11 ms·

Dead Stars Don’t Radiate

246 points by thechao 1y ago

fishsticks89 1y ago
https://archive.is/mG1KS https://archive.is/mG1KS
- Wowfunhappy 1y ago
  As best I can tell there's no paywall on TFA, so I really don't think there's any reason to go through archive.is, which adds its own advertisements (if you don't block them).
  - Out_of_Characte 1y ago
    archiving isn't just to circumvent a paywall. There's also the HN hug of death, possible geoblocks or an actual interest in archiving the article as it was written at the time these comments.
nimish 1y ago
There's an issue this highlights and it's not that the original authors were stupid so much as there's clearly a lot of knowledge held in silos. That's not a good thing if your goal is to advance everyone's knowledge. Whatever is going on in academia is failing relatively closely related fields which is not good.
- kurthr 1y ago
  Well, there's another aspect which is that the original authors and pop-sci journalists don't seem to be able to understand where they went wrong or how outrageous their claims are, precisely because their jobs depend on not understanding. The could have corrected it. We could not still be circling this drain 2 years later, but we are. Kinda classic. Kinda boring.
  - EA-3167 1y ago
    It helps that this is a genuinely difficult process to understand and requires an enormous fluency with QFT. Most people who fit that bill have better things to do with their time than write popular science articles or correct them.
- tekla 1y ago
  99.999999999% of people do not have enough knowledge to even dream of beginning to understand a majority of research. Adults can barely read, much less be able to pass Calc 1.
  - lupire 1y ago
    Wher are you hiding 92 Billion people?
  - coolcase 1y ago
    That percentage of the human population is everyone.
    - saagarjha 1y ago
      I guess they left out a bit for Einstein's brain (but not the rest of his body).
- ajross 1y ago
  It certainly wasn't in "silos", it's all on arxiv! But yes: the world is complicated and it's easy to make mistakes outside your core field. The point of the scientific process is to get things in front of eyeballs who can spot the mistakes, c.f. the linked blog post. Then everyone fights about it or points and laughs or whatever, and the world moves on. The system worked. What the process is not good at is filtering new ideas before people turn them into news headlines. And sure, that sucks. But it's not a problem with "academia failing", at all. The eyeballs worked!
  - deleted 1y ago
    [deleted]
- moefh 1y ago
  > There's an issue this highlights [...] there's clearly a lot of knowledge held in silos. I think the real issue this highlights -- which is something everyone knows and still everyone does -- is that people love to spread and discuss sensational stories, and no one likes to hear naysayers ruining the fun. Look the discussion of the original story here in HN[1]. There's a comment by A_D_E_P_T way down in the discussion explaining why the paper is nonsense and pointing to one of the replies objecting to it mentioned in the article from this post. That comment was downvoted by HN readers. I know because it was greyed out when I upvoted it days ago. So there's no knowledge silo -- us simple folk just want to discuss the newest breakthrough without looking too hard, because that spoils the fun. [1] https://news.ycombinator.com/item?id=43961226 https://news.ycombinator.com/item?id=43961226
  - gnramires 1y ago
    I also think this kind of idea can be fun speculation, but I think there are better things to have fun that aren't promoting wrong ideas (like literal Science Fiction speculation!). When we can build fun on top, the physics of our reality doesn't need to be (academically) fun by itself :)
  - ryandrake 1y ago
    I don't think there's a lack of skepticism on HN of all places. Every article that gets posted that discusses even a mild scientific result brings at least one HN commenter out of the woodwork to dunk on it. You can bank on it--there is always That Guy who has to argue against it, whether he's right or not. Also, the comment you reference was probably downvoted because of the tone, not because of some HN bias against naysayers. Starting out your comment with "It's nonsense." is about as conducive to a productive conversation as starting it out with "You're wrong."
    - andrewflnr 1y ago
      The point of a statement like "it's nonsense" is to prevent a conservation that should not happen, because it will be dumb. It's the right thing to say iff it's correct.
    - 1y ago
- kmm 1y ago
  Is it really that siloed? The condition mentioned in the article (there being a global timelike Killing field) is discussed in all introductory texts on quantum field theory in curved spaces, it's even present in the first few paragraphs of the relevant Wikipedia article[1]. Even if it doesn't apply here, the authors ought to have mentioned why not. I don't think they were stupid per se, nor malicious, but perhaps cavalier in pushing a result with such unexpected consequences without getting a consult. 1: https://en.wikipedia.org/wiki/Quantum_field_theory_in_curved_spacetime https://en.wikipedia.org/wiki/Quantum_field_theory_in_curved...
- boznz 1y ago
  A Lot of these physics papers are interesting but ultimately just noise. An untested Theory is NOT fact, it's just someone (with or without a PhD) pulling something out of their arse that might explain things. Most of cosmology and physics is still theory (even the big bang, and string theory) and even if 90% of theory fits facts, they could still be wrong. I am seeing more and more of these un-testable theories, built on other un-testable theories, citing other un-testable theories, this is why theoretical physics is in a crisis IMHO. MY mother and father also have an untested theory that explains all this too it's called "God", most Sci-Fi authors have plenty, and I am sure AI's will soon add to this pile. Kudos to those scientists that create testable papers or experimentally prove stuff.
  - michaelmrose 1y ago
    We call every model no matter how well founded a theory. An untested theory might be better called a hypothesis. This mistake of language plays into the weirdos who opine we should disregard inconvenient ideas because they are just a theory failing to understand the difference between their own usage and the scientific usage.
- grues-dinner 1y ago
  > clearly a lot of knowledge held in silos. I don't think it's quite that, since the eventual goal is to publish, not only publicly, but as publicly as possible. More like it seems like everyone tends to hold their cards quite close to their chest until the moment of pre-print publication. Which means you can be working on something that someone could have told you months or years ago you have a problem. The scientific equivalent of polishing a branch before making a pull request, only to be told "this has a huge memory leak and moreover what you want already works if you use this other API". I'm not really sure there's a human-scale solution: the research landscape is so vast that you can't connect everyone to everyone else and have everyone in need of valuable input get it, and have everyone able to give it not be inundated with half-baked rubbish. Even if you assume everyone from the top to bottom has pure motivations and incentives for doing the research in the first place (in the pull request analogy CVE spammers, for example). Perhaps not having the universities themselves so keen for PR that they'll slap a press release together about anything that looks clickable without due diligence would at least prevent making a public spectacle outside of the academic circle now and then, but it wouldn't solve the fundamental issues.
- bmitc 1y ago
  I think it's just an intractable problem at this point. There's probably millions of physicists on Earth. Everyone working in a company knows just how hard it is to get even hundreds of people to agree and read and understand the same things. The fact is, there are just too many people doing too many things. When any technical paper sounds like gobblygook to even people in the same field but in a different specialty, it's no surprise this happens, especially when coupled with the modern pressure to scientifically publish and modern "journalism" trends.
- deleted 1y ago
  [deleted]
gruturo 1y ago
Without a gravity well whose escape velocity exceeds c, how are they supposing hawking radiation happens in this scenario? Both virtual particles-antiparticles survive (and promptly disappear because one didn't just cross an event horizon).
- Sharlin 1y ago
  That one's a big white lie of how Hawking radiation works. It's not even an approximation, just a far-fetched metaphor that Hawking made up, presumably to satisfy science journalists.
  - raattgift 1y ago
    Hawking 1974, "Black hole explosions?" (Nature paywall) <https://www.nature.com/articles/248030a0 https://www.nature.com/articles/248030a0> (sci-hub antipaywall) <https://sci-hub.se/https://www.nature.com/articles/248030a0 https://sci-hub.se/https://www.nature.com/articles/248030a0> ("... the time dependence of the metric during the collapse will cause a certain amount of mixing of positive and negative frequencies [...] Part of this wave will be scattered by the curvature of the static Schwarzschild solution outside the black hole ... Another part of the wave will propagate backwards into the star") was certainly not for science journalists and is not at all "far-fetched". The only missing piece here is possibly discussion of his particular approach to second-quantization of the matter fields and how one might interpret that; Hawking's peers fifty years ago did not need assistance there. This was followed in detail by Hawking 1975 (open access via Project Euclid) <https://projecteuclid.org/journals/communications-in-mathematical-physics/volume-43/issue-3/Particle-creation-by-black-holes/cmp/1103899181.full https://projecteuclid.org/journals/communications-in-mathema...> where the most relevant bit surrounds eqns (2.27-28) and there is nothing wrong with talking about signed "contributions to the probability flux into the collapsing body" (as opposed to identifying those contributions as particles). Hawking himself wrote simpler pop-sci explanations in a number of places, including his book, where a reader would not be expected to understand how canonicalizations of wave functions in other than position space and directly-measured particles differ. However none of those works is the equivalent of the brief "explosions?" letter and its follow-on.
- 1y ago
detourdog 1y ago
I couldn't really make heads or tails of this but if they aren't are emitting are they absorbing instead? I feel like the only way not to emit is to absorb.
- kurthr 1y ago
  Naw, this is Hawking Radiation a "quantum phenomena" that in the original paper doesn't conserve mass/baryons. It's weird that it was originally published (fantastic claims require fantastic evidence). I don't really like the headline of TFA either since it seems conflate all sorts of radiation. The original paper is 2023 (Phys Review Letters). There was a rebuttal in PRL in 2024. I don't know why this is still a big deal now in 2025 other than Science Alert decided to write (another?) hyperbolic article based on crap. Still boring.
cvoss 1y ago
> It would also mean that quantum field theory in curved spacetime can only be consistent if baryon number fails to be conserved! This would be utterly shocking. Is it really shocking (today)? I mean, isn't this a logical consequence of Hawking radiation for black holes? I thought we were shocked by this a long time ago, but now we're ok with it. The authors of the paper in question may very well be wrong in their calculations (I can't say), but this blog post doesn't smell good to me because of doubtful statements like these, passed off as so obviously true that you must be an idiot not to agree. That kind of emotional writing does not become someone whose profession should focus on scientific persuasion. From Wikipedia [0], itself citing Daniel Harlow, a quantum gravity physicist at MIT: > The conservation of baryon number is not consistent with the physics of black hole evaporation via Hawking radiation. [0] https://en.m.wikipedia.org/wiki/Baryon_number https://en.m.wikipedia.org/wiki/Baryon_number
- jiggawatts 1y ago
  > The conservation of baryon number is not consistent with the physics of black hole evaporation via Hawking radiation. There are other black hole models that can conserve these quantum numbers! Speaking of things that are so obviously true that you must be an idiot not to agree, there are statements so obviously false that you have to be an idiot to agree: People keep repeating the nonsense put out by Penrose, which require non-physical timelike infinities to work. The current "pop science" (nearly science fiction) statement is that it is possible to fall into a black hole and there is "nothing special" about the event horizon. Quite often, just one paragraph over, the statement is then made that an external observer will never observe the victim falling in. The two observers can't disagree on such matters! To say otherwise means that you'd have to believe that the Universe splits (when!?) such that there are two observers so that they can disagree. Or stop believing in logic, consistency, observers, and everything we hold dear as physicists. This is all patent nonsense by the same person that keeps insisting that brains are "quantum" despite being 309K and organic. If the external observer doesn't observe the victim falling in, then the victim never falls in, full stop. That's the objective reality. Penrose diagrams say otherwise because they include the time at infinity, which is non-physical. Even if the time at infinity was "reachable", which isn't even mathematically sound, let alone physically, Hawking radiation is a thing, so it doesn't matter anyway: Black holes have finite lifetimes! There is only one logically consistent and physically sound interpretation of black holes: nothing can ever fall in. Inbound victims slow down relative to the outside, which means that from their perspective as they approach the black hole they see its flow of time "speed up". Hence, they also see its Hawking evaporation speed up. To maintain consistency with outside observers, this evaporation must occur fast enough that the victim can never reach any surface. Instead, the black hole recedes from them, evaporating faster and faster. This model (and similar ones), can preserve all quantum numbers, because there is no firewall, no boundary, nothing to "reset" quantum fields. Everything is continuous, consistent, and quantum numbers are preserved. Outside observers see exactly what we currently expect, black holes look and work the same, they evaporate, etc...
zabzonk 1y ago
But they do fade away? (Blondie)
- dudeinjapan 1y ago
  It's better to burn out than to fade away.
quantadev 1y ago
In black holes we have essentially a "loss of a dimension" (it's a much bigger story to explain what that even means, that I won't attempt here), so it might be the case that the three-quark arrangement known as 'baryons' only forms according to number of space dimensions (3D == 3 Quarks), making baryons only happen in 3D, so that when stuff reaches an event horizon, the quarks rip apart and rearrange into something where there's simply no such thing as a baryon (i.e. in 2D space). I'm someone who thinks the 'surface' of an event horizon is where the laws are preserved, and that the singularity or even perhaps the entire interior inside black holes may simply not exist at all. Much of where Relativity "breaks" spacetime (i.e. problems with infinities and divide-by-zero) can be solved by looking at things as a loss of a dimension. For example, length contraction is compressing out a dimension (at light speed), and also time dilation (at event horizons, or light speed) is a removal of a dimension as well. Yes, this is similar to Holographic Principle, if you're noticing that. In my view even Lorentz equation itself is an expression of how you can smoothly transform an N-Dimensional space down to an (N-1)-Dimensional space, which happens on an exponential-like curve where the asymptote is reached right when the dimension is "lost". I think "time" always seems like a special dimension, no matter what dimensionality you're in, because it's the 'next one up' or 'next one down' in this hierarchy of dimensionality in spaces. This is the exact reason 'time' in the Minkowski Space distance formula must be assigned the opposite sign (+/-) from the other dimensions, and holds true regardless of whether you assume time to be positive v.s. negative (i.e. called Metric Signature). This of course implies our entire 4D universe is itself a space embedded in a larger space, and technically it's also an "event horizon" from the perspective of higher dimensions.
- BlueTemplar 1y ago
  > I'm someone who thinks the 'surface' of an event horizon is where the laws are preserved, and that the singularity or even perhaps the entire interior inside black holes may simply not exist at all. Sounds tempting, but then what happens at the transition : when a sphere of matter gets just a little bit too dense ?
  - quantadev 1y ago
    It's just like the Lorentz Tranform or any other of the laws of Relativity. Things can get very massive and/or time can slow way down, but ultimately there's not a "problem" (i.e. mathematical failure requiring the theory to be extended) until the speed of light is reached, as an asymptotic limit. But you're raising a good point that maybe Lorentz is pointing to 'non-integer dimensionality' where even enough mass crammed into a small enough space causes the "new maths" to begin to noticeably take hold. Like I said I see Lorentz as a way to transform dimensionality from N-D to (N +/- 1)D, but in a continuous and 'differentiable' way. In super simplistic terms Lorentz is a "compression" function where one dimension of space is compressed perfectly flat, which is the mathematical equivalent of removing that dimension from the 'degrees of freedom' of the system.
cubefox 1y ago
HN discussion at the time: Universe expected to decay in 10⁷⁸ years, much sooner than previously thought (phys.org) https://news.ycombinator.com/item?id=43961226 https://news.ycombinator.com/item?id=43961226 223 points, 5 days ago, 323 comments
BlueTemplar 1y ago
> As Mark Twain said, “A lie can travel around the world and back again while the truth is lacing up its boots.” Actually he probably didn’t say that—but everyone keeps saying he did, illustrating the point perfectly. It was Gandalf who said that of course. And before you try to contradict me, let me point out that Gandalf is a wizard that has no need to bother with silly things like spacetime continuity. P.S.: https://quoteinvestigator.com/2014/07/13/truth/ https://quoteinvestigator.com/2014/07/13/truth/ > In conclusion, there exists a family of expressions contrasting the dissemination of lies and truths, and these adages have been evolving for more than 300 years. Jonathan Swift can properly be credited with the statement he wrote in 1710 [(that does not mention footwear yet)].
mlhpdx 1y ago
> As Mark Twain said, “A lie can travel around the world and back again while the truth is lacing up its boots.” Actually he probably didn’t say that—but everyone keeps saying he did, illustrating the point perfectly. Well played.
- deepsun 1y ago
  "As Mark Twain famously never said" (c)
- frogulis 1y ago
  In a classic case of the Baader-Meinhof phenomenon, I recently read "The Truth" by Terry Pratchett, which repeatedly makes reference to that phrase, and I am now noticing it everywhere, whereas previously I can't recall being aware of it at all.
  - vlovich123 1y ago
    I remember this from the Stephen Colbert show where he then goes something like “what was the truth doing with its pants off” It’s a very old saying but we all learn it at some point
    - tim333 1y ago
      Quote Investigator was quite interesting on the history. The phrase has been evolving over many years going back to at least 1710. https://quoteinvestigator.com/2014/07/13/truth/ https://quoteinvestigator.com/2014/07/13/truth/
- deleted 1y ago
  [deleted]
thayne 1y ago
The title is... odd. White dwarfs and neutron stars are generally considered "dead stars", since they no longer have active fusion processes. But they do radiate from energy left over from the star's "death". (Mostly thermal energy for a white dwarf, for neutron stars there is also a lot in angular momentum and the spinning magnetic field.) In theory, they will eventually radiate all of their energy away and become black dwarfs or cold neutron stars, but IIRC, that would take longer than the current lifetime of the universe.
- GuB-42 1y ago
  I second that. A more accurate title would be "Only black holes emit Hawking radiation". AFAIK everything above above absolute zero radiates, which effectively means that everything radiates. Black holes would be an exception if it wasn't for Hawking radiation. In addition, (stellar) black holes are dead stars. Or at least, that's one way to see them.
  - tbrownaw 1y ago
    > AFAIK everything above above absolute zero radiates, which effectively means that everything radiates. What really matters is temperature relative to surroundings. Something at the same temperature as everything around it won't lose any net energy to radiation.
    - jfengel 1y ago
      And black holes are much colder then their surroundings, i.e. the Cosmic Microwave Background. And they will be for trillions of years.
      - dr_dshiv 1y ago
        Do you mean singularities are much colder? Because everything outside of that is super hot, no?
        1y ago
layer8 1y ago
This detail caught my eye: > [in their 1975 paper] Ashtekar and Magnon also assume that spacetime is globally hyperbolic Isn’t the modern assumption that spacetime is globally flat?
- senderista 1y ago
  The term refers to causal structure: https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold
- griffzhowl 1y ago
  I'm just learning this stuff so the details are hazy, bu my understanding is that there's a difference between spacetime curvature and spatial curvature. You can have a hyperbolic spacetime while at the same time having a flat three-dimensional spatial section of it. It's not an assumption that space is flat. GR doesn't specify the global space curvature, so it's possible that it has a globally negative or positive curvature, but so far there's no evidence of any.
A_D_E_P_T 1y ago
lol, I wrote a very similar comment here a few days ago: https://news.ycombinator.com/item?id=43964524 https://news.ycombinator.com/item?id=43964524 It's true, that paper is nonsense. There's not really much else to say. Preprint servers sometimes publish the sort of stuff that wouldn't pass peer review. (Remember that S.Korean "superconductor" from about two years ago!?) The press should be cautious when writing about it.
- disentanglement 1y ago
  Although that paper even made it to PRL. I guess I should have written up some similar nonsense and sent it to PRL, might have improved my career chances.
- rubitxxx4 1y ago
  Whether it’s nonsense or not, this quote in the critical assessment is concerning: > If I were a science journalist writing an article about a supposedly shocking development like this, I would email some experts and check to see if it’s for real. An attitude like that would have us all believing the earth is flat or that the sun revolves around the earth. After all, experts of the time believed both wrongly.
  - discoinverno 1y ago
    I agree with that comment. Experts can be wrong, of course, but the null hypothesis is that their opinion is 'more correct' than that of a science journalist. As an aside, nobody really believed the earth was flat: https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth.
    - rubitxxx4 1y ago
      > nobody really believed the earth was flat Your link only debates that during the Middle Ages people thought the earth was flat. Those living in ancient Mesopotamia and Egypt believed we all lived on a flat disc or plane floating in the ocean.
  - 1y ago
khanan 1y ago
Let's see what Neil deGrasse Tyson says about this.
w10-1 1y ago
Ok, we all understand the ancient problem and its current manifestation. But what can be done? Science is not supposed to be the realm of disinformation, but it seems to have no real defenses. People are being paid to lie, no one is being paid to say they are liars, and from the outside scientific dispute looks a lot like politics, so scientists lose credibility by association. That's a real problem.
NKosmatos 1y ago
Ah yes, our favorite HN “entertainment”. Scientists, quantum physicists in our case, having a beef about Hawking radiation :-) Besides some high level ideas, which even us normal people can understand, there are so many details linked in the original post that you need an MSc/PhD to fully understand them. For the time being, let’s just keep that the universe has a few extra trillion years, and isn’t expected to decay in 10⁷⁸ years ;-)
- verzali 1y ago
  A few extra trillion years would look like a drop of water against the ocean that is 10⁷⁸ years...
globnomulous 1y ago
This is partly why I roll my eyes when people who don't do research in a field start telling me about the "studies [they] found" while researching a topic. Unless you know the field and the research methods and have actually practiced them, reading studies is pointless, because you're too ignorant to evaluate them.
JohnMakin 1y ago
Good news for boltzmann brains
- m3kw9 1y ago
  One can argue there are 8billion Boltzmann brains on earth already
m3kw9 1y ago
Anyone that predicts an event that far out in the future let alone 100 years out I would bet against any day of the week. This is couple trillion of trillions years using physics no way of proving
qnleigh 1y ago
Is there a simple way to understand why massive objects don't radiate gravitationally? Accelerating observers see a bath of thermal radiation via something called the Unruh effect. If you're standing on a planet, you're accelerating under gravity, and therefore don't you see Unruh radiation? Does this have any connection to Hawking radiation?
- dataflow 1y ago
  > If you're standing on a planet, you're accelerating under gravity, and therefore don't you see Unruh radiation? Layman here, but if you're standing, you're not actually accelerating, right? You'd only be accelerating if there was nothing under you holding you up, meaning if you were falling down.
  - qnleigh 1y ago
    Ah yeah there are multiple definitions of 'acceleration' here. Unruh radiation occurs when you're not 'in an inertial reference frame,' loosely meaning that you feel acceleration. So in a rocket in space or (presumably) standing on Earth's surface. What you say makes intuitive sense, but it was actually the opposite logic that lead Einstein to his general theory of relativity. Here's a slightly dorky but very good Veritasium video that explains this issue and general relativity https://youtu.be/XRr1kaXKBsU?si=1iudoAx5kWgWHHt- https://youtu.be/XRr1kaXKBsU?si=1iudoAx5kWgWHHt-
    - dataflow 1y ago
      Ah gotcha! Yeah I'm familiar with Einstein's happiest thought - it just escaped me what was meant by acceleration here for the Unruh effect. Cool!
  - nazgul17 1y ago
    Also a layman. But as long as your temperature is not absolute zero, particles inside you are moving, and if they have mass, they would indeed radiate gravitationally - until they slow down to a stop, that being absolute zero. My understanding from pop science videos is that they can indeed evaporate, but only through decay mediated by the weak force.
deepsun 1y ago
Should it be a big embarrassment for Phys. Rev. Lett., a big dip in their reputation? The whole point of respectable journals is that they filter out bad quality papers.
- griffzhowl 1y ago
  Yes, I think so. As Baez says, it suggests the paper wasn't reviewed by experts in the subject. But that is the point of peer review, so seems to be very sloppy work by the journal
- deleted 1y ago
  [deleted]
- verzali 1y ago
  That should be the real issue. Bluntly, science journalism is not that well paid and most people won't have given the articles he calls out more than a moments thought. Of course journalists are going to be lazy if they aren't paid not to be. (Which is a problem itself, but I don't see many people advocating for better paid science journalists). But journals should be a kind of guard rail against that. If their peer reviewers were too lazy to find experts or too arrogant to admit they didn't understand what they were reviewing, then that is a real problem.
tbrownaw 1y ago
I've seen proposed perpetual motion machines based on treating simplified calculations as if they're the real thing.
lproven 1y ago
Of course, as noted researcher Eskil Simonsson teaches, Dead stars still burn.
chrz 1y ago
Theres still something in universe that we are missing and I feel the grand theories of next billion years are missing that

246 points by thechao 1y ago

fishsticks89 1y ago

https://archive.is/mG1KS https://archive.is/mG1KS

Wowfunhappy 1y ago
As best I can tell there's no paywall on TFA, so I really don't think there's any reason to go through archive.is, which adds its own advertisements (if you don't block them).
- Out_of_Characte 1y ago
  archiving isn't just to circumvent a paywall. There's also the HN hug of death, possible geoblocks or an actual interest in archiving the article as it was written at the time these comments.

nimish 1y ago

There's an issue this highlights and it's not that the original authors were stupid so much as there's clearly a lot of knowledge held in silos. That's not a good thing if your goal is to advance everyone's knowledge. Whatever is going on in academia is failing relatively closely related fields which is not good.

kurthr 1y ago
Well, there's another aspect which is that the original authors and pop-sci journalists don't seem to be able to understand where they went wrong or how outrageous their claims are, precisely because their jobs depend on not understanding. The could have corrected it. We could not still be circling this drain 2 years later, but we are. Kinda classic. Kinda boring.
- EA-3167 1y ago
  It helps that this is a genuinely difficult process to understand and requires an enormous fluency with QFT. Most people who fit that bill have better things to do with their time than write popular science articles or correct them.
tekla 1y ago
99.999999999% of people do not have enough knowledge to even dream of beginning to understand a majority of research. Adults can barely read, much less be able to pass Calc 1.
- lupire 1y ago
  Wher are you hiding 92 Billion people?
- coolcase 1y ago
  That percentage of the human population is everyone.
  - saagarjha 1y ago
    I guess they left out a bit for Einstein's brain (but not the rest of his body).
ajross 1y ago
It certainly wasn't in "silos", it's all on arxiv! But yes: the world is complicated and it's easy to make mistakes outside your core field. The point of the scientific process is to get things in front of eyeballs who can spot the mistakes, c.f. the linked blog post. Then everyone fights about it or points and laughs or whatever, and the world moves on. The system worked. What the process is not good at is filtering new ideas before people turn them into news headlines. And sure, that sucks. But it's not a problem with "academia failing", at all. The eyeballs worked!
- deleted 1y ago
  [deleted]
moefh 1y ago
> There's an issue this highlights [...] there's clearly a lot of knowledge held in silos. I think the real issue this highlights -- which is something everyone knows and still everyone does -- is that people love to spread and discuss sensational stories, and no one likes to hear naysayers ruining the fun. Look the discussion of the original story here in HN[1]. There's a comment by A_D_E_P_T way down in the discussion explaining why the paper is nonsense and pointing to one of the replies objecting to it mentioned in the article from this post. That comment was downvoted by HN readers. I know because it was greyed out when I upvoted it days ago. So there's no knowledge silo -- us simple folk just want to discuss the newest breakthrough without looking too hard, because that spoils the fun. [1] https://news.ycombinator.com/item?id=43961226 https://news.ycombinator.com/item?id=43961226
- gnramires 1y ago
  I also think this kind of idea can be fun speculation, but I think there are better things to have fun that aren't promoting wrong ideas (like literal Science Fiction speculation!). When we can build fun on top, the physics of our reality doesn't need to be (academically) fun by itself :)
- ryandrake 1y ago
  I don't think there's a lack of skepticism on HN of all places. Every article that gets posted that discusses even a mild scientific result brings at least one HN commenter out of the woodwork to dunk on it. You can bank on it--there is always That Guy who has to argue against it, whether he's right or not. Also, the comment you reference was probably downvoted because of the tone, not because of some HN bias against naysayers. Starting out your comment with "It's nonsense." is about as conducive to a productive conversation as starting it out with "You're wrong."
  - andrewflnr 1y ago
    The point of a statement like "it's nonsense" is to prevent a conservation that should not happen, because it will be dumb. It's the right thing to say iff it's correct.
  - 1y ago
kmm 1y ago
Is it really that siloed? The condition mentioned in the article (there being a global timelike Killing field) is discussed in all introductory texts on quantum field theory in curved spaces, it's even present in the first few paragraphs of the relevant Wikipedia article[1]. Even if it doesn't apply here, the authors ought to have mentioned why not. I don't think they were stupid per se, nor malicious, but perhaps cavalier in pushing a result with such unexpected consequences without getting a consult. 1: https://en.wikipedia.org/wiki/Quantum_field_theory_in_curved_spacetime https://en.wikipedia.org/wiki/Quantum_field_theory_in_curved...
boznz 1y ago
A Lot of these physics papers are interesting but ultimately just noise. An untested Theory is NOT fact, it's just someone (with or without a PhD) pulling something out of their arse that might explain things. Most of cosmology and physics is still theory (even the big bang, and string theory) and even if 90% of theory fits facts, they could still be wrong. I am seeing more and more of these un-testable theories, built on other un-testable theories, citing other un-testable theories, this is why theoretical physics is in a crisis IMHO. MY mother and father also have an untested theory that explains all this too it's called "God", most Sci-Fi authors have plenty, and I am sure AI's will soon add to this pile. Kudos to those scientists that create testable papers or experimentally prove stuff.
- michaelmrose 1y ago
  We call every model no matter how well founded a theory. An untested theory might be better called a hypothesis. This mistake of language plays into the weirdos who opine we should disregard inconvenient ideas because they are just a theory failing to understand the difference between their own usage and the scientific usage.
grues-dinner 1y ago
> clearly a lot of knowledge held in silos. I don't think it's quite that, since the eventual goal is to publish, not only publicly, but as publicly as possible. More like it seems like everyone tends to hold their cards quite close to their chest until the moment of pre-print publication. Which means you can be working on something that someone could have told you months or years ago you have a problem. The scientific equivalent of polishing a branch before making a pull request, only to be told "this has a huge memory leak and moreover what you want already works if you use this other API". I'm not really sure there's a human-scale solution: the research landscape is so vast that you can't connect everyone to everyone else and have everyone in need of valuable input get it, and have everyone able to give it not be inundated with half-baked rubbish. Even if you assume everyone from the top to bottom has pure motivations and incentives for doing the research in the first place (in the pull request analogy CVE spammers, for example). Perhaps not having the universities themselves so keen for PR that they'll slap a press release together about anything that looks clickable without due diligence would at least prevent making a public spectacle outside of the academic circle now and then, but it wouldn't solve the fundamental issues.
bmitc 1y ago
I think it's just an intractable problem at this point. There's probably millions of physicists on Earth. Everyone working in a company knows just how hard it is to get even hundreds of people to agree and read and understand the same things. The fact is, there are just too many people doing too many things. When any technical paper sounds like gobblygook to even people in the same field but in a different specialty, it's no surprise this happens, especially when coupled with the modern pressure to scientifically publish and modern "journalism" trends.
deleted 1y ago
[deleted]

gruturo 1y ago

Without a gravity well whose escape velocity exceeds c, how are they supposing hawking radiation happens in this scenario? Both virtual particles-antiparticles survive (and promptly disappear because one didn't just cross an event horizon).

Sharlin 1y ago
That one's a big white lie of how Hawking radiation works. It's not even an approximation, just a far-fetched metaphor that Hawking made up, presumably to satisfy science journalists.
- raattgift 1y ago
  Hawking 1974, "Black hole explosions?" (Nature paywall) <https://www.nature.com/articles/248030a0 https://www.nature.com/articles/248030a0> (sci-hub antipaywall) <https://sci-hub.se/https://www.nature.com/articles/248030a0 https://sci-hub.se/https://www.nature.com/articles/248030a0> ("... the time dependence of the metric during the collapse will cause a certain amount of mixing of positive and negative frequencies [...] Part of this wave will be scattered by the curvature of the static Schwarzschild solution outside the black hole ... Another part of the wave will propagate backwards into the star") was certainly not for science journalists and is not at all "far-fetched". The only missing piece here is possibly discussion of his particular approach to second-quantization of the matter fields and how one might interpret that; Hawking's peers fifty years ago did not need assistance there. This was followed in detail by Hawking 1975 (open access via Project Euclid) <https://projecteuclid.org/journals/communications-in-mathematical-physics/volume-43/issue-3/Particle-creation-by-black-holes/cmp/1103899181.full https://projecteuclid.org/journals/communications-in-mathema...> where the most relevant bit surrounds eqns (2.27-28) and there is nothing wrong with talking about signed "contributions to the probability flux into the collapsing body" (as opposed to identifying those contributions as particles). Hawking himself wrote simpler pop-sci explanations in a number of places, including his book, where a reader would not be expected to understand how canonicalizations of wave functions in other than position space and directly-measured particles differ. However none of those works is the equivalent of the brief "explosions?" letter and its follow-on.
1y ago

detourdog 1y ago

I couldn't really make heads or tails of this but if they aren't are emitting are they absorbing instead? I feel like the only way not to emit is to absorb.

kurthr 1y ago
Naw, this is Hawking Radiation a "quantum phenomena" that in the original paper doesn't conserve mass/baryons. It's weird that it was originally published (fantastic claims require fantastic evidence). I don't really like the headline of TFA either since it seems conflate all sorts of radiation. The original paper is 2023 (Phys Review Letters). There was a rebuttal in PRL in 2024. I don't know why this is still a big deal now in 2025 other than Science Alert decided to write (another?) hyperbolic article based on crap. Still boring.

cvoss 1y ago

> It would also mean that quantum field theory in curved spacetime can only be consistent if baryon number fails to be conserved! This would be utterly shocking. Is it really shocking (today)? I mean, isn't this a logical consequence of Hawking radiation for black holes? I thought we were shocked by this a long time ago, but now we're ok with it. The authors of the paper in question may very well be wrong in their calculations (I can't say), but this blog post doesn't smell good to me because of doubtful statements like these, passed off as so obviously true that you must be an idiot not to agree. That kind of emotional writing does not become someone whose profession should focus on scientific persuasion. From Wikipedia [0], itself citing Daniel Harlow, a quantum gravity physicist at MIT: > The conservation of baryon number is not consistent with the physics of black hole evaporation via Hawking radiation. [0] https://en.m.wikipedia.org/wiki/Baryon_number https://en.m.wikipedia.org/wiki/Baryon_number

jiggawatts 1y ago
> The conservation of baryon number is not consistent with the physics of black hole evaporation via Hawking radiation. There are other black hole models that can conserve these quantum numbers! Speaking of things that are so obviously true that you must be an idiot not to agree, there are statements so obviously false that you have to be an idiot to agree: People keep repeating the nonsense put out by Penrose, which require non-physical timelike infinities to work. The current "pop science" (nearly science fiction) statement is that it is possible to fall into a black hole and there is "nothing special" about the event horizon. Quite often, just one paragraph over, the statement is then made that an external observer will never observe the victim falling in. The two observers can't disagree on such matters! To say otherwise means that you'd have to believe that the Universe splits (when!?) such that there are two observers so that they can disagree. Or stop believing in logic, consistency, observers, and everything we hold dear as physicists. This is all patent nonsense by the same person that keeps insisting that brains are "quantum" despite being 309K and organic. If the external observer doesn't observe the victim falling in, then the victim never falls in, full stop. That's the objective reality. Penrose diagrams say otherwise because they include the time at infinity, which is non-physical. Even if the time at infinity was "reachable", which isn't even mathematically sound, let alone physically, Hawking radiation is a thing, so it doesn't matter anyway: Black holes have finite lifetimes! There is only one logically consistent and physically sound interpretation of black holes: nothing can ever fall in. Inbound victims slow down relative to the outside, which means that from their perspective as they approach the black hole they see its flow of time "speed up". Hence, they also see its Hawking evaporation speed up. To maintain consistency with outside observers, this evaporation must occur fast enough that the victim can never reach any surface. Instead, the black hole recedes from them, evaporating faster and faster. This model (and similar ones), can preserve all quantum numbers, because there is no firewall, no boundary, nothing to "reset" quantum fields. Everything is continuous, consistent, and quantum numbers are preserved. Outside observers see exactly what we currently expect, black holes look and work the same, they evaporate, etc...

zabzonk 1y ago

But they do fade away? (Blondie)

dudeinjapan 1y ago
It's better to burn out than to fade away.

quantadev 1y ago

In black holes we have essentially a "loss of a dimension" (it's a much bigger story to explain what that even means, that I won't attempt here), so it might be the case that the three-quark arrangement known as 'baryons' only forms according to number of space dimensions (3D == 3 Quarks), making baryons only happen in 3D, so that when stuff reaches an event horizon, the quarks rip apart and rearrange into something where there's simply no such thing as a baryon (i.e. in 2D space). I'm someone who thinks the 'surface' of an event horizon is where the laws are preserved, and that the singularity or even perhaps the entire interior inside black holes may simply not exist at all. Much of where Relativity "breaks" spacetime (i.e. problems with infinities and divide-by-zero) can be solved by looking at things as a loss of a dimension. For example, length contraction is compressing out a dimension (at light speed), and also time dilation (at event horizons, or light speed) is a removal of a dimension as well. Yes, this is similar to Holographic Principle, if you're noticing that. In my view even Lorentz equation itself is an expression of how you can smoothly transform an N-Dimensional space down to an (N-1)-Dimensional space, which happens on an exponential-like curve where the asymptote is reached right when the dimension is "lost". I think "time" always seems like a special dimension, no matter what dimensionality you're in, because it's the 'next one up' or 'next one down' in this hierarchy of dimensionality in spaces. This is the exact reason 'time' in the Minkowski Space distance formula must be assigned the opposite sign (+/-) from the other dimensions, and holds true regardless of whether you assume time to be positive v.s. negative (i.e. called Metric Signature). This of course implies our entire 4D universe is itself a space embedded in a larger space, and technically it's also an "event horizon" from the perspective of higher dimensions.

BlueTemplar 1y ago
> I'm someone who thinks the 'surface' of an event horizon is where the laws are preserved, and that the singularity or even perhaps the entire interior inside black holes may simply not exist at all. Sounds tempting, but then what happens at the transition : when a sphere of matter gets just a little bit too dense ?
- quantadev 1y ago
  It's just like the Lorentz Tranform or any other of the laws of Relativity. Things can get very massive and/or time can slow way down, but ultimately there's not a "problem" (i.e. mathematical failure requiring the theory to be extended) until the speed of light is reached, as an asymptotic limit. But you're raising a good point that maybe Lorentz is pointing to 'non-integer dimensionality' where even enough mass crammed into a small enough space causes the "new maths" to begin to noticeably take hold. Like I said I see Lorentz as a way to transform dimensionality from N-D to (N +/- 1)D, but in a continuous and 'differentiable' way. In super simplistic terms Lorentz is a "compression" function where one dimension of space is compressed perfectly flat, which is the mathematical equivalent of removing that dimension from the 'degrees of freedom' of the system.

cubefox 1y ago

HN discussion at the time: Universe expected to decay in 10⁷⁸ years, much sooner than previously thought (phys.org) https://news.ycombinator.com/item?id=43961226 https://news.ycombinator.com/item?id=43961226 223 points, 5 days ago, 323 comments

BlueTemplar 1y ago

> As Mark Twain said, “A lie can travel around the world and back again while the truth is lacing up its boots.” Actually he probably didn’t say that—but everyone keeps saying he did, illustrating the point perfectly. It was Gandalf who said that of course. And before you try to contradict me, let me point out that Gandalf is a wizard that has no need to bother with silly things like spacetime continuity. P.S.: https://quoteinvestigator.com/2014/07/13/truth/ https://quoteinvestigator.com/2014/07/13/truth/ > In conclusion, there exists a family of expressions contrasting the dissemination of lies and truths, and these adages have been evolving for more than 300 years. Jonathan Swift can properly be credited with the statement he wrote in 1710 [(that does not mention footwear yet)].

mlhpdx 1y ago

deepsun 1y ago
"As Mark Twain famously never said" (c)
frogulis 1y ago
In a classic case of the Baader-Meinhof phenomenon, I recently read "The Truth" by Terry Pratchett, which repeatedly makes reference to that phrase, and I am now noticing it everywhere, whereas previously I can't recall being aware of it at all.
- vlovich123 1y ago
  I remember this from the Stephen Colbert show where he then goes something like “what was the truth doing with its pants off” It’s a very old saying but we all learn it at some point
  - tim333 1y ago
    Quote Investigator was quite interesting on the history. The phrase has been evolving over many years going back to at least 1710. https://quoteinvestigator.com/2014/07/13/truth/ https://quoteinvestigator.com/2014/07/13/truth/
deleted 1y ago
[deleted]

thayne 1y ago

The title is... odd. White dwarfs and neutron stars are generally considered "dead stars", since they no longer have active fusion processes. But they do radiate from energy left over from the star's "death". (Mostly thermal energy for a white dwarf, for neutron stars there is also a lot in angular momentum and the spinning magnetic field.) In theory, they will eventually radiate all of their energy away and become black dwarfs or cold neutron stars, but IIRC, that would take longer than the current lifetime of the universe.

GuB-42 1y ago
I second that. A more accurate title would be "Only black holes emit Hawking radiation". AFAIK everything above above absolute zero radiates, which effectively means that everything radiates. Black holes would be an exception if it wasn't for Hawking radiation. In addition, (stellar) black holes are dead stars. Or at least, that's one way to see them.
- tbrownaw 1y ago
  > AFAIK everything above above absolute zero radiates, which effectively means that everything radiates. What really matters is temperature relative to surroundings. Something at the same temperature as everything around it won't lose any net energy to radiation.
  - jfengel 1y ago
    And black holes are much colder then their surroundings, i.e. the Cosmic Microwave Background. And they will be for trillions of years.
    - dr_dshiv 1y ago
      Do you mean singularities are much colder? Because everything outside of that is super hot, no?
      - 1y ago

layer8 1y ago

This detail caught my eye: > [in their 1975 paper] Ashtekar and Magnon also assume that spacetime is globally hyperbolic Isn’t the modern assumption that spacetime is globally flat?

senderista 1y ago
The term refers to causal structure: https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold https://en.wikipedia.org/wiki/Globally_hyperbolic_manifold
griffzhowl 1y ago
I'm just learning this stuff so the details are hazy, bu my understanding is that there's a difference between spacetime curvature and spatial curvature. You can have a hyperbolic spacetime while at the same time having a flat three-dimensional spatial section of it. It's not an assumption that space is flat. GR doesn't specify the global space curvature, so it's possible that it has a globally negative or positive curvature, but so far there's no evidence of any.

A_D_E_P_T 1y ago

lol, I wrote a very similar comment here a few days ago: https://news.ycombinator.com/item?id=43964524 https://news.ycombinator.com/item?id=43964524 It's true, that paper is nonsense. There's not really much else to say. Preprint servers sometimes publish the sort of stuff that wouldn't pass peer review. (Remember that S.Korean "superconductor" from about two years ago!?) The press should be cautious when writing about it.

disentanglement 1y ago
Although that paper even made it to PRL. I guess I should have written up some similar nonsense and sent it to PRL, might have improved my career chances.
rubitxxx4 1y ago
Whether it’s nonsense or not, this quote in the critical assessment is concerning: > If I were a science journalist writing an article about a supposedly shocking development like this, I would email some experts and check to see if it’s for real. An attitude like that would have us all believing the earth is flat or that the sun revolves around the earth. After all, experts of the time believed both wrongly.
- discoinverno 1y ago
  I agree with that comment. Experts can be wrong, of course, but the null hypothesis is that their opinion is 'more correct' than that of a science journalist. As an aside, nobody really believed the earth was flat: https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth.
  - rubitxxx4 1y ago
    > nobody really believed the earth was flat Your link only debates that during the Middle Ages people thought the earth was flat. Those living in ancient Mesopotamia and Egypt believed we all lived on a flat disc or plane floating in the ocean.
- 1y ago

khanan 1y ago

Let's see what Neil deGrasse Tyson says about this.

w10-1 1y ago

Ok, we all understand the ancient problem and its current manifestation. But what can be done? Science is not supposed to be the realm of disinformation, but it seems to have no real defenses. People are being paid to lie, no one is being paid to say they are liars, and from the outside scientific dispute looks a lot like politics, so scientists lose credibility by association. That's a real problem.

NKosmatos 1y ago

Ah yes, our favorite HN “entertainment”. Scientists, quantum physicists in our case, having a beef about Hawking radiation :-) Besides some high level ideas, which even us normal people can understand, there are so many details linked in the original post that you need an MSc/PhD to fully understand them. For the time being, let’s just keep that the universe has a few extra trillion years, and isn’t expected to decay in 10⁷⁸ years ;-)

verzali 1y ago
A few extra trillion years would look like a drop of water against the ocean that is 10⁷⁸ years...

globnomulous 1y ago

This is partly why I roll my eyes when people who don't do research in a field start telling me about the "studies [they] found" while researching a topic. Unless you know the field and the research methods and have actually practiced them, reading studies is pointless, because you're too ignorant to evaluate them.

JohnMakin 1y ago

Good news for boltzmann brains

m3kw9 1y ago
One can argue there are 8billion Boltzmann brains on earth already

m3kw9 1y ago

Anyone that predicts an event that far out in the future let alone 100 years out I would bet against any day of the week. This is couple trillion of trillions years using physics no way of proving

qnleigh 1y ago

Is there a simple way to understand why massive objects don't radiate gravitationally? Accelerating observers see a bath of thermal radiation via something called the Unruh effect. If you're standing on a planet, you're accelerating under gravity, and therefore don't you see Unruh radiation? Does this have any connection to Hawking radiation?

dataflow 1y ago
> If you're standing on a planet, you're accelerating under gravity, and therefore don't you see Unruh radiation? Layman here, but if you're standing, you're not actually accelerating, right? You'd only be accelerating if there was nothing under you holding you up, meaning if you were falling down.
- qnleigh 1y ago
  Ah yeah there are multiple definitions of 'acceleration' here. Unruh radiation occurs when you're not 'in an inertial reference frame,' loosely meaning that you feel acceleration. So in a rocket in space or (presumably) standing on Earth's surface. What you say makes intuitive sense, but it was actually the opposite logic that lead Einstein to his general theory of relativity. Here's a slightly dorky but very good Veritasium video that explains this issue and general relativity https://youtu.be/XRr1kaXKBsU?si=1iudoAx5kWgWHHt- https://youtu.be/XRr1kaXKBsU?si=1iudoAx5kWgWHHt-
  - dataflow 1y ago
    Ah gotcha! Yeah I'm familiar with Einstein's happiest thought - it just escaped me what was meant by acceleration here for the Unruh effect. Cool!
- nazgul17 1y ago
  Also a layman. But as long as your temperature is not absolute zero, particles inside you are moving, and if they have mass, they would indeed radiate gravitationally - until they slow down to a stop, that being absolute zero. My understanding from pop science videos is that they can indeed evaporate, but only through decay mediated by the weak force.

deepsun 1y ago

Should it be a big embarrassment for Phys. Rev. Lett., a big dip in their reputation? The whole point of respectable journals is that they filter out bad quality papers.

griffzhowl 1y ago
Yes, I think so. As Baez says, it suggests the paper wasn't reviewed by experts in the subject. But that is the point of peer review, so seems to be very sloppy work by the journal
deleted 1y ago
[deleted]
verzali 1y ago
That should be the real issue. Bluntly, science journalism is not that well paid and most people won't have given the articles he calls out more than a moments thought. Of course journalists are going to be lazy if they aren't paid not to be. (Which is a problem itself, but I don't see many people advocating for better paid science journalists). But journals should be a kind of guard rail against that. If their peer reviewers were too lazy to find experts or too arrogant to admit they didn't understand what they were reviewing, then that is a real problem.

tbrownaw 1y ago

I've seen proposed perpetual motion machines based on treating simplified calculations as if they're the real thing.

lproven 1y ago

Of course, as noted researcher Eskil Simonsson teaches, Dead stars still burn.

chrz 1y ago

Theres still something in universe that we are missing and I feel the grand theories of next billion years are missing that