explain xkcd - User contributions [en]

3132: Coastline Similarity

2025-08-25T09:31:36Z

85.159.196.156: /* Explanation */

{{comic
| number = 3132
| date = August 22, 2025
| title = Coastline Similarity
| image = coastline_similarity_2x.png
| imagesize = 553x219px
| noexpand = true
| titletext = Hey! A bunch of the early Cretaceous fossils on each coast seem to have been plagiarized, too!
}}

==Explanation==
{{incomplete|This page was created by a HUMAN, BUT IT WAS PLAGIARIZED BY A BOT. Don't remove this notice too soon.}}

This comic depicts a classroom, likely relating to geography, geology or history, in which the teacher ([[Miss Lenhart]]) is discussing the similar coastlines of Africa and South America, and the way that modern understanding has revealed the cause. [[Cueball]] initially assumes that one coastline plagiarized the other before Miss Lenhart continues by revealing that it was {{w|continental drift}} that explained the similarity.

Continental drift is the widely accepted theory that Earth's continents were once all connected, and have been moving relative to each other due to {{w|plate tectonics}}. One of the clues that actually led to this discovery was that the shapes of the coastlines of South America and Africa that are separated by the Atlantic Ocean are similar. The similarity is much greater for the submerged {{w|continental shelf|continental shelves}} than for the visible coastlines; they're like adjacent pieces of a jigsaw puzzle.

{{w|Plagiarism}} is the act of claiming credit for another individual's work, usually by duplicating the results. The discovery of plagiarism in an already-renowned body of work is often cause for scandal, and Cueball's reaction to the assumed plagiarism of the African/South American coastlines reflects this. Of course, continents are inanimate objects, and have no concept of plagiarism, let alone know how to perform it{{Citation needed}}. However, depending on your definition of plagiarism, because the continents don't give "credit" to the other continent, this may be viewed as plagiarism with a very broad definition of plagiarism.

The title text continues the joke about plagiarism. Additional corroborating evidence of continental drift is that there are similar species of plant and animal fossils on the two sides of the Atlantic, dating to the time when they were connected. Cueball thinks that the progenitors of these species also plagiarized each other, as opposed to the more mundane explanation which is that the progenitors were the ''same'' for both. The younger fossils are descendents of some species that existed across the once-connected lands, the older ones ''are'' the species that did not yet have the nascent Atlantic Ocean in their lives.

This is a very rare example where it is not Miss Lenhart that makes a joke as the teacher, but actually teaches the accepted truth, and it is instead here one of her pupils that makes the joke (intentionally or not). A much more typical scenario for her teachings could for instance be seen in [[1519: Venus]].
The theory of continental drift was originally proposed by Alfred Wegener in 1912, based on such fossil evidence and other geological features common to the two continental borders, in addition to the similarities in shoreline shapes. It's significant to the history of science as a general subject, as a proposal that was originally met with strong opposition (not to mention mockery) but eventually became accepted by almost everyone. Modern cranks and crackpots sometimes point to it in support of their own implausible "theories", as though universal rejection of a "theory" by all of the experts somehow proves that it will someday be accepted and its originator proven right all along. In fact, Wegener's original theory did have a serious flaw, in that it lacked a plausible mechanism, though it was otherwise correct. Modern cranks' "theories" generally lack both plausible mechanisms ''and'' good analysis of supporting evidence. ("Yes, they laughed at Galileo... but they also laughed at Bozo the Clown.")

==Transcript==
:[Miss Lenhart is holding a pointer pointing to a wall map. The map shows South America and Africa, with the east coast of South America and the southwest coast of Africa highlighted in red.]
:Miss Lenhart: People had long noticed that South America and Africa had similarly-shaped coastlines.

:[A side view of the classroom. Jill and Cueball are sitting at school desks, looking at Miss Lenhart. The wall map is visible behind Miss Lenhart.]
:Miss Lenhart: In the 20th century, geologists finally found the explanation:

:[The same scene, with Cueball having his hands on his face.]
:Cueball: ''Plagiaris''--
:Miss Lenhart: Continental drift.
:Cueball: Oh.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Miss Lenhart]]
[[Category:Comics featuring Jill]]
[[Category:Comics featuring Cueball]]
[[Category:Comics with color]]
[[Category:Geology]]
[[Category:Geography]]

Talk:3127: Where Babies Come From

2025-08-25T09:22:58Z

85.159.196.156:

First, I guess. [[User:B_for_brain|B for brain]] ([[User_talk:B_for_brain|talk]]) ([https://www.youtube.com/@bforbrain youtube channel] [https://bforbrain.weebly.com/ wobsite (supposed to be a blag)]) 21:41, 11 August 2025 (UTC)

The geology one seems to be more just an inference that a baby would emerge through differential erosion/weathering from the parent rock body. The meteorological one is both a near actual weather related event description and also a pun on what happens during conception. Other entries also vary between being puns on conception or birth (technically kind of true) or just wrong inferences using their field (such as the “off by one”) [[Special:Contributions/2A09:BAC2:39EE:240A:0:0:397:5A|2A09:BAC2:39EE:240A:0:0:397:5A]] 22:09, 11 August 2025 (UTC)pakers
:Yea I think the geology one reminds me of the reverse footsteps after snow (when you step in snow it compresses it which reduces melting compared to soft, noncompressed snow, meaning once the snow has melted the footsteps are now elevated) [[User:TheTrainsKid|TheTrainsKid]] ([[User talk:TheTrainsKid|talk]]) 22:18, 11 August 2025 (UTC)

0.001 kya (kilo years ago) is 0.001 x a thousand years ago (i.e. around a year ago) [[Special:Contributions/82.42.161.198|82.42.161.198]] 22:36, 11 August 2025 (UTC)

: .001kya is a one digit approximation for 9 months (technically .00075kya) [[User:MAP|MAP]] ([[User talk:MAP|talk]]) 01:59, 12 August 2025 (UTC)
::Actually, an approximation with precision of 1 year (= 1 a = 0.001 ka). A 5× more precise one-significant-figure approximation is 0.0008 kya (technically within actual variation, but further from the average than 0.00075). [[Special:Contributions/2001:4C4D:12CE:DA00:11BB:2E59:DD89:1F6A|2001:4C4D:12CE:DA00:11BB:2E59:DD89:1F6A]] 05:59, 12 August 2025 (UTC)

Why did Randall make this comic? My theory: he's gonna be a father soon and he's trying to figure out how to break the news to us. [[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 15:25, 12 August 2025 (UTC)
:[https://www.explainxkcd.com/wiki/index.php/2386:_Ten_Years This seems unlikely]. Unless they're adopting ...? [[Special:Contributions/205.175.118.102|205.175.118.102]] 16:57, 12 August 2025 (UTC)
::She had breast cancer. You feed babies with breasts you do not give birth to them using them, and can feed babies in other ways... So there is no problem getting kids after being treated for breast cancer. The question is if you wish to, given the risk of recurrence and early death. But Randall has made [[:Category:Comics with babies|lots of comics about babies]] so this comic is no different than those other, that did not indicate Randall about to have one. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 06:21, 13 August 2025 (UTC)

I think the article could be a bit more clinical and direct. Right now, it's low on information, and high on vauge implication, aiming for wit. I'll take a crack at improving some sections, but I'm not sure what the intentions were for every part.
[[Special:Contributions/62.92.112.171|62.92.112.171]] 18:39, 12 August 2025 (UTC)

Saying "contemporaneous documentation" suggests to me that the historians are seeking photographic or video evidence of the, erm, precipitating events. [[Special:Contributions/72.204.242.221|72.204.242.221]] 19:48, 12 August 2025 (UTC)

I guess [https://www.explainxkcd.com/wiki/index.php?title=3127:_Where_Babies_Come_From&oldid=384046 somebody] didn't get the deeper sense of humour. [[Special:Contributions/82.13.184.33|82.13.184.33]] 08:22, 13 August 2025 (UTC)

I understand the historian as questioning a (recently born) baby. After asking for more documentation the baby starts to cry which is interpreted as uncooperativeness. --[[Special:Contributions/2001:638:807:507:25AF:D335:DFE6:ACF4|2001:638:807:507:25AF:D335:DFE6:ACF4]] 08:32, 13 August 2025 (UTC)

Astronomer: at a Coldplay concert? {{unsigned ip|2401:d002:a203:dc00:801b:7795:5d8a:c0a|09:32, 14 August 2025}}
:Great! --[[Special:Contributions/85.159.196.156|85.159.196.156]] 09:22, 25 August 2025 (UTC)

GoComics now requires paid subscriptions, so the link to the Calvin and Hobbes comic should probably be changed to an image that doesn't have this restriction. [[Special:Contributions/2001:8003:1DC8:7900:ACDF:2A0D:1D9F:87F5|2001:8003:1DC8:7900:ACDF:2A0D:1D9F:87F5]] 03:15, 17 August 2025 (UTC)
:I don't have a subscription to GoComics, and the link works for me... on my desktop machine, at any rate. But not on my phone. I don't know where the difference lies. Perhaps the versions of Firefox and Chrome that Windows 8.1 supports aren't advanced enough to play with GoComics's demands. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 23:30, 17 August 2025 (UTC)
::What if we linked to this? https://web.archive.org/web/20241128040214/https://www.gocomics.com/calvinandhobbes/1987/04/18
::--[[Special:Contributions/85.159.196.156|85.159.196.156]] 09:22, 25 August 2025 (UTC)

"Built from a kit" is incorrect currently, but may be correct in future - if genetics and cloning techniques get more advanced, so people can configure DNA and RNA of their child as whatever they want. In most absurd cases, it could result in "future where everyone reproduce via cloning and genetic engineering, having multiple human sub-species optimized for different tasks - since due to genetic defects, reproductive organs of population became non-functional or non-existent, unusable for reproduction purposes - which doesn't stop our descendants from being massive perverts". --[[User:SMGmsgsgd|SMGmsgsgd]] ([[User talk:SMGmsgsgd|talk]]) 20:28, 24 August 2025 (UTC)