I wonder about the use of cicumlocutions like "from the perspective of
an outside observer". In special relativity it it is often said that a
moving object will looked shortened along the direction of motion. But
as Terrell pointed out that's not at all how they look. It is more
accurate to say that /measuring/ a moving a object will show that it is
shortened along the direction of motion; the difference being that the
measurement corrects for the fact that you want the difference in
arrival time of photons that left the ends of the object at the same
time (an ill defined concept), instead of the image formed by photons
that arrived at the same time. But then I think, why not correct for
the Lorentz contraction too in the measurement and arrive at what we
might call "the proper length". That's just as "measured" as either of
the other two.
By the same reasoning, you're really saying the visual impression of a
distant observer is that infalling stuff appears to be on the surface of
the event horizon. Which is because it takes forever for photons to
reach him. But why should he be so naive. He knows what he's seeing is
arbitrarily far in his past; so what he should be said to "measure" or
"calculate" is that the stuff has already been annihilated at the
"singularity" in his reference frame.
Brent
On 7/16/2020 4:08 PM, Lawrence Crowell wrote:
Gravitons do not escape from a BH, any more than can light. However,
from the perspective of an outside observer all matter than went into
a BH is on the surface above the event horizon, called the stretched
horizon.
LC
On Thursday, July 16, 2020 at 9:08:11 AM UTC-5 [email protected] wrote:
On Tuesday, July 14, 2020 at 10:59:54 PM UTC-6, Alan Grayson wrote:
On Tuesday, July 14, 2020 at 4:45:25 PM UTC-6, Lawrence
Crowell wrote:
On Tuesday, July 14, 2020 at 2:25:39 PM UTC-5, Alan
Grayson wrote:
On Tuesday, July 14, 2020 at 9:43:11 AM UTC-6,
Lawrence Crowell wrote:
On Tuesday, July 14, 2020 at 5:55:52 AM UTC-5,
Alan Grayson wrote:
On Tuesday, July 14, 2020 at 4:34:00 AM UTC-6,
Lawrence Crowell wrote:
On Monday, July 13, 2020 at 6:30:46 PM
UTC-5, Alan Grayson wrote:
On Monday, July 13, 2020 at 5:19:30 PM
UTC-6, Lawrence Crowell wrote:
About the EP; I merely stated that it
demonstrates that acceleration is
locally indistinguishable from
gravity, and then I stated what
"locally" means. This is what Wiki and
other sources say. Yet you say I am
confused. How so? About masses of
BH's, I watch documentaries which
feature astrophysicists offering their
opinions, and they *uniformly* claim
that BH's have mass. How could it be
otherwise if they're remnants of
massive collapsed stars? Not one makes
Brent's claim, that they're just
geometric manifestations. AG
Black hole mass is a pure spacetime
physics. There is no material stuff anyone
can get their hands on. With the tortoise
coordinate the distant observer might say
the matter-fields that made of a black
hole exist, but if one tried to reach them
they always recede away. Black holes do
not have mass in a standard sense, though
they have an ADM mass defined by the
curvature of spacetime.
Generally, what resides inside a BH interacts
gravitationally with what's exterior and is
the remnant of a Type 1A supernova. It's
unreachable, but has some correspondence with
normal mass, which is why its mass can be
estimated by its exterior effects, say for the
one residing at the core of the Milky Way. I
don't know how their masses are estimated when
they are cores of distant galaxies. AG
The interior does not interact with the exterior.
The event horizon prevents that.
Then how can a BH interact gravitationally with
objects external to the event horizon, or do you deny
that? AG
The black hole does not interact with material outside,
the material outside interacts with the black hole. A
black hole is a causality sink; causal propagation is into
the black hole. Only stochastic quantum events propagate out.
LC
I am not sure I understand or agree. Space-time is strongly
curved near a BH. Are you claiming this curvature is not
caused by the BH? In any event, doesn't this put a nail in the
coffin of quantum gravity? IIUC, the force carrying particle
in a quantum gravity theory is the graviton. If nothing can
get out of a BH, this would apply to the graviton. Seems like
a problem for any quantum gravity theory. AG
Let me put the question another way; if gravitons exist, could
they escape a BH? If not, does this adversely effect the existence
of a quantum theory of gravity? TIA, AG
From the perspective of anyone in the exterior the
interior of a black hole is nothing more than a
theoretical abstraction. It only exists as a
counter factual situation, where instead of
remaining outside an observer enters the BH/
LC
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