explain xkcd - User contributions [en]

2456: Types of Scientific Paper

2026-04-14T18:20:33Z

Xkcd explainer: grammer fixed in image description of article nr. 10

{{comic
| number = 2456
| date = April 28, 2021
| title = Types of Scientific Paper
| image = types_of_scientific_paper.png
| titletext = Others include "We've incrementally improved the estimate of this coefficient," "Maybe all these categories are wrong," and "We found a way to make student volunteers worse at tasks."
}}

==Explanation==
In this comic, Randall satirizes scientific papers by claiming they all (or at least the large majority) fall into only a small number of categories, which he describes with somewhat humorous generalized titles. This comic may be a jab at mainstream news and their handling of scientific announcements; journalists are eager to report on what could turn out to be a scientific breakthrough even if it's very similar to stories they've already published about similar papers that turned out to be somewhat mundane. It may also relate to how some scientific findings follow certain patterns.

==Breakdown of papers==
{| class="wikitable"
|-
!Paper Title
!Explanation
!Visual Description
|-
!scope=row|We put a camera somewhere new
|This may involve miniaturisation or other improvements of imaging sensors, power supply, transmission or retention of data, environmental hardening and (possibly) recovery afterwards. Photographs and videos can be especially helpful in understanding what is or was going on, especially for the layman, than more limited signal traces.

Cameras have been inserted into every obvious bodily orifice (including swallowed, to be later excreted), placed in habitats to monitor wildlife, attached to wildlife to monitor habitats, sent into volcanic craters/ocean trenches/high altitudes/nuclear reactors, launched into space and sent past/round/onto several of the solar-system's more interesting bodies. This makes the "somewhere new" claim intriguing, possibly even comparable to 'clickbait'.

This could also be generalized even more by replacing "camera" with "sensor", and then going to debate the newly derived sensor data.
|Includes a large figure, likely an image captured with the camera.
|-
!scope=row|Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!
|Rather than starting with the aim of investigating some question, and finding some way of answering it by uncovering evidence, sometimes a writer may have stumbled upon a cache of historic documents that they then feel compelled to justify the resulting '{{w|Wiki rabbit hole|Wiki Walk}}' they may have found themselves sucked into. The author may be far more excited about this than any future reader. This could also be a paper by a historian who found out ancient records which could be useful. A similar sentiment appears in [[1979: History]].
|Small figure may show the most interesting fragment of the records.
|-
!scope=row|My colleague is wrong and I can finally prove it
|This title refers to the occasional rivalries between scientists within a field, which can push them to seek proof that they, and not their colleague, are correct. This search for vindication, rather than truth, can lead the researcher to overlook significant flaws in their research, and can also make for tedious reading. It reflects a tone of smug self-satisfaction.
|Like the two previous types, this one is laid out in two-column format with occasional section headings. Unlike those types, it has no figures.
|-
!scope=row|The immune system is at it again
|The human immune system is notoriously complex, and there are countless papers in medical fields just describing its strangeness. While it is best known for preventing and battling infections, it can also overreact or even turn against the body that it is supposed to protect. For instance, it can overreact in allergic reactions or in a potentially lethal {{w|cytokine storm}} known to occur in certain viral infections, including {{w|influenza}} and {{w|COVID-19}}. The title may convey exasperation with the amorphous nature of this study subject.
|Two-column format, no figures.
|-
!scope=row|We figured out how to make this exotic material, so email us if you need some
|Researchers often attempt to create materials despite there not being any demand, predicting that in the future their material will be game-changing without any actual applications. These researchers have created such a material, and are offering to produce it for anyone who needs it. It is couched in terms of having created an answer for which there was not yet any proper question.

Sometimes the only reason for trying to create the materials is that they are peculiar or novel in some way, with no consideration of whether they might have any use apart from demonstrating the novel property. However, some other people might find that property very useful... and may lack the ability to make the substance for themselves.

This may be also referring to the discovering/creating of elements and subatomic particles. The statement if you wish to buy it is humorous in these cases because they will decay too quickly to be purchased.
|Two-column format, no figures.
|-
!scope=row|What are fish even doing down there
|Deep sea marine biology regularly discovers [https://www.youtube.com/watch?v=u7QXdlSBGGY strange lifeforms] in [https://www.9news.com.au/world/sharks-living-in-volcano-why-are-marine-predators-living-in-an-active-crater/db112bd9-21b2-46c2-9d58-ed07f981ae01 unexpected places], and theories explaining deep sea ecosystems are regularly confounded by new data.

Scientists may also bump into marine organisms when looking for something else. For example, one planned underwater neutrino detector [https://www.nature.com/articles/srep44938 picked up bioluminescence instead].

Whichever way, the title probably reflects a totally unexpected result that is possibly too cross-disciplinary to be properly comprehended as an actual scientific advance by the authors. However, a proper study of the species could very well be an important paper.
|This one-column paper does not appear to have any headers, implying a longer, free-flowing format.
|-
!scope=row|This task I had to do anyway turned out to be hard enough for its own paper
|There is a huge variety in the complexity and importance of subjects studied in scientific papers, and often some supposedly easy task will be sufficiently complicated as to merit its own paper. For example, as part of a {{w|materials science}} project (perhaps making the aforementioned exotic material), a scientist may have innovated on a chemical process involved in its production. Such an innovation could well be worth publishing in its own right, and might even turn out to be of more general application than the "main" project.

The author may be glad to have been able to turn mundane 'housekeeping' activities, that don't normally do much to enhance academic reputations, into an actual opportunity to be cite-worthy.
|This paper is also one-column but it contains section headers.
|-
!scope=row|Hey, at least we showed that this method can produce results! That's not nothing, right?
|One of the struggles of the scientific method is that many experiments will not produce the results scientists desired or expected. Negative or conflicting results of well-conducted research are as important as positive or dramatic ones, but are often ignored in favor of more novel findings. As a result, some journals are established specifically for negative results, reducing the bias towards only positive claims that may actually be outliers or anomalies.

In this case, the authors may otherwise have worked on their problem and been left with no citable proof of their efforts. The title perhaps reflects an attempt to present this as 'success' of a different kind, rather than a submission to such a null/negative-results platform. This may be similar to the above type of paper too.
|Two-column format, no figures.
|-
!scope=row|Check out this weird thing one of us saw while out for a walk
|This paper may be imagined as an opportunistic publication. A department or team has seen itself low down on the local 'league table' for academic output. A brainstorming session for a way of rectifying this led to desperately seizing upon the first idle comment made (in lieu of any better sounding ideas) that can somehow be shoehorned into their respective subject area, and is now being presented similar to "this one weird thing" clickbait titles that almost always oversell their content.
This also works in the context of entomology. Insects have the most species of any class of animals [https://www.si.edu/spotlight/buginfo/bugnos by a wide margin], but due to their small size, they're not easily seen. As a result, new species are constantly being discovered in places as innocuous as [https://wildlife.org/video-entomologists-discover-30-new-species-in-la-backyards/ someone's backyard].

It also works in botany, especially floristics. Papers of first records of alien plants refer to weird things botanists saw on walks. Vagrant birds, unusual animal behaviour, and strange meteorological phenomena are other subcategories.
|Two-column layout. Includes several large figures, likely close-up photographs of the weird thing. There are no headers, as the paper may have little background or methodology, just observations.
|-
!scope=row|We are 500 scientists and here's what we've been up to for the last 10 years
|Some papers summarize the work of big research teams, like those working on the [https://repositorio.uc.cl/xmlui/bitstream/handle/11534/13948/Observation%20of%20a%20new%20particle%20in%20the%20search%20for%20the%20Standard%20Model%20Higgs%20boson%20with%20the%20ATLAS%20detector%20at%20the%20LHC.pdf Higgs Boson] (list of authors starts at page 17 and goes to page 26 with foot notes about authors to page 29, and a dedication in the header would suggest that more than one other contributor died over the course of the research, which would be rather unusual for a smaller project) or LIGO. Since the discoveries which are made are a team effort, probably outlasting many of the individual tenures involved, the papers have many authors listed.
A credit for participation may not mean any particularly great contribution by each individual, but being left out (even for one summer's secondment, seven years before any results could be recorded) would be taken as a slight, and an opportunity missed to be 'citable' in the future.
|A huge portion of the page is taken up by - presumably - the 500 authors' names, above the main horizontal bar.
|-
!scope=row|Some thoughts on how everyone else is bad at research
|Similar to the "my colleague is wrong" paper, but in this case applied to far greater swathes of the community by the author(s) of this (possibly unfocused) tract. Usually a "systematic review", the words 'some thoughts' might indicate a meta-approach with no original research - and possibly a passive-aggressive style of assessment.
|No header sections, possibly because these particular thoughts are in the form of an essay or letter without an accompanying investigation. Formatting this article as a single column with large blocks of text could also be indicating a slightly unhinged rant by someone who—wrongly—perceives themselves as unjustly marginalized.
|-
!scope=row|We scanned some undergraduates
|Initial research is often done at universities, so when human subjects are required, recruiting undergraduate students is a common, easy, and inexpensive way to gather enough people to conduct studies or experiments. This is extremely common in psychological or sociological studies, but can involve more medical (but non-invasive) 'scans', from simple eyeball-tracking to full-body MRI. This practice is often criticized, as it introduces a selection bias, which makes the results difficult to generalize to the entire population, as university students in a given country are not necessarily a representative sample of human beings as a whole. Nonetheless, easy accessibility makes these students a source of data for many academic papers. The low-key approach to the title (concentrating blandly upon the method with no references to results) may indicate that the results obtained are very trivial and no great developments were even made in implementation. Alternately, this is a truly ground-breaking paper obscured entirely by the lead author's over-narrow professional focus and avoidance of any hype.
|Two-column format with figures.
|-
!scope=row|We've incrementally improved the estimate of this coefficient
|Often scientific research, e.g. in cosmology or physics, will work with an assumed constant value that is known to be only an 'educated guess' of the actual definite value, or an inclusive range. However accurate/certain this is, further experimentation or observation may further narrow down the uncertainty involved to a statistically significant degree. An improvement to one of these constants also improves the accuracy of every single calculation that uses it.

Even if these improvements may seem trivial to those outside the discipline (e.g. narrowing down a seemingly esoteric value from 99.99% certainty to 99.995% certainty), they are probably understood as significant achievements by those aware of the effort needed to obtain such diminishing returns, and the authors are probably very excited to have done what they did.

Another possible interpretation of this title is that it refers not to cosmological constants but to an exponent in algorithmic complexity, for example the [https://arxiv.org/abs/1401.7714 2014 paper] that proved that the complexity of matrix multiplication is at most n^2.3728639 in place of the previous upper bound n^2.3729.
|rowspan="3"|(Only referenced in Title Text)
|-
!scope=row|Maybe all these categories are wrong
|In some field that relies heavily upon classification (e.g. phylogenetic biology, or the Standard Model in physics) sometimes observations arise that cast doubt on the previously established ideas. It seems that this may have happened here, hopefully with a suggestion of how to reimagine the situation.

The article may have been written with a sense of euphoria (the chance to present a paradigm shift in thinking, to rewrite the textbooks) or pessimism (it demonstrates only the failings in current thinking, without any obvious solution).

Alternatively, it may be a reference to the categories of papers that this comic proposes.
|-
!scope=row|We found a way to make student volunteers worse at tasks
|Possibly a psychology experiment, and maybe not even the result expected. In general, the repetition of an activity will induce greater skill/capacity in a tested individual. By accident or design, the study group in this instance has induced the opposite correlation. (There are, however, some studies that explicitly look at how e.g. lack of sleep reduces productivity.)

Exactly what emotion the title reflects might depend upon whether the worsening was an intended result, or even how the team were able to refocus and seize upon the adverse outcomes. The tone of the title could even express surprise: some senior academics may already have a generally low opinion of student volunteers (as both naïve students and ones that have no better things to do than volunteer), but then managed to inadvertently engineer a situation in which particularly inept subjects sail well under the already very low bar of expectations for the study aims.
|}

==Transcript==
:[Heading:]
:Types of Scientific Paper

:[An array of 4 rows with 3 scientific papers each, is shown. We see the first page of each paper, but only its title is legible. Headings are shown as black lines, paragraphs of text are shown as several squiggly lines and figures are shown as empty white rectangles. Titles are as follows:]
:We put a camera somewhere new
:Hey, I found a trove of old records! They don't turn out to be particularly useful, but still, cool!
:My colleague is wrong and I can finally prove it
:The immune system is at it again
:We figured out how to make this exotic material, so email us if you need some
:What are fish even doing down there
:This task I had to do anyway turned out to be hard enough for its own paper
:Hey, at least we showed that this method can produce results! That's not nothing, right?
:Check out this weird thing one of us saw while out for a walk
:We are 500 scientists and here's what we've been up to for the last 10 years
:Some thoughts on how everyone else is bad at research
:We scanned some undergraduates

==Trivia==
*Originally, this comic's title text misspelled "volunteers" as "volunters".
*Another comic, [[2012: Thorough Analysis]], similarly categorizes or mocks research papers.

==Derivatives==
The comic inspired many derivatives, changing the paper titles to be more relevant to specific fields.

The hashtag [https://twitter.com/search?q=%23TypesOfScientificPapers&src=typed_query&f=live #TypesOfScientificPapers] on Twitter includes many of these.

There is a [https://observablehq.com/@guillaume-levrier/xkcd-types-paper generator].

There is a [https://app.milanote.com/1LDuH91krMUK9z moodboard compiling hundreds of them].

Some examples include:
{| class="wikitable"
| https://twitter.com/neil_chilson/status/1388216386967715846 || Privacy Paper
|-
| https://twitter.com/SamLMontano/status/1388268078279049217 || Disaster Science Paper
|-
| https://twitter.com/jfbastien/status/1388229180211404803 || C++ Standards papers
|-
| https://twitter.com/waiterich/status/1388207060412682247 || Scientific Paper (Food, Land, and Natural Climate Solutions Version)
|-
| https://twitter.com/stefan_d_jevtic/status/1388192045920137216 || Hematology
|-
| https://twitter.com/jeffpeapod/status/1388185831140118529 || Papers for Grad Students
|-
| https://twitter.com/EdinburghKnee/status/1388069182642794496 || Ortho Paper
|-
| https://twitter.com/j_remy_green/status/1387960392954138624 || Law Paper
|-
| https://twitter.com/JavierApfeld/status/1387891336515362819 || Aging Paper
|-
| https://twitter.com/Gabeincognito/status/1387873643435216897 || Infosec Paper
|-
| https://twitter.com/acarriebear/status/1387870050581889024 || Toxicology
|-
| https://twitter.com/yesitsnicholas/status/1387865583908114432 || Neuroscience
|-
| https://twitter.com/nexel_art/status/1388263392545280009 || Archeology
|-
| https://twitter.com/skinnyfatPhD/status/1388253551013498882 || Metabolism
|-
| https://twitter.com/zamanian_/status/1388179675806158848 || Parasitology
|-
| https://twitter.com/PWGTennant/status/1387734254960975881 || Epidemiology and Public Health
|-
| https://twitter.com/DrIanKellar/status/1387760304818372620 || Health Psychology
|-
| https://twitter.com/nappqm/status/1388098251136589824 || Pest Science
|-
| https://twitter.com/theangelremiel/status/1388134620219297793 || Clinical Paper
|-
| https://twitter.com/plantspipettes/status/1387825850372997121 || Plant science
|-
| https://twitter.com/girlandkat/status/1388030240358768642 || Planetary Science
|-
| https://twitter.com/Nesquixotic/status/1387848121342853122 || History
|-
| https://twitter.com/SamLemonick/status/1388177531703070722 || How a reporter sees types of science papers
|-
| https://twitter.com/AndrewBarnas/status/1388161745684996098 || Scientific Paper PAYWALL meta-joke
|-
| https://twitter.com/ctdicanio/status/1388630827857289221 || Phonetics
|-
| https://twitter.com/ProfSimonFisher/status/1388096934343233537|| Language Research
|-
| https://twitter.com/jeanburgess/status/1388245879119781889 || Internet Studies
|-
| https://twitter.com/drzimmermann/status/1388526687814656004 || AI Ethics
|-
| https://twitter.com/ElephantEating/status/1388552610236403714 || Energy systems modelling 1
|-
| https://twitter.com/WPSchill/status/1388584606375493634 || Energy systems modelling 2
|-
| https://twitter.com/oikoweather/status/1388533147768434689 || Building energy modelling
|-
| https://twitter.com/BrynnTannehill/status/1388947303025844225 || Articles on trans people
|-
| https://twitter.com/jiaqikangjiaqi/status/1389225735202607115 || Types of diaspora writing
|-
| https://twitter.com/jdporterlive/status/1388192751653687297 || Literarcy Criticism
|-
| https://twitter.com/spiroferrer/status/1388169795674120193 || Urban planning
|-
| https://twitter.com/ChanceBonar/status/1388266744784080903 || Biblical studies
|-
| https://twitter.com/AmesCG/status/1389368675887554562 || A certain genre of center-right opinion column
|-
| https://twitter.com/jonathanagray/status/1388527626495594504 || Media studies
|-
| https://twitter.com/awaisaftab/status/1388133087356325888 || Psychiatry
|-
| https://twitter.com/OriPomson/status/1388911680277651462 || International Humanitarian Law (aka 'Law of Armed Conflicts')
|-
| https://bsky.app/profile/carbon-cyclist.bsky.social/post/3lhkha43wfc2v || Arctic-Boreal

|}

{{comic discussion}}

[[Category:Scientific research]]
[[Category:Science]]

3176: Inverted Catenaries

2025-12-04T16:40:36Z

Xkcd explainer: fixed grammatical errors

{{comic
| number = 3176
| date = December 3, 2025
| title = Inverted Catenaries
| image = inverted_catenaries_2x.png
| imagesize = 317x317px
| noexpand = true
| titletext = Some tires are marketed as 'all-shape tires,' but if driven in a climate with both inverted catenary falls and triangle falls, they wear out really fast.
}}

==Explanation==
{{incomplete|This page was created BY A TRAPEZOIDAL WHEEL. Don't remove this notice too soon.}}

During the winter, in snowy areas, people need to replace their typical, all-season tires with snow tires made specifically for the slick environment. In this comic, instead of snow, rounded shapes called inverted catenaries fall from the skies. On a plane covered in inverted catenaries all the same size, square wheels whose side length matches the arc length of the catenary are capable of rolling smoothly, contrary to how they would act on a normal road. Regular wheels would cause a significantly bumpier ride on this terrain, so Cueball plans to swap them out with {{w|Square wheel|square wheels}} to better suit the season.

Mathematicians have found [https://mathtourist.blogspot.com/2011/05/riding-on-square-wheels.html what types of roads would suit weird wheels the most], and inverted catenaries are best suited for a square wheel. People have made real tracks demonstrating this.

Note however, this assumes the catenaries are arranged periodically with no spacing between them, fully cover the surface, and are consistent in shape and orientation. The orientation also would restrict the direction of travel, effectively meaning your vehicle would be travelling on rails.

The title text mentions all-shape tires (as a play on {{w|Off-road tire#All-terrain|all-terrain tire}}), which is advertised to supposedly fit any shape road. However, different shapes would require very different wheels; for example, falling triangles would form a sawtooth road, for which one would optimally require wheels pasted together from pieces of an equiangular spiral. Any hypothetical all-shape wheel would wear out very quickly on most surfaces.

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[Megan and Cueball are walking as inverted catenaries fall from the sky. A few have landed in a regular formation, all flat-side down and next to each other.]
:Cueball: Oh wow, the first inverted catenary fall of the year!
:Cueball: Time to swap out my all-season tires for square ones.

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

3120: Geologic Periods

2025-07-27T07:58:44Z

Xkcd explainer: "proportionally long neck" suggests the neck lenght is normal for the size, that is not the case, changed to "disporoportionally"

{{comic
| number = 3120
| date = July 25, 2025
| title = Geologic Periods
| image = geologic_periods_2x.png
| imagesize = 611x557px
| noexpand = true
| titletext = Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.
}}

==Explanation==
{{incomplete|This page was created by a Cretaceous raptor. Don't remove this notice too soon.}}

{| class="wikitable"
!Period
!Dates (millions of years ago)
!My Favorite Part
!My Biggest Complaint
!Explanation
|-
|Precambrian
|4500-539
|Life develops
|Snowball Earth episodes
|The {{w|Precambrian}} (italicized in the comic since it's not a {{w|Period (geology)|geologic period}}) is the first 88% of Earth's history, including the time 4.1 to 3.4 billion years ago when life on Earth began. The {{w|Snowball Earth}} hypothesis says that during some time spans in the past, Earth became nearly or entirely frozen, with no liquid water on the surface. It's related to the idea of the {{w|Greenhouse_and_icehouse_Earth#Icehouse_Earth|icehouse Earth}}, times when the planet fluctuates between glacial and interglacial periods (such as now).
|-
|{{w|Cambrian}}
|539-487
|Trilobites!
|Evolution could stand to calm down a little
|The {{w|Cambrian explosion}} was a sudden radiation of complex life forms when nearly all important animal phyla, or precursors to them, appeared. {{w|Trilobite|Trilobites}}, a lineage of {{w|Arthropod|arthropods}} (related to present-day insects and spiders), was one of the groups that appeared during the Cambrian. Fossil trilobite specimens are abundant and charismatic, and attract the attention of amateur and professional enthusiasts.
|-
|{{w|Ordovician}}
|487-443
|Earth might have had rings
|Scary volcanic eruption in North America
|Due to the non-random location of impact of one type of meteorite, {{w|Rings_of_Earth|it is proposed}} that those have formed a planetary ring system around Earth before colliding with it. The volcanic eruption(s) that deposited the {{w|Deicke_and_Millbrig_bentonite_layers|Deicke and Millbrig ashfall layers}} during the Late Ordovician are thought to have been among the largest in the last 600 million years of Earth history. The volcano(es) involved may have been among those formed during the mountain-building event in what is now northeastern North America that is called the {{w|Taconic_orogeny|Taconic orogeny}}.
|-
|{{w|Silurian}}
|443-420
|First land animals
|Earth's newfound mold problem
|Green plants first became established on land during the Ordovician period, after having evolved ways to protect themselves from desiccation and ultraviolet light. During the Silurian, land animals (mostly arthropods resembling {{w|Kampecaris|millipedes}}) followed the plants - and mycelial fungi ("mold") evolved to attack them and decompose their remains.
|-
|{{w|Devonian}}
|420-359
|Big mountains in Boston
|Yeah, sure, what those giant killer fish needed was ''armor''
|A series of mountain-building events, during the middle to late Devonian, that are collectively termed the {{w|Acadian_orogeny|Acadian orogeny}} resulted in a section of the present-day Appalachian Range from the Canadian maritimes to the Carolinas, including what is now the Boston area of Massachusetts. (At the time, Boston was in the tropics, just south of the equator.) {{w|Placoderm}} fishes, which were common in but did not survive the Devonian, were characterized by plates of {{w|Dermal_bone|dermal bone}} in the head and thoracic portions of the body. Not all placoderms were giants, or apex predators. The best guess as to why placoderm fishes had these bony plates is that they helped protect the fishes from predation by other placoderms.
|-
|{{w|Carboniferous}}
|359-299
|Cool forests
|Bugs too big
|The {{w|Carboniferous#Terrestrial_invertebrates|'bugs' in this period}} included the largest-ever known land invertebrate, a {{w|Arthropleura|2.6-m (8.5-ft) millipede-like animal}}; the largest-ever known flying insect, resembling a {{w|Meganeura|dragonfly with a wingspan of ~75 cm (30 in)}}; and a {{w|Pulmonoscorpius|70 cm (2 ft 4 in) scorpion}}.
|-
|{{w|Permian}}
|299-252
|Pangea
|Google "The Great Dying"
|{{w|Pangaea}} was the most recent supercontinent containing nearly all of Earth's landmass. The Great Dying, more formally known as the {{w|Permian-Triassic extinction event}}, occurred at the end of the Permian and is the most severe of Earth's {{w|Extinction_event#The_"Big_Five"_mass_extinctions|'Big Five' mass extinction events}}. In it, 81% of marine species and 70% of terrestrial vertebrate species were wiped out.
|-
|{{w|Triassic}}
|252-201
|Tanystropheus
|Damage to Canada still visible from space at Manicouagan
|{{w|Tanystropheus}} was a basal archosaur (not a dinosaur) with a disproportionally long neck. {{w|Manicouagan Reservoir}} is a ring-shaped lake, the remains of the crater caused by a 5-km (3-mi) asteroid hitting {{w|Quebec}}.
|-
|{{w|Jurassic}}
|201-143
|Birds
|Parasitoid wasps
|Birds are cool.{{Citation needed}} Parasitoid wasps are not; their reproduction cycle is such a grisly process that it caused a {{w|Ichneumonidae#Darwin_and_the_Ichneumonidae|crisis of faith}} among 19th-century European scholars.
|-
|{{w|Cretaceous}}
|143-66
|Raptors
|Raptors
|[[:Category:Velociraptors|Raptors]]
|-
|{{w|Paleogene}}
|66-23
|Pretty horseys!!!
|Paleocene-eocene thermal maximum
|The {{w|Paleocene–Eocene Thermal Maximum}} was a time where the global average temperature rose by around 5-8 °C in a relatively short period of time.
|-
|{{w|Neogene}}
|23-2.6
|Forests of Dracaena dragonblood trees
|Zanclean flood
|{{w|Dracaena draco}} and {{w|Dracaena cinnabari}} trees are a source of {{w|dragon's blood}}, a naturally occurring bright red resin with uses including as a varnish and a dye.
The {{w|Zanclean flood}} is theorized to be the flood that refilled the Mediterranean Sea.
|-
|{{w|Quaternary}}
|2.6-present
|Burrito invented
|Whoever picked the name for the third period of the Cenozoic
|Randall jokes that, in the last 2.6 million years, his favorite moment was the invention of the {{w|burrito}}, rather than many other, much more significant discoveries. The precise origin of the burrito is not known, but the {{w|Maya civilization}} used to make food resembling burritos as early as 1500 BC.
The third period of the {{w|Cenozoic}} Era is the Quaternary era, named by Jules Desnoyers in 1829. This naming is controversial; the {{w|International Commission on Stratigraphy}} is proposing to abolish it.
|}

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

{{comic discussion}}<noinclude>
[[Category:Charts]]
[[Category:Geology]]
[[Category:Velociraptors]]
[[Category:Animals]]
[[Category:Food]]
[[Category:Comics featuring Cueball]]

3119: Flettner Rotor

2025-07-24T07:42:24Z

Xkcd explainer: elaborated transcription of picture

{{comic
| number = 3119
| date = July 23, 2025
| title = Flettner Rotor
| image = flettner_rotor_2x.png
| imagesize = 385x359px
| noexpand = true
| titletext = "And in maritime news, the Coast Guard is on the scene today after an apparent collision between two lighthouses."
}}

==Explanation==
{{incomplete|This page was created by a spinning shaft. Don't remove this notice too soon.}}

Randall is pointing out that a {{w|Flettner rotor}} can make a boat look like a lighthouse — and, since lighthouses are immobile while sailboats are not,{{Citation needed}} this would make other boats give a boat with the above affixations the right of way, by the simple expedient of avoiding its general vicinity and the presumed subsurface navigational hazards.

A vertical-axis Flettner rotor is a smooth cylinder which is spun along its axis. As air passes across it from the side, an aerodynamic force is generated at a right-angle (i.e. forwards) to propel the boat in the desired direction. If a directional light were attached at the top, it too would spin, sending out periodic flashes of light just like a lighthouse. Or, as it appears to be in the comic, a fully working {{w|Lighthouse#Components|lantern house}} may be fixed to the top of the non-rotating core to the rotor, within which its light rotates at a more usual rate independent of that of the vertical rotor.

A vessel directly in the path of the moving boat would have to perhaps consider the possibility that they are drifting towards rocks, but how one ''at anchor'' (and not obviously dragging its moorings) could reconcile the conceptual movement, especially if GPS data gives no reason to believe it, is left unexplained.

The title text describes "an apparent collision between two lighthouses", which could refer to two Flettnerized boats colliding with each other because they were ''both'' assuming that everyone else will give them the right of way.

Alternatively, a single Flettnerized boat complacently collided with an actual lighthouse, having similarly dismissed it as another boat that should have been avoiding itself. Thus, tangentially alluding to the old {{w|Lighthouse and naval vessel urban legend|urban legend}} in which a naval vessel insists that another radio operator at sea diverts course to avoid a collision, demanding right of way by citing their military importance, only to be embarrassed when the other operator reveals they are not another sea vessel, but a lighthouse.

==Transcript==
:[A panel showing Cueball standing on a Flettner Rotor Sailboat, which is decorated with rocks and a lighthouse-top on the Flettner Rotor.]
:[Text beneath panel:]
:Sailing tip: If you have a Flettner Rotor Sailboat, you can add some fake plastic rocks and a light to make other boats give you the right of way.

{{comic discussion}}<noinclude>

3113: Fix This Sign

2025-07-11T13:50:51Z

Xkcd explainer: /* Transcript */

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

==Explanation==
{{incomplete|This page was created by a MISaLI NED CO LUM. Don't remove this notice too soon (before sufficient donations are received).}}

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

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

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

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

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

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

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

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

The title text refers to another common annoyance seen in signs: the use of {{w|backslash}}es in {{w|URL}}s. URLs are defined to use forward slashes (/) rather than backslashes (\), which are used in Windows {{w|Path_(computing)|pathnames}}. Due to the widespread usage of both URLs and Windows pathnames, it is not uncommon for someone to mistakenly use backslashes in URLs, which isn't always supported. (Forward slashes in Windows paths, however, ''are'' supported via Win32-to-NT path conversion.) This annoyance was also discussed in [[727: Trade Expert]].

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[A single panel containing a large, elevated sign with Ponytail standing in front of it.]

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

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

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

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

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

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

1517: Spectroscopy

2025-03-23T18:06:14Z

Xkcd explainer: changed on-line to online because current preffered spelling changed over the years

{{comic
| number = 1517
| date = April 27, 2015
| title = Spectroscopy
| image = spectroscopy.png
| titletext = Although right now I'm more excited about ESPRESSO's radial velocity measurements, so I'm listening to This Kiss, her song about measuring "centrifugal motion" on "a rooftop under the sky".
}}

==Explanation==
This comic mixes the method of using ''{{w|spectroscopy}}'' to detect {{w|oxygen}} on {{w|exoplanets}} (planets outside our {{w|Solar system}}) with [http://www.azlyrics.com/lyrics/faithhill/breathe.html the lyrics] for the {{w|Faith Hill}} song "{{w|Breathe (Faith Hill song)|Breathe}}" (listen to [https://www.youtube.com/watch?v=yCmsZUN4r_s "Breathe" on YouTube]).

From the lyrics:
:''I watch the sunlight''
:''dance across your face''
[...]
:''I can '''feel''' you breathe''
In the comic the word "feel" has been changed to "see". The two first panels are one line in the song. The last line is from the chorus and is repeated five times during the song, although not right after the first two lines.

In the first and second panel the singer examines the spectra of a remote planet by ''watching the sunlight'' during the {{w|Transit (astronomy)|transit}} of the planet as this sunlight ''dances across the planet's face''. Finally we determine that breathable oxygen exists. Since we cannot (as Faith can) ''feel'' the planet we have to ''see'' it. And by doing this ''I can see you breathe''.

Measuring the light output of stars (spectra) we are able to determine a number of details of the star, including rotation, relative radial velocity, chemical composition, temperature, and to some degree, distance and size. When a planet, as pictured, moves between the star and the observer, then by looking at the spectrum received, the viewer is able to determine the contents of the planet's atmosphere from the specific wavelengths of light that are {{w|Absorption spectroscopy|absorbed}} in this. If it turns out that the atmosphere absorbs the lines corresponding to molecular oxygen (O2) this is a clear indication that the planet has large quantities of breathable oxygen (but {{w|Exoplanet#Abiotic_oxygen|not necessarily life}}). However, there must be oxygen in large amounts in the atmosphere to sustain most of the life forms that we know of here on Earth (though {{w|Anaerobic_organism|not all}}). It is thus clear why [[Randall]] would be interested in exoplanets with oxygen.

This comic came out four days after this article about [http://www.huffingtonpost.com/2015/04/23/nasa-nexss-search-for-life_n_7123788.html NASA's New NExSS Initiative]. {{w|NASA}} will search for signs of life on other planets, for instance by using "the light passing through the atmospheres of these exoplanets". And they "will study chemicals that have been detected on other worlds, such as oxygen and methane, to see if they were produced by biology".

The title text refers to determining {{w|radial velocity}} in the {{w|ESPRESSO}} program (Echelle SPectrograph for Rocky Exoplanet- and Stable Spectroscopic Observations). By noting that the radial velocity of the star changes slightly as the planet that orbits it moves around the star (centrifugal acceleration), the ESPRESSO program should be able to detect the masses of planets as they are moving towards the Earth in their orbit around their distant stars. The ESPRESSO program is so precise that it should be able to detect {{w|Terrestrial planet|planets as small as Earth}} and the other of the Solar system's inner planets.

Randall is now even more excited about ESPRESSO than he is about the oxygen levels, because it is now possible to detect these "very" small planets. So he is no longer listening to "Breathe", but to another Faith Hill song: "{{w|This Kiss (Faith Hill song)|This Kiss}}" (listen to [https://www.youtube.com/watch?v=dls_cBmUt7Q "This Kiss" on YouTube]).

From the [http://www.sweetslyrics.com/59372.Faith%20Hill%20-%20This%20Kiss.html lyrics]:
:''It's '''centripetal''' motion''
[...]
:''On '''the''' rooftop under the sky''
The first line is part of the chorus and it is repeated four times, but Randall has changed the main word to "centrifugal". There is, however, [http://www.azlyrics.com/lyrics/faithhill/thiskiss.html disagreement] online whether it is centripetal or centrifugal.

The second line is not sung in connection with the chorus, and it is only changed a bit, so "the" is changed to "a". Also the "on" which is part of his line here is not part of the quoted line in the title text.

The song is not about measuring but, of course, about "The Kiss". Since the ESPRESSO is part of the {{w|Very Large Telescope}}, it is located on the {{w|Cerro Paranal}} mountain in the {{w|Atacama desert}} in {{w|Chile}} at an elevation of 2,635 meters (8,645 ft.) above sea level. So it could be said that it is measuring on a rooftop under the sky. Although it is radial velocity it measures, not {{w|Centrifugal force|centrifugal motion}}, the object it does measure will all be experiencing this {{w|fictitious force}} (also see [[123: Centrifugal Force]]), as the planets are in orbit around a star.

Randall has previously made [[:Category:Exoplanets|several references to exoplanets]] in his comics, most notable are the two comics with the same name: [[786: Exoplanets]] and [[1071: Exoplanets]]. The latter comic came out when there were exactly 786 exoplanets found. Today more than 1900 have been discovered (1915 as of Wikipedia on the release day of this comic), much more than twice that amount. And now they can find even smaller planets, and detect the atmosphere. Much have happened since the first exoplanet comic came out in 2010. Five comics later in [[1522: Astronomy]] he mentions {{w|astrobiology}} in the title text, closely relating it to this comic.

==Transcript==
:[A dark panel with a bright star in the center. To the left a planet (drawn as a new moon) approaches the star. Text is written above in white with two musical notes, one on each side of the text.]
:I watch the sunlight

:[Same image but now the planet transits the star. Small lines around the planet indicate the atmosphere, as seen from the light from the star passing through it. Text is again written above in white with two different musical notes, one on each side of the text.]
:Dance across your face

:[A white frame with a black line. It Is the spectrum of the planets atmosphere. Two distinct absorption peaks are visible. The first one is labeled with an arrow. Text is again written above, now in black, with two, again, different musical notes, one on each side of the text.]
:I can see you breathe
:Label: O2

:[Below the panels is the following caption:]
:Faith Hill on exoplanet spectroscopy

{{comic discussion}}
[[Category:Comics with inverted brightness]]
[[Category:Songs]]
[[Category:Science]]
[[Category:Astronomy]]
[[Category:Exoplanets]]

2964: Olympic Sports

2024-07-29T17:37:50Z

Xkcd explainer: added explanation of weightlifting

{{comic
| number = 2964
| date = July 26, 2024
| title = Olympic Sports
| image = olympic_sports_2x.png
| imagesize = 553x328px
| noexpand = true
| titletext = Thankfully for everyone involved, the Winter Olympics officials spotted me and managed to stop me before I got to the ski jump.
}}

==Explanation==
{{incomplete|Created by A VERY CONCERNED OLYMPIC OFFICIAL - Provide an explanation of each sport for the convenience of those unfamiliar with some or all listed sports. Do NOT delete this tag too soon.}}

This comic was officially published on the day of the opening ceremony of the {{w|2024 Summer Olympics|2024 Paris (Summer) Olympics}}, though it actually appeared early the following day.

In this comic, [[Randall]], who has no athletic training, imagines himself participating in various Olympic events, with his degrees of failure measured in terms of their humor potential.

{| class="wikitable"
|+ Olympic sports ranked by how funny it would be if a regular person competed
! How funny !! Sport !! Reason !! Depiction
|-
|rowspan=5| Not that funny || {{w|Rowing}} - One or more people row a boat to a destination.|| The person would struggle to row effectively, falling out of cadence and fouling the oars of the other rowers in their boat. However, if Randall competed in the single sculls, such coordination would not be an issue, and he would likely just be much slower than the other competitors. Or fall in the water. ||
|-
| {{w|Fencing}} - Two contestants attempt to land hits on each other with a long fencing weapon.|| They might fail to land any hits, but it wouldn't be overly humorous. Randall is evidently not masochistic enough to consider putting on protective equipment disastrously wrong and hospitalization funny. ||
|-
| {{w|Weightlifting}} - Contestants lift weights, getting heavier with each round, until all but one fail to lift the weight.|| They might just fail to lift the weights. ||
|-
| {{w|Golf}} - Contestants attempt to hit, with golf clubs, a golf ball into one or more holes in as small a number of hits as possible.|| They would likely miss the ball or hit poorly, due to an incorrect stance/swing when hitting, using a club whose loft (angle of the front face) is inappropriate, or just basic lack of skill. || The illustration depicts Randall missing the hole at very close range.
|-
| {{w|Archery}} - Using a bow and arrow, contestants attempt to hit a target with as much accuracy as possible.|| Arrows might miss the target, but it's not particularly amusing (unless Randall forgoes armbraces & discovers the bowstring's propensity for smacking the inside of his wrist after releasing it). || Randall misses all his shots on the target.
|-
|rowspan=5| Pretty funny || {{w|Swimming}} - Contestants swim to a destination or complete lengths as fast as possible.|| They might struggle to stay afloat (particularly in open water swimming, where they would be buffeted by other contestants) or [https://en.wikipedia.org/wiki/Eric_Moussambani swim awkwardly]. They are also likely to have a markedly different physique to the other competitors, which would have a comic effect. ||
|-
| {{w|Long jump}} - Contestants, with a running start, attempt to jump as far as possible.|| They would likely make a very short jump, or perhaps foul every jump. ||
|-
| {{w|Pole vault}} - Using a bendable pole, contestants attempt to propel (vault) themselves over a bar.|| They might miss the plant and end up dropping the pole and running under the bar. If they did manage to get some lift, but failed to get enough to reach the mat, it would probably be concerning, rather than funny. ||
|-
| {{w|Diving}} - Contestants attempt to fulfil multiple criteria while diving into water.|| Awkward or painful-looking dives could ensue. Potential for injury would be high. ||
|-
| {{w|Hurdles}} - Contestants run on a track with hurdles positioned at various places.|| They might trip and fall over the hurdles, or just knock them all over as they fail to clear them. || Randall repeatedly and unpleasantly runs into the hurdles, unable to jump over any of them. He has his arm raised bent in front of his face in a classic hurdler's pose, but appears to have failed to get much, if any, height off the ground.
|-
|rowspan=5| Incredibly funny || {{w|Figure skating}} [The only Winter Olympic discipline featured in the main comic] Competitors perform artistic routines set to music while skating on an ice rink, and are judged on a combination of skating skill, composition, and presentation. || They might slip and fall continually on the ice (high risk for sprained joints or bone fractures). This might have particular comic potential if Randall were skating as part of a pair, awkwardly attempting to lift and spin a partner, or perhaps doing nothing but being lifted and dragged around by them. ||
|-
| {{w|Horizontal bar}} - A horizontal bar is used to perform gymnastics.|| They might fail to perform any flips or lose their grip on the bar, falling to the safety mats below. In all likelihood, having been lifted to the bar, they would simply hang helplessly beneath it, managing minimal swings backwards and forwards. ||
|-
| {{w|Equestrian sports}} - Various activities involving the use of horses.|| They might struggle to control the horse or fall/get thrown off. || Randall is completely unable to control his horse. He is in the process of falling off and is flailing his arms.
|-
| {{w|Freestyle BMX}} - Contestants ride BMX bikes and perform various tricks, and are then judged by trick quality.|| They might crash or fail to perform tricks. ||
|-
| {{w|Pommel horse}} - Using a gymnastic device somewhat similar to a horse, gymnasts perform various tricks.|| They might awkwardly flop around, fall off, or lose their balance & risk crushing {{tvtropes|GroinAttack|a particularly squashy part}} of their anatomy, which could, depending on one's sense of humor, the context, & the exact aesthetics of the incident, elicit laughter. || Randall is attempting to perform a routine, but the rather basic {{w|The_Lexicon_of_Comicana|agitrons}} surrounding him suggest he is not very graceful, balanced, or typically dynamic. However, he seems to be unaware of this, excitedly demanding that people look at what he presumably thinks is an impressive feat of athleticism.
|}

The title text may be a reference to ski jumper {{w|Vinko Bogataj}}, whose spectacular crash at a (non-Olympic) {{w|Ski_flying|ski flying}} event in 1970 in Oberstdorf, (then) West Germany became emblematic of the expression "the agony of defeat" in the opening narration of the popular US television program "{{w|Wide World of Sports (American TV program)|Wide World of Sports}}". Alternatively the reference may be to {{w|Eddie the Eagle}}, whose poor performance in the {{w|Ski_jumping|ski jump}} at the {{w|1988 Winter Olympics}} led to the introduction of a rule requiring entrants to be ranked internationally in the top 50 and top 30%.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Header above three panels:]
:Olympic Sports ranked by how funny it would be if I, a regular person without athletic training, snuck onto the team to compete:
:[Three panels are shown with a header, a bullet list with five listed sports in each, and one or two depictions of sports.]

:Not that funny
:Rowing
:Fencing
:Weightlifting
:Golf
:Archery
:[Cueball putts a ball with a golf club and misses the hole from a close distance.]
:[Cueball is aiming with a bow. Three arrows are on the ground at various distances from the target.]

:Pretty funny
:Swimming
:Long jump
:Pole vault
:Diving
:Hurdles
:[Cueball runs stomach-first into a hurdle, while holding an arm in front of his head. Another hurdle behind him has fallen down.]
:Cueball: [Bonk] Ow! [Bonk] Ow!

:Incredibly funny
:Figure skating
:Horizontal bar
:Equestrian
:BMX freestyle
:Pommel horse
:[Cueball tries to balance himself on a pommel horse. His both hands and one leg are down, while the other leg is slightly raised.]
:Cueball: Look! Look!
:[A horse rider wearing a black helmet is struggling to maintain balance on the running horse, with both hands and one leg raised.]
:Horse rider with black helmet: AAAAA!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Sport]]
[[Category:Rankings]]

Talk:1547: Solar System Questions

2024-05-15T08:09:49Z

Xkcd explainer: question to wierd answered-not-true-boolean

I wonder if "What's the deal with Miranda?" is talking about one of [https://en.wikipedia.org/wiki/Miranda_(moon) Uranus's satellites] or if it's a Firefly/Serenity reference? [[User:Keavon|Keavon]] ([[User talk:Keavon|talk]]) 15:31, 6 July 2015 (UTC)
* That was my reaction too. Randall is (as he should be) slightly obsessed with Firefly. [[User:Cosmogoblin|Cosmogoblin]] ([[User talk:Cosmogoblin|talk]]) 19:12, 6 July 2015 (UTC)
** There are other Mirandas... Miranda Sings, Miranda Hobbes, etc. [[User:Smperron|Smperron]] ([[User talk:Smperron|talk]]) 13:36, 8 July 2015 (UTC)
*** Given that the title of the comic is "Solar System Questions", and Miranda in firefly is not in the solar system, this is clearly a reference to the Uranus moon. [[User:Niffe|Niffe]] 00:09, 10 July, 2015
**** If it's a reference to Miranda from ''Sex And The City'', it's still a valid question. [[Special:Contributions/108.162.241.8|108.162.241.8]] 12:42, 13 July 2015 (UTC)

Many of the entries can be found at https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics [[User:Cschwenz|Cschwenz]] ([[User talk:Cschwenz|talk]]) 16:16, 6 July 2015 (UTC)

The title text is a reference to the Futurama episode "Butterjunk effect" http://theinfosphere.org/The_Butterjunk_Effect. {{unsigned ip|188.114.98.29}}
* I suggest it's much more likely to be a reference to Randall's own obsession with humans flying with wings: [[620]], https://what-if.xkcd.com/30/. [[Special:Contributions/108.162.250.161|108.162.250.161]] 01:00, 8 July 2015 (UTC)

What's Titan like? Refernece to Gattaca (https://www.youtube.com/watch?v=lZa83dTf4JA)? [[User:Nk22|The Twenty-second. The Not So Only. The Nathan/Nk22]] ([[User talk:Nk22|talk]]) 16:23, 6 July 2015 (UTC)

I wonder if Randal is using us as unpaid researchers to answer his questions for him?[[Special:Contributions/173.245.48.89|173.245.48.89]] 16:53, 6 July 2015 (UTC)
* Crowd-sourcing space probes? I certainly hope so!! [[User:Cosmogoblin|Cosmogoblin]] ([[User talk:Cosmogoblin|talk]]) 19:12, 6 July 2015 (UTC)
** I was also thinking that, or at least he might have been thinking, "This oughtta keep those silly people on the ExplainXKCD wiki busy!". ;) [[User:KieferSkunk|KieferSkunk]] ([[User talk:KieferSkunk|talk]]) 20:42, 6 July 2015 (UTC)

Timing is good as it has recently been shown that red organics (Tholins) are produced by the particular UV wavelength called 'Lyman-Alpha' which is almost as bright on Pluto's night-side due to starshine as it is from the Sun during its daytime... the Edgeworth-Kuiper Belt may be the original Red-light District. Go New Horizons! [[User:Squirreltape|Squirreltape]] ([[User talk:Squirreltape|talk]]) 15:13, 7 July 2015 (UTC)

Ice Spikes could be a reference to the Ice Spikes biome in Minecraft: http://minecraft.gamepedia.com/File:Ice_Plains_Spikes.png [[User:Daedalus|Daedalus]] ([[User talk:Daedalus|talk]]) 10:12, 7 July 2015 (UTC)

The last question/the title text could also refer to Robert A. Heinleins "The Menace from Earth": https://en.wikipedia.org/wiki/The_Menace_from_Earth [[User:Bichlesi|Bichlesi]] ([[User talk:Bichlesi|talk]]) 01:13, 8 July 2015 (UTC)

The "big white things in Titan's lakes" may also refer to the [http://news.nationalgeographic.com/news/2014/11/141111-titan-lake-island-space-science/ magic islands] that were observed by Cassini.--[[Special:Contributions/108.162.221.90|108.162.221.90]] 02:56, 8 July 2015 (UTC)

If they wore wings and could fly you would end up with the Butterfly Derby on the moon from the Futurama Episode "The Butterjunk Effect" [[Special:Contributions/108.162.216.146|108.162.216.146]] 06:23, 14 July 2015 (UTC)

Ideas about the "What pushes spaceships slightly during flybys?": (1) Gravity is slightly stronger near the equator due to the faster relative motion of the planet surface (which is why the plane of orbits of moons, planets, rings, galaxies try to align near the equator of the central mass). (2) Earth's mass is not 100% evenly distributed within it's volume causing minor gravitational distortions. (3) Flybys "behind" the Earth as it moves in its orbit gravitationally slow the Earth (very very slightly) robbing it of KE and giving it to the craft. Flybys "in front" of the Earth in orbit do the reverse. - [[User:Ezfzx|Ezfzx]] ([[User talk:Ezfzx|talk]]) 17:46, 1 December 2021 (UTC)

I think this page, perhaps more than any I've run across so far, can really use a few more sets of eyes. I would even suggest that the page is '''incomplete''', because of all the new science we've done in the past decade. It would be nice if we could label the status of these questions. "Which other moons have seas" answer is clearly incomplete, as it doesn't list "several" contenders. [[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 10:41, 14 February 2024 (UTC)
:I just added the color-coded column, which might be of interest and helpful when looking at this as a checklist. [[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 11:02, 14 February 2024 (UTC)
:Thank you, anonymous IP editor, for adding so much information to this page! That was exactly what I was hoping when I marked this page as incomplete, and it's amazing to see how much new knowledge we've gained in the past decade. The floating islands of Titan particularly wowed me. I'm beyond pleased! [[User:Maplestrip|Maplestrip]] ([[User talk:Maplestrip|talk]]) 13:23, 23 April 2024 (UTC)

Why are so many Things where there is clearly absolutely no answer give not marked as no, but either partly, maybe, or even yes? how did this happen?