If nothing can escape a black hole, it follows that Hawking radiation can't exist?

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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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  • #4
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.
 

1. What is Hawking radiation?

Hawking radiation is a theoretical prediction by physicist Stephen Hawking that black holes emit radiation due to quantum effects near the event horizon. This radiation results from particle-antiparticle pairs that form spontaneously near the event horizon. One of the particles falls into the black hole while the other escapes, which leads to the black hole losing mass over time.

2. How does Hawking radiation escape a black hole if nothing can escape its gravitational pull?

While it's true that nothing can escape from inside the event horizon of a black hole, Hawking radiation originates just outside the event horizon. The particle-antiparticle pairs form at the boundary, and it's possible for one of these particles to escape before crossing into the black hole, while its counterpart falls in. This process does not violate the general rule that nothing can escape from within the event horizon itself.

3. Does Hawking radiation mean black holes can completely evaporate?

Yes, according to the theory of Hawking radiation, black holes can eventually evaporate entirely. As the black hole emits Hawking radiation, it loses mass. If a black hole continues to emit more mass in the form of radiation than it gains from other sources, it will gradually shrink and ultimately vanish. The time this takes depends on the size of the black hole, with smaller black holes evaporating faster than larger ones.

4. Has Hawking radiation been observed?

As of now, Hawking radiation has not been directly observed. The effects of Hawking radiation are expected to be extremely weak and difficult to detect from Earth. However, scientists continue to explore indirect methods and theoretical implications to support the existence of Hawking radiation. Advances in technology and observational techniques in the future may allow for the detection of this phenomenon.

5. What implications does Hawking radiation have for the laws of physics?

Hawking radiation has significant implications for theoretical physics, particularly in the contexts of quantum mechanics and general relativity. It suggests that black holes are not completely black but instead emit radiation, which leads to a decrease in their mass and eventual evaporation. This challenges the traditional view of black holes as simple gravitational sinks and has implications for the conservation of information in the universe, potentially affecting theories about the ultimate fate of information that falls into a black hole.

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