How do black holes radiate if nothing can escape?

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Discussion Overview

The discussion centers on the concept of black hole radiation, specifically addressing how black holes can radiate despite the belief that nothing can escape from them. The scope includes theoretical explanations and the implications of Hawking radiation.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions how black holes can radiate if nothing escapes from them.
  • Another participant asks for clarification on what is meant by "radiate."
  • A participant introduces the concept of Hawking radiation, suggesting that black holes must lose mass somehow.
  • One explanation provided involves vacuum fluctuations creating particle-antiparticle pairs near the event horizon, with one particle falling into the black hole and the other escaping, leading to a loss of mass for the black hole.
  • It is noted that the escaping particle appears to be emitted from the black hole, despite the black hole's nature.
  • A reference to Wikipedia is made for a simplified explanation of Hawking radiation.
  • Another participant asserts that the radiation originates from outside the event horizon.

Areas of Agreement / Disagreement

Participants express differing levels of understanding and clarity regarding the mechanisms of black hole radiation, with no consensus reached on the explanations provided.

Contextual Notes

Some assumptions about the nature of energy and particle interactions near black holes are not fully explored, and the discussion relies on simplified models of complex phenomena.

2sin54
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Hi. So, as title says, how can black holes radiate if nothing can escape from them?
 
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Radiate what?
 
Well, what about Hawking radiation? Black holes have to lose their mass in some way, but how can they emit something?
 
A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle.
From Wikipedia

Wikipedia has a decent explanation in the first couple paragraphs.
http://en.wikipedia.org/wiki/Hawking_radiation
 
Because the radiation is from outside the event horizon, in short.
 

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