Black Holes Arent Black After All?
FYI -- It sounds like physicists are starting to utilize the Sherlock Holmes principle: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth". Apparently, quantum destruction of information is even more unpalatable than the non-existence of black holes, so perhaps black holes don't exist after all. https://medium.com/the-physics-arxiv-blog/d0758c7c88b5 Black Holes ArenÂt Black After All, Say Theoretical Physicists Collapsed stars are just too big to trap light forever Black holes are a crucial part of the great cultural legacy of EinsteinÂs theory of general relativity. They have fascinated scientists and laypeople alike since they entered the public consciousness in the latter half of the 20th century. But it may be time to say goodbye to the notion of regions of space so dense that even light becomes trapped within them. In the last year or so, an intense debate about the paradoxical properties of black holes has left a number of theoretical physicists, including Stephen Hawking, suggesting that black holes might not exist at all, at least not in the form that anyone had imagined. If theyÂre right, it may finally be time to say goodbye to one of the most exotic objects in the theoretical universe. The black hole may finally be dead. First some background. Stars form when matter becomes dense enough to generate a gravitational field that compresses matter to the point where atoms fuse and release energy. This energy release prevents further collapseÂthroughout a starÂs lifetime, its gravitational collapse is balanced by its thermal expansion. Theoretical physicists have long predicted that black holes form when massive stars stop producing energy at the end of their lives. When that happens, thermal forces cease and the gravitational collapse takes over. If the star is relatively small, like the sun, the gravitational forces are not strong enough to overcome the force between neutrons and this stops the collapse forming a neutron star. But when much larger stars end their lives, there is no known force that can stop the collapse. Consequently, theoretical physicists have always assumed that the collapse must continue until the star becomes infinitely dense and forms a singularity in the fabric of space-time. The gravitational field around such a star would be so intense that not even light can escape. Hence the name Âblack holeÂ. ThatÂs never been an entirely satisfactory approach. Many physicists scratch their feet and stare at the ground when confronted with the idea of an infinitely dense object. WhatÂs more, the mechanism of collapse does not take into account quantum gravity, a theory that that is not yet fully understood in such extreme conditions. ItÂs quite possible that a better understanding of quantum gravity could point to an entirely different result. Indeed, thatÂs exactly what appears to be happening. In the last few years, theoretical physicists have begun to think about what happens to information when it falls into a black hole. The general feeling is that information cannot be destroyed in this process and yet thatÂs exactly what seems to happen. Information is ultimately carried by quantum particles such as photons. So at issue here is the nature of quantum mechanics. A fundamental postulate of quantum theory is that all the information about a system is encoded in its wave function and this always evolves in a way that conserves quantum information. But the quantum information associated with matter that enters a black hole seems to devolve into a single state. When that happens, the information must be lost. This information paradox has triggered some intense soul-searching. And as a result of this, Stephen Hawking proposed a potential solution earlier this year. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it. Today, Cenalo Vaz at the University of Cincinnati takes this idea and runs with it. The question he tackles is this: if a dead star does not collapse beyond the event horizon and so does not produce a black hole, what does it end up like? To find out, he models the quantum behaviour of dust as it collapses towards the event horizon. ÂIn this simple model, the picture that emerges is very different from the traditional view of a black hole, says Vaz. In this new model, there are two important parameters. The first is the so-called Schwarzschild radius, which is the size of the black hole that would form in a conventional model. The second is the radius of the dust ball as measured by distant observer. The difference between these radii is a region in which the universe is unlike anything physicists have imagined. The total energy here is negative and quantum fluctuations are likely to dominate. But exactly what goes on will depend on the exact model of quantum gravity that turns out to be correct, something that physicists are some way from determining. By contrast, the behaviour outside this region is strangely conventional, says Vaz. The collapsed star should swelled to about twice the radius of a conventional black hole. There is no event horizon and the space-time geometry is regular. ÂObservationally, what is being encountered has more in common with a neutron star, except that what holds the system up is not matter degeneracy pressure but vacuum energy, says Vaz. ThatÂs a fascinating conclusion. WhatÂs interesting here is that there is plenty of observational evidence that highly dense objects exist in the universe, some of them on a supermassive scale. For example, the supermassive black hole, or something like it, that sits at the very centre of the Milky Way galaxy. Vaz isnÂt disputing the existence of these superdense objects, just what they look like. What he and others are saying is that these objects are not black at all. Indeed, it should be possible to observe them, just like ordinary neutron stars. The difficulty, of course, will be to distinguish them from traditional neutron stars. If Vaz and co are right, astronomers are set to have some fun hunting for these exotic objects. Time to get looking. Ref: arxiv.org/abs/1407.3823 : ThereÂs Nothing ÂBlack about a Black Hole http://arxiv.org/abs/1407.3823
Very interesting, and I hadn't yet seen that result. Around three years ago, a Reddit user, RobotRollCall, posted many excellent answers to /r/AskScience. He (or she) said this about black holes: "...as long as there's no flux through the boundary, a volume of space can be fully described by treating it as just a surface with no interior. You can then take the next step and say that all of the information — which has a specific meaning here, basically referring to everything that's conserved, like energy-momentum and charge and baryon number and so forth — exists not on the interior of the volume, but rather on its surface. The volume of space, taken as a whole and viewed from the outside, acts like it's just a surface, with conserved quantities "painted" on its surface. ... A black hole is, in fact, just such a volume. It has a well-defined surface: the event horizon. It's spherically symmetric. Its interior is uniform. And there is no flux whatsoever through its boundary, because of exactly the reason you noted. So it turns out that quirky mathematical abstraction really can be applied to black holes in a way that isn't just approximate. And in fact, when you work through it, it turns out to have profound physical significance. You can think of black-hole formation this way: At the instant the event horizon forms — and it really is an instant; it happens all at once, over zero time in all reference frames — the interior of the black hole completely ceases to exist, and is replaced by a pure surface, which contains within it all the information — all the conserved quantities, in other words — that were present in the spherical volume of space the boundary of which became the event horizon.
From that point on, there's no place in your equations to put any of the stuff that went into making the black hole. It literally doesn't exist any more. All of its mass, all of its momentum, all of its charge, all of its entropy is now the substance of the black hole's event horizon. Forever after, only the event horizon itself interacts with the universe, and that interaction can be described by a unitary S-matrix. Everything that should be conserved is conserved, no magic happens, nothing vanishes from the universe or appears out of nothing. For the time that the black hole exists — which may or may not be finite, depending on what the scale factor of the universe does in the future — everything that happens around it is determined exclusively by the properties of the event horizon itself.
Black holes, in other words, have no insides. They're surfaces with no interiors." and "Because our understanding of black holes has evolved a lot over the past twenty years or so. Basically everything that was believed to be true about them last century turns out either to be false, or to be much more nuanced and interesting than anyone ever suspected. The best way to think about black holes (and I keep revising this little speech as I test it out on undergraduates) is not so much as objects so much as processes. The interaction of matter and energy with a black hole can be described, mathematically, as a scattering process. Absolutely no different than the type of scattering that happens when a photon meets an atomic nucleus. Stuff goes into the interaction, and stuff comes out of the interaction, and what predicts the outs from the ins is something called a scattering matrix. What makes black holes special, though, is the extent to which time is distorted around them. From the point of view of a distant observer — that's you and me — time near the event horizon is dilated to such an extent that it very nearly stops altogether. Because of this, the scattering process that happens around a black hole takes, instead of an amount of time so short as to basically be zero, countless trillions of years. So what's actually happening to the stuff that "falls in" to a black hole is that it's scattering. Right now, it's scattering. But time is so dilated around the black hole that in our frame of reference the process takes, almost literally, forever. So long story short, everything that "falls in" to a black hole scatters off of the event horizon. But no one will be alive to see it." It's interesting that those ideas appear to have stuck, evolving into the results of the paper Henry quoted. Jeff On Thu, Jul 24, 2014 at 3:00 PM, Henry Baker <hbaker1@pipeline.com> wrote: ...
Information is ultimately carried by quantum particles such as photons. So at issue here is the nature of quantum mechanics. A fundamental postulate of quantum theory is that all the information about a system is encoded in its wave function and this always evolves in a way that conserves quantum information.
But the quantum information associated with matter that enters a black hole seems to devolve into a single state. When that happens, the information must be lost.
This information paradox has triggered some intense soul-searching. And as a result of this, Stephen Hawking proposed a potential solution earlier this year. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it.
Today, Cenalo Vaz at the University of Cincinnati takes this idea and runs with it. The question he tackles is this: if a dead star does not collapse beyond the event horizon and so does not produce a black hole, what does it end up like?
To find out, he models the quantum behaviour of dust as it collapses towards the event horizon. “In this simple model, the picture that emerges is very different from the traditional view of a black hole,” says Vaz.
In this new model, there are two important parameters. The first is the so-called Schwarzschild radius, which is the size of the black hole that would form in a conventional model. The second is the radius of the dust ball as measured by distant observer.
The difference between these radii is a region in which the universe is unlike anything physicists have imagined. The total energy here is negative and quantum fluctuations are likely to dominate. But exactly what goes on will depend on the exact model of quantum gravity that turns out to be correct, something that physicists are some way from determining.
In this hypothesis, what happens to an observer who falls into a black hole? Standard general relativity says the observer continues to exist after entering the event horizon. -- Gene
________________________________ From: Jeff Caldwell <jeffrey.d.caldwell@gmail.com> To: math-fun <math-fun@mailman.xmission.com> Sent: Thursday, July 24, 2014 2:48 PM Subject: Re: [math-fun] Black Holes Aren’t Black After All?
Very interesting, and I hadn't yet seen that result.
Around three years ago, a Reddit user, RobotRollCall, posted many excellent answers to /r/AskScience. He (or she) said this about black holes:
"...as long as there's no flux through the boundary, a volume of space can be fully described by treating it as just a surface with no interior.
You can then take the next step and say that all of the information — which has a specific meaning here, basically referring to everything that's conserved, like energy-momentum and charge and baryon number and so forth — exists not on the interior of the volume, but rather on its surface. The volume of space, taken as a whole and viewed from the outside, acts like it's just a surface, with conserved quantities "painted" on its surface. ...
A black hole is, in fact, just such a volume. It has a well-defined surface: the event horizon. It's spherically symmetric. Its interior is uniform. And there is no flux whatsoever through its boundary, because of exactly the reason you noted.
So it turns out that quirky mathematical abstraction really can be applied to black holes in a way that isn't just approximate. And in fact, when you work through it, it turns out to have profound physical significance.
You can think of black-hole formation this way: At the instant the event horizon forms — and it really is an instant; it happens all at once, over zero time in all reference frames — the interior of the black hole completely ceases to exist, and is replaced by a pure surface, which contains within it all the information — all the conserved quantities, in other words — that were present in the spherical volume of space the boundary of which became the event horizon.
From that point on, there's no place in your equations to put any of the stuff that went into making the black hole. It literally doesn't exist any more. All of its mass, all of its momentum, all of its charge, all of its entropy is now the substance of the black hole's event horizon. Forever after, only the event horizon itself interacts with the universe, and that interaction can be described by a unitary S-matrix. Everything that should be conserved is conserved, no magic happens, nothing vanishes from the universe or appears out of nothing. For the time that the black hole exists — which may or may not be finite, depending on what the scale factor of the universe does in the future — everything that happens around it is determined exclusively by the properties of the event horizon itself.
Black holes, in other words, have no insides. They're surfaces with no interiors."
and
"Because our understanding of black holes has evolved a lot over the past twenty years or so. Basically everything that was believed to be true about them last century turns out either to be false, or to be much more nuanced and interesting than anyone ever suspected.
The best way to think about black holes (and I keep revising this little speech as I test it out on undergraduates) is not so much as objects so much as processes.
The interaction of matter and energy with a black hole can be described, mathematically, as a scattering process. Absolutely no different than the type of scattering that happens when a photon meets an atomic nucleus. Stuff goes into the interaction, and stuff comes out of the interaction, and what predicts the outs from the ins is something called a scattering matrix.
What makes black holes special, though, is the extent to which time is distorted around them. From the point of view of a distant observer — that's you and me — time near the event horizon is dilated to such an extent that it very nearly stops altogether. Because of this, the scattering process that happens around a black hole takes, instead of an amount of time so short as to basically be zero, countless trillions of years.
So what's actually happening to the stuff that "falls in" to a black hole is that it's scattering. Right now, it's scattering. But time is so dilated around the black hole that in our frame of reference the process takes, almost literally, forever.
So long story short, everything that "falls in" to a black hole scatters off of the event horizon. But no one will be alive to see it."
It's interesting that those ideas appear to have stuck, evolving into the results of the paper Henry quoted.
Jeff
On Thu, Jul 24, 2014 at 3:00 PM, Henry Baker <hbaker1@pipeline.com> wrote:
...
Information is ultimately carried by quantum particles such as photons. So at issue here is the nature of quantum mechanics. A fundamental postulate of quantum theory is that all the information about a system is encoded in its wave function and this always evolves in a way that conserves quantum information.
But the quantum information associated with matter that enters a black hole seems to devolve into a single state. When that happens, the information must be lost.
This information paradox has triggered some intense soul-searching. And as a result of this, Stephen Hawking proposed a potential solution earlier this year. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it.
Today, Cenalo Vaz at the University of Cincinnati takes this idea and runs with it. The question he tackles is this: if a dead star does not collapse beyond the event horizon and so does not produce a black hole, what does it end up like?
To find out, he models the quantum behaviour of dust as it collapses towards the event horizon. “In this simple model, the picture that emerges is very different from the traditional view of a black hole,” says Vaz.
In this new model, there are two important parameters. The first is the so-called Schwarzschild radius, which is the size of the black hole that would form in a conventional model. The second is the radius of the dust ball as measured by distant observer.
The difference between these radii is a region in which the universe is unlike anything physicists have imagined. The total energy here is negative and quantum fluctuations are likely to dominate. But exactly what goes on will depend on the exact model of quantum gravity that turns out to be correct, something that physicists are some way from determining.
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My understanding of RobotRollCall's explanation is that nothing falls past the event horizon, once it has formed. An observer falls toward the horizon. Gravity distorts time in a dramatic fashion. Outside observers see the falling observer in normal time, appearing to fall through the horizon. The falling observer experiences normal time and scatters off the event horizon. After scattering, the falling observer finds that trillions of years have passed in the "outside world", due to the extreme time distortion. No information is lost, it is scattered eventually, albeit in normal time as seen by the falling observer. I can find his original posts if they are of interest. A similar, but seemingly newer, view is expressed in the article Henry posted: "Stephen Hawking proposed a potential solution earlier this year. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it."" On Thu, Jul 24, 2014 at 6:17 PM, Eugene Salamin via math-fun <math-fun@mailman.xmission.com> wrote:
In this hypothesis, what happens to an observer who falls into a black hole? Standard general relativity says the observer continues to exist after entering the event horizon.
-- Gene
________________________________ From: Jeff Caldwell <jeffrey.d.caldwell@gmail.com> To: math-fun <math-fun@mailman.xmission.com> Sent: Thursday, July 24, 2014 2:48 PM Subject: Re: [math-fun] Black Holes Aren’t Black After All?
Very interesting, and I hadn't yet seen that result.
Around three years ago, a Reddit user, RobotRollCall, posted many excellent answers to /r/AskScience. He (or she) said this about black holes:
"...as long as there's no flux through the boundary, a volume of space can be fully described by treating it as just a surface with no interior.
You can then take the next step and say that all of the information — which has a specific meaning here, basically referring to everything that's conserved, like energy-momentum and charge and baryon number and so forth — exists not on the interior of the volume, but rather on its surface. The volume of space, taken as a whole and viewed from the outside, acts like it's just a surface, with conserved quantities "painted" on its surface. ...
A black hole is, in fact, just such a volume. It has a well-defined surface: the event horizon. It's spherically symmetric. Its interior is uniform. And there is no flux whatsoever through its boundary, because of exactly the reason you noted.
So it turns out that quirky mathematical abstraction really can be applied to black holes in a way that isn't just approximate. And in fact, when you work through it, it turns out to have profound physical significance.
You can think of black-hole formation this way: At the instant the event horizon forms — and it really is an instant; it happens all at once, over zero time in all reference frames — the interior of the black hole completely ceases to exist, and is replaced by a pure surface, which contains within it all the information — all the conserved quantities, in other words — that were present in the spherical volume of space the boundary of which became the event horizon.
From that point on, there's no place in your equations to put any of the stuff that went into making the black hole. It literally doesn't exist any more. All of its mass, all of its momentum, all of its charge, all of its entropy is now the substance of the black hole's event horizon. Forever after, only the event horizon itself interacts with the universe, and that interaction can be described by a unitary S-matrix. Everything that should be conserved is conserved, no magic happens, nothing vanishes from the universe or appears out of nothing. For the time that the black hole exists — which may or may not be finite, depending on what the scale factor of the universe does in the future — everything that happens around it is determined exclusively by the properties of the event horizon itself.
Black holes, in other words, have no insides. They're surfaces with no interiors."
and
"Because our understanding of black holes has evolved a lot over the past twenty years or so. Basically everything that was believed to be true about them last century turns out either to be false, or to be much more nuanced and interesting than anyone ever suspected.
The best way to think about black holes (and I keep revising this little speech as I test it out on undergraduates) is not so much as objects so much as processes.
The interaction of matter and energy with a black hole can be described, mathematically, as a scattering process. Absolutely no different than the type of scattering that happens when a photon meets an atomic nucleus. Stuff goes into the interaction, and stuff comes out of the interaction, and what predicts the outs from the ins is something called a scattering matrix.
What makes black holes special, though, is the extent to which time is distorted around them. From the point of view of a distant observer — that's you and me — time near the event horizon is dilated to such an extent that it very nearly stops altogether. Because of this, the scattering process that happens around a black hole takes, instead of an amount of time so short as to basically be zero, countless trillions of years.
So what's actually happening to the stuff that "falls in" to a black hole is that it's scattering. Right now, it's scattering. But time is so dilated around the black hole that in our frame of reference the process takes, almost literally, forever.
So long story short, everything that "falls in" to a black hole scatters off of the event horizon. But no one will be alive to see it."
It's interesting that those ideas appear to have stuck, evolving into the results of the paper Henry quoted.
Jeff
On Thu, Jul 24, 2014 at 3:00 PM, Henry Baker <hbaker1@pipeline.com> wrote:
...
Information is ultimately carried by quantum particles such as photons. So at issue here is the nature of quantum mechanics. A fundamental postulate of quantum theory is that all the information about a system is encoded in its wave function and this always evolves in a way that conserves quantum information.
But the quantum information associated with matter that enters a black hole seems to devolve into a single state. When that happens, the information must be lost.
This information paradox has triggered some intense soul-searching. And as a result of this, Stephen Hawking proposed a potential solution earlier this year. His idea is that gravitational collapse can never continue beyond the so-called event horizon of a black hole beyond which information is lost. Gravitational collapse would approach the boundary but never go beyond it.
Today, Cenalo Vaz at the University of Cincinnati takes this idea and runs with it. The question he tackles is this: if a dead star does not collapse beyond the event horizon and so does not produce a black hole, what does it end up like?
To find out, he models the quantum behaviour of dust as it collapses towards the event horizon. “In this simple model, the picture that emerges is very different from the traditional view of a black hole,” says Vaz.
In this new model, there are two important parameters. The first is the so-called Schwarzschild radius, which is the size of the black hole that would form in a conventional model. The second is the radius of the dust ball as measured by distant observer.
The difference between these radii is a region in which the universe is unlike anything physicists have imagined. The total energy here is negative and quantum fluctuations are likely to dominate. But exactly what goes on will depend on the exact model of quantum gravity that turns out to be correct, something that physicists are some way from determining.
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participants (3)
-
Eugene Salamin -
Henry Baker -
Jeff Caldwell