What is the true nature of the mass of a black hole?

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Discussion Overview

The discussion centers on the nature of mass in black holes, exploring theoretical implications and conceptual challenges related to mass, spacetime, and the behavior of particles within black holes. Participants engage with ideas from general relativity and quantum gravity, questioning the relationship between mass and spacetime geometry.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that mass is an attribute of matter attached to particles, questioning what happens to mass when particles are crushed inside a black hole.
  • Others argue that mass in general relativity is a property of spacetime geometry, not merely an attribute of particles.
  • A participant suggests that if a theory of quantum gravity is developed, it may clarify the true nature of mass within black holes.
  • There is a contention regarding whether spacetime itself is destroyed inside a black hole, with some asserting it is altered rather than completely obliterated.
  • Questions arise about the role of the Higgs field and bosons in relation to mass inside a black hole, with uncertainty about their survival in such extreme conditions.
  • Participants express frustration over misunderstandings and the need for clear references to support claims made during the discussion.
  • One participant emphasizes the importance of adhering to forum rules and providing sources for claims to facilitate productive discussion.
  • A later reply introduces the concept of asymptotic methods for defining mass in the context of general relativity, highlighting the complexity of measuring mass in a gravitational field.

Areas of Agreement / Disagreement

Participants exhibit a mix of agreement and disagreement, particularly regarding the nature of mass and spacetime in black holes. Multiple competing views remain, and the discussion does not reach a consensus on these complex topics.

Contextual Notes

Limitations include unresolved definitions of mass, the dependence on theoretical frameworks, and the complexity of measuring mass in a gravitational context. Participants reference various sources and interpretations, which may lead to misunderstandings.

Brunolem33
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The question is probably naive, but please don't block this thread before I get an answer...

As far as I know, mass doesn't exist by itself, it is rather an "attribute" of matter or, let's say it is attached to particles...no particle = no matter = no mass.

Now, inside a black hole, everything, that is, particles, is crushed into nothingness.

And yet it seems that once disintegrated, the mass of the concerned particles remains, since we are talking about the mass of a black hole...which depends on its appetite.

Hence the question: to what exactly is the mass of a black hole "attached" to ? (since I suppose mass is not simply floating around in the void)
 
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Brunolem33 said:
The question is probably naive, but please don't block this thread before I get an answer...

As far as I know, mass doesn't exist by itself, it is rather an "attribute" of matter or, let's say it is attached to particles...no particle = no matter = no mass.

Now, inside a black hole, everything, that is, particles, is crushed into nothingness.

And yet it seems that once disintegrated, the mass of the concerned particles remains, since we are talking about the mass of a black hole...which depends on its appetite.

Hence the question: to what exactly is the mass of a black hole "attached" to ? (since I suppose mass is not simply floating around in the void)
Good question and there's likely a Nobel Prize in your future if you can answer it. Presumably if/when we evolve a proven theory of quantum gravity we'll know what's REALLY going on in there whereas now the math in GR just breaks down to an un-physical answer which we call the "singularity".
 
Brunolem33 said:
As far as I know, mass doesn't exist by itself, it is rather an "attribute" of matter or, let's say it is attached to particles...no particle = no matter = no mass.

This is not correct. "Mass" in GR, properly speaking, is a property of spacetime geometry. The attribute of matter that you are describing is called "stress-energy" in GR, not "mass".

Brunolem33 said:
to what exactly is the mass of a black hole "attached"

To the geometry of spacetime.
 
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But isn't spacetime also crushed into oblivion in a black hole?
 
Brunolem33 said:
isn't spacetime also crushed into oblivion in a black hole?

No.
 
Could you go a bit more into details?

Inside a black hole, time stands still, which is a serious alteration of spacetime, if not a complete destruction.

And what about the 3 spatial dimensions? I understood that they were "compressed" into one...singularity...

I think it was in "The physics of Interstellar", Kip Thorne wrote that there is nothing inside a black hole, and that includes spacetime.

How can mass be preserved in such conditions?
 
Brunolem33 said:
Inside a black hole, time stands still, which is a serious alteration of spacetime, if not a complete destruction.
No it doesn't, where are you getting this information? You are either misunderstanding the source or the source is wrong.
 
OK...back to the first answer then: "mass is attached to the geometry of spacetime" and thus there is no need of a particle to have mass.

Yet, what happens to the Higgs field and bosons in the black hole?

Are these not requested for the existence of mass, or are they surviving inside the black hole, even though the boson is a particle that is not supposed to be safe there?
 
Orodruin asked you to explain where you were getting this from,. not to switch to italics.
 
  • #10
Oh...no need to jump to my throat!
It was a misunderstanding...and sorry for the italics, I don't even know how I switched to italics...
And you guys at Physics Forums really need to cool down...we are just talking here, hence the word "forum", we are not in class, we can be wrong and then learn from our mistakes...we are not all experts, at least I am not...just a layman trying to educate himself...
 
  • #11
Brunolem33 said:
Oh...no need to jump to my throat!
It was a misunderstanding...and sorry for the italics, I don't even know how I switched to italics...
And you guys at Physics Forums really need to cool down...we are just talking here, hence the word "forum", we are not in class, we can be wrong and then learn from our mistakes...we are not all experts, at least I am not...just a layman trying to educate himself...
Might be a good idea for you to review the forum rules that you agreed to when you signed up. The PURPOSE of the "just talking here" is to discuss mainstream physics, which you do not seem to be doing. Wanting to educate yourself is great, but when someone asks you for the source of your "facts" it is good form to reply directly and immediately, not avoid the question. The reason for that is, as orodruin said, that we need to be able to figure out whether what you read is wrong or if you perhaps misunderstood what you read. This greatly increases our ability to give you a helpful answer.
 
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  • #12
Brunolem33 said:
Oh...no need to jump to my throat!

I note that you still haven't answered his question.
 
  • #13
Orodruin asked if it was a misunderstanding or a wrong source...I wrote, in answer to V50 that it was a misunderstanding...
 
  • #14
Brunolem33 said:
Orodruin asked if it was a misunderstanding or a wrong source...I wrote, in answer to V50 that it was a misunderstanding...
No I did not, this was the question:
Orodruin said:
No it doesn't, where are you getting this information?
Unless you actually provide this information, there is no way for us to tell which is the case and how to correct your misunderstandings.
 
  • #15
Brunolem33 said:
I think it was in "The physics of Interstellar", Kip Thorne wrote that there is nothing inside a black hole, and that includes spacetime.

Please give an explicit reference and quote. Somebody is seriously misunderstanding something here, and I strongly doubt it is Kip Thorne. There is certainly spacetime inside a black hole, not to mention objects that have fallen in.

Brunolem33 said:
we are not all experts, at least I am not...just a layman trying to educate himself...

And if you want us to help you with that, you need to give explicit references to the sources you have already consulted. Otherwise we can't tell where you are going wrong; we can only tell that you must be going wrong somewhere, since you are coming to incorrect conclusions.
 
  • #16
Thread moved to the relativity forum as it is more appropriate there.
 
  • #17
Asynptotic methods are needed to define mass rigorously.

It is impossible to determine the mass of a gravitating body by simply adding up the contributions of particles, matter fields and the gravitational field. In general relativity, the concept of local gravitational energy is meanigless. This is because of the equivalence principle - in a freely falling frame gravity disapears, so what was thought as gravitational energy density in one frame is nothing in another frame.

The only meaniful definition of mass is a global one, namely the quantity that determines the asymptotic gravitational field, as probed for example by orbiting particles.
 

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