The efficiency would be much better than that, assuming bulk matter-antimatter annihilation (say, antihydrogen or anticarbon or something). Much of the energy in the outgoing products is in the form of kinetic energy that will be readily deposited in nearby material. For any mass-energy tied up in mesons: The most plentiful neutral product will be the \pi^0, which will give all its mass energy away as it decays to electromagnetic products (photons). For \pi^-, these will be ultimately captured by the nuclei of nearby material and their mass-energy will either become kinetic energy of resulting nuclear fragments, energy in nuclear de-excitation photons, or energy of \pi^0 mesons produced through quark charge exchange; this summarizes to getting essentially all the mass-energy of \pi^- back. Thus, only the mass-energy of \pi^+ is largely lost to neutrinos through its decay chain, at an average of about 100 MeV per \pi^+. All told, the average efficiency if you catch everything other than neutrinos is in the ballpark of 85%.
(If the matter-antimatter is something else, like electrons and positrons, then of course this could be better.)
That doesn’t seem right. Black holes’ blackbody temperature (at least for the black holes we have evidence of) is crazy small, like 10-12 eV and below. At least two neutrinos are known to be way heavier than that (with the third neutrino potentially just as way-heavier). So, almost none of the black hole mass will go into neutrinos.
For a stellar mass black hole, the only options are gravitons (even more of a loss than neutrinos), photons, and (maybe) the lightest neutrinos (and we’re not even certain about the photons). But if the lightest neutrinos are below that temperature, they still have the largest share, mostly just because they have more modes available than photons or gravitons do (though there are also differences between bosons and fermions).
But evaporation of a stellar mass black hole is not worth discussing as a power source, because of that ludicrously low temperature. You need a smaller, hotter hole for that, at which point all of the neutrinos are definitely available.
Though, to be fair, once the hole gets small enough, you can get everything in the radiation, and so eventually neutrinos would drop to a smaller total share again, just because there’s a lot more everything than there are neutrinos (though some of those everythings would themselves decay into neutrinos, among other things).
And on the whateverth hand, at some point, when you get small enough, we have no friggin’ idea what, if anything, comes out of a black hole, because we’d be pushing up against quantum gravity, which we have no knowledge about.
Of the mass-energy released in the proton-antiproton annihilation (1,877 MeV), about half ends up as neutrinos, one-third as gamma rays, and one-sixth as energetic electrons and positrons.
The source is consistent with what you said about the \pi^0, but that’s only 1/3 of the total, and the charged pions it sounds like the majority of mass-energy ends up in the neutrinos.
Were we talking about a power source? I lost track of the hypothetical purpose. Yeah, if you could magic a Goldilocks small-but-not-too-small black hole into existence then there is a bite in mass range where neutrinos would carry away most of the energy. But that’s certainly not a general conclusion. (Back of the envelope: black hole masses between 1013 kg and 1020 kg would radiate mostly to neutrinos. Above and below that, not.)
The source is just all made up, unfortunately. The paragraph starting “The annihilation of a proton with an antiproton is shown in Fig. 2b” and the figure itself bear no resemblance to reality. It looks like the author of that write-up and the site in general is a science fiction enthusiast who has written articles to provide some scientific foundation for those sharing his enthusiasm. He’s been more prolific than careful, it appears.
Proton-antiproton annihilation is a strong-force process, so his diagram’s fundamental emission of gammas, muons, and neutrinos is already problematic. In reality, you get a random draw from a messy menu of mostly mesons, subject to conservation laws and kinematic shaping. Pions, being the lightest meson, show up most readily. And in almost all cases, the “released” energy is mostly kinetic and will be ultimately deposited, even without the eventual recovery of some of the mass-energy as well.
(Aside: In writing this reply I realize that I made a mistake en route to my ~85% number above. Replace that with ~92% efficiency [i.e., non-neutrino energy].)
I’ll also note that @Pasta is assuming that the annihilation is happening in the context of a bunch of other matter, so the immediate byproducts have a chance to give up most of their energy before they themselves decay. It’d be less efficient with isolated particles in a vacuum. Though other matter probably is a more realistic scenario.
There’s also this source, from noted physicist/sci-fi author (that combo again!) RL Forward:
It again confirms that pions are the most prevalent product. But only estimates that 35% of the energy is captured by a 100 atm hydrogen pressure chamber. The pion gives up some KE before decaying into a muon and a neutrino. Then the muon gives up all of its KE before decaying into an electron and two neutrinos.
The 35% figure does include gamma losses as well as chamber wall losses, so I don’t know if it supports the other 50% number. But it’s not fantastically efficient, either way.
Yes, good to point out explicitly. I was indeed assuming the goal was to catch all the catchable outgoing particles and thus to run the thought experiment inside “stuff”.
Interesting. Yes, this would look to be a reliable source on the face of it. All the same, though… (I suppose to Cramer’s credit, that article was originally written in 1979, and at that point quantum chromodynamics was still being tested at a basic level, and we had not yet even observed the weak bosons.)
I will look at that reference in more detail tomorrow, but a 100 atm hydrogen pressure chamber is a rather niche way to capture the energy, and one that he puts forth (it appears at first glance) only in the context of a specific space ship propulsion design with certain spatial and mass constraints and where he’s trying to directly heat the hydrogen to shoot it out as the propellent.
This will be a huge loss, essentially throwing away all neutral pion energy in his design.
My approach is more general, in the vein of: take a big block of iron (couple meters across is ample) and stick your reaction products inside. Neutrinos escape, but circa 90% of the energy will be retained and will heat up the iron (to drive a boiler or something, say).
That’s fair. A hydrogen chamber isn’t the only way to capture the energy. I don’t know that it’s precisely niche, in that spaceship propulsion is one of the few cases where antimatter might really make sense, and hydrogen makes a lot of sense as a working fluid, but that’s by no means the only possible application.
Having just caught up with this thread (especially a segment from the 13th) I have to say that Whack-a-mole and Dr.Strangelove’s avatars are too similar to each other.
It’s hard to even classify this as a potential scam because it’s just so silly. I thought it had to be something to troll the copy/paste news sites like the above, or maybe a masters project at a business or marketing school that was so effective it got accidentally picked up. But then I saw that they have a whole website (which I have chosen not to directly link here) with “details” and press releases and stuff. It still has to be a very dedicated group of trolls and not anyone trying to pretend this is real, but there’s more effort put into their web content than I would have expected. (I like how their newest articles just open a fresh jar of “Artificial Intelligence” to mix into their technology word salad, to stay with the zeitgeist.)
I would say that it can’t possibly be serious, and must be either a joke or a scam. But I’ve seen reputable publications like Scientific American fall for even more ludicrous schemes.
Oh man, they even tout a “patent” that’s actually just an international patent application. You can see it all here:
14 out of 15 claims don’t even mention what this thing is supposed to do, and even claim 15 only refers to vague " invisible solar energy". And even then, if you look at the English translation of the International Preliminary Report on Patentability, the examiner calls them out for describing something contrary to well-known science.
Their basic claim is to “1. foil of metal or a metal alloy, characterized in that the foil has a coating comprising graphene and silicon.”
Their second last paragraph tells the tale:
The mode of operation can be summed up as follows: Nature has relatively “wide-meshed” molecules, so that the neutrinos fly through because of the low mass, so the atoms in the molecules as well as the molecules in the material structure must be so tightly “packed” that part of the neutrinos can not fly through without touching the particles. The surface of the film therefore has nanotechnologically processed structures, so that analogous to a mechanical pendulum chain, the molecules abut each other and thus from the mass and the kinetic energy of a molecule flow and current flow is created (so-called lattice-guiding effect). This is analogous to a current flow in a line to understand: by magnet and coil, the molecules are set in motion in the generator and so we can use the electricity.
I’m pretty sure most people here can spot the holes in this theory.
Of course, this hasn’t issued to an actual patent anywhere in the world I can find, and since it was filed in 2016, it really should have issued if there was anything to it. 8 years is a long time in the patent examination world.
It’s been a while since I debunked a bullshit patent application for fun!
The many replies to this post doesn’t seem to address:
Red Mercury Red mercury - Wikipedia
was alleged to be so energetic, you could initiate thermonuclear fusion…iow, an H-bomb without an A-bomb “trigger”.
