Starship Asterisk*

Fred the Cat wrote:
I was surmising the other day that a black hole could only be if its substance could exist superimposed on itself. Within my amateur knowledge of physics the only bosons seemed to fit that limitation. Since fermions can't occupy the same physical space, they seemed ruled-out of any existence but the "outside" of that concept of a physical black hole.

Is that a terrible "superposition" to take?

https://en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit wrote:
<<The idea that there should be an absolute upper limit for the mass of a cold (as distinct from thermal pressure supported) self-gravitating body dates back to the work of Lev Landau, in 1932, whose reasoning was based on the Pauli exclusion principle according to which the Fermionic particles in sufficiently compressed matter would be forced into energy states so high that their rest mass contribution would become negligible compared with the relativistic kinetic contribution determined just by the relevant quantum wavelength λ which would be of the order of the mean interparticle separation.>>

https://en.wikipedia.org/wiki/Neutron_star wrote:
<<[Neutron stars] are supported against collapse by neutron degeneracy pressure, a phenomenon described by the Pauli exclusion principle. If the remnant has too great a density, something which occurs in excess of an upper limit of the size of neutron stars at 2–3 solar masses, it will continue collapsing to form a black hole.

Neutrons in a degenerate neutron gas are spaced much more closely than electrons in an electron-degenerate gas because the more massive neutron has a much shorter wavelength at a given energy. Typical separations are comparable with the size of the neutron and the range of the strong nuclear force and it is actually the repulsive nature of the latter at small separations that primarily supports neutron stars more massive than 0.7 solar masses (which includes all measured neutron stars).

There is an upper limit to the mass of a neutron-degenerate object, the Tolman–Oppenheimer–Volkoff limit, which is analogous to the Chandrasekhar limit for electron-degenerate objects. The limit for objects supported by ideal neutron degeneracy pressure is only 0.75 solar masses. For more realistic models including baryon interaction, the precise limit is unknown, as it depends on the equations of state of nuclear matter, for which a highly accurate model is not yet available. Above this limit, a neutron star may collapse into a black hole, or into other, denser forms of degenerate matter (such as quark matter) if these forms exist and have suitable properties (mainly related to degree of compressibility, or "stiffness", described by the equations of state).>>

Fred the Cat wrote:I was surmising the other day that a black hole could only be if its substance could exist superimposed on itself. Within my amateur knowledge of physics the only bosons seemed to fit that limitation. Since fermions can't occupy the same physical space, they seemed ruled-out of any existence but the "outside" of that concept of a physical black hole.

Fred the Cat wrote:I equally appreciate your thoughts Chris but I can't keep my curiosity from roaming into the spaces where fermions and bosons coexist and wondering about what is not yet understood. 8-)

Chris Peterson wrote:

Fred the Cat wrote:I equally appreciate your thoughts Chris but I can't keep my curiosity from roaming into the spaces where fermions and bosons coexist and wondering about what is not yet understood.

Nothing wrong with curiosity or with wondering. It's just important not to lose touch with that "not yet understood" component.

Fred the Cat wrote:
Thank "higher levels of existence" for professionals that add even more concepts difficult to comprehend.

gva wrote:I am confused by the depiction. I have always assumed that an accretion disk is shaped like...a disk. In this depiction, the black hole appears to be in a deep well; i.e., the accretion disk appears to be shaped more like an accretion "cloud".

I am surprised because I always thought that accreting matter orbits around the black hole quite a few times before reaching the event horizon. With every orbit, matter that orbits at an angle, relative to the average disk, experiences a lot of collisions and quickly settles into an orbit in the plane of the disk. This is the mechanism that makes Saturn's ring so extremely thin and almost perfectly circular. I did not expect the accretion disk around a black hole to be as thick as depicted. I was expecting something more similar to Saturn's rings.

gva wrote:I am confused by the depiction. I have always assumed that an accretion disk is shaped like...a disk. In this depiction, the black hole appears to be in a deep well; i.e., the accretion disk appears to be shaped more like an accretion "cloud".

I am surprised because I always thought that accreting matter orbits around the black hole quite a few times before reaching the event horizon. With every orbit, matter that orbits at an angle, relative to the average disk, experiences a lot of collisions and quickly settles into an orbit in the plane of the disk. This is the mechanism that makes Saturn's ring so extremely thin and almost perfectly circular. I did not expect the accretion disk around a black hole to be as thick as depicted. I was expecting something more similar to Saturn's rings.

BDanielMayfield wrote:A black hole is in a well, sort of; a 3 dimensional gravity well. No one's ever seen one up this close. They twist spacetime too. So, hard to rap our imaginations around to come up with something realistic looking.

heehaw wrote:Generally, I don't like fakes (artist's impressions, especially of exoplanets), but this one I think is pretty good!

DavidLeodis wrote:Black holes are fascinating .

In the Swift overview information that can be found through the Swift link in the credit it states "By the end of this day, somewhere in the visible universe a new black hole will have formed. Gamma-ray bursts (GRBs), the most distant and powerful explosions known, are likely the birth cries of these new black holes". With the vastness of the Universe I probably should not be surprised at that seemingly high rate of Black Hole formation but it still amazes me.

As I understand it no light can get out of a Black Hole so I wonder If there is a White Hole balancing opposite where light is being released? Sorry for the vagueness (and likely naivety) of my query as I'm unsure how to actually ask it.

DavidLeodis wrote:Thanks Silly Boy for your help :).

In my simple very non-scientific mind I assume that there is an opposite to everything to balance things out, which is why I wondered about 'White Holes'. If there are no opposites to Black Holes then I guess that over the billions of years left of the Universe then Black Holes will gradually merge and finally there will be just one left and that will be the end of things (before it all starts again :wink: ). Perhaps Black and White Holes are a grey area so to speak.

Chris Peterson wrote:

DavidLeodis wrote:Thanks Silly Boy for your help .

In my simple very non-scientific mind I assume that there is an opposite to everything to balance things out, which is why I wondered about 'White Holes'. If there are no opposites to Black Holes then I guess that over the billions of years left of the Universe then Black Holes will gradually merge and finally there will be just one left and that will be the end of things (before it all starts again ). Perhaps Black and White Holes are a grey area so to speak.

Most black holes will never merge. For the most parts, the only black hole mergers will be the central black holes of galaxies within individual clusters. There's no mechanism for others to merge, especially as most are already moving away from each other. Eventually, all the black holes will evaporate and cease to exist.