[achille]

> "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

[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.

[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."

[oneshtein]

We can empirically prove that gravitation cancels out in the gravitational center of an object, if we will dig into Moon.

[pdonis]

In the GR model of black holes, the singularity is at the end of time inside the hole, not the beginning.

[Twisol]

I think the "singularity at the beginning of time" being referenced here is the one postulated before / at the instant of the Big Bang.

[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.

[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.

[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.

https://en.wikipedia.org/wiki/Roy_Kerr

[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.