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We don't know if singularities are even possible. Maybe the universe has some crazy repulsive force when atoms or subatomic particles get really really close (c

We don't know if singularities are even possible. Maybe the universe has some crazy repulsive force when atoms or subatomic particles get really really close (closer than in neutron stars, where atoms are femtometers apart).

CarRamrod 1y ago
>Maybe the universe has some crazy repulsive force when atoms or subatomic particles get really really close (closer than in neutron stars, where atoms are femtometers apart). The Celestial Ick
mytailorisrich 1y ago
There are no "atoms" in neutron stars. The density and temperature are so high that they are "crushed" and that the electrons and protons form neutrons. The result is tightly packed neutrons, hence the name. I believe it is theorised that it might be possible to go even one step further to a "quark star" since neutrons are not elementary but made of quarks. No idea what a black hole might look like with no singularity...
- chasil 1y ago
  As I referenced in the wiki above, the surface of a neutron star is ordinary atomic matter (fully ionized), perhaps iron.
- nikbackm 1y ago
  https://en.wikipedia.org/wiki/Planck_star https://en.wikipedia.org/wiki/Planck_star
pif 1y ago
> closer than in neutron stars, where atoms are femtometers apart I suppose you meant neutrons instead of atoms. Atoms do not exist in a neutron star. At least, non in any significant quantity.
- deleted 1y ago
  [deleted]
- chasil 1y ago
  As I understand it, the surface of a neutron star is an iron shell. "Current models indicate that matter at the surface of a neutron star is composed of ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps between them. It is possible that the nuclei at the surface are iron, due to iron's high binding energy per nucleon. It is also possible that heavy elements, such as iron, simply sink beneath the surface, leaving only light nuclei like helium and hydrogen. If the surface temperature exceeds 10^6 kelvins (as in the case of a young pulsar), the surface should be fluid instead of the solid phase that might exist in cooler neutron stars (temperature <10^6 kelvins)." https://en.m.wikipedia.org/wiki/Neutron_star https://en.m.wikipedia.org/wiki/Neutron_star
  - pif 1y ago
    > ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps That is not purely neutrons, indeed, but it's different from an ordinary lattice made of ionized atoms, each missing a handful of electrons at most.
    - chasil 1y ago
      Reading a little further into the wiki, the depth of atomic matter is controlled by the neutron drip line. Since neutron stars have a maximum mass, this is likely a feature that they all exhibit. At the beginning of the neutron drip, the pressure in the star from neutrons, electrons, and the total pressure is roughly equal. As the density of the neutron star increases, the nuclei break down, and the neutron pressure of the star becomes dominant. When the density reaches a point where nuclei touch and subsequently merge, they form a fluid of neutrons with a sprinkle of electrons and protons. This transition marks the neutron drip, where the dominant pressure in the neutron star shifts from degenerate electrons to neutrons.
XorNot 1y ago
We know something which looks exactly like a singularity though does exist - i.e. whatever black holes are, we can observe matching predictions very well. So if singularities don't exist, then some other weird object must that naively looks like one.
- exe34 1y ago
  No we don't. We know what a blackhole looks like at the event horizon which is entire kilometers away from the alleged singularity.
- hoseja 1y ago
  You're not ever actually seeing the singularity. The place of INFINITE density. You're seeing the event horizon/curved spacetime around it, at best. Those can also appear around non-singularities.
  - radicalbyte 1y ago
    Unless the observable universe itself is within one.
    - hoseja 1y ago
      Well then it is not a singularity either, is it. Feels a bit like a misunderstanding is happening. "Singularity" is a well-defined mathematical concept, not just a cool synonym for "black hole".
- oersted 1y ago
  Do they look like singularities? As I understand it, any object that crosses a certain density threshold, to a point where light cannot escape its gravitational pull, is effectively a black-hole (even if the mathematical model for them is more purist, only described by a handful of parameters). I don't think they need to be infinitely dense to explain our observations. You could say that we do observe a singularity, not in the centre of the black-hole but in its event horizon. But technically that's just an infinity in the maths not a physical singularity, in the sense that if you were there it would just seem like normal space.
scotty79 1y ago
That would mean is that what prevents them is some other mechanism doing it accidentally. My view is that they are prevented by the GR itself (by time dilatation).
dnautics 1y ago
You can get this easy by reformulating gravity's effect on spacetime as slowing down the speed of light/causality and putting a natural bound that asymptotically approaches zero. It should agree with GR everywhere except at extremes like black holes. Looking at gravity as a slowdown of c is appealing because it suggests a computational cost of massive particles. As stuff gets more dense, the clock of the universe must slow down.
- westurner 1y ago
  GR does not describe the interior topology of black holes, beyond predicting a singularity. Is there a hard boundary with no hair, or is there a [knotted or braided] fluidic attractor system with fluidic turbulence at the boundary? SQR Superfluid Quantum Relativity seems to suggest that there is no hard event horizon boundary. I don't understand how any model that lacks descriptions of phase states in BEC superfluids could sufficiently describe the magneto-hydro-thermo-gravito dynamics of a black hole system and things outside of it? It is unclear whether mass/energy/information is actually drawn into a supermassive or a microscopic black hole; couldn't it be that things are only ever captured into attractor paths that are outside of the event horizon? Does Hawking radiation disprove that black holes don't absorb mass/energy/information?
- ccozan 1y ago
  Actually, behind the event horizon due to the limitation of light speed which is highest possible information transfer limit in universe, including the weak and strong field particles, these atomic forces that hold protons and neutrons together fail to work as outside so it a tangled mass of quarks and other barionic matter.

CarRamrod 1y ago

>Maybe the universe has some crazy repulsive force when atoms or subatomic particles get really really close (closer than in neutron stars, where atoms are femtometers apart). The Celestial Ick

mytailorisrich 1y ago

There are no "atoms" in neutron stars. The density and temperature are so high that they are "crushed" and that the electrons and protons form neutrons. The result is tightly packed neutrons, hence the name. I believe it is theorised that it might be possible to go even one step further to a "quark star" since neutrons are not elementary but made of quarks. No idea what a black hole might look like with no singularity...

chasil 1y ago
As I referenced in the wiki above, the surface of a neutron star is ordinary atomic matter (fully ionized), perhaps iron.
nikbackm 1y ago
https://en.wikipedia.org/wiki/Planck_star https://en.wikipedia.org/wiki/Planck_star

pif 1y ago

> closer than in neutron stars, where atoms are femtometers apart I suppose you meant neutrons instead of atoms. Atoms do not exist in a neutron star. At least, non in any significant quantity.

deleted 1y ago
[deleted]
chasil 1y ago
As I understand it, the surface of a neutron star is an iron shell. "Current models indicate that matter at the surface of a neutron star is composed of ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps between them. It is possible that the nuclei at the surface are iron, due to iron's high binding energy per nucleon. It is also possible that heavy elements, such as iron, simply sink beneath the surface, leaving only light nuclei like helium and hydrogen. If the surface temperature exceeds 10^6 kelvins (as in the case of a young pulsar), the surface should be fluid instead of the solid phase that might exist in cooler neutron stars (temperature <10^6 kelvins)." https://en.m.wikipedia.org/wiki/Neutron_star https://en.m.wikipedia.org/wiki/Neutron_star
- pif 1y ago
  > ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps That is not purely neutrons, indeed, but it's different from an ordinary lattice made of ionized atoms, each missing a handful of electrons at most.
  - chasil 1y ago
    Reading a little further into the wiki, the depth of atomic matter is controlled by the neutron drip line. Since neutron stars have a maximum mass, this is likely a feature that they all exhibit. At the beginning of the neutron drip, the pressure in the star from neutrons, electrons, and the total pressure is roughly equal. As the density of the neutron star increases, the nuclei break down, and the neutron pressure of the star becomes dominant. When the density reaches a point where nuclei touch and subsequently merge, they form a fluid of neutrons with a sprinkle of electrons and protons. This transition marks the neutron drip, where the dominant pressure in the neutron star shifts from degenerate electrons to neutrons.

XorNot 1y ago

We know something which looks exactly like a singularity though does exist - i.e. whatever black holes are, we can observe matching predictions very well. So if singularities don't exist, then some other weird object must that naively looks like one.

exe34 1y ago
No we don't. We know what a blackhole looks like at the event horizon which is entire kilometers away from the alleged singularity.
hoseja 1y ago
You're not ever actually seeing the singularity. The place of INFINITE density. You're seeing the event horizon/curved spacetime around it, at best. Those can also appear around non-singularities.
- radicalbyte 1y ago
  Unless the observable universe itself is within one.
  - hoseja 1y ago
    Well then it is not a singularity either, is it. Feels a bit like a misunderstanding is happening. "Singularity" is a well-defined mathematical concept, not just a cool synonym for "black hole".
oersted 1y ago
Do they look like singularities? As I understand it, any object that crosses a certain density threshold, to a point where light cannot escape its gravitational pull, is effectively a black-hole (even if the mathematical model for them is more purist, only described by a handful of parameters). I don't think they need to be infinitely dense to explain our observations. You could say that we do observe a singularity, not in the centre of the black-hole but in its event horizon. But technically that's just an infinity in the maths not a physical singularity, in the sense that if you were there it would just seem like normal space.

scotty79 1y ago

That would mean is that what prevents them is some other mechanism doing it accidentally. My view is that they are prevented by the GR itself (by time dilatation).

dnautics 1y ago

You can get this easy by reformulating gravity's effect on spacetime as slowing down the speed of light/causality and putting a natural bound that asymptotically approaches zero. It should agree with GR everywhere except at extremes like black holes. Looking at gravity as a slowdown of c is appealing because it suggests a computational cost of massive particles. As stuff gets more dense, the clock of the universe must slow down.

westurner 1y ago
GR does not describe the interior topology of black holes, beyond predicting a singularity. Is there a hard boundary with no hair, or is there a [knotted or braided] fluidic attractor system with fluidic turbulence at the boundary? SQR Superfluid Quantum Relativity seems to suggest that there is no hard event horizon boundary. I don't understand how any model that lacks descriptions of phase states in BEC superfluids could sufficiently describe the magneto-hydro-thermo-gravito dynamics of a black hole system and things outside of it? It is unclear whether mass/energy/information is actually drawn into a supermassive or a microscopic black hole; couldn't it be that things are only ever captured into attractor paths that are outside of the event horizon? Does Hawking radiation disprove that black holes don't absorb mass/energy/information?
ccozan 1y ago
Actually, behind the event horizon due to the limitation of light speed which is highest possible information transfer limit in universe, including the weak and strong field particles, these atomic forces that hold protons and neutrons together fail to work as outside so it a tangled mass of quarks and other barionic matter.