explain xkcd - User contributions [en]

Talk:3095: Archaea

2025-05-29T15:29:30Z

162.158.41.36:

great, next time I get a disease caused by archea, I'll know who to blame [[Special:Contributions/172.70.111.123|172.70.111.123]] 23:16, 28 May 2025 (UTC)
:After ruling out ''absolutely'' everything else (primarly that being sunshine, moon light and good times), I'm gonna suggest that it's "the boogie". [[Special:Contributions/162.158.216.115|162.158.216.115]] 23:53, 28 May 2025 (UTC)
''"Archaea has" in the caption is unfortunate, as it denotes that a lineage (a branch of a phylogenetic tree) has become pathogenic. Pathogens are living cells, not lines on a page. "Archaeans have" would have been better.'' I'm not 100% sure on the way Archaea is used grammatically in English, but isn't Archaea the plural of Archaeon, so it should be ''Archaea have''? Is the word Archaeans normally used?[[Special:Contributions/162.158.233.117|162.158.233.117]] 07:37, 29 May 2025 (UTC)
: In math(s), the original latin and greek has remained kinda pristine in modern english. In medicine and taxonomy, it's a dumpster fire of vagary and inconsistency comparable to the US tax code. As far as I'm concerned, use whatever pluralisation you want, you won't degrade the language any further. --DW [[Special:Contributions/162.158.187.177|162.158.187.177]] 15:19, 29 May 2025 (UTC)
:'Archaea' is indeed the plural of 'archaeon', and congratulations for getting this correct! In an English-speaking world in which 'bacteria/bacterias' (bacterium/bacteria), 'algae/algaes' (alga/algae), and, for that matter, 'stadium/stadiums' (stadium/stadia) have become commonplace even in scientific publications [see ''dumpster fire'', above], knowledge of how to handle the singulars and plurals of Latin and latinized Greek loanwords is increasingly rare. The domain name 'Archaea' is in the plural, because it stands for a group of organisms. The same is generally true for the names of taxonomic groups above genus. However, because the name stands for ''one'' group of organisms, it is possible to treat the name as a {{w|Collective_noun|collective noun}} which takes a singular verb form. Thus, [the domain name] ''Archaea has'' and ''Archaea'' [in the specimen/culture collection] ''have'' are both correct, with context the determining factor. Replacing Archaea with [https://www.merriam-webster.com/dictionary/Archaean Archaean] ducks the Latin and places singulars and plurals more in line with common English constructions (archaean/archaeans). Therefore, ''Archaea have'' and ''Archaeans have'' are both appropriate for the caption, whereas ''Archaea has'' is not. Confused yet? [[Special:Contributions/162.158.41.36|162.158.41.36]] 15:29, 29 May 2025 (UTC)

:Perhaps they've risen up en masse, forming a state of Archaea, with a war cabinet and army to take on the humans.[[Special:Contributions/172.71.241.51|172.71.241.51]] 10:11, 29 May 2025 (UTC)
:: [https://www.dude-n-dude.com/2020/01/12/amoebas-lorica-outbreak/ Be careful what you wish for] ... [[Special:Contributions/162.158.41.36|162.158.41.36]] 15:29, 29 May 2025 (UTC)

2035: Dark Matter Candidates

2025-05-07T20:13:15Z

162.158.41.36: /* Explanation */ Update chart explanation with additional xkcd information on dark matter

{{comic
| number = 2035
| date = August 20, 2018
| title = Dark Matter Candidates
| image = dark_matter_candidates.png
| titletext = My theory is that dark matter is actually just a thin patina of grime covering the whole universe, and we don't notice it because we haven't thoroughly cleaned the place in eons.
}}

==Explanation==
{{w|Dark matter}} is a hypothetical, invisible form of matter used by the vast majority of astronomers to explain the far too high apparent mass of objects at large scales in our universe. In galaxies, stars are orbiting faster than the gravitational force of the sum of the masses of visible matter in the galaxy could cause, and entire galaxies are observed moving much faster around each other than their visible masses could explain. In galactic collisions, the mass can appear to separate from the visible matter, as if the mass doesn't collide but the visible matter does. A small handful of galaxies have been observed to not have this property, suggesting that it is a ''thing'' that a galaxy can have more or less of and is separable from. At scales of our solar system, those effects are too small and can't be measured. The most plausible explanation for all of these phenomena is that there is some "dark matter" that has gravity, but is otherwise undetectable. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities for what dark matter could be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10−15 to 10−3 kg are given in grams together with appropriate prefixes, while the ton takes the place of 103 kg.

Only massive objects ranging from subatomic particles up to super massive ones are covered in this comic. There are also {{w|Dark matter#Alternative hypotheses|alternative hypotheses}} trying to modify general relativity with no need of additional matter. The problem is that these theories can't explain all different observations at once. Nonetheless dark matter is a mystery because no serious candidate has been found yet.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten, with explanations suggested by astronomers covering only some portions of that range. [[Randall]] fills the gaps with highly absurd suggestions.

;Axion
:An {{w|Axion|axion}} is a hypothetical elementary particle postulated in 1977 to resolve the strong CP problem in {{w|Quantum chromodynamics|quantum chromodynamics}}, a theory of the strong force between {{w|Quark|quarks}} and {{w|Gluon|gluons}} which form {{w|Hadron|hadrons}} like {{w|Proton|protons}} or {{w|Neutron|neutrons}}. If axions exist within a specific range of mass they might be a component of dark matter. The advantage of this particle is that it's based on a theory which could be proved or also disproved by measurements in the future. Other theories, not mentioned in this comic, like the {{w|Weakly interacting massive particles|weakly interacting massive particles (WIMPs)}} are much more vague.

;Sterile neutrino
:{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter. The well known {{w|Neutrino|neutrinos}} are also charged under the {{w|Weak interaction|weak interaction}} and can be detected by experiments.

;Electrons painted with space camouflage
:{{w|Electron|Electrons}} are fundamental particles which compose the outer layers of atoms. A large number of electrons in the galaxy would be relatively easy to detect, as they not only interact with light (which dark matter does not appear to), but also have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say,{{Citation needed}} this is not an actual candidate for dark matter.) The mass of an electron is about 0.5 MeV which fits well into the graph.

;Neutralino
:A {{w|Neutralino|neutralino}} is a hypothetical particle from {{w|Supersymmetry|supersymmetry}} and is also a current candidate for dark matter. But there is not evidence whether or not supersymmetry is correct and none of the predicted particles have been found yet.

;Q-ball
:In theoretical physics, a {{w|Q-ball}} is a stable group of {{w|boson}}s. It's an actual candidate for dark matter. (In billiards, a cue ball is the white or yellow ball hit with the cue in normal play. In addition, [[Cueball]] is the name explain xkcd uses for the most common xkcd character.)

;Pollen
:{{w|Pollen}} is a joke candidate, though people with seasonal allergies may suspect that the universe is genuinely made up entirely of pollen in the springtime.

;No-See-Ums
:{{w|Ceratopogonidae|No-See-Ums}} are a family (Ceratopogonidae) of small flies, 1–4 mm long, that can pass through most window screens. Another joke candidate, because dark matter is invisible and the name "no-see-ums" implies that the flies are invisible.

;Bees
:Insects of the clade {{w|Bee|Anthophila}} are major pollinators of flowering plants. In recent years {{w|Colony collapse disorder|bees have been disappearing}} at an alarming rate; {{w|The Stolen Earth|Doctor Who explained}} that they are in fact aliens leaving Earth prior to a Dalek invasion.

;8-balls
:In pool, the {{w|Pool (cue sports)|8-ball}} is a black ball numbered 8. It's a pun with Q-ball/cue ball. Unless undetected aliens have discovered billiards and become addicted to it, 8-balls are found only on Earth and are, hence, unlikely dark matter candidates. The 8-ball is also a popular unit of sale for black market pharmaceuticals like cocaine, where it stands for ⅛ ounce (3.5 g). This doesn't make sense as a dark matter candidate either – unless dark matter is hard to detect because it's illegal & trying to avoid the cops.

;squirrel - not on chart
:[[2186: Dark Matter]] discusses the hypothesis that dark matter near earth is a squirrel.

;about 20 pounds - not on chart
:The oracle in [[3085: About 20 Pounds]] reveals that dark matter particles have a mass of roughly 10 kilograms.

;Space cows
:Cows are {{w|Bovinae|bovines}} extensively farmed on Earth for milk and meat.{{Citation needed}} Although there is folklore concerning cows {{w|Hey diddle diddle|achieving circum-lunar orbits}}, not to mention their appearance on a {{w|Shindig (Firefly)|beloved space western TV show}}, as Muppet cow [http://muppet.wikia.com/wiki/Natalie Natalie] in the Sesame Street News Flash (and [https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWestern others less-remembered]), they have yet to be found elsewhere in the Universe. In the television show "Too Close for Comfort", one of the characters is the cartoonist of a comic strip called "Cosmic Cow". {{w|Spherical cow|Spherical cows}} (and especially those in a vacuum, as they would essentially be if in space) have also been used (humorously) by physicists needing to simplify some source of mass in a given problem.

;Obelisks, monoliths, pyramids
:While those human constructions are huge on a human scale, they're negligible at universe-scale. It would take a large number of such constructions, distributed through space, to replicate the effects of dark matter; while a scenario could be envisioned where enough such constructs existed, with properties and distribution allowing them to match observations, this is obviously not a likely explanation. They often show up in fiction and pseudo-scientific literature as alien artifacts generating immense unknown power out of nowhere, with the most famous and influential example being the three monoliths from {{w|2001: A Space Odyssey (film)|2001: A Space Odyssey}} (with the largest having a mass of about 500,000 tonnes).

;Black holes ruled out by:
:{{w|Black hole|Black holes}} are known to occur in sizes of a few solar masses (about 1030-1031 kg) as remnants of the core of former big stars, as well as in quite large sizes at the centers of galaxies (millions or even billions of solar masses). But recent gravitational wave detections indicate that black holes at 50 or 100 solar masses also exist, though their origin is still not understood. Randall doesn't mention this but some astronomers hope that these could fill at least a part of the gap. While black holes are widely reported to be ruled out as a candidate for dark matter for various reasons Randall has listed, such constraints are based on "monochromatic" mass distributions -- meaning that all such black holes are assumed to have the same mass -- which is considered physically implausible for populations of merging bodies which are known to have vastly different masses. See: [https://arxiv.org/pdf/1709.07467.pdf Primordial Black Holes as Dark Matter (2017)] and [https://arxiv.org/pdf/1705.05567.pdf Primordial black hole constraints for extended mass functions (2017)] (That this is a common practice in cosmology may be part of the reference to "buzzkill" astronomers.) He rules out all black holes in the range of approximately 1010 kg to 1033 kg even when below some gaps at the bars appear.

:Except the last item, all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four solar masses.
:* Gamma rays: If dark matter were black holes of this size, the black holes could be evaporating by the predicted {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction if many of those objects would exist. Nonetheless this radiation is still hypothetical and not been observed on any known black holes. Furthermore those objects would be very small because the Schwarzschild radius of a 1012 kg black hole is approximately 148 fm (1.48×10−13 m), which is between the size of an atom and an atomic nucleus.

:* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe and have been observed only in distant galaxies. While gravitational microlensing (see below) is an astronomical phenomenon, it doesn't make much sense here. GRBs are short (milliseconds to several hours) and are often detected only by space-borne sensors for gamma-rays -- rarely at any other wavelengths. Measuring lensing effects would be very difficult. This [https://arxiv.org/abs/1406.3102 paper] discusses the probability of detecting lensing effects caused by {{w|Dark matter halo|galactic halo objects}} among the known GRBs given sufficient objects to represent the missing mass.

:* Neutron star data: {{w|Neutron star|Neutron stars}} aren't black holes, but they're also very small highly compact objects at about 1.4-2.16 solar masses. While black holes can't be observed directly, neutron stars are detectable in many wavelengths. The number of them gives a clue about the number of black holes close to the mass of the sun, a number which is far too low to make up dark matter.

:* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect, (the path of radiation is changed by passing through space bent by nearby mass). This was predicted by Einstein's {{w|General Relativity|Theory of General Relativity}} and was first confirmed in 1919 during a solar eclipse, when a star which was nearly in line with the sun appeared more distant to the sun than usual. Astronomers have found many so called {{w|Einstein ring|Einstein rings}} or Einstein crosses where a massive object in front of other galaxies bends the light toward us. Those massive objects may be black holes, but the number is far too low to explain dark matter.

:* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and has been very stable since shortly after its formation. If not, we wouldn't exist. If dark objects at 1024 to 1030 kg (mass of Earth up to mass of Sun) accounted for dark matter and were distributed throughout galaxies, there should be many of them in the vicinity of our solar system and the system wouldn't be stable at all.

:* Buzzkill Astronomers: Black holes above a certain size are thought by some astronomers to be impossible to miss, due to the effects they have on nearby matter. At the mass of some 1030 kg there must be many supernova remnants we still haven't found. Black holes of about 1035 kg have long been considered dark matter candidates by a minority group of cosmologists, as could be seen here [https://arxiv.org/pdf/1001.2308.pdf Primordial Black Holes as All Dark Matter (2010)] and the Milky Way's first discovered intermediate mass black hole falling in this range shown here [https://www.nao.ac.jp/en/news/science/2016/20160115-nro.html Signs of Second Largest Black Hole in the Milky Way].

:Not covered by this comic are {{w|Massive compact halo object|massive astrophysical compact halo objects (MACHOs)}} composed of hard to detect dim objects like black holes, neutron stars, brown dwarfs, and other objects composed of normal {{w|Baryon|baryonic}} matter. Nevertheless observations have shown that the total amount of baryonic matter in our universe on large scales is much smaller than it would be needed to explain all the measured gravitational effects.

;Maybe those orbit lines on space diagrams are real and very heavy
:Diagrams of our solar system (or any planetary system) often show lines representing the elliptical paths the planet takes around its sun. These lines don't show real objects, though. Astronomers just draw them on pictures of the solar system to show where the planets move. If you draw a line on a map to give someone directions, that line isn't an object in real life; it's just on the map. If these lines were real, they would be ''huge'' (Earth's would be 940 million km long (2π AU) and Neptune's would be 28 ''billion'' kilometers long). [https://www.youtube.com/watch?v=0fKBhvDjuy0 Powers of Ten (1977)] gives a good sense of just how large these orbit lines need to be in order to be visible in space diagrams. If these orbit lines were also very dense, they would have a huge mass and could possibly account for the missing 85% of the mass in the universe. But they would also constantly be impaling the planets, including the Earth, which would probably be a problem.{{Citation needed}} Their mass would also affect planetary motions in ways which we would detect. A related worry about space travel was expressed in previous centuries; it was thought that the planets were embedded within {{w|Celestial spheres|crystal shells}} (spheres or Platonic solids), and a rocket into space could smash the shells and send planets plummeting to Earth. Another joke candidate.

;Title text
:The title text refers to the fact that space is just vast emptiness where a little bit of dirt could be overlooked. Actually the mean density of detectable matter in the universe, according to NASA, is equivalent to roughly [https://map.gsfc.nasa.gov/universe/uni_matter.html 1 proton per 4 cubic meters]. And because this matter is mostly located in galaxies -- and inside there in stars and clouds -- the space between is even more empty. For comparison, one gram of hydrogen consists of {{w|Avogadro constant|6.022 × 1023 atoms}}. Like at home wiping with a cleaning cloth in which we can see the dirt that wasn't clearly visible on the surface we have wiped, Randall believes that some few atoms more per cubic meter could stay undetected in the same way. This isn't true because in the space between galaxies astronomers can detect matter as it spreads over thousands or millions of cubic light years. Atoms can't hide; there is always radiation.

==Transcript==
:Dark matter candidates:
:[A line graph is shown and labeled at left quarter in eV and further to the right in g together with some prefixes.]
:[The labels read:]
:µeV, meV, eV, keV, MeV, GeV, TeV, 10-18kg, ng, µg, mg, g, kg, TON, 106kg, 1012kg, 1018kg, 1024kg, 1030kg

:[All items are shown in bars ranging between two approximately values:]
:< 1 µeV - 10 meV: Axion

:1 eV - 10 keV: Sterile neutrino

:0.5 MeV (exactly): Electrons painted with space camouflage

:10 GeV - 10 TeV: Neutralino

:100 TeV - 10-17 kg: Q-ball

:1 ng - 100 ng: Pollen

:0.1 mg - 1 mg: No-See-Ums

:10-1 g (exactly): Bees

:10 g - 100 g: 8-balls

:100 kg - TON: Space cows

:TON - 109 kg: Obelisks, monoliths, pyramids

:109 kg - 1033 kg: Black holes ruled out by:
::109 kg - 1013 kg: Gamma rays
::1013 kg - 1017 kg: GRB lensing
::1015 kg - 1022 kg: Neutron star data
::1021 kg - 1030 kg: Micro lensing
::1024 kg - 1030 kg: Solar system stability
::1030 kg - 1033 kg: Buzzkill astronomers

:1033 kg - >1036 kg: Maybe those orbit lines on space diagrams are real and very heavy

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Cosmology]]
[[Category:Line graphs]]
[[Category:Bees]]
[[Category:Animals]]
[[Category:Illustrations of scale]]

3085: About 20 Pounds

2025-05-07T20:03:34Z

162.158.41.36: /* Explanation */ Link other dark matter cartoons.

{{comic
| number = 3085
| date = May 5, 2025
| title = About 20 Pounds
| image = about_20_pounds_2x.png
| imagesize = 666x278px
| noexpand = true
| titletext = In addition to gravity, burritos interact through the strong, weak, and electromagnetic forces, which is believed to be a major contributor to their popularity.
}}

==Explanation==
{{incomplete|Created by a £20 20-LB PARTICLE. In ludicrous units. Are any categories missing? Don't remove this notice too soon.}}

The nature of {{w|dark matter}} is a significant unsolved problem in physics. We observe that galaxies spin faster than we expect based on the nearby observable matter. Likewise galactic motions indicate additional mass that we have not observed in other ways. Dark matter is the name we give to this mass. In the comic, [[Cueball]] and [[Ponytail]] consult an {{w|oracle}} to learn about dark matter.

The pentacle and candles suggest that the oracle is supernatural, summoned by an occult ritual; something which would present its own challenges to our understanding of the physical world. There may be a pun here, in that they may be using 'dark magic' to communicate with something from the 'dark realm' on the assumption that it will know about dark matter. However, the word 'dark' in dark matter simply means that we do not know how to observe it; we have no evidence that dark matter is evil or satanic (though [[Randall]] may consider it [[:Category:Comics with cursed items|cursed]]). The oracle is used very similarly to how people have been using and customizing {{w|large language model|large language models}}.

In general, not all forces interact with all particles; indeed, {{w|gravity}} is believed to be the only force that interacts with everything we have observed. If a force doesn't interact with a particle, then the particles existence cannot be directly observed via disturbances in that force. In particular, something that doesn't interact with electromagnetism cannot be 'seen', as photons will pass through it relatively unaffected, and likewise cannot be felt, because collision is a side effect of the {{w|Pauli exclusion principle}}.

Even {{w|neutrino}}s—famous for {{what if|73|interacting with ''almost'' nothing}}—still interact via the {{w|weak force}}, allowing them to be detected with sufficiently large tanks of dense material (as most atoms interact with the weak force, however weakly). A particle that interacts with ''nothing'' except gravity could only be detected by a {{w|LIGO|gravitational telescope}}.

The particle's mass is described vaguely as ''about twenty pounds'' (roughly 10 kilograms), in line with how apparently all-knowing oracles legendarily avoid unambiguous statements. This is an absolutely ludicrous amount of energy for particle physics. Any interaction would have to involve an equally ludicrous amount of other particle mass being in exactly the right place and time, a coincidence that might be so rare that one would not expect it to occur ever in the history of the universe. By comparison, the {{w|top quark}}, the heaviest single particle we have observed, with a mass over a hundred times that of the proton, is around a tenth of a trillionth of a trillionth of a pound.

Under more normal circumstances, we might still hope to observe the properties of the particle via creating it ourselves under controlled laboratory conditions. But again, there is no reasonable way to focus the energy required into a single particle interaction. The {{w|Large Hadron Collider|most powerful particle accelerator in the world}}, for example, peaks at about ten thousand times the mass of the proton—a solid billion times less energy than required—so it's out too.

Despite all this, twenty pounds is also much too ''small'' to be detectable via gravitational interaction—its {{w|Perturbation (astronomy)|influence on the orbits of planets}}, say, or the strength of its {{w|gravitational lensing}} effect, would be entirely negligible. Thus in the scenario posed by the comic, there is no plausible way to observe more about dark matter while on Earth. Even if we did find some such particles naturally occurring, and had instruments that could measure such small gravitational forces, since it would interact only via gravity, the only properties it could have other than mass would be its decay rates from other particles—which, again, would all be essentially nil due to its mass.

The oracle proceeds to break expectations by suggesting that Ponytail and Cueball go out for {{w|burrito}}s, something not considered scientific. When faced with the apparent futility of continuing to try to investigate dark matter, the oracle predicts that going out for burritos is precisely as productive as any other approach—i.e., not at all. It justifies the suggestion by burritos being "pretty" good, again neither exactly quantifying the oracularity, and likely not even giving the optimal idea (for choice of food, or of any other "what now?" diversion that it might give).

The title text observes that burritos interact through all four known {{w|fundamental interactions}}, making burritos popular. The electromagnetic force mediates the chemical reactions leading to a burrito's taste, the strong force keeps atomic nuclei together, and gravity gives burritos heft, all of which are helpful for enjoying them. It's hard to see how the weak force, which takes part in radioactive decay, helps with burrito enjoyment or popularity, but the weak force is responsible for the nuclear fusion that allowed the complex elements of the burrito to exist in the first place.

The previous comic [[3084: Unstoppable Force and Immovable Object]] dealt with particles which do not even interact with gravity.
In [[2035: Dark Matter Candidates]] these 20 lb dark matter particles fit between magic 8 balls and space cows. The squirrels that make up [[2186: Dark Matter]] near the earth must be pretty chunky.

==Transcript==
:[Cueball and Ponytail are standing in front of a pentacle with lit candles at the corners. A black sphere, the oracle, is floating above the middle of the pentacle.]
:Ponytail: Dear oracle,
:Ponytail: What is the nature of dark matter?
:Oracle: It's about 20 pounds.

:[Close up of oracle]
:Off-panel: What?
:Oracle: Dark matter is a particle. It weighs about 20 pounds.
:Oracle: It only interacts through gravity.

:[Same view as first panel]
:Cueball: Only gravity, huh?
:Cueball: So none of our experiments are really going to tell us any more about it, then.
:Oracle: Afraid not.

:[Same view as first and third panels, except Cueball lifted his forearm.]
:Cueball: So what do we do?
:Oracle: You should go out for burritos.
:Ponytail: How will that help?
:Oracle: Well
:Oracle: Burritos are pretty good.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Physics]]
[[Category:Cosmology]]
[[Category:Food]]

3085: About 20 Pounds

2025-05-07T19:57:15Z

162.158.41.36: /* Transcript */ Category:Cosmology

{{comic
| number = 3085
| date = May 5, 2025
| title = About 20 Pounds
| image = about_20_pounds_2x.png
| imagesize = 666x278px
| noexpand = true
| titletext = In addition to gravity, burritos interact through the strong, weak, and electromagnetic forces, which is believed to be a major contributor to their popularity.
}}

==Explanation==
{{incomplete|Created by a £20 20-LB PARTICLE. In ludicrous units. Are any categories missing? Don't remove this notice too soon.}}

The nature of {{w|dark matter}} is a significant unsolved problem in physics. We observe that galaxies spin faster than we expect based on the nearby observable matter. Likewise galactic motions indicate additional mass that we have not observed in other ways. Dark matter is the name we give to this mass. In the comic, [[Cueball]] and [[Ponytail]] consult an {{w|oracle}} to learn about dark matter.

The pentacle and candles suggest that the oracle is supernatural, summoned by an occult ritual; something which would present its own challenges to our understanding of the physical world. There may be a pun here, in that they may be using 'dark magic' to communicate with something from the 'dark realm' on the assumption that it will know about dark matter. However, the word 'dark' in dark matter simply means that we do not know how to observe it; we have no evidence that dark matter is evil or satanic (though [[Randall]] may consider it [[:Category:Comics with cursed items|cursed]]). The oracle is used very similarly to how people have been using and customizing {{w|large language model|large language models}}.

In general, not all forces interact with all particles; indeed, {{w|gravity}} is believed to be the only force that interacts with everything we have observed. If a force doesn't interact with a particle, then the particles existence cannot be directly observed via disturbances in that force. In particular, something that doesn't interact with electromagnetism cannot be 'seen', as photons will pass through it relatively unaffected, and likewise cannot be felt, because collision is a side effect of the {{w|Pauli exclusion principle}}.

Even {{w|neutrino}}s—famous for {{what if|73|interacting with ''almost'' nothing}}—still interact via the {{w|weak force}}, allowing them to be detected with sufficiently large tanks of dense material (as most atoms interact with the weak force, however weakly). A particle that interacts with ''nothing'' except gravity could only be detected by a {{w|LIGO|gravitational telescope}}.

The particle's mass is described vaguely as ''about twenty pounds'' (roughly 10 kilograms), in line with how apparently all-knowing oracles legendarily avoid unambiguous statements. This is an absolutely ludicrous amount of energy for particle physics. Any interaction would have to involve an equally ludicrous amount of other particle mass being in exactly the right place and time, a coincidence that might be so rare that one would not expect it to occur ever in the history of the universe. By comparison, the {{w|top quark}}, the heaviest single particle we have observed, with a mass over a hundred times that of the proton, is around a tenth of a trillionth of a trillionth of a pound.

Under more normal circumstances, we might still hope to observe the properties of the particle via creating it ourselves under controlled laboratory conditions. But again, there is no reasonable way to focus the energy required into a single particle interaction. The {{w|Large Hadron Collider|most powerful particle accelerator in the world}}, for example, peaks at about ten thousand times the mass of the proton—a solid billion times less energy than required—so it's out too.

Despite all this, twenty pounds is also much too ''small'' to be detectable via gravitational interaction—its {{w|Perturbation (astronomy)|influence on the orbits of planets}}, say, or the strength of its {{w|gravitational lensing}} effect, would be entirely negligible. Thus in the scenario posed by the comic, there is no plausible way to observe more about dark matter while on Earth. Even if we did find some such particles naturally occurring, and had instruments that could measure such small gravitational forces, since it would interact only via gravity, the only properties it could have other than mass would be its decay rates from other particles—which, again, would all be essentially nil due to its mass.

The oracle proceeds to break expectations by suggesting that Ponytail and Cueball go out for {{w|burrito}}s, something not considered scientific. When faced with the apparent futility of continuing to try to investigate dark matter, the oracle predicts that going out for burritos is precisely as productive as any other approach—i.e., not at all. It justifies the suggestion by burritos being "pretty" good, again neither exactly quantifying the oracularity, and likely not even giving the optimal idea (for choice of food, or of any other "what now?" diversion that it might give).

The title text observes that burritos interact through all four known {{w|fundamental interactions}}, making burritos popular. The electromagnetic force mediates the chemical reactions leading to a burrito's taste, the strong force keeps atomic nuclei together, and gravity gives burritos heft, all of which are helpful for enjoying them. It's hard to see how the weak force, which takes part in radioactive decay, helps with burrito enjoyment or popularity, but the weak force is responsible for the nuclear fusion that allowed the complex elements of the burrito to exist in the first place.

The previous comic [[3084: Unstoppable Force and Immovable Object]] dealt with particles which do not even interact with gravity.

==Transcript==
:[Cueball and Ponytail are standing in front of a pentacle with lit candles at the corners. A black sphere, the oracle, is floating above the middle of the pentacle.]
:Ponytail: Dear oracle,
:Ponytail: What is the nature of dark matter?
:Oracle: It's about 20 pounds.

:[Close up of oracle]
:Off-panel: What?
:Oracle: Dark matter is a particle. It weighs about 20 pounds.
:Oracle: It only interacts through gravity.

:[Same view as first panel]
:Cueball: Only gravity, huh?
:Cueball: So none of our experiments are really going to tell us any more about it, then.
:Oracle: Afraid not.

:[Same view as first and third panels, except Cueball lifted his forearm.]
:Cueball: So what do we do?
:Oracle: You should go out for burritos.
:Ponytail: How will that help?
:Oracle: Well
:Oracle: Burritos are pretty good.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Physics]]
[[Category:Cosmology]]
[[Category:Food]]

Talk:3085: About 20 Pounds

2025-05-07T19:34:51Z

162.158.41.36: energy conservation?

Wow - first here! I can't help thinking 'about 20 pounds' could be exactly 10 kg! 0r even one Newton?! [[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 05:50, 6 May 2025 (UTC)
:"One Newton" and "10 kg" are totally different things. "10 kg" would cause 1 Newton of gravitational force if you were in a world with about 1% of Earth's gravity, though. --[[Special:Contributions/172.69.109.86|172.69.109.86]] 09:53, 6 May 2025 (UTC)
::Oops! In my rush I should have checked and put 100 Newtons. I was relying on 10kg being about 22 pounds, or rather the other way around, and then a particle having mass not weight and Science using Metric units. Apologies. [[User:RIIW - Ponder it|RIIW - Ponder it]] ([[User talk:RIIW - Ponder it|talk]]) 11:41, 6 May 2025 (UTC)
::(Moved your reply up a bit. You seemed to respond to "20 pounds are...", below, ''and'' split their timestamp signature from their message. And forgot to sign properly, at first, so I got edit-conflicted ''twice'' whilst trying to post myself and correct your initial error. Please take a bit more care, everybody. [[Special:Contributions/172.70.163.53|172.70.163.53]] 11:52, 6 May 2025 (UTC))
:20 pounds are approximately 9.072 kg, so not exactly 10 kg (in fact, it rounds to 9). [[Special:Contributions/172.70.134.55|172.70.134.55]] 10:02, 6 May 2025 (UTC)
::That's the wrong way to think about it. "Exactly 10kg" is "exactly 22.0462lbs", but that (to the nearest single significant figure) is legitimately "about 20lbs". See any given step in [[2585: Rounding]], especially where that 'disagrees greatly' with an adjacent step.
::As with any Oracle (that's worth its omphalos), it may be giving an ''entirely true'' answer which nevertheless is deliberately phrased as ambiguous and misinterpretable, the possible supernatural complement to the 'exact words' genie contract. As with the [[2741: Wish Interpretation]] genie, the Oracle ''may'' slip into less "unhelpfully helpful" mode immediately after, though for different reasons. However, "burritos are ''pretty'' good" also suggests that there's some other thing that is ''more'' good, so — again — it's giving a sufficient response to what they (now) should do, but not a perfect one.
::As I write, the explanation (probably needs a general rewrite) doesn't mention anything about the burritos except as title text, or I would have ensured the famed exact-words/vague-detail was noted in that bit. (Shorter than here.) [[Special:Contributions/141.101.98.82|141.101.98.82]] 11:46, 6 May 2025 (UTC)
:Nobody said anything about "exactly 20 pounds". 20 pounds is about 10 KG and about 100 Newtons when considered as a force rather than a mass. The comic says "about 20 pounds". [[Special:Contributions/172.70.230.63|172.70.230.63]] 22:36, 6 May 2025 (UTC)
Though I don't think it at all merits being described as a reference, I am minded of the {{w|The Usenet Oracle}} (at least when I knew of it). Though, if it ''was'' to be a deleliberate shout-out, I'd expect a few more actual in-jokes. [[Special:Contributions/172.70.86.130|172.70.86.130]] 06:10, 6 May 2025 (UTC)

I bet Randall is in some kind of force-interaction-related, What-if-induced rabbit hole right now (or has been at the time of writing). Wondering what the next comic will be about. [[Special:Contributions/172.71.144.175|172.71.144.175]] 08:39, 6 May 2025 (UTC)

"Nature of ... 20 pounds" is a reference to the koan "A monk asked Tozan, 'What is the nature of Buddha?' He replied, 'Three pounds of flax.'" Someone can add this to the explanation. [[Special:Contributions/172.70.111.115|172.70.111.115]] 08:57, 6 May 2025 (UTC)
:There is a similar story in the Principia Discordia. When asked what is the meaning behind POEE, a Discordian cabal, Malaclypse the younger answered "five tons of flax." [[User:FlavianusEP|FlavianusEP]] ([[User talk:FlavianusEP|talk]]) 16:26, 6 May 2025 (UTC)

"something that doesn't interact with electromagnetism cannot be 'seen', as photons will pass through it completely unaffected": is this supposed to be true ? I thought photons interacted with gravity, and even the phrase before states that gravity is believed to affect everything. [[Special:Contributions/172.68.151.93|172.68.151.93]] 09:17, 6 May 2025 (UTC)
: Indeed, photons do interact with gravity. What I had in mind when writing that were ''direct'' interactions -- of course everything interacts with everything else via a second-order interaction, <X> -> gravity -> <X> for any particle/field <X>. I can clarify that if nobody gets to it before I get around to it. [[User:Linkhyrule5|Linkhyrule5]] ([[User talk:Linkhyrule5|talk]]) 21:45, 6 May 2025 (UTC)
:We can ''infer'' Dark Matter (and, for that... *ahem* ...matter, also Dark Energy) from what the photons in the universe are telling us that does not look anything like what 'light(-interacting) matter' ''should'' be doing. As with some searches for black holes (most particularly, when the theory is that the unseen mass of the universe is a lot of small black holes drifting in the void, not acreting enough to create secondary visible effects), whether or not light is being gravitationally lensed by things (that we cannot directly see) is part of the way that we're narrowing down what-and-where DM is.
:And, I think, currently it seems to be considered that it's residing in a webwork of DM tendrils, at extragalactic (indeed, cosmological) scales, such that where the tendril cross is where they draw 'normal' matter together enough to be any given galaxy. But that's in an "explains all(/many) known facts" way, and might yet be incorrect. e.g. if there's side-dimensions (equally undetectable, at least visually) that change the inverse-square dropoff of gravity at large enough scales to govern galactic rotation rates by just enough to fit observations, or we have some other misunderstanding/scientific blind spot that further study may correct.
:Or, in short, think Brownian Motion. We can't see a handful of air molecules (not by normal, even microscope-enhanced, human vision), they might as well be invisible. But, by what we see of more visible particles, suggests that they exist as something. Conversly, the æther, a proposed medium for light, was thought to exist in a similar all-pervasive manner (insofar as trivial human experience, though less physically 'interactive' than wind), but deeper checks (as to whether its effects on light were as they should have been) dismissed it as a possible concept.
:Depending upon interpretation of the comic (I originally read it as "all dark-matter particles are ~20lbs in mass WIMPs/nano-MACHOs/whatever", but it seems that others take it as "''all of'' dark-matter particles is a single ~20lbs mass particle"; and that's make the oracle-invokers' attitudes more logical, if not the universe), there actually being Dark Matter, but it being just 20lbs of 'something' ''somewhere'' in the whole universe, makes it a needle in a galactic-supercluster-sized haystack.
:Detecting ''that'' would be difficult in the extreme. Even if it's somehow within a few hundred metres of the experimenters. There are ways to {{w|Cavendish experiment|observe the movements of small masses at small distances}}, but when you don't even have a clue ''if'' it exists (or is moving/has moved, and how), it's fairly hopeless. Gravitational lensing of light would be impractical at such distances/masses. LIGO may be very clever, insofar as merging high-mass objects at long distances, but not really for this. Event Horizon Telescope's ability to see a black hole('s accretion disk) via Very Long Baseline Interferometry is also totally useless here.
:I think I'd ''also'' settle for the burritos, given that certainty that I wasn't going to find what I'm looking for via any obvious route. (Assuming I couldn't ask the Oracle to ''show me'' the Dark Matter, rather than just answer questions about it. And noting that, if not for the indicated progression of the conversation, I might have assumed the oracular voice were really from the pentagram (more usual for demonology, not oracularities!) and that the dark blob ''was'' the 20lbs of Dark Matter. Which, of course, it ''does not deny'', so maybe my headcan[n]on ''is'' that the summoned Oracle ''is'' the DM, being deliberately evasive, and successfully so. That would satisfy it being both that which Ponytail seeks, ''and'' the entity of which Ponytail summons in order to seek it! Cueball, however, is currently just seeking food, which (one assumes) the DM-slash-Oracle is not.) [[Special:Contributions/172.68.229.25|172.68.229.25]] 12:48, 6 May 2025 (UTC)

My physics skills are rusty but 20 pounds is much more than the Planck mass. Doesn't this imply that Randall's dark matter particles would be black holes? [[Special:Contributions/172.68.243.107|172.68.243.107]] 10:05, 6 May 2025 (UTC)
:Yes, you are right that 9 kg is about 417,000,000 times more than the Planck mass (21.76 μg), but no, that doesn't imply that 9 kg dark matter particles would be black holes, for that particle can be larger than 417,000,000 Planck lengths (1 Planck length is c. 1.616255×10–35 m, so above 7 rm, this particle would not collapse into a black hole). [[Special:Contributions/172.68.245.81|172.68.245.81]] 10:23, 6 May 2025 (UTC)
Since it's Star Wars day and the 20 lbs. reference would be causing a massively large amount of mass, would it be safe to say that they "sense a great disturbance in the force?" [[Special:Contributions/67.84.20.42|67.84.20.42]] 10:20, 6 May 2025 (UTC)

Back in 2005, when the kg was an actual object's mass, there was an article about what a five pound (~2.268 kg) electron is, but it was deleted, for it is a "trivial result of special relativity". [[Special:Contributions/172.68.245.81|172.68.245.81]] 10:23, 6 May 2025 (UTC)

Since pounds are a measure of weight, and weight is a measure of the gravitational attraction between an object and its "planet", what is the reference planet that is being used to define the weight of the Dark Matter particle?
 Should we assume that Earth's surface is being used as the reference, even though we have no measurements that suggest DM particles are around us, and no reason to assume that the particles would even notice that Earth has a "surface"?
 If Randall wanted to use mass, then he should have used the imperial unit of slug, but I suppose saying that a DM particle is 0.62162 slugs might not give the readers quite the same impression as using 20 pounds. [[User:Galeindfal|Galeindfal]] ([[User talk:Galeindfal|talk]]) 13:38, 6 May 2025 (UTC)
:I might be missing some humour here, but the pound is actually a measure of mass, just like the gram, so it doesn't vary from a planet to another. You might have fallen prey to the second paragraph of the {{w|pound-force|wikipedia article about the pound-force}}, which states: 'Pound-force should not be confused with pound-mass (lb), often simply called "pound"' [[Special:Contributions/172.71.127.160|172.71.127.160]] 14:35, 6 May 2025 (UTC)

Is this, by chance, the Internet Oracle? [[Special:Contributions/104.23.187.126|104.23.187.126]] 13:49, 6 May 2025 (UTC)
:I don't see anything like the pentagram with candles at its web site. The comic seems more like they're summoning a daemon. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 14:10, 6 May 2025 (UTC)

Any idea where Randall came up with "20 pounds"? Why not 19 or 21 (blackjack!)? Why not use Newtons (too figgy?)? Only thing I can think of is that, in America at least, many people think they are "about 20 pounds overweight." I think that's too much of a stretch (pants???) to be the answer here. [[Special:Contributions/172.68.27.170|172.68.27.170]] 14:07, 6 May 2025 (UTC)
:I think it's just humorous, adding to the imprecision / casualness of "about 20". Imperial measurements feel "less scientific" than metric. [[Special:Contributions/162.158.146.124|162.158.146.124]] 16:26, 6 May 2025 (UTC)
:The amount of people confusing mass and weight/force in this thread is pretty disappointing for an xkcd forum. You can't convert pounds into Newtons. [[Special:Contributions/162.158.172.143|162.158.172.143]] 16:38, 6 May 2025 (UTC)
:The poster meant Kilograms rather than Newtons I assume. Under the assumption that the oracle is satire for large language models and AI chats, the "20 pounds" shows the kind of tone and data the AI has been tuned to provide. It's a way they behave when outside the core domain they are well-trained for, producing a certain brand of mistakes, awkwardnesses, and uncanny valleys, that may be quite humorous when first encountered. [[Special:Contributions/172.70.111.77|172.70.111.77]] 22:33, 6 May 2025 (UTC)
I don't think it's accurate to say (as the explanation does right now) that 20 lbs is too little to detect through gravitational interaction. Throwing some numbers together: a 20lbs-sphere of Osmium, the heaviest stable element, is about 4.5cm in radius. If a 20lbs point mass flies by just above the surface of that sphere, it would generate a gravitational force of about 2.5 micronewtons (hooray for Gauss's theorem). That's the weight of a few grains of salt - small, but definitely detectable. If they're all really really fast, or there's always lots of them around at any given time or something, that might wash out any measurements (someone more knowledgeable about dark matter can probably comment what the expected velocity and flux density of 20lbs-dark-matter-particles would be where we are). But in principle, rather measurable! [[Special:Contributions/162.158.172.142|162.158.172.142]] 17:00, 6 May 2025 (UTC)

"A particle that interacts with nothing except gravity, could only be detected by a gravitational telescope." -- Detected by a whatnow? Is that a thing which exists? Google had nothing for "gravitational telescope" when I searched for it. 
Additionally, are there any theoretical physicists out there who can weigh in on how plausible the "20 pound particle that doesn't interact with anything else" theory is? [[User:MeZimm|MeZimm]] ([[User talk:MeZimm|talk]]) 19:33, 6 May 2025 (UTC)
:Well, we haven't seen any such thing. But... that is of course the point. So, by logical extension, it ''must'' be true! :o [[Special:Contributions/172.70.58.130|172.70.58.130]] 21:05, 6 May 2025 (UTC)

There’s a few places online that I’ve seen people ''frustrated'' about dark matter because it’s been so hard to detect, even hoping that it turns out to be experimental error or otherwise not real (for example, [http://www.collectspace.com/ubb/Forum3/HTML/005665.html this collectSPACE thread]) just because it has been so “annoying” to readers of science news to not have a solution for so long. I think this comic could be kind of a joke along those lines (“what if it turns out dark matter ''doesn’t'' matter at all and we’ve been wasting our time?”) but played out in a ridiculous way because dismissing any scientific research, however frustrating, as “a waste of time” would be very un-XKCD.{{unsigned ip|104.23.90.225|21:32+22:01, 6 May 2025}}

Sounds an awful lot like a primordial black hole (a genuine dark matter hypothesis), doesn't it? Anyone who knows what the Hawking temperature of a black hole of that mass would be? (A black hole with a Hawking temperature less than 2.7 K would absorb more energy than it gives off in Hawking radiation and would therefore be stable in the current age of the universe.)

EDIT: answering my own question, apparently about 10²² K. [[Special:Contributions/162.158.91.110|162.158.91.110]] 23:20, 6 May 2025 (UTC)

Shouldn’t there be a comma after ‘well’ (when it is said by the oracle in the last panel), because there’s a comma after ‘dear oracle’ in the first panel? You can’t say that because there’s a break you don’t need a comma because there’s one in dear oracle [[User:Broseph|Broseph]] ([[User talk:Broseph|talk]]) 07:04, 7 May 2025 (UTC)
:Well. Perhaps it may need ''some'' punctuation. But... It doesn't necessarily have to represent a mid-sentence pause.
:Not that I like "you pause for breath, you add a comma" writing, also often used to justify the Oxford cases. Yes, a "clause-pause" coincides with a clausing comma. But if you're representing various other pauses or switches of tone there are mdashes, ellipses, parenthises of various types, the full-stop-slash-period and, in the comic example, the clear newline (and speechline?) acting as a rhetoric 'hold'. (The "Dear oracle," runs on ''into'' the next bit, so maybe that comma indicates symantic ''joining'' that was never required or implied with the effective "Well <mystical equivalent of taking a breath>" merely as a filled-pause.)
:Also note that it's not unknown for Randall to be inconsistent with whether or not to fully punctuate the 'ends' of speech-blocks (and has occasionally added them in post-publication edits; not entirely sure he's ever ''solely'' edited for that, but definitely has done when correcting some bigger mix-up/whatever). House-style seems to be fairly loose on that principle. It's effectively "reported speech", most of the time, so you can perhaps even put it down to the character's voice sort of... Trailing off, or even just halted altogether. [[Special:Contributions/172.68.229.67|172.68.229.67]] 09:46, 7 May 2025 (UTC)

"However, even if a particle does interact via a given force, an interaction is possible only if energy is conserved."
I am puzzled by this statement, which started the paragraph about 20 lbs being ludicrous for a fundamental particle. I think conservation of mass-energy is one of our most fundamental understandings of the universe. The rest of the paragraph does not develop further on the idea of conservation violation. If you know what was intended by this statement and think it is important, please clarify it and put it back in.
I liked the use of ludicrous mass. Brought to mind Space Balls and {{w|ludicrous speed}}. (I haven't thought of a way to make an appropriate tangential reference in the article.) [[Special:Contributions/162.158.41.36|162.158.41.36]] 19:34, 7 May 2025 (UTC)

3085: About 20 Pounds

2025-05-07T19:23:30Z

162.158.41.36: /* Explanation */ simplify sentences - hope I preserved the meaning

{{comic
| number = 3085
| date = May 5, 2025
| title = About 20 Pounds
| image = about_20_pounds_2x.png
| imagesize = 666x278px
| noexpand = true
| titletext = In addition to gravity, burritos interact through the strong, weak, and electromagnetic forces, which is believed to be a major contributor to their popularity.
}}

==Explanation==
{{incomplete|Created by a £20 20-LB PARTICLE. Are any categories missing? Don't remove this notice too soon.}}

The nature of {{w|dark matter}} is a significant unsolved problem in physics. We observe that galaxies spin faster than we expect based on the nearby observable matter. Likewise galactic motions indicate additional mass that we have not observed in other ways. Dark matter is the name we give to this mass. In the comic, [[Cueball]] and [[Ponytail]] consult an {{w|oracle}} to learn about dark matter.

The pentacle and candles suggest that the oracle is supernatural, summoned by an occult ritual; something which would present its own challenges to our understanding of the physical world. There may be a pun here, in that they may be using 'dark magic' to communicate with something from the 'dark realm' on the assumption that it will know about dark matter. However, the word 'dark' in dark matter simply means that we do not know how to observe it; we have no evidence that dark matter is evil or satanic (though [[Randall]] may consider it [[:Category:Comics with cursed items|cursed]]). The oracle is used very similarly to how people have been using and customizing {{w|large language model|large language models}}.

In general, not all forces interact with all particles; indeed, {{w|gravity}} is believed to be the only force that interacts with everything we have observed. If a force doesn't interact with a particle, then the particles existence cannot be directly observed via disturbances in that force. In particular, something that doesn't interact with electromagnetism cannot be 'seen', as photons will pass through it relatively unaffected, and likewise cannot be felt, because collision is a side effect of the {{w|Pauli exclusion principle}}.

Even {{w|neutrino}}s—famous for {{what if|73|interacting with ''almost'' nothing}}—still interact via the {{w|weak force}}, allowing them to be detected with sufficiently large tanks of dense material (as most atoms interact with the weak force, however weakly). A particle that interacts with ''nothing'' except gravity could only be detected by a {{w|LIGO|gravitational telescope}}.

However, even if a particle does interact via a given force, an interaction is possible only if energy is conserved. The particles mass is described vaguely as ''about twenty pounds'' (roughly 10 kilograms), in line with how apparently all-knowing oracles legendarily avoid unambiguous statements. This is an absolutely ludicrous amount of energy for particle physics. Any interaction would have to involve an equally ludicrous amount of other particle mass being in exactly the right place and time, a coincidence that might be so rare that one would not expect it to occur ever in the history of the universe. By comparison, the {{w|top quark}}, the heaviest single particle we have observed, with a mass over a hundred times that of the proton, is around a tenth of a trillionth of a trillionth of a pound.

Under more normal circumstances, we might still hope to observe the properties of the particle via creating it ourselves under controlled laboratory conditions. But again, there is no reasonable way to focus the energy required into a single particle interaction. The {{w|Large Hadron Collider|most powerful particle accelerator in the world}}, for example, peaks at about ten thousand times the mass of the proton—a solid billion times less energy than required—so it's out too.

Despite all this, twenty pounds is also much too ''small'' to be detectable via gravitational interaction—its {{w|Perturbation (astronomy)|influence on the orbits of planets}}, say, or the strength of its {{w|gravitational lensing}} effect, would be entirely negligible. Thus in the scenario posed by the comic, there is no plausible way to observe more about dark matter while on Earth. Even if we did find some such particles naturally occurring, and had instruments that could measure such small gravitational forces, since it would interact only via gravity, the only properties it could have other than mass would be its decay rates from other particles—which, again, would all be essentially nil due to its mass.

The oracle proceeds to break expectations by suggesting that Ponytail and Cueball go out for {{w|burrito|burritos}}, something generally considered non-scientific.{{cn}} When faced with the apparent futility of continuing to try to investigate dark matter, the oracle predicts that going out for burritos is precisely as productive as any other approach—i.e., not at all. It justifies the suggestion by burritos being "pretty" good, again neither exactly quantifying the oracularity, and likely not even giving the optimal idea (for choice of food, or of any other "what now?" diversion that it might give).

The title text observes that burritos interact through all four known {{w|fundamental interactions}}, making burritos popular. The electromagnetic force mediates the chemical reactions leading to a burrito's taste, the strong force keeps atomic nuclei together, and gravity gives burritos heft, all of which are helpful for enjoying them. It's hard to see how the weak force, which takes part in radioactive decay, helps with burrito enjoyment or popularity, but the weak force is responsible for the nuclear fusion that allowed the complex elements of the burrito to exist in the first place.

The previous comic [[3084: Unstoppable Force and Immovable Object]] dealt with particles which do not even interact with gravity.

==Transcript==
:[Cueball and Ponytail are standing in front of a pentacle with lit candles at the corners. A black sphere, the oracle, is floating above the middle of the pentacle.]
:Ponytail: Dear oracle,
:Ponytail: What is the nature of dark matter?
:Oracle: It's about 20 pounds.

:[Close up of oracle]
:Off-panel: What?
:Oracle: Dark matter is a particle. It weighs about 20 pounds.
:Oracle: It only interacts through gravity.

:[Same view as first panel]
:Cueball: Only gravity, huh?
:Cueball: So none of our experiments are really going to tell us any more about it, then.
:Oracle: Afraid not.

:[Same view as first and third panels, except Cueball lifted his forearm.]
:Cueball: So what do we do?
:Oracle: You should go out for burritos.
:Ponytail: How will that help?
:Oracle: Well
:Oracle: Burritos are pretty good.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Physics]]
[[Category:Food]]

3076: The Roads Both Taken

2025-04-15T20:45:19Z

162.158.41.36: /* Explanation */ remove random line breaks in explanation

{{comic
| number = 3076
| date = April 14, 2025
| title = The Roads Both Taken
| image = the_roads_both_taken_2x.png
| imagesize = 361x362px
| noexpand = true
| titletext = When you worry that you're missing out on something by not making both choices simultaneously by quantum superposition, that's called phomo.
}}

==Explanation==
{{incomplete|Simultaneously created by and not created by SCHRÖDINGER'S LYRICIST - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic is a parody of the first and fourth stanzas of {{w|Robert Frost}}'s 1915 poem "{{w|The Road Not Taken}}". The joke is that, while the human narrator of Frost's poem (presumably Frost himself), confronted with two paths, could only take one of them, and is left to [[584: Unsatisfied|contemplate the consequences of his choice]], the photonic narrator of the parody, thanks to {{w|Quantum superposition|quantum physics}}, is not compelled to choose one path over the other, and is left to contemplate the {{w|Wave interference#Quantum interference|consequences of that choice}}.

The title text humorously conflates FOMO (Fear Of Missing Out) with PHOMO (presumably PHOton Missing Out), the concern over lost opportunities from choosing one path only, instead of both. FOMO is concern over lost opportunities from choosing one path over another (or choosing neither).

This comic was posted on April 14, [https://www.quantum.gov/happy-world-quantum-day-2025 World Quantum Day].

{| class="wikitable"
!Original stanza
!Parody
!Explanation
|-
|Two roads diverged in a yellow wood, And ''sorry I could not travel'' both ''And'' be one traveler, ''long I stood'' ''And looked down one'' as far as I could ''To where it bent'' in the undergrowth;
|Two roads diverged in a yellow wood, And ''so of course I traveled'' both ''Though'' be one traveler, ''still I could'' ''Explore down both'' as far as I could ''Beyond the bends'' in the undergrowth;
|In the original, the human narrator, operating at the scale of classical mechanics, contemplates the necessary choice between two mutually exclusive paths. In the parody, the photon, operating at the scale of quantum mechanics, readily explores both paths. At quantum scale, the "roads" and "yellow woods" are metaphorical.
|-
|I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I— I took ''the one less travelled by,'' And that has made ''all the difference.''
|I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I, I took ''them both and recombined,'' And that has made ''interference.''
|In the original, the human narrator reflects subjectively on the (anticipated?) impact of the choice of road - whether for good or ill is not explicitly stated. In the parody, the photon states objectively the result ({{w|Wave interference#Quantum interference|quantum interference}}) of taking both paths at once.
|}

The parody maintains the same rhyme scheme as the original, ABAAB. In the fourth line of the last stanza. "recombined" doesn't {{w|Perfect_and_imperfect_rhymes|perfectly}} rhyme with "sigh" and "I", but it shares the vowel in the last syllable, a form of {{w|assonance}}, and can be considered an {{w|Perfect_and_imperfect_rhymes#Imperfect_rhyme|imperfect rhyme}}.

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

:[A photon recites a poem:]
:Two roads diverged in a yellow wood,
:And so of course I traveled both
:Though be one traveler, still I could
:Explore down both as far as I could
:Beyond the bends in the undergrowth...

:...I shall be telling this with a sigh
:Somewhere ages and ages hence:
:Two roads diverged in a wood, and I,
:I took them both and recombined,
:And that has made interference.

:[Caption below the panel:]
:Photon poetry

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

3076: The Roads Both Taken

2025-04-15T20:41:42Z

162.158.41.36: /* Explanation */ split complex sentence

{{comic
| number = 3076
| date = April 14, 2025
| title = The Roads Both Taken
| image = the_roads_both_taken_2x.png
| imagesize = 361x362px
| noexpand = true
| titletext = When you worry that you're missing out on something by not making both choices simultaneously by quantum superposition, that's called phomo.
}}

==Explanation==
{{incomplete|Simultaneously created by and not created by SCHRÖDINGER'S LYRICIST - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

This comic is a parody of the first and fourth stanzas of {{w|Robert Frost}}'s 1915 poem "{{w|The Road Not Taken}}". The joke is that, while the human narrator of Frost's poem (presumably Frost himself), confronted with two paths, could only take one of them, and is left to [[584: Unsatisfied|contemplate the consequences of his choice]], the photonic narrator of the parody, thanks to {{w|Quantum superposition|quantum physics}}, is not compelled to choose one path over the other, and is left to contemplate the {{w|Wave interference#Quantum interference|consequences of that choice}}.

The title text humorously conflates FOMO (Fear Of Missing Out) with PHOMO (presumably PHOton Missing Out), the concern over lost opportunities from choosing one path only, instead of both. FOMO is concern over lost opportunities from choosing one path over another (or choosing neither).

This comic was posted on April 14, [https://www.quantum.gov/happy-world-quantum-day-2025 World Quantum Day].

{| class="wikitable"
!Original stanza
!Parody
!Explanation
|-
|Two roads diverged in a yellow wood, And ''sorry I could not travel'' both ''And'' be one traveler, ''long I stood'' ''And looked down one'' as far as I could ''To where it bent'' in the undergrowth;
|Two roads diverged in a yellow wood, And ''so of course I traveled'' both ''Though'' be one traveler, ''still I could'' ''Explore down both'' as far as I could ''Beyond the bends'' in the undergrowth;
|In the original, the human narrator, operating at the scale of classical mechanics, contemplates the necessary choice between two mutually exclusive paths. In the parody, the photon, operating at the scale of quantum mechanics, readily explores both paths. At quantum scale, the "roads" and "yellow woods" are metaphorical.
|-
|I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I— I took ''the one less travelled by,'' And that has made ''all the difference.''
|I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I, I took ''them both and recombined,'' And that has made ''interference.''
|In the original, the human narrator reflects subjectively on the (anticipated?) impact of the choice of road - whether for good or ill is not explicitly stated. In the parody, the photon states objectively the result ({{w|Wave interference#Quantum interference|quantum interference}}) of taking both paths at once.
|}

The parody maintains the same rhyme scheme as the original, ABAAB. In the fourth line of the last stanza. "recombined" doesn't {{w|Perfect_and_imperfect_rhymes|perfectly}} rhyme with "sigh" and "I", but it shares the vowel in the last syllable, a form of {{w|assonance}}, and can be considered an {{w|Perfect_and_imperfect_rhymes#Imperfect_rhyme|imperfect rhyme}}.

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

:[A photon recites a poem:]
:Two roads diverged in a yellow wood,
:And so of course I traveled both
:Though be one traveler, still I could
:Explore down both as far as I could
:Beyond the bends in the undergrowth...

:...I shall be telling this with a sigh
:Somewhere ages and ages hence:
:Two roads diverged in a wood, and I,
:I took them both and recombined,
:And that has made interference.

:[Caption below the panel:]
:Photon poetry

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

Burlap

2025-03-26T23:25:33Z

162.158.41.36: rv vandalism

{{comic
| title = Burlap
| image =
| lappend = burlap
| extra = yes
| before = invest in burlap start of fortune
}}

==Explanation==
{{incomplete|This page was created recently. Add more information about it and mention if it has ever changed, etc. (see related comics [[NO]] and [[YES]]). There are many other xkcd pages like this and we're trying to decide how to add them to the wiki. Please see '''[[explain xkcd:Community portal/Proposals#Misc pages]]''' for more.}}

==Transcript==
:[There is no image, just text:]
: invest in burlap
: start of fortune

{{comic discussion}}

[[Category:No date]]