How does black hole evaporation end?

In summary: My understanding is that it's mostly a matter of whether certain extra-dimension theories are true. If specific large-extra-dimension theories are true, then maybe it will be possible to make mini black holes at LHC energies. If different extra-dimension theories are true, or if there are only 4 dimensions, then the LHC (or even anything even close to the order of magnitude of the LHC's energy level) could never possibly make any black holes. So it seems pretty unlikely indeed that the LHC will see mini black holes! It's not just a matter of "are the energies high enough?" but also "do we happen to live in a universe which meets this specific set of slightly contrived assumptions about spac
  • #1
belliott4488
662
1
Someone asked me what happens when micro-black holes evaporate, and I have no idea, not really knowing anything about the theory of black holes, other than what you learn in a first course in GR. What he was asking was whether the black hole just keeps emitting energy (in the form of Hawking radiation, I presume?) until there is nothing left, or at some point is it light enough that it's no longer a black hole at all, but is just a lump of stuff?

My guess was that there is some critical value of the event horizon radius below which it no longer makes sense to talk about something as a black hole anymore, but I don't know what that would be - maybe some kind of effective size of the particle(s) involved?

Is this even a meaningful question? I hope so, but I'm a virtual layman when it comes to this stuff.
 
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  • #2
I, as Rioghio extreme, also known as Quantum Leap, think it is the most viable question ever asked.
 
  • #3
Don't I know you from somewhere?? ;-)
 
  • #4
belliott4488 said:
Someone asked me what happens when micro-black holes evaporate, and I have no idea, not really knowing anything about the theory of black holes, other than what you learn in a first course in GR. What he was asking was whether the black hole just keeps emitting energy (in the form of Hawking radiation, I presume?) until there is nothing left, or at some point is it light enough that it's no longer a black hole at all, but is just a lump of stuff?

If there do exist micro-black holes at all, then that is your answer, they evaporate and yet continues to exist as black holes even to the micro stage.
 
  • #5
From what I recall the black hole continues to shrink until it reaches an effective radius on par with the Planck length, at which point, as the name evaporation implies, it just 'explodes' into a lot of energy via photons and leptons, and it does this because I suppose as you said, it becomes too 'light' to be a black hole still and also has then an enormous temperature.
 
  • #6
Brad_Ad23 said:
From what I recall the black hole continues to shrink until it reaches an effective radius on par with the Planck length, at which point, as the name evaporation implies, it just 'explodes' into a lot of energy via photons and leptons, and it does this because I suppose as you said, it becomes too 'light' to be a black hole still and also has then an enormous temperature.
Ah, yes, the temperature does do up, doesn't it? I was thinking of it as just becoming more benign, in terms of energy density, but I guess it energy goes up as its mass decreases.

I guess if any of this is real, we might find out this Summer at the LHC ... should be fun.
 
  • #7
belliott4488 said:
Ah, yes, the temperature does do up, doesn't it? I was thinking of it as just becoming more benign, in terms of energy density, but I guess it energy goes up as its mass decreases.

I guess if any of this is real, we might find out this Summer at the LHC ... should be fun.

Might being the operative word. I'm a bit skeptical the energies will be sufficiently high enough to test black hole evaporation.
 
  • #8
Brad_Ad23 said:
Might being the operative word. I'm a bit skeptical the energies will be sufficiently high enough [at the LHC] to test black hole evaporation.

My understanding is that it's mostly a matter of whether certain extra-dimension theories are true. If specific large-extra-dimension theories are true, then maybe it will be possible to make mini black holes at LHC energies. If different extra-dimension theories are true, or if there are only 4 dimensions, then the LHC (or even anything even close to the order of magnitude of the LHC's energy level) could never possibly make any black holes.

So it seems pretty unlikely indeed that the LHC will see mini black holes! It's not just a matter of "are the energies high enough?" but also "do we happen to live in a universe which meets this specific set of slightly contrived assumptions about spacetime?"

But, maybe there are other ways to experiment on black hole evaporation. There is for example I am told an http://www.ece.vt.edu/swe/eta/ which could among other things detect the explosions of primordial black holes which formed and died in the chaotic conditions of the early universe. (I got that link from here.)
 
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  • #9
The odds of producing a mini black hole in the LHC are virtually zero. Cosmic rays regularly produce much higher energy collisions in Earth's atmosphere, but, there is no evidence we are besieged by radiation emanating from mini black holes evaporating in our atmosphere.
 
  • #10
Chronos said:
The odds of producing a mini black hole in the LHC are virtually zero. Cosmic rays regularly produce much higher energy collisions in Earth's atmosphere, but, there is no evidence we are besieged by radiation emanating from mini black holes evaporating in our atmosphere.

That is why I am skeptical there will be enough energy!
 

1. How does a black hole evaporate?

A black hole evaporates through a process called Hawking radiation, which occurs when virtual particle pairs are created near the event horizon of the black hole. One particle is pulled into the black hole, while the other escapes, causing the black hole to lose mass over time.

2. How long does it take for a black hole to evaporate?

The time it takes for a black hole to evaporate depends on its mass. Smaller black holes will evaporate faster, while larger black holes can take trillions of years. A black hole with the mass of the sun would take approximately 10^67 years to evaporate.

3. What happens to the matter that falls into a black hole during evaporation?

The matter that falls into a black hole during evaporation is converted into energy in the form of Hawking radiation. This energy is released into space, and the black hole loses mass as a result.

4. Can a black hole completely evaporate?

Yes, a black hole can theoretically completely evaporate if it is not constantly gaining mass. As the black hole loses mass through Hawking radiation, it will eventually reach a point where it can no longer sustain itself and will disappear.

5. What happens to the space-time fabric when a black hole evaporates?

The space-time fabric is not affected by the evaporation of a black hole. The black hole's gravitational pull may have caused distortions in the fabric, but these distortions will remain even after the black hole has evaporated.

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