explain xkcd - User contributions [en]

2284: Sabotage

2020-03-23T18:02:26Z

172.68.141.184: /* Explanation */

{{comic
| number = 2284
| date = March 23, 2020
| title = Sabotage
| image = sabotage.png
| titletext = So excited to see everyone after my luxury cruise home from the World Handshake Championships!
}}

==Explanation==
{{incomplete|Created by a WILD SKUNK WITH CORONAVIRUS. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

This comic, once again, returns to the subject of "the [[:Category:COVID-19|coronavirus]]" (specifically the strain designated as COVID-19 or SARS CoV-2).

In the wake of the virus, the advice from many professionals is to avoid public gatherings to slow the spread of the virus and "flatten the curve".

Vandalism

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

:[Cueball is seated at a desk, typing on a laptop. The top half of the image is the text he is typing in a reply message:]
:"I see you're still getting together today! I'll be there, doing my spoken-word ''Baby Shark'' karaoke all evening.
:We'll also be setting up a petting zoo for the kids. We've spent all week trapping wild skunks!"
:[Below the text is a white on green "reply" button.]
:[Caption below the panel:]
:In the Coronavirus era, desperate times call for desperate measures.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:COVID-19]]

2262: Parker Solar Probe

2020-01-31T21:25:17Z

172.68.141.184: Add animation of Parker Solar Probe trajectory.

{{comic
| number = 2262
| date = January 31, 2020
| title = Parker Solar Probe
| image = parker_solar_probe.png
| titletext = It will get within 9 or 10 Sun-diameters of the "bottom" (the Sun's surface) which seems pretty far when you put it that way, but from up here on Earth it's practically all the way down.
}}

==Explanation==
{{incomplete|Created by a FRIED ROBOTIC SOLAR PROBE. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
This is an informative comic meant to represent the relative distances of astronomical objects relative to the {{w|Parker Solar Probe}}. It also shows where the probe will be in 2025 if its mission continues going according to plan.

The Parker Solar Probe is a robotic spacecraft launched by NASA in 2018 with the mission of repeatedly probing and making observations of the outer corona of the Sun. It travels in an elongated orbit that passes close to the Sun and sometimes passes near Venus, arranged such that Venus nudges the orbit slightly in each pass to bring the probe's perihelion (the lower end of its orbit) closer and closer to the Sun. By the end of the probe's planned lifetime in 2025, it will pass within 4.3 million miles (6.9 million km), or about 5 solar diameters, of the Sun's surface, at a speed of 430,000 mph (690,000 km/h). Two days before this comic was published {{w|Parker_Solar_Probe#Timeline|the probe again passed through perihelion}}, establishing new records for closeness to the Sun and speed.

{{w|Helios (spacecraft)|Helios 2}} was a solar probe launched in the 1976 that formerly held the records for closest man-made object to the Sun and fastest man-made object. Both records were surpassed in 2018 by the Parker probe.

[[File:Animation of Parker Solar Probe trajectory.gif|thumb|right|Animation of Parker Solar Probe's trajectory from August 7, 2018 to August 29, 2025 {{Color|magenta|Parker Solar Probe}} • {{Color|RoyalBlue|Earth}} • {{Color|Cyan|Venus}} • {{Color|Lime|Mercury}} • {{Color|#dbd81d|Sun}}]]

Cueball and Megan are standing on Earth. The way this diagram is drawn, they look like they could fall off Earth toward the Sun -- hence the comment "Careful!" -- though the joke is that in real life they would fall toward the center of the Earth, not toward the Sun.

The title text says the probe will get within 9 or 10 Sun-diameters of the Sun's surface. This is a bit of a mistake: it will actually get {{w|Parker Solar Probe|within that many Sun-''radii''}} -- only 4½ or 5 Sun-diameters.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
Caption above: Looking down toward the Sun and the Parker Solar Probe (distances are to scale, sizes are ''not'' to scale)

Earth, with Cueball and Megan standing "on top" [with their feet lower on the page, toward the Sun]

:Cueball: Careful!

Venus

Mercury

Helios 2
(1976)

Parker Solar Probe
(today)

Parker Solar Probe
(2025)

The Sun (not to scale)

{{comic discussion}}

Talk:2186: Dark Matter

2019-08-10T01:01:51Z

172.68.141.184: replies

If dark matter were squirrels, they ''wouldn't'' set off the bird feeders because dark matter can't interact with feeders at all! Especially since it's not to the squirrels' advantage to set them off. Unless, of course, the dark matter squirrels do exist and steal from our feeders freely, but we can't notice because dark matter is unobservable at this scale. In fact, it's entirely plausible that some squirrels evolved to be dark matter for this specific advantage, so I wouldn't rule that out. [[Special:Contributions/172.68.244.174|172.68.244.174]] 12:12, 7 August
2019 (UTC)
:Well if they can't interact with the feeders, they won't be able to steal the food either.[[Special:Contributions/141.101.107.66|141.101.107.66]] 13:28, 7 August 2019 (UTC)
::Not with that attitude. [[Special:Contributions/162.158.126.4|162.158.126.4]] 14:10, 7 August 2019 (UTC)

I have never seen a spinning bird - can they turn peanuts into gold?
:Yes, but the gold would be radioactive. The much more impressive reaction is to turn gold into peanuts, other than by paying a farmer for peanuts using the gold. [[User:Nutster|Nutster]] ([[User talk:Nutster|talk]]) 14:36, 7 August 2019 (UTC)
::Would I be allowed to pay a merchant for peanuts using the gold? --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 14:38, 7 August 2019 (UTC)

I had to google what a spinning bird feeder is. I had never seen one of these before (I live in Germany). Maybe a link to one of these funny videos should be added. Frank [[Special:Contributions/172.68.110.64|172.68.110.64]] 19:59, 7 August 2019 (UTC)
:{{done}} [[Special:Contributions/172.69.22.32|172.69.22.32]] 01:25, 8 August 2019 (UTC)

Anyone else who read PBH as PHB, the pointy haired boss from Dilbert? --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 07:06, 8 August 2019 (UTC)
:I always think "peanut butter and ham," from PBJ+BLT I guess. [[Special:Contributions/172.68.141.148|172.68.141.148]] 07:20, 8 August 2019 (UTC)

In the explanation, I think I missed a step of logic. Are Windows, Icons, Mice and Pointers made up of Dark Matter? It might explain a few lockups in Windows I've been having lately.[[User:Seebert|Seebert]] ([[User talk:Seebert|talk]]) 11:47, 9 August 2019 (UTC)

How can Megan use the dark matter density across the whole solar system to calculate the density within the Earth? If dark matter interacts with gravity, shouldn't the distribution of dark matter within the Solar system be similar to the distribution of normal matter (i.e. much higher density near massive objects like the Earth)? [[Special:Contributions/108.162.241.124|108.162.241.124]] 17:40, 9 August 2019 (UTC)
:It interacts with gravity, but in doing so it falls into and through ordinary mass and then just keeps going -- gravity isn't strong enough to slow it down enough to make it bunch up around normal matter. Only galaxies have discernible halos clumped. Most dark matter particles that fall into our solar system would just fall out the other side at the same speed, tossing them into the gravity of another star before they slow down enough to come back, in most cases. The linked density paper talks about the extent of that effect as the basis of their calculations. [[Special:Contributions/172.68.141.184|172.68.141.184]] 01:01, 10 August 2019 (UTC)

For comparison, it would be nice to have the average density of "regular" matter of the earth, the sun, interplanetary space, interstellar space, etc. --[[Special:Contributions/141.101.105.246|141.101.105.246]] 18:59, 9 August 2019 (UTC)
:It's a little less than one fifth overall. However, you can't really have a local density of normal matter because it's clumped into stars and planets. Even at our scale, what's underneath is almost certainly far more dense than what's above you. [[Special:Contributions/172.68.141.184|172.68.141.184]] 01:01, 10 August 2019 (UTC)

2172: Lunar Cycles

2019-08-08T22:32:55Z

172.68.141.184: /* Explanation */ pork to the left of dire

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*'''Pork''' {{w|Mooncake|'''moon'''cakes}} have been prepared over a thousand years in the rural areas west of Shanghai for the Chinese {{w|Mid-Autumn Festival}}.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:30:53Z

172.68.141.184: /* Explanation */ thousand+ year tradition

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*'''Pork''' {{w|Mooncake|mooncakes}} have been prepared for over a thousand years in the rural areas west of Shanghai for the Chinese {{w|Mid-Autumn Festival}}.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:27:43Z

172.68.141.184: /* Explanation */ better bold/link

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*'''Pork''' {{w|Mooncake|mooncakes}} are traditionally prepared in the rural areas west of Shanghai for the Chinese {{w|Mid-Autumn Festival}}.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:26:19Z

172.68.141.184: /* Explanation */ precision

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*'''Pork moon'''cakes are traditionally prepared in the rural areas west of Shanghai for the Chinese {{w|Mid-Autumn Festival}}.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:24:22Z

172.68.141.184: /* Explanation */ fix formatting, substitute more common geography

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*'''Pork moon''' cakes are traditionally prepared in rural areas outside Shanghai for the Chinese {{w|Mid-Autumn festival}}.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:22:11Z

172.68.141.184: /* Explanation */ pork mooncakes, yum!

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*'''Pork moon'' cakes are a traditional food prepared in the {{w|Suzhou}} region for the Chinese {{w|mid-autumn festival}}.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:18:27Z

172.68.141.184: /* Explanation */ unbold link

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A [[wikipedia:blood moon|blood moon]] refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*There are no occurrences of '''pork moon''' in the Google Books N-Gram viewer, which includes many works from the 1800s through 2008.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2172: Lunar Cycles

2019-08-08T22:16:45Z

172.68.141.184: /* Explanation */ reorder left-to-right, add MtG dire moon card

{{comic
| number = 2172
| date = July 5, 2019
| title = Lunar Cycles
| image = lunar_cycles.png
| titletext = The Antikythera mechanism had a whole set of gears specifically to track the cyclic popularity of skinny jeans and low-rise waists.
}}

==Explanation==

This comic shows a mixture of real, scientific lunar cycles and cycles that are comedic or fictional in nature.

*'''Nodal precession:''' The Moon's orbital plane is tilted slightly compared to the Earth's orbital plane around the sun (the {{w|ecliptic}}). This tilt is why we don't constantly see eclipses; most of the time, the Moon's orbital plane is tilted higher or lower than the Sun, so they generally don't cross each other. The two points at which these planes ''do'' cross are called {{w|lunar nodes}}. {{w|Nodal precession}} is the gradual rotation of these nodes over time, which for the Moon follows an 18.6 year cycle.

*'''Apsidal precession:''' All orbits have two points where the orbiting body is either closest to, or furthest away from, the thing they are orbiting. These points are called {{w|apsides}}, and the imaginary line between them is called the ''line of apsides''. {{w|Apsidal precession}} is the gradual rotation of this line over time, which occurs in cycles of around 8.9 years for the Moon.

*'''Phase:''' {{w|Lunar phase}} describes the change in shape of the sunlit side of the Moon as viewed from the Earth's surface, which is caused by the changing angle between Moon and Sun as the Moon revolves around the Earth. The cycle of lunar phases takes 29.5 days, a figure referred to as the ''synodic month''.

*'''Distance:''' Because the Moon's orbit around the Earth is elliptical, its distance from the Earth varies slightly over the course of an orbit. This means that the moon's distance also follows a cycle which is the same as the length of one lunar orbit: approximately 27.5 days. This figure is referred to as the ''anomalistic month''. Note that the synodic month is (perhaps counterintuitively) two days ''longer'' than the sidereal month - or to put it another way, it takes 2 more days for the Moon's phases to cycle than it does for the Moon to go around the Earth. This is due to the fact that the Earth is also moving ''around'' the Sun while the phases are going on, which means that the Moon has to spend 2 extra days "catching up" to the point at which the lunar phase cycle can restart.

*'''Earth-Moon relative size''': This is a joke cycle; the Earth and Moon do not physically change size, nor does the Moon ever become larger than the Earth. This may be playing on the idea that the Moon often ''appears'' to change size to viewers on Earth, due to various factors; most commonly, this is due to the {{w|Moon illusion}}, which tricks the brain into perceiving the Moon as much larger than it really is. There are also so-called {{w|supermoon}}s, which occur when the full moon coincides with the Moon's closest approach to Earth; these actually do increase the Moon's apparent size, although by a relatively insignificant amount.

*'''Lunar shape:''' Again, this is a joke cycle; the Moon does not actually change shape. A shape intermediate between circle and square is known as a {{w|squircle}}, a subclass of the {{w|superellipse}}.

*'''Lunar mood:''' The moon does not have a mood, although humans can have moods that fluctuate over time, sometimes with a regularity akin to a cycle. Ironically, the section of the graph that shows a good (i.e. happy) mood has the graph line curving up then down like the mouth of a frown, and for the bad (unhappy) mood it curves down and then up, as in the mouth of a smile.

* The final diagram shows many different cycles superimposed on each other, highlighting areas where several cycles are coinciding. This is likely satirizing the media trend of overhyping astronomical coincidences and giving them grand-sounding names:
:*The light gray "phase × distance" plot does not correspond to the product of periods given for phase and distance, which [https://i.imgur.com/0i0mcPn.png look like this] instead.
:*A [[wikipedia:harvest moon|harvest moon]] is the traditional name for the full moon closest to the autumnal equinox, but there is nothing astronomically significant about it.
:*A [[wikipedia:Supermoon|supermoon]] is a full or new moon when the Moon is closest to the Earth, resulting in a slightly larger-than-usual apparent size. A full supermoon is roughly 14% larger in diameter than when the Moon is furthest away. See also [[1394: Superm*n]].
:*A [[wikipedia:blue moon|blue moon]] is the extra full moon in years with 13 full moons, which happens once every two or three years (hence the phrase "once in a blue moon"). Blue moons don't look any different from regular full moons.
:*A '''[[wikipedia:blood moon|blood moon]]''' refers to the moon during a lunar eclipse.
:*While the popularity of '''skinny jeans''' ([[wikipedia:Slim-fit pants|slim-fit pants]]) does change over time, the idea that this is connected to a lunar cycle is also a joke.
:*The [[wikipedia:Golden Age of Television|Golden Age of Television]] is said to have occurred in the 1940s and 50s, and the 2000s.
:*[https://scryfall.com/card/m20/120/vampire-of-the-dire-moon "The Vampire of the '''Dire Moon'''"] is a recently introduced, uncommon card from the {{w|Magic: The Gathering}} card game.
:*There are no occurrences of '''pork moon''' in the Google Books N-Gram viewer, which includes many works from the 1800s through 2008.
:*{{w|Astrology}} is a pseudoscience which claims that the positions of the celestial bodies can be used to predict human affairs. The chart jokingly suggests that astrology actually ''does'' work, but only within a very specific two-week timeframe.
:*Finally, while the idea of a '''total eclipse of the sea''' seems absurd, [https://www.deepseanews.com/2017/08/what-happens-in-the-sea-during-a-solar-eclipse/ an eclipse was famously used to explain the migration of maritime animals]:
:::''biologists were beginning to unravel the mystery of this ‘false bottom’–a layer in the ocean that looks the the sea floor on the sounder but isn’t–which covered much of the ocean. This false bottom rises in up at night and sinks down during the day. This rising and falling is in fact caused by the largest migration of animal on Earth–everything from fish, shrimp and jellyfish, moving hundreds of meters in unison up and down each day.... the moon moved into its place in front of the sun, daylight rapidly faded, and the scientists solved the migration mystery: the deep layer of animals began to rise. Bioluminescent creatures started to shine, and nocturnal creatures started a frantic upward thrust. As the world grew darker, they swam upward nearly 80 meters. But this frantic migration didn’t last long. As the moon receded and the sun revealed itself, the massive animal layer did an about-face, scrambling back into the safety of the darkness.''
:: (Backus, Clark, and Wing (1965) [https://sci-hub.tw/10.1038/205989a0 "Behaviour of certain marine organisms during the solar eclipse of July 20, 1963"] ''Nature'' '''4975:'''989-91.)
The '''{{w|Antikythera_mechanism|Antikythera mechanism}}''' mentioned in the title text is an ancient Greek machine, rediscovered in 1901, designed to calculate astronomical positions. The title text jokes that there is a set of gears on said mechanism that is used to predict the popularity of "skinny jeans" and "low-rise waists." Since it was likely created in the 1st or 2nd century B.C., it is impossible for the creators to have had any knowledge of skinny jeans or low-rise waists - both are modern-day clothing fashions.

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

:Understanding lunar cycles

:Nodal precession
:[A diagram showing a broad cosine-like wave with wavelength labelled as 18.6 years. To the right are two diagrams showing an orbital cycle moving in and out of plane.]

:Apsidal precession
:[A diagram similar to the one above but with a slightly shorter wavelength, labelled as 8.9 years. To the right are two diagrams showing an elliptical orbit around a planet and the same orbit rotated.]

:Phase
:[A diagram similar to those above with a shorter wavelength, labelled as 29.5 days. To the right is a diagram showing four phases of the moon: New, Waxing crescent, Waxinf gibbos, Full.]

:Distance
:[A diagram similar to those above with a shorter wavelength, labelled as 27.5 days. To the right is a diagram showing the distance of the moon from the Earth over time, with distances marked by arrows.]

:Earth-Moon relative size
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Earth bigger' and an arrow pointing to the maximum labelled 'Moon bigger'. To the right are two diagrams of the moon and Earth, one showing the Earth bigger than the Moon and the other showing the Moon bigger than the Earth.]

:Lunar shape
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Circle' and an arrow pointing to the maximum labelled 'Square'. To the right is a diagram showing a circle, a circle transforming into a square with outward arrows at each corner and a square transforming into a circle with inward arrows.]

:Lunar mood
:[A wave with long wavelength with an arrow pointing to the minimum labelled 'Bad' and an arrow pointing to the maximum labelled 'Good'. To the right are four emojis: :), :|, :(, :|]

:[A superimposed graph of all the above waves. Different points on the graph are labelled: Harvest moon, Supermoon, Blue moon, Skinny Jeans popular, Super blood moon, Golden age of TV, Dire moon, Pork moon, Two week window in which astrology works, Total eclipse of the sea.]

{{comic discussion}}

2186: Dark Matter

2019-08-08T21:59:53Z

172.68.141.184: /* Explanation */ s/issue/mystery

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
{{incomplete|Created by a DARK MATTER SQUIRREL ON A SPINNING BIRD FEEDER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly in the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the Earth. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass necessary for [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them], enraging Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Megan's figures imply that a {{w|squirrel}} has a mass of 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams] (about 1.3 lb), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for the composition of dark matter. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this mystery, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were atomic nuclei, to detect dark matter particles like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels.)

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]

2186: Dark Matter

2019-08-08T21:59:07Z

172.68.141.184: /* Explanation */ rm comma

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
{{incomplete|Created by a DARK MATTER SQUIRREL ON A SPINNING BIRD FEEDER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly in the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the Earth. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass necessary for [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them], enraging Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Megan's figures imply that a {{w|squirrel}} has a mass of 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams] (about 1.3 lb), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for the composition of dark matter. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this issue, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were atomic nuclei, to detect dark matter particles like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels.)

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]

2186: Dark Matter

2019-08-08T21:58:17Z

172.68.141.184: /* Explanation */ reorder title text explanation at end, where it dovetails

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
{{incomplete|Created by a DARK MATTER SQUIRREL ON A SPINNING BIRD FEEDER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly in the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the Earth. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass necessary for [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them], enraging Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Megan's figures imply that a {{w|squirrel}} has a mass of 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams] (about 1.3 lb), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for the composition of dark matter. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this issue, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were atomic nuclei, to detect dark matter particles, like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels.)

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]