On 9/26/2014 10:55 AM, 'Chris de Morsella' via Everything List wrote:
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*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).
That last doesn't follow. A person falling into a large black hole would not necessarily
notice anything. Susskind has argued that they would encounter a "firewall" of trapped
radiation within a few Planck lengths of the event horizon based on his sting-theory
analysis. But that's still very controversial.
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.
Yes, that's the idea of the paper. It will still *look* like a black hole while it's
waiting for that radiation to get out.
Brent
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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