Black hole - between horizon and singularity

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Discussion Overview

The discussion centers on the nature of the space between a black hole's event horizon and its singularity, exploring whether this region is filled with matter, vacuum, or something else entirely. Participants examine theoretical implications and the limitations of current understanding regarding black holes.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the space between the event horizon and the singularity could be filled with matter falling toward the singularity, while others suggest it is simply vacuum.
  • One participant argues that while we cannot observe what is inside a black hole, there must be something present other than vacuum, as matter is continuously absorbed by the black hole.
  • Another viewpoint suggests that even if there is vacuum, it could still contain vacuum energy, and the infalling matter might contribute energy to this vacuum.
  • A later reply mentions the fuzzball string theory as a possible explanation, though its acceptance in mainstream physics is questioned.
  • One participant corrects a previous claim about visibility, stating that while observers inside a black hole can see outside, they cannot send signals back out.
  • It is noted that if something falls into the black hole, it occupies a small non-vacuum region, but the majority of the interior remains vacuum.
  • There is a mention of quantum gravity models suggesting that spacetime geometry itself may contain information, even in the absence of matter or energy.

Areas of Agreement / Disagreement

Participants express differing views on whether the region between the event horizon and the singularity contains matter, vacuum, or both. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Limitations include the speculative nature of some theories discussed, such as fuzzball string theory, and the dependence on definitions of vacuum and spacetime geometry. The conversation also highlights the challenges in observing and understanding the interior of black holes.

arlesterc
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What occupies the space between a black hole's event horizon and the singularity? Stuff hurtling to the singularity? Vacuum?
 
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arlesterc said:
What occupies the space between a black hole's event horizon and the singularity? Stuff hurtling to the singularity? Vacuum?
Actually, nobody really knows. What goes on beyond the event horizon stays beyond the event horizon.
 
arlesterc said:
What occupies the space between a black hole's event horizon and the singularity?

Nothing. A black hole is a vacuum, i.e., it is empty space everywhere.
 
We can't see into a black hole. Whatever is in the black hole can't see us. That part seems to be clear to me. However as the surface of a black hole is conjectured to have all the bits in the black hole - in fact is the limit of the bits in the black hole - it seems there is something in the black hole other than vacuum. Stuff goes into and disappears to us but that doesn't mean it isn't there in some form. And it falls toward the singularity from my understanding. As the black hole is constantly absorbing stuff it seems a lot of stuff is making this trip. So even though the form this stuff takes as it hurtles to the singularity is not observable to us it seems to be something. So the black hole doesn't seem to be merely vacuum. I can see however that the black hole could have vacuum and vacuum energy - I don't see a reason why not - feel free to give me theories for or against this proposition. And given that,I can see that the stuff going into it could add energy to the vacuum. That it would do only that however is a little harder for me to understand as I feel from all that I have read that something is hurtling to the singularity/adding to the mass of the black hole. Again feel free to persuade me otherwise. Links are good as direct explanation - but they need to be at 'interested laymen with some physics and math background' level. Thanks for any further time with this.
 
arlesterc said:
We can't see into a black hole.

Correct.

arlesterc said:
Whatever is in the black hole can't see us.

Incorrect. Light can travel into the black hole just fine, so observers inside can see things outside. They just can't send light signals back out.

arlesterc said:
as the surface of a black hole is conjectured to have all the bits in the black hole - in fact is the limit of the bits in the black hole - it seems there is something in the black hole other than vacuum.

If something falls into the hole, obviously there is a tiny non-vacuum region occupied by that something. But the rest of the inside is still vacuum.

The (speculative) point you seem to be unaware of is that, in the quantum gravity models you are referring to, spacetime geometry itself has bits of information associated with it, even if it is vacuum, i.e., even if there is no matter or energy present. So the "bits" stored at the horizon are storing information about the (vacuum) spacetime geometry inside.
 

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