| Topic: |
Science > Physics |
| User: |
"CWatters" |
| Date: |
26 Jul 2005 07:55:49 AM |
| Object: |
Black holes |
Just a daft question that occured to me...
Could a hollow black hole form if the right amount of matter collided in the
right way? Probably tricky to arrange but possible or not?
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| User: "Ben Rudiak-Gould" |
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| Title: Re: Black holes |
26 Jul 2005 03:07:35 PM |
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CWatters wrote:
Could a hollow black hole form if the right amount of matter collided in the
right way?
I have no idea what a "hollow black hole" is. If you mean a black hole
without mass, there's no such thing. If you mean a naked singularity,
there's been some work suggesting that GR might allow them, but no one
really knows.
-- Ben
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| User: "CWatters" |
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| Title: Re: Black holes |
26 Jul 2005 03:23:17 PM |
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"Ben Rudiak-Gould" <br276deleteme@cam.ac.uk> wrote in message
news:dc656i$nub$1@gemini.csx.cam.ac.uk...
CWatters wrote:
Could a hollow black hole form if the right amount of matter collided in
the
right way?
I have no idea what a "hollow black hole" is. If you mean a black hole
without mass, there's no such thing. If you mean a naked singularity,
there's been some work suggesting that GR might allow them, but no one
really knows.
My (limited) understanding is that a BH forms when you have enough mass
compressed into a small space. Perhaps if you had some matter that started
out orbiting a point.. ..
0 0
0 0
0 0
When it comes together..
0 0
0 0
0 0
00
0 0
00
Could you end up with the critical density being reached uniformly around
the edge but not in the middle? Obviously it unlikely and it wouldn't last
long but is it possible or interesting? What would the middle region be
like?
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| User: "G=EMC^2 Glazier" |
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| Title: Re: Black holes |
26 Jul 2005 05:10:52 PM |
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Ben No hollow planets meteors or any macro object. Gravity sees to it.
The only hollow object I can think of is a bucky ball.and that's in the
micro realm If a black hole was hollow it would have no center of
gravity,and all its gravity force would be the combined area of its
surface. If spinning very fast the center of gravity would be its poles.
Bert
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| User: "Jeff_Relf" |
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| Title: Hawking_Radiation, Unruh_Radiation, gavity and Space_Time_Entropy. |
26 Jul 2005 04:34:48 PM |
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Hi C_Watters and Ben_Rudiak_Gould,
C_Watters postulated that some black hole's could be hollow,
not understanding that black holes always dissipate before they fully form.
See Hawking_Radiation:
http://en.wikipedia.org/wiki/Hawking_radiation
The universe has only a finite lifespan before entropy,
i.e. intrinsic dissipation, makes it a virtually perfect vacuum.
See Entropy:
http://en.wikipedia.org/wiki/Entropy
Further, observers on earth will never see a fully_formed black hole because
it'd require a virtually infinte amount of time, in our frame, to form.
See Black_Holes:
http://en.wikipedia.org/wiki/Black_Holes
All the same, in the black hole's local frame, it's just a supernova,
requiring only a few seconds to dissipate.
A virtually infinite gavitational energy at a virtual event_horizon
is not possible. See Unruh_Radiation:
http://en.wikipedia.org/wiki/Unruh_radiation
Remember, intrinsically, time is a spatial, not temporal, dimension.
Further, I posit:
1. Physical processes determine absolutely everthing.
So free_will is ever Virtual, never real.
2. Entropy is the fifth Spatial dimension.
Although that's hard to see anywhere but at cosmic scales,
like time, entropy is parochial and static,
and intrinsic property of mass_energy.
3. Gravity is merely a remnent of
the higher densities of space_time that once were.
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| User: "Anthony Cerrato" |
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| Title: Re: Hawking_Radiation, Unruh_Radiation, gavity and Space_Time_Entropy. |
26 Jul 2005 06:43:44 PM |
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"Jeff_Relf" <Me@Privacy.NET> wrote in message
news:Jeff_Relf_2005_Jul_26_8Kvg@Cotse.NET...
Hi C_Watters and Ben_Rudiak_Gould,
C_Watters postulated that some black hole's could be
hollow,
not understanding that black holes always dissipate before
they fully form.
See Hawking_Radiation:
http://en.wikipedia.org/wiki/Hawking_radiation
The universe has only a finite lifespan before entropy,
i.e. intrinsic dissipation, makes it a virtually perfect
vacuum.
See Entropy:
http://en.wikipedia.org/wiki/Entropy
"The universe has only a finite lifespan before entropy..."
Where do you get this? AIUI, the universe likely has an
_infinite_ lifespan before becoming fully entropic;
otherwise, it's fate is not known (provable) either way.
"...black holes always dissipate before they fully form."
This very semantically philosophical statement depends
completely on the ref. frame of the observer. AIUI, for a
distant observer the BH will appear to come to a dead stop
in time as the BH formation proceeds and its light shifts
into red-shift invisibility. To a local observer almost at
the event horizon, the BH would fully complete its formation
since its time flow rate goes to infinity relative to that
of the distant observer.
Do you not agree? ...tonyC
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| User: "Jeff_Relf" |
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| Title: Time dilation and length contraction. |
26 Jul 2005 09:39:04 PM |
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Anthony_Cerrato, EKPhm, _BOa6iK, D Glorb.COM, Microsoft, 26, 4.43 P
Hi Anthony_Cerrato, C_Watters and Ben_Rudiak_Gould,
I wrote:
The universe has only a finite lifespan before entropy,
i.e. intrinsic dissipation, makes it a virtually perfect vacuum.
See Entropy: http://en.wikipedia.org/wiki/Entropy
Cerrato replied:
" The universe has only a finite lifespan before entropy..."
Where do you get this ? AIUI, the universe likely has an
_infinite_ lifespan before becoming fully entropic;
otherwise, it's fate is not known ( provable ) either way.
Recent supernovae data suggests that the net mass_energy of the universe
is virtually negative, i.e. space_time is hyperbolic, not flat or closed.
Going back 12 billion years or so,
there's been a fairly Constant acceleration in the expansion of space_time.
But much, much more/better supernovae data is needed.
Because of this data, Einstein's so_called greatest_blunder,
lambda, a.k.a. the Cosmological_Constant,
has become part of the leading model, the Lambda-CDM model.
I don't know what the lifespan might be, maybe 10 ^ 9999 years or something,
but it's certainly not infinite,
at least as far as human_like observers are concerned.
Plenty of high_precision data, including NASA's WMAP, say that space,
independent of time, is perfectly flat and homogenouos,
i.e. our universe has no center of gravity:
http://map.gsfc.Nasa.GOV/m_mm/mr_content.html
WikiPedia says:
Adding a cosmological constant to the standard theory of cosmology
...has led to a model for cosmology known as the Lambda-CDM model.
This model is in very good agreement with
established cosmological observations.
__ http://en.wikipedia.org/wiki/Dark_energy
and:
In spite of its problems, the cosmological constant is in many respects
the most economical solution to the problem of cosmic acceleration.
One number successfully explains a multitude of observations.
Thus, the current standard model of cosmology, the Lambda-CDM model,
includes the cosmological constant as an essential feature.
__ http://en.wikipedia.org/wiki/Dark_energy#The_cosmological_constant
I wrote:
Observers on earth will never see a fully_formed black hole because
it'd require a virtually infinte amount of time, in our frame, to form.
See Black_Holes: http://en.wikipedia.org/wiki/Black_Holes
All the same, in the black hole's local frame, it's just a supernova,
requiring only a few seconds to Totally dissipate.
A virtually infinite gavitational energy
at a virtual event_horizon is not possible.
See Unruh_Radiation: http://en.wikipedia.org/wiki/Unruh_radiation
Cerrato replied:
"...black holes always dissipate before they fully form."
This very semantically philosophical statement depends
completely on the ref. frame of the observer.
AIUI, for a distant observer the BH
will appear to come to a dead stop in time as the BH formation proceeds
and its light shifts into red-shift invisibility.
To a local observer almost at the event horizon,
the BH would fully complete its formation
since its time flow rate goes to infinity relative to that
of the distant observer. Do you not agree ?
Distant human_like observers, living the life of the universe,
would never see any fully_formed black holes.
They'd explode first, because they'd all be smaller than the universe.
See Hawking_Radiation: http://en.wikipedia.org/wiki/Hawking_radiation
So the local observer would Also never see a fully formed black hole,
for the Exact same reason.
The SI second and meter have very exact definitions
which are subjected to Relative time dilation and length contraction.
So, instead of the distant observer's aeons of Hawking_Radiation,
he'd see just a few seconds of Unruh_Radiation, dissipating everything away.
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| User: "Dogma Discharge" |
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| Title: Re: Black holes |
26 Jul 2005 08:18:33 AM |
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NOT
--
Kind Regards
Cameron
"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:ppqFe.153951$_Q1.8155251@phobos.telenet-ops.be...
Just a daft question that occured to me...
Could a hollow black hole form if the right amount of matter collided in
the
right way? Probably tricky to arrange but possible or not?
.
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