2035: Dark Matter Candidates

2018-08-20T16:09:15Z

108.162.229.238: Bees

{{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==
{{incomplete|Every section needs to be filled and explained. Do NOT delete this tag too soon.}}
{{w|Dark matter}} is a hypothetical 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 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. In cosmology, dark matter is estimated to account for 85% of the total matter in the universe.

This comic gives a set of possibilities of what dark matter could possibly be, charted by mass from smallest (given in {{w|Electronvolt#Mass|electronvolts}}) to largest (given in kilograms). Masses in the range 10-15 kg to 10-3 kg are given in grammes.

The joke in this comic is that the range of the mass of the possible particles and objects stretch over 81 powers of ten. [[Randall]] filled the gap between real small candidate particles and real large candidate objects with highly absurd suggestions.

;Axion
An {{w|Axion|Axion}} is a hypothetical elementary particle that might be a component of dark matter.

;Sterile neutrino
{{w|Sterile neutrino|Sterile neutrinos}} are hypothetical particles interacting only via gravity. It's an actual candidate for dark matter.

;Electrons painted with space camouflage
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 have a strong electric charge. Presumably, space camouflage is a positively-charged coating which prevents electrons from interacting with light. (Needless to say, this is not an actual candidate for dark matter.)

;Neutralino
A {{w|Neutralino|Neutralino}} is a hypothetical particle from {{w|Supersymmetry|Supersymmetry}}, not something made up by Randall Munroe that sounds vaguely like one. It's an actual candidate for dark matter.

;Q-ball
In theoretical physics, a {{w|Q-ball|Q-ball}} is a stable group of particles. 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.

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

;No-See-Ums
{{w|Ceratopogonidae|No-See-Ums}}, also called Ceratopogonidae, a family of small flies (1–4 mm long) who can pass through most window screens. Another joke candidate.

;Bees

;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.

;Space Cows
Cows are Bovines extensively farmed on Earth for milk and meat. Although there is folk lore concerning cows {{w|Hey diddle diddle|acheiving circum-lunar orbits}}, they have yet to be found elsewhere in the Universe.

;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 monolith from 2001: A Space Odyssey.

;Black Holes ruled out by:
{{w|Black hole|Black holes}} are known in sizes of a few sun masses (about 1030-1031 kg) as remnants of the core of former big stars and the real big ones at the centers of galaxies (millions or even billions of the mass of the sun.) But recent gravitational wave detection indicate that black holes at 50 or 100 sun masses also exist while 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.

Except the last item all range below the mass of the sun (2x1030 kg) while the smallest known black hole is about four sun masses.
* Gamma rays: If dark matter were black holes of this size, the black holes would be evaporating in bursts of {{w|Hawking radiation}}, and we'd see a buzz of gamma rays from every direction.
* GRB lensing: {{w|Gamma-ray burst|Gamma-ray bursts}} (GRBs) are the brightest events in the universe only been observed 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 often only detected by gamma-ray satellites in space but rarely at any other wavelengths. Measuring lensing effects would be very difficult.
* Neutron star data
* Micro lensing: {{w|Gravitational microlensing}} is a gravitational lens effect. This is a prediction by Einstein's General Theory of Relativity and was first confirmed in 1919 during a solar eclipse when a star nearby the sun was closer to the sun than it should be. 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 the dark matter.
* Solar system stability: Our {{w|Solar system|solar system}} is 4.5 billion years old and very stable since then. If not we wouldn't exist. If dark objects at 1024 kg - 1030 kg (mass of Earth until Sun) would resemble the dark matter there should be many of them even in the vicinity of our solar system and the system wouldn't be stable at all.
* Buzzkill Astronomers: Black holes above a certain size would be impossible to miss, due to the effects they have on nearby matter. But at the mass of some 1030 kg there must be many supernova remnants we still havn't found.

;Maybe those orbit lines on space diagrams are real and very heavy
Any diagram of our solar system (or any solar system) will show lines representing the path the planet takes around its sun. Since planets orbit in ellipses, there will be an ellipse for every planet. This 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 inner four planets, including the Earth, which would be a problem. Overall, not a very likely candidate.

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

: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

:1 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:Line graphs]]

2021: Software Development

2018-07-18T15:13:38Z

108.162.229.238:

{{comic
| number = 2021
| date = July 18, 2018
| title = Software Development
| image = software_development.png
| titletext = Update: It turns out the cannon has a motorized base, and can make holes just fine using the barrel itself as a battering ram. But due to design constraints it won't work without a projectile loaded in, so we still need those drills.
}}

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

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

{{comic discussion}}

Talk:1782: Team Chat

2017-01-06T16:32:21Z

108.162.229.238:

This is an xkcd about why the majority is wrong. ;) [[Special:Contributions/108.162.229.238|108.162.229.238]] 16:32, 6 January 2017 (UTC) seirl

Talk:1585: Similarities

2015-10-02T08:22:22Z

108.162.229.238:

;Origins

I've heard 50 Shades of Grey started out as Twilight fan fiction, but don't know how The Martian came to be. [[Special:Contributions/108.162.216.115|108.162.216.115]] 05:56, 2 October 2015 (UTC)

-- Still missing from the explanation is what kind of brand ''The Martian'' is about... -- [[Special:Contributions/162.158.114.217|162.158.114.217]] 08:18, 2 October 2015 (UTC)
:NASA? [[Special:Contributions/108.162.229.238|108.162.229.238]] 08:22, 2 October 2015 (UTC)

explain xkcd - User contributions [en]

2035: Dark Matter Candidates

2021: Software Development

Talk:1782: Team Chat

Talk:1585: Similarities