2nd event horizon in black holes

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Discussion Overview

The discussion centers around the concept of a potential second event horizon in black holes, specifically addressing the idea that there may be a region beyond which light and energy are trapped. Participants explore various aspects of black hole theory, including classical models and the implications of rotating and charged black holes.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that black holes may have an inner second event horizon where light and energy could be trapped, although this idea lacks substantial explanation in existing literature.
  • Others express skepticism about the validity of such hypotheses, suggesting that they may be dismissed based on contemporary understanding of black holes.
  • A participant references the Kerr metric and rotating black holes, indicating that these may have multiple horizons, including a Cauchy horizon, which is distinct from an event horizon.
  • Another participant mentions that charged non-rotating black holes can also possess two horizons, contingent on the charge being sufficiently small, and discusses the implications of naked singularities.
  • There is a suggestion that a reliable understanding of black hole interiors may require an accepted quantum theory of their geometry.
  • A participant shares a link to a post discussing the Cauchy horizon and its properties within classical general relativity.

Areas of Agreement / Disagreement

Participants express a range of views, with some supporting the idea of multiple horizons in black holes while others contest the validity of the second event horizon concept. The discussion remains unresolved, with no consensus on the topic.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about black hole models, the definitions of horizons, and the lack of consensus on the implications of quantum theories for understanding black holes.

tanzanos
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I recently saw a video where it was stated that black holes may have an inner 2nd event horizon where beyond it is trapped light and energy! I have searched the web for an explanation pertinent to this hypothesis but found nothing.

Can anyone shed some light (if possible)?
 
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tanzanos said:
I recently saw a video where it was stated that black holes may have an inner 2nd event horizon where beyond it is trapped light and energy! I have searched the web for an explanation pertinent to this hypothesis but found nothing.

Can anyone shed some light (if possible)?

That was discussed on a thread here recently but it was all deleted by the mods because it's nonsense. TV physics is very entertaining but often just nonsense.
 
phinds said:
That was discussed on a thread here recently but it was all deleted by the mods because it's nonsense. TV physics is very entertaining but often just nonsense.
I will accept that is is nonsense since you say so and I have no reason to doubt you. I gather that contemporary understanding of Black holes gives us the ability to dismiss some hypotheses without hesitation?
 
tanzanos said:
I recently saw a video where it was stated that black holes may have an inner 2nd event horizon where beyond it is trapped light and energy! I have searched the web for an explanation pertinent to this hypothesis but found nothing.

Can anyone shed some light (if possible)?

I didn't see the video, so I can't say exactly what yours was about. However did you look up the Wikipedia for "Rotating black holes" and "Kerr metric"?

I suppose that a black hole can have several interesting horizons or surfaces, if it is either rotating or electrically charged.

You could also do a google search with keywords like "Reissner-Nordstrom" or "Kerr-Newman". It might be educational, or give you a better idea what the people in the video were talking about.

Personally I don't think there will be any reliable answer or consensus about interior of black holes until there is an accepted quantum theory of their geometry. But it is good to know something about the existing classical (i.e. non-quantum) models of BH. You are right to keep asking questions, also to remain skeptical.
 
Maybe this post from George Jones is relevant: https://www.physicsforums.com/showpost.php?p=1973806&postcount=3.

"(Non-extremal) Rotating black holes have two horizons. The outer horizon, the boundary of the black hole, is an event horizon, and nothing too special happens as an observer crosses this horizon. The inner horizon is a Cauchy horizon, and some calculations indicate that measured energy density diverges at the Cauchy horizon."
 
Thank you all for the information. I will check it out. Lastly I really would appreciate it if phrases such as "its Nonsense" be kept out of my posts as they offer nothing and not forgetting that science requires us to be not only inquisitive but also sceptical too!

Thanks guys!
 
Charged non-rotating black holes also have two horizons as long as the charge is sufficiently small. If the charge is sufficiently large one can obtain a naked singularity. However there is a conjecture that these cannot exist. As for the charged black hole this makes sense because a super-charged piece of matter would have a great electro-static repulsion force and would unlikely become a black hole.
 
A very interesting read indeed. Thanks!
 

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