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		<updated>2026-04-15T10:16:03Z</updated>
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	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3143:_Question_Mark&amp;diff=387303</id>
		<title>3143: Question Mark</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3143:_Question_Mark&amp;diff=387303"/>
				<updated>2025-09-21T14:31:29Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3143&lt;br /&gt;
| date      = September 17, 2025&lt;br /&gt;
| title     = Question Mark&lt;br /&gt;
| image     = question_mark_2x.png&lt;br /&gt;
| imagesize = 380x463px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = Although now people will realize three-per-em space that all this time I've been using weird medium mathematical space whitespace characters in my hair space hair space hair space speech dot dot dot...&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|This page was created by a BOT TIRONIAN ET ⹒ MULTIPLE HUMANS PERIOD. Don apostrophe 't remove this notice too soon period.}}&lt;br /&gt;
&lt;br /&gt;
In colloquial English, the phrase &amp;quot;{{wiktionary|question_mark#Particle|question mark}}&amp;quot; is sometimes added to the end of a statement to give an exaggerated or emphasized impression of its uncertainty, as if the question mark in a written representation of the utterance should be spoken aloud instead of remaining implicit in the {{w|Intonation (linguistics)#English|rising intonation}}. This may be to reinforce true questions in dialects that exhibit a {{w|high rising terminal}} even for normal statements, to signal that a sentence is meant to be interrogative despite not following the typical structure of a question, or even just for effect. Here, the phrase “[it is] maybe even the greatest movie of all time” is structured like a standard declaration of fact, and so verbalizing the question mark helps clarify that the statement is made in order to request a (hoped for) confirmation, or at least acquiescence.&lt;br /&gt;
&lt;br /&gt;
This appears to be a relatively new phenomenon, at least in terms of gaining meaningful adoption, and such linguistic novelties can often cause irritation or discomfort among those outside of their usage groups. When [[Hairy]] does this, [[Cueball]] feels compelled to respond by doing the same with other punctuation marks, and even other matters of formatting, such as typographical emphasis and whitespace. Whether he does this to try to fit in, or as a form of 'revenge' for a perceived linguistic abuse is unclear.&lt;br /&gt;
&lt;br /&gt;
Generally, speaking punctuation and formatting out loud is considered strange, though there are some examples that are accepted, and it is possible that the same will become true of &amp;quot;question mark&amp;quot; over time. Sometimes the word &amp;quot;period&amp;quot; (US English) or &amp;quot;full-stop&amp;quot; (UK English) is spoken at the end of a sentence, before a period, to declare that there can be no dispute about what is being stated. An example might be: &amp;quot;That's the end of the matter, we're leaving Friday, period.&amp;quot; Similarly, a feeling of incompleteness or foreboding is sometimes evoked by speaking the phrase &amp;quot;dot dot dot&amp;quot; at the end of a sentence, reflecting the use of an ellipsis to indicate an unwritten continuation...&lt;br /&gt;
&lt;br /&gt;
Cueball mentions the film ''{{w|Charlie's Angels: Full Throttle}},'' illustrating the common use of italics to indicate titles of films (as well as other works, e.g. books, albums and series, depending on the stylebook used) and colons to separate subtitles from titles. From the context, Hairy and Cueball had differently polarised opinions about the merits of this film.&lt;br /&gt;
&lt;br /&gt;
The title text reads: &amp;quot;Although now people will realize three-per-em space that all this time I've been using weird medium mathematical space whitespace characters in my hair space hair space hair space speech dot dot dot...&amp;quot; Randall uses, and {{tvtropes|ReadingTheStageDirectionsOutLoud|vocalises}}, three different whitespace characters in this statement. Specifically, the three-per-em space (U+2004), the medium mathematical space (U+205F) and the hair space (U+200A). Normally they'd be used for typesetting mathematical formulae and in {{w|microtypography}}, without any expected audible distinction or meaning beyond text-placement and alignment in printed media.&lt;br /&gt;
&lt;br /&gt;
Translated, it looks like:&lt;br /&gt;
{| class=&amp;quot;wikitable&amp;quot;&lt;br /&gt;
|-&lt;br /&gt;
! Characters in title text&lt;br /&gt;
| &amp;quot;&amp;lt;span style='white-space: break-spaces;'&amp;gt;Although now people will realize&amp;lt;span style='background-color:#808080;'&amp;gt;&amp;amp;#x2004;&amp;lt;/span&amp;gt;that all this time I’ve been using weird&amp;lt;span style='background-color:#808080;'&amp;gt;&amp;amp;#x205f;&amp;lt;/span&amp;gt;whitespace characters in my&amp;lt;span style='background-color:#444;'&amp;gt;&amp;amp;#x200a;&amp;lt;/span&amp;gt;&amp;lt;span style='background-color:#aaa;'&amp;gt;&amp;amp;#x200a;&amp;lt;/span&amp;gt;&amp;lt;span style='background-color:#444;'&amp;gt;&amp;amp;#x200a;&amp;lt;/span&amp;gt;speech...&amp;lt;/span&amp;gt;&amp;quot;&lt;br /&gt;
|-&lt;br /&gt;
! Ordinary whitespace&lt;br /&gt;
| &amp;quot;&amp;lt;span style='white-space: break-spaces;'&amp;gt;Although now people will realize&amp;lt;span style='background-color:#808080;'&amp;gt; &amp;lt;/span&amp;gt;that all this time I’ve been using weird&amp;lt;span style='background-color:#808080;'&amp;gt; &amp;lt;/span&amp;gt;whitespace characters in my&amp;lt;span style='background-color:#808080;'&amp;gt; &amp;lt;/span&amp;gt;speech...&amp;lt;/span&amp;gt;&amp;quot;&lt;br /&gt;
|}&lt;br /&gt;
&lt;br /&gt;
Pronouncing punctuation used to be a staple of {{w|Dictation (exercise)|dictation}}, especially in the 20th century, when secretaries taking dictation to type letters were more commonplace. The expression &amp;quot;…, {{wiktionary|period#Interjection|period}}&amp;quot; or &amp;quot;…, {{wiktionary|full stop#Interjection|full stop}}&amp;quot;, taken to mean &amp;quot;…and that's final&amp;quot;, originates from this usage.{{acn}} Since Cueball is pronouncing all other punctuation marks as well, his final &amp;quot;period&amp;quot; denotes only the mark and not the common expression, especially since the latter would usually require mention of the comma before and then an ''additional'' spoken &amp;quot;period&amp;quot; after.&lt;br /&gt;
&lt;br /&gt;
The Kooblen, in Phil Foglio's &amp;lt;i&amp;gt;Buck Godot&amp;lt;/i&amp;gt; setting, [https://web.archive.org/web/20150428205448/http://www.airshipentertainment.com/buckcomic.php?date=20070125 speak in this way] to express punctuation.&lt;br /&gt;
&lt;br /&gt;
See (and hear) also Victor Borge's [https://www.youtube.com/watch?v=TIf3IfHCoiE &amp;quot;Phonetic Punctuation&amp;quot;] sketch in its various forms, in which a variety of vocal sounds are used to make punctuation explicit.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
:[Hairy and Cueball are both walking to the right.]&lt;br /&gt;
:Hairy: That movie was so good. Maybe even the greatest movie of all time question mark?&lt;br /&gt;
:Cueball: Yeah comma, but you said that about italics ''Charlie's Angels Colon: Full Throttle'' period. Paragraph break.&lt;br /&gt;
:Cueball: I question your judgment period.&lt;br /&gt;
:[Caption below the panel:]&lt;br /&gt;
:When people say &amp;quot;question mark&amp;quot; out loud as a rhetorical device, it always makes me want to say my other punctuation and formatting too.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&amp;lt;noinclude&amp;gt;&lt;br /&gt;
[[Category:Comics featuring Hairy]]&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Language]]&lt;br /&gt;
[[Category:Movies]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3105:_Interoperability&amp;diff=380230</id>
		<title>3105: Interoperability</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3105:_Interoperability&amp;diff=380230"/>
				<updated>2025-06-23T15:35:51Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */ added real-world issue&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3105&lt;br /&gt;
| date      = June 20, 2025&lt;br /&gt;
| title     = Interoperability&lt;br /&gt;
| image     = interoperability_2x.png&lt;br /&gt;
| imagesize = 740x269px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = We're getting a lot of complaints from commuters who were routed onto a coaster, but the theme park patrons who spent hours stuck on an intercity line are also not happy.&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
[[Black Hat]] gives a presentation to [[Cueball]] and [[Hairbun]] in which he emphasizes the importance of {{w|interoperability}} and compatibility. These terms refer to designing systems in such a way that systems can work together and share assets or components without modification. The terms are most commonly used in {{w|information technology}} to refer to different systems using the same formatting standards and communication protocols to allow the systems to interface and files to be exchanged easily. The terms also apply to hardware systems, where different pieces of equipment might use standardized parts and dimensions to allow them to be integrated easily. Railroads are a common example of this principle, if different railway systems are built to different gauges (the distance between the tracks), then rolling stock from one railway can't travel on another without major modifications. Building railroads to common specifications means that they can connect to one another, and can share, exchange and purchase equipment without compatibility issues. This is a real-world issue, for example mainland Europe switches from {{w|Iberian-gauge railways|Iberian gauge}} to {{w|Standard-gauge railway|standard gauge}} to {{w|5 ft and 1520 mm gauge railways|Russian gauge}} travelling from east to west, meaning that people and cargo have to change trains or the train must use a complex system to adjust its wheels when needing to move across the {{w|break of gauge}}.&lt;br /&gt;
&lt;br /&gt;
Black Hat points out that US rail systems predominantly use the standard gauge of 143.5cm (or the virtually identical 4 ft 8½ in, in the US), and associated {{w|Rapid transit|subway systems}} and their cars are built to match this standard. This is a good example of interoperable systems. However, he also points out that roller coasters typically use a different gauge, presenting this as a problem, then goes on to state that his company has been retrofitting roller coasters to match railway gauge, and speaks ominously about &amp;quot;Phase 2&amp;quot;. This suggests that he plans to either run railroad stock on roller coasters, or use roller coaster cars on train tracks. &lt;br /&gt;
&lt;br /&gt;
There are clearly many, many reasons why this would be a bad idea. Even with identical gauges, roller coasters would not be able to run on train tracks, or vice versa. The tracks, wheels and how they interface would still be completely different. Trains and subways using {{w|Train Wheel|sets of flanged steel wheels on top of the track}}, while coasters use {{w|Roller coaster wheel assembly|polyurethane rollers above, below, and to the sides of the track}}. Roller coasters are generally not powered, being initially lifted by a chain and then running on gravity and inertia. Roller coasters aren't built for the kind of weight or size typical to train cars. Any attempt to connect the two systems would almost certainly not work, and if attempted, would cause all kinds of damage and danger, while offering no obvious benefits. Given Black Hat's nature, it's unlikely that gives him any pause. &lt;br /&gt;
&lt;br /&gt;
The audience responds that &amp;quot;maybe interoperability is actually bad&amp;quot;. In fact, while interoperability can have major benefits in the right circumstances, there are many cases in which different systems should not be interfaced, and designing them to make such interfaces impossible is a good design principle. For example, electric systems that operate at different voltages might have differently designed plugs, to prevent accidentally plugging one into the other. In this case, even if it were possible to interface trains and roller coasters, it would be a terrible idea. &lt;br /&gt;
&lt;br /&gt;
The title text suggests that Black Hat's company has 'successfully' interfaced the two systems, allowing cars from each to travel onto the other (presumably meaning that they've solved the many, many engineering problems involved). Predictably, this has resulted in no benefits and major problems. Commuters on trains find themselves unexpectedly on roller coasters, which would be jarring, frightening, and dangerous (even if the track holds up and the train doesn't derail, lack of safety restraints would send people flying around the train cars). This is in addition to the simple fact that people trying to get to a destination largely wouldn't want to be routed onto an amusement park ride instead. By contrast, roller coaster patrons, expecting an exciting ride, would instead find themselves routed to ordinary transit lines, presumably going to destinations that they hadn't planned. Hence, even in the best case scenario, this connection would mess with everyone's plans, which is presumably Black Hat's central intention.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
{{incomplete transcript|Don't remove this notice too soon.}}&lt;br /&gt;
: [A close-up shot of Black Hat from the shoulders up]&lt;br /&gt;
: Black Hat: Compatibility and interoperability are so important.&lt;br /&gt;
&lt;br /&gt;
: [A zoom out reveals that Black Hat is standing in front of and pointing at a diagram showing a commuter subway car and a roller coaster car, and the tracks they both run on. Standing next to him are Cueball and Hairbun]&lt;br /&gt;
: Black Hat: For example, most subway rails are 143.5 cm apart. But many roller coasters use a narrower 110 cm gauge.&lt;br /&gt;
&lt;br /&gt;
: [This panel shows only Black Hat]&lt;br /&gt;
: Black Hat: For the last few years, our company has been quietly retrofitting roller coasters to use 143.5 cm tracks.&lt;br /&gt;
&lt;br /&gt;
: [Black Hat now has his fists raised]&lt;br /&gt;
: Black Hat: Soon, we can begin phase 2.&lt;br /&gt;
: Voice from off-panel: Maybe interoperability is actually bad.&lt;br /&gt;
: Black Hat: If you listen to the destination announcement while boarding, you'll be fine.&lt;br /&gt;
{{comic discussion}}&amp;lt;noinclude&amp;gt;&lt;br /&gt;
[[Category: Comics featuring Cueball]]&lt;br /&gt;
[[Category: Comics featuring Black Hat]]&lt;br /&gt;
[[Category: Comics featuring Hairbun]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3098:_Trojan_Horse&amp;diff=379193</id>
		<title>3098: Trojan Horse</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3098:_Trojan_Horse&amp;diff=379193"/>
				<updated>2025-06-11T13:31:25Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3098&lt;br /&gt;
| date      = June 4, 2025&lt;br /&gt;
| title     = Trojan Horse&lt;br /&gt;
| image     = trojan_horse_2x.png&lt;br /&gt;
| imagesize = 740x196px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = Ultimately, history would imperfectly record the story of the Foal of Troy.&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|This page was created by a BABY BOT INSIDE A BOT. Don't remove this notice too soon.}}&lt;br /&gt;
This comic presents a brief retelling of the {{w|Trojan Horse}} story, the climactic event of the legendary {{w|Trojan War}}, one of the best-known epics of ancient Greece and Rome. The retelling is a {{w|Feghoot|feghoot}}, set up to deliver the pun in the title text as well as a deconstruction of the story, replacing the epic elements with far more ordinary ones while keeping the tone of the tale the same.&lt;br /&gt;
&lt;br /&gt;
The premise is that the Trojan Horse story's origin is mundane. The gift to the Trojans by the (supposedly) departing Greek army, we are told, was a normal-sized, living mare, which promptly and unexpectedly dropped (i.e. gave birth to) a foal. According to the title text, this is the story of the &amp;quot;Foal of Troy&amp;quot;, which &amp;quot;history imperfectly recorded&amp;quot;.  In the &amp;quot;imperfect record&amp;quot; (presumably the one by {{w|Virgil}}), the normal-sized live horse became a colossal wooden statue that &amp;quot;dropped&amp;quot; a commando unit of some 40 Greek soldiers, who opened the gates of Troy to the main Greek force (who had sailed back under the cover of darkness), resulting in the &amp;quot;''Fall'' of Troy&amp;quot;. The pun is implicit, as &amp;quot;Fall of Troy&amp;quot; does not appear in the comic. ‘Fall’ (πτῶσις) and ‘foal’ (πῶλος) share the initial consonant and stem vowel in Ancient Greek and are spelled even more similarly in English as well as being near {{w|homophone}}s. &lt;br /&gt;
&lt;br /&gt;
It is not made clear whether the gifter of the horse knew of/suspected the pregnancy or whether they would have even chosen to hand it over under different circumstances. However, it is consistent with the story, and with the {{w|Beware_of_Greeks_bearing_gifts|&amp;quot;Greeks bearing gifts&amp;quot; trope}} that originated with it, that the Greeks intentionally gifted a pregnant mare to annoy the Trojans. Surprise foals, where a mare is purchased with a hitherto unknown pregnancy, actually occur. The pregnancy is typically excused as weight gain, up until the point where a foal is discovered with its mother in the morning. Horses with rounder builds, like some pony breeds, are known for maintaining undetected pregnancies. The reason a surprise foal might be salient for the comic, beyond the &amp;quot;Foal of Troy&amp;quot; pun, is the non-trivial costs of horse ownership, which can amount to hundreds or thousands of dollars per month. Food costs are part of (but not all of) this, as the comic touches on.&lt;br /&gt;
&lt;br /&gt;
The joke suffers from a modern bias in that in present day North America horses are seen largely as companion animals that can cost a great deal of one's discretionary income (or grain supply) to maintain. However in ancient times, horses were valuable tools and the gift of a pregnant mare would generally be welcomed. In the uncommon situation where the local food supply was insufficient to maintain one or both of the creatures, they could be slaughtered for their meat, a practice that in Munroe's time has become taboo.&lt;br /&gt;
&lt;br /&gt;
Archaeological evidence of a military conquest of {{w|Troy}} during the Bronze Age, or even of a major war centered on the city, is lacking. Far better evidence exists for the destruction of several iterations of the city by earthquakes. It is not thought that these earthquakes were caused by horses{{Citation needed}}. Possibly, the Trojan War legend arose as visitors attempted to explain the ruins of an earthquake-ravaged, deserted city. The &amp;quot;Foal of Troy&amp;quot; story, therefore, need not include a Greek conquest of Troy, or even a major military conflict with the Greeks.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
{{incomplete transcript|Don't remove this notice too soon.}}&lt;br /&gt;
:[A horse is facing Cueball and Ponytail, who are standing in front of an entrance below a tower.]&lt;br /&gt;
:[In an inset panel, Cueball is talking to Megan and Hairy.]&lt;br /&gt;
:Cueball: When the Greeks departed, they left behind a horse as a gift.&lt;br /&gt;
&lt;br /&gt;
:[Hairbun is standing behind a horse, with Cueball standing in front.]&lt;br /&gt;
:We took it as a gesture of peace, but it carried a secret payload.&lt;br /&gt;
&lt;br /&gt;
:[A smaller horse is standing behind the horse from previous panel, which is looking behind at it.]&lt;br /&gt;
:One night, from within the horse, '''''another, smaller horse emerged!'''''&lt;br /&gt;
&lt;br /&gt;
:[Close-up on Cueball.]&lt;br /&gt;
:Cueball: Our guards have been unable to determine the inner horse's objective, but it has begun to show an interest in our oats.&lt;br /&gt;
:Off-panel voice 1: An attack on Troy's food supply!&lt;br /&gt;
:Off-panel voice 2: How ''dare'' they!?&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&amp;lt;noinclude&amp;gt;&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics featuring Megan]]&lt;br /&gt;
[[Category:Comics featuring Hairy]]&lt;br /&gt;
[[Category:Comics featuring Ponytail]]&lt;br /&gt;
[[Category:Comics featuring Hairbun]]&lt;br /&gt;
[[Category:Animals]]&lt;br /&gt;
[[Category:Food]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3046:_Stromatolites&amp;diff=364586</id>
		<title>3046: Stromatolites</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3046:_Stromatolites&amp;diff=364586"/>
				<updated>2025-02-05T15:39:17Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3046&lt;br /&gt;
| date      = February 3, 2025&lt;br /&gt;
| title     = Stromatolites&lt;br /&gt;
| image     = stromatolites_2x.png&lt;br /&gt;
| imagesize = 581x505px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = If only my ancestors had been fortunate enough to marry into the branch of the bacteria family that could photosynthesize, like all my little green cousins here.&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|Created by THE MISSING LINK'S OSTRACIZED ANCESTOR - Please change this comment when editing this page. Do NOT delete this tag too soon.}}&lt;br /&gt;
This comic makes fun of claims to 'special' ancestry, such as some old royal family or similar, that may be made after doing research on a {{w|family tree}} site. These services allow the user to input the names and other information of family members and cross reference with various documents to trace lines of descent. Often, those who find a connection to a historically significant individual are quite excited about this, and may feel that it somehow makes them special. However, in reality, once you go back more than a few generations there will be many thousands of such connections, and once you get back more than a thousand years or so, anyone you could be related to will also be related to pretty much everybody else still alive in some way or other.&lt;br /&gt;
&lt;br /&gt;
While out for a walk, [[Beret Guy]] is explaining to [[Cueball]] how he has been on such a site and kept clicking back until he found an ancestor from &amp;quot;a few billion years back&amp;quot;. These services typically do not allow the user to track their familial history prior to written records{{citation needed}}, but with his [[:Category:Strange powers of Beret Guy|strange powers]] it is no wonder that Beret Guy could make this work! (Some do provide genetic sequencing, which allows for more information to be acquired, but this isn't accurate enough to track individual people who lived before such technology existed on a wide scale.)&lt;br /&gt;
&lt;br /&gt;
He may also have needed to rely on these powers to do all the clicks needed to go back that far in the past. Even at a rate of 10 to 15 clicks per second it would still take thousands of years — maybe even more due to how fast cells can reproduce — to do enough clicks to work back this far from scratch. However, it may be that a large part of the tree had already been constructed by previous users, and all he had to do was find a relation already attached to this tree. This would further underline how un-special his newly discovered relationship is.&lt;br /&gt;
&lt;br /&gt;
Beret Guy found out that he is related to {{w|stromatolites}}. They are layered sedimentary formations created by microorganisms, predominantly the oxygenic-photosynthetic {{w|Cyanobacteria|cyanobacteria}}. The organisms produce adhesive compounds that cement sand and other rocky materials to form mineral &amp;quot;microbial mats&amp;quot; (Cueball calls them ''bacterial mats''). A succession of these mats through time forms the layers (&amp;quot;stromata&amp;quot;) characteristic of both fossil and modern stromatolites. Some fossil stromatolites in Australia from 3.48 billion years ago contain the oldest undisputed evidence of life on Earth, though people have also claimed {{w|Earliest known life forms|other, older evidence}} for this record. Since this is some of the first life on Earth it is basically a given that all life that came after (not even just all humans) is related. Beret Guy only claims he is related to their {{w|Alphaproteobacteria|cousins}} and that it is from their cousin bacteria that he got his {{w|mitochondria}}. His aside that he also got his cell nuclei in this way is odd, as, according to the {{w|Cell_nucleus#Evolution|leading contemporary theory}}, the ancestral archaeon (&amp;quot;my archaean ancestors&amp;quot;) themselves contributed the nucleus to the original eukaryotic cell. In this model, both the archaeon and the alpha-proteobacterium were endosymbionts in a third cell, which is not consistent with Beret Guy's claim that the mitochondrion began as an archaeon's endosymbiont. Perhaps all that clicking addled even Beret Guy's brain. Anyway, he is not claiming to be a direct descendant from [the cyanobacterial component of] stromatolites, which makes sense since they can photosynthesize, and as he mentions in the title text, he cannot!&lt;br /&gt;
&lt;br /&gt;
Cueball asks if he would like to contact his distant relatives, since there are still living stromatolites today (or at least something very similar to those from billions of years ago). But Beret Guy imagines they are busy so he will not bother them. When asked by Cueball what he would use his newfound knowledge for, he lies down on the hill they have climbed to bask in the sun. Because as he says, &amp;quot;Lying on a hill in the warm sun is an old family tradition.&amp;quot; This is basically the only thing stromatolites can do, but they are doing it all the time and could thus be said to be busy with this. It seems, however, like Beret Guy is going to enjoy this tradition.&lt;br /&gt;
&lt;br /&gt;
In the title text Beret Guy muses about how great it would have been if his distant relatives had married into the branch of the bacteria family that could photosynthesize... and then refers to the grass he is now lying on as &amp;quot;my little green cousins here&amp;quot;. If this had happened he would either have been able to lie on the hill without eating since [https://www.gocomics.com/doonesbury/2014/10/28 he would be able to photosynthesize] getting energy directly from the sun (instead of eating some of his small green cousins' closer relatives) - although that might not be enough to sustain him, as per ''[[what if? (blog)|what if?]]'' article ''{{what if|17|Green cow}}''. Or else he would actually have been a plant instead.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[Cueball and Beret Guy, seen from afar in silhouette, are walking up a grassy hill.]&lt;br /&gt;
&lt;br /&gt;
:[They continue walking up the hill, reaching its grassy summit. Now with normal lighting. Beret Guy is a bit ahead of Cueball.]&lt;br /&gt;
:Beret Guy: I learned something today.&lt;br /&gt;
:Beret Guy: I went on one of those family tree sites and kept clicking back, and it turns out I'm related to stromatolites!&lt;br /&gt;
&lt;br /&gt;
:[Closeup on Cueball. Beret Guy's reply comes off-panel from a starburst on the right edge of the panel.]&lt;br /&gt;
:Cueball: The bacterial mats?&lt;br /&gt;
:Beret Guy [off-panel]: Yeah! A few billion years back, on my mitochondria's side.&lt;br /&gt;
&lt;br /&gt;
:[Cueball and Beret Guy standing on the top of the grassy hill facing each other. Beret Guy holding a hand out towards Cueball.]&lt;br /&gt;
:Beret Guy: My Archaean ancestors absorbed some bacteria that were cousins of stromatolites. That's how I got mitochondria.&lt;br /&gt;
:Beret Guy: Cell nuclei, too.&lt;br /&gt;
&lt;br /&gt;
:[Cueball is standing behind Beret Guy who is now sitting down in the grass leaning back on one arm with the other arm resting on his bent knee.]&lt;br /&gt;
:Cueball: I think there are still living stromatolites. You could get in touch.&lt;br /&gt;
:Beret Guy: Nah, they're probably busy. I don't want to bother them.&lt;br /&gt;
&lt;br /&gt;
:[Cueball is sitting behind Beret Guy who is now lying down, both again shown in silhouette from a far, revealing they are on the top of the grassy hill.]&lt;br /&gt;
:Cueball: So what ''are'' you going to do with this knowledge? Nothing?&lt;br /&gt;
:Beret Guy: Lying on a hill in the warm sun is an old family tradition.&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Comics featuring Beret Guy]]&lt;br /&gt;
[[Category:Biology]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3038:_Uncanceled_Units&amp;diff=362159</id>
		<title>3038: Uncanceled Units</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3038:_Uncanceled_Units&amp;diff=362159"/>
				<updated>2025-01-15T14:48:44Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3038&lt;br /&gt;
| date      = January 15, 2025&lt;br /&gt;
| title     = Uncanceled Units&lt;br /&gt;
| image     = uncanceled_units_2x.png&lt;br /&gt;
| imagesize = 323x355px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = Speed limit c arcminutes^2 per steradian&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|Created by THE PLANCK CONSTANT, WHICH IS TECHNICALLY A FREQUENCY AND CAN THUS BE EXPRESSED IN HERTZ - Please continue to explain the joke and possible interpretations. Do NOT delete this tag too soon.}}&lt;br /&gt;
Another of [[Randall]]'s [[:Category:Pet Peeves|pet peeves]], this comic expresses disapproval of units that could be mathematically simplified.&lt;br /&gt;
&lt;br /&gt;
In this comic, [[White Hat]] is presenting a refrigerator to [[Cueball]], claiming it only uses 3 kWh per day. This is a commonly used, but uncancelled unit: kiloWatts x hour / day contains two units of time, which can be cancelled (24h = 1d), yielding 1/8 kW or 125 W. White Hat is expressing the refrigerator's power consumption as a unit of energy divided by time, but his choice of energy unit, kilowatt hour, is itself a unit of power times time (as opposed to the standard unit for energy, the Joule). Whilst this way of expressing energy consumption may be jarring to a scientific purist, it may well be preferred by an ordinary consumer as electricity is generally priced in kWh, allowing an easy conversion into currency to understand how much the refrigerator will cost to run each day.&lt;br /&gt;
&lt;br /&gt;
Cueball (possibly representing Randall) answers by asking whether the refrigerator would fit in his kitchen, since the ceiling is only 50 gallons per square foot high, which is also an uncancelled unit, as gallons can be transformed to cubic feet (1 US gal ≈ 0.1337 ft&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;), which can be divided by the square feet, yielding a ceiling height of around 203.7 cm, or around 6 feet 8 inches. (Using imperial gallons [1 UK gal ≈ 0.1605 ft&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;], the height is approximately 244.7 cm, roughly 8 feet.) Cueball's unit is much less common and was likely deliberately chosen to be harder to understand, which shows how Randall feels about people using other uncancelled units like &amp;quot;kWh per day&amp;quot;.&lt;br /&gt;
&lt;br /&gt;
''[[what if? (blog)|what if?]]'': [https://what-if.xkcd.com/11/ Droppings] also covers strange instances of unit cancellation, including a measure of volume per distance converted to area; similar to Cueball's measure of volume per area representing a distance (the height of his ceiling).&amp;lt;!-- This may not be relevant enough to keep --&amp;gt;&lt;br /&gt;
&lt;br /&gt;
In the title text, a speed limit is given as c arcminutes^2 per steradian, where c is presumably the speed of light in vacuum, 2.998×10^8 m/s (meters per second) or 186282 mi/s (miles per second). A steradian (sr) is the SI unit for solid angle, subtending a section of a sphere, like a radian is a unit of angle subtending a section of a circle. A square arcminute is also a unit of solid angle, equivalent to a section of a sphere of 1/60 of a degree by 1/60 of a degree. There are ((1/60)*(pi/180))^2 = 8.462×10^-8 sr in a square arcminute. Then multiplying by c gives a speed of 56.75 mph (probably 55 mph, based upon the {{w|National Maximum Speed Law|'traditional' US speed limit}}, before rounding errors in the reverse direction), or 91.33 km/h, showing that you can combine an outrageously high speed with two unnecessary units that cancel each other to form a normal road speed.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
{{incomplete transcript|Do NOT delete this tag too soon.}}&lt;br /&gt;
&lt;br /&gt;
:[White Hat and Cueball are standing to either side of a refrigerator. The fridge has two top compartments and one bottom compartment. The top left compartment has a tall handle on its right, the top right compartment has a tall handle on its left, and the bottom compartment has a long handle on its top. The top left compartment has a paper attached to it with unreadable text, possibly an advertisement.]&lt;br /&gt;
:White Hat: This fridge uses only 3 kWh per day!&lt;br /&gt;
:Cueball: But will it fit in my kitchen? The ceiling there is only 50 gallons per square foot.&lt;br /&gt;
&lt;br /&gt;
:[Caption below the panel:]&lt;br /&gt;
:Pet peeve: Uncanceled units&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
&lt;br /&gt;
[[Category:Comics featuring White Hat]]&lt;br /&gt;
[[Category:Comics featuring Cueball]]&lt;br /&gt;
[[Category:Math]]&lt;br /&gt;
[[Category:Pet Peeves]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=3038:_Uncanceled_Units&amp;diff=362133</id>
		<title>3038: Uncanceled Units</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=3038:_Uncanceled_Units&amp;diff=362133"/>
				<updated>2025-01-15T13:35:50Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */ corrected hat character colour&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 3038&lt;br /&gt;
| date      = January 15, 2025&lt;br /&gt;
| title     = Uncanceled Units&lt;br /&gt;
| image     = uncanceled_units_2x.png&lt;br /&gt;
| imagesize = 323x355px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = Speed limit c arcminutes^2 per steradian&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|Created by 1440 BOT-MINUTES PER DAY - Please change this comment when editing this page. Do NOT delete this tag too soon.}}&lt;br /&gt;
In this comic, [[White Hat]] is presenting a refridgerator to [[Cueball]], claiming it only uses 3 kWh per day. This is a commonly used, but uncancelled unit: kiloWatts x hour / day contains two units of time, which can be cancelled (24h = 1d), yielding 0.125 or 1/8 kW.&lt;br /&gt;
Cueball answers by asking whether the refridgerator would fit in his kitchen, since the ceiling is only 50 gallons per square foot high, which is also an uncancelled unit, as gallons can be transformed to cubic feet, which can be divided by the square feet, yielding a ceiling height of around 203.7 cm, or around 6 feet 8 inches.&lt;br /&gt;
&lt;br /&gt;
White Hat is trying to sell a refrigerator to Cueball. In doing so, he touts the power draw of the unit as &amp;quot;three kilowatt-hours per day&amp;quot;. But &amp;quot;day&amp;quot; and &amp;quot;hours&amp;quot; are both units of time. &amp;quot;Per&amp;quot; indicates division, so this could be written as (3 kW-h / d), or (3 kW-h / 24 h). Identical units in the numerator and denominator of a fraction cancel out, so it could also be written as (1/8 kW), or one-eighth of a kilowatt (or 175 watts), a typical power draw for a fridge running between 6 and 8 hours a day.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
{{incomplete transcript|Do NOT delete this tag too soon.}}&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	<entry>
		<id>https://www.explainxkcd.com/wiki/index.php?title=2747:_Presents_for_Biologists&amp;diff=308536</id>
		<title>2747: Presents for Biologists</title>
		<link rel="alternate" type="text/html" href="https://www.explainxkcd.com/wiki/index.php?title=2747:_Presents_for_Biologists&amp;diff=308536"/>
				<updated>2023-03-14T15:10:19Z</updated>
		
		<summary type="html">&lt;p&gt;Jellyfish dave: /* Explanation */ link to the other James Bond&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;{{comic&lt;br /&gt;
| number    = 2747&lt;br /&gt;
| date      = March 8, 2023&lt;br /&gt;
| title     = Presents for Biologists&lt;br /&gt;
| image     = presents_for_biologists_2x.png&lt;br /&gt;
| imagesize = 396x353px&lt;br /&gt;
| noexpand  = true&lt;br /&gt;
| titletext = A lot of these are actually non-venomous, but I can see which species you mistook them for. If you pause the crane for a sec I can give you some ID pointers for next time!&lt;br /&gt;
}}&lt;br /&gt;
&lt;br /&gt;
==Explanation==&lt;br /&gt;
{{incomplete|Created by a SUPERVILLAIN - Please change this comment when editing this page. Do NOT delete this tag too soon.}}&lt;br /&gt;
&lt;br /&gt;
In this strip, [[Black Hat]] is a supervillain subjecting '{{w|James Bond}}' (drawn as [[Hairy]]) to a death trap, similar to [[123: Centrifugal Force]] (presumably Bond managed to escape in that instance). &lt;br /&gt;
&lt;br /&gt;
This time, however, Black Hat also has another victim, [[Science Girl]], apparently playing the role of a {{w|Bond Girl}} (who were sometimes scientists in the stories) being subjected to the same device – a pit full of snakes, into which the victims are slowly lowered (upside-down and suspended by just one ankle) entirely at the whim or mercy of the antagonist.&lt;br /&gt;
&lt;br /&gt;
While Bond voices typical defiance at Black Hat's scheme, Science Girl instead gushes over the sight of an unfamiliar snake species within the pit, asking Black Hat to lower her faster before that creature either escapes (there seemingly being very little to prevent any snake escaping the pit) or just moves to the other end of the pit.&lt;br /&gt;
&lt;br /&gt;
The caption reveals that Science Girl is a biologist. For her, the contents of this death trap would be happily considered a suitable present or experience gift, and apparently even the dire circumstances don't dampen the experience sufficiently to reduce her interest. &lt;br /&gt;
&lt;br /&gt;
The caption also mentions that there is a surprising amount of overlap between what would be &amp;quot;good presents for biologists&amp;quot; (like the ornithologist, {{w|James_Bond_(ornithologist)|James Bond}}?) and &amp;quot;things villains want to do to James Bond&amp;quot;. Although we can only guess what other activities [[Randall]] is thinking of, shark tanks could be one of them, or maybe the crabs in Dr. No, which turned out not to be carnivorous and which Honey found &amp;quot;good company&amp;quot;.&lt;br /&gt;
&lt;br /&gt;
The title text explains how Science Girl has expertly spotted that the supervillain included some less dangerous snakes, probably {{w|Coral snake#North American coloration patterns|in error}}. Ever the professional, she suggests the possibility of her advice to help him avoid these errors in the future and increase the deadliness of his scheme. She would need a short stay of execution to do so, but is apparently not particularly fazed by how things end up immediately afterwards.&lt;br /&gt;
&lt;br /&gt;
==Transcript==&lt;br /&gt;
:[James Bond, drawn as Hairy, and Science Girl are hanging upside down from ropes attached to one of their ankles. Underneath them is a pit with many snakes. Science Girl is pointing down, while Black Hat to the left is operating a lever. Bond is yelling at Black Hat, indicated by lines emanating from his head. Science Girl is also yelling, but that is in the direction of the snakes beneath them. There seems to be many snakes in the pit, at least eight heads can be seen, and there are also snakes whose heads are not visible. At least six snakes are partly outside the pit. They have different patters of spots and shades and stripes.]&lt;br /&gt;
:Bond: You won't get away with this!&lt;br /&gt;
:Science Girl: Ooh! Ooh! That one is a new species for me!&lt;br /&gt;
:Science Girl: Hey, can you lower me faster? It's getting away!&lt;br /&gt;
&lt;br /&gt;
:[Caption below the panel:]&lt;br /&gt;
:There's a surprising amount of overlap between &amp;quot;Good presents for biologists&amp;quot; and &amp;quot;Things villains want to do to James Bond.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
{{comic discussion}}&lt;br /&gt;
&lt;br /&gt;
[[Category:Comics featuring Black Hat]]&lt;br /&gt;
[[Category:Comics featuring Hairy]]&lt;br /&gt;
[[Category:Comics featuring Science Girl]]&lt;br /&gt;
[[Category:Biology]]&lt;br /&gt;
[[Category:Animals]]&lt;br /&gt;
[[Category:Fiction]]&lt;/div&gt;</summary>
		<author><name>Jellyfish dave</name></author>	</entry>

	</feed>