explain xkcd - User contributions [en]

Talk:2817: Electron Holes

2023-08-21T19:15:09Z

172.70.211.114:

I must admit... I'm not entirely convinced that one _couldn't_ build an electron hole beam. It would probably be called a quasibeam, but I think it could be done. [[Special:Contributions/162.158.175.61|162.158.175.61]] 05:11, 19 August 2023 (UTC)
: You could clearly do this if you fired a beam of physical material to carry the holes. You could also find a way to stimulate the production of holes at a distance, maybe by inducing static charge with electromagnetic emission. [[Special:Contributions/162.158.62.192|162.158.62.192]] 00:49, 21 August 2023 (UTC)

Would an electron "vacuum" be an electron hole gun? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 05:30, 19 August 2023 (UTC)
: I think so! You’d create holes to pull the electrons, and the holes would travel away from the gun to the electron source as the electrons traveled to the gun. This is likely exactly what Randall is depicting. Could be wrong. [[Special:Contributions/172.70.230.36|172.70.230.36]] 14:32, 21 August 2023 (UTC)

Is it worth mentioning that "pewpewpew" was one of the incorrect pronunciations of Perseids in [https://www.explainxkcd.com/wiki/index.php/2814:_Perseids_Pronunciation 2814]? [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 05:34, 19 August 2023 (UTC)
: Foreshadowing! Note it there? [[Special:Contributions/162.158.86.182|162.158.86.182]] 08:11, 19 August 2023 (UTC)

Objection, Your Honor! Don't know if electron quasibeams (see comment above) can be done, but the "a beam consisting of a lack of something is not possible" in the current explanation is too wide. Think of antisound devices! I think a "vacuum beam" going through normal gas pressure is very possible. And what about the Meissner effect, which could be seen as a beam of absence of a magnetic field? [[Special:Contributions/198.41.242.211|198.41.242.211]] 07:25, 19 August 2023 (UTC)
:Anti-sound just exactly(/sufficiently) compliments the sound you're trying to 'remove'. On its own, it is sound in its own right.
::Sure, but it makes a region without sound from destructive interference. Beams take energy anyway. [[Special:Contributions/172.70.230.36|172.70.230.36]]
:Projecting a vacuum (which would, incidentally, quash sound except for that which travels round it or is caused by its creation/collapse) sounds like it needs a whole army of Maxwell's demons carrying their own 'portable hatches' to allow air molecules to leave the volume of the beam whilst batting away any that threaten to move into it. (That might be interesting to see, if noisy.)
::This might work at absolute zero? For example, you could electrically charge the particles of a motionless gas and then pull them using a focused electric field and make a beam that emits vacuum. [[Special:Contributions/172.70.230.36|172.70.230.36]] 14:32, 21 August 2023 (UTC)
:The Meissner Effect is an interesting (practical) version of this. Upon decreasing the possibility of an interior field, an identical increase is detetected immediately outside of it (conserving flux across the whole system, or so it seems to be/makes most sense).
:Which is not to say that there's no such thing as "a nothing", in the whole weird world of science, or variously vagues analogues to it (if you don't dig too deep, maybe). Some might suggest quantum vacuum decay might be the ultimate substantial 'nothing', but not that we know how to study it... let alone harness it. Yet! [[Special:Contributions/172.71.242.5|172.71.242.5]] 10:23, 19 August 2023 (UTC)
:Those aren't "beams of nothing" but rather "beams of things that cause another thing to be suppressed/expelled/cancelled" [[Special:Contributions/172.69.247.43|172.69.247.43]] 14:49, 20 August 2023 (UTC)
::I’m surprised nobody is mentioning an antimatter beam. This would eradicate matter in its brilliant path. But you could make a beam of nothing in an environment where there presence of something is controlled by another system, by engaging the system doing this. Shadows are maybe the most simple example of this. Shading a light source makes a beam of darkness. [[Special:Contributions/172.70.230.36|172.70.230.36]] 14:32, 21 August 2023 (UTC)
:For sure a beam of nothing can exist - it's called Reality TV. [[Special:Contributions/172.70.90.164|172.70.90.164]] 09:57, 21 August 2023 (UTC)

When the [https://en.wikipedia.org/wiki/Positron positron] was first predicted it was modeled as an electron hole, a gap in the hypothetical "sea" of negative-energy electrons filling all space. Sadly, AFAIK modern quantum field theory has done away with that idea, so while a gun that shoots a positron beam is theoretically possible, it probably wouldn't qualify as an electron hole beam. [[User:Hmj|Hmj]] ([[User talk:Hmj|talk]]) 08:03, 19 August 2023 (UTC)
:I (separately) mentioned positrons in an edit summary just now. Of course, adding the two concepts together makes for an even ''more'' ridiculous thing... A 'positron hole beam'. You know all those positrons we (don't, in general terms) have floating around us? This now projects a concentrated ''lack'' of them! [[Special:Contributions/172.71.242.5|172.71.242.5]] 10:23, 19 August 2023 (UTC)

I firmly believe the printer deserved it. It knows what it did. [[Special:Contributions/162.158.19.95|162.158.19.95]]

Electrical current was defined as the flow of positive charge carriers before it was understood that the negative charge carriers (electrons) were what was moving. When talking about semiconductor physics, this became a problem because we’re very concerned about what particles are actually moving around, so the mathematical fiction of “hole flow” was invented so we wouldn’t have to use negative signs everywhere in the math. An electron hole is a property of p-type semiconductors, a place where electrons can move into, which can also be described as the nonsensical but more mathematically convenient flow of holes in the opposite direction. By analogy, if you had a children’s shape-sorting box, you could build a catapult that threw around the blocks, but you couldn’t build something that threw around the holes in the lid that the blocks fit into.
:But... sure you could!? The blocks would function like pegs obstructing unaligned travel, & the "holes" could simply be panels that can only traverse the pegs when their holes are aligned. Just because a gap in a medium lacks one thing, doesn't mean it contains nothing, & the medium itself is necessarily still a thing. None of the math for a QED vacuum even works unless a space defined by masss-energy over time, is defined; there is no "nothing".
:[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 15:31, 21 August 2023 (UTC)

:Current sign is a convention, we could just as easily reverse the convention for proton and electron charge sign... that we haven't done so for one or the other is both a source of endless frustration, confusiong, and also, yet another XKCD comic [[567: Urgent Mission]] - [[Special:Contributions/172.70.211.114|172.70.211.114]] 19:15, 21 August 2023 (UTC)

== Anode ray ==

A contributor wrote, "Here, the electron hole gun might refer to the anode ray tubes." An anode ray is a beam of positive ions; these are actual particles and not "quasiparticles", and therefore the comic does not refer to them. [[Special:Contributions/162.158.86.243|162.158.86.243]] 07:05, 20 August 2023 (UTC)

== Who is firing the beam? ==

Are we so sure it's Beret Guy? Depending on how dangerous or destructive it is, it could be Black Hat? And is using the first person in the title text ("my") for a character like Beret Guy, instead of for a fictionalized Randall Monroe with weird hobbies, a departure from usual norms?

Quoting the article as of my writing, "It should be noted however, that a hole in the QED vacuum is a real particle, known as the positron. See the {{w|Dirac sea}}." That very linked Wikipedia article says that the Dirac Sea is ''not'' the QED vacuum, that they are equivalent but different models. [[User:Nitpicking|Nitpicking]] ([[User talk:Nitpicking|talk]]) 02:20, 21 August 2023 (UTC)

I disagree with the punchline here. a layman might be angry about this hypothetical device, but a physicist would understand that an electron hole is indistinguishable from a positron. [[Special:Contributions/162.158.158.118|162.158.158.118]] 17:24, 21 August 2023 (UTC)

2653: Omnitaur

2022-08-02T08:39:52Z

172.70.211.114: /* Explanation */

{{comic
| number = 2653
| date = August 1, 2022
| title = Omnitaur
| image = omnitaur.png
| titletext = "My parents were both omnitaurs, which is how I got interested in recombination," said the normal human.
}}

==Explanation==
{{incomplete|Created by AN OMNITAUR-HUMAN HYBRID - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Omnitaur is an {{w|anagram}} of {{w|minotaur}}, a mythical creature that was part man, part bull. "{{wiktionary|omni}}" is a prefix that means "all". The word is for instance known from the word {{w|omnivore}}, meaning all eating as compared to {{w|carnivore}} or {{w|herbivore}} (only eating meat or plant respectively). Given the combinations of animals used to create the omnitaur, it could be expected that it was also an omnivore.

An "omnitaur" would suggest that it would encompass all real and mythical creatures, and appears to be a hybrid or {{w|Chimera (genetics)|genetic chimera}} combined from 11 different creatures: {{w|Fish}}, {{w|lion}}, {{w|snake}}, {{w|shark}} (also a fish), {{w|bull}}, {{w|dragon}} (another mythical creature), {{w|horse}}, {{w|leopard}}, {{w|Sheep|ram}} (male sheep), {{w|human}} and {{w|bird}}.

This new creature has been inspired by the mythological {{w|minotaur}}, which has the head and tail of a bull and the body of a man, and who has given rise to its name. But many other inspirations can be found in mythology like the {{w|centaur}}, which has the upper body of a human and the lower body and legs of a horse; the {{w|manticore}} with a body of a lion and human face; a {{w|griffin}} with a lion's body and a eagle's head; a {{w|mermaid}} with a lower-body of a fish and upper body of a human; a {{w|Hippocampus (mythology)|hippocampus}} with the upper body of a horse and a lower body of a fish; a {{w|qilin}} with a body that resembles both a horse and a dragon; or the mythological {{w|chimera (mythology)|chimera}}, for which the genetic chimera is named, which has lion, snake, and goat body parts; But ultimately there are {{w|List of hybrid creatures in folklore|lots of hybrid creatures in mythology}}, so without word from [[Randall]] you're free to make your own conclusions.

The title text is a comment said by a human whose parents both where omnitaurs. This would be strange that such parents would not get offspring that was still omnitaur. Hence the "normal" human says "My parents were both omnitaurs, which is how I got interested in recombination. This references {{w|genetic recombination}}, which is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. The human thus has become interested in this, to find out if that could explain how the omnitaur parents could have ordinary human offspring. Since we don't understand omnitaur genetics, we can't evaluate whether that is a plausible claim. But since it seems to be only 1/11 human, the odds are 1/11 x 1/11 = 1/121 for getting a only human offspring, if it was simply a matter of the math... Of course if it worked like that, it would be hard to explain how a creature consisting of 11 different animal came into existence in the first place.

It is interesting that Randall chooses to mention fish and shark, given that sharks are fish, and he for sure knows this. It would have been like saying mammal for the lion part and then horse later... Also funny he includes dragons, since all the other animals are real animals.

In {{w|C. S. Lewis}}' {{w|The Chronicles of Narnia}}, the {{w|Magical_creatures_in_The_Chronicles_of_Narnia#Centaurs|centaurs}} are depicted eating two meals - a huge roast meal "to satisfy the man stomach" and a meal of grass "to satisfy the horse stomach", making it take quite some time for them to eat every morning. This could further support that the omnitaur is an omnivore. But given that there are still only need for two stomachs, one for grass and one for most other stuff, it may not take longer for the omnitaur to eat than for the Centaur. Although the bird beak may slow down the process quite a bit.

==Transcript==
:[A creature, the Omnitaur, is shown. It is a four legged animal divided into 11 segments, each segments is from a different animal. An arrow goes to each section from a label, most of the labels are above the animal, but the fourth and seventh segments labels are below the animal. The animal has a fish tail and cat like hind legs. The torso is divided into four segments, the first and last of these with scales, but only the last of these also with sharp scales at the top. The second torso segment is white and smooth, the third also white but with hair both above and below, those above merges with the sharp scales of the fourth torso segment. The front legs are horse like, the lower neck is from an animal with dark spots, the upper neck has rams horns, which goes over in the central part of a human head, with ears and hair (drawn like a real human, not like a xkcd stick figure) and finally the front of the face is a bird with its eyes and a beak shown. The labels are given here in the order of the segment of the animal from the back to the front (disregarding weather the label is written above or below the animal:]
:Fish
:Lion
:Snake
:Shark
:Bull
:Dragon
:Horse
:Leopard
:Ram
:Human
:Bird

:[Caption below the panel:]
:The Omnitaur

{{comic discussion}}

[[Category:Animals]]
[[Category:Biology]]