Darren New <dne### [at] sanrrcom> wrote:
> Let's say the outside observer measures the slow-down of the clock and
> calculates that the victim's clock will read 1PM at the moment the victim
> crosses the EH.  Will the victim ever experience 1:01PM?  What will the rest
> of the universe look like when the victim experiences 1:01PM? If the
> victim's clock actually stops with respect to the outside universe, the
> entire universe will age and disappear (or big crunch) before the clock
> reads 1:01PM, yes?

It seems to boil down to that, yes.


> >> (Discounting the black holes that have paths to the singularity that don't
> >> cross an EH, of course.)
> >
> > How could that be?
>
> Rotating highly charged black holes that don't have the same Schwartzchild
> equations. (The Schwartzchild equations only work for non-rotating
> non-charged black holes, methinks.) If you spin the black hole fast enough,
> the equator doesn't have an EH, or the pole doesn't, or something. (I've
> heard speculation that the equations must therefore be wrong.)

Yes, Schwartzschild (an interesting name coincidence, by the way, that someone
whose name translates to "Blackshield" should be the first to discover the
formula for a black hole's event horizon) did his calculations for the most
simple of black holes.

So if there's no EH, you can just zip straight through the singularity? And
actually decide to turn around any time? Speaking of which, how will time be
affected near the singularity?

I think I recall remember having heard that spinning black holes would actually
not have a point-shaped singularity at all, but a loop, because their drag on
spacetime is that extreme.

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Darren New <dne### [at] sanrrcom> wrote:
> > Remember Achilleus and the turtle!
>
> But the universe is still around when Achilleus passes the turtle. :-)

Yeah, that's the weird part about black holes... but otherwise I find the
Achilleus-and-the-turtle image very helpful with them.

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Warp <war### [at] tagpovrayorg> wrote:
>   Lack of evidence is not evidence of the contrary. Just because a
> singularity has not been observed and measured doesn't necessarily mean
> that singularities cannot exist.

You would be right if you said that lack of *proof* is not *proof* if the
contrary. But lack of evidence (i.e. an observation that does not prove
something but still seems to support it) still is *evidence* (although maybe
not as strongly) to the contrary.

Lack of evidence that the invisible pink unicorn exists is some evidence that it
doesn't.

>   There are basically two choices:

I have made the experience that when someone presents just two choices, he's
typically overlooking something ;)

> 1) Assume that GR equations are correct in all situations, including
>    the extreme ones. There's little evidence to show that this wouldn't
>    be so. One consequence of this is accepting singularities, at least
>    until better evidence shows up.
>
> 2) Object to the notion of a singularity to be possible. This implies that
>    GR equations do *not* work in all possible situations, and that they
>    start to deviate in extreme conditions. However, no concrete evidence
>    of this exists, nor widely accepted alternative theories.

Or 3) Merely *question* the notion of a singularity being possible, drawing the
following conclusions:

* Assume that GR equations *may* be wrong in extreme situations like a
singularity, or even close to it; note that this may actually help *defend* GR
- because if we find that the singularity predicted by GR doesn't exist, we can
just interpret the singularity in the equations as saying that GR never
predicted anything (sensible) at all for these conditions in the first place.

* Take it as an incentive to search for other ways of seeing things, hoping to
come up with something that does the same job as GR (in all non-extreme
situations) but gives a non-singularity answer for the extreme situations. It
may actually be that we find a theory that has singularities somewhere else,
like - say - a point where there is no gravity (just a *very* wild speculation,
please don't jump on *this* one ;)), but otherwise gives sufficiently similar
results as GR does.

* Still, at the same time, without a tested superior theory, continue to use GR.


>   It may well be that singularities can not exist in this Universe, and
> that something else is happening with collapsing stars (stars do collapse
> due to gravity, which is something basically nobody doubts). However, as
> long as viable theories or, better yet, evidence of alternatives are not
> presented, science in general has to take choice #1.

No, science *must* take choice #3.


>   As far as I understand it, science is not about the Truth. The Truth may
> be impossible to achieve. Science is about the best we know so far. About
> getting as close to the truth as we can, by observing and measuring.

That's why #1 is stupid. The singularity problem is already an indicator that GR
*may* be wrong there, so why wait until this indicator turns to hard evidence
before starting to look for alternatives, when all experience suggests that
this indicator *will* turn to hard evidence (if the question can ever be
decided, that is)?

I'm not saying "trash GR, because it gives wrong answers for the center of a
black hole" - all I'm saying is "don't be *too* dogmatic about GR, and instead
keep your eyes peeled for fresh ideas, because GR gives *questionable* answers
for the center of a black hole."

Of course, when checking candicate alternatives, they need to stand a lot of
tests, and a lot will fail at them.

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Warp <war### [at] tagpovrayorg> wrote:
>   The observer who is falling into the black hole does experience the
> crossing.

.... unless there's an effect at the EH that prevents him from doing so.

If the victim is disintegrated into sub-atomic particles that can no longer
interact with each other nor the outside world at the very instant he crosses
the EH, I guess the answer to the question whether he ever experiences the
crossing must, once again, be the Zen "mu".

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Darren New <dne### [at] sanrrcom> wrote:
> Do you go to the doctor to check if you have the flu, even if you have no
> symptoms? No, because lack of evidence is evidence to the contrary. :-)

LOL! I tried to find a good scientific example, but didn't come up with anything
good - yours hits the mark ;)


> > 2) Object to the notion of a singularity to be possible. This implies that
> >    GR equations do *not* work in all possible situations, and that they
> >    start to deviate in extreme conditions. However, no concrete evidence
> >    of this exists,
>
> Except fermions.

Well, even with fermions, it is questionable whether this is a problem with GR,
or rather with QM.


> I don't think anyone on p.o-t knows whether GR or QM is wrong for sure.

I think you can apply this theory to outside p.o-t as well... there's currently
little evidence to the contrary ;)

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>  Yet, this is not as simple as it sounds in any case. The slingshot effect
> is always relative to something. For example interplanetary gravitational
> assist is relative to the Sun. The Sun itself cannot be used for a 
> slingshot
> effect inside the solar system (it could be used for a slingshot relative
> to the galaxy, but not relative to the solar system).
>
>  With this taken into account, can you just go from Earth to the nearest
> black hole, get an enormous speedup and come back at 100x the speed and
> slam onto Earth at that speed? From a gravity assist only, I don't think 
> so.

I was thinking, it doesn't really matter about a gravity slingshot for time 
travel, just speeding up as you go close to the black hole will suffice to 
allow you to travel forward in time.  It doesn't matter if you slow down on 
the way back because you've already done the time-travelling bit as you went 
around the black hole close to the speed of light.

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Warp <war### [at] tagpovrayorg> wrote:
>   If we assume the mass of the black hole would decrease, then the EH would
> recess. The photons which were emitted extremely close to the EH will get
> a speedup when the EH recesses. Basically the "point of entry" will stop
> being *at* the EH and becomes being *above* it. Thus all the photons will
> reach the external observer in finite time. The external observer will
> end up actually "seeing" the falling object cross the EH.

I guess it will rather be that as the black hole evaporates, the EH will shrink
as you said, but the "victim" will still seem to "stick" to it.

So from an outside observer's point of view, the moment the "victim" reaches the
singularity will be when the EH has "boiled down" to the singularity, and will
be identical with it.


It's still an interesting question though how the EH can ever boil down to
singularity if it still has the mass of a spacecraft. And all the other stuff
still sticking to its EH.

Which leads me to believe that in fact, the very moment you reach the EH of a
black hole you just simply evaporate.

Which, again, leads me to believe that there is actually no mass at all *inside*
a black hole: All that makes up the gravity well is the stuff busy falling into
it. From an outside observer unable to ever reach the EH - except due to
quantum fluctuations. Which will cause them to reach it at last and instantly
evaporate.


Duh. That's sounds simple enough to actually be true!


Now *why* would you evaporate if you reached the EH? Maybe because you would zip
off straight towards the singularity because all those evil vectors head straigt
there - but you can't stay there because, after all, it's a singularity, a "mu"
location where nothing can be - not even you, although it looks like you just
fell into there. But then again, *are* you really where you seem to be?

Enter QM: If you *can't* be there where you most likely *are*, then you must be
someplace where it's quite *unlikely* (though not perfectly impossible) that
you're there... like, say, not in the grasp of That Nasty Big Black Hole after
all... like, say, Hawaii... Alas! If only you hadn't opted for that job as a
space cadet... But... hey, did you, after all? It's a bit unlikely that you
did, given the fact that it made you end up somewhere you cannot possibly be...
so maybe you stayed home after all - or at least one of your electrons did...
Whoops! Off here goes one of your elementary particles... Or you could have
died in that explosion at Tau Alpha Ceti 6, and be part of that fascinating
dust cloud out there... Whoops! Here goes another one...

Hey, I like this idea...


Boys, I don't want to brag, but could it be that I'm just hatching an important
idea here...?? It looks to me like things are falling into place this way:

- It would explain what the singularity in the GR equations actually means: A
"forbidden point" in spacetime. A place that is not. GR being unable to give
proper results for this point because the only proper result is "mu". In fact,
it would mean that giving nonsense results for such a point would actually be a
*prerequisite* for a good theory, unless you're using it for Zen archery target
practice. Fascinating!

- It would explain where Hawking radiation actually comes from. And why it
doesn't lose information: It's still there. It has stayed home at Hawaii, got
blown up at Alpha Ceti 6, whatever - it never fell into the hole in the first
place.

Note that there's no contradiction there: All of your particles that ever
interacted with anything still "outside" on your way to the black hole
(including particles that interacted with particles that interacted with
particles that interacted with anything "outside") did pass on their
information at the very moment they interacted, so no loss happend there; for
all the particles that did not interact, QM says Schroedinger's Cat never fell
into the black hole in the first place - because now that the Black Hole Box
has evaporated, you find that you never even managed to trap it there in the
first place. It must have slipped out quietly while you were still fiddling
with the lock. Darn!

So what are black holes? Looks like a reroll in a random generator trying to
obtain a certain random distribution... or some "game over - reload saved
game?" popups for individual particles :P.

- It would explain the fermion paradoxon: If there's no fermion at the
singularity in the first place, there's no need to worry about a second fermion
trying to occupy the same spot.

<wild_guess>
Then again, maybe the fermion mechanism is actually the key to understanding the
singularity from a QM point of view: If energy densities are high enough, like
in a collapsing superstar, maybe this is sufficient to slam two fermions
together into the same quantum state, creating a particle that doesn't allow
*any* other particle to share the same spot...
</wild_guess>

However, I'd rather guess that the singularity is a forbidden point because it
is a "border" of spacetime, in a sense, and that this border is not included in
spacetime.


>   After all, how would the external observer actually see the black hole
> getting smaller?

Smaller EH of course.

>
> > looks like even after he's past the event horizon, which would imply the
> > universe hasn't ended for *him*?
>
>   I don't think that's possible. When he is exactly at the EH, the entire
> EH engulfs the entire view on all sides. He doesn't see anything else
> than the EH. What he "sees" inside... I don't know.

"Mu" again.

As I pointed out previously, I see the EH as being identical to the singularity
- a single point in spacetime blown up to macroscopic dimensions.

Actually, stating that the singularity is something which is not, this also
means that the EH is something which is not. Spacetime ends an infinitesimal
distance away from it. You can't reach it - being there is impossible, and
impossible is less likely than the infinitesimally small probability of not
having steered too close to the black hole in the first place.

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Darren New <dne### [at] sanrrcom> wrote:
> I don't know either. By now, I'm entirely in BS mode. :-)

BS is actually a good fertilizer...

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nemesis <nam### [at] gmailcom> wrote:
> It's also interesting that a blackhole is as obscure as the future and
> the objects farther away we can get a glimpse of are from a bright
> distant past that gets away from us under heavy acceleration...

Maybe we're all getting that one wrong, and the universe is actually far smaller
than we think. Maybe what we see "out there" is just one single "hypermassive"
black hole at the very other "side" of the universe - and it keeps sucking
spacetime away from us...?

Maybe what we see isn't the "big bang" after all, but the "big crunch"?

After all, there's still some quadrupole anomaly to explained in cosmic
background radiation; maybe a rotating hypermassive black hole would do the
job?


Now, why on earth - erm, I mean, why in the universe - would we happen to live
exactly on the opposite side of that hypermassive black hole? Good point -
maybe the anthropic principle comes into play here. Or maybe we're not, but
spacetime may have some weird symmetry that the distance to the HMBH measured
in one direction would automatically require the distance to it in the opposite
direction to be equal - which would explain the quadrupole anomaly.


(Okay, I'm back entirely in BS mode again now, too :))

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"clipka" <nomail@nomail> wrote:
> >   After all, how would the external observer actually see the black hole
> > getting smaller?
>
> Smaller EH of course.

.... and - which I forgot to note - as it is absolutely impossible for anything
inside the EH to ever get back out, nothing inside it would get "re-exposed" to
the outside (if there ever *was* anything truly inside it :P); instead, the
whole spacetime near the EH would shrink with it - the nearer, the stronger the
shrinking effect (though at the same time the region would probably become less
distorted)...

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