Are black holes theoretical or real?

[LeeJeffries]

The news always depicts them as real

http://www.bbc.co.uk/news/science-environment-13964767

But as far as I gather from reading this forum and wikipedia, black holes are always said to be "candidates"

Has it been proven "beyond a reasonable doubt" that they exist?

 

[phinds]

SOMETHING exists that exhibits the characteristics which we attribute to a thing that we call black holes for want of a better term

 

[Phrak]

SOMETHING exists that exhibits the characteristics which we attribute to a thing that we call black holes for want of a better term

So you say, apparently in favoring the idea that black holes have been positively measured. I'd be truly shocked to see you or anyone provide evidence to support the claim that black holes exhibit measurably different characteristics from incipient black holes. Shock me.

 

[Phrak]

The news always depicts them as real

http://www.bbc.co.uk/news/science-environment-13964767

But as far as I gather from reading this forum and wikipedia, black holes are always said to be "candidates"

Has it been proven "beyond a reasonable doubt" that they exist?

"Exist" has no well defined meaning in general relativity. existence is relative, to be blunt.

 

[hunt_mat]

We can study black holes in the lab by looking at their acoustic analogues:

http://en.wikipedia.org/wiki/Sonic_black_hole

 

[PAllen]

So you say, apparently in favoring the idea that black holes have been positively measured. I'd be truly shocked to see you or anyone provide evidence to support the claim that black holes exhibit measurably different characteristics from incipient black holes. Shock me.

It think what you say is true, but maybe not for much longer. There are observational programs under way to directly observer whether the hypothesized black holes in the milkyway or Andromeda have true event horizons. Within a decade, this will likely be settled observationally. This will distinguish between quantum gravity models where the event horizon never actually forms, versus those prevent the singularity but not the event horizon.

 

[George Jones]

It think what you say is true, but maybe not for much longer. There are observational programs under way to directly observer whether the hypothesized black holes in the milkyway or Andromeda have true event horizons. Within a decade, this will likely be settled observationally. This will distinguish between quantum gravity models where the event horizon never actually forms, versus those prevent the singularity but not the event horizon.

Yes, see the fascinating article "Portrait of a Black Hole",

https://www.cfa.harvard.edu/~loeb/sciam2.pdf.

 

[russ_watters]

So you say, apparently in favoring the idea that black holes have been positively measured. I'd be truly shocked to see you or anyone provide evidence to support the claim that black holes exhibit measurably different characteristics from incipient black holes. Shock me.

Isn't that hairsplitting? At least grammatically, one is a subset of the other!

I agree with phinds: "black holes" exist because that's the name we have chosen for a certain set of observations. That does not imply - nor should it be required to - that that set of observations is fully understood.

 

[TrickyDicky]

Black holes are obviously thoretical and that is IMO clearly stated in most articles, included the one in the OP where they make clear they are talking about a quasar or in the Sciam article linked by George jones where they specifically talk about this distinction.

"black holes" exist because that's the name we have chosen for a certain set of observations. That does not imply - nor should it be required to - that that set of observations is fully understood.

This is important, not only this but the theoretical black hole is just the current interpretation of the consequences of the EFE under certain assumptions. We have no way of knowing if in the future those assumptions might change and the EFE of GR may lead to different interpretations of the observations, whether it is thru some Quantum gravity theory yet to be developed or something similar.

 

[Phrak]

Isn't that hairsplitting? At least grammatically, one is a subset of the other!

No.

 

[Phrak]

It think what you say is true, but maybe not for much longer. There are observational programs under way to directly observer whether the hypothesized black holes in the milkyway or Andromeda have true event horizons. Within a decade, this will likely be settled observationally. This will distinguish between quantum gravity models where the event horizon never actually forms, versus those prevent the singularity but not the event horizon.

Do you have a link I could visit for more information? I'm not sure what to get out of this. You seem to be saying we could have observational evidience in a decade or so whether one or more black hole candidates have a measurable event horizon. What you say could be interesting.

 

[russ_watters]

No.

Care to elaborate? Ie, do you think "apple pie" is a subset of "pie"?

 

[PAllen]

Do you have a link I could visit for more information? I'm not sure what to get out of this. You seem to be saying we could have observational evidience in a decade or so whether one or more black hole candidates have a measurable event horizon. What you say could be interesting.

George Jones gave a link to the Scientific American article on this. I believe that has pointers to the primary literature.

 

[bcrowell]

By analyzing millimeter and infrared very-long-baseline-interferometry observations, Broderick, Loeb, and Narayan http://arxiv.org/abs/0903.1105 have shown that if Sagittarius A* had a surface, then the luminosity of this surface must be less than 0.3% of the luminosity of the accretion disk. But this is not physically possible, because there are fundamental limits on the efficiency with which the gas can radiate away its energy before hitting the surface. We can therefore conclude that Sagittarius A* must have an event horizon. As PAllen noted, its event horizon may be imaged directly in the near future: http://arxiv.org/abs/0906.4040