explain xkcd - User contributions [en]

2310: Great Attractor

2025-09-13T10:39:38Z

86.13.226.126: /* Explanation */

{{comic
| number = 2310
| date = May 22, 2020
| title = Great Attractor
| image = great_attractor.png
| titletext = Living in the southern hemisphere was nice because I could jump extra high, but I like it here too. Besides, if I ever want to move back, I can just curl up in a ball and wait!
}}

==Explanation==
[[Cueball]] comments on the fact that as summer approaches, the sun rises earlier and sets later, a common topic of conversation, especially to complain that it is still light at times of day where you are used to it being dark out. [[Beret Guy]] comments that he fell off of the wall this morning, a seemingly unconnected topic.

People will often complain about falling out of bed as an indicator of having slept badly. The later sunset is [https://www.insider.com/why-its-hard-to-sleep-in-the-summer-2018-6 often linked to worsened sleep]. However, Beret Guy didn't fall from the bed, he fell from the wall. While being able to figure out he's talking about his worsened sleep, Cueball is understandably confused, so Beret Guy clarifies.

Beret Guy is strongly affected by the {{w|Great Attractor}}, a large gravitational anomaly that influences the galaxies near it, but is difficult to observe directly. Beret Guy claims that the Great Attractor pulls on him unusually hard, which could be another one of his [[:Category:Strange powers of Beret Guy|strange powers]]. This attraction, while not overpowering the gravity of the Earth, (he states in the title text that he can "Jump extra high" when it is above him) affects his life greatly.

For Beret Guy his attraction to the Great Attractor means that, at various times, like now, he can lie on the vertical surface of any wall (external or internal) that is currently oriented in a fortuitous direction (i.e. facing north). He fell off the wall this morning due the Great Attractor being below him during daylight hours and on the horizon during night hours. Thus, Beret Guy's complaint in the first panel comes across as an attempted solidarity with Cueball's complaint; he was still asleep when the Great Attractor moved to below him, causing him to fall off the wall and presumably awaken him. The Great Attractor reaches the same apparent location once in a stellar day which is about four minutes shorter than the solar day. This means Beret Guy would only be able to sleep on walls for certain part of the year, as the time of day when the Great Attractor is near the horizon would occur 4 minutes earlier each day.

He gives a short explanation of which Attractor he refers to (the space one) and why the Great Attractor affects him. According to his doctors it is apparently caused by the motion of galaxies and how many dimensions his bones have. Since having fewer than 3 spatial dimensions may lead to trouble, his bones may be existing in more dimensions than our normal 3 dimensions of space and 1 of time. Galactic motions normally have no significant effect on a person with 3-D bones.{{Citation needed}}

Beret Guy then says that day-sliding season is near, due to the Great Attractor being at the horizon in the day, and offers to run errands for Cueball in the South, implying that he will be pulled towards the south during day-sliding season, and can run much faster in that direction. Since the Great Attractor is in the southern half of the night sky, in most parts of the world it will usually pull Beret Guy roughly towards the South.

Beret Guy is not standing straight up during this comic, he has one knee slightly bent towards Cueball in the first two panels. This is because it is evening (8:00 PM as Cueball states) and the Great Attractor is now coming near the horizon, where it will be during the night. So Beret Guy will be pulled towards the south, behind him in the comic, and thus leans away from the pull. In the final panel, when he leaves Cueball, moving right towards south and into the pull, he can be seen sliding along the ground without walking. He leans a bit back to not stumble forward. His last sentence also indicates that he either speeds up or that he is a little uncertain on his feet altering his voice.

He mentions that at the moment during day-time the Great Attractor is beneath him so he can stand straight. He then just feels a little heavier (he will thus weigh more than another person with the same mass).

In the title text he says he liked living in the south because the Great Attractor was often above him, meaning he could jump higher with the help of its pull (and would weigh less than a normal person with same mass). Since he could jump, the force is clearly weaker than Earth's gravity, but still enough for him to easily slide over the ground when it is near the horizon. So he could likely win some high-jump or long-jump competitions if he chose the right time and place.

Being Beret Guy, he is never really unhappy, so he states that he also likes it here (in the north). But then he continues to comment on how easy it will be for him to get to the south. Because if he entirely stopped bracing himself against the pull by crouching into a more spherical shape, and just waited for the Great Attractor to get near the horizon again, then the pull would cause him to start rolling over the ground to some place with lower net gravitational potential, i.e. further south, where the Great Attractor will be more directly over his head. In practice traveling any extended distance, let alone thousands of kilometers, by rolling would likely result in unpleasant bruising and be generally a bad idea.{{Citation needed}}

A prior example of an xkcd character with alternate gravitational susceptibility is [[417: The Man Who Fell Sideways]], where a consistent off-vertical pull somehow applies (rather than one linked to a spot on the stellar sphere). In [[1376: Jump]] Cueball floats sideways across the ground a bit above Earth, in a similar idea to being pulled sideways.

See also these other fictional examples of [https://www.goodreads.com/book/show/872243.The_Revolving_Boy 'personalized'] [https://wiki.lspace.org/Tethys gravitational] [https://wiki.lspace.org/Sally_Cambric susceptibilities].

Beret Guy has previously been interested in strange attracting forces in the universe, in [[502: Dark Flow]], where he hoped it was his mom and wished she would pull on him. It was though not about the Great Attractor, and the force did not clearly affect him, although his love for his mom did affect two space probes, as mentioned in the title text.

This comic came out just a bit more than a month before the next comic with one of Beret Guy's strange powers, [[2325: Endorheic Basin]]. Which is interesting since the previous comic with such a power came back in November 2017, [[1922: Interferometry]], more than 2.5 years before this one. Also in the Endorheic Basin comic strange forces exerted a pull on Beret Guy, although in that it was he who attracted water, where here it was himself that was most affected.

=====More detail=====
Some of the humor of the comic has to do with the immense differences in scale between Beret Guy and the Great Attractor.

In very round numbers our own {{w|Milky Way}} galaxy is 150,000 - 200,000 light years across. It is just one of several galaxies in something called the {{w|Local Group}}, which is around 10,000,000 light years across. And the Local Group is itself in something called the {{w|Virgo Supercluster|Local Supercluster}} (also called the Virgo Supercluster), around 110,000,000 light years across. Each galaxy, each group, and each {{w|supercluster}} is not just a chance alignment, but is a gravitational coherent structure. And all this is just yet a part of the even larger {{w|Laniakea Supercluster}} in which also the Great Attractor is located, along with more than 100,000 other galaxies, in a region of space spanning more than 500 million light years.

Something unpredictable (hence "anomalous") is going on with the galaxies in the Local Supercluster (including our own). These galaxies are indeed accelerating away from one another as seen by their red shift. {{w|Hubble's Law}} predicts the expansion should be uniformly proportional to their distance from Earth and from one another. But for the Local Supercluster something is restricting the expansion. That something is, as "viewed" from Earth, somewhere in the direction of the Southern Triangle constellation but 250,000,000 light years distant, and has (but only since 1988) been termed the Great Attractor. The Great Attractor can't conveniently be seen at visible wavelengths, because that direction is the so-called {{w|Zone of Avoidance}}: the area of the night sky obscured by our own Milky Way.

Boiling this all down: something a quarter of a billion light years away that makes an anomalous blip in the local rate of expansion of the universe, and whose existence astronomers deduce only by X-ray observations of stellar red-shift, has large-scale effects on everyday gravitational forces uniquely experienced by Beret Guy. OK, now you can smile.

==Transcript==
:[Cueball and Beret Guy stand next to each other, talking. Beret Guy leans towards Cueball by bending down one knee.]
:Cueball: I can't believe it's still light out. It's 8:00 PM!
:Beret Guy: Seriously! This morning I fell off the wall.

:[In a frame-less panel with the same setting Beret Guy is looking and pointing to the right.]
:Cueball: Wait, why were you sleeping on the wall?
:Beret Guy: The Great Attractor is near the horizon at night right now.

:[Zoom in on Beret Guy, who hold one hand palm up towards Cueball who is speaking to him off-panel.]
:Cueball (off-panel): The Great Attractor?
:Beret Guy: Yeah! The space one.
:Beret Guy: It pulls on me extra hard. Doctors said it's something to do with galactic motion and how many dimensions my bones have.

:[Cueball is still standing as Beret Guy slides away to the right, while looking and leaning back towards Cueball. He holds his arms slightly out, to keep his balance. Lines behind him and at his feet indicates his motion, even if he is clearly not walking. In his last word the letters becomes italic after Good and the last three Ts becomes smaller and smaller than the previous letters.]
:Beret Guy: This time of year, it's below us all day, so I stand vertically. But day-sliding season is near!
:Beret Guy: Let me know if you have any errands to run to the south!
:Beret Guy: Good''niiight<sup>t<sup>t</sup></sup>''

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Beret Guy]]
[[Category:Strange powers of Beret Guy]]
[[Category:Astronomy]]

3141: Mantle Model

2025-09-12T21:29:25Z

86.13.226.126: /* Explanation */ antle plumes

{{comic
| number = 3141
| date = September 12, 2025
| title = Mantle Model
| image = mantle_model_2x.png
| imagesize = 527x317px
| noexpand = true
| titletext = Mantle plumes explain Hawaii, Yellowstone, Iceland, the East African Rift, the Adirondack uplift, the Permian extinction, the decline of Rome, the DB Cooper hijacking, and the balrog in Moria. Those little hills of sand in your yard are caused by antle plumes.
}}

==Explanation==
{{incomplete|This page was created by {{w|Pele (deity)|Pele}}, the goddess of volcanoes and fire. Don't remove this notice too soon.}}

A {{w|mantle plume}} is a flow of {{w|magma}} upward from deep in the Earth toward the surface. Some plumes are thought to come close to the surface and result in hotspots that produce volcanoes, such as the hotspot that formed the {{w|Hawaiian Islands}} chain. Here Randall says the plumes account for every surface feature on Earth that we can't otherwise account for.

The title text extends this further, suggesting with increasing absurdity that mantle plumes account for other things:
* Hawaii. A hotspot, hypothesized to sit atop a mantle plume, did indeed create the Hawaiian Islands.
* {{w|Yellowstone}}. This area of hot springs, geysers, and other geothermal phenomena is in the {{w|Yellowstone Caldera}}, which some geologists believe sits atop a mantle plume.
* The {{w|East African Rift}}. This area in East Africa is a developing divergent {{w|tectonic plate}} boundary where the African plate is in the process of splitting into two tectonic plates.
* The {{w|Adirondack_Mountains#Geology|Adirondack uplift}}. The Adirondack Mountains were raised by the collision of tectonic plates. Some geologists believe that tectonic plates are in turn driven, in part, by mantle plumes.
* The {{w|Permian extinction}}, also called the 'Great Dying' and more formally as the Permian-Triassic extinction event, is the largest of the {{w|List of extinction events|"big five" mass extinctions}} since vertebrate life appeared on Earth. There are several hypotheses as to why it happened, once of which, {{w|Siberian Traps}} volcanism, could have happened because of a mantle plume.
* The decline of Rome refers to the end of the {{w|Roman Empire}}, which had nothing to do with mantle plumes.
* The {{w|DB Cooper}} airplane hijacking occurred in 1971 and remains unsolved. Dan B. Cooper is an alias of the hijacker, whose real name is unknown. The hijacking had nothing to do with mantle plumes.
* The {{w|balrog}} in {{w|Moria, Middle-earth|Moria}} is a fictional beast in {{w|J.R.R. Tolkien}}'s {{w|legendarium}} that first appeared in ''{{w|The Lord of the Rings}}''. It too has nothing to do with mantle plumes, though it does live deep underground.
* Ants often create anthills, which, depending on the species, can look like little plumes of sand. The title text refers to ants as "antle plumes".

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

A diagram of the Earth’s inner structure is shown with the caption “Standard geophysical model of the mantle”. Dotted lines forming structures that appear to be moving through and between various layers of the mantle are labeled with arrows. The arrows either point to the base of the structures on the inside of the planet or formations on the outside.

In the center around the Earth’s core are vertical columns rising up away from the core through cracks in lower layers of mantle. At different layers the structure either branches out horizontally between layers or again vertically through additional cracks. This process might yield a single vertical column, or several branching horizontal and vertical branches. These structures are labeled “hypothesized mantle plumes”.

On the Earth’s surface are various rock formations that align with the locations of plumes just below. The formations are labeled, “Every feature of the Earth surface that we have a hard time explaining”.

{{comic discussion}}<noinclude>

Talk:3118: iNaturalist Animals and Plants

2025-07-22T16:44:12Z

86.13.226.126: Commented on fungi

we probably need to add something about how bacteria are more common but not observable to the average person [[Special:Contributions/72.203.83.113|72.203.83.113]] 16:36, 21 July 2025 (UTC)
:Why? Bacteria are not animals or plants. [[Special:Contributions/2600:387:4:803:0:0:0:2C|2600:387:4:803:0:0:0:2C]] 17:45, 21 July 2025 (UTC)
:The lack of fungi is perhaps more noteworthy. --[[Special:Contributions/86.13.226.126|86.13.226.126]] 16:44, 22 July 2025 (UTC)

Why are some states missing their postal code? IA, FL, AK, HI don't have them. [[User:Nolanmeyer|Nolanmeyer]] ([[User talk:Nolanmeyer|talk]]) 18:27, 21 July 2025 (UTC)
:Probably human error. [[Special:Contributions/2001:4C4E:1C00:BF00:658B:2EF0:F9ED:69A|2001:4C4E:1C00:BF00:658B:2EF0:F9ED:69A]] 12:27, 22 July 2025 (UTC)
:Added a trivia section! --[[User:FaviFake|FaviFake]] ([[User talk:FaviFake|talk]]) 13:52, 22 July 2025 (UTC)

I am curious which animal and which plant are mentioned for the most states? [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 18:43, 21 July 2025 (UTC)
:Common Eastern Bumble Bee with 7 states [CT, IL, MD, MA, MN, VT, WI] and Common Milkweed with 6 states [IL, IA, MI, MN, NE, WI][[User:Nolanmeyer|Nolanmeyer]] ([[User talk:Nolanmeyer|talk]]) 18:53, 21 July 2025 (UTC)
:White-tailed Deer also has 7 states [IO, MI, MT, NH, PA, VI, WV] [[User:Rtanenbaum|Rtanenbaum]] ([[User talk:Rtanenbaum|talk]]) 19:16, 21 July 2025 (UTC)
:You're right! My python script missed Iowa because of a capitalization error in the transcription. [[User:Nolanmeyer|Nolanmeyer]] ([[User talk:Nolanmeyer|talk]]) 19:32, 21 July 2025 (UTC)

Is there a hidden joke in this one that needs explaining, or is it simply an interesting data map? [[Special:Contributions/37.19.197.233|37.19.197.233]]
: Looks like just an interesting map. Nothing wrong with that. --[[Special:Contributions/81.96.108.67|81.96.108.67]] 20:50, 21 July 2025 (UTC)
:: Wrong. What's wrong with it is that there's no joke. It's not "comic" in any way. {{unsigned ip|70.16.143.48|22:03, 21 July 2025 (UTC)}}
::: It may have derived from the earlier use of 'comic' implying a joke or humour, but the modern use of 'comic' for the artform does not. For example, Wikipedia refers to it as "a medium used to express ideas with images, often combined with text or other visual information", which is exactly what this is. [[Special:Contributions/82.13.184.33|82.13.184.33]] 10:41, 22 July 2025 (UTC)

Big question: what does "most-observed" mean? Most reported? Most likely for a resident to see? Most likely for a resident to pay attention to? -- [[User:Dtgriscom|Dtgriscom]] ([[User talk:Dtgriscom|talk]]) 19:38, 21 July 2025 (UTC)
:The comic already answers that question: "Not the most common species in the state, just the one people have reported the most times." [[Special:Contributions/174.53.211.85|174.53.211.85]] 20:06, 21 July 2025 (UTC)
:iNaturalist is a phone app used by people to help contribute to citizen science (i.e. help collect data for research), so people scan animals/plants that they see to send to iNaturalist databases to be identified automatically. Most-observed means the species that are most reported to the database (so the species with the most scans). The comic notes most reported ≠ most common since many people just ignore species of animals/plants they don't believe to be notable enough to take the effort to scan such as grass. [[Special:Contributions/97.126.175.170|97.126.175.170]] 20:10, 21 July 2025 (UTC)
::If people were reporting common animals they see, they'd probably be dogs and cats. And even more common would be insects -- a backyard probably has hundreds of ants living in it. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 23:30, 21 July 2025 (UTC)
::: "''reporting common animals they see,''" iNat members report what they think is worth reporting. I aint got time to figure if I see more cedar or maple-- in fact I reported a maple only cuz I found a spectaculary colorful maple leaf, a great picture. It is casual observations, not a strict census. (Yes, some observers get a bit obsessive, but still.......) Yes, dogs get reported a lot-- it is a great way to learn the process and you may already have good photos of Rover.
:::: Does this app double as an identification tool? In that case it might also be animals/plants that people don't know and are curious about. (I live in Germany and have a similar app for plants, but I admit I mostly use it for stuff that catches my eye, not for stuff I think is scientifically worth reporting.)--[[Special:Contributions/176.199.208.178|176.199.208.178]] 07:36, 22 July 2025 (UTC)

For the other {{w|U.S. Territories}} not mentioned (sorted animal, plant):
* Guam: Hawaiian Garden Spider, Coconut Palm
* Northern Marianas: Mariana Kingfisher, Alim
* American Samoa: Striped Surgeonfish, Fish Poison Tree
* US Virgin Islands: Green Iguana, Portia Tree

United States Minor Outlying Islands (collectively): Laysan Albatross, Stalky Grass
* Baker Island: Painted Lady, Rugosa Rose
* Howland Island: (not a valid location in iNat)
* Jarvis Island: Masked Booby, Sooty Tern (tie), (no plant)
* Johnston Atoll: Great Frigatebird, Beach Plant
* Kingman Reef: (no animal or plant)
* Midway Atoll: Laysan Albatross, Beach Naupaka
* Navassa Island: (not a valid location in iNat)
* Palmyra Atoll: Red-Footed Booby, Grand-Devil's Claws
* Wake Island: (not a valid location in iNat)
[[Special:Contributions/122.56.85.105|122.56.85.105]] 21:44, 21 July 2025 (UTC)

The surprising part is that palmettos isn't South Carolina's and deer isn't Maine's, and ''Virginia'' Springbeauty is in Ohio. [[User:Strontium|Strontium]] ([[User talk:Strontium|talk]]) 03:21, 22 July 2025 (UTC)

Is there a category for the very rare XKCD strips which don't include any humour, even in the alt text? I can't think of any from recent years, which makes this one extraordinary, but I might be forgetting some obvious examples. [[Special:Contributions/82.42.161.198|82.42.161.198]] 16:29, 22 July 2025 (UTC)

Talk:3106: Farads

2025-06-25T09:16:50Z

86.13.226.126:

Who wrote this description? It's complete nonsense. A capacitor can't throw a stone. A 1 F capacitor is also not remotely dangerous unless it's charged to a high voltage — except that a 1 F capacitor and a 0.01 F capacitor can be charged to essentially the same maximum voltage!

Unlike other units of measure where a single unit is non-extreme, "The capacitance of the Earth's ionosphere with respect to the ground is calculated to be about 1 F." [https://en.wikipedia.org/wiki/Farad] Most capacitors in practical use are measured in pico, nano, or micro farads. 03:04, 25 June 2025 (UTC)

Please note that the pound, shown in panel 2, is not an SI unit. The corresponding SI unit is the kilogram; an item with a mass of one kilogram is still commonplace. [[User:Troy0|Troy0]] ([[User talk:Troy0|talk]]) 03:11, 25 June 2025 (UTC)

When my father was a young engineer, the old guys would haze the new kids by asking them to fetch a "one farad capacitor". But everybody in the lab said "Sorry, I ran out, go ask Fred on the top floor", "Go ask Tom in the basement", "Try Peter's Parts on Vine St", etc--- give the kid a run-around. The joke was: at the time, 1F was likely large than a large garbage can and many hundred (non-SI) pounds. But the world changed, and in recent years you can easily buy 1F @ 16V, about the size of a soup can, to smooth car sound power feeds. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 03:27, 25 June 2025 (UTC)

This explanation would benefit from some elaboration on how and why supercapacitors are dangerous. [[Special:Contributions/195.252.226.234|195.252.226.234]] 04:41, 25 June 2025 (UTC)

Funnily enough, the wikipedia page for "Farad" (https://en.wikipedia.org/wiki/Farad) currently has a 1 farad supercapacitator as the title image. It looks pretty unassuming. [[User:Mouse|Mouse]] 08:54, 25 June 2025 (UTC)

Top of the page says June 23 even though it looks like this came out on June 25. Should it be changed? [[Special:Contributions/85.76.9.43|85.76.9.43]] 05:15, 25 June 2025 (UTC)

I agree with [[User:Troy0|Troy0]] that having a non-SI unit in there (1 pound) is incongruous, and it should instead be a sugar crystal weighing 1 gram. [[Special:Contributions/121.98.227.79|121.98.227.79]] 06:52, 25 June 2025 (UTC)

"most consumer electronics use at most a nanofarad" -> nah... Several hundreds of microfarads are quite common. But so are tens-of-picofarad, mostly in HF/RF filters etc. Calculating an average over all capacitors in all consumer electronics makes no sense anyway... But I'd say "Most consumer electronics use capacitors in the picofarad to milifarad range".
"To prevent static electricity from building lethal charge, unused supercapacitors are usually stored and transported with a "keeper", a steel or aluminum bar shorting the terminals." -> Static charge won't change the voltage of a 1 F capacitor much... V=q/C with small q and large C... The shorting is for high voltage capacitors that 'recharge' themselves trough {{w|Dielectric_absorption|dielectric absorption}}... Interesting, but completely different. -- [[User:Gautee|Gautee]] ([[User talk:Gautee|talk]]) 07:52, 25 June 2025 (UTC)

We now have an exact answer to the question "how tall is Cueball?"--[[Special:Contributions/86.13.226.126|86.13.226.126]] 09:16, 25 June 2025 (UTC)