
Black hole paradoxes reveal a fundamental link between energy and order - nnx
https://www.quantamagazine.org/black-hole-paradoxes-reveal-a-fundamental-link-between-energy-and-order-20200528/
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at_a_remove
Here's the one that has bugged me since I first learned of Hawking radiation
as an undergrad: if it is true (it's still unobserved but let's go with it),
that means that merely passing through the event horizon allows for violation
of the conservation of baryon number.

I generally regard most of the "Star Trek physics" ideas like FTL with the
hairy eyeball, but this one really gets me. Being able to violate the
conservation of baryon number (and lepton number, for that matter) would point
to -- in some scenarios -- mass-energy conversion being a lot more available
than the laborious processes of fission, fusion, and particle/antiparticle
mutual annihilation.

~~~
simonh
Surely the conservation of baryon numbers is just a rule for reactions. I
don’t see how crossing the event horizon changes anything. Remember from the
POV of the baryon, it never crosses the event horizon. It’s not really
‘destroyed’, it just becomes unobservable to the external universe.

~~~
danbruc
_Remember from the POV of the baryon, it never crosses the event horizon. It’s
not really ‘destroyed’, it just becomes unobservable to the external
universe._

I think this is backwards - for an outside observer nothing ever crosses the
event horizon, from the point of view of anything falling towards the event
horizon it takes a finite amount of time to cross the event horizon.

~~~
heavenlyblue
How does this interact with the Hawking radiation? ie I throw something into
the black hole, how much time do I wait before the Hawking radiation from that
matter to manifest itself?

~~~
danbruc
From your point of view - assuming you do not fall into the black hole
yourself - nothing you throw into the black hole ever crosses the event
horizon so you will have wait forever. You can only see something cross the
event horizon if you cross the event horizon yourself and you will see
everything cross the event horizon at the moment you cross the event horizon.

~~~
coffeeling
My friend is kind of confused. Why wouldn't an observer outside of the event
horizon see things falling into it? He says you can glean information from a
thing that's outside of the horizon, but a thing falling into it should cease
to be observable, at least by his understanding of black holes. My galaxy-
sized brain understands this, of course, but my friend's pea-brain doesn't.

So asking for a friend, ELI-aborted-CS-degree?

~~~
danbruc
An observer outside the event horizon has to accelerate to avoid falling into
the black hole itself and in the resulting frame of reference of this observer
the horizon of the black hole coincides with future infinity and therefore
everything falling into the black hole only reaches the event horizon
infinitely far into the future. You can watch Leonard Suskind's lecture on
that [1], falling into a black hole starts at about 53 minutes, but depending
on your background you may want to start earlier, maybe even several lectures
earlier. Looking at those Penrose diagrams is probably the easiest way to see
what happens even if it will probably still not make intuitive sense.

[1]
[https://www.youtube.com/watch?v=BdYtfYkdGDk&list=PLpGHT1n4-m...](https://www.youtube.com/watch?v=BdYtfYkdGDk&list=PLpGHT1n4-mAvcXwzOIz3dHnGZaQP1LEib&index=4)

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pierrebai
As a true amateur,I don't understand the basic premise of this extremal black
hole mystery.

In my simple view, if a charged black whole is extremal and cannot shrink
then... the solution simply is that it must grow again. It absorbs particles
of the opposite charge until it becomes neutral enough to shrink again and the
process repeat until it completely evaporate.

That seems both a simple and straightforward theory.

(Then my other misunderstanding is how a black whole would become so charged
when the universe is seemingly so neutral. The law of big number ensures that
a black hole would be mostly neutral and the extremal case would only happen
for very small ones on the brink of evaporation.)

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mormegil
> In that case, the universe of the far future will be littered with tiny,
> indestructible black hole remnants — the remains of any black holes that
> carry even a touch of charge

I don't get that. Wouldn't the charge be neutralized by consuming particles
with an opposite charge (which are attracted gravitationally _and_
electrically)? Or even by merging two extremal black holes with opposite
charge?

~~~
hellofunk
I think if you read the article, they talk about this far future hypothesis.

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andrewflnr
I remember reading somewhere that charged black holes would quickly lose their
charge by radiating charged particles rather than, I guess, purely neutral
photons. I've been taking that for granted for a while now, but don't remember
exactly where I read it. Does anyone know where that hypothesis comes from and
how it relates to the work in article?

~~~
qubex
I think the prevailing notion is another, namely that an electrically charged
black hole would quickly neutralise by preferentially attracting particles of
opposite charge.

~~~
AnimalMuppet
In particular, if a charged black hole creates Hawking pairs, the oppositely-
charged particle is more likely to be captured than the same-charge particle.

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zzv
What a ridiculously well-written article!

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peter_d_sherman
>"Plumbing black holes for knowledge of quantum gravity originated with
Stephen Hawking. In 1974, the British physicist calculated that quantum jitter
at the surfaces of black holes cause them to evaporate, slowly shrinking as
they radiate heat."

If heat is related to a black hole shrinking, and a black hole shrinking is
related to information, then perhaps _heat_ is related to _information_ , and
vice-versa.

[...]

>"In that case, the universe of the far future will be littered with tiny,
indestructible black hole remnants — the remains of any black holes that carry
even a touch of charge..."

You mean like an atom? Perhaps atoms (and other particles, in fact, _all other
particles_ ) are really just black holes! Perhaps _curved space_ is a better
way to look at it... perhaps all black holes (and all particles) are really
just _curved space_... in fact, perhaps all waves are _curved space_ too...

Which would mean that everything in the universe, all of its particles, all of
its waves, all of its contents, including the universe itself... is basically
_curved space_... in one form or another...

[...]

>"In a paper published in March in Physical Review Letters, [Garrett] Goon and
Riccardo Penco broadened the lessons of the earlier work by proving a simple,
universal formula relating energy and entropy. The newfound formula applies to
a system such as a gas as well as a black hole."

If gases (particulate matter spread thinly in a thinner medium, i.e., space)
can be related to black holes, then black holes can be related to the
particles in the gases, which lends additional credence to the idea that all
atoms are black holes, although, this being said, it's not a hard proof...

[...]

>"When they combine Einstein’s gravity equations and the equations of
electromagnetism, they calculate that a black hole’s charge, Q, can never
surpass its mass, M, when both are converted into the same fundamental units.
Together, the black hole’s mass and charge determine its size — the radius of
the event horizon. _Meanwhile, the black hole’s charge also creates a second,
“inner” horizon, hidden behind the event horizon._ "

Super weird idea here... if we thought about a black hole of whatever size
holographically, as information, then what would be true if the inner, hidden
part of the black hole actually contained a miniature replica, a miniature
mirror-image -- of ALL of the information inside this universe, a universe-
inside-of-a-universe? That's highly speculative of course, but I think it's an
idea worth exploring...

[...]

">When a black hole hits this point, a simple option for further decay would
be to split into two smaller black holes."

You mean like + and - on a battery terminal?

Let me go for "full crackpot theorist" <g>...

What if charge, as we know it, in electricity, is implemented by various
clusters of small black holes, regions of curved space, that we have (up until
this point in time) been calling by such names as "charge", "electron",
"electricity", "potential", "potential difference", etc.

When, what you've got might be multiple black holes, split into pairs, where
one is a complex conjugate, a mirror image of the other, and they basically
want to unify and annihilate, producing various wavelengths (heat/information)
in the process?

All physics should be solvable once the correct identities are established
between apparently dissimilar phenomena...

~~~
jiggawatts
[https://en.wikipedia.org/wiki/Black_hole_electron](https://en.wikipedia.org/wiki/Black_hole_electron)

My line of thought has been similar: If all mass/energy curves space time,
then by extension all particles curve space time in proportion to their mass.
You can't have only planets and stars curving the fabric of spacetime, it has
to be the individual particles that make them up, because duh: if you split a
planet in two, each half will keep half the mass and hence half the
curvature.[1] You can repeat this all the way down to atoms, nucleons, and
electrons. Probably photons, quarks, and neutrinos too.

But that's not how anything works in field theory, QED, etc... they just
assume that there's a locally flat background with some "stuff on top" that
doesn't distort the background at all. Like a function above the number line.

The key insight is that whatever makes particle curve spacetime must be some
inherent, fundamental aspect of their nature. Not an extra "m" attribute that
can be anything. That's why rest masses of all particles are consistent, their
mass -- their curvature in spacetime -- is the very essence of their nature.

My current best hunch is that particles are like knots or tangles in the
fabric of spacetime, inherently curving it. _All information_ is encoded as
curvature, and curvature is the only thing that truly exists. In this model,
black holes are regions of maximum curvature, vaguely like a ball of yarn. If
you want to add one extra "strand" going into the ball of yarn, its cross-
section has to be added to the surface area of the black hole, which is why
black hole area is proportional to its matter content, not its volume.

1] Not _quite_ though! There is the gravitational binding energy. You have to
put energy into a planet to split it up into separate particles, and
conversely, planets release energy by the mere act of their forming. Jupiter
releases more energy from its interior due to gravitational contraction that
it receives from the Sun. In effect, particles are _heavier_ separately than
together.

~~~
Eyght
The idea of particles like knots in the fabric of space has been around for a
long time.

[https://en.wikipedia.org/wiki/Vortex_theory_of_the_atom](https://en.wikipedia.org/wiki/Vortex_theory_of_the_atom)

~~~
jiggawatts
That was a fascinating rabbit hole to go down!

I especially liked this alternate model:
[http://kennethsnelson.net/PortraitOfAnAtom.pdf](http://kennethsnelson.net/PortraitOfAnAtom.pdf)

I don't know if anyone had ever bothered to develop it further, or even
critique it, but it's interesting how many qualitative phenomena it explains
in a straightforward, intuitive way!

