the world works. Often, although the question is simple, the answer is not. "Why is the sky blue?" is a common example, since most parents are not familiar with {{w|Rayleigh scattering}}, and thus are unable to answer the question.

[[Randall]]'s hobby is to make those questions even harder, so that the parents who ''are'' familiar with the subject (scientists, for example) will be stumped.

Another point of this comic is that we often think that we understand a scientific phenomenon (e.g. why is the sky blue?); however, a certain simple question (e.g. why isn't the sky violet?) can often uncover large gaps in our actual understanding.

{{W|Rayleigh scattering}} is the phenomenon that explains the color of the sky, where light of every wavelength gets scattered in the air by the inverse quartic (fourth power) of its wavelength as given in the comic. In the {{w|visible spectrum}}, blue light has a wavelength of 450–495 nm while violet has a shorter wavelength of 380–450 nm. Violet light does indeed get scattered more than blue light, however the lower portion of the spectrum for sunlight consists of blue light and eyes are much more sensitive to blue light than violet light. Furthermore, the sunlight contains more blue than violet to begin with as a result of the surface temperature of the sun. This leaves the impression of a blue sky. A good explanation, including why blue and not violet, can be found in [http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html Usenet Physics FAQ :: Why is the sky blue?], but note that human color perception [http://blog.asmartbear.com/color-wheels.html is more complicated] than described there. Xkcd later tackles the same question in [[1818: Rayleigh Scattering]].

The title text refers to a {{w|mirror image}}, and is discussed by the famous American theoretical physicist {{w|Richard Feynman}} in a famous BBC documentary [http://www.youtube.com/watch?v=6tuxLY94LXw], as one of the problems which he used to have fun with first years (British English for first year student or freshman).

A mirror image is a virtual image produced by the reflection of light on a mirror. It's common to think of images in mirrors as being reversed left-to-right, as any text held in front of us will appear flipped. This is actually an issue of perception. In a plane mirror, images are reflected directly: the left side of your body will be reflected in the left side of the mirror, and vice-versa. The source of confusion is that people tend to think of a mirror image the way we would think of a person facing us. When another person faces us, they turn around the vertical axis, placing their right hand on our left side, so seeing our left hand on our left side in a reflection ''seems'' like an inversion, even though it's a direct representation. By the same token, in order to hold text up to a mirror, we generally flip it around the vertical axis, so that the start of the text is on right, and the end on the left (in English, at least). When the mirror reflects this, we see the text as backward, but the mirror hasn't reversed it, we reverse it when we turn it toward a mirror.

In other words, the vertical axis is only "special" because we're used to objects turning around it, so we come to expect that reversal, instead of a reflection.

You can induce a mirror to reverse left and right only --- by standing next to it instead of in front of it, facing along the plane of the mirror itself. If you lift your right arm, you can clearly see your image's left arm raising, without having to adjust for frame of reference. Similarly, you can induce a mirror to reverse top and bottom only by holding it flat above your head or laying it flat on the ground and standing on it (or perhaps standing under a suitably equipped bedroom ceiling). See [https://youtu.be/1t4dOPxKgrY this] video for a demonstration.

==Transcript==
:[Science Girl and her mother, Megan, but with her hair up. Megan is at a desk and facing the girl.]
:Science Girl: Mommy, why is the sky blue?
:Megan: Rayleigh scattering! Short wavelengths get scattered ''way'' more (proportional to 1/''λ''4). Blue light dominates because it's so short.
:Science Girl: Oh.
:Science Girl: So why ''isn't'' the sky violet?
:Megan: Well, because, uh... ...hmm.
:[Caption Below the panel:]
:My hobby: Teaching tricky questions to the children of my scientist friends.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Science Girl]]
[[Category:Physics]]
[[Category:My Hobby]]

Talk:2678: Wing Lift

2022-09-29T09:39:40Z

B jonas: reference to why the wing really produces lift

"The plane of the wing" - looks like Randall messed up on the title text [[User:InfoManiac|InfoManiac]] ([[User talk:InfoManiac|talk]]) 05:52, 29 September 2022 (UTC)
:Or maybe not: It's the plane of the wing of the plane! [[Special:Contributions/172.68.51.160|172.68.51.160]] 07:21, 29 September 2022 (UTC)
: Yeah, I also don't think that this is a mistake. The word "plane" is not used as the device that can fly but as the description for the (bottom) surface of the wing. One word for two totally unrelated things. I removed the trivia-part. https://en.wikipedia.org/wiki/Plane_(geometry) vs https://en.wikipedia.org/wiki/Airplane [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 09:23, 29 September 2022 (UTC)

If you want to know how a wing really produces lift, it's complicated, and the best reference on the net for that is [http://www.av8n.com/how/ See How It Flies]]. [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 09:39, 29 September 2022 (UTC)

Countdown in header text

2022-01-27T08:06:56Z

B jonas: revert 224735 16:28, 18 January 2022‎ Kynde and 224794 04:02, 19 January 2022‎ Sure and 224793 06:42, 19 January 2022‎ 172.70.114.99, which deleted the mention of EST then re-added a version of it that makes less sense

{{comic
| date = January 10, 2022
| title = Countdown in header text
| image = Countdown_in_header_text.png
| before = The countdown will probably last 21 days. After February 1st 2022 it is likely to have disappeared. See this [https://web.archive.org/web/20220110183238/https://xkcd.com/ 2022-01-10] archive version.
| ldomain = www
| lappend =
| extra = yes
}}
*Go directly to the list of [[Countdown in header text/images|images]].
**Or [[Countdown in header text/images#newestpicture|Jump to the newest picture]]
***The images can also be found [https://munvoseli.github.io/xkcd-countdown/ here] on munvoseli's page where comparison of two images and an animation can be seen.
{{TOC}}
==Explanation==
*On January 10th 2022, [[Randall]] added a countdown in the top right corner of the [[xkcd Header text]] on {{xkcd}}.
**This happened while the comic [[2565: Latency]] was up.
***First the xkcd Header text was [[xkcd_Header_text#2022-01-08_-_Back_to_standard_text|changed back]] to the [[xkcd_Header_text#Header_text|standard text]] for the first time in almost three years:
****xkcd updates every Monday, Wednesday, and Friday.
***But already while this Friday-comic was still up on the following Monday the [[xkcd_Header_text#2022-01-10_-_Standard_text_with_countdown|countdown]] was added.
****This was thus up when the Monday comic [[2566: Decorative Constants]] was released, drawing more people to the xkcd page.
*The first [[#Archived Versions|archived version]] from [https://web.archive.org/web/20220110183238/https://xkcd.com/ 2022-01-10] read 20d 20h 27m.
**It looks like it started on [https://munvoseli.github.io/xkcd-countdown/ 01-10 17:00 UTC].
***At that time it would have read 20d 21h 59 min. Just two hours and 1 minute short of 3 weeks.
*This countdown will reach zero on Monday 2022-01-31 at 14:59 (2:59 PM) {{w|UTC}}, or 9:59 AM in Boston, Randall's home town.
**If seconds will be added towards the end, it seems likely that it may end exactly at 15:00 UTC (10:00 AM in Boston).
***Further, the timer may be using [[1061:_EST|EST]], in which case it will count up for four hours on 2022-01-18, and will end on 2022-01-31 23:00 UTC.
****Though either way, it would fall on Monday, and therefore the day comic 2575 should be released.
****The full moon has since passed, and now we know that the timer isn't using EST, so it will indeed reach zero at or near 2022-01-31T15:00Z.
*The next day on [https://web.archive.org/web/20220111153818/https://xkcd.com/ 2022-01-11] a diagonal black bar appeared in the lower left-hand corner of the countdown box and started to move further into the image on following changes to the [[#Images|image]].
**This development called for the creation of this dedicated [[Countdown in header text]] page.
**The line had already moved further into the image at this time, but the latest version will never be available in the web archive.
***This development is reminiscent of the huge comic [[1190: Time]].
*As mentioned above, [https://munvoseli.github.io/ Munvoseli] is keeping [https://munvoseli.github.io/xkcd-countdown/ track of the changes] to the image on the countdown.
**Although there are (at 2022-01-12 12:35 UTC) thirteen different frames we know of, the first three looks the same (because the diagonal bar was not in the frame yet) and the seventh and the eighth also seems to be the same, even though the bar had already begun moving across the frame from the fourth. This is either on purpose, a slipup or means that The FrameTM might not be zooming out of a larger image.
***However, the images that look the same all have individual addresses on the xkcd server. See more under [[#Images|Images]] below.
***Similarly, frames 91 and 92 seem to be exactly the same. Also frame 92 did not upload as part of the roughly four hour schedule, but between two frames that are part of the regular schedule.

Randall has previously made a comic simply called [[1159: Countdown]]. However, in that the roles are reversed. There we know that the countdown is for (Super Volcano) but not if it will happen soon or very much later. Here we know when, and it is rather soon, but not what.

==Images==
*Images will be put on [[Countdown in header text/images|this separate page]].
**The images can also be found [https://munvoseli.github.io/xkcd-countdown/ here] on munvoseli's page.
***It is possible to compare two images, chosen between those released, on that page!
***From 2022-01-14 it has also been possible to see an animation.
**See more details at the top of the image page.
*After a few days the black lines forming the image came into conflict with the clock, which has a rounded white frame around it. This can be seen in one of the earliest examples here:
[[File:Countdown in header text Clock Cover Black Lines.png]]
*Also at this time a new development happened after the "plane tail" moved forward it stopped on 2022-01-18 and started moving up (or zooming in). See for instance these two comparison from munvoseli's page showing the difference from the 8 pictures before today, and then after three out today:
[[File:Countdown in header text Compare 40 to 48.png]] [[File:Countdown in header text Compare 48 to 51.png]]
*Later a similar change happens, as it changes from zooming out to slowly moving towards the right, although the windows and the door appear to move more in relation to the frame than the rest of the aircraft:
[[File:Countdown in header text Compare 85 to 90.png]] [[File:Countdown in header text Compare 95 to 90.png]]

===Ongoing description===
** Frames 1-12: A diagonal line.
** Frame 13: A curve seems to begin at the top left of the line.
** Frame 18: The curve connects the diagonal line with a horizontal line.
** Frame 27-28: A new line appears in the bottom left corner.
** Frame 40-42: The new line turns out to be connected to the horizontal line, forming a corner which is not attached to any other line.
** Frame 49: The "camera movement" direction changes, while the object is still moving upward it stopped moving towards the left side, moving towards the right instead.
** Frame 54: A slight upward curve seems to appear in the right line, the left line seems to have a small bend downwards, though that could at that point just be a straight line that Randall drew without a ruler.
** Frame 60-62: A new line appears in the bottom right corner, it turns out to be a continuation of the first original line which curves upward and has a positive slope at that point of the picture, between about 2 o'clock and 3 o'clock. The downward bend of the left line continues on straight in the same direction, it was probably an intentional bend and not an irregularity in drawing a straight line by hand.
** Frame 63: In the minimum of the right curved line a new line starts appearing, way thinner than the others (which were up to this point all rather part of one line) and going slightly downwards and very much to the left, at an angle somewhere between 8 o'clock and 9 o'clock.
** Frame 67: A possible feature becomes visible at the bottom edge of the image that might resolve the exact nature of the (currently presumed) aircraft, e.g. which particular aerodynamic surface we have been seeing and thus from which particular orientation we are viewing it.
** Frame 68-72 makes it clear this must be an aircraft by showing windows and a door and clearly the tail fin. As late as frame 69 some people argued that the tail fin could have been a wing.
** Frame 73-83 brings a horizontal stabilizer into view.
** Frame 87-89: A new curved line appears on the underside of the (presumed) aircraft, so there either is something behind it or it might not be an aircraft.
** Frame 96-99: An arc is coming into view in the upper right corner, likely the top edge of a cloud.
*** Turned out not to be a cloud.
** Frame 101-107 seems to be some kind of radar on top of the plane, like the one on {{w|Boeing E-3 Sentry}}. Or alternatively this plane is hanging beneath another plane. Not looking at all like {{w|Spaceshiptwo}}, but something similar, which could make this plane a spaceplane?

==Theories==
*Here are different theories for what the countdown is for and what the picture is going to reveal can be added.

===The picture===
*Theories about the picture:
**From 2022-01-21 it became certain that it was a plane! Passenger plane. Door and windows are visible.
***From 2022-01-22 it became clear that it was the rear end, so it was a tailfin that came into the panel to begin with. Up til the day before it was still a bit uncertain if it could have been a wing.
*** from 2022-01-24 a bottom line has appeared which doesn't fit well with a 'standard' airliner. perhaps the image is deliberately misleading (eg will transform into something else)
*** From 2022-01-26 something looking like a radar like the one on a {{w|Boeing E-3 Sentry}} began emerging in the top right corner.
**What will this lead up to - theories about this.
***It could be an airplane with a banner like in [[1355: Airplane Message]].
****That would very soon be clear as the bottom part of the rear end seems to be coming into view during 2022-01-24, if the direction does not change again.
*****This is now ruled out, since the plane is clearly not towing a banner.
***It could end up landing in a city, perhaps with a skyline pinpointing where Randall will be or move.
****However, unlikely to manage this in real life as the count down ends.
****Also, very unlikely (1 in 60, or even 1 in 3600) that such a landing would occur exactly on the hour.
*****But it could also just be the time when he announces he has moved...
***Maybe Cueball will make a parachute jump, and Cueball could represent a real life Randall, as this could in principle be timed very accurately.
****This is something you would schedule a month or more ahead, want to tell people about in advance, want to make a big deal about on your website, is not quite as bizarre as zero-G and probably more fun {{citation needed}}, could be done with an adventurous wife, explains why it’s the tail of the plane in the image, and (assuming no mechanical, medical, or meteorological problems, a safe assumption), might go something like “on my mark, it’ll be 9:59:56 A.M. in Boston... mark. 3, 2, 1, JUMP!” Maybe it’ll be just Cueball/Randall, but could more likely include Megan representing his wife.
****However, it could very easily be that the weather in January could foil the attempt, or at least the timing.
****The plane appears to be a commercial jetliner, though, rather than the small prop planes used for parachute jumps. Unless, of course, Randall is revealing his real identity has been Wesley Snipes all along

====Early theories====
Many early theories were generated before the picture was decisively revealed to be a plane.

*It seems after two days and 12 pictures like either something is moving into the frame or that it is a zoom out from a white area of a large picture. Maybe it is the arm of Cueball that will come into view.
*The second line makes it look somewhat like the tail fin of an aircraft.
**Or the wing of an aircraft (left if looking down at it). Perhaps the plane is towing a banner that will fly through the frame.
***After almost a week this looks like the most promising suggestion so far. Now that the direction of the camera movement has changed, we might get to see the rest of the aircraft soon.
****From picture 63, it more and more seems like it was the tail fin of a plane and now we can see the body.
*****It's almost certainly the tail (and now a bit of the rear fuselage) of an aircraft.
******It could just as easily be the left wing and part of the fuselage (showing windows on the right side of an airliner), with the tail fin out of view to the rear, as being the tail fin from an angle where the left wing is out of view behind the fuselage.
*******judging by the relative size of the (presumed) windows, I think it's more likely to be the left wing than the tail fin.
*******Based on the way planes are drawn in [[1868: Eclipse Flights]]. [[1355: Airplane Message]] and [[1669: Planespotting]], plane wings have a point on their edge and tail fins have a flat side, and (if a line is present) a thick line separates wings from the body, whereas thin lines or no lines separate tail fins, so this is a tail fin.
*******In the bottom left there appears to be the top part of a horizontal stabilizer, implying this is the tail.
********It’s a tail fin, that’s finally clear, but that’s the underside of the stabilizer. Which means this would be the best angle to view Cueball/Randall parachuting out of that door, something that would be predictable to the exact minute (barring all kinds of things that could go wrong).
*******Appears to be a door to the left of the windows
*******It could be an airplane with a banner like in [[1355: Airplane Message]]
***Tail of a space shuttle, perhaps?
****While I think Randall would've also drawn in the signature black part of the rudder, the shape fits perfectly
****Timing is close (though not exact) to the Columbia disaster anniversary (2003-02-01 1359 UTC)
***I'm thinking the tail of a Zeppelin.
****Although those normally have longer tail fins.
*Maybe it is some kind of vehicle rolling into frame, like a car?
*Or the word xkcd? (or xkcd 2?)
*Could have been "Hangman", but it looks like it's zooming in on the diagonal instead of continuing to make a gibbet.
*With the new second line appearing in the corner as of frame 28 it looks like it's definitely zooming out of an image. It looks like it could be someone's arm in a running position.
*I think it could also be two legs of a reclining stick person.
*The lines suggest a shark fin and the movement would suggest it swimming across the frame.
**If it was a shark fin, then the most likely candidates would be the first dorsal fin and the pectoral fin, but both end in points rather than edges like in the pictures of the header puzzle. An aircraft tail fin still seems most likely.
*Maybe it's a two-dimensional shape viewed from a weird angle?
**Like a rectangle viewed from a floating, tilted perspective
**Or the top of the k in xkcd
**Or a boat dock?
*The r/xkcd subreddit produced some early theories :
**Cueball's arm
**The letter D, as in "The End"
**A spider's web, in reference to comic 1688
***With the airplane revelation, this reference turned into a meme in the subreddit, where users tried to justify the presence of an airplane shape inside a bigger-scope spider picture
***Some joke theories included:
****A giant spider flinging airplanes from the sky, as a new potential "What If?"
****The lines are a web and the apparent windows the eyes of a giant spider
****The airplane is a complex-looking spider leg, and 8 of them form a spider
***Another redditor made the airplane part of a dragon's head

===Countdown===
*Theories about the countdown:
*Several have already been mentioned in the discussion:
**Maybe Randall is going on vacation?
**Notice that as of now - 22-Jan-2022 7am PST - (not sure exactly when it happened) the countdown has disappeared. Temporarily (perhaps to make the image cleaner?) or permanently? [[User:Pharmacovigilant|Pharmacovigilant]] ([[User talk:Pharmacovigilant|talk]]) 15:38, 24 January 2022 (UTC) The next time I looked (Sunday?), the countdown was back. No idea if it was a glitch or what.
**Randall's next book, either the countdown is counting down to the start of promotion or it is released when the countdown ends.
***Usually Randall has made month long [[:Category:Book promotion|book promotions]] before release. So if it is the release day it is a new way to do it. But he will get a lot of attention. If it is just the start of promoting it, people might get disappointed…
****For instance he began promoting his [[xkcd_Header_text#2015-05-14_-_New_book_Thing_Explainer|new book Thing Explainer]] in the header text. That was in May 2015 and the book was first released [https://blog.xkcd.com/2015/05/13/new-book-thing-explainer/ late November 2015]. Most of this time the header text was promoting the book.
**{{w|James Webb Space Telescope}} (JWST) going into orbit about L2 {{w|Lagrange point}}.
***Randall has already made several comics about the telescope. The latest [[2564: Sunshield]] was released just five days prior to the countdown was started.
***But the telescope will not reach the point but rather go into a large orbit around it, so a precise timer counting down to it seems a bit farfetched.
***On NASA's page on JWST it seems like it will [https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplorer.html#25 go into orbit] 29.5 days after its [[December 25th Launch]], on Christmas Day, so it should have already started the orbit by the 23rd or 24th of January - 8 days before the countdown.
***Also No based on the image.
**{{w|Lunar New Year}}
***In China it starts on February 1st and a [https://yourcountdown.to/chinese-new-year countdown for China] is 8 hours behind.
****The South Korean time zone is UTC+9, hence 14:59 UTC = 23:59 in South Korea, one minute to Feb 1.
*****But it's weird if Randall that has basically never mentioned this holiday suddenly makes a three week countdown for it, and why choose South Korea when most would think of China in this context…?
**Randall will stop making xkcd (Goodbye in the image).
***Hopefully not.
****Agreed, {{tvtropes|PoisonOakEpilepticTrees|to be avoided}}
***It might be a temporary stop (hiatus).
**[https://nationaldaycalendar.com/backward-day-january-31/ National Backward Day]
***This is not a day mentioned on Wikipedia at the time of release of the countdown, so seems unlikely.
**Maybe it will be an announcement of xkcd 2, a new and improved version for… some reason?
***Seems unlikely…
**{{w|Black History Month}}. The {{w|Greensboro sit-ins}} started on Feb 1 1960. Black History Month also begins on February 1st, also in 2022.
***But this countdown stops early on January 31st so seems unlikely.
***However, before changing the Header recently it was about [[xkcd_Header_text#2020-06-03_-_Black_Lives_Matter|Black Lives Matter]] for more than 1.5 years, first ending on December 20th 2021, less than a month before the countdown began. In between that there was a short Christmas sale reminder until a week into 2022. So it could just be another way of reminding of us the issues faced by black people in the US.
****If this was true, I feel like it would be simpler to just change back to the Black Lives Matter text at the top of the screen. Also, it seems increasingly likely as of Jan. 20th that the image is some kind of plane, which doesn't really have much to do with Black History Month (that I know of?)
**The accompanying header says specifically "xkcd updates Monday, Wednesday, and Friday"--maybe the countdown is to the reveal of a new update schedule?
***Very unlikely. This was the standard header for a long time. It was used when Randall had nothing better to say. But with all his books and the trouble in US with elections and BLM, he has used the header as a platform most of the time many years now. So the standard text is rare. But he did return it for two days before adding the count down, making it seem just like normal.
***A guess is that it returned to this, so the header text did not take any focus away from the countdown.
**[[:Category:Red Spiders|Red spider]] attack?
***Un-Likely
**He will become a father - could be a planned C-section.
***As this is unpredictable, and could go wrong, then this would be a dangerous countdown, people can be very superstitious, even if scientist.
**As it currently looks (after a [[1070: Words for Small Sets|few days]] into the countdown) it may be a trip he is taking by plane.
***Maybe going somewhere people could meet him.
****Book tour?
***Moving a long way from home (down under or the like).
****Maybe he's moving to Japan? Could be a plane, and the time zone would fit, at least.
*****Then the countdown would be until when the plane lands, not to midnight.
******What has time zones to do with this clock? It counts down to the same time all over the world, and will reach zero at the same time no matter what time zone you are in.
******Time zones have to do with where it will be midnight when the countdown reaches zero. If it's a countdown to when January ends (a moment before February begins), then it's until that moment in the time zone where the countdown reaches zero at that time.
****If it is a plane, then maybe it will land in a new city Randall moves to when the counter ends, and the skyline will be visible...
**Perhaps it's a start to a new series like [[1190: Time]].
***It is already a series that works like Time, so seems unlikely.
**Zero-G flight, really looks like plane to me.
***Could be time he will first go weightless which could be fairly well known except for bad weather
**A parachute jump by Randall. Could be predicted as well as the zero G.
**How about the [https://www.hitc.com/en-gb/2021/09/09/star-trek-picard-season-2-release-date-plot-cast/ new series of Picard]?
***{{w|Star Trek: Picard (season 2)}} is set to run from March 3 2022, which both Wikipedia (link before) and [https://www.imdb.com/title/tt8806524/episodes?season=2 IMDb] agrees upon so bad to miss by more than a month, and what would the plane in the image have to do with this anyway?
***So No!
** The xkcd world tour!! I wish
** I'm beginning to see another part of the picture entering into view, underneath the arc and above the body of the plane. To me, it looks like it could be a leg of sorts (Early bet: it could be a dinosaur)

===count-wimRikmef===
* The identifier of the script contains what is probably an acronym, but for what?
** count / wim (?) / Rik (name) & me f(light)
** Or it's just the output of whatever js minimizer was used.
** R = Randall?
* The "img" tag has a misspelled "heigth" attribute. Probably just a typo?

==Archived Versions==
;Seems like the links are (currently?) not working properly?
*Here is a list of the versions that has been saved to the web archive during the countdown.
**The counter in that version is written behind the date of the web archive.
**Note that the counter is active on the archived version counting minutes down from the start. Some of the versions almost changing the minutes just after loading. But it will always count from the time given here:
#[https://web.archive.org/web/20220110183238/https://xkcd.com/ 2022-01-10] 20d 20h 27m
#[https://web.archive.org/web/20220110214138/https://xkcd.com/ 2022-01-10] 20d 17h 18m
#[https://web.archive.org/web/20220111011115/https://xkcd.com/ 2022-01-11] 20d 13h 48m
#[https://web.archive.org/web/20220112005828/https://xkcd.com/ 2022-01-12] 19d 14h 1m
#[https://web.archive.org/web/20220113044552/https://xkcd.com/ 2022-01-13] 18d 10h 14m
#[https://web.archive.org/web/20220114010759/https://xkcd.com/ 2022-01-14] 17d 13h 51m
#[https://web.archive.org/web/20220114195624/https://xkcd.com/ 2022-01-14] 16d 19h 3m
#[https://web.archive.org/web/20220115052737/https://xkcd.com/ 2022-01-15] 16d 9h 32m
#[https://web.archive.org/web/20220116074923/https://xkcd.com/ 2022-01-16] 15d 7h 10m
#[https://web.archive.org/web/20220116225217/https://xkcd.com/ 2022-01-16] 14d 16h 7m
#[https://web.archive.org/web/20220118050255/https://xkcd.com/ 2022-01-18] 13d 9h 57m
#[https://web.archive.org/web/20220118195259/https://xkcd.com/ 2022-01-18] 12d 19h 6m
#[https://web.archive.org/web/20220119213308/https://xkcd.com/ 2022-01-19] 11d 17h 26m
#[https://web.archive.org/web/20220120103559/https://xkcd.com/ 2022-01-20] 11d 4h 23m
#[https://web.archive.org/web/20220121102349/https://xkcd.com/ 2022-01-21] 10d 4h 36m
#[https://web.archive.org/web/20220122002328/https://xkcd.com/ 2022-01-22] 9d 14h 36m
#[https://web.archive.org/web/20220122223018/https://xkcd.com/ 2022-01-22] 8d 16h 29m

{{comic discussion}}

[[Category:Meta]]

Countdown in header text

2022-01-18T14:23:18Z

B jonas: not EST

Countdown in header text

2022-01-17T16:16:34Z

B jonas: /* Explanation */

Talk:1801: Decision Paralysis

2017-02-20T11:26:55Z

B jonas:

[[309:_Shopping_Teams]] is also directly relevant. [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 11:26, 20 February 2017 (UTC)

== Don't hurt me ==
First explanation. There's serious problems with it, I know. Be gentle. [[Special:Contributions/162.158.62.159|162.158.62.159]] 05:59, 20 February 2017 (UTC)

== Nerd sniping ==
[[356: Nerd Sniping]] appears to be a practical application of this. [[Special:Contributions/162.158.114.16|162.158.114.16]] 09:14, 20 February 2017 (UTC)

434: xkcd Goes to the Airport

2016-12-22T11:13:53Z

B jonas:

{{comic
| number = 434
| date = June 9, 2008
| title = xkcd Goes to the Airport
| image = xkcd_goes_to_the_airport.png
| titletext = Under three ounces, but it stains panties.
}}

==Explanation==
The various characters of xkcd cause problems at the airport due to their various quirks.

Panel 1: [[Beret Guy]] and [[Megan]] are lost, following each other in a loop. Beret Guy displays his obsession with baked goods as he also does in later comics: [[442: xkcd Loves the Discovery Channel]] and [[452: Mission]].

Panel 2: [[Cueball]] tries to carry a {{w|Lock picking|lockpick set}} (a tool able to unlock doors without the original key) through security. The security guard tells Cueball that he has to come with him, but Cueball wants to tell the guard about "this hacker girl" before going with the guard. This may be spoofing the incidents where someone has been manipulated into smuggling drugs or other contraband by a romantic interest they met on the Internet. The hacker girl could be [[Elaine]] from the [[1337|1337-series]].

Panel 3: On the plane, Cueball has been instructed to disable the wireless transmission functionality of his device. Many airlines require passengers to disable {{w|Mobile phones on aircraft|mobile phones on aircraft}} as well as other radio transmitting devices because they may interfere with the radio-based navigation and communication equipment of the aircraft. However, his laptop is running Linux and he doesn't know how to change the wireless settings; he's reading the {{w|Man page|manual}} for the program that controls the wireless radio. However, this is probably not the ideal situation, as the airplane is pressed to take off. Man page was also referenced in [[293: RTFM]]. Much later a plane was again linked to a man page in [[912: Manual Override]].

Panel 4: [[Black Hat]] tries to carry a container of liquid through security. According to US law{{Citation needed}}, the maximum amount of liquid that can be taken onto a plane in a container is three ounces, a security measure taken to prevent terrorists from taking explosives onto planes. When the guard has doubts about the amount of liquid in the vial, Black Hat reveals that the liquid is actually blood from a churchmouse. This is a reference to [[526: Converting to Metric]], which claims that a fieldmouse has much fewer blood than that. The guard is visibly uncomfortable and clearly does not want to deal with the issue any further.

The title text continues off the final panel, saying that there are less than three ounces of blood in a churchmouse, but it "stains panties", an undesirable scenario. However, this undesirable scenario is paralleled by the implied undesirable scenario of a terrorist attack due to explosive liquids, the possibility of which caused the law. The title text seems to parody the prospect of an explosion with the relatively insignificant staining of panties, a term for women's underwear. This may also be a menstruation joke.

==Transcript==
:[Standing outside the Airport. There is a sign saying "Airport" and a plane in the background.]
:Megan: Okay, what airline?
:Beret Guy: I'm following you.
:Megan: ...I'm following you.
:Beret Guy: I assumed we were walking to the bakery.
:Megan: You always assume that!

:[Presumably the security checkpoint.]
:Security Guy: Lockpicks? These are... illegal, actually. Where did you get them?
:Cueball: Oh man, it all started with this hacker girl.
:Security Guy: You need to come with-
:Cueball: Sure, sure. But man, let me tell you about her!

:[On a plane.]
:Announcement: If your device has a "Transmit" function, please disable it.
:Cueball: Okay - hang on, I'm half way through the iwconfig man page.

:[Security checkpoint.]
:Security guy: Sir, is this container under three ounces?
:Black Hat: Not sure, how much blood is there in a churchmouse?
:Security guy: . . .Why don't you just go.

{{comic discussion}}
[[Category:Comics featuring Beret Guy]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Megan]]
[[Category:Linux]]
[[Category:Food]]
[[Category:Man pages]]

Talk:1762: Moving Boxes

2016-11-21T16:08:20Z

B jonas:

I think I've got some Dark Matter in a box left in my basement. Anyone knows how long you can keep this stuff until it expires? [[Special:Contributions/162.158.22.72|162.158.22.72]] 13:36, 21 November 2016 (UTC)
: Mine is about 13.8 billion years old and still OK. But shouldn't about 3/4 of the boxes be filled with dark matter? --[[Special:Contributions/162.158.91.172|162.158.91.172]] 14:21, 21 November 2016 (UTC)
: Hah! Mine's 13.8'''1''' years old.
--[[User:Thejohnfan|Thejohnfan]] ([[User talk:Thejohnfan|talk]]) 14:28, 21 November 2016 (UTC)Thejohnfan
::Yeah - you've really gotta be careful about labelling that stuff - since it neither absorbs nor emits electromagnetic radiation, you're going to have to use gravitational lensing techniques to figure out which box it's in - and we all know how much of a pain THAT can be on moving day! [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 14:59, 21 November 2016 (UTC)

:When I last moved house, I methodically labelled every single box with it's exact contents. Several meticulously itemized boxes contained (amongst other things) stuff like "Acrylic art paint", "Rodent poison" and "Adhesives" - and the movers saw this and refused to move about a dozen boxes because they contained things that are liquids or hazardous materials. This was more than I could fit in my car - so this became a huge deal. So next time, I'm going with "Normal House Stuff". Seriously - just label them with the room you want them dumped in at your new home and a number...write the actual contents in a MySQL database...preferably with a photo of the box before you taped it up. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 14:59, 21 November 2016 (UTC)
::Label the boxes with "Normal house stuff'); DROP TABLE Boxes; --" if you're doing that. [[Special:Contributions/162.158.34.137|162.158.34.137]] 15:16, 21 November 2016 (UTC)
:::How do you access the MySQL database when your computer is still packed away in a box? [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 16:08, 21 November 2016 (UTC)

Talk:1756: I'm With Her

2016-11-07T19:10:23Z

B jonas:

Instead of comic, post contained a political statement. I am not amused. I want a refund. I don't vote, and I don't even live anywhere near USA. [[Special:Contributions/141.101.96.102|141.101.96.102]] 18:40, 7 November 2016 (UTC)

The "I'm with her" and H with an arrow are CLEARLY the respective campaign slogan and campaign logo for Hillary Clinton, not some vagueness having to do with bringing a significant other. --[unsigned]
:I see it more as him endorsing voting regardless of who you vote for (as evidenced by half the comic is about "Here's how you vote" without any mention of candidates or issues) and the endorsing Clinton part is an add-on as if to say "This is how I'm voting; vote for her if you agree with me." [[User:Jeudi Violist|Jeudi Violist]] ([[User talk:Jeudi Violist|talk]]) 18:39, 7 November 2016 (UTC)

Has Randall endorsed a presidential candidate before? --[[User:Dfeuer|Dfeuer]] ([[User talk:Dfeuer|talk]]) 17:14, 7 November 2016 (UTC)
He supported Obama on his blog in '08, not in the comic though.

He could have said any number of clever things about the election, and all he did was put up a campaign sign. Disappointing. [[User:Gmcgath|Gmcgath]] ([[User talk:Gmcgath|talk]]) 17:37, 7 November 2016 (UTC)

what a cuck --[[Special:Contributions/172.68.51.63|172.68.51.63]] 17:45, 7 November 2016 (UTC)
:: leaving aside the most ridiculous slur of the past few years, I don't know what else did you expect from Randall. I guess you must have stumbled upon this wiki by chance and have never heard of xkcd before.--[[Special:Contributions/141.101.98.130|141.101.98.130]] 17:59, 7 November 2016 (UTC)
:: AHAHAHAHA. *Ahem.* Hooray for pejorative misappropriation of a kink. /s [[Special:Contributions/108.162.246.55|108.162.246.55]] 19:07, 7 November 2016 (UTC)

This is the first time I still don't get the joke even after reading the explainxkcd page [[Special:Contributions/108.162.219.123|108.162.219.123]] 18:09, 7 November 2016 (UTC)
== Bit disappointing... ==

I was hoping for a comic today. oh well. Interesting to see how he's planning to vote, though - it's a shame that there are no candidates this year in favor of strong encryption.

Funny how females outdo males in this 'comic' but in terms of frequency and of elevation. Oh well. xkcd has long been overrepresenting females, it was to be expected. <nowiki>~~~~</nowiki>

Seriously? You're whinging 'what about the men?' in a geek web comic?! [[Special:Contributions/108.162.215.212|108.162.215.212]] 18:21, 7 November 2016 (UTC)

The only disappointing this are comments like those two above. [[Special:Contributions/162.158.201.96|162.158.201.96]] 18:11, 7 November 2016 (UTC)
: Females being overrepresented in comics like xkcd (but also other ones) with respect to their controlled interest in science in reality is a fact. Therefore, you are calling facts disappointing. How geeky of you. <nowiki>~~~~</nowiki>

A little disappointing to have a normally lighthearted comic dive seriously into politics, if even for one strip. Not really a fan of either candidate, but would like to see stuff like this stay above the fray.
:Completely agreed. [[User:SeanAhern|SeanAhern]] ([[User talk:SeanAhern|talk]]) 18:27, 7 November 2016 (UTC)

This is a first... comics 500 and 1130 (possibly 1131 too) were related to the election, but didn't endorse a candidate. I'm not entirely sure how I feel about this. [[Special:Contributions/108.162.219.89|108.162.219.89]] 18:41, 7 November 2016 (UTC)

I came here to see what the tone of the comments were going to be. I was half expecting to find an all-out flamewar in progress. I was happy to see that the comments have not devolved into the kind of attacks that one would expect to find pretty much anywhere else on the Internet. Geeks are the best people. :) [[User:Mwburden|mwburden]] ([[User talk:Mwburden|talk]]) 18:47, 7 November 2016 (UTC)

I'm very dissappointed. Randall never took sides before and - be it as it may - this comic is not a comic but plain out political campaign. Up until now I held xkcd in EXTREMELY high esteem - this comic put a serious dent in that opinion..
--[[Special:Contributions/162.158.91.60|162.158.91.60]] 18:56, 7 November 2016 (UTC)

Can you help list all the characters in the transcript? From left to right; they're Joanna (ponytail with EMP cannon) from [[322]]; Black Hat; unknown with kite; White Hat; possibly Miss Lenhart (but his hair is somewhat different from [[1519]]); unknown possibly Megan; cueball; unknown woman with glasses; Hairbun; Beret Guy; Cueball with toy sword from [[303]]. [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 19:10, 7 November 2016 (UTC)

1053: Ten Thousand

2014-11-10T07:39:07Z

B jonas:

{{comic
| number = 1053
| date = May 9, 2012
| title = Ten Thousand
| image = ten_thousand.png
| titletext = Saying 'what kind of an idiot doesn't know about the Yellowstone supervolcano' is so much more boring than telling someone about the Yellowstone supervolcano for the first time.
}}

==Explanation==
This is certainly a great approach to take with someone that doesn't know something, rather than taking the "idiot" approach. For all those who haven't yet seen the {{w|Diet Coke and Mentos eruption}}: here is a [http://www.youtube.com/watch?v=LjbJELjLgZg Mythbusters video], and [http://www.youtube.com/watch?v=PQHPYelqr0E a music video] (Pork and Beans by Weezer) with excessive eruptions. The Mentos eruption is mentioned in a previous strip [[346: Diet Coke+Mentos]].

The rate 10,000 per day of hearing about it for the first time is just the birth rate of 4,000,000 per year divided by 365 days. The target age of thirty years is irrelevant on these numbers. For easier calculations let's compare the targets 10 and 100 years:
*10 years: 1,000 people in each age of one to ten years have to learn so everybody would know it by the age of ten.
*100 years: The rate per age is less and only 100 people in the age from one to hundred years have to get the picture.
Because the birth rate is assumed to be constant it would happen every year, exactly the amount of new born of people have to learn, but the target age isn't important. And this assumes also that really everybody would get it, which is a little bit unrealistic.

The title text emphasizes that explaining something to a person who doesn't know about is much better than just expressing annoyance about that missing knowledge. Just explain your knowledge to other people.

Here is a [http://www.youtube.com/watch?v=_PxDGiVQNg8 good video] about the {{w|Yellowstone supervolcano}}.

==Transcript==
:I try not to make fun of people for admitting they don't know things.
:Because for each thing "everyone" knows by the time they're adults", every day there are, on average, 10,000 people in the US hearing about it for the first time.
:Fraction who have heard of it at birth = 0%
:Fraction who have heard of it by 30 ≈ 100%
:US birth rate ≈ 4,000,000/year
:Number hearing about it for the first time ≈ 10,000/day

:If I make fun of people, I train them not to tell me when they have those moments. And I miss out on the fun.
:Megan: "Diet coke and Mentos thing"? What's that?
:Cueball: Oh man! come on, we're going to the grocery store.
:Megan: Why?
:Cueball: You're one of today's lucky 10,000.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Math]]

1445: Efficiency

2014-11-10T07:29:18Z

B jonas: link to 309: Shopping Teams

{{comic
| number = 1445
| date = November 10, 2014
| title = Efficiency
| image = efficiency.png
| titletext = I need an extension for my research project because I spent all month trying to figure out whether learning Dvorak would help me type it faster.
}}

==Explanation==
There are often multiple ways in which to deal with a problem or task. Generally, some methods are more efficient than others, though sometimes only slightly. Many people try to avoid unnecessary work by finding the easier of the methods, but this can prove to be more time-consuming than even just choosing the most difficult method. [[Randall]] cites this as the reason for his inefficiency.

The title text refers to the {{w|Dvorak_Simplified_Keyboard|Dvorak}} keyboard layout, an alternative to the almost universally accepted {{w|QWERTY}} layout, which some believe offers greater typing efficiency.

The title text sounds like an excuse given by a college student to their professor for why their project was not completed by the due date.

Another comic about too much resources spent on decisions that ultimately might not matter is [[309: Shopping Teams]]. A similar comic that addressed wasted time due to bad time management was [[1319: Automation]].

==Transcript==
:[A graph titled Time Cost]
:Strategy A
:[Short line beside A]
:Strategy B
:[Slightly longer line beside B]
:Analyzing whether strategy A or B is more efficient
:[A much longer line next to this, about 10 times the length of B]
:The reason I am so inefficient
{{comic discussion}}
[[Category:Charts]]

456: Cautionary

2014-04-27T17:48:39Z

B jonas:

{{comic
| number = 456
| date = July 30, 2008
| title = Cautionary
| image = cautionary.png
| titletext = This really is a true story, and she doesn't know I put it in my comic because her wifi hasn't worked for weeks.
}}

==Explanation==
Many people who use {{w|Linux}} start out not really knowing anything about other than that it's free. So, they find someone who knows about it to help them set it up.

XORG (officially {{w|X.Org Server|X.Org}}) is an implementation of the X window manager, a program responsible for the graphical display used on Linux. If it had configuration problems, which was quite common with some video card drivers back in 2008 (especially {{w|fglrx#Linux|the one for ATI Radeons}}), it is often difficult, painful or completely impossible to fix (see [[963: X11]]).

Linux has many versions, called "distributions". Each distribution, or "distro", has a different look and feel, and different features. {{w|Ubuntu (operating system)|Ubuntu}} is a "beginner" version of Linux, designed to just "work" and be friendly toward people used to Windows. {{w|Debian}} is a somewhat more advanced distro that requires more knowledge of Linux (and sometimes programming), and {{w|Gentoo Linux|Gentoo}} is a very advanced distro. Because she is fed up with Ubuntu trading functionality for ease-of-use, she switches to Gentoo. “Autoconfig issues” refers to [[416: Zealous Autoconfig]].

Some advanced users of Linux decide to compile their kernel from source. This basically means that instead of downloading Linux and installing it, they download the source code, change something, build the source code into a runnable version of the OS, and then use it. To many advanced users, their installation of Linux is like a house might be to a homeowner: A never-ending project, improved slightly every day, but modified more often than it's actually used.

In the final panel, she has become addicted to Linux, and as a heroin addict might take another dose, or a homeowner might paint something or move a picture, she might change a setting or two and recompile the kernel for her Linux OS.

The title text jokes about the bad {{w|Wi-Fi}} support of many then-common cards on Linux back in 2008.

==Transcript==
:Linux: A True Story:
:[Cueball talks on a cell phone.]
:Week One:
:Megan: Hey, it's your cousin. I got a new computer but don't want Windows. Can you help me install "Linux"?
:Cueball: Sure.

:[Megan sits in an office chair with her laptop on her lap. She is on the phone.]
:Week Two:
:Megan: It says my XORG is broken. What's an "XORG"? Where can I look that up?
:Cueball: Hmm, lemme show you man pages.

:[Megan crouches on the floor with the laptop on her lap. She is still on the phone.]
:Week Six:
:Megan: Due to auto-config issues, I'm leaving Ubuntu for Debian.
:Cueball: Uh.
:Megan: Or Gentoo.
:Cueball: Uh oh.

:[Megan lies on her stomach with the laptop on the floor. On the floor are several pieces of paper and a book. Cueball stands to her left.]
:Week Twelve:
:Cueball: You haven't answered your phone in days.
:Megan: Can't sleep. Must compile kernel.
:Cueball: I'm too late.

:[Box with text:]
:Parents: talk to your kids about Linux... Before somebody else does.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Linux]]

Talk:1359: Phone Alarm

2014-04-23T06:06:50Z

B jonas: Created page with "See also 479: Tones. ~~~~"

See also [[479: Tones]]. [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 06:06, 23 April 2014 (UTC)

Talk:526: Converting to Metric

2014-03-25T14:58:48Z

B jonas:

Why is 3L a two-liter bottle?[[Special:Contributions/75.69.96.225|75.69.96.225]] 21:16, 28 April 2013 (UTC)

:Because this is America and we supersize our sodas! {{unsigned ip|72.68.9.56}}

:It is the volume of the bottle itself. I have added this explanation. [[User:Sten|Sten]] ([[User talk:Sten|talk]]) 22:39, 29 August 2013 (UTC)

:A 2L bottle doesn't take 3L of space, not even close. I also think it's a reference to overly large drinks in the US. But even if it isn't, the current explanation is wrong. [[Special:Contributions/108.162.229.34|108.162.229.34]] 22:28, 12 December 2013 (UTC)

: I suspect he's just messing with us, because the approximate volume of a two-liter bottle should be obvious. Many beverages sold in the US are already labeled in metric. Soda is routinely sold in one and two liter bottles, with three-liter bottles common in some markets. Bottled water is often sold in liters and half-liters. Liquor and wine are sold in 375 and 750 mL bottles. Also, since 1 quart = 946 mL, an approximate (+/- 5%) mental conversion from quarts to liters is already quite easy. [[User:Fryhole|Fryhole]] ([[User talk:Fryhole|talk]]) 01:35, 25 January 2014 (UTC)

My names River, that is all --[[Special:Contributions/139.216.242.254|139.216.242.254]] 02:52, 29 August 2013 (UTC)

:Tick tock, goes the clock, 'till River kills the Doctor

Earth's hottest is 70,7 °C... [[Special:Contributions/199.27.128.29|199.27.128.29]] 03:06, 24 February 2014 (UTC)

:The world record as per wikipedia (and Guiness) is "only" 56.7. See corrected explanation above. [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 17:03, 6 March 2014 (UTC)

There was an incomplete asking for checking all measures and also for making sure that the references to serenity and velociraptors was mentioned. I did this, the last two by assigning the categories (firefly), and then also creating a new [http://www.explainxkcd.com/wiki/index.php/Category:Your_Mom category:Your Mom]. I now consider this explanation complete. Although if someone will speculate two whom the remaining two from the Serenity crew tower then please do so ;-) [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 17:03, 6 March 2014 (UTC)

The speed of rapors given here is very different from [[135: Substitute]]. [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 14:58, 25 March 2014 (UTC)

1010: Etymology-Man

2014-02-15T20:20:59Z

B jonas:

{{comic
| number = 1010
| date = January 30, 2012
| title = Etymology-Man
| image = etymology_man.png
| imagesize =
| titletext = I can't believe I'm saying this, but I wish Aquaman were here instead--HE'D be able to help.
}}

==Explanation==
This comic is a take on the traditional appearance of a super hero when a disaster strikes. In this case, Etymology-Man arrives, who apparently has the power of {{w|Etymology}} - the study of the history of words, their origins, and how their form and meaning have changed over time. As Etymology-Man is explaining the history of the words "{{w|tsunami}}" and "tidal wave", the water starts rising around them. As the waters continue to rise, he only continues explaining the words in an attempt to save them as a superhero should.

Also, the title text is a play on how useless {{w|Aquaman}} is (perceived to be) compared to other superheroes, as his powers -- breathing underwater, speed swimming, and communicating with sea life -- are very difficult for writers to make relevant. Indeed, in the case of a flood, Aquaman and his aquatic allies would be able to assist with evacuations.

Etimology man returns two comics later in [[1012: Wrong Superhero]].

==Transcript==
:Cueball: Earthquake!
:Ponytail: We should get to a higher ground - There could be a tidal wave.

:[Cueball takes a pedantic pose]
:Cueball: You mean a tsunami. "Tidal wave" means a wave caused by tides.

:[A crash is heard, followed by Etymology-Man flying in while wearing a cape]
:Etymology-man: You know, that doesn't add up.
:Cueball and Ponytail: Etymology-man!

:[Etymology-man takes a pedantic pose]
:Etymology-man: What ''does'' "tidal wave" mean? There are waves caused by tides, but they're "tidal bores", and they're not cataclysmic.
:It can refer to the daily tide cycle, but that's obviously not what people mean when they say "a tidal wave hit".
:It's been obvious for centuries that these waves come from quakes. So why "tidal"?

:Etymology-man: Remember that until 2004, there weren't any clear photos or videos of tsunamis. Some modern writers even described them rearing up and breaking like surfing waves.
:Of course, in 2004 and 2011, it was made clear to everyone that a tsunami is more like a rapid, turbulent, inrushing tide - exactly what historical accounts describe.

:[Water begins to rush in. Etymology-man keeps his pedantic pose]
:Etymology-man: Maybe those writing about Lisbon in 1755 used "tidal wave" not out of scientific confusion, but because it described the wave's form — a description lost in our rush to expunge "tidal wave" from English.

:[The water is now waist-deep. Etymology-man continues to drone on, but the others start to panic]
:Etymology-man: "Tsunami" is now the standard, and I'm not trying to change that. But let's be a tad less giddy about correcting "tidal wave" - especially when "tsunami" just means "harbor wave", which is hardly...

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Language]]

Talk:758: Raptor Fences

2013-11-01T23:35:19Z

B jonas:

Is the Cueball on the left holding a lit cigar? {{unsigned|‎Gegueure}}

The role of Samuel L. Jackson is played by Cueball in this film. [[User:ZevEisenberg|ZevEisenberg]] ([[User talk:ZevEisenberg|talk]]) 14:44, 9 August 2013 (UTC)

Does this remind you to Gulliver being attacked by tiny people in Liliput? Or the similar scene in [http://pbfcomics.com/95/ Perry Bible Fellowships strip 95: Gnome Bubbles] with the tiny gnomes? [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 23:35, 1 November 2013 (UTC)

Talk:202: YouTube

2013-11-01T16:31:28Z

B jonas:

In the transcript, it says simpleplan2009's comment was posted 3 minutes ago. However, in the image, it clearly says 5 minutes. [[User:Caagr98|Caagr98]] ([[User talk:Caagr98|talk]]) 19:01, 17 April 2013 (UTC)
:I agree. In theory a 3 and a 5 could be hand-written to be hard to differentiate, but here it is clear. Changed. (And added the first line.) [[User:Markhurd|Mark Hurd]] ([[User talk:Markhurd|talk]]) 10:56, 19 April 2013 (UTC)

On Gunpistolman's comment, is [http://www.phys.ufl.edu/~det/phy2060/heavyboots.html the heavy boots story] worth a mention? [[User:B jonas|B jonas]] ([[User talk:B jonas|talk]]) 16:31, 1 November 2013 (UTC)

599: Apocalypse

2013-11-01T16:28:21Z

B jonas: sqrt(163)

{{comic
| number = 599
| date = June 19, 2009
| title = Apocalypse
| image = apocalypse.png
| titletext = I wonder if I still have time to go shoot a short film with Kevin Bacon.
}}

== Explanation ==
According to Wikipedia, {{w|Paul Erdős}} (26 March 1913 – 20 September 1996) was a Hungarian mathematician who published more papers than any other mathematician in history, working with hundreds of collaborators.

An in-joke developed among mathematicians called the {{w|Erdős number}} (similar to a Bacon number for film actors, which we'll discuss in a minute). By definition, Erdős has an Erdős number of 0. Everyone who has co-written a mathematical paper with Erdős has an Erdős number of 1. Everyone who collaborated with them (but not Erdős himself) is assigned an Erdős number of 2. In general, if ''k'' is the minimal Erdős number of all the people you've written papers with, your Erdős number is ''k'' + 1. The Erdős number is the length of the shortest "chain" from you to Erdős.

Not everyone has an Erdős number, meaning that they don't have any chain linking them to Erdős. Most non-mathematicians do not have an Erdős number.

In this comic, the apocalypse happens. [[Cueball]] quickly writes a math paper and gets everyone from the math dept. to sign it. Then he gets the resurrected Erdős to sign it. This way everyone from the math dept. has an Erdős number of 1.

Paul Erdős described people who had stopped doing mathematics as "dead."

The title text mentions a similar (and less esoteric) meme called "{{w|Six degrees of Kevin Bacon}}", or simply Bacon numbers. This time, the chain's center is actor {{w|Kevin Bacon}}, and the links are formed by two people appearing in the same movie. Unlike Erdős, Kevin Bacon is not dead, so those of you wishing to get a Bacon number of 1 still have a chance.

One of the mathematical scribbles appearing in panel 5 shows the square root of 163, which may be a reference to {{w|Ramanujan's constant}}.

==Transcript==
:[Scene of meteors showering the earth.]

:Beret Guy: The apocalypse! The skies burn, the seas turn to blood, and the dead walk the earth!

:[Cueball and Beret Guy.]
:Cueball: The dead what?
:Beret Guy: Walk the earth!

:[Cueball running.]
:Cueball: I have to go.

:[Cueball scribbling at a table. Mathematical symbols and equations are above Cueball's head.]
:''Scribble scribble''

:[Cueball running, paper in hand.]

:[Cueball opening door labelled "Math dept."]
:Cueball: The dead return!
:Cueball: Everyone, quick, get your names on here!

:[People lining up.]
:Woman signing paper: At last!
:Man in line: I hope there's still time!

:[Cueball running.]

:[Cueball at a cemetery.]
:Rising dead: ''Hurrghhh''

:[Cueball finds a man rising from his grave.]

:Cueball: Paul Erdős?
:Erdős: Yes?
:Cueball: We need you to sign this.

{{Comic discussion}}
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