explain xkcd - User contributions [en]

2804: Marshmallow

2023-07-21T21:11:34Z

Shadowfax37: Spelling error

{{comic
| number = 2804
| date = July 19, 2023
| title = Marshmallow
| image = marshmallow_2x.png
| imagesize = 670x334px
| noexpand = true
| titletext = The increasing number of graham crackers and chocolate bars in orbit has created a growing risk of Kessler s'mores.
}}

==Explanation==
{{incomplete|Created by a CELESTIAL S'MORE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
This comic shows the atmospheric re-entry process of a capsule similar to that used in the Apollo moon landing program in the late 1960s and early 1970s. This capsule features a fictional Reentry Marshmallow Toasting Module, with a marshmallow on a deployable stick, which is exposed to airflow during reentry.

During reentry, the capsule would presumably be going at orbital speeds, which for Earth are in excess of 8 km/s. This high velocity heats up the air around the capsule as the kinetic energy is dissipated.{{Actual citation needed}} This has the effect of heating the marshmallow. Additionally, reentry heating effects typically look like flames covering the bottom of the reentering object. This is very similar to a common practice on the Earth's surface of holding a marshmallow on a stick over a static fire on the ground, like a campfire, which also heats the marshmallow, improving its taste.

At the start of the panel, the capsule is approaching atmospheric entry, so any aerodynamic forces would not have begun yet. "All systems nominal" is an aerospace phrase that means all systems (including life support, navigation and stability systems) are performing as expected. However, once the atmospheric effects begin then something goes wrong.

Having a long, thin extension to the airflow will disrupt the aerodynamics, as air starts pushing up against the roasting stick, creating an unbalanced torque that pushes the marshmallow further back into the airflow, rotating the entire capsule. This angular acceleration continues until the aerodynamic design of the rest of the capsule plays a significant factor, rotating the capsule back to its original position, and starting the uncontrollable cycle of oscillations anew. Hence, the astronaut on board reports some oscillations to Houston.

This prompts the unnamed astronaut to tell their colleague, Smith, to put away the marshmallow roaster. This would clean up the aerodynamic profile and stop the oscillation. This is met with resistance that the marshmallow is not cooked yet. This may be expected, as due to the design of the module, it appears as though the marshmallow has been on the outside of the capsule for the entire journey, exposed to the vacuum of space. In this situation, it would have radiated all its heat energy away, reaching temperatures near absolute zero (approximately -273.15 degrees Celsius, the absolute coldest temperature physically achievable). A very brief moment of shock heating from atmospheric effects may not have bought the marshmallow up to a consumable temperature, or even affected the internals of the marshmallow at all. The goal of roasting marshmallows is often to melt the inside of a marshmallow completely, so if this is still frozen, that defeats the entire purpose of the module.

"Houston" is the radio {{w|callsign}} for {{w|Christopher C. Kraft Jr. Mission Control Center|NASA Mission Control}}, located in Houston, Texas. During reentry, the superheated air forms a plasma phase and disrupts radio signals. Hence, it is doubtful that Mission Control would have received this communication from the capsule, and it is very unlikely Mission Control would have received further updates from the capsule until the reentry process was largely finished. This would make the Mission Control operators very concerned over the success of the reentry. But as orbital mechanic and spaceman extraordinaire {{w|Scott Manley}} has discussed the feasibility of [https://www.youtube.com/watch?v=Zwf0RWXx8BY roasting a turkey by dropping it from space] (and Randall has himself addressed the issue of {{what if|28|cooking steaks}}), the astronauts featured in this cartoon are not straying too far from accepted marshmallow roasting techniques and should not be reprimanded by NASA.

The caption for the panel muses that maybe the concept of the module was a mistake, which is a fair assessment given the number of flaws in the design. It would indeed be far better to have ''two'' such units, set upon opposing sides of the module and operated in conjunction, to balance rotational forces. Or even three of them, set 120° apart from each other, perhaps automatically and independently actuated to tune out all ''other'' undesired aerodynamic effects – with the added advantage of simultaneously preparing snacks for all three of the astronauts that typically inhabit an Apollo capsule, not just Smith. However, if there is no way to retrieve the marshmallows without exiting the capsule, they would likely be somewhat salty and waterlogged after the time the capsule splashes down and the astronauts can "enjoy" their cooking.

The title text refers to a popular snack of {{w|S'more|s'mores}}, made by placing a marshmallow roasted over a fire with some chocolate between two crackers, similar to a sandwich. It also refers to a problem in rocketry, known as {{w|Kessler syndrome}}. Kessler syndrome is a scenario where the density of {{w|Low Earth orbit#Space_debris|space junk in low Earth orbit}} is so high that pieces of space junk crash into each other, breaking apart into smaller pieces. This increases the amount of space junk in orbit, setting off a cascade that could render low earth orbit unusable. These two concepts are combined in a ridiculous way, whereby instead of space junk, it is Graham crackers and chocolate bars that are polluting space. These, combined with the marshmallow from the toasting module, would create celestial s'mores, a novel and frankly wacky concept, as the United States space program does not primarily consist of chocolate and Graham crackers.{{Citation needed}}

==Transcript==
:[A space capsule beginning reentry into Earth's atmosphere is shown. There are four versions of this as it moves deeper and deeper into the atmosphere, but shown in a single panel.]

:[The first version is shown to the left with just a bit air resistance shown with thin dotted lines around and behind it. The capsule looks pretty standard with the broad bottom with the heat shield pointing forwards, and the capsule above it narrowing in a pyramid shape. There are a circular shapes (windows?) and some other lines indicating either doors or access panels. The one special feature is on the left, a stick is held back along the edge of the capsule from a extrusion near the bottom of the capsule. At the top of the stick a white square is located. From inside the capsule one of the unseen astronauts is speaking, possibly with ground control. All speech texts are located in rectangular frames with jagged arrows pointing towards the capsule.]
:Astronaut voice: We're approaching atmospheric entry.
:Astronaut voice: All systems nominal.

:[In the second version air resistance has increased a lot, with many more and thicker lines indicating the air resistance. At this point the arm with the white square turns on its pivot so it is now sticking straight out from the capsule far outside the heat shield below. Two lines indicate the circular movement and the release of the stick makes a loud noise:]
:''Fwip''

:[In the third version air resistance continues to increase, but now also the stick and particular the white square at the end begins to heat up, smoke coming of from the white square. Two small lines on either side of the top of the capsule indicates it is shaking.]

:[In the forth version the air resistance is about the same, but there are now six larger lines at the top of the capsule, two on either side and two above indicating more violent shaking of the capsule. The white square on the stick seems to be burning.]
:Astronaut voice: Houston, we're experiencing some oscillations. Vehicle is becoming difficult to control.
:Astronaut voice: Smith, retract that stupid arm.
:Astronaut Smith's voice: No! It's not ready yet!

:[Caption below the panel:]
:In retrospect, the reentry marshmallow toasting module was a mistake.

{{comic discussion}}

[[Category:Space]]
[[Category:Food]]

2608: Family Reunion

2022-04-21T16:50:38Z

Shadowfax37: Typos I think

{{comic
| number = 2608
| date = April 18, 2022
| title = Family Reunion
| image = family_reunion.png
| titletext = Grandma says that because of differences in primate and feline lifespans, the cat is actually my 17,000,000th cousin 14,000,000 times removed.
}}

==Explanation==
{{incomplete|Created by THE GIRL YOU DIDN'T KNOW WAS YOUR RELATIVE (WHOOPS) - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

Because all humans are descended from a {{w|Mitochondrial Eve|common ancestor}}, every human is, at some point, related to every other human, albeit distantly. Similarly, all life forms on Earth are presumed (with good reasons) to be descended from a single {{w|Most recent common ancestor|even more distant relative}} whose ultimate lineage {{w|Last universal common ancestor|became more relevant}} than any from its own 'cousins' at the time, and thus ''all'' life forms are distantly related. This makes every interaction with another life-form, technically, a family reunion, if not in the traditional sense.

The general English definition of a {{w|cousin}}, which is a person sharing an ancestor who is not a direct parent of either party, can be qualified by two numbers. There is the ''n''th-ness of the relationship (the fewest generations you need to go beyond one's parentage, "a first cousin" implies that a grandparent is the key link) - for example, [[Cueball|this Cueball's]] relation to [[White Hat]] is via a great-grandparent, whilst that with [[Hairbun]] is through a great-great-great-great-great-great-great-great-grandparent. A "removed" number is any difference in this number between the two individuals, such that a child of a direct cousin invokes a "once removed" relationship between the two (without individually qualifying who is the 'senior' generation, from whom the 'nth' count is determined). You would normally only qualify "first cousin" if this fact is considered important, and "zero times removed" would also be considered implicit.

As pointed out in the title text, cat lifespans (or, more importantly, inter-generational breeding cycles) are somewhat different from those of humans. Although they would have still been very similar immediately after the divergence from the appropriate MRCA, the differences will have built up to a generational-count displacement of a similarly extreme nature. i.e. that while the shared ancestor is Cueball's 17-million-or-so-Great Grandparent, the cat is in turn the 31-million-or-so-Great Grandchild. Exactly how accurate, or even precise, Randall considers these numbers is unknown, but it is the kind of fact that we know he likes to research and use expert opinion for.

According to [https://www.quora.com/How-many-generations-of-human-beings-recognizably-the-same-as-us-have-there-been this Quora page], there have been about 13,000 generations of modern humans, so the people at this party would be quite closely related, all things considered.

[https://www.evogeneao.com/en/learn/tree-of-life The Evogeneao Tree of Life diagram] indicates that humans and cats diverged around 90 million years ago and humans and plants diverged around 1.8 billion years ago.

If we presume that generations of humans (including proto-humans, pre-humans, etc) since the divergence from cathood (including proto-cats, pre-cats, and the rest, back to the common ancestral form) have averaged around 5 years, then a 17 millionth cousin may be about right. Many of our (and cats') early ancestors will have necessarily been small burrowing mammals — to have been amongst the ones who survived the asteroid around 66 million years ago that killed off most of the dinosaurs — with contemporary equivalents having breeding cycles in terms of a year at the most. But we currently have a large feasible range of generational cycle (15-50 years, ''very'' roughly, with or without technical/social help or hinderances), that may have started to drag our long-term average upwards since at least the age of the early hominids, if not the age of our primate forebears or earlier.

To get a 50 billionth cousin from the potted plant, then the generations of (eventually) humans since we were of the same form as that time's ancestral plants (or vice-versa) would need to average two weeks. This is possible, but difficult to be precise about due to the lack of much of the required evidence in the known fossilized remains.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon. Like seriously, don't}}

:[Megan, White Hat, Cueball, Hairy, Danish, a cat, Hairbun, a chair, and a potted plant on a cabinet are "standing" in a line. White Hat is holding a cup and Hairy has his hands to the side. There are arrows pointing to each of the living creatures.]

:14th cousin [Megan]
:2nd cousin [White Hat]
:Me [Cueball]
:12th cousin [Hairy]
:35th cousin [Danish]
:17,000,000th cousin [cat]
:9th cousin [Hairbun]
:50,000,000,000th cousin [potted plant]

:[Caption below the panel:]
:Really, ''every'' gathering is a family reunion.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]

[[Category:Comics featuring Hairbun]]
[[Category:Cats]]
[[Category:Biology]]

2608: Family Reunion

2022-04-21T16:49:31Z

Shadowfax37: Typo

{{comic
| number = 2608
| date = April 18, 2022
| title = Family Reunion
| image = family_reunion.png
| titletext = Grandma says that because of differences in primate and feline lifespans, the cat is actually my 17,000,000th cousin 14,000,000 times removed.
}}

==Explanation==
{{incomplete|Created by THE GIRL YOU DIDN'T KNOW WAS YOUR RELATIVE (WHOOPS) - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

Because all humans are descended from a {{w|Mitochondrial Eve|common ancestor}}, every human is, at some point, related to every other human, albeit distantly. Similarly, all life forms on Earth are presumed (with good reasons) to be descended from a single {{w|Most recent common ancestor|even more distant relative}} whose ultimate lineage {{w|Last universal common ancestor|became more relevant}} than any from its own 'cousins' at the time, and thus ''all'' life forms are distantly related. This makes every interaction with another life-form, technically, a family reunion, if not in the traditional sense.

The general English definition of a {{w|cousin}}, which is a person sharing an ancestor who is not a direct parent of either party, can be qualified by two numbers. There is the ''n''th-ness of the relationship (the fewest generations you need to go beyond one's parentage, "a first cousin" implies that a grandparent is the key link) - for example, [[Cueball|this Cueball's]] relation to [[White Hat]] is via a great-grandparent, whilst that with [[Hairbun]] is through a great-great-great-great-great-great-great-great-grandparent. A "removed" number is any difference in this number between the two individuals, such that a child of a direct cousin invokes a "once removed" relationship between the two (without individually qualifying who is the 'senior' generation, from whom the 'nth' count is determined). You would normally only qualify "first cousin" if this fact is considered important, and "zero times removed" would also be considered implicit.

As pointed out in the title text, cat lifespans (or, more importantly, inter-generational breeding cycles) are somewhat different from those of humans. Although they would have still been very similar immediately after the divergence from the appropriate MRCA, the differences will have built up to a generational-count displacement of a similarly extreme nature. i.e. that while the shared ancestor is Cueball's 17-million-or-so-Great Grandparent, the cat is in turn the 31-million-or-so-Great Grandchild. Exactly how accurate, or even precise, Randall considers these numbers is unknown, but it is the kind of fact that we know he likes to research and use expert opinion for.

According to [https://www.quora.com/How-many-generations-of-human-beings-recognizably-the-same-as-us-have-there-been this Quora page], there have been about 13,000 generations of modern humans, so the people at this party would be quite closely related, all things considered.

[https://www.evogeneao.com/en/learn/tree-of-life The Evogeneao Tree of Life diagram] indicates that humans and cats diverged around 90 million years ago and humans and plants diverged around 1.8 billion years ago.

If we presume that generations of humans (including proto-humans, pre-humans, etc) since the divergence from cathood (including proto-cats, pre-cats, and the rest, back to the common ancestral form) have averaged around 5 years, then a 17 millionth cousin may be about right. Many of our (and cats') early ancestors will have necessarily been small burrowing mammals — to have been amongst the ones who survived the asteroid around 66 million years ago that killed off most of the dinosaurs — with contemporary equivalents having breeding cycles in terms of a year at the most. But we currently have a large feasible range of generational cycle (15-50 years, ''very'' roughly, with or without technical/social help or hinderances), that may have started to drag our long-term average upwards since at least the age of the early hominids, if not the age of our primate forebears or earlier.

To get a 50 billionth cousin from the potted plant, then the generations of (eventually) humans since we were of the same form as that time's ancestrial plants (or vice-versa) would need to average two weeks. This is possible, but difficult to be precise about due to the lack of much of the required evidence in the known fossilised remains.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon. Like seriously, don't}}

:[Megan, White Hat, Cueball, Hairy, Danish, a cat, Hairbun, a chair, and a potted plant on a cabinet are "standing" in a line. White Hat is holding a cup and Hairy has his hands to the side. There are arrows pointing to each of the living creatures.]

:14th cousin [Megan]
:2nd cousin [White Hat]
:Me [Cueball]
:12th cousin [Hairy]
:35th cousin [Danish]
:17,000,000th cousin [cat]
:9th cousin [Hairbun]
:50,000,000,000th cousin [potted plant]

:[Caption below the panel:]
:Really, ''every'' gathering is a family reunion.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]

[[Category:Comics featuring Hairbun]]
[[Category:Cats]]
[[Category:Biology]]

2608: Family Reunion

2022-04-20T02:50:01Z

Shadowfax37: Adding some analysis of the numbers included

{{comic
| number = 2608
| date = April 18, 2022
| title = Family Reunion
| image = family_reunion.png
| titletext = Grandma says that because of differences in primate and feline lifespans, the cat is actually my 17,000,000th cousin 14,000,000 times removed.
}}

==Explanation==
{{incomplete|Created by THE GIRL YOU DIDN'T KNOW WAS YOUR RELATIVE (WHOOPS) - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

Because all humans are descended from a {{w|Mitochondrial Eve|common ancestor}}, every human is, at some point, related to every other human, albeit distantly. Similarly, all life forms on Earth are presumed (with good reasons) to be descended from a single {{w|Most recent common ancestor|even more distant relative}} whose ultimate lineage {{w|Last universal common ancestor|became more relevant}} than any from its own 'cousins' at the time, and thus ''all'' life forms are distantly related. This makes every interaction with another life-form, technically, a family reunion, if not in the traditional sense.

The general English definition of a {{w|cousin}}, which is a person sharing an ancestor who is not a direct parent of either party, can be qualified by two numbers. There is the ''n''th-ness of the relationship (the fewest generations you need to go beyond one's parentage, "a first cousin" implies that a grandparent is the key link) - for example, [[Cueball|this Cueball's]] relation to [[White Hat]] is via a great-grandparent, whilst that with [[Hairbun]] is through a great-great-great-great-great-great-great-great-grandparent. A "removed" number is any difference in this number between the two individuals, such that a child of a direct cousin invokes a "once removed" relationship between the two (without individually qualifying who is the 'senior' generation, from whom the 'nth' count is determined). You would normally only qualify "first cousin" if this fact is considered important, and "zero times removed" would also be considered implicit.

As pointed out in the title text, cat lifespans (or, more importantly, inter-generational breeding cycles) are somewhat different from those of humans. Although they would have still been very similar immediately after the divergence from the appropriate MRCA, the differences will have built up to a generational-count displacement of a similarly extreme nature. i.e. that while the shared ancestor is Cueball's 17-million-or-so-Great Grandparent, the cat is in turn the 31-million-or-so-Great Grandchild. Exactly how accurate, or even precise, Randall considers these numbers is unknown, but it is the kind of fact that we know he likes to research and use expert opinion for.

According to [https://www.quora.com/How-many-generations-of-human-beings-recognizably-the-same-as-us-have-there-been this Quora page], there have been about 13,000 generations of modern humans, so the people at this party would be quite closely related, all things considered.

[https://www.evogeneao.com/en/learn/tree-of-life The Evogeneao Tree of Life diagram] indicates that humans and cats diverged around 90 million years ago and humans and plants diverged around 1.8 billion years ago.

If we presume that generations of humans since cathood have averaged around 5 years, then 17 millionth cousin is about right.

To get 50 billionth cousin from the potted plant, then generations of humans since planthood would need to average two weeks.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon. Like seriously, don't}}

:[Megan, White Hat, Cueball, Hairy, Danish, a cat, Hairbun, a chair, and a potted plant on a cabinet are "standing" in a line. White Hat is holding a cup and Hairy has his hands to the side. There are arrows pointing to each of the living creatures.]

:14th cousin [Megan]
:2nd cousin [White Hat]
:Me [Cueball]
:12th cousin [Hairy]
:35th cousin [Danish]
:17,000,000th cousin [cat]
:9th cousin [Hairbun]
:50,000,000,000th cousin [potted plant]

:[Caption below the panel:]
:Really, ''every'' gathering is a family reunion.

{{comic discussion}}
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]

[[Category:Comics featuring Hairbun]]
[[Category:Cats]]
[[Category:Biology]]

2577: Sea Chase

2022-02-05T04:20:33Z

Shadowfax37: Misspelling

{{comic
| number = 2577
| date = February 4, 2022
| title = Sea Chase
| image = sea_chase.png
| titletext = There are two rules on this ship: Never gaze back into the projection abyss, and never touch the red button labeled DYMAXION.
}}

==Explanation==
{{incomplete|Created by a FLATTENED OBLATE SPHEROID - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this comic, Randall returns to one of his pet subjects: [[977: Map Projections|map projections]]. Unusually, this time it is from the perspective of people living - or, in this case, sailing - upon the world that is quite literally being mapped.

Two sailing ships, of circa 18th century design, are engaged in a close chase across the {{w|Atlantic}}, the aggressor flying the Skull And Cross-Bones of a stereotypical pirate vessel. The ship being chased, however, has a plan to escape. And the means to do so. At a crucial moment, [[Cueball]] is told to flip an incongruous large switch that (like several [[1620: Christmas Settings|other]] [[1763: Catcalling|artifacts]] in Randall's universe) alters the nature of their reality.

Whereas beforehand the world is directly represented upon a simply contiguous map, the {{w|Robinson projection}}, it is now changed to one (which is actually the new reality) known as {{w|Goode homolosine projection|Goode Homolosine}} in which the flattening of the world mitigates localised warping of angle/distance/area by introducing discontinuities in relatively 'unused' parts of the mapped world, such as the centre of the Atlantic.

By precisely timing the change (as they cross a particular {{w|meridian}}, possibly the 40°W one), they leave the pursuer now on the wrong side of the very real gap, allowing the pursued ship to escape whatever fate they were trying to avoid. Though there is still an oceanic connection, it requires sailing down the edge towards the tropics, rounding this particular rent in the planet's surface and heading back up the other side. This is vastly further than Cueball's ship needs to travel to reach (presumably) any European port in which they can safely moor.

The title text elaborates on the policies of the black-flagged ship: crewmates are never to look into the "projection abyss" and to never hit the red button labeled "DYMAXION."

The first rule suggests that changing the projection of physical reality produces a gap in reality, a void. This may be dangerous to gaze into or simply unnerving to crewmates, hence the rule.

The second rule references a button that seems to do the same thing as the lever but changes the world into a "Dymaxion" (a portmaneau of "dynamic", "maximum" and "tension") projection . The {{w|Dymaxion map|Dymaxion projection}} projects the Earth in a way that preserves land scale as much as possible. (Most maps warp land area, distance, and/or angle.) However, the preservation of scale comes at the cost of dramatically altering a map in a nearly unrecognizable and unintuitive manner.

The necessary discontinuities resulting from pressing this button would be even more strange and mind-bending than the 'interrupted' Goode Homolosine, so turning the world into this projection may be bad, and a good reason to create a rule against pressing the button in question.

The Robinson, Goode Homolosine, and Dymaxion projections have been referenced in [[977: Map Projections]].

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

[A pirate ship flying the Skull and Crossbones is sailing after a merchant ship.]

Merchant 1: They're closing in!

Merchant 2: Hang on, we're almost at the meridian!

[A map of the Earth in the Robinson projection, with two red dots in the middle of the Atlantic Ocean.]

Merchant 2: ''Now!'' Throw the switch!

[Cueball pulls down a giant lever switch labeled "Projection", from "Robinson" to "Goode Homolosine".]

[A map of the Earth in the Goode Homolosine projection, with one red dot on the American side of the split and one red dot on the European side of the split.

{{comic discussion}}

[[Category:Maps]]
[[Category:Comics featuring Cueball]]

2466: In Your Classroom

2021-05-22T04:44:19Z

Shadowfax37: Adds percentages

{{comic
| number = 2466
| date = May 21, 2021
| title = In Your Classroom
| image = in_your_classroom.png
| titletext = Ontology is way off to the left and geography is way off to the right.
}}

==Explanation==
{{incomplete|Created by a QUASAR IN YOUR CLASSROOM. The table is still a work in progress. Do NOT delete this tag too soon.}}
Randall has created a thought experiment and corresponding chart about school courses. The idea is, "the subject of the class appears in the classroom" and the chart compares how dangerous and how unusual that would be.

{| class="wikitable"
|+Breakdown of Subjects
|-
!Course Topic
!Weirdness
!Danger
!Explanation
|-

!scope=row|Atmospheric Physics
|0%
|0%
|The presence of atmosphere in the classroom is quite common, as humans require the presence of an atmosphere to remain alive, and cannot learn while dead.{{Citation needed}}
|-

!scope=row|Ethics
|25%
|0%
|Ethical thinking and behavior are widely considered good and should normally be present in education, but are sadly not universal.
|-

!scope=row|Education
|0%
|10%
|Learning usually goes on in classrooms, so education as a concept is both being learned about and present in the form of learning itself.
|-

!scope=row|Bibliography
|25%
|7%
|A bibliography is a list of sources, and students should ideally learn to cite their sources. Presumably, this would be a bibliography at the end of a school paper about bibliographies.
|-

!scope=row|Human Physiology
|0%
|20%
|This comic assumes that there are humans learning in the classroom, which was true at the time this comic was published. However, as of 2038 the Earth has been overtaken and education is forbidden for mere mortals.{{Actual citation needed}}
|-

!scope=row|Public Speaking
|25%
|15%
|Some classes require students to present things in front of the class, which is likely a requirement in a public speaking class. Thus, public speaking itself would be present in the class.
|-

!scope=row|Architecture
|0%
|30%
|All buildings can be considered architecture, and most classes take place in buildings. This comic also refers to a class''room'', which is a room, and therefore considered architecture.
|-

!scope=row|Library Science
|25%
|25%
|Library science is concerned with the organization of knowledge, and is useful for finding information. Many classes require research papers that require the use of books and other sources of information to complete them.
|-

!scope=row|Furniture Design
|0%
|40%
|Most rooms have furniture,{{Citation needed}} so this would probably be present in a classroom
|-

!scope=row|Culinary Arts
|40%
|30%
|
|-

!scope=row|Ergonomics
|5%
|45%
|Ergonomic equipment and workspaces promote comfort and efficiency, while non-ergonomic ones may be unpleasant, unhealthy, or even immediately dangerous.
|-

!scope=row|Botany
|40%
|40%
|
|-

!scope=row|20th Century Authors
|65%
|10%
|A literature class would, normally, benefit greatly from an open discussion or interview with the author himself. Sadly such things are rare. Authors who were published in the 20th century would mostly be in retirement age in 2021, so securing an interview with them could be somewhat difficult.
|-

!scope=row|Exobiology
|100%
|0%
|Exobiology is the study of extraterrestrial life. This would mean that an alien lifeform was in the classroom.
|-

!scope=row|21st Century Authors
|60%
|20%
|
|-

!scope=row|19th Century Authors
|100%
|15%
|Like other authors, the class would benefit from having an actual author show up, but this would be extremely weird since no 19th century author is still alive.
|-

!scope=row|Paleontology
|100%
|25%
|
|-

!scope=row|Robotics
|55%
|30%
|
|-

!scope=row|Martian Soil Chemistry
|100%
|35%
|
|-

!scope=row|Tourism
|75%
|40%
|
|-

!scope=row|Child Psychology
|60%
|45%
|
|-

!scope=row|Entomology
|15%
|55%
|
|-

!scope=row|Occupational Therapy
|10%
|62%
|
|-

!scope=row|Hydraulic Engineering
|40%
|62%
|
|-

!scope=row|Pest Control
|25%
|70%
|
|-

!scope=row|Foodborne Illness
|15%
|80%
|
|-

!scope=row|Criminal Law
|45%
|85%
|
|-

!scope=row|Physiology of Stress
|0%
|90%
|
|-

!scope=row|Oncology
|25%
|100%
|
|-

!scope=row|Ornithology
|60%
|55%
|
|-

!scope=row|Animation
|100%
|56%
|
|-

!scope=row|Petroleum Geology
|65%
|60%
|
|-

!scope=row|Highway Engineering
|75%
|65%
|
|-

!scope=row|Toxicology
|55%
|75%
|
|-

!scope=row|Hematology
|75%
|70%
|Hematology is the study of blood. Given that there should be blood in each of the students present{{Citation needed}}, we should probably assume Randall means "large quantities of blood outside of one's body", which would indeed be both bad and weird.
|-

!scope=row|Hostage Negotiation
|70%
|85%
|Reasons as to why there would be hostage negotiations taking place at a school have horrifying implications for the students and teacher.
|-

!scope=row|History of Siege Warfare
|100%
|80%
|This would mean that the students would be trapped in the building until they ran out of resources, and dies of thirst and starvation (depending on whether or not the opposing army destroyed the school's water lines).
|-

!scope=row|Trauma Surgery
|55%
|95%
|Trauma surgery is an incredibly painful procedure, and difficult to look at for many. It would undoubtedly be disturbing to the class, especially if the patient was one of them.
|-

!scope=row|Volcanology
|75%
|95%
|Having a live volcano in one's classroom is both very dangerous and very weird, as volcanoes take very long times to form. Note this also applies to [[1611: Baking Soda and Vinegar | baking soda and vinegar volcanoes that are offshoots of much larger vinegar hotspots]].
|-

!scope=row|Quasar Astronomy
|75%
|100%
|Quasars are distant astronomical objects that release large amounts of energy.
|-

!scope=row|Ontology (Title Text)
|<0%
|?
|Ontology is the philosophical study of existence and being. Since there must be ''something'' learning in the classroom, it is unsurprising that ontology is a normal subject to appear in the classroom.
|-

!scope=row|Geography (Title Text)
|>100%
|?
|Logistics aside, having a planet's terrain in one's classroom would almost certainly be a distraction to the learning environment.

|}

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

:[Caption above scatter plot with labeled axes]
:Caption: The thing you study just showed up in your classroom! That's...
:Upper y-axis label: Good
:Lower y-axis label: Bad
:Upper x-axis label: Normal
:Lower x-axis label: Weird

:[First quadrant (left to right, top to bottom):]
:20th century authors
:Exobiology
:21st century authors
:19th century authors
:Robotics
:Paleontology
:Martian soil chemistry
:Child psychology
:Tourism
:[Second quadrant]
:Atmospheric physics
:Ethics
:Education
:Bibliography
:Human physiology
:Public speaking
:Architecture
:Library science
:Furniture design
:Culinary arts
:Ergonomics
:Botany
:[Third quadrant]
:Entomology
:Occupational therapy
:Hydraulic engineering
:Pest control
:Foodborne illness
:Criminal law
:Physiology of stress
:Oncology
:[Fourth quadrant]
:Ornithology
:Animation
:Petroleum geology
:Highway engineering
:Toxicology
:Hematology
:Hostage negotiation
:History of siege warfare
:Trauma surgery
:Volcanology
:Quasar astronomy

{{comic discussion}}
[[Category:Charts]]

2386: Ten Years

2020-11-20T03:57:52Z

Shadowfax37: Adding a citation needed joke

{{comic
| number = 2386
| date = November 16, 2020
| title = Ten Years
| image = ten_years.png
| titletext = The ten-year cancerversary is traditionally the Cursed Artifact Granting Immortality anniversary.
}}

==Explanation==
{{incomplete|Created by a CURSED ARTIFACT. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
[[Randall]]'s then-fiancée, now wife was diagnosed with cancer in late 2010. This is a matter he has discussed in the comic [[:Category:Cancer|multiple times before]], with Randall being depicted as Cueball and his wife as Megan. It has been 10 years since her diagnosis and treatments.

This comic is a continuation of [[1141: Two Years]] and [[1928: Seven Years]], which are shown in the first 16 panels, slightly grayed out.

The first of the new panels shows Randall and his wife at a "Rabbit Rescue", interacting with buns ([[:Category:Buns|a recurring theme]] of xkcd). The purpose of such events is to get rescued (often surrendered or seized) rabbits or other animals used to interacting with each other and with unfamiliar humans under controlled circumstances, to help them be more suitable as pets and hopefully entice visitors to adopt them. Randall facetiously asks his wife if she thinks the rabbits have socialized enough, even though he and his wife are there for the sake of their own enjoyment (and she indicates that she would like to spend more time patting a bunny on its head).

In the next panel, Cueball is pushing Megan in a handcart, which is presumably stolen. (As evidenced by the off-panel person asking if anybody has seen the handcart.)

The third new panel shows Cueball and Megan exploring a mountain. They appear to have found something interesting, due to Megan pointing her finger towards something off-panel.

The fourth panel shows Cueball and Megan sitting on the edge of a pier, looking at the night sky. This is a typical romantic nighttime activity{{Citation needed}}.

The fifth new panel shows Cueball and Megan sitting on a hill, talking about how they couldn't believe that Megan would make it to 10 years cancer-free, which according to [[881: Probability]] wasn't all that certain (77% probability -- [[2379: Probability Comparisons|the probability of picking an M&M out of a bag at random and getting one that isn't blue]]). Because the table does not include values for probability of survival more than ten years after treatment, she jokingly concludes that she is now immortal, perhaps thanks to a cursed artifact. Many anniversaries are traditionally marked by giving gifts, such as the {{w|silver jubilee}} after twenty-five years of marriage (or of a monarch's reign, or an employee's seniority within a company, or anything else). The tenth anniversary is traditionally associated with a tin gift (tin being a much more precious metal [https://www.bartleby.com/95/22.html in 1922] than it is today), but maybe Randall bought it at [[2376: Curbside|a cursed shop]].

=== Trivia ===

Cursed artifacts that cannot die were recently mentioned in [[2332: Cursed Chair]].

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:'''From [[1141: Two Years]]'''
:[Randall (drawn as Cueball) and Randall's fiancée (drawn as Megan) sit on a bed, Randall's fiancée is talking on the phone. The person she is talking to, a doctor holding a clipboard, is shown inset.]
:Randall's fiancée: Oh god.

:[Randall and Randall's fiancée sit together while Randall's fiancée, now bald, is receiving chemotherapy. They are both on their laptops.]
:IV pump: ... Beeep ... Beeep ... Beeep ...

:[Randall and Randall's fiancée (who is wearing a knit cap) are paddling a kayak against a scenic mountain backdrop.]

:[Randall and Randall's fiancée sit at a table, staring at a cell phone. There is a clock on the wall. Her head is stubbly.]
:Randall's fiancée: How long can it take to read a scan!?

:[Randall and Randall's fiancée are back at the hospital again, Randall's fiancée receiving chemo. They are playing Scrabble.]
:Randall: "Zarg" isn't a word.
:Randall's fiancée: But ''caaaancer.''
:Randall: ...Ok, fine.

:[Randall and Randall's fiancée (wearing a knit cap) are listening to a Cueball-like friend. A large thought bubble is above their heads and it obscures the friends talk. The text below, split in three is the only part there can be no doubt about:]
:Friend: So next year you should come visit us up in the mounta
::a
::and
:Randall and Randall's fiancée (thinking): '''"Next year"'''

:[Randall and Randall's fiancée are getting married, with a heart above their heads. Randall's wife's hair is growing back.]

:[Randall and Randall's wife (wearing a knit cap) stand on a beach, watching a whale jump out of water.]
:''Fwoosh''

:'''From [[1928: Seven Years]]'''

:[Randall and Randall's wife (with her hair noticeably longer) are walking through a forest.]

:[Randall's wife is sitting down, not in the forest anymore.]
:Randall's wife: My toe hurts and I found a report of a case in which toe pain was an early sign of cancer spreading.
:Randall: Wait—didn’t you stub your toe yesterday?
:Randall's wife: Yes, but what if this is unrelated?

:[Randall and his wife are going spelunking. The guide is gesturing deeper into the cave while Randall and his wife are climbing down.]

:[Randall's wife stands on a rock above an alligator in a swamp, photographing the alligator. Randall is on a balcony behind safety railings.]
:Randall: When they estimated your survival odds, I think they made some optimistic assumptions about your hobbies.

:[Randall's wife sits on an examination bed, listening to a doctor holding a clipboard.]
:Doctor: This is probably nothing.
:Doctor: But given your history, we should do a full scan.
:Doctor: We'll call with the results in a few days. Try not to worry about it until then!

:[Randall and his wife stand above a deep pond full of fish and other objects. Randall's wife is piloting a wired underwater camera with lights.]

:[Randall and his wife are standing next to each other. Randall's wife has shoulder-length hair covering most of her face.]
:Randall's wife: Hard to believe—six years ago, I was bald. But today, after a long struggle, I finally look like the little girl from ''The Ring''.
:Randall: That's, uhh... good?
:Randall's wife: ''Hissssss''

:[A line of six people, including Randall and his wife, stand and watch the solar eclipse.]

'''New to [[2386: Ten Years]]''':
:[Randall and his wife are sitting in a room with five bunnies sitting around and on them. The Poster on the wall reads: Rabbit rescue.]
:Randall: Do you think they're socialized enough?
:Randall's wife: This one might need some more head pats.

:[Randall is running and pushing his wife on a hand cart.]
:Someone off-panel: Has anyone seen the hand cart?
:Randall's wife: Wheee!

:[Randall and his wife walks up hill with snowy mountains near by and in the background. his wife is gesturing to something ahead of them.]

:[A large dark panel, to the right of the previous three, to the left in two rows. Randall and his wife sits, leaning back on their hands looking up, at the end of a pier going into a lake. The end is broader and they sit to each side of the middle of he pier. It is night and behind the lake there is a forest of pine trees. Above the three is a clear starlit night sky with hundreds of stars and the band of the Milky Way clearly visible. The trees and some of the stars are reflected in the water of the lake, distorted by the movements of the water.]

:[Randall is sitting on a grassy field, a bit higher than his wife who lies on her back looking up.]
:Randall: You did it.
:Randall: Ten years.
:Randall's wife: It doesn't seem real.

:[Zoom in on Randall's wife, who is not longer lying down.]
:Randall's wife: When they showed me my 10-year survival chart, I really didn't believe I would make it here.
:Randall's wife: I don't understand why you married me when it looked so bad.
:Randall's wife: But it was very sweet.

:[In a frame-less panel Randall is standing in front of his wife, who is sitting on the ground, arm leaning on her bent knees.]
:Randall: You make it sound like an act of grace, and not something I desperately wanted to do and was worried I wouldn't get to.
:Randall: You're the coolest person I've ever met. I just wanted whatever time we could have.

:[Same setting but seen from a distance and in silhouette. Randall's wife has lifted her fist towards the sky, and it seems like Randall has turned away from her looking up.]
:Randall's wife: Well, good news, my hideous and inexplicable existence continues unabated! Take that, Biology!
:Randall's wife: You failed to kill me and now I can never die!
:Randall: Is... that how it works?
:Randall's wife: It was in the fine print on the chart.

{{comic discussion}}

[[Category:X Years]]
[[Category:Comics featuring Randall Munroe]]
[[Category:Comics featuring real people]]
[[Category:Doctor Ponytail]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Multiple Cueballs]]
[[Category:Cancer]]
[[Category:Romance]]
[[Category:Animals]]
[[Category:Total Solar Eclipse 2017]]
[[Category:Buns]]
[[Category:Comics with inverted brightness]]

2295: Garbage Math

2020-04-19T05:53:39Z

Shadowfax37: Increases width of text-heavy third column

{{comic
| number = 2295
| date = April 17, 2020
| title = Garbage Math
| image = garbage_math.png
| titletext = 'Garbage In, Garbage Out' should not be taken to imply any sort of conservation law limiting the amount of garbage produced.
}}

==Explanation==
{{incomplete|Created by a ZILOG Z80. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This comic explains the "{{w|garbage in, garbage out}}" concept using arithmetical expressions. Just like the comic says, if you get garbage in any part of your workflow, you get garbage as a result. Except when you multiply by zero. That one always fixes everything.

Some of these rules correspond to the rules of {{w|floating point arithmetic}}, while others may be inspired by the rules of {{w|Propagation_of_uncertainty#Example_formulae| propagation of uncertainty}} where a "garbage" number would correspond to an estimate with a high degree of uncertainty, and the uncertainty of the result of arithmetic operations will tend to be dominated by the term with the highest uncertainty. The rule about N pieces of independent garbage reflects the {{w|central limit theorem}} and how it predicts that the uncertainty (or {{w|standard error}}) of an estimate will be reduced when independent estimates are averaged. The comic oddly omits raising garbage to the 0th power, which transforms even NaN, the platonic ideal of garbage, to exactly 1{{Citation needed}}.

This comic is about the propagation of errors in numerical analysis and statistics, but described in much more colloquial terms. Numbers with low precision are termed "garbage" and numbers with high precision are labeled "precise".

This comic is not related to the {{w|2019–20 coronavirus outbreak|2020 pandemic}} of the {{w|coronavirus}} {{w|SARS-CoV-2}}, which causes {{w|COVID-19}}, breaking the streak of comics preceding this on [[:Category:COVID-19|topics relating to COVID-19]], after (rather appropriately) 19 comics (not counting the [[2288: Collector's Edition|April Fools' comic]]).

{| class="wikitable"
!Formula
!Statistical Expression
!Explanation
|-
|Precise number + Precise number = Slightly less precise number
|<math>\mathop\sigma(X+Y)=\sqrt{(\mathop\sigma(X))^2+(\mathop\sigma(Y))^2}</math>
|{{Nowrap|If we know absolute error bars, then adding two precise numbers will}} at worst add the sizes of the two error bars. For example, if our precise numbers are 1 (±10-6) and 1 (±10-6), then our sum is 2 (±2·10-6). It is possible to lose a lot of relative precision, if the resultant sum is close to zero as a result of adding a number and then close to its inverse. This phenomenon is known as catastrophic cancellation. Therefore, it is likely that all numbers referred here are positive numbers, which does not exhibit this phenomenon.
|-
|Precise number × Precise number = Slightly less precise number
|<math>\mathop\sigma(X\times Y)=\sqrt{(\mathop\sigma(X)\times Y)^2+(\mathop\sigma(Y)\times X)^2}</math>
|Here, instead of absolute error, relative error will be added. For example, if our precise numbers are 1 (±10-6) and 1 (±10-6), then our product is 1 (±2·10-6).
|-
|Precise number + Garbage = Garbage
|<math>\mathop\sigma(X+Y)=\sqrt{(\mathop\sigma(X))^2+(\mathop\sigma(Y))^2}</math>
|If one of the numbers has a high absolute error, and the numbers being added are of comparable size, then this error will be propagated to the sum.
|-
|Precise number × Garbage = Garbage
|<math>\mathop\sigma(X\times Y)=\sqrt{(\mathop\sigma(X)\times Y)^2+(\mathop\sigma(Y)\times X)^2}</math>
|Likewise, if one of the numbers has a high relative error, then this error will be propagated to the product. Here, this is independent of the sizes of the numbers.
|-
|<math>\sqrt{\text{Garbage}} = \text{Less bad garbage}</math>
|<math>\mathop\sigma(\sqrt X)=\frac{\mathop\sigma(X)}{2\times\sqrt X} </math>
| When the square root of a number is computed, its relative error will be halved. Depending on the application, this might not be all that much ''better'', but it's at least ''less bad''.
|-
|Garbage2 = Worse garbage
|<math>\mathop\sigma(X^2)=2\times X\times\mathop\sigma(X)</math>
|Likewise, when a number is squared, its relative error will be doubled. This is a corollary to multiplication adding relative errors.
|-
|<math>\frac{1}{N}\sum(\text{N pieces of statistically independent garbage}) = \text{Better garbage}</math>
|
|By aggregating many pieces of statistically independent observations (for instance, surveying many individuals), it is possible to reduce relative error. This is the basis of statistical sampling and the [https://en.wikipedia.org/wiki/Central_limit_theorem central limit theorem].
|-
|Precise numberGarbage = Much worse garbage
|<math>\mathop\sigma(b^X)=b^{2\times X}\times\mathop{\mathrm{ln}}b\times\sigma(X)</math>
|The exponent is very sensitive to changes, which may also magnify the effect based on the magnitude of the precise number.
|-
|Garbage – Garbage = Much worse garbage
|<math>\mathop\sigma(X-Y)=\sqrt{(\mathop\sigma(X))^2+(\mathop\sigma(Y))^2}</math>
|This line involves catastrophic cancellation. If both pieces of garbage are about the same (e.g. if their error bars overlap), then it is possible that the answer is positive, zero, or negative.
|-
|<math>\frac{\text{Precise number}}{\text{Garbage}-\text{Garbage}}</math> = Much worse garbage, possible division by zero
|<math>\mathop\sigma(\frac{a}{X-Y})=|\frac a{X-Y}|\times\sqrt{(\mathop\sigma(X))^2+(\mathop\sigma(Y))^2}</math>
|Indeed, as with above, if error bars overlap then we might end up dividing by zero.
|-
|Garbage × 0 = Precise number
|<math>\mathop\sigma(0)=0</math>
|Multiplying anything by 0 results in 0, an extremely precise number in the sense that it has no error whatsoever since we supply the 0 ourselves. This is equivalent to discarding garbage data from a statistical analysis.
|}

The title text refers to the computer science maxim of "garbage in, garbage out," which states that when it comes to computer code, supplying incorrect initial data will produce incorrect results, even if the code itself accurately does what it is supposed to do. As we can see above, however, when plugging data into mathematical formulas, this can possibly magnify the error of our input data, though there are ways to reduce this error (such as aggregating data). Therefore, the quantity of garbage is not necessarily conserved.

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

[A series of mathematical equations are written from top to bottom]

Precise number + Precise number = Slightly less precise number

Precise number × Precise number = Slightly less precise number

Precise number + Garbage = Garbage

Precise number × Garbage = Garbage

√Garbage = Less bad garbage

1/N Σ (N pieces of statistically independent garbage) = Better garbage

(Precise number)Garbage = Much worse garbage

Garbage – Garbage = Much worse garbage

Precise number / ( Garbage – Garbage ) = Much worse garbage, possible division by zero

Garbage × 0 = Precise number

{{comic discussion}}
[[Category:Math]]

1810: Chat Systems

2017-03-13T21:13:36Z

Shadowfax37: Removing apostrophes after decades

{{comic
| number = 1810
| date = March 13, 2017
| title = Chat Systems
| image = chat_systems.png
| titletext = I'm one of the few Instagram users who connects solely through the Unix 'talk' gateway.
}}

==Explanation==
{{incomplete|Fill in the table and explain the title text. The main purpose of an euler diagram needs to be explained. (E.g. BBM in eMail; WhatsApp in eMail and SMS)}}
In the world of social media, connecting to and communicating with friends, relatives, and other acquaintances can be extremely easy, but due to the large amount of networks and systems through which to communicate, and the selective nature of the people using them, it can be difficult to keep track of who uses which system(s), and thus, communication can be more complicated by social media as well.

;Chat systems mentioned
{| class="wikitable"
!System
!Number of people in group
!Explanation
|-
| {{w|Skype}}
|2
|Microsoft's chat client. It offers VoIP video and audio calls, instant messaging and phoning from within the app.
|-
| {{w|Email}}
|35
|A popular form of electronic communication that saw first widespread use in the 1960s. It allows you to send electronic "letters" to people using pre-exchanged email addresses. Many people use this platform, hence the large size of the corresponding circle.
|-
| {{w|SMS}}
|39
|Short Message System; a text-based messaging system connecting most worldwide phone systems that had its beginnings in the 1980s and has since represented the most common form of data transmission for most people. It is principally used to send short text messages between mobile phones, but most phone carriers provide facilities to send-to-email or send-to-voice (for use with landline phones). Most major phone carriers also provide support for email-to-SMS.
|-
| {{w|AIM}}
|2
|AOL Instant Messaging service; a popular messaging system from the 1990s that suffered a severe decline in 2005 upon the release of Gmail and Google Chat. It is based on the closed source OSCAR protocol, but AOL created the TOC/TOC2 protocol specifications, and made specifications openly available, for third parties to connect to their service. There have been short-lived dalliances with other protocols since 2008; it has never had direct support for the other widely used protocols here.
|-
| {{w|Slack_(software)|Slack}}
|5
|A team instant messaging service
|-
| {{w|Hangouts}}
|9
|Google Hangouts is Google's instant messaging system. It can be used to share data and for video chat.
|-
| {{w|ICQ}}
|1
|An older open-source instant messaging application.
|-
| {{w|iMessage}}
|6
|Apple's SMS service
|-
| {{w|IRC}}
|5
|IRC is an old chat system that many people refuse to switch off of.
|-
| {{w|Snapchat}}
|1
|Snapchat is an image messaging app.
|-
| {{w|Signal_(software)|Signal}}
|8
| An app used for encrypted communications.
|-
| {{w|Facebook_Messenger|FB Messenger}}
|2
|Facebook's chat system.
|-
| {{w|Instagram|Instagram DM}}
|2
|Direct Messaging, a feature of Instagram that allows users to post personal messages to each other.
|-
| {{w|Zephyr (protocol)}}
|1
| Zephyr was designed as an instant messaging protocol and application-suite with a heavy Unix background.
|-
| {{w|WhatsApp}}
|2
|Billed as encrypted end-to-end chat, allows VoIP chats, text chats, video and image sharing. Caters for group chat as well.
|-
| {{w|WeChat}}
|2
| A free, cross-platform and instant messaging application
|-
| Telegram
|2
|Could refer to a cloud based instant messaging system by this name ({{w|Telegram (software)|Telegram}}), or to actually sending messages using {{w|telegrams}}. Telegrams were messages sent by electric telegraphy, which were often typed out and hand-delivered to the recipient. This was the first system for rapid communication across long distances that was widely available, originally developed in the 19th century. Naturally, telegraphy is now wildly obsolete (though some local services apparently do still exist) which would explain why Munroe communicates with so few people that way.
|-
|{{w|Apache_HTTP_Server|Apache}} Request {{w|Server_log|Log}}
|1
|A file used by Apache HTML server to log page access requests by users, usually stored as access_log. Its use as a communications tool would require the user to embed their messages in URLs and the admin to look for the messages in the logs. It would be inconvenient and time consuming for both parties.
|-
| {{w|Twitter|Twitter DM}}
|4
| "Direct messages" between users on Twitter.
|-
| {{w|BlackBerry Messenger|BBM}}
|1
|Blackberry message. A chat system available on {{w|BlackBerry}} phones, now largely obsolete.
|-
|{{w|Peach_(social_network)|Peach}}
|2
|
|-
|{{w|Talk_(software)|Unix 'talk'}}
|*
|This is in the title text, and the only user is Munroe. Old peer-to-peer chat system whereby users logged into the same UNIX system could privately communicate with each other in a full-screen interface.
|-
|{{w|Wall (Unix)}}
|1
|Short for "write all", the "wall" command copies its argument to every user logged into the same Unix system, and so can be used as a primitive chat system. {{w|Wall_(Unix)}}
|-
|Wall (bathroom)
|1
|Apparently a chat system based around writing on the wall in the bathroom. Not an electronic system. Alternatively, this could mean the person is an extreme introvert, and hides in his bathroom instead of interacting with others.
|-
|The "chat" tab in an old {{w|Google Doc}}
|2
|Google Docs is an online word processor reminiscent of Microsoft Word. One of the notable features is online collaborative editing, with a rudimentary chat feature for communication. Randall apparently communicates with someone using the chat in an old Google Doc.
|}

;Related comics
*The ubiquity of standards - here, of messaging systems - was already covered in [[927: Standards]]
*For IRC see also [[1782: Team Chat]]

==Transcript==
{{incomplete transcript}}
:[an Euler diagram with a large number of circles for various chat systems, overlapping in complicated ways]
:I have a hard time keeping track of which contacts use which chat systems.

{{comic discussion}}

1621: Fixion

2015-12-27T03:19:09Z

Shadowfax37:

{{comic
| number = 1621
| date = December 25, 2015
| title = Fixion
| image = fixion.png
| titletext = My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.
}}

==Explanation==
The second [[:Category:Christmas|Christmas comic]] in a row, the first being [[1620: Christmas Settings]].

This comic was released on {{w|Christmas}} day as a present from [[Randall]] to all {{w|physicists}}. It introduces a new particle, the ''Fixion'', which explains everything. The word "Fixion" can be read as a pun: Either it can mean something like "fix-i-on," with "[https://en.wiktionary.org/wiki/-on#Suffix -on]" being a suffix for many particles, and this particle being able to "fix" things; or it means "fiction" (in English, the pronunciations of "-xion" and "-ction" are indistinguishable). Alternately, "Fixion" could be a portmanteau of "fix" and "ion", implying that the particle is not subatomic but is a different type of ion.

In physics, there are still many {{w|List of unsolved problems in physics|big questions and mysteries}}. There are many phenomena which don't seem to fit, and we don't know how to explain yet. The "Fixion" is satirically presented as a particle which acts as a {{w|Deus ex machina}}, (see also [http://tvtropes.org/pmwiki/pmwiki.php/Main/DeusExMachina tvtropes]), which solves all of these mysteries without any serious fundamental reasons.

The style of the chart suggests a {{w|Feynman diagram}} - an easy way of drawing particle interactions. Every time there is an interaction, the main central Fixion-line changes direction. Typically, {{w|fermions}} (the "solid" particles like {{w|electrons}} and {{w|quarks}}) are shown with solid lines, {{w|photons}} (and generally the weak-force-carrying {{w|bosons}}) are shown with wavy lines, {{w|gluons}} with spiraling lines and other mediating particles (such as {{w|pions}} in the {{w|nuclear force}}, or the {{w|Higgs boson}}) with a dotted line. Randall obeys these rules only very loosely, which makes sense - many of the things involved in this Feynman diagram are either so theoretical that they have no widely used standard representation, or would never appear in a sensible diagram (spacecrafts, for instance). All mentioned types of lines - and even more types - are presented in the diagram. All that the Fixion does is described in the [[#Table of Phenomena|table below]].

The title text is a continuation of one of the jokes already mentioned in the main comic (fourth phrase from the top to the left) about {{w|Fast radio burst}}s (FRBs) and {{w|Peryton (astronomy)|perytons}}. See explanation in the last entry in the [[#Table of Phenomena|table below]].

===Table of Phenomena===
*Below, all the phenomenons mentioned in the comic (and in the title text) has been listed and described.
*The order is the top left phenomenon first, and then alternating between right and left down to the bottom and then the title text at the end.
{| border =1 width=100% cellpadding=5 class="wikitable"
|'''Phenomenon''' || '''In the comic''' || '''Description''' || '''Solved?'''
|-
| Main component of dark matter
|| An arrow points to the very first part of the main line.
|| Our best measurements of the universe predict that visible matter is only about one-sixth of the matter in the universe; the remaining matter is "{{w|dark matter}}" that cannot be seen. The leading candidates for dark matter are {{w|weakly interacting massive particles}} (WIMPs). These would be new, undiscovered forms of matter which barely interact except through gravity and thus give off little or no light. Some of the dark matter is likely made up of {{w|Massive compact halo objects}} (MACHOs); effectively dead stars too dim to see. MACHOs are probably only a minority of the dark matter, however. Studies of two colliding galaxy clusters suggest that dark matter can pass through other matter without slowing down, unlike ordinary matter. Moreover, calculations of the elements produced during the {{w|big bang}} - which match the observed distribution of elements in the universe very precisely - don't leave room for enough additional {{w|protons}} and {{w|neutrons}} to form the dark matter.
|| No. Proving the nature of dark matter will most likely win someone a {{w|Nobel Prize}}.
|-
| Confines quarks and gluons
|| An arrow points to the very first part of the main line.
|| {{w|Quark confinement}} means that we never see particles with {{w|colour charge|color charge}} (i.e. {{w|quark}}s and {{w|gluon}}s) on their own. They only exist in groups that cancel out the color charge. Try to separate the groups, and the energy you add will instead cause new particles to pop into existence.
|| The basic facts of confinement are well understood, but some of the details are too complicated to tease out.
|-
| Neutralizes monopoles
|| An arrow points to the first solid line going away from the main line, left and upwards. This is thus a solid particle going out from the Fixion.
|| {{w|Magnetic monopoles}} (i.e., a north charge without a south charge) should exist, according to many {{w|Grand Unified Theory|grand unified theories}} (GUTs) and {{w|String theory|string theories}}, but none have ever been seen.
|| No! Despite claims that pop up in the news every year, creating a monopole-like state in the magnetic spins of a crystal is not the same as creating a real monopole.
|-
| Suppresses antimatter in early universe
|| No arrow.
|| The universe today is made almost entirely of matter. {{w|Antimatter}} and matter are identical, except that the charges are opposite. Antimatter and matter "{{w|Annihilation|annihilate}}" when they come into contact? So why is the universe made of matter? Why didn't the universe have equal amounts of both, and if it did, why didn't it annihilate itself immediately? This is a big question in physics today. Of course, the Fixion explains this by its ability to suppress the formation of antimatter in the early universe.
|| Lots of theories, no conclusive evidence for any yet. The most notable theories revolve around the {{w|weak interaction}}, which has been shown to treat matter and antimatter asymmetrically. Now that the {{w|Higgs boson}} has been found, the biggest project for the {{w|Large Hadron Collider}} experiments is to try to crack this.
|-
| Spontaneously emits dark energy
|| Two arrows points to two dotted lines going out left and downwards below the first solid line. It is thus two mediating particles that go out from the Fixon.
|| Prior to the 1990s, most {{w|cosmologists}} expected that the universe's expansion after the Big Bang would either slow down or stay constant. In 1998, cosmologists discovered that the expansion of the Universe is accelerating. Under {{w|Einstein|Einstein's}} theory of {{w|general relativity}}, the observed acceleration predicts that ordinary matter and dark matter make up about 30% of the universe's total energy, with the rest coming in the form of "{{w|dark energy}}." The nature of dark energy is not certain. However, the leading candidate is that space itself has intrinsic energy (either constant or variable), and so as space expands, the energy of the universe increases.
|| Again, Nobel Prize territory.
|-
| Mediates proton decay, but then hides it.
|| An arrow point to several lines going to and from the main line. The outer line does not connect with the main line. Maybe this represents the hiding part of this proton decay mediator.
|| Many GUTs predict that {{w|proton decay|protons will decay}}, but experiments have shown the proton to have a half-life of at least 1033 years very much longer than the {{w|age of the universe}} (1.38x1010 years).
|| It's not ''necessarily'' a problem. All theories predict that proton decay is a very slow process (1032+ seconds), which is consistent with the current data.
|-
| Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts
|| Two arrows point to four wavy lines. The waves of the lines have different wave length. The one line coming out left is of the same at wavelength as the top of the three coming out right. The two below each decrease in wavelength compared to the one before them. Maybe this is not meant to represent photon-like particles, but are just different frequencies of microwaves from the microwave oven – thus relating to the subject.
|| {{w|Fast radio burst}}s (FRBs) are unexplained bursts of radio-frequency energy from space, they could even be extragalactic signals, with speculations that they might be signs of {{w|extraterrestrial intelligence}}. {{w|Peryton (astronomy)|Perytons}} are things that ''look like'' FRBs, but come from Earth (specifically, from the {{w|microwave oven}} at {{w|Parkes Observatory}}). Randall's Fixion makes some perytons change frequency distribution so they appear to come from space; thus in fact all FRBs come from microwave ovens.
|| No, but it's probably something very big - a star collapsing to a {{w|black hole}} or (as now looks likely) a {{w|magnetar}} (magnetic neutron star)
|-
| Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment
|| An arrow points to the part of the main line just before the first wavy line.
|| The {{w|neutron electric dipole moment}} is a measure of how balanced electric charge is inside the neutron. ϴ (theta) is a number in {{w|quantum chromodynamics}} (QCD) which quantifies the breaking of a type of symmetry called {{w|CP violation|CP symmetry}}. If ϴ is not 0, one result of this should be a neutron dipole moment. {{w|Symmetry breaking}} is a common explanation of effects in some areas of theoretical physics (for instance, it's an important part of {{w|Peter Higgs|Higgs'}} theory about why particles have mass), but normally it explains why a value is ''not'' zero. Presumably the Fixion breaks CP symmetry independently of QCD, which means that ϴ can be 0 while preserving observed CP-breaking effects.
|| Again, it's not (yet) a problem - the predicted dipole moment is tiny, and we're only just reaching the point when we can measure it that accurately.
|-
| Causes alpha effect
|| No arrow.
|| Ther {{w|alpha effect}} is a weird effect from chemistry, where putting an "alpha" atom with a {{w|lone pair}} of electrons close to a molecule makes the molecule more likely to give up its electrons. The Fixion is the reason for this effect.
|| Lots of competing explanations.
|-
| Covers naked singularities
|| No arrow – but the text is situated next to the middle of the three wavy lines going right.
|| A {{w|naked singularity}} is like a black hole without an {{w|event horizon}}. So far no naked singularity has been observed (except, arguably, the big bang) and the {{w|cosmic censorship hypothesis}} suggests they can't exist, although some people have suggested ways of making them. Of course if any did exist then the Fixion will cover it, so it won’t become embarrassed by its nudity. Randall has mentioned these in his latest [[what if?]]: [http://what-if.xkcd.com/140/ Proton Earth, Electron Moon].
|| Not necessarily something that needs explaining - none have been seen, and most theories say they don't exist. If support grows for {{w|loop quantum gravity}}, then we might have to start really searching.
|-
| Intercepts certain gravitational waves before they're observed.
|| An arrow points to a spiraling line going upwards to the left, so this is drawn like a gluon.
|| If {{w|gravity}} behaves like {{w|Fundamental interaction|the other forces}}, it must be conveyed by waves. Our best detector, {{w|LIGO}} has yet to detect any {{w|gravitational waves}}, though this is probably just due to the low probability of events that would be detectable. Only extreme events like {{w|binary black hole}} mergers are detectable with the current setup. The proposed {{w|LISA Pathfinder}} spacecraft will be able to see things like orbiting black holes and {{w|neutron stars}}. Since the Fixion intercepts gravity waves before they are observed we should not get our hopes up too high about observing any even with LISA.
|| Let's wait for the LISA data before jumping to conclusions.
|-
| Causes coronal heating
|| No arrow – but the text is situated next to the middle of the three wavy lines going right.
|| For some reason the outer layer of the {{w|sun}} (the {{w|corona}}) is hotter than most reasonable theories predict. This is for instance mentioned in Randall’s new book ''[[Thing Explainer]]'' in the entry about the sun. This can also be seen on the [[Thing_Explainer#Preview Pages |back cover of the book]]. The phenomenon is explained by the Fixion…
|| It's a mystery, but it possibly has something to do with waves in the corona (for example, the {{w|High Resolution Coronal Imager}} has seen "braids" in the corona that whip around and unravel themselves).
|-
| Higgs-ish
|| As this is just a property of the Fixion there is no arrow.
|| The {{w|Higgs boson}} is a manifestation of the Higgs field... but many supersymmetry and string theories predict multiple Higgs-like particles. It's almost a prerequisite of any new theory that it has a Higgs-ish element. So the Fixion blends in with this.
|| N/A
|-
| Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find)
|| An arrow points to the point of the main line just below the bottom space probe.
|| The {{w|Cosmic Microwave Background}} (CMB) is incredibly uniform. In fact it is so uniform that the conclusion is that these areas must have been in contact at some time in the early universe. But with the universe being infinite, and the speed of light being finite, most parts of the universe will never be able to interact (any more at least). The explanation usually given for the uniformity is that the universe expanded really fast in the beginning during what is called the {{w|Inflationary epoch}}. {{w|BICEP_and_Keck_Array#BICEP2|BICEP2}} is a {{w|radio telescope}} at the South Pole whose operators claim to have seen polarization in the CMB indicative of inflation. (See [[1365: Inflation]] that references BICEP2's results). The Fixion fixes the problem since it allowed {{w|Faster-than-light|superluminally}} smoothing of the early anisotropies to explain the smoothness observed today. The Fixion has left just enough signal that the new {{w|BICEP_and_Keck_Array#BICEP3|BICEP3}} telescope will be able to find them.
|| As stated, {{w|Inflation (cosmology)|inflation}} is the standard explanation and it holds up fairly well. Other studies haven't seen the polarization that BICEP2 has - the {{w|Planck (spacecraft)|Planck space telescope}} also suggests that the BICEP2 team were looking at an unusually dusty bit of space, which could cause polarization. Hopefully this will improve with the BICEP3 data that should be published in 2016.
|-
| Accelerates certain spacecraft during flybys
|| Two arrows point to two solid lines going away from the main line (left and right). At the end of each line there is a space craft with satellite dish and solar panels, representing the items that the Fixion interacts with.
|| This refers to the {{w|flyby anomaly}} which is sometimes (but not always) seen when spacecraft fly close to planets and pick up more speed than expected. It's not always seen – for instance the {{w|Rosetta (spacecraft)|Rosetta space probe}} had no flyby anomaly when it swooped extremely close to Mars. Another anomaly for spacecraft’s (a deceleration this time) has been mentioned in the title text of [[502: Dark Flow]].
|| It could be an unpredicted quirk of gravity and relativity... or it could be experimental error.
|-
| Triggers Siberian sinkholes
|| No arrow, but it is right next to the solid line with an arrow going into the main line just before the first hole where the main line disappears and becomes dotted. Thus it could be a reference also to these holes.
|| Recently, (2014), several {{w|sinkholes}} opened up in {{w|Yamal_Peninsula#Yamal_craters |remote parts}} of Siberia. The explanation is currently unknown, except of course we now know that it was the Fixion that caused it.
|| While there are lots of weird theories, there's a good chance they were caused by {{w|Arctic methane release}} due to melting {{w|permafrost}} which is probably caused by {{w|global warming}}. See ([http://www.independent.co.uk/news/science/mystery-of-the-siberian-holes-at-the-end-of-the-world-solved-scientists-offer-explanation-9642988.html Mystery of the Siberian holes… solved]).
|-
| Melts ice in "Snowball Earth" scenario
|| No arrow.
|| {{w|Snowball Earth}} is the theory that the whole planet was covered in ice at some point. To melt all that ice by the {{w|greenhouse effect}} would require far more carbon dioxide in the atmosphere than seems plausible. However, if volcanoes were to deposit black soot on the surface of the ice, it would start absorbing heat more efficiently (in scientific terms, the Earth's {{w|albedo}} would decrease) and that would also make the planet heat up. Of course it was the Fixion was the cause of the melting ice.
|| There are {{w|Snowball_Earth#Scientific_dispute|scientific dispute}} regarding the theory for a Snowball Earth. There is no conclusive evidence that it ever occurred, but those in favor has presented lots of {{w|Snowball_Earth#Evidence|evidence}}…
|-
| Transports neutrinos faster than light, but only on certain days through one area of France
|| An arrow points to the part of the main line that becomes dotted between the two “{{w|wormholes}}”. This is where the neutrinos move faster than light…
|| Refers to the {{w|faster-than-light neutrino anomaly}}, where it seemed that a neutrino beam from {{w|CERN}} on the France/Switzerland border to the {{w|OPERA experiment}} in Italy traveled faster than light. Scientists were not able to reproduce the result. Of course it was because of the Fixion. This Neutrino experiment was also mentioned in [[955: Neutrinos]], where there are more explanation on the subject.
|| In the end, there was no mystery, just a [http://www.redorbit.com/news/science/1112551696/cern-confirms-neutrinos-not-faster-than-light/ defective cable causing a measurement error].
|-
| Suppresses sigma in experiments
|| No arrow but the last solid line, with an arrow pointing left, that is going away from the main line, point almost directly at it.
|| Sigma (σ) refers to the {{w|standard deviation}} - a mathematical measure of how much an observed value differs from the expected value. For a formal scientific discovery in particle physics, the standard is 5 sigma which means that there is about a 1 in 3.5 million chance that the results were caused by random errors (of course, they could be caused by ''systematic'' errors, such as measurement problems). Some tantalizing experiments have found interesting results at 3 or 4 sigma but either can't reach 5 sigma or {{w|Oops-Leon|are subsequently dis-proven}}. The question is, if the way the Fixion works here in this comic pushes the sigma value one way or the other? Does it suppress the value so it goes below or above the level of significance? Is it artificially pushed in the direction so a result seems like it is significant when it is not (see for instance [[882: Significant]]), or if it is the other way so some experiments, which could have found what the experimenters wanted to find, did not because the sigma has been artificially lowered below the proof threshold. Either way it is a very annoying fact of the Fixion, but it would explain a lot, and probably also make it very hard to find the Fixion because of this intrinsic behavior.|| N/A
|-
| My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.
|| From the title text.
|| This is a continuation of the joke already mentioned above regarding Fast radio bursts (FRBs) and perytons. GUTs normally predict that all the forces we see are the different low-energy versions of a single force which can only be seen at extremely high energies (much higher than any Earth-based collider could produce). A high-energy FRB would be a {{w|gamma ray burst}} and if it came from a close enough object, would obliterate all life on Earth... It would also wreck the sensitive electronics at Parkes Observatory. This "high energy unification" is stated in a way reminiscent of the unification of electromagnetic and weak forces at high energies; but unlike the latter, it involves two things only "appearing" (or, in this case, not appearing) to be the same, not actually becoming the same.
|| N/A
|}

==Transcript==
:[Caption above the panel:]
:A Christmas gift for physicists:
:The '''Fixion'''
:A new particle that explains everything

:[A chart resembling a Feynman diagram is shown. It begins with a solid line coming down at the top, going a little to the left. The line continues downwards all the time, but changes direction 16 times before exiting at the bottom almost straight under the starting point. At every point where it changes direction, there is some kind of “interaction” with something outside this line. There are 19 phrases, 10 on the left and 9 on the right. 11 of these are distinct labels for points on the line as 14 gray curved arrows points between these 11 phrases to specific points on the line. Three of the phrases on the left has two arrows pointing to two different, but close, parts of the line. The main central line is solid all the way, except at the very bottom, where it “disappears” inside a hole only to “reappear” later from a similar hole. Between these two holes the line is dotted. The lines going away (or to) the main line can be straight and solid, straight and dotted, wavy lines (with different waviness), even looking like a spiral. Two straight solid lines ends up at two space probes, and finally the last two straight solid lines coming in (and out) on either side of the “hole” in the line has arrow pointing in and out. Below the phrases will be listed in reading order, taking one on each side alternatingly. Above each is described if there are any arrow and, if there are, what they points at.]

:[Left: Arrow pointing to the very first part of the main line:]
::Main component of dark matter

:[Right: Arrow pointing to the very first part of the main line, but below the previous arrow:]
::Confines quarks and gluons

:[Left: Arrow points to the first solid line going left and upwards:]
::Neutralizes monopoles

:[Right: No arrow:]
::Suppresses antimatter in early universe

:[Left: Two arrows points to two dotted lines going out left and downwards below the first solid line:]
::Spontaneously emits dark energy

:[Right: Arrow pointing to several lines going almost parallel with the main line. The first line closest to the arrow is not connected with the main line. It bends closer to the other lines in the middle. The next line is connected to the main line, and is thus actually two lines going in to the main line. The same goes for the inner line, where there is some distance between the entry and exit, as the middle of these three lines connect to the main line in between. In principle there are four lines going in/out and one not connected, but it looks like three lines:]
::Mediates proton decay but then hides it

:[Left: One arrow points to the first wavy line (7 peaks) coming out and up towards the dotted lines above. A second arrow points further down the main line where there are three more wavy lines coming out, but to the right, they are all of the same length and go almost straight right, only a little down. The first has as short a wave length as the line above to the left, but as it is shorter it only has 6 peaks. Then the wavelength decreases to a very long one for the last, 5 peaks and then 3 peaks. The arrow points almost where the middle wavy line exits the main line:]
::Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts

:[Right: An arrow point to the part of the main line between the three parallel lines and the first wavy line:]
::Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment

:[Left: No arrow:]
::Causes alpha effect

:[Right: No arrow, but right next to the middle of the three wavy line:]
::Covers naked singularities

:[Left: An arrow points to a spiraling line going upwards to the left:]
::Intercepts certain gravitational waves before they're observed.

:[Right: No arrow, but right next to the bottom of the three wavy line:]
::Causes coronal heating

:[Left: No arrow:]
::Higgs-ish

:[Right: A long arrow point to the point of the main line just below the line pointing to the bottom (and left) of the space probes:]
::Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find)

:[Left: One arrows point towards the point on the main lines where a solid line goes to the right and up and another arrow points on another solid line going away from the main line towards left and down. At the end of both lines are drawn spacecrafts with satelite dish and solar panels:]
::Accelerates certain spacecraft during flybys

:[Right: No arrow, but right next to the solid line with an arrow going into the main line just before the first hole where the main line disappears and becomes dotted:]
::Triggers Siberian sinkholes

:[Left: No arrow:]
::Melts ice in "Snowball Earth" scenario

:[Right: Arrow points to the dotted part of the main line between the two holes:]
::Transports neutrinos faster than light, but only on certain days through one area of France

:[Left: No arrow but the last solid line, with an arrow pointing left, that is going away from the main line, point almost directly at it:]
::Suppresses sigma in experiments

{{comic discussion}}

[[Category:Christmas]]
[[Category:Charts]]
[[Category:Science]]
[[Category:Astronomy]]
[[Category:Physics]]
[[Category:Space]]
[[Category:Puns]]
[[Category:Language]]
[[Category:Portmanteau]]

1621: Fixion

2015-12-27T03:18:18Z

Shadowfax37: spelling error

{{comic
| number = 1621
| date = December 25, 2015
| title = Fixion
| image = fixion.png
| titletext = My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.
}}

==Explanation==
The second [[:Category:Christmas|Christmas comic]] in a row, the first being [[1620: Christmas Settings]].

This comic was released on {{w|Christmas}} day as a present from [[Randall]] to all {{w|physicists}}. It introduces a new particle, the ''Fixion'', which explains everything. The word "Fixion" can be read as a pun: Either it can mean something like "fix-i-on," with "[https://en.wiktionary.org/wiki/-on#Suffix -on]" being a suffix for many particles, and this particle being able to "fix" things; or it means "fiction" (in English, the pronunciations of "-xion" and "-ction" are indistinguishable). Alternately, "Fixion" could be a portmanteau of "fix" and "ion", implying that the particle is not subatomic but is a different type of ion.

In physics, there are still many {{w|List of unsolved problems in physics|big questions and mysteries}}. There are many phenomena which don't seem to fit, and we don't know how to explain yet. The "Fixion" is satirically presented as a particle which acts as a {{w|Deus ex machina}}, (see also [http://tvtropes.org/pmwiki/pmwiki.php/Main/DeusExMachina tvtropes]), which solves all of these mysteries without any serious fundamental reasons.

The style of the chart suggests a {{w|Feynman diagram}} - an easy way of drawing particle interactions. Every time there is an interaction, the main central Fixion-line changes direction. Typically, {{w|fermions}} (the "solid" particles like {{w|electrons}} and {{w|quarks}}) are shown with solid lines, {{w|photons}} (and generally the weak-force-carrying {{w|bosons}}) are shown with wavy lines, {{w|gluons}} with spiraling lines and other mediating particles (such as {{w|pions}} in the {{w|nuclear force}}, or the {{w|Higgs boson}}) with a dotted line. Randall obeys these rules only very loosely, which makes sense - many of the things involved in this Feynman diagram are either so theoretical that they have no widely used standard representation, or would never appear in a sensible diagram (spacecrafts, for instance). All mentioned types of lines - and even more types - are presented in the diagram. All that the Fixion does is described in the [[#Table of Phenomena|table below]].

The title text is a continuation of one of the jokes already mentioned in the main comic (fourth phrase from the top to the left) about {{w|Fast radio burst}}s (FRBs) and {{w|Peryton (astronomy)|perytons}}. See explanation in the last entry in the [[#Table of Phenomena|table below]].

===Table of Phenomena===
*Below, all the phenomenons mentioned in the comic (and in the title text) has been listed and described.
*The order is the top left phenomenon first, and then alternating between right and left down to the bottom and then the title text at the end.
{| border =1 width=100% cellpadding=5 class="wikitable"
|'''Phenomenon''' || '''In the comic''' || '''Description''' || '''Solved?'''
|-
| Main component of dark matter
|| An arrow points to the very first part of the main line.
|| Our best measurements of the universe predict that visible matter is only about one-sixth of the matter in the universe; the remaining matter is "{{w|dark matter}}" that cannot be seen. The leading candidates for dark matter are {{w|weakly interacting massive particles}} (WIMPs). These would be new, undiscovered forms of matter which barely interact except through gravity and thus give off little or no light. Some of the dark matter is likely made up of {{w|Massive compact halo objects}} (MACHOs); effectively dead stars too dim to see. MACHOs are probably only a minority of the dark matter, however. Studies of two colliding galaxy clusters suggest that dark matter can pass through other matter without slowing down, unlike ordinary matter. Moreover, calculations of the elements produced during the {{w|big bang}} - which match the observed distribution of elements in the universe very precisely - don't leave room for enough additional {{w|protons}} and {{w|neutrons}} to form the dark matter.
|| No. Proving the nature of dark matter will most likely win someone a {{w|Nobel Prize}}.
|-
| Confines quarks and gluons
|| An arrow points to the very first part of the main line.
|| {{w|Quark confinement}} means that we never see particles with {{w|colour charge|color charge}} (i.e. {{w|quark}}s and {{w|gluon}}s) on their own. They only exist in groups that cancel out the color charge. Try to separate the groups, and the energy you add will instead cause new particles to pop into existence.
|| The basic facts of confinement are well understood, but some of the details are too complicated to tease out.
|-
| Neutralizes monopoles
|| An arrow points to the first solid line going away from the main line, left and upwards. This is thus a solid particle going out from the Fixion.
|| {{w|Magnetic monopoles}} (i.e., a north charge without a south charge) should exist, according to many {{w|Grand Unified Theory|grand unified theories}} (GUTs) and {{w|String theory|string theories}}, but none have ever been seen.
|| No! Despite claims that pop up in the news every year, creating a monopole-like state in the magnetic spins of a crystal is not the same as creating a real monopole.
|-
| Suppresses antimatter in early universe
|| No arrow.
|| The universe today is made almost entirely of matter. {{w|Antimatter}} and matter are identical, except that the charges are opposite. Antimatter and matter "{{w|Annihilation|annihilate}}" when they come into contact? So why is the universe made of matter? Why didn't the universe have equal amounts of both, and if it did, why didn't it annihilate itself immediately? This is a big question in physics today. Of course, the Fixion explains this by its ability to suppress the formation of antimatter in the early universe.
|| Lots of theories, no conclusive evidence for any yet. The most notable theories revolve around the {{w|weak interaction}}, which has been shown to treat matter and antimatter asymmetrically. Now that the {{w|Higgs boson}} has been found, the biggest project for the {{w|Large Hadron Collider}} experiments is to try to crack this.
|-
| Spontaneously emits dark energy
|| Two arrows points to two dotted lines going out left and downwards below the first solid line. It is thus two mediating particles that go out from the Fixon.
|| Prior to the 1990s, most {{w|cosmologists}} expected that the universe's expansion after the Big Bang would either slow down or stay constant. In 1998, cosmologists discovered that the expansion of the Universe is accelerating. Under {{w|Einstein|Einstein's}} theory of {{w|general relativity}}, the observed acceleration predicts that ordinary matter and dark matter make up about 30% of the universe's total energy, with the rest coming in the form of "{{w|dark energy}}." The nature of dark energy is not certain. However, the leading candidate is that space itself has intrinsic energy (either constant or variable), and so as space expands, the energy of the universe increases.
|| Again, Nobel Prize territory.
|-
| Mediates proton decay, but then hides it.
|| An arrow point to several lines going to and from the main line. The outer line does not connect with the main line. Maybe this represents the hiding part of this proton decay mediator.
|| Many GUTs predict that {{w|proton decay|protons will decay}}, but experiments have shown the proton to have a half-life of at least 1033 years very much longer than the {{w|age of the universe}} (1.38x1010 years).
|| It's not ''necessarily'' a problem. All theories predict that proton decay is a very slow process (1032+ seconds), which is consistent with the current data.
|-
| Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts
|| Two arrows point to four wavy lines. The waves of the lines have different wave length. The one line coming out left is of the same at wavelength as the top of the three coming out right. The two below each decrease in wavelength compared to the one before them. Maybe this is not meant to represent photon-like particles, but are just different frequencies of microwaves from the microwave oven – thus relating to the subject.
|| {{w|Fast radio burst}}s (FRBs) are unexplained bursts of radio-frequency energy from space, they could even be extragalactic signals, with speculations that they might be signs of {{w|extraterrestrial intelligence}}. {{w|Peryton (astronomy)|Perytons}} are things that ''look like'' FRBs, but come from Earth (specifically, from the {{w|microwave oven}} at {{w|Parkes Observatory}}). Randall's Fixion makes some perytons change frequency distribution so they appear to come from space; thus in fact all FRBs come from microwave ovens.
|| No, but it's probably something very big - a star collapsing to a {{w|black hole}} or (as now looks likely) a {{w|magnetar}} (magnetic neutron star)
|-
| Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment
|| An arrow points to the part of the main line just before the first wavy line.
|| The {{w|neutron electric dipole moment}} is a measure of how balanced electric charge is inside the neutron. ϴ (theta) is a number in {{w|quantum chromodynamics}} (QCD) which quantifies the breaking of a type of symmetry called {{w|CP violation|CP symmetry}}. If ϴ is not 0, one result of this should be a neutron dipole moment. {{w|Symmetry breaking}} is a common explanation of effects in some areas of theoretical physics (for instance, it's an important part of {{w|Peter Higgs|Higgs'}} theory about why particles have mass), but normally it explains why a value is ''not'' zero. Presumably the Fixion breaks CP symmetry independently of QCD, which means that ϴ can be 0 while preserving observed CP-breaking effects.
|| Again, it's not (yet) a problem - the predicted dipole moment is tiny, and we're only just reaching the point when we can measure it that accurately.
|-
| Causes alpha effect
|| No arrow.
|| Ther {{w|alpha effect}} is a weird effect from chemistry, where putting an "alpha" atom with a {{w|lone pair}} of electrons close to a molecule makes the molecule more likely to give up its electrons. The Fixion is the reason for this effect.
|| Lots of competing explanations.
|-
| Covers naked singularities
|| No arrow – but the text is situated next to the middle of the three wavy lines going right.
|| A {{w|naked singularity}} is like a black hole without an {{w|event horizon}}. So far no naked singularity has been observed (except, arguably, the big bang) and the {{w|cosmic censorship hypothesis}} suggests they can't exist, although some people have suggested ways of making them. Of course if any did exist then the Fixion will cover it, so it won’t become embarrassed by its nudity. Randall has mentioned these in his latest [[what if?]]: [http://what-if.xkcd.com/140/ Proton Earth, Electron Moon].
|| Not necessarily something that needs explaining - none have been seen, and most theories say they don't exist. If support grows for {{w|loop quantum gravity}}, then we might have to start really searching.
|-
| Intercepts certain gravitational waves before they're observed.
|| An arrow points to a spiraling line going upwards to the left, so this is drawn like a gluon.
|| If {{w|gravity}} behaves like {{w|Fundamental interaction|the other forces}}, it must be conveyed by waves. Our best detector, {{w|LIGO}} has yet to detect any {{w|gravitational waves}}, though this is probably just due to the low probability of events that would be detectable. Only extreme events like {{w|binary black hole}} mergers are detectable with the current setup. The proposed {{w|LISA Pathfinder}} spacecraft will be able to see things like orbiting black holes and {{w|neutron stars}}. Since the Fixion intercepts gravity waves before they are observed we should not get our hopes up too high about observing any even with LISA.
|| Let's wait for the LISA data before jumping to conclusions.
|-
| Causes coronal heating
|| No arrow – but the text is situated next to the middle of the three wavy lines going right.
|| For some reason the outer layer of the {{w|sun}} (the {{w|corona}}) is hotter than most reasonable theories predict. This is for instance mentioned in Randall’s new book ''[[Thing Explainer]]'' in the entry about the sun. This can also be seen on the [[Thing_Explainer#Preview Pages |back cover of the book]]. The phenomenon is explained by the Fixion…
|| It's a mystery, but it possibly has something to do with waves in the corona (for example, the {{w|High Resolution Coronal Imager}} has seen "braids" in the corona that whip around and unravel themselves).
|-
| Higgs-ish
|| As this is just a property of the Fixion there is no arrow.
|| The {{w|Higgs boson}} is a manifestation of the Higgs field... but many supersymmetry and string theories predict multiple Higgs-like particles. It's almost a prerequisite of any new theory that it has a Higgs-ish element. So the Fixion blends in with this.
|| N/A
|-
| Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find)
|| An arrow points to the point of the main line just below the bottom space probe.
|| The {{w|Cosmic Microwave Background}} (CMB) is incredibly uniform. In fact it is so uniform that the conclusion is that these areas must have been in contact at some time in the early universe. But with the universe being infinite, and the speed of light being finite, most parts of the universe will never be able to interact (anymore at least). The explanation usually given for the uniformity is that the universe expanded really fast in the beginning during what is called the {{w|Inflationary epoch}}. {{w|BICEP_and_Keck_Array#BICEP2|BICEP2}} is a {{w|radio telescope}} at the South Pole whose operators claim to have seen polarization in the CMB indicative of inflation. (See [[1365: Inflation]] that references BICEP2's results). The Fixion fixes the problem since it allowed {{w|Faster-than-light|superluminally}} smoothing of the early anisotropies to explain the smoothness observed today. The Fixion has left just enough signal that the new {{w|BICEP_and_Keck_Array#BICEP3|BICEP3}} telescope will be able to find them.
|| As stated, {{w|Inflation (cosmology)|inflation}} is the standard explanation and it holds up fairly well. Other studies haven't seen the polarization that BICEP2 has - the {{w|Planck (spacecraft)|Planck space telescope}} also suggests that the BICEP2 team were looking at an unusually dusty bit of space, which could cause polarization. Hopefully this will improve with the BICEP3 data that should be published in 2016.
|-
| Accelerates certain spacecraft during flybys
|| Two arrows point to two solid lines going away from the main line (left and right). At the end of each line there is a space craft with satellite dish and solar panels, representing the items that the Fixion interacts with.
|| This refers to the {{w|flyby anomaly}} which is sometimes (but not always) seen when spacecraft fly close to planets and pick up more speed than expected. It's not always seen – for instance the {{w|Rosetta (spacecraft)|Rosetta space probe}} had no flyby anomaly when it swooped extremely close to Mars. Another anomaly for spacecraft’s (a deceleration this time) has been mentioned in the title text of [[502: Dark Flow]].
|| It could be an unpredicted quirk of gravity and relativity... or it could be experimental error.
|-
| Triggers Siberian sinkholes
|| No arrow, but it is right next to the solid line with an arrow going into the main line just before the first hole where the main line disappears and becomes dotted. Thus it could be a reference also to these holes.
|| Recently, (2014), several {{w|sinkholes}} opened up in {{w|Yamal_Peninsula#Yamal_craters |remote parts}} of Siberia. The explanation is currently unknown, except of course we now know that it was the Fixion that caused it.
|| While there are lots of weird theories, there's a good chance they were caused by {{w|Arctic methane release}} due to melting {{w|permafrost}} which is probably caused by {{w|global warming}}. See ([http://www.independent.co.uk/news/science/mystery-of-the-siberian-holes-at-the-end-of-the-world-solved-scientists-offer-explanation-9642988.html Mystery of the Siberian holes… solved]).
|-
| Melts ice in "Snowball Earth" scenario
|| No arrow.
|| {{w|Snowball Earth}} is the theory that the whole planet was covered in ice at some point. To melt all that ice by the {{w|greenhouse effect}} would require far more carbon dioxide in the atmosphere than seems plausible. However, if volcanoes were to deposit black soot on the surface of the ice, it would start absorbing heat more efficiently (in scientific terms, the Earth's {{w|albedo}} would decrease) and that would also make the planet heat up. Of course it was the Fixion was the cause of the melting ice.
|| There are {{w|Snowball_Earth#Scientific_dispute|scientific dispute}} regarding the theory for a Snowball Earth. There is no conclusive evidence that it ever occurred, but those in favor has presented lots of {{w|Snowball_Earth#Evidence|evidence}}…
|-
| Transports neutrinos faster than light, but only on certain days through one area of France
|| An arrow points to the part of the main line that becomes dotted between the two “{{w|wormholes}}”. This is where the neutrinos move faster than light…
|| Refers to the {{w|faster-than-light neutrino anomaly}}, where it seemed that a neutrino beam from {{w|CERN}} on the France/Switzerland border to the {{w|OPERA experiment}} in Italy traveled faster than light. Scientists were not able to reproduce the result. Of course it was because of the Fixion. This Neutrino experiment was also mentioned in [[955: Neutrinos]], where there are more explanation on the subject.
|| In the end, there was no mystery, just a [http://www.redorbit.com/news/science/1112551696/cern-confirms-neutrinos-not-faster-than-light/ defective cable causing a measurement error].
|-
| Suppresses sigma in experiments
|| No arrow but the last solid line, with an arrow pointing left, that is going away from the main line, point almost directly at it.
|| Sigma (σ) refers to the {{w|standard deviation}} - a mathematical measure of how much an observed value differs from the expected value. For a formal scientific discovery in particle physics, the standard is 5 sigma which means that there is about a 1 in 3.5 million chance that the results were caused by random errors (of course, they could be caused by ''systematic'' errors, such as measurement problems). Some tantalizing experiments have found interesting results at 3 or 4 sigma but either can't reach 5 sigma or {{w|Oops-Leon|are subsequently dis-proven}}. The question is, if the way the Fixion works here in this comic pushes the sigma value one way or the other? Does it suppress the value so it goes below or above the level of significance? Is it artificially pushed in the direction so a result seems like it is significant when it is not (see for instance [[882: Significant]]), or if it is the other way so some experiments, which could have found what the experimenters wanted to find, did not because the sigma has been artificially lowered below the proof threshold. Either way it is a very annoying fact of the Fixion, but it would explain a lot, and probably also make it very hard to find the Fixion because of this intrinsic behavior.|| N/A
|-
| My theory predicts that, at high enough energies, FRBs and perytons become indistinguishable because the detector burns out.
|| From the title text.
|| This is a continuation of the joke already mentioned above regarding Fast radio bursts (FRBs) and perytons. GUTs normally predict that all the forces we see are the different low-energy versions of a single force which can only be seen at extremely high energies (much higher than any Earth-based collider could produce). A high-energy FRB would be a {{w|gamma ray burst}} and if it came from a close enough object, would obliterate all life on Earth... It would also wreck the sensitive electronics at Parkes Observatory. This "high energy unification" is stated in a way reminiscent of the unification of electromagnetic and weak forces at high energies; but unlike the latter, it involves two things only "appearing" (or, in this case, not appearing) to be the same, not actually becoming the same.
|| N/A
|}

==Transcript==
:[Caption above the panel:]
:A Christmas gift for physicists:
:The '''Fixion'''
:A new particle that explains everything

:[A chart resembling a Feynman diagram is shown. It begins with a solid line coming down at the top, going a little to the left. The line continues downwards all the time, but changes direction 16 times before exiting at the bottom almost straight under the starting point. At every point where it changes direction, there is some kind of “interaction” with something outside this line. There are 19 phrases, 10 on the left and 9 on the right. 11 of these are distinct labels for points on the line as 14 gray curved arrows points between these 11 phrases to specific points on the line. Three of the phrases on the left has two arrows pointing to two different, but close, parts of the line. The main central line is solid all the way, except at the very bottom, where it “disappears” inside a hole only to “reappear” later from a similar hole. Between these two holes the line is dotted. The lines going away (or to) the main line can be straight and solid, straight and dotted, wavy lines (with different waviness), even looking like a spiral. Two straight solid lines ends up at two space probes, and finally the last two straight solid lines coming in (and out) on either side of the “hole” in the line has arrow pointing in and out. Below the phrases will be listed in reading order, taking one on each side alternatingly. Above each is described if there are any arrow and, if there are, what they points at.]

:[Left: Arrow pointing to the very first part of the main line:]
::Main component of dark matter

:[Right: Arrow pointing to the very first part of the main line, but below the previous arrow:]
::Confines quarks and gluons

:[Left: Arrow points to the first solid line going left and upwards:]
::Neutralizes monopoles

:[Right: No arrow:]
::Suppresses antimatter in early universe

:[Left: Two arrows points to two dotted lines going out left and downwards below the first solid line:]
::Spontaneously emits dark energy

:[Right: Arrow pointing to several lines going almost parallel with the main line. The first line closest to the arrow is not connected with the main line. It bends closer to the other lines in the middle. The next line is connected to the main line, and is thus actually two lines going in to the main line. The same goes for the inner line, where there is some distance between the entry and exit, as the middle of these three lines connect to the main line in between. In principle there are four lines going in/out and one not connected, but it looks like three lines:]
::Mediates proton decay but then hides it

:[Left: One arrow points to the first wavy line (7 peaks) coming out and up towards the dotted lines above. A second arrow points further down the main line where there are three more wavy lines coming out, but to the right, they are all of the same length and go almost straight right, only a little down. The first has as short a wave length as the line above to the left, but as it is shorter it only has 6 peaks. Then the wavelength decreases to a very long one for the last, 5 peaks and then 3 peaks. The arrow points almost where the middle wavy line exits the main line:]
::Introduces dispersion in perytons from kitchen microwaves, explaining fast radio bursts

:[Right: An arrow point to the part of the main line between the three parallel lines and the first wavy line:]
::Broken symmetry causes ϴ=0, explaining unobserved neutron dipole moment

:[Left: No arrow:]
::Causes alpha effect

:[Right: No arrow, but right next to the middle of the three wavy line:]
::Covers naked singularities

:[Left: An arrow points to a spiraling line going upwards to the left:]
::Intercepts certain gravitational waves before they're observed.

:[Right: No arrow, but right next to the bottom of the three wavy line:]
::Causes coronal heating

:[Left: No arrow:]
::Higgs-ish

:[Right: A long arrow point to the point of the main line just below the line pointing to the bottom (and left) of the space probes:]
::Superluminally smooths anisotropies in early universe (but adds faint polarization for BICEP3 to find)

:[Left: One arrows point towards the point on the main lines where a solid line goes to the right and up and another arrow points on another solid line going away from the main line towards left and down. At the end of both lines are drawn spacecrafts with satelite dish and solar panels:]
::Accelerates certain spacecraft during flybys

:[Right: No arrow, but right next to the solid line with an arrow going into the main line just before the first hole where the main line disappears and becomes dotted:]
::Triggers Siberian sinkholes

:[Left: No arrow:]
::Melts ice in "Snowball Earth" scenario

:[Right: Arrow points to the dotted part of the main line between the two holes:]
::Transports neutrinos faster than light, but only on certain days through one area of France

:[Left: No arrow but the last solid line, with an arrow pointing left, that is going away from the main line, point almost directly at it:]
::Suppresses sigma in experiments

{{comic discussion}}

[[Category:Christmas]]
[[Category:Charts]]
[[Category:Science]]
[[Category:Astronomy]]
[[Category:Physics]]
[[Category:Space]]
[[Category:Puns]]
[[Category:Language]]
[[Category:Portmanteau]]

1541: Voice

2015-06-26T21:08:56Z

Shadowfax37:

{{comic
| number = 1541
| date = June 22, 2015
| title = Voice
| image = voice.png
| titletext = Anyway, we should totally go watch a video story or put some food in our normal mouths!
}}

==Explanation==
During a casual talk with [[Megan]], [[Ponytail]] suddenly interrupts her normal speech stating that she is for some reason only capable of controlling her own voice once every six years. Apparently only for a very brief time since she immediately returns to the casual talk, continuing her previous sentence mid-word before being able to tell Megan how she could help her. Upon Megan's confused request, she denies knowledge of the occurrence, although in a somewhat suspicious way, using a possibly fake laughter.

It could be this was just a prank by Ponytail, to tease Megan, but given her fake laughter reply to Megan's inquiry and the continuing comment in the title text it seems most likely that Ponytail is indeed possessed by some sort of entity that prevents her from expressing her own thoughts, except for a very short time every six years. Of course this may just be her way of continuing with the prank... (see a previous case of such a prank [[#Voice hijacking|below]]).

In case it is not a prank it would thus appears that Ponytail's usual "self" is indeed this possessing entity. Whether this entity is actually aware that the "real" Ponytail did speak, or if it actually does not know that it was interrupted (since it continued mid-word) is not clear from the last response to Megan.

The title text suggests that Ponytail is possessed by some sort of inhuman entity, most likely an alien or {{w|AI}}, unfamiliar with movies and eating. See below for [[#Related comics|related comics]].

===Related comics===
====Non human entity trying to behave like a human====
The recent comic, [[1530: Keyboard Mash]], also revolves around the same theme of a non human entity trying to convince other humans that it is in fact a human. This is most clearly referenced in the title text of this comic. In Keyboard Mash, it is a spider that tries to chat like it was a human, making statements that are true if you are human, but which humans would never utter in a conversation like here - ''put some food in our normal mouths!'' However, the pretended 'human' being (the spider) is not seen by the other person in this comic. As opposed to this one where Megan speaks directly with Ponytail.

====Voice hijacking====
It has already been established recently, in [[1528: Vodka]], that Ponytail's voice can be hijacked by non-human entities. That time it was the vodka she was drinking that took over. It is possible that this is continuing or caused by the same openness to possession as shown here. It is also possible that she simply thinks possession jokes are funny and once again jokes with Megan.

====Six years ago====
Six years ago today, which according to this comic was the last time Ponytail had control of her own voice, this comic [[600: Android Boyfriend]] was posted. Ponytail acquired an android boyfriend. It seems unlikely that this older comic has any relation with this particular episode - except that this comic mentions a six-year period and Ponytail is also in that comic.

====Note on Ponytail====
''Ponytail is mainly a filler character, showing up when two females are needed or when a large group of people are present.''

This means the character in this comic may or may not be the same as the Ponytail in other comics. (As for most xkcd characters without hats. Those [[:Category:Characters with Hats|''with'' hats]] usually behave the same way from comic to comic.)

==Transcript==
:[Megan and Ponytail are walking.]
:Megan: Are you doing anything later?
:Ponytail: I was th- ''I can only control my voice once every six years. Please, you have to'' -inking of going out, but no real plans.
:Megan: ...What was that?
:Ponytail: Haha, what?

==Trivia==
*{{w|Demonic possession|Possession}} stories are common in films and books. Some recent examples that could have inspired this comic could be one of these (beware of '''spoilers'''):
**In the film {{w|The Host (2013 film)|The Host}} the human race has been taken over by small parasitic aliens called "Souls" that inserts themselves individually into a host body where they are then able to access the host's memories. In the story the main character is the host that controls a body, and then the personality of that body, which is then no longer able to control her body, but can speak to the host. And in a few situations can take over her body for a short period. Very similar to what happens in this comic.
**The Yeerks from the {{w|Animorphs (TV series)|Animorphs}} TV series take humans as a host by entering and merging with their brain through the ear canal. In some situations this merger is not complete. (The Animorph series were referenced previously in [[1380: Manual for Civilization]].)
**In the movie {{w|Being John Malkovich}} the main character possesses Malkovich, but Malkovich is occasionally able to communicate through the possession.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]