explain xkcd - User contributions [en]

3056: RNA

2025-02-27T14:49:43Z

Bendorfm: /* Explanation */ corrected typo by adding a period just before an opening parentheses.

{{comic
| number = 3056
| date = February 26, 2025
| title = RNA
| image = rna_2x.png
| imagesize = 566x291px
| noexpand = true
| titletext = 2040s: RNA formed the basis for life each of the five known times it arose on the early Earth.
}}

==Explanation==
{{incomplete|Created by a BOT FROM RNAWORLD. EARLY EXPLANATION THIS IS A BASE![''No, {{w|Uracil|this}} is a base!''] - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This is a comic about the evolution of our understanding {{w|DNA}} and {{w|RNA}} over time as we've done more research into how they figure into cellular and virus processes. In the 1960s, we had just started to understand the role of DNA. But, as the years progress, we realized RNA played a part (initially as an intemediary), and it turned weird as we learned that RNA's role is potentially as complex as DNA's, if not more. People now believe that life as we know it developed as RNA, and then evolved proteins and DNA later, this is called the "RNA world" theory.


The first panel shows the simplified (though incorrect) version of the {{w|central dogma}}, saying that RNA's sole function is to carry information from DNA to produce proteins.

The second panel shows the discovery that RNA itself can also catalyze reactions, like in {{w|ribozymes}}.

The third panel shows the more recent discovery of many different types of RNA that have numerous functions, like {{w|small interfering RNA|siRNA}} which acts in the {{w|RNA interference}} pathway, {{w|microRNA|miRNA}} which causes regulation of transcript expression, {{w|Piwi-interacting RNA|piRNA}} which regulates {{w|transposons}} and other genetic elements, and more.

The fourth panel explains that RNA seems to be the primary actor in life, and it merely uses DNA for permanent storage of information. In particular, DNA contains the genetic information that's copied when cells divide and when ova and sperm combine.

The title text [[605: Extrapolating|extrapolates]] from the fourth panel into the 2040s, where humans have learned that RNA was responsible for the formation of life on Earth, and that life formed on Earth five times. Of course, we currently only know of one time which life formed on Earth today.

At the present time, all types of life we know of today (or have evidence of having existed) seem highly likely to have arisen from the ultimate {{w|most recent common ancestor}} of every other example. (Although it is hypothesised that Viruses {{w|Viral_evolution#Origins|may have evolved indepently of cellular life}}.) Whether this can change for the 2040s is unknown. It might take more advanced study of ancient rocks, and the sheer good fortune to uncover/discover a suitably preserved 'bed' of alternate biochemistry, to establish decent evidence of some other origin(s) of life. Another possibility is that intense analysis of the current diversity of biology ''could'' extrapolate multiple origins for some of the chemical pathways that eventually became cooperative parts in some or all more recent forms of biological cell.

RNA has been mentioned previously in [[2425: mRNA Vaccine]], where the [[:Category:COVID-19 vaccine|COVID-19 vaccine]] is explained, and [[3002: RNAWorld]], in which Disney decides to capitalize on the success of RNA.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[In each panel, Cueball is standing in front of a poster. On the poster there is a picture of a double helix (presumably DNA) and some illegible text, although the poster is different in each panel. Each panel has a header indicating the decade in which it takes place.]

:'''1960s'''
:[Cueball has a hand up in an explanatory pose]
:Cueball: Life is based on DNA, which uses RNA to make proteins do stuff.

:'''1980s'''
:[Cueball faces towards the poster, with his hand on his chin.]
:Cueball: Also, the RNA does some stuff itself, which is weird.

:'''2000s'''
:[Cueball has his arms raised in the air.]
: Cueball: There are so many types of RNA. It's doing ''so'' much stuff!

:'''2020s'''
:[Cueball has both his hands down]
:Cueball: Life is a seething mass of RNA that sometimes uses DNA to take notes.
:Person out of frame: What do the proteins do?
:Cueball: Errands for RNA.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Biology]]

3056: RNA

2025-02-27T14:48:50Z

Bendorfm: /* Explanation */ corrected typo by closing parentheses.

{{comic
| number = 3056
| date = February 26, 2025
| title = RNA
| image = rna_2x.png
| imagesize = 566x291px
| noexpand = true
| titletext = 2040s: RNA formed the basis for life each of the five known times it arose on the early Earth.
}}

==Explanation==
{{incomplete|Created by a BOT FROM RNAWORLD. EARLY EXPLANATION THIS IS A BASE![''No, {{w|Uracil|this}} is a base!''] - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This is a comic about the evolution of our understanding {{w|DNA}} and {{w|RNA}} over time as we've done more research into how they figure into cellular and virus processes. In the 1960s, we had just started to understand the role of DNA. But, as the years progress, we realized RNA played a part (initially as an intemediary), and it turned weird as we learned that RNA's role is potentially as complex as DNA's, if not more. People now believe that life as we know it developed as RNA, and then evolved proteins and DNA later, this is called the "RNA world" theory.


The first panel shows the simplified (though incorrect) version of the {{w|central dogma}}, saying that RNA's sole function is to carry information from DNA to produce proteins.

The second panel shows the discovery that RNA itself can also catalyze reactions, like in {{w|ribozymes}}.

The third panel shows the more recent discovery of many different types of RNA that have numerous functions, like {{w|small interfering RNA|siRNA}} which acts in the {{w|RNA interference}} pathway, {{w|microRNA|miRNA}} which causes regulation of transcript expression, {{w|Piwi-interacting RNA|piRNA}} which regulates {{w|transposons}} and other genetic elements, and more.

The fourth panel explains that RNA seems to be the primary actor in life, and it merely uses DNA for permanent storage of information. In particular, DNA contains the genetic information that's copied when cells divide and when ova and sperm combine.

The title text [[605: Extrapolating|extrapolates]] from the fourth panel into the 2040s, where humans have learned that RNA was responsible for the formation of life on Earth, and that life formed on Earth five times. Of course, we currently only know of one time which life formed on Earth today.

At the present time, all types of life we know of today (or have evidence of having existed) seem highly likely to have arisen from the ultimate {{w|most recent common ancestor}} of every other example (Although it is hypothesised that Viruses {{w|Viral_evolution#Origins|may have evolved indepently of cellular life}}.) Whether this can change for the 2040s is unknown. It might take more advanced study of ancient rocks, and the sheer good fortune to uncover/discover a suitably preserved 'bed' of alternate biochemistry, to establish decent evidence of some other origin(s) of life. Another possibility is that intense analysis of the current diversity of biology ''could'' extrapolate multiple origins for some of the chemical pathways that eventually became cooperative parts in some or all more recent forms of biological cell.

RNA has been mentioned previously in [[2425: mRNA Vaccine]], where the [[:Category:COVID-19 vaccine|COVID-19 vaccine]] is explained, and [[3002: RNAWorld]], in which Disney decides to capitalize on the success of RNA.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[In each panel, Cueball is standing in front of a poster. On the poster there is a picture of a double helix (presumably DNA) and some illegible text, although the poster is different in each panel. Each panel has a header indicating the decade in which it takes place.]

:'''1960s'''
:[Cueball has a hand up in an explanatory pose]
:Cueball: Life is based on DNA, which uses RNA to make proteins do stuff.

:'''1980s'''
:[Cueball faces towards the poster, with his hand on his chin.]
:Cueball: Also, the RNA does some stuff itself, which is weird.

:'''2000s'''
:[Cueball has his arms raised in the air.]
: Cueball: There are so many types of RNA. It's doing ''so'' much stuff!

:'''2020s'''
:[Cueball has both his hands down]
:Cueball: Life is a seething mass of RNA that sometimes uses DNA to take notes.
:Person out of frame: What do the proteins do?
:Cueball: Errands for RNA.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Biology]]

2961: CrowdStrike

2024-07-22T13:13:26Z

Bendorfm: /* Ponytail is kneeling, not sitting */

{{comic
| number = 2961
| date = July 19, 2024
| title = CrowdStrike
| image = crowdstrike_2x.png
| imagesize = 322x384px
| noexpand = true
| titletext = We were going to try swordfighting, but all my compiling is on hold.
}}

==Explanation==
{{incomplete|Created by an UNAFFECTED BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic is about the {{w|2024 CrowdStrike incident}} occurring on the day of the comic's release. CrowdStrike makes security software to protect computers from malware, ransomware and other cyberattacks. The software is sold to businesses and large enterprises like hospitals, airlines and retailers. CrowdStrike frequently releases updates to their software to handle new types of malware they know about. A faulty update for one of their software products, which was apparently released without adequate testing or {{w|quality assurance}}, caused computers with the software installed to crash (a {{w|Blue Screen of Death}}) very early on when booting up. This meant the computers could not be quickly or automatically fixed. Because many large businesses with large numbers of computers used CrowdStrike's software on at least some of their systems, or relied upon businesses that did, the resulting disruption was very widespread and very visible, preventing those businesses from operating and, in many cases, preventing their employees from working while their computers were affected.

Apparently, Cueball and Ponytail's company, or possibly a company providing a service their work depends on, uses CrowdStrike to secure their computers (although they may just be using it as an excuse to slack off, if their colleagues don't know any better). Without being able to work, they have found something more entertaining to do -- Cueball, riding a scooter and with a rope tied around his waist, is towing Ponytail, who is kneeling on a swiveling chair, around their office or neighborhood. Performing this activity is probably a bad idea.{{cn}}

As the caption suggests, not everyone has the luxury of slacking off while their computers are broken. CrowdStrike engineers had to address the faulty update, and help the businesses using their software to fix their computers. And relevant employees at affected customers' IT departments had to work to mitigate the impacts, and to roll out the necessary fixes. In the event, CrowdStrike had released a patch for the software around six hours after it came to light, but this had to be manually applied to each affected device.

The title text refers to [[303: Compiling]], in which Cueball also found an alternative way to spend time at work when 'forced' to step away from his computer, albeit for a less disruptive reason. But, because of ''this'' problem, even the compiling is on hold. If sword fighting is 'officially allowed' only during actual compiling, as that comic implied, then during this instance (forced to be {{w|Glossary of video game terms#AFK|AFK}} for different reasons) they must resort to yet ''other'' activities, such as the one in this comic.

==Transcript==
:[White Hat is pointing his finger at Ponytail and Cueball. Ponytail is crouched on a moving office chair, holding with both hands onto a rope tied around the waist of Cueball, who is riding an electric scooter.]
:White Hat: Hey, aren't you supposed to be working on the—
:Ponytail: Sorry, that's all on hold today because of the CrowdStrike thing.

:[Caption below the panel:]
:Protip: As long as you're not actually in charge of '''''fixing''''' the CrowdStrike thing, you can use this excuse for pretty much anything you want to do today.

{{comic discussion}}

[[Category:Protip]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Cueball]]
[[Category:Computer security]]

2710: Hydropower Breakthrough

2022-12-13T15:06:21Z

Bendorfm: Added announcement link

{{comic
| number = 2710
| date = December 12, 2022
| title = Hydropower Breakthrough
| image = hydropower_breakthrough_2x.png
| imagesize = 261x303px
| noexpand = true
| titletext = A hydroelectric dam is also known as a heavy water reactor.
}}

==Explanation==
{{incomplete|Created by a PRACTICAL WATER REACTOR - Needs another citation for the anouncment since the one that was present required a subscription to a paper! Do NOT delete this tag until the year 2039, or until fusion reactors have succeeded.}}
The comic parodies fusion reactors, with energy produced seemingly never positive. In the past years, constant developments in fusion reactors have slowly increased the energy output of fusion to more than the input. It is possible this is meant to directly parody the Department of Energy's anticipated announcement of Q>1 fusion. The announcement is scheduled for the day after this comics release, and [https://www.washingtonpost.com/business/2022/12/11/fusion-nuclear-energy-breakthrough/ the date of this announcement was announced the day this comic went up.]

A {{w|hydroelectric dam}} is a power facility that generates electricity from water flowing in a river passing through a water turbine and generator. In the comic, [[Beret Guy]], unscientific as always, presents a hydroelectric dam. However, instead of generating energy, it generates a flow of water. This is similar to the way that a fusion reactor takes energy (and hydrogen isotopes) as an input and energy (and helium isotopes) as outputs. While one member of the audience shouts "Hooray!", another member of audience, who is presumably familiar with regular physics, says "Wait.", presumably because they realise that, instead of the normal approach, Beret Guy has been pursuing the essentially useless goal of producing more water (or possibly because they're confused that, on the face of it, it appears to be violating {{w|conservation of mass}}, which would usually require that a dam should produce the same amount of water as that fed into it - that said, for a regular dam in a natural valley like the one shown in this comic, it is entirely normal for the dam to "produce" more water than input in the sense that in addition to water from upstream rivers, the dam will also output any "unofficial" inflow from direct rainfall above and from uncharted sources of groundwater below).

The symbol Q is normally used to refer to {{w|fusion energy gain factor}}, the ratio of power generated by a fusion reactor to the energy used to maintain it. An energy source isn't useful if it takes more power to run it than it produces, so Q > 1 means the reactor is producing net energy. Q also can represent the volumetric flow rate of water through a hydroelectric dam, and in this case, a Q > 1 would have no great significance. Beret Guy has somehow mixed the two up, making the rate of flow as the output of the reaction and increasing it.

The title text further confuses the issue as it introduces nuclear ''fission'' and equates the hydroelectric dam with a heavy water reactor, which is a special type of nuclear fission reactor that uses deuterium (heavy water) as a moderator to absorb neutrons. This is also a pun because one could simplistically say that a hydroelectric dam runs on the weight of water (potential energy stored in the water: U = mgh), or that it is a water reactor (producing electricity) that is heavy (bulky). While a hydroelectric power plant is not actually a reactor, it would have to be using a reaction (such as 2H2 + O2 -> 2H2O) to create water to satisfy Beret Guy's statement that more water is produced than fed into the dam, while simultaneously satisfying the law of conservation of mass. Alongside that, the title text is possibly making a pun on water and fusion reactors. Heavy water is the primary source of deuterium, a specific isotope of hydrogen required for the most energy-efficient fusion reactions needed today. On the other hand, water is the liquid that passes through dams, and is rarely used for fusion reactions today — although [https://what-if.xkcd.com/14/ it could be used as fusion fuel because it is made of hydrogen and oxygen.]

==Transcript==
:[Beret Guy is standing on a podium behind a lectern. He is gesturing with his hand, palm up, towards a poster hanging behind him. On it is a picture of a tall dam, with a lake behind, and water coming out at the foot of the dam in the valley on the other side. Two voices reacts to Beret Guy's statement from off-panel.]
:Beret Guy: We are pleased to announce that our hydroelectric dam has achieved Q>1, producing more water than we fed into it!
:Off-panel voice 1: Hooray!
:Off-panel voice 2: Wait.

{{comic discussion}}

[[Category:Comics featuring Beret Guy]]
[[Category:Strange powers of Beret Guy]]
[[Category:Public speaking]]
[[Category:Physics]]

2626: d65536

2022-06-01T14:33:47Z

Bendorfm: corrected typo

{{comic
| number = 2626
| date = May 30, 2022
| title = d65536
| image = d65536.png
| titletext = They're robust against quantum attacks because it's hard to make a quantum system that large
}}

==Explanation==
{{incomplete|Created by a HEXAKISMYRIAPENTAKISCHILIAPENTAHECTATRIACONTAKAIHEXAHEDRON - The claim in the trivia that the numbers refer to a comic, should be substantiated with an explanation. If true interesting, if not... Do NOT delete this tag too soon.}}
In binary computing, 16 bit numbers range from 0 to 65535, for a total of 65536 unique numbers, a number which is hence well-known to software engineers. Generating large numbers in a manner that is truly random is a recurring problem in cryptography, required to send private messages to another party. People today still use dierolls to generate private random numbers.

In role-playing games (and occasionally in other tabletop games), multiple shapes of dice are often used to generate random numbers in specific ranges. By convention, these are referred to as d''n'' according to their number of faces. A traditional six-faced die would be a d6, and many popular pen-and-paper role-playing games use dice ranging between d4 and d20. While there are larger dice used in tabletop games (most commonly d100), these are usually split into multiple smaller ones. For example, a d100 is often two d10s rolled together, with one die providing the first digit and the other die giving the second digit — the total number of possible combinations (100) is the product of the number of faces of the two dice (10 * 10). While "real" {{w|Zocchihedron|d100s}} and other large-numbered dice do exist, most people consider them to be impractical: they need to be either impractically large or have very small faces (resulting in small print for the numbers), they're close enough to being spheres that it's difficult to get them into a stable resting position, and even if they are stationary, determining which face is "on top" is difficult to do by eye. The Zocchihedron (d100) die is also biased because of geometry requiring different sized faces, the next unbiased die is a d120, it is very likely that [[Cueball|Cueball's]] d65536 die is also biased.

Here, Cueball has constructed a d65536 for generating random 16 bit numbers. It may have solved the problem of generating large random numbers with fewer die rolls, but it magnifies all of the problems with large-numbered dice to ludicrous extremes. In order for the faces to be readable, the die is ridiculously huge, dwarfing the human standing next to it. Rolling such a die is not only physically challenging, but it would also need a huge space in which to roll if the result is to be random, and that space would need to have an extremely flat and rigid surface in order for the die to come to rest. And even in those problems were solved, simply getting to a vantage point to see the top of the die would be a major challenge, and determining which number was truly on top would be near impossible to do by eye. If one really wished to use dice, it would be much easier to simply use multiple dice rolls. For instance, one could roll eight d4 dice (or use 16 coin flips), and convert the result into binary. Generating pseudorandom numbers is relatively easy, using the kind of die depicted in the comic would not be.

The closest regular shape similar to the depicted in the comic could be a {{w|Goldberg polyhedron}}. However, no such polyhedron exists with exactly 65536 hexagonal faces. The closest Goldberg Polyhedron has a mixture of 65520 hexagons and 12 pentagons, totaling 65532 faces. It is possible to construct a fair die without a matching regular shape by limiting the sides which it could land on and designing those sides to be fair (for instance, a prism with rectangular facets that extend its entire length, and rounded ends to ensure it doesn't balance on end).

The title text references how many cryptographic systems (especially RSA and other factoring-is-hard based systems) are vulnerable to quantum attacks as quantum computing technology develops. The title text is essentially punning on the idea of a "large" quantum system. "Large" in the quantum computing sense would be on the order of 64 qubits each of which would be an atom or two at most. This would still be microscopic and will never be as large as the giant die the comic is centered on; but for a well-observed environment and human rolling without sufficient entropy (consider somebody obsessed with a certain number dropping the die on something soft), a conventional computer could predict some rolls. See also [[538]] for non-mathematical paths of cryptography.

==Transcript==
:[A large sphere with a several lines, and in some places grids, are shown. Cueball, standing next to it, is dwarfed by its size, as it is at least seven times as tall as he is. The sphere has many lines following various great circles or parallel lesser circles around the curve of the sphere, and some patches of cross hatching to suggest further texturing along these lines hovering just below the degree of most of the illustrative detailing. In the top right part of the ball is a black circle. An arrow points to this circle, and the end of the arrow goes to a larger circle that partly obscures the rightmost part of the sphere. The circle shows a zoom in on the surface in the black circle on the sphere. The zoom shows a small portion of the spheres surface, showing that the grid comes along because the sphere is divided into elongated hexagonal faces with numbers up to at least five-digits. Seven numbers can be fully seen, but there are nine other faces partly shown, five of these with part of their numbers visible, one of these clearly only have four digits. One of the empty faces must also have a number with only 1-3 digits, as no numbers are visible although a significant part of the face is visible.]

:[Here follows the numbers in the zoomed in part of the sphere, with "..." represents numbers being cut off. The numbers are read in lines left to right, even though the numbers are tilted from down towards the right, which could have suggested a different reading order.]
:30827
:16[bottom part of a cut-off line][small cut-off circle]
:...38
:11875
:25444
:...[top part of a cut-off line]5
:12082
:28525
:3 [left part of a cut-off line]...
:13359
:13874
:[Two cut-off lines, likely the start of the number 2]...

:[Caption below the image:]
:The hardest part of securely generating random 16-bit numbers is rolling the d65536.

==Trivia==
*If a real d65536 were constructed with each number having an equal area and each printed in 12 point font, the resulting die would be about 5 feet (1.5 meters) in diameter, which isn't several times the size of a person as the comic suggests, but is still large enough to be hilariously inconvenient. If it were made out of standard acrylic, and not hollow, it would weigh about 2 tons (1700kg).
*This die would have a 0.00001526 chance of rolling a natural one (or any other number).
*There are seven 16-bit numbers fully visible in the picture: 30827, 25444, 11875, 28525, 12082, 13874 and 13359. They conceal a message. If these numbers are split big-endian into two 8-bit ASCII characters each, the result is <code>xkcd.com/2624/</code>{{citation needed}}.

{{comic discussion}}

[[Category:Cryptography]]
[[Category:Comics featuring Cueball]]

2495: Universal Seat Belt

2021-07-29T13:17:05Z

Bendorfm: /* Explanation */

{{comic
| number = 2495
| date = July 28, 2021
| title = Universal Seat Belt
| image = universal_seat_belt.png
| titletext = The plug fits really snugly, so it should be safe in a crash.
}}

==Explanation==
{{incomplete|Created by a USB PORT. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This became the second installment in the new series of [[:Category:Cursed Connectors|Cursed Connectors]] which began two comics earlier with [[2493: Dual USB-C]].

The comic shows another of [[Randall|Randall's]] "Cursed Connectors", this time #65 the "Universal {{w|Seat belt|Seat Belt}}", a pun on the Universal Serial Bus ({{w|USB}}) connector.

USB connectors are mostly designed for free and unrestricted insertion and removal. There may be a slight use of the internal and external bumps and dimples to provide a tactile indication of being engaged or disengaged, but there are usually no facilities to prevent a connector being easily pulled out of even a port being actively used - the OS can do no more than complain that a device has been removed without first ensuring proper logical unmapping of the resource (which in turn may have to await a current session of data transfer being completed or aborted) or warn that a "delayed write" has failed.

Car seat-buckles, on the other hand, have very definite requirements to not come loose ''unless'' intentionally and mechanically released, in order to keep the passenger safely anchored to the seat.

The title text claims that the seat belt is secure in the case of a crash. This is another pun, as seat belts protect passengers in a car crash while USB ports are rated to protect devices in the event of a computer malfunction ("crash").

Another similarity between seat-belts (especially on back seats) and USB-plugs is that they can be a bit fiddly to insert. A seat-belt lock with the asymmetric design of a USB-A plug would be even more fiddly and thus "cursed".

One possible use for the USB data connector might be to give a certain degree of 'proof' that the belt is plugged in, although that functionality is fairly well covered by current anchor-point sensors that (combined with seat-occupancy sensors that may respond to the weight of a seated person) can trigger dashboard lights and possibly warning sounds in vehicles as necessary to prompt correct usage of restraining belts. That system does not usually need an electronic data connection between anchor and belt, an anchor-side switch should suffice, and it would still require a mechanical gripping/hooking method to make it of any use to be engaged in the first place.

==Transcript==
:[The two ends of a seatbelt are shown next to each other, but the seatbelt connectors are replaced with a USB-A plug and port. Above is a title and below is a label.]
:Cursed Connectors #65
:the Universal Seat Belt

{{comic discussion}}

[[Category:Cursed Connectors]]

2336: Campfire Habitable Zone

2020-07-23T13:04:02Z

Bendorfm: /* perhaps shivering cold herself */

{{comic
| number = 2336
| date = July 22, 2020
| title = Campfire Habitable Zone
| image = campfire_habitable_zone.png
| titletext = Oh no, my marshmallow became tidally locked!
}}

{{incomplete|Created by a FIRE-PROOF ORBITING SMORE-MAKING ROBOT. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

==Explanation==
This comic plays on the concept of the astronomic "habitable zone" applied at the scale of people sitting around a campfire.

The {{w|Circumstellar habitable zone|habitable zone}} for a star (also known as the "Goldilocks Zone") is the range of distances in which a planet might support liquid water, and hence life in the only form that we currently know of. Too close, and the amount of stellar radiation would be too great, causing water to boil. Too far, and the water would freeze. For liquid water to actually exist, the planet itself must also have the right mass (in order to maintain a life-compatible atmosphere) and meet other requirements. For our sun, the habitable zone is estimated to range from about 0.38 to 10 astronomical units, where 1.0 is the distance from the sun to the Earth.

{{w|Marshmallow#Toasted_marshmallows|Marshmallow toasting}} is a popular camping activity in which people place a marshmallow (a soft, sugary blob made of gelatin and covered in corn starch) on a stick near a fire. As it cooks, the middle becomes gooey while the outside becomes crispy and perhaps slightly charred, making it tastier.

In the context of the campfire, a similar "habitable zone" is posited to exist: close enough to the fire that the person can comfortably toast marshmallows, presumably on a stick of reasonable length - the ones shown seem to be about 1.5 times an arm's normal reach; yet far enough that the person is not uncomfortably hot, or even burnt by the flames.

In the comic, Ponytail is sitting in the left habitable zone (marked in green), and appears to be enjoyably toasting a marshmallow. Cueball is sitting half outside the right habitable zone, too close to the fire, and appears to be getting singed on his arm, which is too close to the fire. Megan is well outside the habitable zone on the right cool side. She is waving a marshmallow on a stick, perhaps shivering cold herself, but presumably it will not toast, as it is too far from the fire, even further from the fire than Cueball.

The title text introduces the concept of {{w|tidal locking}}. This is when one astronomical body synchronises its rotation with its orbit around another, such that one side always faces the other body. The joke here is that if a marshmallow became tidally locked to the fire, then one side would become more and more cooked, perhaps burnt, while the other side never became toasted at all. This happens in real life, as in the case of Earth's moon, which always presents the same face to the Earth; and also in the case of a marshmallow that has begun melting more than you realised and dripped down too far, so that it no longer responds when you rotate the roasting stick, and you'd better cut your losses and pull it out now before it drops into the fire pit.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The scene consists of 3 people sitting near a campfire with two green areas to the left and right of the fire. Ponytail is sitting to the left of the fire, with her body fully in the green habitable zone and is holding a stick with a marshmallow pointed at the fire. Cueball is sitting to the right of the fire, half sitting in the white area where the fire is and half in the green habitable zone. He is visibly sweating. Megan is crouching to the right of Cueball, outside the habitable zone with a marshmallow on a stick pointing into the green zone. Below the scene two arrows point to the two green areas marked with a label.]
:Label: Habitable zone

:[Caption below panel:]
:Astronomers define the Campfire Habitable Zone as the region where you're far enough not to be burned but close enough to roast marshmallows.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics with color]]
[[Category:Astronomy]]
[[Category:Food]]