explain xkcd - User contributions [en]

3121: Kite Incident

2025-08-08T06:21:45Z

2600:1700:31C0:9F50:D055:C58E:4B0:B6F6: /* Explanation */ Mentioned string snagging on rocket as another reason why air travel may have been shut down

{{comic
| number = 3121
| date = July 28, 2025
| title = Kite Incident
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = kite_incident_2x.png
| imagesize = 740x1610px
| noexpand = true
| titletext = Detectives say the key to tracking down the source of the kites was a large wall map covered in thumbtacks and string. 'It's the first time that method has ever actually worked,' said a spokesperson.
}}

==Explanation==
In this comic [[Megan]] is setting up a kite as [[Cueball]] arrives. Megan sets up the kite using a fishing line, which is unorthodox but not unheard of. Because the connection between the holding point and the lofted kite will form a {{w|catenary}} hanging down, after paying out sufficient line toward a kite increasingly far downwind, the line starts to dip and possibly touch the ground. Cueball suggests adding another kite at that point, after which they can then pay out more line and keep the line raised off the ground for additional distance.

They then get into a loop of adding more line to accommodate a stock of kites, and then more kites to support the line, until the kite chain reaches ludicrous proportions. The kites become so numerous and high-flying that they eventually blow in a circle around a significant part of the planet, following a {{w|jet stream}}. A circle on the surface of the Earth that follows the line of latitude where Randall lives is about 18,500 miles long, though a circumpolar jet-stream would curve into higher and lower latitudes to possibly add a lot more distance (as well as being at a higher altitude, which would add a more predictable fraction to its length). If the kites have been dragged into a much smaller circle as the result of a kite and/or its string getting caught by an airplane, there's no evidence of this to either the comic's characters or to ourselves, and travel purely by extensive (albeit slower) atmospheric movement has been [[2805: Global Atmospheric Circulation|featured before]]. Modelling the line as a straight line stretching 15 degrees above the horizon, Megan has spent over 38km of fishing line by the time the first kite reaches the jet stream at 10km high, but the mean separation of kites is possibly not particularly far, based upon the heights of the figures in wider shots, and Megan has lost count of how many they deployed, anyway. The curve of the hanging tethers would be highly dependant upon the tension between the two points of suspension, as would the ability of any given kite to fly, but there is not enough clear information to discern to what limits these (and the fishing line) might constrain the scenario.

The sirens in the second-to-last panel refer to a visit by some law-enforcement agency. The string of kites circling the Earth has interfered with international air travel. Although the mass of any given kite and the presence of such a relatively light and fragile tether should not cause too much difficulty for the majority of airliners if their wing or body collides with the kite-chain, the danger of a kite being ingested into the engine would ''preferably'' be avoided out of an abundance of caution. This is true even if the presence of kites is known to be not a more solid danger rather than a mystery and/or {{w|2023 Chinese balloon incident|perceived threat}} which can lead to {{w|Air travel disruption after the 2010 Eyjafjallajökull eruption|air travel to be shut down}}. (Of course, with xkcd physics, the pilots may have been concerned that [[2148: Cubesat Launch|snagging on the kite string would pull Megan and Cueball off of their feet]].) Regardless of the actual degree of danger, the authorities react accordingly, and events culminate in Megan and Cueball being forced to issue a formal apology. Having their lawyer there might indicate they won't get away with just an apology, but maybe this is to show they meant no harm, to decrease the penalty they will face.

The title text alludes to an investigation technique seen in many types of media where the investigator {{tvtropes|StringTheory|pins text and photo evidence to a board}}, connecting related evidence with string. This technique is also made fun of in [[2244: Thumbtacks And String]]. Though often good enough for fictional purposes, at least to the extent that the plot demands, the text indicates that real-world uses of 'string on a map' to discover a useful result have not actually been successful. But in this case, the string on the map would be there to indicate the actual extent to the string ''in the air'', probably from various reports received from around the world, and apparently it had successfully led to the discovery of the location from which the string originated on the ground and the subsequent intervention against the duo's excessive kite-deployment activity.

Kites have been a [[:Category:Kites|recurring topic]] on xkcd since the early days. It has been three years since the last comic featuring kites, [[2632: Greatest Scientist]], six years since Cueball put one up, in [[2208: Drone Fishing]], and 10 years since Megan did so, for [[1614: Kites]].

==Transcript==
:[Cueball approaches Megan from the left. Megan is flying a kite, with the line attached to a spool.]
:Cueball: Ooh, flying a kite?
:Megan: Yeah. I found this big spool of fishing line in a closet.

:[In a silent panel, Cueball and Megan are seen from further away, indicating that the kite is flying higher.]

:[Cueball and Megan are seen from yet further away, indicating that the kite is flying still higher.]
:Cueball: Are we allowed to fly a kite this high? Should we Google whether there are rules?
:Megan: Eh, it's probably fine.

:[The line held by Megan leaves her hand almost horizontally before curving up. Cueball stands a little way downwind his hand up to the string, above head-height, as if supporting/stabilising it or testing its tendency to stay up.]
:Megan: The string is really starting to sag.
:Cueball: Maybe we could attach another kite? I'll go get one.

:[A new kite is attached just above the line, supporting it higher in the air, Megan's held end now leading up to the point it is joined.]
:Cueball: It worked!
:Megan: Nice!

:[Megan is feeding out line from a partly depleted spool, via a peg/ground anchor, with a knot visible a short way up the rising cord. Two further empty spoole are seen on the ground. Cueball is approaching with a box.]
:Cueball: I bought another package of string.
:Megan: Oh good, these spools are almost empty.
:Megan: I think we're in the jet stream.

:[Three empty spools, one spool in use and one unused spool surround Megan and Cueball, with one supporting kite visible on the line that Megan is still feeding out.]
:Cueball: How many kites are on there now?
:Megan: I've lost count.

:[Another silent panel, zoomed out to see at least a half self-supporting "kite-length" about ready to have a new kite added at the ground end, and almost the same amount of curve leading off-panel to the next (previously attached) kite, unseen. There are flat items (presumably kites), spools (one being the current one being fed out) and boxes (assumed to contain more kite material and/or spools behind and around the two small figures.]

:[A much larger panel with the same ground details but a wider view. Above the ascending line of kites there is now a second, horizontal line of kites, dangling furves of connecting chord, leading from off-panel left to off-panel right.]
:Cueball: Uhh...

:[Some kites, spools and boxes are around the two figures, now seen again in close-up.]
:Cueball: ...Did it blow in a circle?
:Megan: I don't know. Lemme look at a map of where the jet stream goes.
:Cueball: Hey, do you hear sirens?

:[A CNN logo is at the upper right of the panel. Megan stands at a lectern, with Cueball on one side and Ponytail, holding a briefcase, on the other. Illegible subtitle/sub-banner text appears at the lower left, lower right, and below them.]
:[A banner with white text on a black background:]
:Breaking: Kite Incident Duo Speaks
:Megan: On the advice of our lawyer, we would like to apologize for the events that shut down global air travel last week...

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Kites]]
[[Category:Aviation]]

3120: Geologic Periods

2025-08-08T06:04:53Z

2600:1700:31C0:9F50:D055:C58E:4B0:B6F6: /* Explanation */ Mentioned PETM's similarity to modern climate change

{{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 explanation should focus more on explaining the jokes in the comic rather than the history of life on Earth. There are still no explanations of the "birds" and "raptors" joke, which are the main jokes in the comic.
*The title text explanation could be shortened a bit.}}

This comic depicts a table representing planet Earth's geological time scale. For each period, [[Randall]] highlights his rather idiosyncratic likes and dislikes among their characteristics, instead of accompanying each geological name with facts pertinent to it, such as the duration of the period represented, the state of the Earth (e.g., glaciated), or the flora and fauna most common.

{| class="wikitable sortable"
!Period and date ({{abbr|{{w|Million years ago|MYA}}|Millions of years ago}})
!Randall's comments
!Explanation
|-
! rowspan="2" | {{w|Precambrian}} (4500⁠–⁠539)
|{{Yes|Life develops}}
|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.
|-
|{{No|Snowball Earth episodes}}
|According to the {{w|Snowball Earth}} hypothesis, during some time spans in the past Earth became nearly or entirely frozen, with no liquid water on the surface. This is similar to the {{w|Greenhouse and icehouse Earth#Icehouse Earth|Icehouse Earth}}, including now, when the planet fluctuates between glacial and interglacial periods.
|-
! rowspan="2" | {{w|Cambrian}} (539⁠–⁠487)
|{{Yes|Trilobites!}}
|{{w|Trilobite|Trilobites}} are related to present-day insects, crabs, and other arthropods, and appeared during the Cambrian.
|-
|{{No|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. Randall apparently thinks it all happened a little too fast.
|-
! rowspan="2" | {{w|Ordovician}} (487⁠–⁠443)
|{{Yes|Earth might have had rings}}
|Due to the location of impact of one type of meteorite, they may have formed a {{w|Rings of Earth|planetary ring system around Earth}} before colliding with it.
|-
|{{No|Scary volcanic eruption in North America}}
|The volcanic eruptions that deposited {{w|Deicke and Millbrig bentonite layers|layers of ash}} during the Late Ordovician were incredibly large. The volcanoes involved may have been formed during the mountain-building event in {{w|Taconic orogeny|what is now north-eastern North America}}.
|-
! rowspan="2" | {{w|Silurian}} (443⁠–⁠420)
|{{Yes|First land animals}}
|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.
|-
|{{No|Earth's newfound mold problem}}
| Mold soon evolved to attack them and decompose their remains. A "{{w|Indoor mold|mold problem}}" often refers to mold growing in damp places in a building, causing unpleasant odors and various {{w|Indoor_mold#Health_effects|negative health effects}}.
|-
! rowspan="2" | {{w|Devonian}} (420⁠–⁠359)
|{{Yes|Big mountains in Boston}}
|A section of the present-day Appalachian Range from the Canadian Maritimes to the Carolinas, including what is now the Boston area of Massachusetts, was created during this period. (At the time, Boston was in the tropics, just south of the equator.)
|-
|{{No|Yeah, sure, what those giant killer fish needed was ''armor''}}
|{{w|Placoderm}} fishes, which were common in the Devonian, had plates of {{w|dermal bone}} in the head and thoracic portions of the body. Not all placoderms were giants, or apex predators. These fishes likely had these bony plates because they helped protect them from predators.
|-
! rowspan="2" | {{w|Carboniferous}} (359⁠–⁠299)
|{{Yes|Cool forests}}
|Forests in the Carboniferous lacked the flowering plants and conifers that are common in present-day forests. Instead, forests were dominated by giant versions of today's {{w|Lycopodiaceae|club mosses}}, {{w|Equisetidae|horsetails}}, and {{w|Marattiaceae|ferns}}, as well as by several plant lineages that are now extinct. {{w|File:Meyers b15 s0272b.jpg|Artists' depictions}} of such forests are exotic-looking and considered "cool" by Randall.
|-
|{{No|Bugs too big}}
|Carboniferous '{{w|Carboniferous#Terrestrial invertebrates|bugs}}' included the largest-ever known land invertebrate, a {{w|Arthropleura|2.6 m millipede-like animal}}; the largest-ever known flying insect, resembling a {{w|Meganeura|dragonfly with a wingspan of 75 cm}}; and a {{w|Pulmonoscorpius|70 cm scorpion}}.
|-
! rowspan="2" | {{w|Permian}} (299⁠–⁠252)
|{{Yes|Pangea}}
|{{w|Pangaea}} was the most recent {{w|supercontinent}} containing nearly all of Earth's landmass.
|-
|{{No|Google "The Great Dying"}}
|{{w|Permian-Triassic extinction event|The Great Dying}} 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, 80% of marine species and 70% of terrestrial vertebrate species were wiped out.
|-)
! rowspan="2" | {{w|Triassic}} (252⁠–⁠201)
|{{Yes|Tanystropheus}}
|The ''{{w|Tanystropheus}}'' was an {{w|Archosauromorpha|Archosauromorph}} with a proportionally unusually long neck (as depicted in the comic).
|-
|{{No|Damage to Canada still visible from space at Manicouagan}}
|{{w|Manicouagan Reservoir}} is a ring-shaped lake, the remains of the crater caused by a 5 km (3 mi) asteroid hitting {{w|Quebec}}.
|-
! rowspan="2" | {{w|Jurassic}} (201⁠–⁠143)
|{{Yes|Birds}}
|The {{w|Avialae|ancestors of modern birds}} emerged during the Jurassic. Randall has repeatedly found it cool that birds are modern-day dinosaurs.
|-
|{{No|Parasitoid wasps}}
|{{w|Parasitoid wasp}}s reproduce by implanting their eggs into still-living animals, whose bodies are then eaten from the inside out by the wasp's larva. It is such a grisly process that it caused a {{w|Parasitoid wasp#In culture|crisis of faith}} among 19th-century European scholars.
|-
! rowspan="2" | {{w|Cretaceous}} (143⁠–⁠66)
|{{Yes|Raptors}}
| rowspan="2" |{{w|Raptors}}, especially {{w|Velociraptors}}, are a [[:Category:Velociraptors|trope]] within xkcd, especially in its early years. They were popularized by their appearance in the ''[[:Category:Jurassic Park|Jurassic Park]]'' film series. In the films, velociraptors are depicted as small (shorter than adult humans) bipedal scaled dinosaurs which frequently attacked and killed humans. Velociraptors and the irrational fear of being attacked by them in the modern world are a subject of several [[xkcd]] strips. Thus, "raptors" appears in both the "Favorites" and "Complaints" columns of the table.
|-
|{{No|Raptors}}
|-
! rowspan="2" | {{w|Paleogene}} (66⁠–⁠23)
|{{Yes|Pretty horseys!!!}}
|Fossils of members of the {{w|Equidae|horse family}} first appear during this period. Horses, fossil and extant, are prime examples of {{w|charismatic megafauna}} ("Pretty horseys!"). The rapid diversification of horses from a presumed single common ancestor is an oft-cited example of mammalian adaptive radiation.
|-
|{{No|Paleocene-eocene thermal maximum}}
|The {{w|Paleocene–Eocene Thermal Maximum}} was a time when the global average temperature rose by 5-8 °C in a relatively short period of time. It can be viewed as a slower version of [[:Category:Climate change|climate change, which Randall has repeatedly complained about]].
|-
! rowspan="2" | {{w|Neogene}} (23⁠–⁠2.6)
|{{Yes|Forests of ''Dracaena'' dragonblood trees}}
|''{{w|Dracaena draco}}'' and ''{{w|Dracaena cinnabari}}'' trees are a source of {{w|dragon's blood}}, a naturally occurring bright red resin used as a varnish and a dye.
|-
|{{No|Zanclean flood}}
|The {{w|Zanclean flood}} is theorized to be the flood that refilled the Mediterranean Sea.
|-
! rowspan="2" | {{w|Quaternary}} (2.6⁠–⁠present)
|{{Yes|Burrito invented}}
|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}} made food resembling burritos as early as 1500 BC.
|-
|{{No|Whoever picked the name for the third period of the Cenozoic}}
|The third period of the {{w|Cenozoic Era}} is the Quaternary ("Fourth"), named by Jules Desnoyers in 1829. Randall is riffing on the cognitive disconnect between "third" and "fourth", for which the current geological naming conventions offer no explanation.
|}

The title text expands on the complaint about the "third" <em>v</em> "fourth" discrepancy in regard to the Quaternary Period by postulating the existence of an unnamed geologic period within the Cenozoic Era "that geologists won't tell us about". In fact, the use of "Quaternary" (and "Tertiary") in recent/current geological nomenclature is a relic of four centuries of the history of geological studies in Western Europe, complicated by the religiously-inspired acceptance until the beginning of the 19th century, among European scholars, of an Earth that was only 6000 years old. "Primary" rocks were those considered to have been present in mountains before the "Great Deluge" of Noah (the {{w|Genesis flood narrative}}), while "Secondary" rocks represented the rubble from the Flood. Igneous and metamorphic rocks came to be understood as "primary", and eldest (within the context of a 6000-year-old Earth), and sedimentary rocks as "secondary". More recent geological formations came to be known as "tertiary" (relatively newer) and "quaternary" (even more recent). As the idea of Earth being billions of years old gained acceptance and we invented tools for dating rocks, "primary" and "secondary" fell away as descriptors for both rock types and rock ages, replaced by terms that convey information about the rocks more accurately. "Tertiary" was applied to "Cenozoic minus Quaternary", and survived in formal nomenclature into the 21st century. No alternative for "Quaternary" has yet been accepted, so the name persists as fodder for cartoonists who wonder, not without cause, how a "third" element in Earth history could be labeled a "fourth" element.

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

:[A table with 3 columns, labelled: "Period", "My favorite part" and "My biggest complaint". There are 13 rows below the labels]
:[Row 1: Period:] ''Precambrian'' [My favorite part:] Life develops [My biggest complaint:] Snowball Earth episodes
:[Row 2: Period:] Cambrian [My favorite part:] Trilobites! [My biggest complaint:] Evolution could stand to calm down a little
:[Row 3: Period:] Ordovician [My favorite part:] Earth might have had rings [My biggest complaint:] Scary volcanic eruption in North America
:[Row 4: Period:] Silurian [My favorite part:] First land animals [My biggest complaint:] Earth's newfound mold problem
:[Row 5: Period:] Devonian [My favorite part:] Big mountains in Boston [My biggest complaint:] Yeah, sure, what those giant killer fish needed was '''''armor'''''
:[Row 6: Period:] Carboniferous [My favorite part:] Cool forests [My biggest complaint:] Bugs too big
:[Row 7: Period:] Permian [My favorite part:] Pangea [My biggest complaint:] Google "The Great Dying"
:[Row 8: Period:] Triassic [My favorite part:] Tanystropheus [accompanying the text in this cell is an image of a ''Tanystropheus'' and its characteristic elongated neck, with Cueball standing next to it for scale] [My biggest complaint:] Damage to Canada still visible from space at Manicouagan
:[Row 9: Period:] Jurassic [My favorite part:] Birds [My biggest complaint:] Parasitoid wasps
:[Row 10: Period:] Cretaceous [My favorite part:] Raptors [My biggest complaint:] Raptors
:[Row 11: Period:] Paleogene [My favorite part:] Pretty horseys!!! [My biggest complaint:] Paleocene-eocene thermal maximum
:[Row 12: Period:] Neogene [My favorite part:] Forests of ''Dracaena'' dragonblood trees [My biggest complaint:] Zanclean flood
:[Row 13: Period:] Quaternary [My favorite part:] Burrito invented [My biggest complaint:] Whoever picked the name for the third period of the Cenozoic

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