5 ms·

Here is an interesting paper that says a collapsing star sheds enough mass to not ever become a black hole or form a singularity. It's from 2014, and still cont

by eggy 6y ago

Here is an interesting paper that says a collapsing star sheds enough mass to not ever become a black hole or form a singularity. It's from 2014, and still controversial, but interesting, and her math seems to have been reviewed. I will follow this with interest to see how it fares peer review. Evidence of black holes is indirect at the moment, which is OK for now, but it will be interesting to see how it all pans out in the coming years. https://phys.org/news/2014-09-black-holes.html https://phys.org/news/2014-09-black-holes.html

ChrisLomont 6y ago
There's plenty of papers by others past this one, showing a more accurate model yields black holes, for example [1]. Here's [2] about 25 others. [1] https://arxiv.org/pdf/1609.05775.pdf https://arxiv.org/pdf/1609.05775.pdf [2] https://scholar.google.com/scholar?cites=12026935191450315869&as_sdt=800005&sciodt=0,15&hl=en https://scholar.google.com/scholar?cites=1202693519145031586...
- meowface 6y ago
  I understand that the existence of black holes is pretty widely believed, now, but how controversial is the idea of true singularities being inside? I know, for example, there's Carlo Rovelli's "Planck star" hypothesis, which posits that the black hole is effectively (from an outside observer's perspective) an extremely slow violent explosion and hits an energy density limit before ever reaching the singularity stage: https://en.m.wikipedia.org/wiki/Planck_star https://en.m.wikipedia.org/wiki/Planck_star
  - ChrisLomont 6y ago
    >but how controversial is the idea of true singularities being inside I don't know any physicist that would believe this. Singularities happen mathematically due to GR being continuous space and time and material, but we know material is not continuous, and it's possible space and time are not also. So pretty much every one I have ever read or talked to about this believes that once GR is corrected for the quantum level, the singularities will go away, since they by definition would require quantum scale behavior, and it's known GR is not a quantized theory. Note that the "Plank star" is a LQG theory, and LQG has so far failed to reproduce much of anything, so it's not clear at all how that will play out. It hasn't even been shown to reproduce GR at the appropriate scales, and it was recently a big deal when LQG was made consistent on a circle. It's no where ready to deal with 4D spacetime yet. My guess is LQG, like so many other theories of gravity, will die out as more and more pieces of it end up disagreeing with experiments.
    - meowface 6y ago
      Thanks for the clarification on LQG. As a totally uninformed layman, your description of the singularity was also my understanding. I only brought up the question because this is the second paragraph of the original comment in this sub-thread: >Would it be possible or plausible that singularity actually does not exist, but just that the theory of general relativity is not a correct description of space/time/matter in small scale? I am thinking in classical theory, when things were treated as point mass/charges, infinity exist in the solution of point sources. Basically, I wasn't sure why they were getting so much criticism for this, because it sounded pretty reasonable to me.

by eggy 6y ago

ChrisLomont 6y ago

There's plenty of papers by others past this one, showing a more accurate model yields black holes, for example [1]. Here's [2] about 25 others. [1] https://arxiv.org/pdf/1609.05775.pdf https://arxiv.org/pdf/1609.05775.pdf [2] https://scholar.google.com/scholar?cites=12026935191450315869&as_sdt=800005&sciodt=0,15&hl=en https://scholar.google.com/scholar?cites=1202693519145031586...

meowface 6y ago
I understand that the existence of black holes is pretty widely believed, now, but how controversial is the idea of true singularities being inside? I know, for example, there's Carlo Rovelli's "Planck star" hypothesis, which posits that the black hole is effectively (from an outside observer's perspective) an extremely slow violent explosion and hits an energy density limit before ever reaching the singularity stage: https://en.m.wikipedia.org/wiki/Planck_star https://en.m.wikipedia.org/wiki/Planck_star
- ChrisLomont 6y ago
  >but how controversial is the idea of true singularities being inside I don't know any physicist that would believe this. Singularities happen mathematically due to GR being continuous space and time and material, but we know material is not continuous, and it's possible space and time are not also. So pretty much every one I have ever read or talked to about this believes that once GR is corrected for the quantum level, the singularities will go away, since they by definition would require quantum scale behavior, and it's known GR is not a quantized theory. Note that the "Plank star" is a LQG theory, and LQG has so far failed to reproduce much of anything, so it's not clear at all how that will play out. It hasn't even been shown to reproduce GR at the appropriate scales, and it was recently a big deal when LQG was made consistent on a circle. It's no where ready to deal with 4D spacetime yet. My guess is LQG, like so many other theories of gravity, will die out as more and more pieces of it end up disagreeing with experiments.
  - meowface 6y ago
    Thanks for the clarification on LQG. As a totally uninformed layman, your description of the singularity was also my understanding. I only brought up the question because this is the second paragraph of the original comment in this sub-thread: >Would it be possible or plausible that singularity actually does not exist, but just that the theory of general relativity is not a correct description of space/time/matter in small scale? I am thinking in classical theory, when things were treated as point mass/charges, infinity exist in the solution of point sources. Basically, I wasn't sure why they were getting so much criticism for this, because it sounded pretty reasonable to me.