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On Jan 15, 2011, at 11:52 AM, nick herbert wrote:
General relativity IS CLASSICAL, Jack.
So is the concept of horizons.

Sure, but any classical theory has quantum corrections.
So you deny the work of Bekenstein, Hawking, Unruh, Davies, Gibbons, t'Hooft & Susskind et-al on the quantum thermodynamics of classical horizons?
3 years ago Proxima Centauri went nova
but not even Uri Gellar noticed
because this space-time event
is currently outside our event horizon.

Nick you are confused about the meaning of "event horizon" - that is not our future event horizon. Nick your argument is not even wrong because you are confounding past OPTICAL horizons with our FUTURE event horizon.
"event horizon" means gtt = 0
the past optical horizon you confound that with has nothing to do with gtt = 0 - the past optical horizon is only due to the finite speed of light not a property of the representation of the ds^2 metric field relative to a class of arbitrarily chosen detectors.
I don't know what Uri Geller has to do with this. Note correct spelling of his name.
In 2012 a wave of gamma will cross this horizon
and wipe out all non-microbial life forms on Earth.

Hey Nick, how do you know? Have you been doing precognitive remote viewing amping up the signal nonlocality efficiency of your brain with exotic nanomotors? ;-) Ah, so that's what my 1-5-11 precognition of dread was all about - this message of The End from you on 1-15-11?
Sarfatti claims that horizons act like absorbers
for reasons he is not able to clearly explain.

My argument is that since virtual electron-positron pairs are clamped to horizons as accelerating static LNIFs relative to us at r = 0.
gtt = -1/grr = 1 - / ^2  observer dependent in the static LNIF representation of ds^2 absolute invariant.
Therefore, they see an Unruh temperature that provides enough energy to elevate them to a real electron-positron plasma that will absorb any null geodesic photons hitting the horizon.
However, this happens only within a Gme/c^2 ~ 10^-55 cm thickness of the 2D future event horizon much smaller than the Planck thickness.
Agreed my argument rests on shaky ground at the moment.
However, Hoyle and Narlikar have an independent argument leading to the same conclusion. Will collect that later.
Nick thinks GR horizons, like the ones at sea,
are ubiquitous and nothing special
as far as the radiation that's crossing them is concerned.
You've shown me no reason to believe differently
Quoting big names, Jack,
is not the same as an argument.

At least I spell their names correctly - most of the time and I never use the big big D ;-)
On Jan 14, 2011, at 10:47 PM, JACK SARFATTI wrote:
On Jan 14, 2011, at 10:21 PM, nick herbert wrote:
There's lots of stuff we can't see because
it's too far away for light to reach us--
separated from us by a (moving) horizon.

Yes, but you are ignoring all the work of Bekenstein, Hawking etc on the quantum thermodynamics of horizons.
You are thinking classically.
However, I admit this is very weird stuff.
The apparent subjectivity of our future horizon is one weird aspect.
Likewise there are parts of the universe
that can't see us because our light has not reached them yet.
For some observers, we are exactly on the horizon.
You are ignoring horizon complementarity.
The horizon thermodynamics is for accelerating observers.
It has no meaning to say we are exactly on the horizon even momentarily if we are geodesic observers. Also event horizons are 2D closed surrounding surfaces. World lines are 1D intersecting them.

See references below on "horizon complementarity".
Even in the case of the black hole which is not subjective, the geodesic observer does not see anything unusual at the horizon itself unlike the hovering static LNIF observer.
When ships seem to disappear "over the horizon"
nothing really happens to them.
Likewise at optical horizons.
Maybe some people believed that ships actually went over the edge of the world
when they disappeared beneath the horizon but hardly anyone believes that today.
Some people believe that something special happens at optical horizons.
I am not one of those people..
No, that is not the problem. The optical horizon analogy misses the point. It's not a valid comparison at all in my opinion.
"Black hole complementarity is a conjectured solution to the black hole information paradox, proposed by Leonard Susskind[1] and Gerard 't Hooft.[2]
Ever since Stephen Hawking suggested information is lost in evaporating black hole once it passes through the event horizon and is inevitably destroyed at the singularity and that this can turn pure quantum states into mixed states, some physicists have wondered if a complete theory of quantum gravity might be able to conserve information with a unitary time evolution. But how can this be possible if information can't escape the event horizon without traveling faster than light? This seems to rule out Hawking radiation as the carrier of the missing information. It also appears as if information can't be "reflected" at the event horizon as there is nothing special about it locally.
Leonard Susskind[3] proposed a radical resolution to this problem by claiming that the information is both reflected at the event horizon and passes through the event horizon and can't escape, with the catch being no observer can confirm both stories simultaneously. According to an external observer, the infinite time dilation at the horizon itself makes it appear as if it takes an infinite amount of time to reach the horizon. He also postulated a streched horizon, which is a membrane hovering about a Planck length outside the horizon which is both physical and hot. According to the external observer, infalling information heats up the stretched horizon, which then reradiates it as Hawking radiation, with the entire evolution being unitary. However, according to an infalling observer, nothing special happens at the event horizon itself, and both the observer and the information will hit the singularity. This isn't to say there are two copies of the information lying about — one at or just outside the horizon, and the other inside the black hole — as that would violate the no cloning theorem. Instead, an observer can only detect the information at the horizon itself, or inside, but never both simultaneously. Complementarity is a feature of the quantum mechanics of noncommuting observables, and Susskind proposed that both stories are complementarity in the quantum sense.
Interestingly enough, an infalling observer will see the point of entry of the information as being localized on the event horizon, while an external observer will notice the information being spread out uniformly over the entire stretched horizon before being re-radiated."
Now I am proposing a similar idea for our future event horizon. I agree it's strange and the issue is not settled.
Lenny only considers the distant hovering LNIF. Even more weird is the momentarily locally coincident LIF Alice and LNIF Bob just before Alice falls through the horizon. Can Alice catch fire from Bob for example if too close to him? The issue is unitarily non-equivalent quantum vacua for LIFs and LNIFs when coincident - not part of strictly classical GR of course.
[0811.4465] Horizon Complementarity and Casimir Violations of the ...
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[hep-th/9306069] The Stretched Horizon and Black Hole Complementarity
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Black hole complementarity - Wikipedia, the free encyclopedia
Instead, an observer can only detect the information at the horizon itself, or inside, but never both simultaneously. Complementarity is a feature of the ...
en.wikipedia.org/wiki/Black_hole_complementarity - Cached
[PDF] Using Finite-Dimensional Complementarity Problems to Approximate ...
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Stephen W. Hawking, G. W. Gibbons, E. Paul S. Shellard - 2003 - Biography & Autobiography - 879 pages
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On Jan 14, 2011, at 6:06 PM, JACK SARFATTI wrote:
On Jan 14, 2011, at 5:37 PM, nick herbert wrote:
Everyplace in the universe is a horizon for some observer.
False I think.
Let's see
Now this is only on the cosmological scale where a galaxy is approximated as a "point".
It's not clear to me that your sentence above is true in the relevant context.
Our observable universe from the POV of everyone on Earth, indeed everyone in our galaxy I suppose, has pretty much almost the same past particle and future event horizon.
According to Hawking our future event horizon has thermodynamic properties. True even LNIF observer dependent Rindler horizons have thermodynamic properties.
So I don't quite see the relevance of your above sentence.
Nothing special is happening to light here on Earth (a horizon for some).
It's not true that our Earth's world line is a horizon for an observer. A horizon is a 2D surrounding surface. A 1D world line is not a surrounding 2D surface. Also a horizon is a null geodesic 2D surface for some metric guv field.
For example
ds^2 = (1 - / ^2)dt^2 - (1 - / ^2)^-1dr^2 - ....
is the de Sitter metric for static LNIFs with US at r = 0.
All static LNIFs at fixed r from us are accelerating in tensor sense with an Unruh temperature
~ c^2/^1/2(1 - / ^2)^-1/2 ---> infinity mathematically at the 2D horizon.
Thus I don't believe (as you seemingly do)
that a horizon acts as a Cramerian absorber of last resort.
I do agree with Nick that this horizon complementarity is very weird - a geodesic observer passing through our future event horizon will not see anything strange.
But we see dark energy density that is the inverse area A of our future event horizon i.e.
dark energy density = hc/Lp^2A
So Nick how do you explain that? Merely a random coincidence?
Do you think Gibbons and Hawking are mistaken?