# Is Hawking any closer to solving the puzzle of black holes?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Aug 28, 2015.

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Is Hawking any closer to solving the puzzle of black holes?
August 28, 2015 by Geraint Lewis, The Conversation

But after it has completely evaporate, where did all that quantum information go? The potential solutions and counter solutions to this have given us the black hole wars, were key researchers have argued about different ways that information could escape.

Hawking's latest pronouncement is the next salvo in the war, changing his view that the information is somehow stored and is eventually released when the black hole in the final stage of evaporation.

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The link includes a short video of a lecture hawking was giving members of the swedish Institute of Technology.

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Another BH article not related to the above, but revealing in their relationship to QUASARS.

Astrophysicists find supermassive black holes in quasar nearest Earth
August 27, 2015 by Robert Gutro

Astronomers using NASA's Hubble Space Telescope have found that Markarian 231 (Mrk 231), the nearest galaxy to Earth that hosts a quasar, is powered by two central black holes furiously whirling about each other.

The finding suggests that quasars—the brilliant cores of active galaxies—may commonly host two central supermassive black holes that fall into orbit about one another as a result of the merger between two galaxies. Like a pair of whirling skaters, the black-hole duo generates tremendous amounts of energy that makes the core of the host galaxy outshine the glow of the galaxy's population of billions of stars, which scientists then identify as quasars.

7. ### SchmelzerValued Senior Member

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The basic error about all this black hole evaporation is that black holes will probably not radiate at all, except for a few seconds after the collapse. The problem is named in the literature the "transplanckian problem", and officially described in the form that the prediction of black hole radiation requires some assumptions about distances lower than Planck length. Which is a formally correct but very misleading information. Because even if for distances much much smaller than Planck length, say $10^{-10000}l_{Pl}$, everything is fine, it does not help much, because it will add only a few second, may be minutes (depends on how much 0 used in the exponent) to the Hawking radiation. If there will be some Hawking radiation after this is completely unclear at best.

A "theory" which depends on assumptions about distances much much lower than $10^{-10000}l_{Pl}$ is nothing what could be taken seriously. And those who accept it nonetheless can be, without much risc, ignored as pseudoscientists.

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The theoretical application of hawking Radiation, makes sense. The error seems to rest with your own agenda laden take on that application.

Hawking Radiation despite your ranting, is held in high regard and a logical application with reasonable assumptions.
Of course I prefer listening to expert opinion as distinct from your own.....

Classically, black holes are black.
Quantum mechanically, black holes radiate, with a radiation known as Hawking radiation, after the British physicist Stephen Hawking who first proposed it.

The animation at top left cartoons the Hawking radiation from a black hole of the size shown at bottom left. The blobs are supposed to be individual photons. Notice, first, that the photons have sizes' (wavelengths) comparable to the size of the black hole, and, second, that the Hawking radiation is not very bright - the black hole emits roughly one photon every light crossing time of the black hole. So a black hole observed by its Hawking radiation looks fuzzy, a quantum mechanical object.

This is one animation that I did not compute mathematically. How do you draw a quantum mechanical object, whose appearance depends not only on the object but also on the way the observer chooses to observe it? I figured my impressionism was good enough here.

Hawking radiation has a blackbody (Planck) spectrum with a temperature T given by

kT = hbar g / (2 pi c) = hbar c / (4 pi rs)

where k is Boltzmann's constant, hbar = h / (2 pi) is Planck's constant divided by 2 pi, and g = G M / rs2 is the surface gravity at the horizon, the Schwarzschild radiusrs, of the black hole of mass M. Numerically, the Hawking temperature is T = 4 × 10-20g Kelvin if the gravitational acceleration g is measured in Earth gravities (gees).
The Hawking luminosity L of the black hole is given by the usual Stefan-Boltzmann blackbody formula

L = A sigma T4

where A = 4 pi rs2 is the surface area of the black hole, and sigma = pi2k4 / (60 c2 hbar3) is the Stefan-Boltzmann constant. If the Hawking temperature exceeds the rest mass energy of a particle type, then the black hole radiates particles and antiparticles of that type, in addition to photons, and the Hawking luminosity of the black hole rises to
L = A (neff / 2) sigma T4

where neff is the effective number of relativistic particle types, including the two helicity types (polarizations) of the photon.black hole at the centre of the galaxy Messier 87. The Hawking radiation from such black holes is minuscule. The Hawking temperature of a 30 solar mass black hole is a tiny 2×10-9 Kelvin, and its Hawking luminosity a miserable 10-31 Watts. Bigger black holes are colder and dimmer: the Hawking temperature is inversely proportional to the mass, while the Hawking luminosity is inversely proportional to the square of the mass.

9. ### SchmelzerValued Senior Member

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The only problem is that my "ranting" refers to a well-known and acknowledged problem which has even a Wiki entry https://en.wikipedia.org/wiki/Trans-Planckian_problem but is not even mentioned in your "expert opinion".

10. ### BdSRegistered Senior Member

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497
The last time I thought about this topic I got to. The BH's local time is highly dilated and its emitted EM is shifted/dilated out of the visible range and thats why we cant see anything happening there. If we were in the same BH dilated frame, perhaps the BH would emitting large amounts of energy. When a emitter is time dilated it locks the frequency to it's dilated frame, to a remote observers frame with a different time dilation he sees a different frequency (us looking a BH for example). Maybe they both agree on the distance the EM moved c, but not the frequency. Same reason satellites clocks have to compensate for time dilation, theres a change in the clocks energy transfer compared to our different dilated frame.

11. ### wellwisherBannedBanned

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If a blackhole emitted wavelengths longer than we can measure, we would not see these. Have anyone ever ruled out extreme wavelengths, beyond technology, using science experiment instead of just theory?

The EM spectrum is concerned with electro-magnetic. Say EM has become neutralized and converted to gravity in the black hole. We should not see any EM energy escaping, since the needed phases are not there. What we do see is space-time expanding as we leave the black hole. Is this expansion due to a form of energy emitted?

A red shift causes the value of the original energy quanta to lower. Where does the energy difference go if we apply energy conservation? Is the difference in energy value supply the work used to expand space-time?

12. ### BdSRegistered Senior Member

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Can dark energy or dark matter escape a blackhole?

13. ### SchmelzerValued Senior Member

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"Dark energy" is, in its most popular mainstream version, a name for a term in the GR equations, also named the cosmological constant, thus, something which does not move at all.

Dark matter is usual matter, simply not visible, thus, cannot escape.

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• I didn't say anything about there not being a problem, but my claim stands re hawking Radiation being a logical process.
• A few points you fail to recognise, [1] WIKI is certainly not the be all and end all of reputable links. They are easily trumped by reputable links from learned institutions and such, and [2] The Planck scale is no more than a theoretical application or arbitrary number, denoting where the quantum effects of gravity cannot be ignored. And [3] nowhere did I ever say my opinion was "expert", but I do try to link to expert opinion.
DE is a constant aspect of spacetime that exists everywhere and is part and parcel of that same spacetime.
• DM certainly is gravitationally affected by BHs, as much as baryonic matter is and therefor does not escape.

15. ### The GodValued Senior Member

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3,546
The argument while proposing 'Hawking radiation' was not to solve Information paradox, but to give a life span to BH, vanishing of BH due to evaporation.

Hawking knew from the day one that this premises is faulty, mainly because of direct conflict with CMBR, an attempt to link the same with thermal radiation also would have failed due to very definition of BH. So Hawking came up with this another masterstroke that the entire information of the falling matter is available at Event Horizon, and due to Hawking Radiation the same is extracted back and not lost. So the paradox issue is solved. It appears that there are less takers now for this proposition.

The formation of particle/antiparticle pair at EH itself is probabilistic event, not at all deterministic, and the bigger issue is dynamically changing value of Event Horizon due to CMBR absorption, which may create a situation that positive energy particle too may fall back inside EH. An all isolated BH is improbable concept. Double whammy.

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Perhaps its a Black Neutron Star [tic mode on of course]

What needs to be remembered of course is that no quantum firewall effect invalidates the existence of BHs in any sense whatsoever.....Unless of course unlike our old friend rajesh, you are able to come up with a observationally validated alternative to what we see as BHs.

The other point that was also denied strenuously by our old friend rajesh was as detailed by Prof Lewis in the OP article, that BHs can only have three properties, mass, spin and charge
from the article.....
"Only a few properties of the infalling material are remembered, imprinted on the black hole's gravitational field, namely the mass, the charge and the angular momentum. All other properties appear to be promptly forgotten; neglecting spin and charge, all black holes of the same mass are identical, whether they were built of collapsing stars or from an immense number of tennis balls".

Last edited: Aug 30, 2015
17. ### SchmelzerValued Senior Member

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I know, of course, that Wiki is not a reputable source. It is much better in scientific questions than in political ones, where one can consider it only as a collection of popular desinformation. But, nonetheless, it is not a source with high reputation. The point of my "even a Wiki entry" was that the problem itself is sufficiently widely known. Agreement about [2]. This was, by the way, my point that the problem is much more serious: The problem is not that one uses some assumptions about distances below Planck length, but that one needs assumptions about much much smaller distances. And what I have criticized was your link, which did not even mention the problem. Thus, your error is only to listen to sources which simply ignore the problem.

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Being a purely arbitrary figure, the problem may not even exist.

19. ### SchmelzerValued Senior Member

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The problem certainly exists. Because it is a problem of the derivation of the existence of Hawking radiation. And so it is present already in the first paper of Hawking about black hole radiation.

Let's formulate it in the following way: If GR is correct, nothing after horizon formation can influence something outside. So, what radiates comes from a domain before the collapse has finished. But let's assume now that GR becomes wrong for extremal time dilations. Time dilation becomes extremal near the horizon. So, let's assume that the modification is a simple one, the collapse simply stops at the radius $r_S+\varepsilon$ slightly greater than the Schwarzschild radius for some extremely small $\varepsilon\ll l_{Pl}$. The point of this special modification is that in this case one can compute the result in a sufficiently exact way, and the result is very simple: There will be Hawking radiation during the collapse time, but not after the collapse has stopped at $r_S+\varepsilon$. Of course, the collapsing body has to reach this distance, and after this, the last bit of Hawking radiation has to go out and to reach the outside observer, but the time necessary for this is quite small, and increases only like $-\log \varepsilon$ with decreasing $\varepsilon$, and therefore it is almost completely irrelevant which particular value of $\varepsilon$ one uses - the Hawking radiation stops after a quite short period of time. To increase the time of Hawking radiation by some quite short fixed amount of time $r_S/c$, one has to divide $\varepsilon$ by a fixed constant, which was e or so IIRC.

One can reformulate the problem in another language. You may have heard about infinities in QFT and the renormalization techniques used to solve them. The technique is, in the general idea, quite simple - use a lattice approximation, with a distance $\varepsilon$ between lattice nodes, take a sufficiently small value of $\varepsilon$, and recompute everything in such a way that one can get rid of the $\varepsilon$-dependence. In this case, it does not matter what $\varepsilon$ you choose, because anyway Hawking radiation will not last very long, and stop after the same $-\log \varepsilon$ time.

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As I said, and as per my reputable links, I see it as a rather logical theoretical application as opposed to your own thoughts.

Classically, black holes are black.
Quantum mechanically, black holes radiate, with a radiation known as Hawking radiation, after the British physicist Stephen Hawking who first proposed it.

The animation at top left cartoons the Hawking radiation from a black hole of the size shown at bottom left. The blobs are supposed to be individual photons. Notice, first, that the photons have sizes' (wavelengths) comparable to the size of the black hole, and, second, that the Hawking radiation is not very bright - the black hole emits roughly one photon every light crossing time of the black hole. So a black hole observed by its Hawking radiation looks fuzzy, a quantum mechanical object.

This is one animation that I did not compute mathematically. How do you draw a quantum mechanical object, whose appearance depends not only on the object but also on the way the observer chooses to observe it? I figured my impressionism was good enough here.

Hawking radiation has a blackbody (Planck) spectrum with a temperature T given by

kT = hbar g / (2 pi c) = hbar c / (4 pi rs)

where k is Boltzmann's constant, hbar = h / (2 pi) is Planck's constant divided by 2 pi, and g = G M / rs2 is the surface gravity at the horizon, the Schwarzschild radiusrs, of the black hole of mass M. Numerically, the Hawking temperature is T= 4 × 10-20g Kelvin if the gravitational acceleration g is measured in Earth gravities (gees).
The Hawking luminosity L of the black hole is given by the usual Stefan-Boltzmann blackbody formula

L = A sigma T4

where A = 4 pi rs2 is the surface area of the black hole, and sigma = pi2k4 / (60 c2 hbar3) is the Stefan-Boltzmann constant. If the Hawking temperature exceeds the rest mass energy of a particle type, then the black hole radiates particles and antiparticles of that type, in addition to photons, and the Hawking luminosity of the black hole rises to
L = A (neff / 2) sigma T4

where neff is the effective number of relativistic particle types, including the two helicity types (polarizations) of the photon.black hole at the centre of the galaxy Messier 87. The Hawking radiation from such black holes is minuscule. The Hawking temperature of a 30 solar mass black hole is a tiny 2×10-9 Kelvin, and its Hawking luminosity a miserable 10-31 Watts. Bigger black holes are colder and dimmer: the Hawking temperature is inversely proportional to the mass, while the Hawking luminosity is inversely proportional to the square of the mass.

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27,534

Hawking radiation mimicked in the lab

Sound waves used to imitate light particles predicted to escape black holes.

Scientists have come closer than ever before to creating a laboratory-scale imitation of a black hole that emits Hawking radiation, the particles predicted to escape black holes due to quantum mechanical effects.

The black hole analogue, reported in Nature Physics1, was created by trapping sound waves using an ultra cold fluid. Such objects could one day help resolve the so-called black hole ‘information paradox’ - the question of whether information that falls into a black hole disappears forever.

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http://www.sciencepubco.com/index.php/ijbas/article/view/607
Abstract:
Given the importance of Hawking radiation in the areas of black holes, we present in this paper an overview about the fuzzy black hole and its thermodynamic properties. We introduce the Hawking radiation of this class of black holes via complex path method and we give the possibility to estimate the evaporation time of the Schwarzschild black hole in fuzzy space

Conclusion:
In this work, we recalled some basic concept of Schwarzschild Black Hole in fuzzy space and their Thermodynamics properties. However, a main goal of this paper is to study the Hawking radiation and the evaporation time estimated of fuzzy Schwarzschild black hole by using the method of complex paths developed in [14].
We have to underline that the relevance of our work can be related also to the importance of the complex paths method.

23. ### SchmelzerValued Senior Member

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Your "reputable link" tells us nothing about this, your third link refers to an abstruse exercise in math of M-theory, that means, highly theoretical speculation, thus, worth to be ignored by everybody except specialists in this particular highly speculative domain.

The theme of your second link is interesting, because it refers to black hole analogons in condensed matter theory. They may, indeed, show an analogon of Hawking radiation. But, of course, only of the part of Hawking radiation which appears during the collapse time. And the even more interesting point is that this analogon has a critical distance, the atomic distance of the condensed matter considered. This defines a cutoff for higher frequencies of sound waves. If this analogon is a really good one, one may expect that it shares also this qualitative property with fundamental physics, so that we would have to expect some critical distance, with a cutoff for higher frequencies. And in this case, there will be definitely no Hawking radiation except for a small time around the collapse.