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The Kerr black hole

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  The Kerr black hole mitchrae3323@gmail.com - 2018-09-25 18:46 -0700
    Re: The Kerr black hole JanPB <filmart@gmail.com> - 2018-09-25 20:48 -0700
      Re: The Kerr black hole mitchrae3323@gmail.com - 2018-09-25 21:25 -0700
        Re: The Kerr black hole JanPB <filmart@gmail.com> - 2018-09-26 23:57 -0700
          Re: The Kerr black hole Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-28 10:11 -0500
            Re: The Kerr black hole JanPB <filmart@gmail.com> - 2018-09-28 12:44 -0700
            Re: The Kerr black hole Hilton Packett <wod@wcothr.ce> - 2018-09-28 20:36 +0000
              Re: The Kerr black hole Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-28 16:37 -0500
                Re: The Kerr black hole Hilton Packett <wod@wcothr.ce> - 2018-09-28 21:55 +0000
                Re: The Kerr black hole JanPB <filmart@gmail.com> - 2018-09-28 15:02 -0700
                  Re: The Kerr black hole Hilton Packett <wod@wcotahr.ce> - 2018-09-29 23:57 +0000
                    Re: The Kerr black hole JanPB <filmart@gmail.com> - 2018-09-29 21:31 -0700
                      Re: The Kerr black hole Hilton Packett <wod@wcotahr.ce> - 2018-09-30 16:20 +0000
                        Re: The Kerr black hole moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-30 17:08 +0000
                          Re: The Kerr black hole Hilton Packett <wod@wcotahr.ce> - 2018-09-30 21:29 +0000
                    Re: The Kerr black hole "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2018-09-30 09:44 -0700
          Re: The Kerr black hole Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-28 10:11 -0500
            Re: The Kerr black hole Hilton Packett <wod@wcotahr.ce> - 2018-09-30 16:43 +0000

#473100 — The Kerr black hole

How does a singularity point rotate?
Even if somehow you believe that how
would it take the event horizon with it?
Space isn't doing that...

Here and now Black holes don't belong...

Mitchell Raemsch

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#473108

On Tuesday, September 25, 2018 at 6:46:38 PM UTC-7, mitchr...@gmail.com wrote:
> How does a singularity point rotate?
> Even if somehow you believe that how
> would it take the event horizon with it?
> Space isn't doing that...
> 
> Here and now Black holes don't belong...
> 
> Mitchell Raemsch

The singular set in Kerr t=const. slice is a circle, not a point. And it doesn't rotate in
any sensible way as it's not a part of spacetime.

--
Jan

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#473110

On Tuesday, September 25, 2018 at 8:48:20 PM UTC-7, JanPB wrote:
> On Tuesday, September 25, 2018 at 6:46:38 PM UTC-7, mitchr...@gmail.com wrote:
> > How does a singularity point rotate?
> > Even if somehow you believe that how
> > would it take the event horizon with it?
> > Space isn't doing that...
> > 
> > Here and now Black holes don't belong...
> > 
> > Mitchell Raemsch
> 
> The singular set in Kerr t=const. slice is a circle, not a point. And it doesn't rotate in
> any sensible way as it's not a part of spacetime.
> 
> --
> Jan
Slice isn't a singularity.
Black holes aren't real Jan...
Your knowledge is unreal.

Mitchell Raemsch

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#473236

On Tuesday, September 25, 2018 at 9:25:16 PM UTC-7, mitchr...@gmail.com wrote:
> On Tuesday, September 25, 2018 at 8:48:20 PM UTC-7, JanPB wrote:
> > On Tuesday, September 25, 2018 at 6:46:38 PM UTC-7, mitchr...@gmail.com wrote:
> > > How does a singularity point rotate?
> > > Even if somehow you believe that how
> > > would it take the event horizon with it?
> > > Space isn't doing that...
> > > 
> > > Here and now Black holes don't belong...
> > > 
> > > Mitchell Raemsch
> > 
> > The singular set in Kerr t=const. slice is a circle, not a point. And it doesn't rotate in
> > any sensible way as it's not a part of spacetime.
> > 
> > --
> > Jan
> Slice isn't a singularity.

I never said it was. By "slice" I simply meant the 3D space at a fixed coordinate time.

> Black holes aren't real Jan...

This is most likely correct.

> Your knowledge is unreal.

That's beside the point, the idea here is to "stress" the given model (GR in this case)
by going along with its consequences to see where they lead. This sort of "what if"
game can be very useful when attempting to come up with new, better models.

--
Jan

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#473358

On 9/27/18 1:57 AM, JanPB wrote:
> On Tuesday, September 25, 2018 at 9:25:16 PM UTC-7, mitchr...@gmail.com wrote:
>> Black holes aren't real Jan...
> 
> This is most likely correct.

I disagree. Black holes are most likely real, because astronomers have observed 
many objects for which the only models we have are black holes, and those models 
agree very well with the observations. This includes several gravitational-wave 
events, Sgr A*, quasars, and compact super-massive objects observed at the 
centers of most galaxies.

Whether the singularity inside a black hole "exists" is a rather different 
question; I suspect they probably don't "exist" (whatever that might mean for a 
singularity), because there is no expectation that GR remains valid in such 
regions. I also suspect that we will never know this for sure, because those 
singularities are cloaked by a horizon.

	(Note that other than unfounded speculations, we have no reason
	 to expect that GR does not apply near and at the horizons of
	 such black holes. Observations trump speculations.)

Tom Roberts

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#473396

On Friday, September 28, 2018 at 8:11:10 AM UTC-7, tjrob137 wrote:
> On 9/27/18 1:57 AM, JanPB wrote:
> > On Tuesday, September 25, 2018 at 9:25:16 PM UTC-7, mitchr...@gmail.com wrote:
> >> Black holes aren't real Jan...
> > 
> > This is most likely correct.
> 
> I disagree. Black holes are most likely real, because astronomers have observed 
> many objects for which the only models we have are black holes, and those models 
> agree very well with the observations.

I meant strictly the singular set, I should have said that precisely.
I have no beef with the horizon.

--
Jan

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#473406

Tom Roberts wrote:

> On 9/27/18 1:57 AM, JanPB wrote:
>> On Tuesday, September 25, 2018 at 9:25:16 PM UTC-7, mitchr...@gmail.com
>> wrote:
>>> Black holes aren't real Jan...
>> 
>> This is most likely correct.
> 
> I disagree. Black holes are most likely real, because astronomers have
> observed many objects for which the only models we have are black holes,
> and those models agree very well with the observations. This includes
> several gravitational-wave events, Sgr A*, quasars, and compact
> super-massive objects observed at the centers of most galaxies.
> Whether the singularity inside a black hole "exists" is a rather
> different question; I suspect they probably don't "exist" (whatever that
> might mean for a singularity), because there is no expectation that GR
> remains valid in such regions. I also suspect that we will never know
> this for sure, because those singularities are cloaked by a horizon.

In principle you can escape the horizon, using the kinetic energy from the 
fall, plus the payload carrying propellant. 

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#473424

On 9/28/18 3:36 PM, Hilton Packett wrote:
> Tom Roberts wrote:
> Black holes are most likely real, [...]
> 
> In principle you can escape the horizon, using the kinetic energy from the
> fall, plus the payload carrying propellant.

Not true. Once any timelike object enters the horizon of a black hole, no amount 
of kinetic energy or propellant can get it back outside the horizon. Moreover it 
is doomed to intersect the singularity at the "center" within finite proper 
time. This also applies to null objects (light), mutatis mutandis.

Tom Roberts

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#473428

Tom Roberts wrote:

> On 9/28/18 3:36 PM, Hilton Packett wrote:
>> Tom Roberts wrote:
>> Black holes are most likely real, [...]
>> 
>> In principle you can escape the horizon, using the kinetic energy from
>> the fall, plus the payload carrying propellant.
> 
> Not true. Once any timelike object enters the horizon of a black hole,
> no amount of kinetic energy or propellant can get it back outside the
> horizon. Moreover it is doomed to intersect the singularity at the
> "center" within finite proper time. This also applies to null objects
> (light), mutatis mutandis.

Yes, but I was thinking mass objects are falling through bellow light 
speed, since otherwise it would violate many other things. So I was 
thinking that the fall and rise energy cancels out, then you have the 
carrying propellant to give the additional push.

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#473430

On Friday, September 28, 2018 at 2:37:44 PM UTC-7, tjrob137 wrote:
> On 9/28/18 3:36 PM, Hilton Packett wrote:
> > Tom Roberts wrote:
> > Black holes are most likely real, [...]
> > 
> > In principle you can escape the horizon, using the kinetic energy from the
> > fall, plus the payload carrying propellant.
> 
> Not true. Once any timelike object enters the horizon of a black hole, no amount 
> of kinetic energy or propellant can get it back outside the horizon. Moreover it 
> is doomed to intersect the singularity at the "center" within finite proper 
> time.

Strictly speaking (i.e. strict GR) this is true only for non-rotating black 
holes. In the rotating case two things happen:

1. the "one-way street" beyond the horizon "detaches" itself from the
singular set,

2. the singular set itself "opens up" into a disc of radius "a" (the
rotation's angular momentum per unit mass) acting as a branch cut in
the spacetime through which an infalling object can go.

In fact, in this situation ("a" nonzero) it gets quite hard to hit the
singular set, again two reasons:

1. the singular set is gravitationally repulsing (it's also repulsing
in the Schwarzschild (non-rotating) case but the "one-way street" part
of spacetime is "touching" it there, so it does become unavoidable
regardless),

2. on top of that, one can also prove (Carter's theorem) that
a free-falling object can hit the singular set only if its trajectory
is completely contained in the equatorial plane (of course the tidal
forces near the singular set may be lethal anyway).

Finally, the repulsive force of the singularity in the rotating case
is quite strong, for example an object dropped along the axis of
rotation down will go through the horizons and then _bounce back_,
repulsed by the singularity, again through the horizons (a different
pair of horizons) into a different branch of the fully extended
spacetime. In order to get that object to fly _through_ the singularity
(which is a circle) one must supply an extra thrust to it, just free-falling
down from infinity is not strong enough. With that sort of extra push
this is possible and given massive enough black hole will produce
FAPP imperceptible tidal forces.

This is all strict GR, of course. We'll hopefully find out better with
a better theory.

--
Jan

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#473506

JanPB wrote:

> 2. the singular set itself "opens up" into a disc of radius "a" (the
> rotation's angular momentum per unit mass) acting as a branch cut in the
> spacetime through which an infalling object can go.

I barely conceive a singularity forming the shape of a disk.

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#473523

On Saturday, September 29, 2018 at 4:57:20 PM UTC-7, Hilton Packett wrote:
> JanPB wrote:
> 
> > 2. the singular set itself "opens up" into a disc of radius "a" (the
> > rotation's angular momentum per unit mass) acting as a branch cut in the
> > spacetime through which an infalling object can go.
> 
> I barely conceive a singularity forming the shape of a disk.

The singularity is a circle, the disc is not singular.

--
Jan

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#473564

JanPB wrote:

> On Saturday, September 29, 2018 at 4:57:20 PM UTC-7, Hilton Packett
> wrote:
>> JanPB wrote:
>> 
>> > 2. the singular set itself "opens up" into a disc of radius "a" (the
>> > rotation's angular momentum per unit mass) acting as a branch cut in
>> > the spacetime through which an infalling object can go.
>> 
>> I barely conceive a singularity forming the shape of a disk.
> 
> The singularity is a circle, the disc is not singular.

How can that be a circle. Circles are empty inside. I can't visualize such 
as whatsoever. You either have a singularity, or you don't have it.

I got it, since the nature is an approximation, that singularity may 
stretch along a circle??

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#473582

The nymshifting troll Hilton Packett <wod@wcotahr.ce> writes:

>JanPB wrote:

>> On Saturday, September 29, 2018 at 4:57:20 PM UTC-7, Hilton Packett
>> wrote:
>>> JanPB wrote:
>>> 
>>> > 2. the singular set itself "opens up" into a disc of radius "a" (the
>>> > rotation's angular momentum per unit mass) acting as a branch cut in
>>> > the spacetime through which an infalling object can go.
>>> 
>>> I barely conceive a singularity forming the shape of a disk.
>> 
>> The singularity is a circle, the disc is not singular.

>How can that be a circle. Circles are empty inside. I can't visualize such 
>as whatsoever. You either have a singularity, or you don't have it.

The singularity is the circumference itself, not the inside. Instead of a
point of no size, it is a (curved) line with zero size in two dimensions,
not three like a point.

I guess GR predicts all kinds of weird stuff if you go through the circle
created by the singularity without getting too near the singularity (not
too near the edge of the circle) but I think of this as angels dancing on
pinheads territory.

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#473621

The nymshifting troll botoxed dwarf Michael Moroney wrote:

> Prof. Dr. Hilton Packett <wod@wcotahr.ce> writes:
>>JanPB wrote:
>>> On Saturday, September 29, 2018 at 4:57:20 PM UTC-7, Hilton Packett
>>> wrote: 
>>>> I barely conceive a singularity forming the shape of a disk.
>>> 
>>> The singularity is a circle, the disc is not singular.
> 
>>How can that be a circle. Circles are empty inside. I can't visualize
>>such as whatsoever. You either have a singularity, or you don't have it.
> 
> The singularity is the circumference itself, not the inside. Instead of
> a point of no size, it is a (curved) line with zero size in two
> dimensions, not three like a point.
> I guess GR predicts all kinds of weird stuff if you go through the
> circle created by the singularity without getting too near the
> singularity (not too near the edge of the circle) but I think of this as
> angels dancing on pinheads territory.

Talk is cheap. Dare you coming here without the shadow of an equation. Put 
your mechanism up, in form of equations, or find yourself another hobby. I 
am the equation man.

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#473577

On Saturday, September 29, 2018 at 4:57:20 PM UTC-7, Hilton Packett wrote:
> JanPB wrote:
> 
> > 2. the singular set itself "opens up" into a disc of radius "a" (the
> > rotation's angular momentum per unit mass) acting as a branch cut in the
> > spacetime through which an infalling object can go.
> 
> I barely conceive a singularity forming the shape of a disk.


"Spiral space-filling curve."  Singularity theory is 
usually about an asymptote, but a spiral space-filling 
curve (eg a sphere with a center) is also a "singularity".
(Curvature as 1/r and all.)

(Physics' black hole as a singularity is "it would take 
infinite velocity to get out", that "infinite" is an 
asymptote of the velocity as a function of time.)

About "no amount of kinetic energy or propellant", or, 
change in a local system inside the event horizon can 
ever get out, there's still an idea like that an object 
has relativistic mass when it enters the event horizon, 
then loses that, eg the ring cyclotron spinning down, 
or, eg along the Allais effect, or, "space-time wheel",
that the otherwise always growing Schwarzchild radius 
would reduce and the contents now outside would be ejected.

But, any organization crossing the event horizon would 
be spaghettified / distintegrated.

"As to what local deformation there might be as matches
the interface and goes past the event horizon in one piece
is rather as above (not that there'd be anything else
there in one piece). "

Then, reading Allais, it does appear to be that the Earth 
like any other place in the universe is at a fulcrum of 
the shift of all the objects in the universe about it and 
it's more than less a local constant: the drift of the aether 
about the Earth (or any other origin or frame).


https://en.wikipedia.org/wiki/Dayton_Miller


"This motion is called 'peculiar' because it is characteristic 
of our local position in the universe," Pluchino said. "In fact, 
it is obtained by combining the motion of our galaxy, and of 
the local group of galaxies, with a velocity of about 600 km/sec 
toward what is called the Great Attractor (a large concentration 
of matter situated at about 100 Mpc from us), along with the motion 
of the solar system within our galaxy. Therefore, an observer placed 
at the opposite site of our galaxy will also see a dipole anisotropy but, 
for him, the kinematical parameters will be different."

Read more at: https://phys.org/news/2016-02-year-old-ether-cosmological-temperature-gradient.html#jCp



This reflects on a recent discussion here about 
"is the Kerr metric derived"?  Basically that's 
about that anything is either drawn in a spiral 
(and is, "highly non-linear") or goes straight in 
as per usual derivations of a metric.

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#473359

On 9/27/18 1:57 AM, JanPB wrote:
> On Tuesday, September 25, 2018 at 9:25:16 PM UTC-7, mitchr...@gmail.com wrote:
>> Black holes aren't real Jan...
> 
> This is most likely correct.

I disagree. Black holes are most likely real, because astronomers have observed 
many objects for which the only models we have are black holes, and those models 
agree very well with the observations. This includes several gravitational-wave 
events, Sgr A*, quasars, and compact super-massive objects observed at the 
centers of most galaxies.

Whether the singularity inside a black hole "exists" is a rather different 
question; I suspect they probably don't "exist" (whatever that might mean for a 
singularity), because there is no expectation that GR remains valid in such 
regions. I also suspect that we will never know this for sure, because those 
singularities are cloaked by a horizon.

	(Note that other than unfounded speculations, we have no reason
	 to expect that GR does not apply near and at the horizons of
	 such black holes. Observations trump speculations.)

Tom Roberts

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#473576

Tom Roberts wrote:

> Whether the singularity inside a black hole "exists" is a rather
> different question; I suspect they probably don't "exist" (whatever that
> might mean for a singularity), because there is no expectation that GR
> remains valid in such regions. I also suspect that we will never know
> this for sure, because those singularities are cloaked by a horizon.

I don't think this is a problem. I can easily travel through a black hole. 
Even assuming chaos under the horizon, one cannot exclude a required 
thrust energy oriented out of the black hole, giving the push. Along the 
finite time. Local time.

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