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Disclaimer: we are at the hairy edge of my knowledge here, so what I am about to tell you could very well be wrong. Hawking radiation has never actually been o

by lisper 5y ago

Disclaimer: we are at the hairy edge of my knowledge here, so what I am about to tell you could very well be wrong. Hawking radiation has never actually been observed. It is just something that pops out of the math if, as Sabine rightfully emphasizes in her video, you make certain assumptions. And one of those assumptions is that you have a fully-fledged black hole, i.e. an object that actually contains mass beyond the event horizon. We are used to thinking of this assumption as having actually been confirmed by observation, but it is not actually true. No one has ever actually observed a black hole, notwithstanding that we've ostensibly taken a picture of one. That image was of the radiation emitted by an accretion disk, not the black hole itself. Black holes themselves are, obviously, impossible to image. So we don't actually know whether black holes actually exist or not. The only thing we've directly observed is their gravitational effects, and the gravitational effects of an actual black hole are indistinguishable from having all of the mass of the hole actually resident just outside the event horizon. What actually happens at the horizon is beyond the reach of our current theories because there both gravity and quantum effects are significant, and we do not yet have a consistent theory of quantum gravity. Everything we think we know about black holes is actually the result of taking GR and QM and framming them together in some ad hoc way by adding simplifying assumptions which may or may not actually be true. This is the point Sabine was trying to make: the black hole information loss paradox is not a problem with physics, it's a problem with our current theories. We simply don't know how the universe actually behaves in the presence of extreme concentrations of mass/energy. The only thing that the BHILP actually tells us is that either GR or QM -- or both -- are wrong, mere approximations to the actual truth in the same way that Newtonian mechanics turned out to be an approximation to the actual truth (one that happens to work extremely well in weak gravitational fields). But no one has a clue which one is wrong or how despite 100 years of effort. And one of the reasons for this is that we have no data, and no reasonable prospects for obtaining it. So we may just have to make our peace with not knowing.

platz 5y ago
Wall of text, didn't answer the question.
- lisper 5y ago
  The question assumes that black holes evaporate, and we don't actually know that they do. Is that better?
  - platz 5y ago
    That is a more transparent answer and direct answer, yes. Maybe if you had lead with that sentence, I wouldn't have been inclined to respond. But it also fails to address what I point out below. (as an aside, this answer is also not one that I find satisfactory on the actual topic.) Dllthomas correctly pointed out that given the two premises that (from the frame of the observer) (1) [matter takes infinite time to transit the horizon] and (2) [due to hawking radiation, black holes have a finite time span], then (2) resolves (1) when the black hole disappears. To recap, Instead of acknowledging that (2) resolves (1) you proceed to question the existence of hawking radiation and black hole evaporation, which compared to consensus is a radical view and is not warranted. Also the pivot was done in a way that seems to complicate and obfuscate rather than address the point directly (this is a common debate tactic; however I'm not sure if you were conscious of the behavior or if it was more subconscious/rationalization (more likely); you may not have even been aware you were doing it). It seems like you chose to reject consensus instead of simply accepting that (2) resolves (1), maybe because you seem to have a fixation on not ever conceding a point in a conversation. Sometimes it's ok just so say, "yeah, that's a good point". (btw if you're rejecting hawking radiation why say anything about black hole theory at all this point because it could all be wrong, no reason to speculate about it)
    - lisper 5y ago
      > you seem to have a fixation on not ever conceding a point That is quite the accusation coming from someone whose entry into the conversation was "Wall of text, didn't answer the question." But let's see... > Dllthomas correctly pointed out... dllthomas did not "point out" anything, correctly or otherwise. All he did was ask the following question: "How does that remain true after the black hole has evaporated and there is no longer a horizon?" This question assumes that black holes evaporate. That assumption may be incorrect. We do not know whether or not black holes actually evaporate. In fact, we do not even know whether or not black holes actually form at all. And therefore: > (2) resolves (1) when the black hole disappears That might be true if (2) were true. Even that is arguable, but it is neither here nor there because we do not know whether or not (2) is true > compared to consensus is a radical view Yes, of course. The consensus view leads to a paradox, and so we know that the consensus view cannot possibly be correct. We also know that decades of effort have not resolved this paradox, and so it is extremely unlikely that there is a simple straightforward solution that has simply been overlooked. So the correct solution will almost certainly be a radical departure from the current consensus.
polishdude20 5y ago
It's fascinating to think that our theories on everything around us are based on everything near us enough to be measurable and experimented on. Black holes are so far away and so outside of our normal observations of mass and energy that we can't observe them well enough to do experiments. It's like we've come up with two theories of how the universe works but and the universe is like "you guys are like 90% there but here's a case where these don't work.". It's fascinating to think that there's gotta be some one theory that can account for everything in the universe both big and small from black holes to quantum stuff. It's like we've dug ourselves in two very deep holes over the years and maybe we need someone to come along with a new hole that encompasses both things that see the whole picture. Anyways now I'm just speculating.
- lisper 5y ago
  > there's gotta be some one theory that can account for everything Actually, there doesn't. The universe is under no obligation to operate according to laws. That the behavior of the universe is so lawful is quite remarkable. It didn't have to be this way. Our universe could be a simulation, and that simulation could have been created by some capricious being who makes all kinds of random shit happen just to fuck with us. That does not appear to be the case, but there is no reason that it could not have been. Likewise, there is no reason why our brains should have the capacity to be able to figure this out. It may be that the Kolmogorov complexity of the universe is vastly larger than what the human brain is capable of dealing with. Again, this does not appear to be the case. In fact, it appears to be the exact opposite. We can explain 100% of the phenomena within our solar system, and even within most of our galaxy, with theories whose KC is shockingly low, small enough to be grasped by a single human brain. But it didn't have to be that way. And maybe it isn't that way. Maybe we have actually reached the limit of what the human brain is capable of (in terms of figuring out physics). I don't think so, but you can't rule out the possibility on the basis of the evidence we have.
  - polishdude20 5y ago
    I'm just saying there's gotta be because of what we've observed so far. Like you said, we can explain 100% of the phenomena in our solar system. It leads to believe that we can do that in the future for things outside of it. Also, just because a theory is discontinuous at its boundaries doesn't mean we can't have a theory that is on the other edge of that boundary. The unifying theory is supposedly supposed to link both general relativity and quantum mechanics. Obviously this is just my opinion but I think any system that is sufficiently observable, with enough time can be figured out completely. I don't think it's a matter of if our brains can understand it but if we can have the ability to run experiments on it and enough time.
wumpus 5y ago
> Black holes themselves are, obviously, impossible to image. What we observe is the "shadow" of the black hole. The expectation is that the flux from the shadow should be consistent with zero. For M87* the observed flux ratio with the ring was ~10:1. See Paper 1: First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole https://arxiv.org/abs/1906.11238 https://arxiv.org/abs/1906.11238
vl 5y ago
>Black holes themselves are, obviously, impossible to image. Unless they produce Hawking radiation. Then by definition they are possible to image. In the original article she mentions that temperature of known black holes is lower than CBR, meaning that they are too cold to be seen agains background of cosmic background radiation. I personally think that they produce no radiation and do not evaporate, but this is just unscientific philosophical opinion.
- lisper 5y ago
  > Unless they produce Hawking radiation. Fair point (modulo the practical difficulties of measuring Hawking radiation).

by lisper 5y ago

platz 5y ago

Wall of text, didn't answer the question.

lisper 5y ago
The question assumes that black holes evaporate, and we don't actually know that they do. Is that better?
- platz 5y ago
  That is a more transparent answer and direct answer, yes. Maybe if you had lead with that sentence, I wouldn't have been inclined to respond. But it also fails to address what I point out below. (as an aside, this answer is also not one that I find satisfactory on the actual topic.) Dllthomas correctly pointed out that given the two premises that (from the frame of the observer) (1) [matter takes infinite time to transit the horizon] and (2) [due to hawking radiation, black holes have a finite time span], then (2) resolves (1) when the black hole disappears. To recap, Instead of acknowledging that (2) resolves (1) you proceed to question the existence of hawking radiation and black hole evaporation, which compared to consensus is a radical view and is not warranted. Also the pivot was done in a way that seems to complicate and obfuscate rather than address the point directly (this is a common debate tactic; however I'm not sure if you were conscious of the behavior or if it was more subconscious/rationalization (more likely); you may not have even been aware you were doing it). It seems like you chose to reject consensus instead of simply accepting that (2) resolves (1), maybe because you seem to have a fixation on not ever conceding a point in a conversation. Sometimes it's ok just so say, "yeah, that's a good point". (btw if you're rejecting hawking radiation why say anything about black hole theory at all this point because it could all be wrong, no reason to speculate about it)
  - lisper 5y ago
    > you seem to have a fixation on not ever conceding a point That is quite the accusation coming from someone whose entry into the conversation was "Wall of text, didn't answer the question." But let's see... > Dllthomas correctly pointed out... dllthomas did not "point out" anything, correctly or otherwise. All he did was ask the following question: "How does that remain true after the black hole has evaporated and there is no longer a horizon?" This question assumes that black holes evaporate. That assumption may be incorrect. We do not know whether or not black holes actually evaporate. In fact, we do not even know whether or not black holes actually form at all. And therefore: > (2) resolves (1) when the black hole disappears That might be true if (2) were true. Even that is arguable, but it is neither here nor there because we do not know whether or not (2) is true > compared to consensus is a radical view Yes, of course. The consensus view leads to a paradox, and so we know that the consensus view cannot possibly be correct. We also know that decades of effort have not resolved this paradox, and so it is extremely unlikely that there is a simple straightforward solution that has simply been overlooked. So the correct solution will almost certainly be a radical departure from the current consensus.

polishdude20 5y ago

It's fascinating to think that our theories on everything around us are based on everything near us enough to be measurable and experimented on. Black holes are so far away and so outside of our normal observations of mass and energy that we can't observe them well enough to do experiments. It's like we've come up with two theories of how the universe works but and the universe is like "you guys are like 90% there but here's a case where these don't work.". It's fascinating to think that there's gotta be some one theory that can account for everything in the universe both big and small from black holes to quantum stuff. It's like we've dug ourselves in two very deep holes over the years and maybe we need someone to come along with a new hole that encompasses both things that see the whole picture. Anyways now I'm just speculating.

lisper 5y ago
> there's gotta be some one theory that can account for everything Actually, there doesn't. The universe is under no obligation to operate according to laws. That the behavior of the universe is so lawful is quite remarkable. It didn't have to be this way. Our universe could be a simulation, and that simulation could have been created by some capricious being who makes all kinds of random shit happen just to fuck with us. That does not appear to be the case, but there is no reason that it could not have been. Likewise, there is no reason why our brains should have the capacity to be able to figure this out. It may be that the Kolmogorov complexity of the universe is vastly larger than what the human brain is capable of dealing with. Again, this does not appear to be the case. In fact, it appears to be the exact opposite. We can explain 100% of the phenomena within our solar system, and even within most of our galaxy, with theories whose KC is shockingly low, small enough to be grasped by a single human brain. But it didn't have to be that way. And maybe it isn't that way. Maybe we have actually reached the limit of what the human brain is capable of (in terms of figuring out physics). I don't think so, but you can't rule out the possibility on the basis of the evidence we have.
- polishdude20 5y ago
  I'm just saying there's gotta be because of what we've observed so far. Like you said, we can explain 100% of the phenomena in our solar system. It leads to believe that we can do that in the future for things outside of it. Also, just because a theory is discontinuous at its boundaries doesn't mean we can't have a theory that is on the other edge of that boundary. The unifying theory is supposedly supposed to link both general relativity and quantum mechanics. Obviously this is just my opinion but I think any system that is sufficiently observable, with enough time can be figured out completely. I don't think it's a matter of if our brains can understand it but if we can have the ability to run experiments on it and enough time.

wumpus 5y ago

> Black holes themselves are, obviously, impossible to image. What we observe is the "shadow" of the black hole. The expectation is that the flux from the shadow should be consistent with zero. For M87* the observed flux ratio with the ring was ~10:1. See Paper 1: First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole https://arxiv.org/abs/1906.11238 https://arxiv.org/abs/1906.11238

vl 5y ago

>Black holes themselves are, obviously, impossible to image. Unless they produce Hawking radiation. Then by definition they are possible to image. In the original article she mentions that temperature of known black holes is lower than CBR, meaning that they are too cold to be seen agains background of cosmic background radiation. I personally think that they produce no radiation and do not evaporate, but this is just unscientific philosophical opinion.

lisper 5y ago
> Unless they produce Hawking radiation. Fair point (modulo the practical difficulties of measuring Hawking radiation).