“My discovery that black holes emit radiation raised serious problems of consistency with the rest of physics. I have now resolved these problems, but the answer turned out to be not what I expected.” -Stephen Hawking

One of the most puzzling things about Black Holes is that if you wait around long enough, they’ll evaporate completely. The curved spacetime outside of the event horizon still undergoes quantum effects, and when you combine General Relativity and quantum field theory in exactly that fashion, you get a blackbody spectrum of thermal radiation out.

Hawking radiation is what inevitably results from the predictions of quantum physics in the curved spacetime surrounding a black hole’s event horizon. Image credit: E. Siegel.

Given enough time, a black hole will decay away completely. But what will that entail? Will an event horizon cease to exist, exposing a former black hole’s core? Will it persist right until the final moment, indicative of a true singularity? And how hot and energetic will that final evaporative state be?

Against a seemingly eternal backdrop of everlasting darkness, a single flash of light will emerge: the evaporation of the final black hole in the Universe. Image credit: ortega-pictures / Pixabay.

Incredibly, even without a quantum theory of gravity, we can predict the answers! Find out on this week’s Ask Ethan.

Comments

  1. #1 Kasim Muflahi
    United Kingdom
    May 20, 2017

    I thought that the event horizon is determined by the mass of the blackhole. To me, this means that the event horizon radius will get smaller and smaller as the mass decreases. The escape velocity will also decrease until it reaches sublight speeds; at which point a neutron star becomes visible.
    You’re implying that as soon as an event horizon develops, the volume of the blackhole becomes zero i.e. a singularity irrespective of what the mass is.
    I disagree. I think that at the centre of every blackhole is a neutron star and it’s only the humongous gravity that prevents us from seeing it. Besides, as the blackhole loses mass, it also loses gravity. So, the remaining mass expands in volume since it’s being compressed by a weaker and weaker gravitational force.
    People quote that GR predicts a singularity. Every equation has a domain of validity and these people are using GR beyond its domain of validity (which has yet to be determined). For example, the stoichiometric laws of chemistry state that inert gases cannot form compounds; and yet Xenon does. This is explained by the fact that the electrons of the outer shell are very loosely held due to the distance from the nucleus and the shielding effect of the inner shells. This enables high electronegativity elements, such as oxygen and fluorine, to pull those outer electrons and form legitimate bonds. This illustrates that the law of stoichiometry has its limitations i.e. it’s domain of validity.
    So, as far as I’m concerned, a blackhole has a massive neutron star at the centre that causes an event horizon to form at a particular distance from the centre of the neutron star i.e. there’s no singularity as it’s a physical impossibilty because you can’t have any amount of mass in a point of zero volume.

    The fact that GR predicts singularities implies that it’s being used outside of its domain of validity which has yet to be determined.

  2. #2 Frank
    Omaha,NE
    May 20, 2017

    Hawking radiation carries away energy and information and both are conserved. If the energy comes from the Black Hole then information must come from it also. This maybe a two stage process where the Black Hole gives energy and information to vacuum and vacuum gives them to Hawking Radiation.

  3. #3 John
    Baltimore
    May 20, 2017

    As the Hawking Radiation originates from outside of the Balk Hole, it is not obvious to me how it could carry information from the other side of the Event Horizon. Additionally, as the Hawking Radiation is one of a pair of virtual particles – photons – coming into existence randomly, with the other of the pair falling through the Event Horizon. It is unclear to me what information about the Black Hole it, the one “emanating” from the Black Hole, could provide.

  4. #4 Michael Mooney
    May 20, 2017

    So the Forbes “Ask Ethan” blog is different than this forum. Got it. My comments on the same topic there will not show up here
    .
    Why two different conversations on the same blog? Just asking.

  5. #5 John
    Baltimore
    May 20, 2017

    Michael,

    I believe that the synopsis here drives traffic to there.

    John

  6. #6 Michael Mooney
    May 20, 2017

    Ps: I once read a very astute answer to a physics question on a Q&A site:
    “Where does Hawking radiation go?”
    Answer from the professor:
    “Nowhere. It stays in Hawking’s head!”

  7. #7 Frank
    Omaha,NE
    May 20, 2017

    John,
    That was my reasoning for the solution of Black Hole Information Paradox. No idea how actually it could happen but I think that is the correct way. Based on that reasoning I also think No Hair Theorem (which leads to the paradox and also seems unproven) must be wrong somehow.

  8. #8 Elle H.C.
    May 20, 2017

    @John

    If I’m not mistaken than Ethan had first his own blog-site, than he moved to here (scienceblogs), after sometime he also got invited to Medium, and next also Forbes. So it’s more like a tv-show that’s played on multiple channels. Anyway, there’s an existing readers community here so he keeps this one ‘alive’ as well. There some swab-post were he explains it all.

  9. #9 anneb
    Amsterdam
    May 21, 2017

    #1, @Kasim Muflahi. Neutrons resist collapse until a certain pressure. I suppose this pressure limit can be calculated? After this the neurtron star transforms into a quark star, a single object consisting of quarks. If the pressure gets even higher, the quark star collapses into something even smaller, supposedly a point-like singularity.

    However, if the black hole looses mass due to radiation and the black hole mass reduces to less than that of a quark star, why would the singularity remain stable and not pop back into such a quark star?

  10. #10 Johnny
    May 21, 2017

    For objects other than a black hole, the escape velocity is the minimum speed a projectile would need to get to “infinity”.
    However this assumes the projectile gets a ״kick” and then no additional force (except gravity) is involved. If you have a rocket you can supply the required energy gradually and you do not have to get to escape velocity.
    This is not the case for black holes but it’s not simply because nothing can go faster than. Light

  11. #11 Johnny
    May 21, 2017

    Singularities: this is what we get from taking the physics we know to its conclusion.
    Every time a theory gave us “infinity” in the past – we had to modify the theory.

  12. #12 John
    Baltimore
    May 21, 2017

    Elle,

    When I compare the content of the synopsis here to that in the the article at Forbes I see different content. The TV shows are not the same.

    John

  13. #13 Michael Mooney
    May 21, 2017

    John,
    It seems like a lot of razzel-dazzel to me… as an old man who is not very good at navigating a maze for the sake of one conversation on one topic. Pick your “channel” for the daily wisdom from Dr. Siegel. Who knows who reads your comments on the same conversation.

    I recommend a competent administrator without an opinion on any issue. I would probably be banned again if s/he were a “mainstream relativity” believer. No worry here. Nonsense is not science… in the long run.

  14. #14 Anonymous Coward
    May 22, 2017

    I don’t think it would just be one spectacular flash of light. Once black holes got sufficiently small they’d be emitting lots of radiation. If we had a black hole which had shrunk down to around a hundred billion kilograms or so, that would last for around the age of the universe to date. I wonder if you had a cluster of these, gravitationally bound in stable orbits, in the very late universe, if it could manage to produce enough energy to develop life on a planet of some sort in orbit around it. It would take something like 1060 years for a solar mass black hole to shrink to that size though, and if proton decay happens, with a half-life of about 1036 years, there would be precious little ordinary matter left by that time.

  15. #15 Elle H.C.
    May 22, 2017

    @John,

    Indeed the posts are not ‘exactly’ the same, the posts on this blog have turned into shorter introductory posts with each time a link to the full (Forbes) article at the bottom. You can check the older posts to see the difference.

  16. #16 Michael Mooney
    May 22, 2017

    Where to comment… Here or there?
    There must be an explanation to reconcile two apparently contradictory claims about black holes.
    The first is of course is the standard description as a mass generating so much gravity that NOTHING can escape.
    The second is Hawking’s brain child, the “evaporation” of black holes via “Hawking radiation.”

    Here is the essence of the latter according to Ethan:

    “Combining these two laws of nature — quantum physics and the General Relativistic spacetime around a black hole — gives us the phenomenon of Hawking radiation.”

    (Illustration):” A visualization of QCD illustrates how particle/antiparticle pairs pop out of the quantum”

    ” One of the most puzzling things about Black Holes is that if you wait around long enough, they’ll evaporate.”

    First, quantum physics and general relativistic spacetime are “LAWS OF NATURE?” Really… not just speculative theories?
    Second, the illustration “shows” particle pairs “popping out,” so there is the “evidence” right before our eyes! (?)
    Third, if neither light nor mass can escape a bh gravity well, how is it that these theoretical particle/ antiparticle pairs can “pop out?”
    I know that Ethan has declined to reply to me here anymore since he dodged (ignored) explaining his self contradiction on another topic, but maybe someone else here who believes in Hawking radiation can shed some light on the above contradiction.

  17. #17 Sean T
    May 22, 2017

    MM,

    No contradiction, just (once again) a misunderstanding of the physics on your part. General Relativity states that nothing, including light, can exit a black hole. That’s true, but only insofar as Quantum Mechanics is ignored. The two theories have to date not been reconciled successfully. For the most part, this is not a problem as their domains are widely different. GR deals with gravity, which is really only important at cosmological scales. QM only really diverges from classical physics for very tiny objects like atoms, molecules and subatomic particles. There very rarely is any reason to be concerned that the two theories are basically incompatible.

    Very rarely is not never, though. Black holes present a case where the BH singularity both is very massive (meaning GR is needed) and very tiny (meaning QM is needed). Since we need both simultaneously and we know we cannot reconcile them, what we get out of the combination is somewhat speculative. We have not observed Hawking Radiation (AFAIK, someone please correct me if I’m wrong) to date. It is in the realm of speculation. However, the rule that nothing can escape a BH is solely based on GR. When we have a situation where QM effects are relevant, the conclusions of GR may have to be modified.

    This does NOT mean what you probably want it to mean, though. This does not throw GR into disrepute in any way. It is merely a recognition that GR (like all scientific theories) is limited in its domain of usefulness. Venturing outside that domain can lead to incorrect predictions from the theory. That does not mean that the predictions within its domain are in any way incorrect or suspect. For GR at least, these predictions have in fact been experimentally verified 100% of the time they have been tested. GR is a very strong, but incomplete, theory. Nobody has ever suggested otherwise.

    And, BTW, another misunderstanding you seem to have. Laws of nature are in no way superior to theories in science. They are in fact different entities altogether. In terms of understanding of the universe, in fact, we prefer theories to laws of nature. Laws of nature are merely an expression of some regularity of the universe. For example “Two masses will attract each other with a force proportional to their masses and inversely proportional to the square of their separation distance” is a law of nature. This expresses a universal regularity. We expect that if we actually measure the force between two objects that we can correctly predict the value we measure from this law.

    This is an important step, but there’s something missing from this law (and every other law), which is WHY it holds true. That’s where theories come in. Theories are the explanation of laws. GR is the theory that explains WHY the previously quoted law is true. Theories are NOT speculative. The statements that are speculative are called hypotheses, and are also important components of science. These are statements that are tested in order to develop theories. A theory is an overarching framework that leads to many hypotheses that can be tested. In the case of GR, these included the motion of the planet Mercury, the apparent shift in stellar positions during a solar eclipse, time dilation, length contraction, and a whole host of other hypotheses. These have all been tested and found to agree with the theory, so we hold that the theory is true. New evidence could show otherwise, but right now GR is the best theory of gravity that we have.

  18. #18 Michael Mooney
    May 22, 2017

    Sean T,
    “cir·cum·lo·cu·tion:
    noun
    the use of many words where fewer would do, especially in a deliberate attempt to be vague or evasive.”

    So back to my question: If nothing escapes the gravity of a black hole, how can they possibly “evaporate” … as when “twin virtual particles” are said to “pop out,” AS ILLUSTRATED?

    Very imaginative, with all the fame and credentials to back it up (Hawking), but there is no evidence to distinguish the evaporating black hole theory from pure speculative fantasy.

    Science is not based on the opinion of famous physicists. Even Ethan’s.

  19. #19 eric
    May 22, 2017

    If nothing escapes the gravity of a black hole, how can they possibly “evaporate” … as when “twin virtual particles” are said to “pop out,”

    When a particle anti-particle pair forms just at the event horizon, the particle moves ‘away’ from the BH while the anti-particle moves towards it (i.e. falls in). The BH thus loses the mass equivalent of the anti-particle, while we outside the BH see it “emitting” the particle.

  20. #20 Michael Mooney
    May 22, 2017

    Eric,
    Please show empirical evidence for the particle moving away from the bh. The “event horizon” just means what we can see before gravity pulls *everything* into the gravity well of no return.
    Anything close will be pulled in… except psuedo -virtual- particles created only in theory… and “illustrated” by cool computer graphics. “It all depends on whom you ask.” Ask Ethan… or Hawking.

  21. #21 eric
    May 22, 2017

    Anything close will be pulled in… except psuedo -virtual- particles created only in theory…

    You misunderstand.Pairs created just outside the event horizon are, AIUI, the basis of Hawking radiation. There is nothing contradictory or physics-breaking about such a particle – existing outside the event horizon – escaping the gravitational pull of the BH.

  22. #22 Johnny
    May 23, 2017

    > Please show empirical evidence for the particle moving away from the bh.
    We do not have evidence for Hawking radiation and it’s very unlikely we’ll be able to detect something so weak. Unless we catch a black hole completely evaporating … which as Ethan explains won’t happen for unfathomable long time.

    Without experimental evidence for the Hawking radiation, Hawking would not get an all-paid trip to Stockholm – the Nobel committee doesn’t award the prize for theoretical work without an experimental evidence. The Hawking radiation is not real enough for a Nobel.

    That said, the Hawking radiation is a consequence of two highly successful theories and is in their “comfort zones” – so we need to take it seriously.

  23. #23 Michael Mooney
    May 23, 2017

    Some empirical science on the subject:
    In 2014 NASA’s Swift Mission captured images of event ASASSN-14li, as a star near a black hole disintegrated via the bh’s immense gravity and the debris field did a “death spiral” toward the bh event horizon.
    Stars near black holes are sucked in by gravity. So too must all other assorted matter in the vicinity of a bh. … even very small particles. Nothing escapes. It’s a “law of nature.” Quantum physics and its prominent theoreticians can not change that… just because Hawking claimed to “discover” “Hawking radiation” in his very fertile mind, with no empirical evidence to support it.

  24. #24 Elle H.C.
    May 23, 2017

    @Michael Mooney

    You are a bully.

    It wasn’t Length-contraction that was wrong but Einstein the person, now again it isn’t about Hawking-Radiation but Hawking himself, similarly you don’t care about what Ethan writes, you are only here to pick on him. You play the person, and not the ball.

    https://en.wikipedia.org/wiki/Bullying

    Relational

    This is any bullying that is done with the intent to hurt somebody’s reputation or social standing which can also link in with the techniques included in physical and verbal bullying. Relational Bullying is a form of bullying common amongst youth, but particularly upon girls. Relational bullying can be used as a tool by bullies to both improve their social standing and control others. Unlike physical bullying which is obvious, relational bullying is not overt and can continue for a long time without being noticed.”

  25. #25 dean
    May 23, 2017

    You are a bully

    .

    You spelled science denialistr incorrectly.

  26. #26 dean
    May 23, 2017

    *science denialist

  27. #27 dean
    May 23, 2017

    @Michael Mooney

    You are a bully.

    No, just someone convinced his beliefs are better than the science.

    His “arguments” are not much different in tone than those of the anti-vaccination people. In the vaccination/autism setting, the denialists have two targets: the studies that fail to show any link between vaccines and autism, and the (asserted) lack of studies on what happens when several vaccines are given at a time.

    In the first case the standard argument is “yes but” and then they give a list of things they believe the studies don’t cover. In the second the typical response is to deny the studies of multiple shots at once are capable of addressing the possibilities.
    In the end their arguments come down to “We simply don’t believe what the studies show.”

    MM began asserting that his “gut feeling” showed the predictions made by relativity and the observations that result from investigations into relativity were wrong. He’s now moved into multiple areas of denial.

    Evidence means nothing to conspiracy people (anti-vaccine people) or to cranks like MM. It isn’t bullying (IMO) but a belief that their “gut understanding” surpassess the research of the relevant scientists. The same thing is demonstrated by the common climate deniers.

  28. #28 John
    Baltimore
    May 23, 2017

    Elle,

    Yes, I agree. The synopsis here now drives the clicks there for the full story.

    John

  29. #29 tb29607
    May 23, 2017

    Can anyone tell me if quantum theory predicts black holes. I understand Einstein’s theories of relativity do but wondered specifically if quantum theory does as well.

  30. #30 Elle H.C.
    May 23, 2017

    @Dean

    What you describe here doesn’t exclude being a bully, it can be part of the process that leads to being one. Like I said, he doesn’t fixate on the problem but prefers the person. Read his post again in this thread. Check the characteristics:

    https://en.wikipedia.org/w/index.php?title=Bullying&mobileaction=toggle_view_desktop#Characteristics

    “a typical bully has trouble resolving problems with others and also has trouble academically. He or she usually has negative attitudes and beliefs about others”

    “Hawking claimed to “discover” “Hawking radiation” in his very fertile mind”

  31. #31 dean
    May 24, 2017

    a typical bully has trouble resolving problems with others and also has trouble academically.

    Maybe. I’m always sceptical of discussions of complex things on Wikipedia, but the two items in that quote do apply to mm (also to the anti-vaccination folks around my state, as well as the climate change deniers).

  32. #32 Michael Mooney
    May 24, 2017

    I cited recent (2014) empirical evidence, actual images of star debris spiraling into a bh. Clearly ALL particles near a bh are pulled in by its gravity field.
    Elle H.C. and dean ignored the evidence (science) in my post and attacked me personally (yet again) for pointing out the evidence clearly falsifying Hawking radiation. You two exemplify what you are accusing me of with a dose of guilt-by-association with science deniers thrown in.

    There is no evidence for or physics of shrinking physical objects as per length contraction either, since you brought it up again. (Not just a “gut feeling.”) Btw, I’ve never challenged that different frames of reference will see things differently.

    Do either of you or anyone else have anything to say about the substance of the post, i.e., in the spirit of unbiased scientific discussion?

  33. #33 eric
    May 24, 2017

    Can anyone tell me if quantum theory predicts black holes.

    AFAIK, nope. But also AFAIK our limited computational ability to use QM can’t predict the behavior of any large collection of particles with QM, even at the regular densities of solids and liquids.

    MM:

    Clearly ALL particles near a bh are pulled in by its gravity field.

    Think really hard about the fact that you are citing astronomical observations of the in-spiral to claim nothing from the in-spiral escapes.

  34. #34 Narad
    May 25, 2017

    There is no evidence for or physics of shrinking physical objects as per length contraction either, since you brought it up again.

    What you steadfastly refuse to grasp is that GR is a geometric theory. The coordinates that you hold so dear are merely calculational frosting.

    Seriously, the first 70 pages or so of Misner, Thorne, & Wheeler are available from G—le Books. Please read it.

  35. #35 Narad
    May 25, 2017

    Pick your “channel” for the daily wisdom from Dr. Siegel. Who knows who reads your comments on the same conversation.

    I recommend a competent administrator without an opinion on any issue.

    Start your own blog if you wish your taste to be catered to.

  36. #36 Robo
    Italy
    May 25, 2017

    Dear doctor Ethan I write to you from Italy. I have some difficulty in writing in English, but i am curious, so i try to make you a question or two.
    1) You said no threshold for the evaporation of a black hole but i thought that something like the Plank lenght were the threshold, if it’s true that space under this misure has no meaning…What am i not understanding about this issue?
    2) I read of an hypothethic graviton that mediates gravity force. But if it exists it can’t go faster that light. Since nothing escapes from the horizon events is it possible that the incompatibility between Einstein gravity and quantum theory is substantial?
    Thank you

  37. #37 Michael Mooney
    May 26, 2017

    @Narad #34
    I was speaking of the claim of * SR *, not GR… that the length of physical objects depends on the observer’s frame of reference. This is based on the SR dictum that measurements from all frames of reference are “equally valid” and that “length is not invariant,” i.e., it varies with the observer.
    Therefore, for instance, Earth’s diameter depends on the observer’s frame of reference. Ethan and all mainstream forums on SR (and Wikipedia) insist that objects vary in length “depending on whom you ask.” Seriously. Read up.

  38. #38 Narad
    May 26, 2017

    @Narad #34
    I was speaking of the claim of * SR *, not GR…

    And you think the latter doesn’t subsume the former?

  39. #39 Michael Mooney
    May 27, 2017

    Narad,
    In reply to dean, I was defending my criticism of SR as not merely a “gut feeling” but as a theory that claims that lengths of physical objects contract, depending on observational frames of reference. (No “as is” cosmos independent of differences in observation.) That’s why SR is so “special!” Of course it’s off topic here, but I was getting abuse about it again, as above.

    Dean: “…to claim nothing from the in-spiral escapes.” The evidence cited shows that nothing escapes. Hawking radiation has been falsified by direct empirical evidence.

  40. #40 Narad
    May 27, 2017

    I was defending my criticism of SR as not merely a “gut feeling” but as a theory that claims that lengths of physical objects contract, depending on observational frames of reference. (No “as is” cosmos independent of differences in observation.)

    There are no global inertial reference frames. How, exactly, do you propose measuring the absolute “sizes” that you keep demanding must be Real?

  41. #41 Narad
    May 27, 2017

    Hawking radiation has been falsified by direct empirical evidence.

    I see that this claim has gotten stronger, to wit, the previous version (emphasis added):

    Stars near black holes are sucked in by gravity. So too must all other assorted matter in the vicinity of a bh. … even very small particles. Nothing escapes. It’s a “law of nature.” Quantum physics and its prominent theoreticians can not change that… just because Hawking claimed to “discover” “Hawking radiation” in his very fertile mind, with no empirical evidence to support it.

    Look, man, the raw assertion that black holes are magical vacuum cleaners (modulo the totem word “near”) doesn’t mean that you understand what Hawking radiation is in the first place. If you have an objection, at least try to figure out the subject well enough to phrase it comprehensibly. Spluttering like this, your first comment, doesn’t cut it:

    Ps: [sic] I once read a very astute answer to a physics question on a Q&A site:
    “Where does Hawking radiation go?”
    Answer from the professor:
    “Nowhere. It stays in Hawking’s head!”

  42. #42 Michael Mooney
    May 28, 2017

    Narad:
    “There are no global inertial reference frames. How, exactly, do you propose measuring the absolute “sizes” that you keep demanding must be Real?”

    “Absolute?” Who said absolute? How about just actual physical sizes (lengths in this case) of objects as formed by the laws of nature independent of how one measures them. “Proper length” is measured from at rest with the object.
    We can expect distorted *images* of objects if ever measured from near light speed frames of reference. I have no problem with such hypothetical *appearances* of contracted images as conveyed by light to a high speed traveled. There is no physics of actual shrinking objects… like a contracted diameter of Earth, as an obvious example.

    “Look, man, the raw assertion that black holes are magical vacuum cleaners (modulo the totem word “near”) doesn’t mean that you understand what Hawking radiation is in the first place”

    “Raw assertion?… magical vacuum cleaners?” Study the universal law of gravitation. Mass attracts mass… etc. No magic. No “spluttering” about it. The evidence cited from NASA’s 2014 Swift Mission clearly shows the debris field from a star disintegrated by a black hole’s gravity spiraling into it.
    How do you suppose Hawking’s “virtual particles of radiation” (just one of each pair of course) escape when star dust can not? How are they immune from the pull of gravity that eats nearby stars?

  43. #43 eric
    May 28, 2017

    How do you suppose Hawking’s “virtual particles of radiation” (just one of each pair of course) escape when star dust can not?

    The same way other things escape; by having a high enough momentum. You understand that anything outside the event horizon can escape a BH, right? Not everything does, but there is no physical law preventing it.

  44. #44 Michael Mooney
    May 28, 2017

    eric,
    I understand that things with enough momentum outside a bh can escape and not be sucked in by gravity. However, the claim is that a bh can lose mass (already within the horizon) until it all “evaporates” via escaping radiation.

    The inventor of that claim also said (about gravity):
    “Because there is a law such as gravity, the universe can and will create itself from nothing.”
    Since gravity is generated by mass, one must wonder how gravity created the universe and its mass “from nothing.” This is belief in magic, not science. Buy that and Hawking radiation (or anything else he claims) is no problem to swallow.

  45. #45 Narad
    May 28, 2017

    How do you suppose Hawking’s “virtual particles of radiation” (just one of each pair of course) escape when star dust can not?

    Has it ever occurred to you to read the original rather than pop-sci versions?

    “It should be emphasized that these pictures of the mechanism responsible for the thermal emission and area decrease are heuristic only and should not be taken too literally. It should not be thought unreasonable that a black hole, which is an excited state of the gravitational field, should decay quantum mechanically and that, because of quantum fluctuation of the metric, energy should be able to tunnel out of the potential well of a black hole. This particle creation is directly analogous to that caused by a deep potential well in flat space-time [18]. The real justification of the thermal emission is the mathematical derivation given in Section (2) for the case of an uncharged non-rotating black hole. The effects of angular momentum and charge are considered in Section (3). In Section (4) it is shown that any renormalization of the energy-momentum tensor with suitable properties must give a negative energy flow down the black hole and consequent decrease in the area of the event horizon. This negative energy flow is non-observable locally.”

  46. #46 Narad
    May 28, 2017

    Narad:
    “There are no global inertial reference frames. How, exactly, do you propose measuring the absolute “sizes” that you keep demanding must be Real?”

    “Absolute?” Who said absolute? How about just actual physical sizes (lengths in this case) of objects as formed by the laws of nature independent of how one measures them.

    It would help if you tried to maintain at least some sort of semblance of rationality.

  47. #47 Narad
    May 28, 2017

    ^

    “Proper length” is measured from at rest with the object.

    But that’s not observer independent, now is it? Thus it’s apropos of nothing. Hey, remember this?

    Study the universal law of gravitation. Mass attracts mass… etc.

    Given that the second sentence is false in GR, I suggest that you take your own advice.

  48. #48 eric
    May 28, 2017

    MM:

    I understand that things with enough momentum outside a bh can escape and not be sucked in by gravity. However, the claim is that a bh can lose mass (already within the horizon) until it all “evaporates” via escaping radiation.

    So you should understand that when virtual particle formation occurs outside the event horizon, and the mass particle has enough momentum to escape, this will be the functional equivalent of the BH emitting radiation and losing mass.

    The inventor of that claim also said (about gravity): “Because there is a law such as gravity, the universe can and will create itself from nothing.” Since gravity is generated by mass, one must wonder how gravity created the universe and its mass “from nothing.”

    You have completely misunderstood Hawking. His claim is not that gravity created the universe. Its that a universe with a gravitational law like ours (plus QM, which is critical to his claim) can arise spontaneously, without a prior causal event.

    Hawking’s claim is still hypothetical/unproven. But at least have the decency to read it and understand it before you reject it.

  49. #49 Michael Mooney
    May 28, 2017

    eric,
    You falsely assume that I have not studied Hawking radiation, presumably because I don’t agree with his theoretical physics on evaporating black holes and how gravity created the universe ‘from nothing” and how everything in the universe came out of a “point” of zero volume and infinite mass density. Study the context of all these claims. I have followed him since he was just barely famous.
    He is the newest and “leading” pop star of physics since Einstein. Disagree with either and you will not get your doctorate in theoretical physics. (And folks like you will harass the critic on on forums like this one.)

  50. #50 Narad
    May 28, 2017

    He is the newest and “leading” pop star of physics since Einstein. Disagree with either and you will not get your doctorate in theoretical physics.

    Do go on.

  51. #51 eric
    May 29, 2017

    You falsely assume that I have not studied Hawking radiation,

    No, I observe you making much more fundamental errors involved with misunderstanding the science. Like citing astronomical observations of in-spiraling to claim that nothing escapes from the in-spiral. That statement involves a much more basic error than not understanding Hawking radiation.

    Or your latest, claiming The Grand Design is about gravity creating the universe. That’s another blatant misunderstanding.“Since gravity is generated by mass, one must wonder how gravity created the universe and its mass “from nothing…” is just plain wrong. No two ways about it. Do you even understand why it is wrong?

    Disagree with either and you will not get your doctorate in theoretical physics.

    Now that’s just funny. Clearly you’re unaware that pretty much everyone disagrees with Einstein’s opinion about the cosmological constant (he thought it was a blunder; everyone pretty much disagrees now).

    You also seem to be unaware that Hawking is fond of making bets with other physicists…and regularly loses them. Scientists disagree with him all the time, and it’s not at all bad for their careers.

  52. #52 Michael Mooney
    May 29, 2017

    Narad,
    It was meant as a general observation, not as a personal testimony. Science is not based on popularity or personal opinion, whatever one’s “degree” or popularity.

  53. #53 Michael Mooney
    May 29, 2017

    eric: “Or your latest, claiming The Grand Design is about gravity creating the universe. That’s another blatant misunderstanding.“Since gravity is generated by mass, one must wonder how gravity created the universe and its mass “from nothing…” is just plain wrong. No two ways about it. Do you even understand why it is wrong?”

    GET A GRIP! I was quoting Hawking spouting nonsense, not agreeing with him. (Have your reading comprehension checked.)

  54. #54 Michael Mooney
    May 29, 2017

    eric,
    I missed a piece: “You also seem to be unaware that Hawking is fond of making bets with other physicists…and regularly loses them.”

    No. I’m aware of that, for decades.
    It goes to show that he is playing on his popularity (still) to stay in the limelight whether he is “right or wrong.” No matter. It seems to be just a game for him. (Who’s on top?) But it passes for science these days.

  55. #55 dean
    May 29, 2017

    “Disagree with either and you will not get your doctorate in theoretical physics.”

    If I were a betting man my money would be on you not having any supporting evidence for this, since you’ve never supported your “objections” to relativity with anything resembling science, but: what reason do you have for making your claim?

  56. #56 eric
    May 29, 2017

    I was quoting Hawking spouting nonsense

    He’s not spouting nonsense; you just don’t understand what he’s saying. Go on, prove me wrong. Show me you actually understand his point by explaining it.

    You also seem to be unaware that Hawking is fond of making bets with other physicists…and regularly loses them.”

    No. I’m aware of that, for decades.

    If you were aware that physicists regularly and publicly disagree with Hawking and this doesn’t end their careers, then why did you claim disagreeing with Hawking ends ones’ physics career?

  57. #57 Narad
    May 29, 2017

    But it passes for science these days.

    Quoth the Newtonian. By all means, hep everyone to your CV.

  58. #58 Narad
    May 29, 2017

    ^ Sorry, “cosmic-minder and Newtonian.”

  59. #59 Narad
    May 29, 2017

    He is the newest and “leading” pop star of physics since Einstein. Disagree with either and you will not get your doctorate in theoretical physics.

    Do go on.

    It was meant as a general observation, not as a personal testimony.

    </blockquote

    OK, do go on without a non sequitur.

  60. #60 Michael Mooney
    May 30, 2017

    Clearly all critics of relativity are considered cranks by its mainstream believers. Never mind that physical objects don’t actually shrink as a result of differences in observation or that spacetime is a geometric/ math model, not an actual malleable medium (“fabric”) in the observable cosmos. Obviously such “cranks” can not pass the textbook tests for higher degrees.
    Hawking has been proven wrong enough times that it’s a wonder anyone takes him seriously anymore with his high flights of fantasy (coated with plenty of math to make it easier to swallow for mathematicians.) But his lost bets were with his peers, not undergrads, who tend to worship him as the new Einstein… not to be questioned until his foolishness is exposed.
    As I’ve said before, I’ve been an amateur scientist all my adult life (now 72) and followed the arguments and criticisms on the net since i got my first computer. There is no shortage of critics with stories of how mainstream academia rejected their “wrong answers” to the established doctrines of relativity, astrophysics and cosmology.

    That said, can anyone explain how black holes actually lose mass from within their event horizons. Btw, “Because Hawking says so” is not a legitimate answer. Look at his record.

  61. #61 eric
    May 30, 2017

    Clearly all critics of relativity are considered cranks by its mainstream believers.

    No, not at all. MOND theories would imply GR is wrong, and many MOND researchers are taken seriously.

    Your particular complaints are not taken seriously because your particular complaints have never been published, you’ve never done any credible research supporting them, and because you can’t even quantify your objections in a way that allows other people to test if they are right. heck, you can’t even come up with a mere thought experiment test of them.. But other people who have published, have done research, and have quantified their ideas – “put a scientific stake in the ground” so to speak – are taken seriously.

    Sagan famously said “The fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown.” I would add to that comment: the fact that they laugh at you like Bozo does not mean all geniuses are laughed at like Bozo. It just means you’re not one of the geniuses.

  62. #62 eric
    May 30, 2017

    That said, can anyone explain how black holes actually lose mass from within their event horizons.

    Ethan referred to the answer. Sean T. did too in @17. Narad practically handed it to you on a silver platter in @45. Perhaps you should go back and read the OP as well as their responses.

  63. #63 Michael Mooney
    May 31, 2017

    eric,
    Check out his new (today’s) post. He went from evaporating black holes to “”Nothing Escapes From A Black Hole, And Now Astronomers Have Proof…” in just 11 days!

  64. #64 eric
    May 31, 2017

    I read it for content. There is nothing, nada, zero, zip cogent about your complaint. Perhaps, as Naked Bunny suggested, you should try reading past the headline (ironically, the exact same failing I pointed out in my last reply to you).

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