Starship Asterisk*

Chris Peterson wrote:

neufer wrote:
The cores of black holes and elementary particles consist of strings or sheets or other higher dimensional objects...It is a reasonable assumption that doesn't require that current scientific ideas are anywhere near close to any final solution.

It's still just a mathematical result that appears elegant, but largely fails as a scientific theory on the grounds that virtually nothing about it seems testable or falsifiable. An interesting channel of investigation, but too premature, I think, to treat as even provisionally likely.

https://en.wikipedia.org/wiki/Regge_theory wrote:
<<In 1960 Geoffrey Chew and Steven Frautschi conjectured from limited data that the strongly interacting particles had a very simple dependence of the squared-mass on the angular momentum: the particles fall into families where the Regge trajectory functions were straight lines for all the trajectories. The straight-line Regge trajectories were later understood as arisin From massless endpoints on rotating relativistic strings.>>

neufer wrote:

Chris Peterson wrote:

neufer wrote: The point here is that point singularities probably don't exist in the real world.

I wouldn't go as far as "probably". We just don't know.

Point singularities:

• 1) produce strong infinities that must be treated with ad hoc renormalizations
  2) and contain angular momentum, mass & other info that must be assigned ad hoc.

neufer wrote:

Chris Peterson wrote:

neufer wrote:
The cores of black holes and elementary particles consist of strings or sheets or other higher dimensional objects.

A conclusion that stems from highly speculative and only marginally scientific ideas. We don't know what the cores of black holes or elementary particles consist of. Maybe the idea of "core" doesn't even apply.

It is a reasonable assumption that doesn't require that current scientific ideas are anywhere near close to any final solution.

Chris Peterson wrote:

neufer wrote:

Chris Peterson wrote:
But it's important to recognize that these are the conclusions of mathematical analyses, taken to limits where our theories may not work. These abstractions are very useful, but we have no clue what a physical singularity (point or ring) really means outside of the math.

The point here is that point singularities probably don't exist in the real world.

I wouldn't go as far as "probably". We just don't know.

• 1) produce strong infinities that must be treated with ad hoc renormalizations
  2) and contain angular momentum, mass & other info that must be assigned ad hoc.

Chris Peterson wrote:

neufer wrote:
The cores of black holes and elementary particles consist of strings or sheets or other higher dimensional objects.

A conclusion that stems from highly speculative and only marginally scientific ideas. We don't know what the cores of black holes or elementary particles consist of. Maybe the idea of "core" doesn't even apply.

neufer wrote:

Chris Peterson wrote:

neufer wrote:
Point singularities DON'T exist in the cores of rotating BHs.
RING singularities exist in the cores of rotating BHs.

But it's important to recognize that these are the conclusions of mathematical analyses, taken to limits where our theories may not work. These abstractions are very useful, but we have no clue what a physical singularity (point or ring) really means outside of the math.

The point here is that point singularities probably don't exist in the real world.

The cores of black holes and elementary particles consist of strings or sheets or other higher dimensional objects.

Chris Peterson wrote:

neufer wrote:
Point singularities DON'T exist in the cores of rotating BHs.
RING singularities exist in the cores of rotating BHs.

But it's important to recognize that these are the conclusions of mathematical analyses, taken to limits where our theories may not work. These abstractions are very useful, but we have no clue what a physical singularity (point or ring) really means outside of the math.

neufer wrote:Point singularities DON'T exist in the cores of rotating BHs.
RING singularities exist in the cores of rotating BHs.

BDanielMayfield wrote:

MarkBour wrote:

BDanielMayfield wrote:
Since at least most of a black hole’s angular momentum will be retained how can it be that its mass is truly crushed down to a singularly? How can a point with no size possess angular momentum?

I can imagine a number of reasons that might be part of the current thinking on this that would get around this problem, but as far as I have imagined black holes so far, this would be a reason that the mass can't get to the center. Surely, this issue of the theory that has been discussed by physicists. Perhaps they agreed with us on this point.

It seems to this layman that there is good reason to doubt that singularities really exist at the cores of rotating BHs. Angular momentum is the “hold up” figuratively, but perhaps literally as well.

• Point singularities DON'T exist in the cores of rotating BHs.
  RING singularities exist in the cores of rotating BHs.

https://en.wikipedia.org/wiki/Kerr_metric#Kerr_black_holes_as_wormholes wrote:

[b][color=#0000FF][size=135]Event horizons and ergospheres of a rotating black hole (spin parameter a=Jc/G/M²=0.99); the ring-singularity is located at the equatorial kink of the inner ergosphere at R=a.[/size][/color][/b]

---

<<The Kerr metric or Kerr geometry describes the geometry of empty spacetime around a rotating uncharged axially-symmetric black hole with a spherical event horizon. The Kerr metric is an exact solution of the Einstein field equations of general relativity; these equations are highly non-linear, which makes exact solutions very difficult to find. The Kerr metric is a generalization of the Schwarzschild metric, which was discovered by Karl Schwarzschild in 1915 and which describes the geometry of spacetime around an uncharged, spherically-symmetric, and non-rotating body. The corresponding solution for a charged, spherical, non-rotating body, the Reissner–Nordström metric, was discovered soon afterwards (1916–1918). However, the exact solution for an uncharged, rotating black-hole, the Kerr metric, remained unsolved until 1963, when it was discovered by Roy Kerr. The natural extension to a charged, rotating black-hole, the Kerr–Newman metric, was discovered shortly thereafter in 1965.>>

MarkBour wrote:

neufer wrote: ...
When two black holes merge they first form a rapidly rotating prolate black hole
which radiates circularly polarized gravitational waves containing angular momentum.

Yes, mergers present a very complex case in this regard. I'll buy what you're telling me, and so mostly I want to consider the simpler case of one BH with various events of normal matter falling into it. If matter in an accretion disk swirls into a BH, then it will be rotating faster once it has fallen below the event horizon and I assume the BH will spin more and more as a result.

BDanielMayfield wrote:...
Side point: Since at least most of a black hole’s angular momentum will be retained how can it be that its mass is truly crushed down to a singularly? How can a point with no size possess angular momentum?

Bruce

Nice! You read my mind, Bruce. Admitting that a classical view of what is going on here may be inadequate, nevertheless, I imagine matter inside the BH swirling around the central point at a speed approaching c, and then that matter cannot get any closer to the center. Using

• L = mrv

then to conserve angular momentum as r decreased for that matter, v would need to increase.

I can imagine a number of reasons that might be part of the current thinking on this that would get around this problem, but as far as I have imagined black holes so far, this would be a reason that the mass can't get to the center. Surely, this issue of the theory that has been discussed by physicists. Perhaps they agreed with us on this point.

neufer wrote: ...
When two black holes merge they first form a rapidly rotating prolate black hole
which radiates circularly polarized gravitational waves containing angular momentum.

BDanielMayfield wrote:...
Side point: Since at least most of a black hole’s angular momentum will be retained how can it be that its mass is truly crushed down to a singularly? How can a point with no size possess angular momentum?

Bruce

• L = mrv

neufer wrote:

BDanielMayfield wrote:

MarkBour wrote:
Is it not part of the theory that black holes conserve angular momentum? And is it correct that the black hole will have the same total angular momentum about its central point as the sum of the angular momenta that all of the objects that fell into it had?

I would think so, that angular momentum would have to be conserved, even in the extreme conditions of a black hole.

More or less.

When two black holes merge they first form a rapidly rotating prolate black hole
which radiates circularly polarized gravitational waves containing angular momentum.

BDanielMayfield wrote:

MarkBour wrote:
Is it not part of the theory that black holes conserve angular momentum? And is it correct that the black hole will have the same total angular momentum about its central point as the sum of the angular momenta that all of the objects that fell into it had?

I would think so, that angular momentum would have to be conserved, even in the extreme conditions of a black hole.

MarkBour wrote:This leads me to a question. Is it not part of the theory that black holes conserve angular momentum? And is it correct that the black hole will have the same total angular momentum about its central point as the sum of the angular momenta that all of the objects that fell into it had?

Uncle Jeff wrote:

Case wrote:

distefanom wrote:..."chemical constellation"....??? What does it mean?

The familiar APOD play on words: Long ago (1756), Fornax was named by French astronomer Nicolas Louis de Lacaille, originally as le Fourneau Chymique (the Chemical Furnace), before being abbreviated to just Fornax.

That's probably asked every time APOD uses the phrase. In the future, each use should always be hyperlinked to your excellent explanation.

NCTom wrote:Is there enough known about barred galaxy development to determine if this is a stable form or if the bars represent a transitional state on its way to a more stable shape?

Case wrote:

APOD Robot wrote:At the core lies a supermassive black hole.

Wikipedia wrote:
In February 2013, observations using the NuSTAR satellite have found out that the central supermassive black hole of NGC 1365, measured to be about 2 million solar masses in mass, is spinning at almost the speed of light.[6]
https://www.nustar.caltech.edu/news/nustar130227

redmudislander wrote:
This galaxy is clearly a merger. (A layman's opinion.) The spiral arm that looks like a loop is clearly out of plane with the majority of rotation. It seems reasonable that each contributor to the merger would have a central black hole, and that these wouldn't necessarily hit head on but would end up orbiting each other, possibly allowing a bar to persist between them for quite some duration.

Case wrote:

distefanom wrote:..."chemical constellation"....??? What does it mean?

The familiar APOD play on words: Long ago (1756), Fornax was named by French astronomer Nicolas Louis de Lacaille, originally as le Fourneau Chymique (the Chemical Furnace), before being abbreviated to just Fornax.

NCTom wrote:
Is there enough known about barred galaxy development to determine if this is a stable form or if the bars represent a transitional state on its way to a more stable shape?

NCTom wrote:Is there enough known about barred galaxy development to determine if this is a stable form or if the bars represent a transitional state on its way to a more stable shape?

distefanom wrote:..."chemical constellation"....???
What does it mean?