Can Black Holes Really Evaporate and Lose Mass?

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Discussion Overview

The discussion revolves around the concept of black holes and their potential to evaporate, specifically through mechanisms such as Hawking radiation. Participants explore the origins of Hawking radiation, the implications of black hole evaporation, and related questions about the universe's expansion and the nature of black holes.

Discussion Character

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

Main Points Raised

  • Some participants assert that black holes emit Hawking radiation, which leads to their evaporation and loss of mass.
  • There is a suggestion that the precise origin of Hawking radiation is debated, with some attributing it to quantum fluctuations.
  • One participant mentions that extremal black holes at absolute zero do not radiate, raising questions about the observational evidence for black holes.
  • Participants discuss the methods of detecting black holes, including gravitational lensing and radiation from accretion discs, while noting that Hawking radiation is too weak to be detected directly.
  • There are differing views on the universe's expansion, with some attributing it to gravitational forces and others suggesting a role for charge.
  • One participant proposes a connection between black hole evaporation, dark matter, and the expansion of the universe, suggesting that proton destruction could explain these phenomena.

Areas of Agreement / Disagreement

Participants generally agree that black holes emit Hawking radiation, but there are multiple competing views regarding its origin and the implications of black hole evaporation. The discussion on the universe's expansion also remains unresolved, with differing opinions on its causes.

Contextual Notes

Some claims about the observational evidence for black holes and the nature of Hawking radiation depend on theoretical constructs and assumptions that are not universally accepted. The discussion reflects ongoing uncertainties in the field.

robsharp14
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black holes evaporate, i know that it sounds like it defies all rational elucidation but i think that black holes evaporate. see black holes emmit black body radiation they also emmit hawking radiation and hawking radiation as far as I am informed shrinks black holes it causes them to lose mass and even matter.
 
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Yes. This is highly agreed upon. (Although to the black body radiation black holes emit *is* Hawking radiation)
 
ok thanks
 
question, where does hawking radiation come from?
 
and i have another question,what makes the universe expand? is it anti gravity or no one knows for sure
 
one more question. if god exists what is he made of,and how can he survive the big crunch?
 
robsharp14 said:
one more question. if god exists what is he made of,and how can he survive the big crunch?

This would probably be better asked in a philosophy or theology forum, rather than an Astrophysics forum.
 
robsharp14 said:
question, where does hawking radiation come from?
From Stephen Hawking, of course :-p
 
  • #10
there are different views about the precise origin or Hawking radiation, but I think there is general agreement that quantum fluctuations are the ultimate source.

Extremal black holes, at absolute zero, apparently do not radiate...these are as far as I understand theoretical constructs...in fact I don't believe we have absolute observational evidence for any black holes yet...
 
  • #11
Naty1 said:
there are different views about the precise origin or Hawking radiation, but I think there is general agreement that quantum fluctuations are the ultimate source.

Extremal black holes, at absolute zero, apparently do not radiate...these are as far as I understand theoretical constructs...in fact I don't believe we have absolute observational evidence for any black holes yet...

Wouldn't black holes BE unobservable by definition? The fact that we have things that act as theories on black holes predict, including unobservability, makes it, at least to me, seem rather convincing.
 
  • #12
TubbaBlubba said:
Wouldn't black holes BE unobservable by definition? The fact that we have things that act as theories on black holes predict, including unobservability, makes it, at least to me, seem rather convincing.
Black holes could be detected by observing their gravitational effect on their surroundings. Gravitational lensing, in which the black hole's gravity distorts the light from sources behind it, is one way. Also, by measuring the energy of the radiation from accretion discs, one can infer the existence (and mass) of the black hole. This second method is more indirect than the former, however, just because we can't use light to 'see' a black hole, this does not mean that they are undetectable in principle.
 
  • #13
I know, that's why I said unobservable rather than undetectable. But thanks for the elaboration.
 
  • #14
I see little difference between those words. But this is no place for a semantic argument. Since this is a common question asked by forum goers, I think it's important to make the point that even though black holes are not visible, they are still observable.
 
  • #15
Black holes are usually detected by radiation emitted by their accretion disc. Others are detected by their gravitational influence in a binary [or more] system. Gravitational lensing another possibility although I'm unaware of any direct detections by this method [too many plausible alternatives]. None are detected by virtue of their hawking radiation, it is much cooler than the CMB.
 
  • #16
Black Hole evaporation. Hawkins radiation. and dark matter. I think are the remains of proton distruction. It would explain why the universe is expanding as the charge would be positive and would repel all mater coming close to it. It would also account for the mismatch of strong and weak forces. Has anybody looked at this as a solution. Only areas where negative charges are abundant (electrons) would be able to accumulate and form stars and element solids.
 
  • #17
bapowell said:
I see little difference between those words. But this is no place for a semantic argument. Since this is a common question asked by forum goers, I think it's important to make the point that even though black holes are not visible, they are still observable.

No scientist has ever admitted to actually seeing a black hole; though, there are good indicators where one might be though.

By their very nature black holes do not directly emit any signals other than the hypothetical Hawking radiation. Since the Hawking radiation for an astrophysical black hole is predicted to be very weak, this makes it impossible to directly detect astrophysical black holes from the Earth. A possible exception to the Hawking radiation being weak is the last stage of the evaporation of light (primordial) black holes. Searches for such flashes in the past has proven unsuccessful and provides stringent limits on the possibility of existence of light primordial black holes.[64] NASA's Fermi Gamma-ray Space Telescope launched in 2008 will continue the search for these flashes.[65]

Astrophysicists searching for black holes thus have to rely on indirect observations. A black hole's existence can sometimes be inferred by observing its gravitational interactions with its surroundings.

http://en.wikipedia.org/wiki/Black_hole#Observational_evidence
 
  • #18
There is a good chance that, within a decade or so, we should be able to "image" the astrophysical black hole at the centre of our galaxy. See

http://www.scientificamerican.com/article.cfm?id=portrait-of-a-black-hole

http://arxiv.org/abs/astro-ph/0607279.
 
Last edited:
  • #19
George Jones said:
There is a good chance that, within a decade or so, we should be able to "image" the astrophysical black hole at the centre of our galaxy. See

http://www.scientificamerican.com/article.cfm?id=portrait-of-a-black-hole

http://arxiv.org/abs/astro-ph/0607279.


Note the "good chance" - but I have high hopes. Over the years our technology surprises us again and again.
 
  • #20
the universe as i see it is expanding because of the throw which caused th big bang ... the gravity being a very weak force , caoul not stop this expasion , hence we keep on expanding ... but friedman proposes 3 models in which , the first one says that gravity will dominate and there will again be a big crunch , the 2nd says that the 2 forces will balnce out and th 3rd says that the universe will expand to infinity ...
and taxman , i don't think the universe is expanding because of charge ...
and hawking radiation comes from a particle and an antiparticle formed just aboive the event horizon
 
  • #21
andya said:
and hawking radiation comes from a particle and an antiparticle formed just aboive the event horizon

Well the hawking radiation is itself the particle and anti particle emitted
 
  • #22
taxman said:
Black Hole evaporation. Hawkins radiation. and dark matter. I think are the remains of proton distruction. It would explain why the universe is expanding as the charge would be positive and would repel all mater coming close to it. It would also account for the mismatch of strong and weak forces. Has anybody looked at this as a solution. Only areas where negative charges are abundant (electrons) would be able to accumulate and form stars and element solids.
Yes, and it has not been taken seriously.
 

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