Warp <war### [at] tagpovrayorg> wrote:
>   Just because you can't tell appart gravity from acceleration doesn't
> mean that all accelerations are caused by the same phenomenon as gravity.

No, but they both cause exactly the same effects...

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> So since the person falling in will never see himself cross the EH
> 
>   I'm not sure where you are getting this one. I have not heard of it.

Hmmm.... Maybe my bad, I think.  GR isn't easy for my brain.

If his clock slows to zero on the outside and he never crosses the event 
horizon, then the next tick of the clock is infinitely far in the future of 
the universe, yes?  So he never experiences crossing the EH because it takes 
forever for his clock to tick.  Say the black hole evaporates after a 
billion years - does the space ship ever hit the singularity?

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

triple_r wrote:
> Scratch that.  It could be  LOT worse.  I could be this guy (worth at listen at
> about 31:00):

"That's what they told Galileo."
I know Galileo, and you're no Galileo. On the contrary, you're one of "they"


Heh heh heh.
-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Warp <war### [at] tagpovrayorg> wrote:
>   The foundation of GR is that gravity does not, in fact, cause
> acceleration at all. An object in "free wall" is all about inertia
> and nothing about acceleration (even though it may not look like it
> to us).

From the viewpoint of a free-falling(!) "actor", gravity is actually absent,
yes. It has no effect whatsoever - it's just that That Big Black Hole Over
There keeps accelerating towards *him*, badly mangling spacetime as it does.

Post a reply to this message

Darren New escreveu:
> nemesis wrote:
>>  holding your cup of coffee with a steady hand... :P
> 
> ... which only means you need more coffee.

LOL

Post a reply to this message

clipka wrote:
> - If the equations say that inside the EH you can't do anyhing to a particle to
> prevent it from going straight towards the center, then this might be a hint
> that particles there can't *interact* in the first palce.

It doesn't. It says no particle going at or slower than c can avoid going 
towards the center. But QM doesn't restrict particles from going FTL, either.

> Fine. So? I *love* some good crazy mix of science, philosophy and wild
> speculations, nothing wrong there for me ;)

Welcome to p.o-t!  :-)   How about some Java/C++ flames now? ;-)

> it is reasonable to assume that singularities predicted by scientific theories
> actually indicate that the theory *fails* at these conditions.

Again, I think that's what's meant by the term "singularity". Isn't that why 
they name it after that word? The formulas fall down?

QM has its own singularities: if you take it all the way down to size zero, 
you get infinities in the sums. Feynman got his Nobel for proving you don't 
have to go down to zero, and regardless of where you stop approaching the 
limit of zero, you get the same answer (within tolerance of course).

So there's a singularity in QM in the same place there is in GR, in some 
sense - you can't do the QM formulas without freedom of motion, which 
doesn't happen at the singularity in a black hole.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Warp <war### [at] tagpovrayorg> wrote:
>   Actually it would work if the black hole was moving towards us. Then
> the spacecraft could go there and rob part of this momentum and get a
> speed boost back towards Earth.

Well, for the sake of the original argument, I think you're wrong here: It
wasn't about a speed *boost*, but just using the black hole to "swing around"
and not lose any of the momentum that got us there in the first place.

Though you may be right that for the sake of this maneuver, *any* black hole not
sufficiently "static" with respect to us would be a bad choice. I didn't check
the math.

Then again, I think yours is wrong as well: With that black hole being
sufficiently heavy and having a speed of V, if we head there with a speed v, we
should be bouncing back at a speed of (roughly) v' = V-v (with no significant
influence of the hole's mass remaining), as long as neither of us is going
relativistic.

So it should suffice to find a black hole significantly slower than our
spacecraft.


>   Remember: When the Shoemaker-Levy was on collision course against Jupiter,
> tidal forces broke it in 9 parts well before it reached the surface. And
> Jupiter is a lot less massive than the Sun.

I'd expect it to depend a good deal on (a) how elastic the thing is, and (b) how
fast the thing is rotating around itself: When rotating fast, the tidal forces
not only tear at the electromagnitic "links" between the molecules and atomic
particles, but keep distorting the shape of the object, and I guess an overdose
of squishing and squashing kills an object a lot faster than the tidal forces
themselves.

It's similar to a tyre with not enough air pressure: As long as you don't move
your car, nothing bad will happen to it. But if you drive around with it too
fast, the squishing and squashing will heat it up, so it may ultimately break
up like that comet...

So, in this sense, the Shoemaker-Levy comet wasn't torn apart by tidal forces,
but was killed by RSI :)


>   They don't emit anything, but by their nature as being really massive
> objects they surely tend to aggregate lots of nasty stuff orbiting around
> them, and this stuff often emits large amounts of radiation by several
> means.

Well, would they aggregate more stuff than a massive star? (Assuming we're
talking about "star-sized" holes here)


>   For example one concern about sending probes to orbit Jupiter is the
> large amount of radiation there (which could break electronics if not
> shielded properly). Jupiter, as a very massive object, gathers tons of it.
> And Jupiter is a lot less massive than a normal black hole.

Maybe that's due to a magnetic field of Jupiter? Sort of a "Van Allen Belt,
XXL-size"?

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> So since the person falling in will never see himself cross the EH (because
> his time slows), and the person outside will never see him cross, then stuff
> falling into a black hole does *not* fall into the singularity. Nothing
> crosses the EH, so nothing gets compressed into the singularity, yes?

The problem here is the frame-of-reference thing.

An outside observer will see the "victim's" clock slow down.

The "victim" will not notice, so what will he see? From his point of view, he'll
reach the EH in finite time, so depending on what happens then, he *may* see
himself falling in.


> (Discounting the black holes that have paths to the singularity that don't
> cross an EH, of course.)

How could that be?

Post a reply to this message

clipka wrote:
> The "victim" will not notice, so what will he see? From his point of view, he'll
> reach the EH in finite time,

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?

>> (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.)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> If his clock slows to zero on the outside and he never crosses the event
> horizon, then the next tick of the clock is infinitely far in the future of
> the universe, yes?  So he never experiences crossing the EH because it takes
> forever for his clock to tick.  Say the black hole evaporates after a
> billion years - does the space ship ever hit the singularity?

Remember Achilleus and the turtle!

Post a reply to this message

clipka wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> If his clock slows to zero on the outside and he never crosses the event
>> horizon, then the next tick of the clock is infinitely far in the future of
>> the universe, yes?  So he never experiences crossing the EH because it takes
>> forever for his clock to tick.  Say the black hole evaporates after a
>> billion years - does the space ship ever hit the singularity?
> 
> Remember Achilleus and the turtle!

But the universe is still around when Achilleus passes the turtle. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka <nomail@nomail> wrote:
> Then again, I could turn my speculation indeed into an objection: As of now, no
> singularity (i.e. a condition where a formula gives "infinity" as an answer)
> predicted by any scientific theory has ever been observed in true life.

  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.

  There are basically two choices:

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.

  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.

  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.

-- 
                                                          - Warp

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> If his clock slows to zero on the outside

  "On the outside" means "from the point of view of an external observer".
In other words, someone far away from the influence of the black hole,
looking at the falling clock.

  The observer who falls into the black hole *with* the clock will
perceive it normally. (Well, relatively speaking. Let's forget for
a moment the space-warping.)

> and he never crosses the event 
> horizon, then the next tick of the clock is infinitely far in the future of 
> the universe, yes?

  From the outside perspective.

>  So he never experiences crossing the EH

  The observer who is falling into the black hole does experience the
crossing.

-- 
                                                          - Warp

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> 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.)

  If I remember correctly, for a rotating black hole the singularity
will have a torus shape (with a minor radius of zero). The faster it
rotates, the larger the torus. I might remember this wrongly, though.

  Likewise the event horizon elongates, and if it rotates fast enough,
might even get some kind of torus shape itself as well, or something
like that.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> clipka <nomail@nomail> wrote:
>> Then again, I could turn my speculation indeed into an objection: As of now, no
>> singularity (i.e. a condition where a formula gives "infinity" as an answer)
>> predicted by any scientific theory has ever been observed in true life.
> 
>   Lack of evidence is not evidence of the contrary. 

If course it is.  It's not *proof*, but it's certainly evidence.

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. :-)

> 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.

That would assume that QM is broken, and there's little evidence to show 
*that* would be so. :-)

> 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.

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

But it has been fun talking about it, because I think I understand better 
what the problem is.

> long as viable theories

... which is where we came into the thread. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Warp wrote:
>   The observer who is falling into the black hole does experience the
> crossing.

OK. Maybe I'm just incapable of understanding this. :-)  But yes, I get a 
glimmering of what you're saying. That whole lack of simultaneity.

But if he's still emitting photons when the black hole evaporates, it would 
seem to be rather paradoxical even for GR.

If he never crosses the EH as seen from outside, and the black hole is (say) 
only one stellar mass, then the outside observer will see the hole evaporate 
(thus eliminating the EH) before the spaceship actually crosses the EH.

It would seem the occupant would think he *did* cross the EH, while those 
outside would have a constant view of the occupant outside the EH.

Plus, the occupant *can* look out and conceivably see what the universe 
looks like even after he's past the event horizon, which would imply the 
universe hasn't ended for *him*?

(Modulo the space ship being bigger than the black hole physically, if it 
is, and that "constant view" would be very intermittent, and I may be 
misremembering how big a hole needs to be to be stable. Ignore that bit for 
now. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> But if he's still emitting photons when the black hole evaporates, it would 
> seem to be rather paradoxical even for GR.

  GR doesn't predict black hole evaporation. It's those quantum mechanists
messing around.

> If he never crosses the EH as seen from outside, and the black hole is (say) 
> only one stellar mass, then the outside observer will see the hole evaporate 
> (thus eliminating the EH) before the spaceship actually crosses the EH.

  Thinking about it, this is probably what would happen:

  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.

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

> Plus, the occupant *can* look out and conceivably see what the universe 
> 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.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> But if he's still emitting photons when the black hole evaporates, it would 
>> seem to be rather paradoxical even for GR.
> 
>   GR doesn't predict black hole evaporation. It's those quantum mechanists
> messing around.

Good point. :-)

> reach the external observer in finite time. The external observer will
> end up actually "seeing" the falling object cross the EH.

Hmmm... Yes, that's possible.

>   I don't think that's possible. When he is exactly at the EH, the entire
> EH engulfs the entire view on all sides.

Even straight up?   And again, QM comes in there, as there might be 
uncertainty in the sense of what is it that's "straight up"?

I don't know either. By now, I'm entirely in BS mode. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> >   I don't think that's possible. When he is exactly at the EH, the entire
> > EH engulfs the entire view on all sides.

> Even straight up?

  Perhaps you see an infinitely small, very blue-shifted point.

>   And again, QM comes in there, as there might be 
> uncertainty in the sense of what is it that's "straight up"?

  The opposite direction of where gravity is pulling you. :)

-- 
                                                          - Warp

Post a reply to this message

Warp escreveu:
> Darren New <dne### [at] sanrrcom> wrote:
>> Plus, the occupant *can* look out and conceivably see what the universe 
>> 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.

I think I'm finally understanding what Darren means.

If time slows down nearing a massive graviational field and an external 
observer sees the voyager freezing as he aproaches the EH, but still for 
him time would be the same as always, except perhaps he would see the 
external observer and the rest of the universe behind going by extremely 
faster as ages go by until eventually getting out of view once passing 
the EH.

The question Darren seems to pose is:  does it get an eternity for the 
voyager to get through the EH?  I believe not, even in the so called 
supermassive blackholes supposedly in the center of galaxies.  Spacetime 
dilatates near the EH, but don't become infinite (except in the 
singularity).  So, if we think otherwise we come to the turtle and 
Achilleus tale.

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...

Post a reply to this message

nemesis wrote:
> The question Darren seems to pose is:  does it get an eternity for the 
> voyager to get through the EH?  

Something like that. Complicated by the question "who is asking?" :-)

Another interesting thought I saw somewhere:

The cosmological horizon is not unlike an event horizon - things moving 
towards it are going faster and faster relative to us, and hence are slowing 
down time-wise[1].  Perhaps the background microwave radiation is really 
just all the galaxies that used to be close red-shifted waaaaay down as they 
pile up near the border of the observable universe.



[1] Do they really slow down (for us) if their speed is caused by new space 
being created?  I have no idea, but from what I know of it, I think the 
answer is "yes".

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

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.

Post a reply to this message

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.

Post a reply to this message

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.

Post a reply to this message

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".

Post a reply to this message

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 ;)

Post a reply to this message

>  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.

Post a reply to this message

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.

Post a reply to this message

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...

Post a reply to this message

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 :))

Post a reply to this message

"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)...

Post a reply to this message

BTW, just a quick thought on the information paradoxon associated with black
holes:

Thinking about it, this is actually a non-issue.

Doesn't QM say (at least in some interpretations) that a particle's properties
are not determined until it interacts?

So assume a particle actually falls into a black hole; Is any information lost?
No - because it can no longer interact with anything; so its properties were
still undetermined when it fell in. So there goes a memory storage location,
but it wasn't used.

Why wasn't it used? Well, because all information it had before was passed on to
the last particle it interacted with.

But each particle can only store so much bits of information, so where did the
information go *that* particle carried? Simple: There wasn't any in it. After
all, the only thing it interacted with was a particle that is lost, so we have
no way of checking how it influenced that particle; so those properties cannot
be (indirectly) observed either - and were hence still undefined when it
interacted.

And so on.

So as it seems, a lot of matter out there is actually just unused spare memory,
ready to back-up information of other particles doomed to fall into black
holes... the queer thing is, we don't know *which* particles are used and which
aren't...

Post a reply to this message

clipka <nomail@nomail> wrote:
> 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.

  Why? Exactly how does that happen?

-- 
                                                          - Warp

Post a reply to this message

clipka escreveu:
> 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...

Yeah, great useful ideas may actually germinate thanks to it. :)

Post a reply to this message

clipka escreveu:
> 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?

Well, if we can believe that matter and energy began out of nothing with 
a Big Bang, why not believe it can suddenly come out of existence with 
all but silence and darkness? :P

> 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...

Perhaps only Phil Connor would know. :P

> 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:

hehe, are you sure you're not a mere crackpot? ;)

http://math.ucr.edu/home/baez/crackpot.html

> - 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!

Perhaps we get to know a universe in one single dimension?  "Hey, Phil, 
long time no see!  Somewhat overcrowded here, huh?"  well, except time 
wouldn't exist and so everything would be at the same time (damn word!). :P

Perhaps everything at the same time is nothing but a blur, a nothing. 
And this is my daily contribution of BS... :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.

Yes.

>>   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.

Now that it's being considered that our universe could be a hologram, 
perhaps it's nothing but the slot to the credit card machine?  Freedom 
at last! :P

Well, I think we got into some wild scifi scenarios here and I'll be 
munching all of it away for quite a few time... :D

Post a reply to this message

Warp <war### [at] tagpovrayorg> wrote:
> > 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.
>
>   Why? Exactly how does that happen?

Suppose for argument's sake that the BH just suddenly happens to shrinks to half
its mass.

What happens to the EH? Simple: It recedes. A BH with less mass has a smaller
Schwartzschild radius.

What happens to the gravity well? Simple, too: Its slope gets less dramatic
where the EH used to be. Still catastrophic where the EH is *now*.

What happens to the point where the victim was "hanging out"?

Now this gets a bit more tricky. I'll present two approaches that sound
plausible to me; both would come to the conclusion I presented, and I guess
actually both would happen at the same time:

(a)

What does a "gravity well" mean? Well, it's distorted spacetime. I imagine it as
"compressed". So let's for the sake of argument use a very simplistic image;
say, a BH would just influence a radius double its EH radius, and the space
between that distorted linearly.

So let's assume that the "victim" has fallen 99% along this slope (he has had
enough time to do that), so he's just 1% of the EH radius away from the EH,
when all of a sudden the black hole goes on a diet: Pop! here goes the EH
radius to, say, half its diameter.

Space further away gets "un-distorted" - actually all the space up to the old EH
radius. But that's only the part up to 50% along the old slope. The remaining
50% are still "downhill", with our victim still on this slope. 98% along it,
actually. So 2% of the new EH radius away from the new EH.

So for practical purposes, he has almost exactly moved along with the receding
EH.

Note that in reality, the distortion close to the EH would be much stronger than
further away, and the "un-distortion" effect would be much weaker for areas very
close to the EH than for areas further away.

(b)

What would happen if the EH would suddenly recede and spacetime getting somewhat
"un-distorted", and our victim would *not* follow the EH?

Well, in that case, from an outside observer his wristwatch would speed up
again. But then what? Remember what the poor old sod was busy with when we left
him hanging at the edge of the EH? Right: Falling straigt towards the black
hole! So what will he do now in his newly recovered spare time? Um... continue
falling I guess...

So if the receding EH would also recede from our poor sod, he'd *very* quickly
catch up with it...


I guess both effects will happen, and they will combine. So there's reason
enough to believe that even as the EH recedes, that guy will still keep hugging
it, bound in eternal love... ("Oh darling, why can't this moment last forever!")

Post a reply to this message

clipka escreveu:
> 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.

Indeed.  And thanks for the info, I was afraid he was son of 
Schwarzzenegger or something. :P

Post a reply to this message

clipka <nomail@nomail> wrote:
> What happens to the point where the victim was "hanging out"?

  The victim was not "hanging out" anywhere. There were simply some
leftover photons there, going out (with asymptotically lessening frequency).

  When the event horizon recedes, these leftover photons will be in a
less strong gravity field and will thus get a boostup. The photons which
were almost touching the EH will now be farther away, and will get out
in less time.

-- 
                                                          - Warp

Post a reply to this message

nemesis <nam### [at] gmailcom> wrote:
> Perhaps only Phil Connor would know. :P

Maybe - I don't know *him*... should I?


> hehe, are you sure you're not a mere crackpot? ;)
>
> http://math.ucr.edu/home/baez/crackpot.html

Hm.... let's check this out (BTW, I'm a fan of JOAN Baez, so it must be good
;))...


.... uh-oh! Looks like I'm making a *really poor* crackpot... a few points from
the first items, but I utterly fail at the real challenges...

I guess we *all* have to train still a bit more to qualify ;)

(We didn't even get into a flamewar about this... that's really poor! :P)

> Perhaps we get to know a universe in one single dimension?  "Hey, Phil,
> long time no see!  Somewhat overcrowded here, huh?"  well, except time
> wouldn't exist and so everything would be at the same time (damn word!). :P

The good thing is that it wouldn't last long :)

> Now that it's being considered that our universe could be a hologram,
> perhaps it's nothing but the slot to the credit card machine?  Freedom
> at last! :P

Yeah... so next step would be a few bit shift registers, accumulators, and - ah!
There you go: Correct pin, so spit out them greenbacks... :P

Post a reply to this message

nemesis <nam### [at] gmailcom> wrote:
> clipka escreveu:
> > 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.
>
> Indeed.  And thanks for the info, I was afraid he was son of
> Schwarzzenegger or something. :P

Just googled around a bit. Looks like Arnold "Arnie" Schwarzenegger (just one
"z" BTW) bears a surname derived from a Swiss location called "Schwarzenegg",
which in turn might translate to "black corner/region" or something alike.

Another BTW: With contemporary German orthography, "Schwartzschild" would lose
the "t" in his name... like "Rothschild" (which is "Redshield") would lose the
"h"...

..... I must confess though that this information has absolutely *nothing* to do
with black holes or cosmology or anything remotely close :P

(... except if you're opting for a holistic view on our universe ;))

Post a reply to this message

Warp <war### [at] tagpovrayorg> wrote:
> > What happens to the point where the victim was "hanging out"?
>
>   The victim was not "hanging out" anywhere. There were simply some
> leftover photons there, going out (with asymptotically lessening frequency).

No, there's not enough space "wrapped up" to keep them there. It's instead the
phenomenon of time dilation - the fact that time is "wrapped up" there as well
(after all, it's the *spacetime* that is warped) - that produces the effect.

From an outside observer's frame of reference, the victim not only *appears* to
be "hanging out there", he still physically *is*.

Maybe I'll draw a picture this weekend to illustrate what I mean.

Post a reply to this message

clipka wrote:
> 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 ;)

Yes. The proper expression is "absence of proof is not proof of absence." 
But evidence certainly is. http://en.wikipedia.org/wiki/Bayes%27_theorem

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

I think we've all acknowledged that repeatedly. :-)

>> 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 ;)

Yup.  Except that wouldn't nearly be as sarcastic. ;-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka wrote:
> Doesn't QM say (at least in some interpretations) that a particle's properties
> are not determined until it interacts?

Some are, some aren't.  A photon is always positively charged whether you're 
measuring it or not. Only the properties that are orthogonal (i.e., 
"uncertain") are indeterminate.

> So assume a particle actually falls into a black hole; Is any information lost?

I'm told there is. :-)

> And so on.

Nice thought, but again, I personally am willing to take the word of people 
like Hawking over my own understanding of QM. :-)

> So as it seems, a lot of matter out there is actually just unused spare memory,
> ready to back-up information of other particles doomed to fall into black
> holes... the queer thing is, we don't know *which* particles are used and which
> aren't...

Cute.  Sounds like a good SF story.

Oh, wait, already did one. Permutation City by Greg Egan. Highly 
recommended. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka <nomail@nomail> wrote:
> From an outside observer's frame of reference, the victim not only *appears* to
> be "hanging out there", he still physically *is*.

  How is he "physically" there? The external observer can't touch him nor
communicate with him.

-- 
                                                          - Warp

Post a reply to this message

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

My favorite personal random idea is ... what if we really *are* at the 
center of the universe, and everything really *is* moving away from *us*?

What if we happen to be near the very peak of a big curve of space-time, and 
everything else is rolling faster and faster down the big hill away from us, 
while we're perched at the top?

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

I saw a great line:  "Of *course* God put the Earth in the center of the 
universe. That's why all the stars shine *towards us*!"

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka wrote:
> in a collapsing superstar, maybe this is sufficient to slam two fermions
> together into the same quantum state,

I'm pretty sure that's not how it works. It isn't like pushing two magnets 
together, where if you just squeeze hard enough, you overcome the 
resistance. There's no interaction between the fermions keeping them apart - 
rather, there's no pair of paths that both end at the same place that don't 
cancel each other out.

It's like waves, I guess. No matter how hard you try, you can't combine 
sin(t) and -sin(t) and wind up with a wave. It's not a matter of squeezing 
them real hard - they just cancel out.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

nemesis wrote:
> Perhaps we get to know a universe in one single dimension?  "Hey, Phil, 
> long time no see!  Somewhat overcrowded here, huh?" 

"In the beginning, before the big bang, my friends and I all hung out with 
each other. I mean, where else was there to go?"

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka wrote:
> So if there's no EH, you can just zip straight through the singularity?

I think it's more that you can see things coming out of the singularity.

> actually decide to turn around any time? Speaking of which, how will time be
> affected near the singularity?

Dunno. Complex math.

> 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.

Yep. And if you fly through the hole, you wind up ... somewhere else.

-- 
   Darren New, San Diego CA, USA (PST)
   "Ouch ouch ouch!"
   "What's wrong? Noodles too hot?"
   "No, I have Chopstick Tunnel Syndrome."

Post a reply to this message

clipka escreveu:
> nemesis <nam### [at] gmailcom> wrote:
>> Perhaps only Phil Connor would know. :P
> 
> Maybe - I don't know *him*... should I?

Ever seen "Groundhog Day" with Bill Murray?  A classic. :)

> Yeah... so next step would be a few bit shift registers, accumulators, and - ah!
> There you go: Correct pin, so spit out them greenbacks... :P

or that! :D

Post a reply to this message

Darren New escreveu:
> clipka wrote:
>> Maybe what we see isn't the "big bang" after all, but the "big crunch"?
> 
> My favorite personal random idea is ... what if we really *are* at the 
> center of the universe, and everything really *is* moving away from *us*?

Shouldn't then we not see them above the peak?  Oh, alright, spacetime 
is curved and light would also bend and come from the sides and seem to 
be right above our heads fooling us into thinking the universe is 
roughly spherical.

> I saw a great line:  "Of *course* God put the Earth in the center of the 
> universe. That's why all the stars shine *towards us*!"

Well, it's all relative to the observer, so from our point of view the 
universe indeed revolves around us.  Actually, to the common man in the 
streets -- whose view at nights is occluded by both smog polution and 
city lights so he doesn't really take the time to look up the few 
blinking stars so far away and so static -- the universe revolves around 
mundane job, bills and society's many rituals. :P

Post a reply to this message