Talk:2817: Electron Holes

Explain xkcd: It's 'cause you're dumb.
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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. 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. 00:49, 21 August 2023 (UTC)
So a device that fires electrically charged projectiles. That sounds like a normal gun with a few extra features to me. guess who (if you want to | what i have done) 00:29, 29 April 2024 (UTC)

Would an electron "vacuum" be an electron hole gun? 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. 14:32, 21 August 2023 (UTC)

Is it worth mentioning that "pewpewpew" was one of the incorrect pronunciations of Perseids in 2814? Barmar (talk) 05:34, 19 August 2023 (UTC)

Foreshadowing! Note it there? 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? 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.
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. 14:32, 21 August 2023 (UTC)
Calling myself out for handwaving. I have no idea how to turn an electric field into a beam. It would be just like the electron hole gun. Maybe with EM. Does Randall conflate guns that fire in a straight line with electron guns that emit electrons which then behave like electrons rather than bullets or lasers? 05:56, 22 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! 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" 14:49, 20 August 2023 (UTC)
I’m surprised nobody is mentioning an antimatter beam (edit: oh, positrons below, oops). This would eradicate matter in its brilliant path. But you could make a beam of nothing in an environment where the 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. 14:32, 21 August 2023 (UTC)
For sure a beam of nothing can exist - it's called Reality TV. 09:57, 21 August 2023 (UTC)

When the 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. 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! 10:23, 19 August 2023 (UTC)

I firmly believe the printer deserved it. It knows what it did.

I'm honestly surprised to see no mention of toner printers, or even conjecture on why it's a printer that the electron hole gun is being fired on. Maybe an another reason the physicist is upset is that he's messing up her currently-printing document? - Vaedez (talk) 11:51, 26 August 2023 (UTC)

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".
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 - 19:15, 21 August 2023 (UTC)

Anode ray[edit]

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. 07:05, 20 August 2023 (UTC)

Isn't a positive ion an atom missing an electron? Couldn't you make an anode ray tube that emits charged semiconductor dust? The quasiparticles are the missing electrons in the matter. 05:38, 22 August 2023 (UTC)
For sure you can make a beam of positively charged ions - and that's the first thing I thought of with the "electron hole gun".
But . . . the context pretty much says that the gun is sending the holes only, without any surrounding matrix. That is what is "impossible". 18:11, 22 August 2023 (UTC)
Holes always imply surrounding negative charges. They are, specifically, a way to discuss the flow of net positive charge in a sea of negative charges. If you work with them this becomes quite clear. 23:38, 27 August 2023 (UTC)

Who is firing the beam?[edit]

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 Dirac sea." That very linked Wikipedia article says that the Dirac Sea is not the QED vacuum, that they are equivalent but different models. Nitpicking (talk) 02:20, 21 August 2023 (UTC)

I could guess Cueball holding an anode ray gun a little. 05:42, 22 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. 17:24, 21 August 2023 (UTC)

It might depend on the kind of physicist; one who deals with semiconductors wouldn't use "electron hole" to refer to positrons. It's pretty clear that the beam in the cartoon is not a stream of positrons, which would be reacting with the electrons in the air and releasing high-energy photons. It's the difference between "fantastic behaviour of a thing that doesn't really exist" and "behaviour that violates the known properties of a thing that does exist". Perhaps the ST:TNG Enterprise needs to be swept periodically to remove all of the lowadekions it's picked up, fine, but it's a bad thing to take away all of the baryons. BunsenH (talk) 01:06, 22 August 2023 (UTC)
*"an electron hole is indistinguishable from a positron"* - oh, an electron hole is very, very distinguishable from a positron. They hold the same charge, so they are the same in that respect, but otherwise they have quite a lot of different characteristics. For one thing a positron has mass whereas an electron hole, not so much.
an electron hole in solid state has an effective mass. I renew my original point. Electron holes and positrons are the same thing. 16:56, 24 August 2023 (UTC)
If you shot out a beam of electron holes (however you are planning to manage that) and then followed it up by shooting a beam of positrons, I very well guarantee that you are going to be able to tell that the two are vastly different things. You might not even need any special equipment to do so . . . 18:16, 22 August 2023 (UTC)
My impression from the references given in this discussion is that the phrase "electron hole" can have two different meanings, in different areas of physics: semiconductors and Dirac field theory. I'm familiar with only the former, but the latter appears to be attested and to be equivalent to positrons. A bit like how "exothermic" means nearly opposite things between biology and physics/chemistry. BunsenH (talk) 20:43, 22 August 2023 (UTC)
They're not really different meanings. It's just that the properties of a hole depend on the background. 16:57, 24 August 2023 (UTC)