
Black holes may be brick walls that bounce information back out - bootload
https://www.newscientist.com/article/dn28159-black-holes-may-be-brick-walls-that-bounce-information-back-out/
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PuffinBlue
Basing this on personal hunch instead of any theoretical hard standing
whatsoever I think black holes are really just the event horizon, there's
nothing 'inside' the event horizon.

I believe that the collapse into a 'black hole' 'stops' at the moment that
space-time curvature creates a sphere of space-time that geometrically appears
to us 'outsiders' as the surface of a sphere or a shell - ergo the event
horizon.

That is, I believe that there is _nothing_ inside the event horizon (literally
nothing, no space-time, no anything), the event horizon is just the region of
space-time occupying the surface of a shell inside which there is NOTHING.

I don't believe you fall 'through' the event horizon, I think that the matter
that would otherwise make up the singularity at the centre of the black hole
is smeared over this surface/event-horizon region.

There are problems with this idea, but those are somewhat related to the fact
we believe matter becomes infinitely dense (why wouldn't material on the
surface of the sphere collapse to smaller spheres/event-horizons of their own)
But infinite density is clearly not a 'proven' theory, however widely it's
postulated - so we clearly don't understand if that is even a physical
possibility.

I've not seen anything concrete that says you can't model a black-hole as a
shell of mass. As I understand it, to an outside observer a shell behaves
gravitationally identically to a point mass at the centre of such a shell
would.

Of course, I'm no doubt very wrong, but whenever I've mentioned this to
anyone, no one has really come up with anything to say it absolutely isn't
possible, not without holding on to other things we 'think' we know like
matter 'should' continue to collapse to infinite density once past some
arbitrary point. Something I'm not convinced is true.

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danbruc
A few comments. I doubt that many or even any serious physicist imagine
something of infinite density inside a black hole, infinities are just the way
our theories tell us that we don't understand things well enough and got the
math wrong. The event horizon can be a very ordinary place with almost flat
space and no strong gravitational forces. You can probably cross the event
horizon of a large black hole without even noticing what you just did and that
you are doomed. So imagining that the event horizon is kind of a wall with
nothing behind the wall most likely does not work. Lastly the singularity is
not a place but a time, the common pictures of black holes are highly
inadequate to think about black holes.

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guard-of-terra
Event horizon is an ordinary place that happens to be bombarded by high energy
particles coming from the whole galaxy in great numbers. I think you'll note.

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danbruc
Black holes are not active all the time, after cleaning out the surrounding
space they can go through extended periods in which they are not aggregating
more mass. I am not even sure if you should expect particles with high energy
rushing in. Why not gas clouds with densities of a few atoms per cubic meter
drifting into the black hole with modest velocity? If I remember correctly you
can even be inside the event horizon before the black hole actually formed, I
would definitely not expect high energy particles in such an scenario.

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guard-of-terra
When you approach event horizon you witness the galaxy age and die, and also
get multiple billion year load of heavy particles, possibly even blueshifted
thermal photons.

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danbruc
Nothing special happens when you approach or cross the event horizon. If you
look back, even from inside the event horizon, everything looks normal to you,
at least until you are close enough to the singularity so that the curvature
becomes significant. Only observers outside of the black hole see the event
horizon as a special place. For a pretty accessible introduction including a
discussion of falling into a black hole see for example [1].

[1] [http://theoreticalminimum.com/courses/general-
relativity/201...](http://theoreticalminimum.com/courses/general-
relativity/2012/fall)

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guard-of-terra
It does. Galaxy speeds up and then you witness it age and die. Also harvest
all its decay products in very short period of time.

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Thiz
I've always thought they're not really holes but black spheres that absorb
everything close to them including light.

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lukifer
The thing to remember is that space isn't flat. Gravity warps it, like a
bowling ball warps a flat bed sheet, but in 3 (technically, 4) dimensions. A
black hole is a warping where instead of a gradual dip in the sheet, there is
a cone that plummets down seemingly infinitely. But the principle of
relativity means we don't really know what's on the other side; just that
anything that goes over the edge of the quasi-spheroid line (the event
horizon) can't ever go fast enough to come back.

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Thiz
I like my black sphere theory better, but interesting the similarity with a
cone nonetheless.

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amelius
I've always been told that the laws of physics are reversible, so I don't
think information can be trapped anyway.

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JoeAltmaier
That's precisely the bit that is at issue. The boundary of a black hole seems
to be asymmetric regarding information and the arrow of time. Not reversible,
which would be a new thing.

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SilasX
Stupid question: is this any differen from the "everyday" problem of
information loss? That is, we know phase space is conserved, and yet, if you
burn a piece of paper and mix up the ashes, you can't practically recover what
was written on it.

Is there information loss (per the claim in the dispute) in a stronger sense
for black holes? Is it a case where multiple start states map to the same
final state, or just another case of in-practice irreversibility like in the
burning paper example?

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richmarr
While from a human perspective information seems to be being destroyed, really
it's just being obfuscated beyond our means of recovery.

If you were to pause time, with enough analysis and knowledge of the _present_
state of your burning parchment you could recover the state from a split-
second prior to that.

No-hair theory says that the event horizon of a black hole is different. One
moment the information exists, the next moment it's just gone.

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akiselev
This is a key point: recovery of the information requires some knowledge of
time. If you were handed a pile of ashes (assuming ideal combustion of every
molecule) you have zero chance of recovering any information but if you
watched it burn, you can theoretically recover the initial state.

Thats where the analogy breaks down with black holes: when a singularity
absorbs a particle not only is any information about its identity lost, but
also where it was in time.

If you were to mix a bunch of ashes after watching several different documents
burn you could still recover the initial state of each one but because of the
extreme conditions in a singularity, even this basic axiom of cause and effect
is no longer valid.

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SilasX
So black holes really do shrink phase space, and it's not simply a matter of
it being too computationally expensive to extract out "what went inside it"
given the microstate of the black hole radiation?

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akiselev
Yep. The big unanswered question as far as I know (from a layman's
perspective) is whether the matter/energy in the singularity at the center of
a black hole even follows the laws of nature as we have observe them or if all
of that is out of the window past the event horizon. If you don't know the
laws of nature describing what happens inside (and you can't study them due to
the destructive nature of those forces), no amount of computation will be able
to help.

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guard-of-terra
I find this black hole information debate akin to medieval ramblings on amount
of angels dancing on diamond pin head. Can we please move on a little and come
back when we have new angle?

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mojuba
Exactly. I call it exploitation of the unknown. You can generate lots of
"theories" by just combining a couple of mysterious things into one. For
example, something that hasn't been tried yet afaict, is a theory that black
holes are a gateway between the physical world and human consciousness (or
self-awareness).

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LoSboccacc
Oh i like the what if games.

Black hole (as singularities that may have formed without collapsing stars)
played a central role in early universe by swallowing matter and anti matter
and radiating energy by hawking radiation which then fueled energy decay into
standard matter, and that may explain the current imbalance between matter and
anti matter or it may be mad internet rambling.

Still medium worthy?

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witty_username
Your theory doesn't make much sense. There's really nothing special about
"normal" matter vs antimatter. You could as easily call the matter I'm made of
antimatter and reverse the names and the physics is the same for both.

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lern_too_spel
You've set up a strawman. The GP doesn't claim that there's anything special
about antimatter. He simply provides a wacky explanation for the unsolved
problem of baryon asymmetry.

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Qwertious
The question is: Why would the black holes swallow up more antimatter than
matter, if everything is completely symmetrical?

