What is Hawking radiation: Definition and 202 Discussions

Hawking radiation is black-body radiation that is predicted to be released by black holes because of quantum effects near the black hole event horizon. It is named after the physicist Stephen Hawking, who developed a theoretical argument for its existence in 1974.The requirement that black holes lose energy into the wider universe, and therefore can "evaporate" and the radiated spectrum are both a result of analysing black hole thermal equilibrium combined with extreme redshifting effects very close to the event horizon, with some consideration of quantum entanglement effects. A pair of virtual waves/particles arises just outside the event horizon due to ordinary quantum effects. Very close to the event horizon, these always manifest as a pair of photons. It may happen that one of these photons passes beyond the event horizon, while the other escapes into the wider universe ("to infinity"). A close analysis shows that the exponential red-shifting effect of extreme gravity very close to the event horizon almost tears the escaping photon apart, and, in addition, very slightly amplifies it. The amplification gives rise to a "partner wave", which carries negative energy and passes through the event horizon, where it remains trapped, reducing the total energy of the black hole. The escaping photon adds an equal amount of positive energy to the wider universe outside the black hole. In this way, no matter or energy ever actually leaves the black hole itself. A conservation law exists for the partner wave, which in theory shows that the emissions comprise an exact black body spectrum, bearing no information about the interior conditions.Hawking radiation reduces the mass and rotational energy of black holes and is therefore also theorized to cause black hole evaporation. Because of this, black holes that do not gain mass through other means are expected to shrink and ultimately vanish. For all except the smallest black holes, this would happen extremely slowly. The radiation temperature is inversely proportional to the black hole's mass, so micro black holes are predicted to be larger emitters of radiation than larger black holes and should dissipate faster.

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  1. shounakbhatta

    Hawking radiation and its significance

    Hello All, I have been trying to understand the exact contribution of our legendary physicist, Dr.Hawking and found that Hawking radiation is amongst one. Is it that Hawking radiation is the first attempt to unify, general relativity, quantum mechanics and thermodynamics which led to the...
  2. Superposed_Cat

    How Does Hawking Radiation Influence the Black Hole Information Paradox?

    Hi all, to begin this is my understanding of hawking radiation. A particle/anti-particle pair is generated. one particle outside the event horizon of a black hole, the other inside. The gravitational force "boosts" the one particle into being real. this energy is compensated for by endowing...
  3. Superposed_Cat

    Light Entering Black Hole: Hawking Radiation Explained

    Hi all, I was wondering if, when a beam of light is pulled towards a black hole , because it can't accelerate, it is blueshifted? Thanks in advance.
  4. J

    The paradox of Hawking radiation - is matter infinitely compressible?

    The hypothetical Hawking radiation means that a set of baryons can be finally transformed, "evaporate" into a massless radiation - that baryons can be destroyed. It requires that this matter was initially compressed into a black hole. If baryons can be destroyed in such extreme conditions, the...
  5. S

    Can't figure out how hawking radiation fixes thermodynamic problem

    Hi, I've tried several times to get my head around this, but every way I look at it Hawking Radiation doesn't seem to fix the thermodynamic issues it was supposed to solve. People who are a lot smarter than me seem to believe it's real, so can someone please point out where I'm going wrong...
  6. D

    Hawking Radiation and Shrinking Black Holes

    I was wondering whether anyone could provide an explanation as to why when two particles are created near the event horizon, only the negative energy particle is captured by the black hole, and the positive particle travels outward and is seen as Hawking Radiation. I have read numerous posts...
  7. K

    Free falling into a black hole that evaporates by Hawking Radiation

    The solution of Einstein's field equations for a simple black hole show a slowing of time as you get close to the black hole. Time stops at the event horizon. An observer in flat spacetime far from the hole would see an astronaut fall slower and slower as he approaches the event horizon. It...
  8. Q

    Hawking radiation and Black hole evaportion

    When the 'evaporation' of a black hole supposedly occurs, it is always attributed to 'Hawking radiation.' As I understand it, Hawking radiation occurs when a virtual particle pair is 'split' at the exact edge of an event horizon. When this occurs, one of the particle pair escapes to 'normal'...
  9. Crazymechanic

    Hawking radiation , black hole size

    Hi. If the hawking radiation is emitted from outside the event horizon , because probably that's the last place where the particles are being able to escape, then how come huge black holes ever evaporate as the matter behind event horizon has no chance of escaping in any way as to the immense...
  10. T

    Why do smaller black holes emit more Hawking radiation?

    Why is it that the smaller a black hole is, the more Hawking radiation it emits? It seems counterintuitive to me. I would think that a larger black hole with a larger surface area would trap more antiparticles from virtual particle antiparticle pairs, hence emitting more Hawking radiation.
  11. rjbeery

    Does Hawking Radiation preclude EH formation?

    Discussions involving Hawking radiation in the study of black holes usually require their preexistence; however, if we apply the Hawking radiation process to the initial stages of a birthing black hole I'm confused about how the theory claims the event horizon would form in the first place. In...
  12. L

    Why doesn't hawking radiation prevent a space-like singularity

    As I understand it, as a particle is observed approaching an event horizon, will would never be observed to cross the horizon, and it's red shift would tend towards infinity. I've read conflicting things about this, A, that that red shift WOULD NOT reach infinity in a finite time, and B, that...
  13. N

    Hawking Radiation inside a Black Hole?

    I've seen it said somewhere that an observer falling into a black hole doesn't notice anything qualitatively unique at the exact moment they cross the event horizon. Does this include Hawking radiation? That radiation is described as being emitted by the event horizon, so once the observer...
  14. R

    Is Hawking Radiation inherently unimportant?

    I know their is a theoretical answere to this or else the theory would have no traction... If a black hole emits a particle at a high speed, wouldn't logic say that the black holes immense gravity simply pull it back in? Also, what kind/size particle is theorized to eject?
  15. W

    What's the color of Hawking radiation?

    What's the "color" of Hawking radiation? If I understand correctly, the Hawking radiation hypothesis predicts that if a pair of virtual particles appears very close to the event horizon of a black hole, it may happen that one of them falls into the black hole and the other escapes, becoming a...
  16. D

    Calculation on hawking radiation in schutz (pg 324)

    on pg 324 of Schutz's "A First Course in General Relativity", i am having a little trouble with the integral (11.100). the book says that to first order in \epsilon , the answer should be 2\sqrt{2M\epsilon} but i keep getting \sqrt{2M\epsilon} . i am missing that factor of 2 somehow. the...
  17. Orion1

    Hawking radiation and cosmic microwave background radiation

    In order for the black hole to evaporate it must have a temperature greater than that of the present-day black-body radiation of the Universe. Cosmic microwave background radiation temperature: T_u = 2.725 \; \text{K} Hawking radiation temperature: T_H = \frac{\hbar c^3}{8 \pi G M k_B}...
  18. J

    Does any gravitating body emit Hawking radiation?

    The Hawking-Unruh temperature is given by the expression: \large T = \frac{\hbar g}{2 \pi c k} where g is the gravitational acceleration at the surface of a black hole. Does this expression imply that any gravitating body will emit Hawking radiation? For example if we take the...
  19. P

    Hawking Radiation and the Hologram Theory

    According to Hawking Radiation, a black hole if left alone will eventually evaporate. As the black hole loses mass the area of the event horizon shrinks until both are gone. The Hologram Theory says that as matter falls past the event horizon all the information pertaining to that matter is...
  20. T

    Redshift and time dilatation of Hawking radiation

    Micro black holes should in principle be observable by emitting Hawking radiation. However, as this takes place extremely close to the event horizon, shouldn't one expect then extreme redshifting (z = 1/(1-Rs/R)^-1/2 -1, Rs = Schwarzschildradius, R = Radius of Emission) and time dilatation? In...
  21. R

    Why can Hawking Radiation not work in reverse?

    I understand that to obey conservation that the black hole must lose energy and mass and the surrounding space must gain an equal amount of energy and mass. Then why can the antiparticle not be emitted from the black hole, adding negative energy and mass to the surrounding space, and the...
  22. J

    A question on virtual antiparticles and Hawking Radiation

    I know that Hawking Radiation is caused by the separation of virtual particles on the event horizon of a black hole, but I do not understand why the antiparticle is always the particle from the pair that falls into the black hole. It seems to me that the gravitational effects of the black hole...
  23. Y

    Hawking radiation and negative gravitational charge

    I was wondering if virtual anti particles had a postulated anti gravitational charge if that would be inconsistent with Hawking radiation as virtual anti particles would always be ejected from the vicinity of the Schwarzschild radius whereas virtual particles may or may not be ejected depending...
  24. N

    Why should Hawking radiation decrease a black hole's size?

    So from what I understand when the particle anti-particle pairs that are constantly being created and annihilated come into existence near a black hole's horizon, the nearer one can get sucked in while the further one can radiate off as though it were heat. And this radiation of energy decreases...
  25. J

    Question about Hawking radiation in BH

    i have read about Hawking's theory of BH radiation based on the idea of spontaneous particle pair creation at the EH wherein, on occasion, one of the particles is absorbed by the BH while the other escapes to become real. since the one which is absorbed is always of negative energy (whatever...
  26. C

    Hawking Radiation and Particle/Anti-Particle

    My (very basic) understanding of at least some form of Hawking Radiation is that, upon the formation of a particle/anti-particle pair near the event horizon, the black hole sucks in an anti-particle leaving the non-paired particle to go off into the universe as "radiation." But what about the...
  27. S

    Is Quantum Tunneling a Source of Hawking Radiation?

    Hi PF I was wondering, if Hawking radiation could have a different source than black-body radiation. I was wondering, if quantum tunneling could be a possible way, for energy to slip out of the grasp of the black holes gravitational attraction and slip through the event horizon. Would this be...
  28. M

    Calculational details of Hawking radiation

    Can anybody help me with the original calculations of hawking radiation. I am working out the details of Hawking's original paper on black hole radiation. I am getting stuck at many places. Does anyone know about some place where the detailed calculations can be found.
  29. B

    Exploring the Reality of Hawking Radiation: Observations and Implications

    Has hawking radiation ever been observed?
  30. U

    Equation for the energy of Hawking Radiation

    What is the equation for the energy/frequency of Hawking radiation emitted from a black hole? Thank you in advance! EDIT: I found this http://library.thinkquest.org/C007571/english/advance/core5.htm but the website doesn't seem to be a legitimate source and it doesn't give the derivation of the...
  31. Pengwuino

    Hawking Radiation w/out black holes

    I stumbled upon an article while doing some research that had a statement saying that Hawking radiation can be found in places beyond black hole horizons. This lead me to this paper (which I'm not actually interested in beyond it's reference to the existence of hawking radiation outside of...
  32. R

    How can hawking radiation escape?

    how can hawking radiation escape from a black hole? thanks
  33. M

    Hawking radiation from a black hole?

    In his theory, Stephen Hawking suggests that a black hole will give off thermal radiation. Radiation is light, so how can light escape the gravity of a black hole, especially originating from one? The only way I could see this was that if radiation were traveling beyond the speed of light, but...
  34. L

    Hawking Radiation: Is it Emitted Due to Quantum Effects?

    Is it true to say that Hawking radiation isn't actually the temperature of the black hole but rather, the temperature of the thermal radiation it emits due to quantum effects? Thanks.
  35. J

    One more time on Hawking radiation

    i have posted a few questions regarding Hawking radiation in the past, regarding the assumption of "negative energy" of the particle which falls into the BH. i have tried to do as much reading as i can on the topic, since i have had a very hard time absorbing the concept of negative energy...
  36. R

    Virtual Particles and Hawking radiation

    I was having a conversation with a physicist on Facebook (author of a book I rather enjoyed - "Users guide to the universe"), and he let the conversation end without my question ever being fully answered. Perhaps someone here can help explain this to me. I'll paste the entire conversation...
  37. jaketodd

    Hawking Radiation seems contrary to black hole dynamics

    My understanding of Hawking Radiation is that a particle and anti-particle form at the event horizon, the particle escapes, the anti-particle goes into the black hole, annihilates a particle at the core of the black hole, and energy is released, leading to an evaporating black hole. But how do...
  38. A

    Hawking Radiation: Does it Really Shrink Black Holes?

    I read about Hawking Radiation a while ago (Scientific American?), and just thought of something that seems to not agree with it: Unless my memory is wrong, then at the event horizon the virtual particle pairs of the "vacuum" are split, and the anti-particle falls into the black hole, and the...
  39. P

    On when does Hawking radiation begin?

    On "when does Hawking radiation begin?" I have wondered about when, during collapse, Hawing radiation starts (given that an outside observer never sees the horizon reached, classically at least), and asked this here without getting answers (presumably, because there is no well founded answer)...
  40. P

    When does Hawking radiation begin?

    This question has bothered me sometimes. For 'standard' black hole with an event horizon, an external observer never sees matter cross the horizon (or get any signal from inside); while an infalling observer crosses the horizon and, for a very big black hole, may not even notice any extreme...
  41. E

    Hawking radiation redshift (?)

    I think it was proven that firing a photon (laser) straight up from the surface of Earth did in fact redshift the photon and decrease its frequency. And now, when we consider a black hole and Hawking radiation... I mean - the gravity inside the event horizon is so strong that EM cannot escape...
  42. P

    Analog of Hawking Radiation Observed?

    Didn't see a post about this yet. http://arxiv.org/abs/1009.4634
  43. Q

    Hawking radiation & quarks/gluons

    The theory of "Hawking radiation" says that black holes can emit different particles. We have a particle-antiparticle pair and one of them falls into the black hole while the other one escapes. On the other hand, we know that particles with color charge like quarks or gluons cannot travel...
  44. K

    How Does Hawking Radiation Affect Black Hole Mass?

    I've read as much on the subject as I can before getting into the actual math of it, so I need people who know the subject better then I do to answer my question. The way I understand it, at the quantum level, particle/anti-particle pairs are created all the time and annihilate before they...
  45. E

    Does string theory/LQG predict Hawking radiation?

    Actual experimental aparatus, measurements and all that, see figure 2 on page 6 http://arxiv.org/abs/1008.1911 Measurement of stimulated Hawking emission in an analogue system Silke Weinfurtner, Edmund W. Tedford, Matthew C. J. Penrice, William G. Unruh, Gregory A. Lawrence (Submitted on 11 Aug...
  46. stevebd1

    Derivation of Hawking Radiation

    I'm not quite sure how reliable http://library.thinkquest.org/C007571/english/advance/core4.htm" as a source but I thought it provided a good derivation for the Hawking Radiation equation relative to the Heisenberg uncertainty principle- First the energy of the radiation is established-...
  47. R

    Other universes vs Hawking radiation

    So, when you plunge into a rotating black hole, according to penrose diagram one could travel to different universes, but at the same time black holes emit particles by hawking radiation. So what happens to an object inside the black hole? Do I make an error in reasoning somewhere?
  48. D

    Opinions Sought on Hawking Radiation and High Energy Collisions

    Can someone give some opinions on the following? The 2 main arguments from this site i can tell are: that hawking radiation isn't proven. And that high energy collisions in the upper atmosphere travel at a fast speed & the small black holes can escape from Earth unlike in the lhc. I...
  49. C

    Hawking Radiation & Parity Imbalance: Matter vs. Anti-Matter

    Does Hawking radiation account for the parity imbalance between matter and anti-matter? Do Black Holes create matter? If a matter/anti-matter pair materializes on either side of the event horizon of a black hole: 1) if the matter particle is on the inside of the event horizon, the mass of the...
  50. K

    What are the unanswered questions about Hawking radiation and the Unruh effect?

    1)when hawking first propounded this thermal radiation, he took into acount the the gravitational cllapse. so I am not sure, if we consider a stationary system, then there won't be any particle creation. Is this the case? because I think there will not be any mixing of posive and negative...
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