
Are We Wrong About Black Holes? - theafh
https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/
======
gus_massa
> _If a black hole is obeying thermodynamic laws, we can presume that a
> statistical description of all its fundamental, indivisible parts can be
> made._

No. It is posible to define the entropy of an object that has no internal
indivisible parts, for example a black hole.

> _Here’s another way in which the analogy falls flat. Black hole entropy is
> given by the black hole area. Well, area is length squared, volume is length
> cubed. So what do we make of all those thermodynamic relations that include
> volume, like Boyle’s law? Is volume, which is length times area, really
> length times entropy? That would ruin the analogy. So we have to say that
> volume is not the counterpart of volume, which is surprising._

This paragraph makes no sense at all. No sense at all!

First, Boyle's law is a law for ideal gases (that can be applied somewhat
correctly to real gases). It can't be applied to solids, it can't be applied
to liquids, it can't be applied to a photon gas, it can't be applied to black
holes. Trying to apply it to black holes shows a completely lack of
understanding of the subject.

In particular:

> _Is volume, which is length times area, really length times entropy?_

What? First the entropy of a black hole is not equal to the area, it's only
proportional to the area, there are some constants. (I had to look up S = A *
c^3 / 4Għ.) Second, you can't pick any three length [1] and multiply them and
expect that the result that has the units of a volume can be used in any
formula you want.

[1] For example, the height of the Eiffel tower, the atomic radio of an iron
atom in the Eiffel tower and the width of the door of the elevator of the
Eiffel tower. You can multiply them and get a volume, but this volume doesn't
follow the Boyle's law when the atmospheric pressure changes in Paris.

~~~
reallydude
> No. It is posible to define the entropy of an object that has no internal
> indivisible parts, for example a black hole

How? If there is no system of parts, there is no entropy. I'm not sure why you
have a "black hole" as an example, when you talk about the entropy of a black
hole afterward and it's has not been concluded that black holes violate the
second law. You have failed to give an example and I think it's important to
at least clarify your statement.

> First, Boyle's law is a law for ideal gases (that can be applied somewhat
> correctly to real gases). It can't be applied to solids, it can't be applied
> to liquids, it can't be applied to a photon gas, it can't be applied to
> black holes.

He didn't say that Boyle's law applied to black holes. He was expounding on
the initial point you objected on. If you have a system of parts, it has a
volume.

> Trying to apply it to black holes shows a completely lack of understanding
> of the subject.

You're being disingenuous by not even attempting to understand the assertion
and then attacking every logical conclusion as if that means something. He has
an understanding, even if you think it's wrong.

> Is volume, which is length times area, really length times entropy?

To your first point, it's semantics when you drop the constants. This isn't
some obscure way of speaking and he uses it generously.

To your second point, he didn't.

This was a generalization of the concept expanded to how you calculate the
event horizon of a black hole. A sphere's surface area can be calculated from
the length of the radius (ie A=4πr2).

(from google) S/V = 3/R 4πr2/Volume = 3/r or Area/3/radius = Volume

So the interpretation is volume = Area x 1/length or Area x Length (ie radius)
when dealing with the variants.

A x c^3 / 4Għ = Entropy (Bekenstein–Hawking formula) and dropping all the
invariants (A = E) we get Area = Entropy So the volume of a black hole (given
it has entropy) could be the volume of the black hole (Area x Length) =
Entropy and since we can get area from Length, we can drop the invariants and
we get Length = Entropy with constants and invariant proportions.

~~~
nwallin
> If there is no system of parts, there is no entropy.

Define entropy?

Wikipedia says this about entropy:

> In statistical mechanics, entropy is an extensive property of a
> thermodynamic system. It is closely related to the number Ω of microscopic
> configurations (known as microstates) that are consistent with the
> macroscopic quantities that characterize the system (such as its volume,
> pressure and temperature). Entropy expresses the number Ω of different
> configurations that a system defined by macroscopic variables could assume.

The number of possible configurations of a black hole is hilariously large and
demands delving into up arrows and beyond. It includes collapsing stellar
cores, primordial black holes, neutron stars accreting matter until collapse,
merging black holes, kugelblitzes, etc., which all are bizarrely dislike
microstatically. Yet the possible macroscopic variables are only three: Mass,
angular momentum, and charge.

If you pretend quantum mechanics don't exist, sure, black holes don't have
entropy. But we're pretty sure something that looks a lot like quantum
mechanics does exist.

~~~
ziotom78
Moreover, entropy can be defined using either thermodynamics or statistical
mechanics. In the first case (which was the first to be developed,
historically) the entropy exists for any isolated system in thermal
equilibrium, even though the system can be subdivided into parts or not.

------
saagarjha
I really hate to do this (especially since I am not an expert in this field),
but this really seems like a philosophical argument against scientific theory
rather than one actually backed by evidence. No offense to the author, he just
goes into some sort of superficial argument that thermodynamics doesn't apply
to black holes because the analogy doesn't really make sense for what looks to
be personal issues with how certain things are defined. Honestly, it's great
and all that there are people willing to exercise caution about our current
models, but I'm not seeing anything to back Callender's views here and his
viewpoint comes across as pseudoscientific.

~~~
normalhuman
The very idea of a "scientific theory" is a philosophical concept, and your
implicit assertion that empiricism trumps abstract reasoning (which I am here
neither agreeing with nor opposing) is in itself a philosophical position.

Pseudoscience refers to activities that superficially have the aesthetics of
science but do not follow its constraints. For example, homeopathy is
pseudoscience. They dress in white coats and use chemistry lab equipment, but
they do not test their ideas with experiments that could falsify them. This
has nothing to do with reasoning with the current scientific theories. What do
you think theoretical physicists do?

I say this because more and more I notice people using "pseudoscience" in a
sense similar to "heresy", and treating philosophy as some sort of inferior
system of knowledge that is bound to be replaced by science. These people
misunderstand both science and philosophy, and would benefit from a bit more
of reading and thinking outside of their comfort zone.

~~~
naringas
> I say this because more and more I notice people using "pseudoscience" in a
> sense similar to "heresy"

I think that for some people science has replaced religion as a belief and
social control system

For these people science defines what is possible within reality and how the
world works in a fundamental way; but they don't really understand how these
scientific theories work, they just accept them.

I am not saying that science is a religion (they do work under different
constraints), I am just saying that science has started to serve a similar
role within our civilization, like religion did back in the "dark ages"

~~~
chousuke
I'm not sure that calling science "social control" in any context is fair.
It's certainly replaced religion as a tool for explaining things, but that's
what it's for.

Your wording makes it sound like there's only one "scientific" belief system,
but It's in my view really only a component of one. I think constructing your
worldview around at least theoretically verifiable claims is a definite
improvement over religious dogma, but most important is the scientific mindset
of accepting uncertainty and "I don't know" answers (until you figure them
out).

I also think it's valid to trust experts, but extraordinary claims will still
require extraordinary evidence.

Now, the social structures around science aren't perfect and bad science can
definitely be used to mislead people. That's just another problem to solve.

------
kovrik
> Stephen Hawking proved that the area of a black hole’s event horizon — the
> surface that marks its boundary — cannot decrease.

I thought he proved the opposite: that black holes (slowly) evaporate through
Hawking radiation, lose mass, hence their event horizon shrinks. Could anyone
please elaborate?

Also, do scientists actually say that thermodynamics and black holes are the
same thing? Never heard of that. I think they only mean that laws of
thermodynamics are universal and should be applicable to black holes as well.

~~~
pdonis
He proved both. He and Penrose proved theorems that showed that, under certain
assumptions, the area of a black hole's event horizon can never decrease. But
he later showed that quantum fields near the horizon can violate some of the
assumptions that are required for the area theorem, so when those quantum
effects are taken into account, black holes can radiate and this can cause the
area of their event horizons to decrease.

~~~
kibibu
So he proved "if x then y", then later proved "!x"

~~~
nightcracker
No. x -> y && !x does not give !y, it just gives nothing.

He proved y under _some set of assumptions_ , and then later !y under _another
set of assumptions_. So he proved a -> y && b -> !y.

~~~
xamuel
But, given x->y, if you prove !y, you can conclude !x, so in a sense kibibu is
right (possibly requiring "proved" to be read as "indirectly proved"), and we
should give them the benefit of the doubt.

~~~
pdonis
_> given x->y, if you prove !y, you can conclude !x_

But given x -> y, if you prove !x, you can't conclude anything. And kibibu
said !x, not !y.

~~~
kibibu
Yeah, I interpreted:

> quantum fields near the horizon can violate some of the assumptions that are
> required for the area theorem

as !x

------
giardini
Arieh Ben-Naim is a well-respected thermodynamicist who believes that
application of the laws of thermodynamics to the whole universe and to black
holes is not valid. He's written books about it:

[https://en.wikipedia.org/wiki/Arieh_Ben-
Naim](https://en.wikipedia.org/wiki/Arieh_Ben-Naim)

[https://www.amazon.com/Arieh-Ben-
Naim/e/B001HD1O86/ref=dp_by...](https://www.amazon.com/Arieh-Ben-
Naim/e/B001HD1O86/ref=dp_byline_cont_book_1)

I enjoyed Ben-Naim's "Briefest History of Time, The: The History of Histories
of Time and the Misconstrued Association Between Entropy and Time "

[https://www.amazon.com/s?k=briefest+history+of+time](https://www.amazon.com/s?k=briefest+history+of+time)

Ben-Naim takes credit for Hawking later cutting most of his "Brief History of
Tme" in later editions.

------
sidcool
Black holes are the most astonishing of stellar objects. They were
mathematically predicted first and then discovered, which is fascinating.

~~~
jsweojtj
Just like Neptune!
[https://en.wikipedia.org/wiki/Urbain_Le_Verrier](https://en.wikipedia.org/wiki/Urbain_Le_Verrier)

~~~
fhars
And Vulcan!
[https://en.m.wikipedia.org/wiki/Vulcan_(hypothetical_planet)](https://en.m.wikipedia.org/wiki/Vulcan_\(hypothetical_planet\))

... oops.

------
danbruc
_There’s a long debate in the foundations of statistical mechanics about
whether entropy is a subjective notion or an objective notion. I’m firmly on
the side of thinking it’s an objective notion._

I spread out two decks of cards on the table in front of you. One is
thoroughly mixed up, the other one is neatly ordered by suit from spades to
diamonds and each suit is ordered from ace to king, except for 7 and 8 of
clubs, they are in the wrong order. »Which deck has the higher entropy?« I
ask. »The mixed up one of course.« you answer. Out of my pocket I pull a
flashlight and turn it on, under the shine of its blacklight you can read the
numbers 1 to 52 written onto the mixed up deck in perfect order, the numbers
written onto the neatly ordered deck are in no discernible order.

~~~
mgsouth
My question is "why does the symbol '1', followed by '2', ... '52' define an
ordered state?" It would seem that the "cheat sheet" which defines the
progression is part of the system. Not sure where I'm going with that...

This brought up another set of questions: is it possible to define entropy
without a definition of simultaneity, or some other global ordering of events?
Is it possible for two different observers to have differing views of entropy?
What does rotation of the time-like axis do? Googling didn't find much, but it
did find a discussion on physicsforums [0]. The answer seemed to be... it's
complicated. Good discussion, though.

[0] [https://www.physicsforums.com/threads/time-dilation-and-
entr...](https://www.physicsforums.com/threads/time-dilation-and-
entropy.837480/)

~~~
platz
You can't calculate entropy without defining the macroscopic variables you are
interested in.

Once you have done that, you can start counting the microstates that satisfy
those macroscopic variables.

~~~
mgsouth
So, in other words, yes, entropy is subjective, and depends upon your
definition of variables (and ordering). What's the other argument, leading to
debate?

~~~
cygx

        ΔS = Q/T
    

We tend to think of energy as an objective thing (the distance your car can go
on a tank full of gas doesn't depend on your subjective beliefs), and the same
is true for temperature (commonly manifesting as an average energy and
measurable via thermometers). This implies that entropy should be considered
an objective property of the system as well.

~~~
mgsouth
So then, would this be true:

The specific value for the entropy of a system depends upon the definition of
the microvariables. However, regardless of the definition used, the measured
value will increase over time. In the deck of cards example, above, one
definition of entropy is the suites and rank, and another definition is the
numbers 1 .. 52 written on the backs. Shuffling the deck will reduce the
ordering, no matter which definition you look at.

This implies

a) No definition of microvariables and their ordering can result in an entropy
level which is the inverse of another definition.

b) Its possible to define a set of all sets, which is the union of all
possible microvariables and orderings. This uber-entropy will also increase
over time.

I suppose the philosophical argument is that "objective entropy" is either
referring to the uber-entropy, or the property that all entropies always
increase, and "subjective entropy" is looking at specific values for one
particular measurement system.

Also, c) increasing entropy over time only holds true for interaction
functions which are fully transposable. For example, if microstate X is the
result of an interaction "f" betweeen microstates A and B

state(x) = f(state(a), state(b))

state(a) = f'(state(x), state(b))

state(b) = f''(state(x), state(a))

f, f', and f'' are fully deterministic and yield unique results for every
combination of inputs.

------
sleepysysadmin
The problem with black holes is that all of our science is observationally
weak. You can't use any science that's based on the speed of electromagnetism
or for that matter light.

If your observational weakness prevents you from making any observations. Then
you know nothing at all about it.

------
kgin
> Craig Callender worries that the analogy between black holes and
> thermodynamics has been stretched too far.

Spaghettification

------
Causality1
The featured professor implies credentials he doesn't have by describing
himself as a "philosopher of science" when his actual degree is in philosophy,
not any hard science. In fact he has no scientific or mathematic background
whatsoever. Read his opinions with the same amount of skepticism you would
apply to a post on 4chan, because he's exactly as credible.

~~~
dang
This breaks the site guideline against shallow dismissals. Please don't do
that here.

~~~
Causality1
Pointing out that someone is misrepresenting themselves as an authority is not
a shallow dismissal. In fact I didn't even say he was wrong; I said take his
claims with a large degree of skepticism.

~~~
dang
Snarkily putting someone down because of his credentials is certainly a
shallow dismissal, and just the sort of thing that guideline asks you not to
do here.

------
imvetri
Human sees ant - Be busy as an ant. Ant is incredible, We have to colonise
world just like they are doing. Ant has more strength when compared to its
body. only queen ants talk to small ants. Queen controls the ants. Ants are
disciplined. Some ants attack. Some ants build bridges.

What if Human are the ant?.

Proving it being right / wrong is not the point.

