New maps of the chaotic space-time inside black holes
106 comments
·February 25, 2025achille
ziddoap
PBS Space Time's take on Kerr's paper:
https://www.pbs.org/video/what-if-singularities-do-not-exist...
Echoing JumpCrisscross' sentiment, though. "Disproven" is way too strong of a word.
wigster
"kerr black holes" should surely have been "black-kerr holes" ;-)
mr_mitm
They are singularities in the framework of general relativity, i.e. while ignoring quantum mechanics. I think most people expect the right version of quantum gravity to make the singularities go away, but studying classical GR is worth it on its own, so it's often ignored like in this statement you quoted.
goatlover
What if gravity is non-linear and thus collapses the wave function? I think Penrose has suggested gravity as an objective collapse interpretation. The measurement problem still hasn't been resolved, but we observe a classical world around us, despite the fact that decoherence simply spreads the superposition of interacting quantum systems to the world. Gravity could be what prevents the linearity of quantum systems from putting the entire universe into superposition.
mr_mitm
Gravity is non-linear (as in: the Einstein field equations are non-linear differential equations).
That has nothing to do with the measurement problem. Also, the measurement problem is only a problem of the Copenhagen interpretation. It doesn't exist in the many worlds interpretation.
GoblinSlayer
Decoherence splits your state into superposition of several coherent states then you observe one classical result in each state in superposition, that's why it looks classical.
nathan_compton
As far as I know the limits on physical collapse theories are extremely strong and there are some reasonably good philosophical reasons to doubt them as well. I don't have the text in front of me at the moment but Aaronson's Quantum Computing Since Democritus has a section on this, I think. If physical collapse were true then the implications for quantum computing would beggar belief. P=NP stuff.
empath75
Sabine doesn't even say it's disproven, and the paper doesn't claim that it's disproven, it just claims that one of the earliest proofs that it was a singularity was incorrect. There's an important distinction there. If someone points out a flaw in a proof of the pythagorean theorem, that doesn't mean the theorem is disproved, it just means that the proof was wrong.
JumpCrisscross
> my understanding was that this was disproven
To the extent anything in this discussion can be absolute, it's the wrongness of your statement. Nothing about singularities has been empirically proven (or disproven).
credit_guy
You don’t seem to be new around here, so this quote from this forum’s guidelines is more for the benefit of others
> When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3."JumpCrisscross
You’re right. My apologies to OP and y’all. Can’t edit, but the snark was uncalled for.
slwvx
I don't see any name calling. Could you eplicitly state what the problem is?
pdonis
In the GR model of black holes, the singularity is at the end of time inside the hole, not the beginning.
uoaei
A more diplomatic and uncontroversial way to put it is that the event horizon is the only thing we have any evidence for.
GoblinSlayer
We don't have evidence for event horizon. Black hole is a hypothetical object to begin with, it exists only in mathematics, what evidence.
blovescoffee
The photos we have of black holes?
oneshtein
Two event horizons, because gravitation cancels out in the center of a black hole.
ps. Energy is sucked up from the center by second event horizon, but matter is pushed inside, forming a dense and cool crystal, a solid foundation for second order effects to play.
uoaei
That assumes there is gravity, or even universe, "inside" the black hole. We don't have any evidence of that.
biimugan
Your first link goes to a 2023 arXiv pre-print that never landed in any journals as far as I can tell (could be wrong though). And there seems to be some controversy about whether Kerr's math shows what he says it shows.
This is the danger of trying to sensationalize science and putting any special weight on science influencers, especially ones who very often seem gung-ho about any story that challenges the status quo despite the evidence.
monocasa
To be fair, it's written by literal Roy Kerr.
null
spwa4
Layman opinion here: If a black hole forms, the point where it forms is an event horizon, but not a singularity. Then, while things get worse, it disappear from the universe.
So why would a singularity ever form? And what can't be formed, can't exist.
mr_mitm
Cosmologist here, the event horizon is not a true singularity. There is a singularity in certain coordinates, but it goes away when doing a coordinate transformation. There is nothing physically strange going on at the event horizon. The physical singularity is only at the center.
rbanffy
I have the (layman) impression that there is no inside - that spacetime is so stretched around the event horizon that there is no spacetime beyond it.
But, then, I've never seen anywhere that the mass of the black hole (which is very much a real thing that exists in spacetime) is distributed over the event horizon, which would be at the biggest amount of mass a given region of spacetime can hold, and is not concentrated on a point with infinite density inside it.
nh23423fefe
black holes have an interior, you wouldn't notice if you passed the event horizon of a large enough black hole.
skc
So I've read that inside a black hole spacetime becomes so distorted that space and time eventually swap places.
I can't wrap my head around what it means for your future to become a destination that you can't escape in the same way you can't escape tomorrow.
How would an imaginary indestructible being that fell into a black hole make sense of this. Does intuition just flip to accomodate this?
nathan_compton
The notion you are referring to has to do with a particular set of coordinates you could use to describe the spacetime around a black hole. In that coordinate system the signature of the metric looks like (-+++) outside and(+-++) inside (roughly speaking, as it is not appropriate to think of these coordinates as t, x, y, z)1.
But the true insight of GR is that coordinates are not physical and that any physical question must have an answer that is coordinate invariant. So the whole exercise of imagining a "time direction" is moot. One can pose questions like "what do the null geodesics between two points look like as they move along their trajectories and one passes the event horizon" or questions like that. Ultimately only such questions have a physical meaning in GR and related theories.
Practically speaking in the local coordinates of an infalling observer passing the event horizon all the parts of the observer on the other side of the horizon, including signals, are simply destined to move towards the center of the black hole and the parts on the outside have some dynamical freedom not to. This is, in fact, what the inversion of the two coordinates means physically.
Footnote 1:
In Schwarzschild Coordinates the line element is given by: ds^2 = -(1 - 2GM/r) dt^2 + (1 / (1 - 2GM/r)) dr^2 + r^2 dθ^2 + r^2 sin^2(θ) dφ^2
Note that if 2GM/r is less than 2 then the sign in front of dt^2 is negative and the sign in front of dr^2 is positive. If 2GM/r is greater than one then the sign in front of dt^2 becomes positive and the sign in front of dr^2 is negative. This is the so-called inversion between a spatial dimension (r) and time. But it doesn't do to take this too seriously, as, again, the physics of the situation are entirely separate from any coordinatization we might choose.
smm11
We have NO idea. The movie was fun and all, but still.
nathan_compton
I think it overstates things a bit to say we have no idea. We have good reason to believe in the theory of general relativity over a broad range of scales and that theory provides reasonable predictions beyond the event horizon. While its certainly unclear how quantization modifies that picture, the possibilities are not infinite and we can speculate about them to some degree.
stefantalpalaru
[dead]
gunian
can confirm just delivered an amazon package in one
ck2
trying to find the PBS Space Time for that but meanwhile enjoy
> "At the beginning of time and the center of every black hole lies a point of infinite density called a singularity"
my understanding was that this was d̶i̶s̶p̶r̶o̶v̶e̶n̶ mathematically incorrect:
- https://news.ycombinator.com/item?id=38636225
- sabine's take: https://www.youtube.com/watch?v=nz55jONtFAU
edit: disproven -> mathematically incorrect