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Black hole singularity is a surface not a point

arxiv.org

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Re: Black hole singularity is a surface not a point

#181

Post by marcyb5st »

ck2 wrote: post #6

what's really going to blow your mind is while you probably assumed or knew spinning black holes move space around them spinning black holes also move TIME around them * https://www.science.org/doi/10.1126/sciadv.ady9068 so in theory a spinning black hole that's been around for billions of years has a time drag around it in a path that is billions of years old (no we can't navigate it because yes that would be time t…

Time travel breaks causality if you assume Copenhagen interpretation of quantum mechanics. Multi-world interpretation allows it as you just end up in a self-consistent "branch" and you would be stuck there.

Like you can travel back in time and kill one of your ancestors before he/she had children. In that branch you wouldn't be born, but since you come from another branch the system remain consistent.

(If you are interested look at David Deutsch’s quantum model of Closed Timelike Curves).

Re: Black hole singularity is a surface not a point

#183

Post by zelphirkalt »

ben_w wrote: post #35
0x20cowboy wrote: post #33

Earlier quoted context omitted.

> Normally people think of gravity as pulling on objects. You can instead think of it as pulling on the space those objects are in. (Very uneducated person here) I’ve always wondered if large objects caused gravity, or if maybe large objects form in the places where there is a lot of gravity. This is probably elementary, but I’ve never looked in to it. Maybe today is the day!

Dark matter is mysterious enough to be compatible with both at the same time, I think. (Is a collisionless gas really even an "object"?)

I tend to believe that dark matter is a name for something we don't understand better yet. I don't necessarily mean MOND or anything specifically, but dark matter is just a little too mysterious and convenient for my taste. Maybe in 100y we will laugh about the notion of something like an aether named dark matter, and see it as simply a model which was necessary, because we didn't get what really is going on.

Re: Black hole singularity is a surface not a point

#184

Post by saidnooneever »

sigmoid10 wrote: post #171
eru wrote: post #167

Earlier quoted context omitted.

Even without quantum mechanics, black holes are trouble: Approximately everything in nature rotates. Including black holes. Schwarzschild blockholes do not rotate. Rotating black holes are much more complicated and don't necessarily shield their singularity behind an event horizon.

Rotating black holes are described by Kerr geometries and have more than one event horizon, but still have their singularities hidden from anyone outside behind their inner horizon.

pardon a maybe stupid quesiton but a few comments say this and i wonder.

why does it matter that it is not 'visible' for anyone?

Re: Black hole singularity is a surface not a point

#185

Post by gizmo686 »

saidnooneever wrote: post #184
sigmoid10 wrote: post #171

Earlier quoted context omitted.

Rotating black holes are described by Kerr geometries and have more than one event horizon, but still have their singularities hidden from anyone outside behind their inner horizon.

pardon a maybe stupid quesiton but a few comments say this and i wonder. why does it matter that it is not 'visible' for anyone?

"Visible" in this case means "able to influence in any way".

If a problem is not able to influence anything, even in theory, then by definition, it cannot possible influence any testable predictions we have.

Re: Black hole singularity is a surface not a point

#186

Post by XorNot »

inigyou wrote: post #157
XorNot wrote: post #88

Earlier quoted context omitted.

Not quite: inside a closed surface you can't escape, but things can repeat. You can avoid a coordinate, for example by choosing not to go there, or revisit another one repeatedly. A black hole on the other hand doesn't have that: you cannot revisit old locations - attempting to do so moves you closer to the singularity.

Unless it's a spinning black hole, which contains closed timelike curves that can be reached from and can escape back to the outside universe?

None of those proposed time machines has ever turned out to be theoretically workable when the details are investigated more closely by physicists.

Re: Black hole singularity is a surface not a point

#187

Post by jiggawatts »

DrJokepu wrote: post #165

I have a question for any physicists here. Due to my engineering background, I know just enough physics and mathematics to completely misunderstand general relativity and quantum mechanics. However, one pattern I have noticed is that one favorite past time of physicists is looking at the mathematical models, trying to find insane ass edge cases and then trying to interpret them. With that in mind, do these equations…

This is the "cosmic censorship hypothesis": singularities are always hidden by an event horizon and can never be observed without falling victim to them. Or more accurately, any observer of a singularity can never communicate that information to someone who is not a victim.

This is hypothetical, and not at all "proven" in any meaningful sense.

Re: Black hole singularity is a surface not a point

#188

Post by rfgplk »

The primary issues with black holes and singularities (as well as the numerous endless debates about them) is due to admitting only a single temporal dimension as the sole representation of the universe. Once you allow multiple temporal dimensions (at least two non gauge constrained ones) the issues disappear entirely.

Re: Black hole singularity is a surface not a point

#189

Post by DexesTTP »

rfgplk wrote: post #188

The primary issues with black holes and singularities (as well as the numerous endless debates about them) is due to admitting only a single temporal dimension as the sole representation of the universe. Once you allow multiple temporal dimensions (at least two non gauge constrained ones) the issues disappear entirely.

The issue is that we only observe one dimension of time and three dimensions of space. So allowing more than that would require a lot of evidence.

Postulating that there's multiple times dimensions is the same thing as postulating that there's more than three space dimensions in string theory. You make the maths "easier" by postulating that there's more dimensions, but you don't make any predictions that the 3+1 spacetime theory doesn't make and that can be observed experimentally.

Re: Black hole singularity is a surface not a point

#190

Post by Ajoha »

sigmoid10 wrote: post #177
NooneAtAll3 wrote: post #114

Earlier quoted context omitted.

OSM - slight generalization of Schwarzshild BH, where you take evolving spherically-symmetric mass distribution instead of point mass - shows that point singularity in the middle can be naked (aka observable), so it's not just QM that causes worms... https://en.wikipedia.org/wiki/Oppenheimer–Snyder_model

It is not difficult to construct geometries with naked singularities. Reissner, Nordström, Weyl and others individually came up with one long before Oppenheimer. You can also construct geometries where faster than light travel is possible. But all of these suffer from fundamentally unphysical energy conditions. Quantum mechanics may change the picture because it allows weirder energy states than normal physics becaus…

Thanks, I enjoyed your answers !
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