Can Hawking Radiation Exist If Nothing Escapes a Black Hole?

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Discussion Overview

The discussion revolves around the existence of Hawking radiation in the context of black holes and the implications of the information paradox. Participants explore the theoretical underpinnings of black holes, the predictions of classical General Relativity versus quantum models, and the evolving understanding of black holes as observational phenomena.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether Hawking radiation can exist if nothing escapes a black hole, highlighting a perceived contradiction in theories.
  • One participant asserts that Hawking radiation originates outside the event horizon, suggesting that this reconciles the existence of radiation with the properties of black holes.
  • Another participant emphasizes that classical General Relativity predicts black holes cannot lose mass, but Hawking's models introduce the idea of mass loss through radiation, which is still provisional due to the lack of a complete theory of quantum gravity.
  • There is a discussion about the visibility of black holes, with a participant clarifying that black holes are "seen" through their effects on surrounding matter rather than any radiation escaping from within.
  • Concerns are raised about the misunderstandings present in the original post, which some participants believe have been addressed in the discussion.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of Hawking radiation and the implications of black hole physics. There is no consensus on the interpretations of these concepts, and misunderstandings are noted but not resolved.

Contextual Notes

Limitations include the provisional nature of current models regarding black holes and Hawking radiation, as well as the ongoing challenges in developing a comprehensive theory of quantum gravity.

Walrus
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Or is Hawking radiation something? Can't be both, however if you choose one theory over another, why do you do so. Those of you who are younger will not remember a World without the information paradox, but when I was younger it did not exist in any way because nothing escaped the event horizon of the black hole which could not be seen, but now we see them. Bye the way isn't it time to change the name since they are not black anymore?
 
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Walrus said:
nothing escaped the event horizon of the black hole
The Hawking radiation that comes out originates outside the event horizon.
Walrus said:
Bye the way isn't it time to change the name since they are not black anymore?
In a few trillion trillion years when they're less black than the microwave background, maybe.
 
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Walrus said:
if you choose one theory over another
You are misdescribing what physicists are actually doing.

The prediction of classical General Relativity is that a black hole cannot lose mass. (That, btw, is the prediction that changes when Hawking radiation is taken into account. So your first misdescription is of the actual prediction that changes.)

Hawking and others have developed models that take quantum effects into account at least to some extent, and those models generally predict that black holes should emit radiation, which, if nothing else ever fell into them, would cause them to lose mass and eventually evaporate away. However, these models are only provisional because we do not have a good theory of quantum gravity.

So it is not a matter of "choosing one theory over another", it is a matter of not having a theory at all that takes into account all possibly relevant effects. But in practical terms, this is not an issue at all, because, first, the estimated Hawking evaporation time for black holes of stellar mass or larger is many, many orders of magnitude greater than the age of the unvierse, and second, all real black holes do have things falling into them--CMB radiation, if nothing else--which adds mass to them that swamps any predicted mass loss due to Hawking radiation.

Walrus said:
nothing escaped the event horizon of the black hole which could not be seen, but now we see them.
This is still another misdescription. We do not "see" black holes because of anything escaping from inside their horizons. We "see" them because of their effects on nearby objects and radiation outside their horizons.
 
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The OP is based on multiple misunderstandings, which have been corrected. This thread will remain closed.
 

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