Re: Do they or don't they exist? Is anyone familiar with this paper?

Fri, 26 Sep 2014 10:56:49 -0700 



________________________________
 From: John Clark <[email protected]>
 


Before anybody gets too excited there are 2 things to keep in mind:

1) There is overwhelming empirical evidence that Black Holes DO exist, so if a 
theoretician says they don't then that's the theoretician's problem not the 
Black Hole's.

We have overwhelming astronomical evidence that  entities exist which are 
gravitationally massive and compact, by how things we can measure are affected 
by their gravitational force. I know there is a big search on to actually see a 
black hole -- or at least its accretion disk, but I am unaware that any have 
actually been detected. What we do detect is that there are entities with 
massive gravitational forces at the centers of most spiral galaxies, as well as 
unseen companions that are exerting smaller scale yet still massive 
gravitational influence on their visible counterparts.
I agree with you that this is pretty strong and convincing evidence for the 
existence of black holes, by the way... and that the onus is on the 
theoretician who makes the radical claim to back that claim up with not only 
mathematical internal consistency, but some prediction or falsifiable statement 
about what observable reality should look like as a result.
My point is that I am not as certain as you seem to be that we actually 
understand these massive gravitational entities and that black holes actually 
ever do form. As, I think Brent pointed out the time dilation at the location 
of formation of a black hole would slow time down in a relativistic manner to 
an almost pure standstill... so the burning up and process by which a black 
hole never quite is able to form but burns its mass off in Hawking radiation 
would be smeared over periods of many billions of years from our own 
relativistic perspective... and so from our own point of view they would seem 
to exist. 
Not asserting that this is so.... just pointing out that the formation (or 
never-quite-formation) of a black hole is a highly relativistic phenomena and 
that in fact someone falling through the event horizon of a black hole would 
experience time coming to a relativistic equivalent of a full stop (as Leonard 
Susskind for example has argued).
I am not clear that in practice we would necessarily observe anything different 
-- at great astronomical remove -- whether or not a black hole ever actually 
forms. The process of formation occurs within such a relativistically extremely 
distorted region of spacetime, precisely due to its massive density and gravity 
that billions of years would pass for the outside observer, viewing the 
(possible almost instantaneous) process unfold from relatively flat spacetime.

2) The most interesting sentence in the article was "The paper, which was 
recently submitted to ArXiv, an online repository of physics papers that is NOT 
PEER-REVIEWED". 

Yes, sure... this hypothesis is speculative, but the author is also an 
associate professor of physics at a major American university and is a pretty 
well known cosmologist. Not that easy to dismiss her as a fringe loon, if that 
is what you are suggesting.


  John K Clark



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