
Strangeness of Black Holes - dnetesn
http://nautil.us/issue/68/context/the-strangeness-of-black-holes
======
ithkuil
I found these lectures by Leonard Susskind very insightful:

\- Leonard Susskind on The World As Hologram
([https://www.youtube.com/watch?v=2DIl3Hfh9t](https://www.youtube.com/watch?v=2DIl3Hfh9t))

\- Leonard Susskind | "ER = EPR" or "What's Behind the Horizons of Black
Holes?"
([https://www.youtube.com/watch?v=OBPpRqxY8Uw](https://www.youtube.com/watch?v=OBPpRqxY8Uw))

\- Entanglement and Complexity: Gravity and Quantum Mechanics
([https://www.youtube.com/watch?v=9crggox5rbc](https://www.youtube.com/watch?v=9crggox5rbc))

~~~
consp
As a note to the poster: The first video is not available where I live
(Netherlands), maybe the link is wrong, the others are however.

~~~
arunix
This one works for me (UK):

[https://www.youtube.com/watch?v=2DIl3Hfh9tY](https://www.youtube.com/watch?v=2DIl3Hfh9tY)

(Leonard Susskind on The World As Hologram)

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bawana
I find it strange that no one has characterized that boundary layer where
light orbits the black hole. We know that massive objects distort space and as
a result alter the path of light. At sufficiently close distances, space is so
distorted that 'not even light can escape'. Everyone assumes that light 'falls
into' a black hole. But for light to do that, it would need a velocity greater
than light itself if it is in orbit around the black hole. Thus, any light
that is captured by tangential approach to the black hole and goes into orbit
around the black hole, has to stay in orbit. Any acceleration that is needed
to change the path of light would add to the velocity of light and that should
not be possible.

Over time, the only light that is not absorbed by virtue of collision with the
singularity at the center of the black hole is the light in orbit around it.
This is distinct and different from the light resulting from nuclear fusion of
material in the accretion disc which is just outside.

~~~
l33tman
The perfect orbit geodesic is infinitely thin and therefore unstable due to
quantum mechanics. So even if a photon is injected at the perfect orbit it
would not stay there, it would fall in or eject. Besides, even without
invoking QM, any other matter that actually falls into the hole afterwards
would inflate the event horizon, causing those photons caught in the perfect
orbit to now exist just infinitesimally within the orbit and fall in.

~~~
soVeryTired
Do you need quantum mechanics to see that a photon would fall in or eject?
Presumably a little movement from the black hole would do the trick too.

~~~
Pharmakon
Right, but the QM view tells us that even a perfectly stationary chargeless
black hole in a perfect vacuum alone in a perfectly smooth universe would
_still_ experience fluctuations in its event horizon. Unlike the Classical
view, QM reveals that even in principle there exists a degree of instability
in the horizon.

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dpark
I’ve never understood how infinite time dilation jives with black hole
evaporation:

> _If we take for example the latter observation of unbounded time dilation
> seriously, we come to the conclusion that in the moment that we spend on the
> horizon all time passes for anything outside the black hole. The end of all
> things happens in the rest of the universe, and in fact after the moment in
> which we enter the black hole, there is no way back._

> _However, if we consider a black hole of the same mass, things look rather
> different. As a (partially) quantum object it radiates and evaporates within
> a tiny fraction of a second. All its mass converts into energy, which
> results in an explosion three times stronger than the bomb dropped on
> Hiroshima._

How do these two things mix? A particle experiences asymptotic time dilation
when it crosses the event horizon and the rest of the universe ends in that
moment. Then the black hole evaporates and lo and behold the universe is not
ended.

Yeah, the particle that went in got annihilated and never actually came back
out. Sure. But if the black hole does not survive until the end of the
universe, then it seems fundamentally impossible that the particle in question
experienced unbounded/infinite/asymptotic time dilation. The particle’s
annihilation must have happened by the time the black hole evaporated. And
yes, time is relative, but it doesn’t run in reverse.

~~~
speakeron
> How do these two things mix? A particle experiences asymptotic time dilation
> when it crosses the event horizon and the rest of the universe ends in that
> moment. Then the black hole evaporates and lo and behold the universe is not
> ended.

I don't know if that's necessarily correct. From the point of view of an
object falling through the event horizon, nothing special happens and they can
look outwards normally; whereas an observer some distance from the black hole
(and maintaining that distance) sees the falling object fall slower and slower
and becoming more redshifted. The falling object also become shorter in the
direction of travel (according to the external observer) and end up 'smeared'
on the horizon.

Leonard Susskind shows this using a Penrose diagram in lecture 5 or 6 (I
think, but they're all worth watching) of the Stanford Topics in String Theory
lectures[1]

[1] [https://www.youtube.com/watch?v=NZ-
ElsvYKyo](https://www.youtube.com/watch?v=NZ-ElsvYKyo)

~~~
zwkrt
Suskind actually has a whole lecture on Youtube devoted to addressing the
paradox of falling into a black hole from the perspective of the person
falling in versus an outside observer. The outside observer sees the falling
observer catastrophically turned into high-entropy soup smeared across the
horizon, while the one falling feels nothing particularly special as they
cross the event horizon.

[https://www.youtube.com/watch?v=2DIl3Hfh9tY](https://www.youtube.com/watch?v=2DIl3Hfh9tY)

~~~
Pharmakon
Just a note, that’s the case for a very high mass black hole. A “smaller”
black hole would shred the astronaut before they even reached the event
horizon.

------
dr_dshiv
I'm curious about the description of a black hole as a singularity. I'm going
to resort to Neoplatonist philosophy to try to understand this.

In the formation of the universe, the notion of a singularity points at an old
idea, argued by Plotinus, that everything started with "The One". This is
commensurable with the statement that the boltzmann entropy of the start of
the universe, prior to inflation, would be equal to "1" \-- because that is
the total volume of possible phase space. That, to me, is very elegant --
although it is unclear whether there are predictions about how the 1 becomes 2
("the indefinite dyad"), 3 and then the inflationary myriad. But still, I'm
impressed that the logic of ancient philosophy could correspond reasonably
with modern physics.

From this perspective, I'm interpreting big bang's "singularity" as =1. What
is the nature of the singularity of a blackhole? Is the event horizon itself
the singularity, or does it just an effect of a singularity at the center of
the blackhole? Is there a "One" at the center of the blackhole?

~~~
whatshisface
If one doesn't understand a scientific theory then their understanding of it
contains no information. Ancient philosophy rarely contains information. As a
result the two often appear to line up.

~~~
yesenadam
>Ancient philosophy rarely contains information.

Sounds like you haven't read much, gee. What a strange comment. It has a far
higher signal/noise ratio than modern philosophy, I'd say, maybe because
usually only the best has survived.

~~~
whatshisface
> _It has a far higher signal /noise ratio than modern philosophy_

You can look at it this way: every possible statement seems to have been made
by at least one ancient philosopher, especially once you include the non-
western traditions. There were atom-ists, and continuum-ists, and so on. If
you view ancient philosophy as one big bucket of sentences, it will fill up
sentence space fairly uniformly. You could reconstruct ancient philosophy just
by coming up with reasonable-sounding claims about things they were aware of
back then until you ran out of possibilities, although that wouldn't produce
the historical association of certain views with certain people.

A distribution that uniformly fills space is, in the technical sense of the
word, "no information." If you trim it down (for example by doing experiments
and discarding whatever doesn't match your newfound knowledge of reality), you
get a distribution that "has information."

To put it concretely, finding out that an ancient philosopher said something
doesn't help, because ancient philosophers said everything they could think
of. Whether that is better or worse than what philosophers are doing now is up
to philosophers to decide, I guess.

~~~
teolandon
I haven't actually taken every single statement said by ancient philosophers
(if you can even clearly classify philosophers as 'ancient' \-- what's the
date cutoff?), and put them in a bucket, and checked that the sentence space
in that bucket is filled up uniformly.

However, new sentences are made every day, new words made very often. Nobody
cares about the technical sense of the words "no information". If your
argument was extended from 'ancient philosophy' to 'anything ever said by
humans', then anything ever said by humans would fill the sentence space
fairly uniformly, so finding out that anyone has said anything doesn't help.

A single human has not considered and thought about every sentence possible.
They have their own beliefs and knowledges, and by reading ancient philosophy,
they can expand that knowledge base, change those beliefs. Ancient philosophy
is not inconsequential, and it certainly contains "information".

~~~
dpark
I think whatshisface is being overly dismissive of the value/information in
ancient philosophy. But the heart of his comment is that you can cherry pick
pretty much whatever you want from ancient philosophy because the corpus is so
large. If you, e.g., selectively choose statements that vaguely line up with
quantum mechanics, you haven’t proven that Ancient Greeks knew quantum
mechanics or had some unexpectedly deep understanding of the universe. You did
something equivalent to P-hacking to dig meaningless correlations out of the
noise.

~~~
dr_dshiv
Right, it would be inappropriate to claim that Plato predicted the big bang!

He did arguably explicitly predict that basic mathematical/geometric forms
underlie the structure of the universe. E.g., that atoms would be composed of
pyramids, cubes, dodecahedrons and that the behaviour of atoms would be based
upon the different geometric properties of basic forms.

That idea is only partially correct, however. Atoms are based on the basic
mathematical forms -- but on the spherical harmonics of electron clouds, not
point geometries. Whoops! Otherwise, the idea is commensurable with modern
atomic understanding.

Earth, water, air and fire correspond not to elements (ice can melt,
obviously) but to phases of matter. (Solid, liquid, gas, plasma).

There is a reason Classical Greek philosophy underlies western civilization.
They were not dummies and there is still a lot we can learn from them. It's
not like all their ideas were examined in the 1800s and we took all the good
ones, leaving the classics as a sort of intellectual skin worth shedding.
Instead, it is the core we build on. It's worth understanding the core -- and
giving them the benefit of the doubt to identify interesting ideas.

Like that the universe begins with "the one" :)

~~~
dpark
That is some impressively hand-wavy equivalency. Plato predicted something
pretty much entirely wrong and you're pretending he was generally correct.
Plato believed, without evidence, that there were some indivisible units of
matter. That's all he got right (and even that was arguably incorrect given
subatomic particles).

