Warp escreveu:
> nemesis <nam### [at] gmailcom> wrote:
>> We're actually cruising unknown frontiers at speeds vastly superior to 
>> 200km/sec
> 
>   With respect to what?
> 
>   Motion is always relative.
> 
to the center of the galaxy?

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Warp escreveu:
> nemesis <nam### [at] gmailcom> wrote:
>> Which also begs the philosophical question of whether passing 
>> through the EH leads to a whole new universe beginning from yet another 
>> big bang...
> 
>   I don't think the spacetime geometry inside the event horizon of a
> black hole would allow for a universe to exist in there.

In there or out there? ;)

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nemesis escreveu:
> Warp escreveu:
>> nemesis <nam### [at] gmailcom> wrote:
>>> Which also begs the philosophical question of whether passing through 
>>> the EH leads to a whole new universe beginning from yet another big 
>>> bang...
>>
>>   I don't think the spacetime geometry inside the event horizon of a
>> black hole would allow for a universe to exist in there.
> 
> In there or out there? ;)

I believe the singularity could only get a proper artistic rendering 
from Escher. :)

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nemesis <nam### [at] gmailcom> wrote:
> Warp escreveu:
> > nemesis <nam### [at] gmailcom> wrote:
> >> We're actually cruising unknown frontiers at speeds vastly superior to 
> >> 200km/sec
> > 
> >   With respect to what?
> > 
> >   Motion is always relative.
> > 
> to the center of the galaxy?

  Well, I suppose that since we are in a rotating frame of reference, and
given that it's physically possible (at least in theory) to determine an
inertial frame of reference centered at the center of our galaxy, we could
be moving at that speed with respect to this inertial frame of reference.

-- 
                                                          - Warp

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Darren New escreveu:
> clipka wrote:
>> Talk about atoms - the ancient greeks "invented" them. 
> 
> Yes, and they also didn't believe in irrational numbers even after they 
> were proved to exist. So I don't think you can pick one success out of 
> history and call it a "prediction".
> 
> I mean, there's really only two or three possibilities: Stuff is atoms, 
> stuff is continuous, stuff is a mixture. :-)
> 
> The greeks had no evidence of atoms, as far as I know. It was just a 
> guess. It wasn't until Mendeleev (or the work that lead up to the 
> periodic table) or so that people actually had evidence that atoms were 
> the right answer.

Indeed.  And atoms are not even atomic in the original sense of the 
greek word... ;)

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nemesis wrote:
>  holding your cup of coffee with a steady hand... :P

... which only means you need more coffee.

-- 
   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 wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> You'd wind up changing the course of the black hole much less than you'd 
>> change the course of your spaceship, is all.
> 
>   The black hole would have to be moving towards the general direction
> of Earth, in that case.

I don't have the math to be sure that's true.  Wouldn't it be possible to 
make it moving away less quickly?

I mean, certainly if there's a solid object moving away from you, you can 
land on it and jump off and go up. Stand on a trampoline going 1 MPH 
downwards - can you jump up?

You might be right, tho, if there's no physical contact, but as I say I 
don't want to learn the math to figure it out. :-)

>   But you get tons of other problems, as I described in my post. :P

Yah. I posted before I read that, methinks.

>   As very massive objects, and ones usually formed from collapsing stars
> (the collapse leaving behind tons of stuff), I think it would be rather
> difficult to find "naked" black holes, without the accompanying stuff.

Unless you manufactured it yourself, yes. :-)

-- 
   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:
>   If someone objects to the notion of a singularity, he would have to show
> some evidence that GR doesn't work as predicted in this case. There must be
> some property of the Universe which makes GR not work in this situation,
> something which actually stops the singularity from forming. What could this
> phenomenon be? Has anyone ever measured such phenomenon to exist?
>
>   If not, then any objection against singularities is more or less
> philosophical. "It doesn't sound right" is not hard science.

I'm not saying "it doesn't sound right" - I'm saying I *believe* something else
;)

It wasn't meant to be a scientific statement or any other claim of truth in the
first place. Just a purely philosophical statement amidst an otherwise
dominated by science and wild thoughts...


I believe science will find that GR is wrong close to its singularities,
because... well, because I love the idea that there might be some
mind-bogglingly simple way of looking at both GR and QM, which science just
hasn't been imaginative enough to discover ;)


>   The thing is, if GR equations are right, and there is a lot of evidence
> suggesting that they are, then there simply is no way for a singularity
> to not to form when a mass collapses to be smaller than its Schwarzschild
> radius. All geodesics inside the event horizon, including time geodesics,
> point towards the center. There's no known way for matter/energy to stop
> going towards this center. Just advancing in time makes it advance towards
> this center. Even if you tried to apply some force to a particle to stop
> it from getting closer to the center, you couldn't, not even if you applied
> an infinite force.

Hm - let's take this a step further, and salt it with a bit of quantum thinking
(which has successes of its own):

- 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.

- If particles can't *interact*, there is no way to measure time; so the time a
particle would take from entering the EH until it reaches the center would be
"mu" (in the Zen sense, not some greek-lettered constant).

- If the equations say that as soon as a particle crosses the EH it will head
straight towards the center within a time of "mu", then it *might* be a hint
that the EH is *identical* with the center after all...


>   The only possible conclusion is that all the matter and energy compresses
> into a point of zero volume.

No - this is the most *straightforward* conclusion. But being straightforward,
it may hinder thinking along other lines, so I choose to discard it and let my
imagination run wild.

Occam's razor is a good tool, but applying it to some "brainstorming" will just
kill inspiration.

It's also a good thing to occasionally check whether the concept once regarded
as "most simple" actually still *is* the most simple.


> If the singularity does not form in reality,
> then something must explain why. Something more than philosophical
> objections.

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


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. In
fact, various theories that predicted singularities have been *proven* to be
inconsistent with reality exactly at or close to these conditions. Therefore,
it is reasonable to assume that singularities predicted by scientific theories
actually indicate that the theory *fails* at these conditions.

This resoning is actually not philosophical in nature, but rather very
scientific, and may qualify for a theory in its own right. The statement is
clear: "If the formulae derived from a theory in the domain of natural science
result in "infinity" values for certain conditions, then it is invalid for
these conditions." Predictions can be easily derived from it, e.g. "The GR does
not accurately describe the conditions within the EH of a black hole". In this
case, putting the predictions to the test might be problematic, but I guess
other theories can be found.

Of course one must be careful with this reasoning. Finding that a theory
predicts singularities doesn't mean the theory as a whole msut be at fault - it
just should be taken as a warning to be careful about predictions made by the
theory close to these conditions. In fact, a theory may be perfectly fine
except *exactly* at these conditions. And, after all, this reasoning is just
another theory, so it *may* be wrong after all. But from evidence seen so far,
I guess it can be considered quite robust.

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> QM also 
>> says you can't have two fermions in the same quantum state in the same 
>> place.
> 
>   At least not in normal, almost-cartesian space, with extremely weak
> gravity.
> 
>   How about inside space which is so curved that it forms an event
> horizon because of a practically infinite gravity?-)

AFIAK, gravity's effect is so weak in QED at least that nobody knows how it 
affects things.

Note that I'm not saying "you can't have two fermions in the same state." 
I'm saying that's what QM says. And since it conflicts with GR's 
predictions, one of the other needs to be adjusted, unless you can prove 
that you can't prove either one is right.

Sure, it's possible that QM breaks down in extremes of GR, just like it's 
possible GR breaks down at extremes of QM.  I'm not saying one is right or 
the other. I'm saying it's not just "philosophical objections" to 
singularities, but actual mathematics that matches experimental measurements 
to 15 decimal places.

(I think gravity is something like 40 decimal places out, tho, so it's 
certainly possible QM isn't taking account of it properly.)

>   Under such pressures matter degenerates. Do fermions even stay as
> fermions, or do they degenerate to something more elemental? Something
> which might not be bound to QM laws?

It's entirely possible that's what happens.

>   Gravity is in effect also at subatomic levels, even though it's often
> ignored because it's so weak in normal circumstances.

Yep. And QM is in effect at levels the size of a star, similarly. :-)

>>> There's no known way for matter/energy to stop going towards this center. 
> 
>> You wouldn't think a single electron could be larger than a house, either, 
>> but they've done that in a laboratory.
> 
>   "You wouldn't think" is different from "there's no known way". The
> former is something related to my intuition. The latter is related to
> current scientifical global knowledge.

Sure. I was simply addressing your "philosophical objection" bit. :)

And there *is* a known way for it to stop going towards the center: QM.

If either of us knew whether GR or QM was more right in this situation, we'd 
already been in Stockholm picking up our prize. :-)

-- 
   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:
>   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...

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