Light inside a black hole?

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (5 Jan 2007 07:45:35 -0800) it happened "dlzc"
wrote in . com:

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (Fri, 5 Jan 2007 09:31:03 -0500) it happened "Greg Neill"
wrote in
:

"Jan Panteltje" wrote in message ...
If you move to the centre of a black hole, where
gravitational forces sort of cancel, can light and
normal matter exist in some area there?

Gravitational forces don't cancel because the mass of a
black hole (except for the infalling matter from its
"feeding") is located at a singlularity at the center.

But why? image for a moment matter falling into a body.
As its mass increases,

The mass of infalling matter does not increase.

I was trying to say that the mass of the body increaes.

That is what I am telling you is incorrect. The BH gains the mass of
the body, and vice versa. But not as a function of the body's speed.

We cannot pass by each other at large fractions of the speed of light,
and turn one another into black holes.

David A. Smith

On a sunny day (5 Jan 2007 11:43:38 -0800) it happened "dlzc"
wrote in . com:

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (5 Jan 2007 07:45:35 -0800) it happened "dlzc"
wrote in . com:

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (Fri, 5 Jan 2007 09:31:03 -0500) it happened "Greg Neill"
wrote in
:

"Jan Panteltje" wrote in message ...
If you move to the centre of a black hole, where
gravitational forces sort of cancel, can light and
normal matter exist in some area there?

Gravitational forces don't cancel because the mass of a
black hole (except for the infalling matter from its
"feeding") is located at a singlularity at the center.

But why? image for a moment matter falling into a body.
As its mass increases,

The mass of infalling matter does not increase.

I was trying to say that the mass of the body increaes.

That is what I am telling you is incorrect. The BH gains the mass of
the body, and vice versa. But not as a function of the body's speed.

We cannot pass by each other at large fractions of the speed of light,
and turn one another into black holes.

David A. Smith

I lost you here, or your English.
I think that as matter falls into the (to be) BH,
its mass increases (that of the BH).
With that escape speed increases, as it is a function of the total mass.
Once the escape speed exceeds c (light speed) light can no longer escape.
I think this is correct, if not why not?

"dlzc" wrote in message
oups.com...

Happy New Year David,

I personally expect that the CMBR is a distorted image of the Universe
that contains the BH(s) that open into our Universe. George Dishman
has valiantly tried to dissuade me from my (wacky) opinion. It would
allow complete, fully-developed structures to exist right up to the
CMBR. It has the difficulties:
* having the amount of hydrogen the amount of iron,

What iron? A clearer statement would be having the
amount of _all_ primordial elements heavier than
lithium being zero.

* internal GR solutions have information from the past and future of
non-local objects available (assuming *now* for you and the remote
object starts at EH crossing),
* probably more.

The key objection was that you assign a physical
significance to the singularity inherent in the
Schwarzschild metric at the EH when that is purely
a coordinate effect and other coordinate systems
do not show any untoward behaviour there.

George

"Jan Panteltje" wrote in message
...

.. imag[in]e for a moment matter falling into a body.
As its mass increases, the escape speed from it will increase.
At some point the escape speed will be greater then C, so light cannot
escape,
we no longer see any EM waves coming from it, we call it a black hole
(is this correct?).

Not quite. As the new matter arrives, the mass increases
as does the volume. The surface gravity also increases as
does the pressure at the centre. As that pressure reaches
some threshold, it forces the electrons and protons in the
atoms in the core to become neutrons. Adding further matter
continues the process but then another threshold is reached
when the pressure exceeds what can be sustained by the
exclusion principle and the core collapses. This happens
_before_ the surface escape velocity reaches the speed of
light. At that point the core will implode and nothing we
know of can stop it. As the surface falls toward the centre,
the radius is decreasing while the total mass is constant
and at some point the surface escape velocity will reach
the speed of light and at that point you have a black hole,
but the surface is still colapsing towards the centre and
since the surface gravity is still increasing, there is
no way it can stop.

I'm glossing over dynamic effects, that isn't intended as a
description of the formation process in any way.

Incidentally, there is no point at the centre where things
balance out just as there is no value of r close to zero
where 1/r^2 is zero, it approaches infinity on both sides
and is infinite at zero.

There is nothing that says that the thing could not be a bit hollow, its
being
black only depends on the escape speed.

The matter on the surface would be moving faster than the
speed of light relative to a free-falling object which is
not possible in GR.

Or does the black hole simply get denser when you move towards it
center,
as opposed to haveing a center with a dense shell around it (black egg)?

There's no shell. The event horizon is about as substantial
as a property line; it just demarkates the boundary beyond
which there's no escape.

I agree with that (except for 'evaporation' of particles).

Whether some new quantum effect comes into play we don't
know but I think the scale at which new physics might
stop the collapse is smaller than an atom, so if the
entire mass of a star is compressed say to the size of a
single neutron and the radius of the event horizon is
several km, the question is not going to be easily
resolved by observation.

HTH
George

Dear George Dishman:

"George Dishman" wrote in message
...

"dlzc" wrote in message
oups.com...

Happy New Year David,

To you as well. Any unusual weather there, this time of year?
Kind of warm here, and got a little bit of rain.

I personally expect that the CMBR is a distorted
image of the Universe that contains the BH(s) that
open into our Universe. George Dishman has
valiantly tried to dissuade me from my (wacky)
opinion. It would allow complete, fully-developed
structures to exist right up to the CMBR. It has
the difficulties:
* having the amount of hydrogen the amount of iron,

What iron? A clearer statement would be having the
amount of _all_ primordial elements heavier than
lithium being zero.

Wait for it. My "solution" isn't, until / unless anomalous
structures complete with heavy elements are located "impossibly
close" to the CMBR. This early age is hard to image, now.
Especially for "normally energetic" structures.

* internal GR solutions have information from the
past and future of non-local objects available
(assuming *now* for you and the remote object
starts at EH crossing),
* probably more.

The key objection was that you assign a physical
significance to the singularity inherent in the
Schwarzschild metric at the EH when that is purely
a coordinate effect and other coordinate systems
do not show any untoward behaviour there.

Actually no, George. All the metrics (that I am aware of, a
short list since my ignorance is large) that smoothly transition
across the event horizon swap the outer radial and time axes for
internal time and spatial axes, in different sorts of "twist".
It isn't the Schwarzchild singularity that is the issue.

If spacetime is not something separate from matter, and the math
says something twists (like a rug being constructed on a loom),
maybe the outer Universe simply contributes to the inner as a
boundary condition... like tensioning the frame on a loom.

I was very careful to warn him (and any lurkers) that this was
only my opinion. I figure he remembers that he and I have
disagreed in the past, and will not spend a lot of time on this.

David A. Smith

On a sunny day (Sat, 6 Jan 2007 14:02:35 -0000) it happened "George Dishman"
wrote in :


"Jan Panteltje" wrote in message
...

.. imag[in]e for a moment matter falling into a body.
As its mass increases, the escape speed from it will increase.
At some point the escape speed will be greater then C, so light cannot
escape,
we no longer see any EM waves coming from it, we call it a black hole
(is this correct?).

Not quite. As the new matter arrives, the mass increases
as does the volume. The surface gravity also increases as
does the pressure at the centre. As that pressure reaches
some threshold, it forces the electrons and protons in the
atoms in the core to become neutrons. Adding further matter
continues the process but then another threshold is reached
when the pressure exceeds what can be sustained by the
exclusion principle and the core collapses. This happens
_before_ the surface escape velocity reaches the speed of
light. At that point the core will implode and nothing we
know of can stop it. As the surface falls toward the centre,
the radius is decreasing while the total mass is constant
and at some point the surface escape velocity will reach
the speed of light and at that point you have a black hole,
but the surface is still colapsing towards the centre and
since the surface gravity is still increasing, there is
no way it can stop.

I'm glossing over dynamic effects, that isn't intended as a
description of the formation process in any way.

Incidentally, there is no point at the centre where things
balance out just as there is no value of r close to zero
where 1/r^2 is zero, it approaches infinity on both sides
and is infinite at zero.

There is nothing that says that the thing could not be a bit hollow, its
being
black only depends on the escape speed.

The matter on the surface would be moving faster than the
speed of light relative to a free-falling object which is
not possible in GR.

Or does the black hole simply get denser when you move towards it
center,
as opposed to haveing a center with a dense shell around it (black egg)?

There's no shell. The event horizon is about as substantial
as a property line; it just demarkates the boundary beyond
which there's no escape.

I agree with that (except for 'evaporation' of particles).

Whether some new quantum effect comes into play we don't
know but I think the scale at which new physics might
stop the collapse is smaller than an atom, so if the
entire mass of a star is compressed say to the size of a
single neutron and the radius of the event horizon is
several km, the question is not going to be easily
resolved by observation.

HTH
George

George, thank you for the explanation.
Maybe one day they will figure out some way to know what happens in
the BH.
Maybe one of those big particle accelerators will make a tiny BH, and
deduce something from that.
Regards
Jan

David,

You "plonked" me long ago, so I don't know if you'll see this.

My understanding of a black hole event horizon is that its
location depends on the location and motion of the observer.
Most simply, it is always between the observer and the
singularity. If I fall into a black hole and you watch me from
a good distance, you will see me disappear at your event
horizon when my wris****ch reads 11:00 PM, but I will still
consider the horizon to be below me when my watch reads
11:01 PM. I can tell because George jumped in ahead of
me and doesn't disappear from my view until my watch
reads 11:01 PM.

-- Jeff, in Minneapolis

Dear Jeff Root:

Jeff Root wrote:
David,

You "plonked" me long ago, so I don't know if you'll see this.

Time to clear out some entries then.

My understanding of a black hole event horizon is that its
location depends on the location and motion of the observer.

Agreed. Just like a horizon moves away from you as you move towards
it.

Most simply, it is always between the observer and the
singularity. If I fall into a black hole and you watch me from
a good distance, you will see me disappear at your event
horizon when my wris****ch reads 11:00 PM, but I will still
consider the horizon to be below me when my watch reads
11:01 PM. I can tell because George jumped in ahead of
me and doesn't disappear from my view until my watch
reads 11:01 PM.

Actually GR says you can know stuff about George's past and future,
once you are "inside". And that an external observer *never* actually
sees you or George cross the horizon. (Unless the BH starts to
evaporate, when the photons will be able to escape before t=infinity.)

David A. Smith

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (5 Jan 2007 11:43:38 -0800) it happened "dlzc"
wrote in . com:

Dear Jan Panteltje:

Jan Panteltje wrote:
On a sunny day (5 Jan 2007 07:45:35 -0800) it happened "dlzc"
wrote in . com:

Dear Jan Panteltje:

Jan Panteltje wrote:
....
But why? image for a moment matter falling into
a body. As its mass increases,

The mass of infalling matter does not increase.

I was trying to say that the mass of the body
increaes.

That is what I am telling you is incorrect. The BH
gains the mass of the body, and vice versa. But
not as a function of the body's speed.

We cannot pass by each other at large fractions of
the speed of light, and turn one another into black
holes.

I lost you here, or your English.

They wouldn't have me. Those damned 'mericans...

I think that as matter falls into the (to be) BH,
its mass increases (that of the BH).

You "accused" the body (which I assumed to be different / separate from
the BH) of gaining mass because of its speed.

With that escape speed increases, as it is a function
of the total mass.

.... of the BH.

Once the escape speed exceeds c (light speed) light
can no longer escape. I think this is correct, if not
why not?

You had a body falling into an already established black hole. It is
assumed that it already has an established event horizon, which is a
"surface" (r=2M) where the escape velocity is c.

If you are imagining that the infalling body becomes its own BH before
crossing, simply because of its motion, and thereby loses its motion
and stays as part of an accumulating BH "shell", I don't think you have
a leg to stand on. Just because the light announcing the body's
position is trapped near the horizon, doesn't mean the body is. This
light is special. Most light from the body's passage will have
preceeded it into the BH.

I think there would be a quiet "burp", and we could perform a speed of
gravity experiment, to see when the presence of the body was
indiscernable from the center-of-gravity of the BH. At r=2M, or after
some finite time. Lots of different schools of thought here.

David A. Smith

"dlzc" wrote in message ups.com...
| Dear Jeff Root:
|
| Jeff Root wrote:
| David,
|
| You "plonked" me long ago, so I don't know if you'll see this.
|
| Time to clear out some entries then.
|
| My understanding of a black hole event horizon is that its
| location depends on the location and motion of the observer.
|
| Agreed. Just like a horizon moves away from you as you move towards
| it.
|
| Most simply, it is always between the observer and the
| singularity. If I fall into a black hole and you watch me from
| a good distance, you will see me disappear at your event
| horizon when my wris****ch reads 11:00 PM, but I will still
| consider the horizon to be below me when my watch reads
| 11:01 PM. I can tell because George jumped in ahead of
| me and doesn't disappear from my view until my watch
| reads 11:01 PM.
|
| Actually GR says you can know stuff about George's past and future,
| once you are "inside". And that an external observer *never* actually
| sees you or George cross the horizon. (Unless the BH starts to
| evaporate, when the photons will be able to escape before t=infinity.)
|
| David A. Smith

Amazing how you know so much about something that doesn't exist.
Psychiatrists call that "deluded", it is a mental aberration. Have
either of you three considered seeking psychiatric help?