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."

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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."

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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.

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

LOL

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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."

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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"?

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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?

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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."

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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!

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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."

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