3 ms·

How does a black hole this small stay together. I assumed it was gravity pushing against the atomic forces. Is it a case of once you black, you never go back?

GolDDranks 1y ago
Nobody really knows for black holes of these sizes, because we don't have a theory of quantum gravity, but I think that answer according to general relativity would that the curvature is steep enough that escaping would require going faster than c, the universal speed limit, so it doesn't happen.
clarionbell 1y ago
Exactly. Once your object reaches the right radius it's done. It will 'evaporate' eventually. But it won't revert back. An interesting result is that you could, and this is very much beyond our engineering, manufacture black holes like this.
- casperc 1y ago
  Very cool. Is there a place I can read up on this?
  - clarionbell 1y ago
    https://en.wikipedia.org/wiki/Schwarzschild_radius https://en.wikipedia.org/wiki/Schwarzschild_radius The principle is simple. If something crosses it's Schwarzschild radius, it becomes a black hole. So if you had a very, very, obscenely large particle collider, you could start smashing heavy nuclei with enough force to get them within that radius. Then you would have to 'trap' the new micro-black hole in some way (possibly give it a charge) and 'feed' it more matter very, very quickly, before it evaporates. The evaporation is a bit trickier, also known as Hawking radiation. It has not been observed yet, but it's one of those cases when we are pretty sure something like it must be going on. Otherwise we have even bigger hole in our understanding of the universe. Theory is more difficult, but the practical effect is relatively obvious. Once the 'surface temperature' of black hole reaches over that of microwave background, it will begin to evaporate. The process is slow at first, but non-linear. As black hole evaporates, it loses mass, but the temperature actually rises. Eventually, the process should end with a gamma ray burst. There is a lot of unknown in that. Right now we are very, very far from doing any of this. We would need to achieve much higher strength of magnetic fields before we could even consider this. It may turn out, that it's easier just to "catch" an existing micro-black hole. If they exist that is.
  - GuB-42 1y ago
    One way would be to make a "Kugelblitz". It works by concentrating a huge amount of energy in a very small space. Because of E=mc2, concentrating energy does the same thing as concentrating mass, and could create a black hole from which even the photons that created it can't escape, at least in theory. In practice, probably impossible, or at least well beyond our current technological capabilities.
meindnoch 1y ago
Black holes are not held together by gravity. The geometry of spacetime inside the event horizon doesn't allow anything to move away from the singularity. All possible worldlines move closer to the singularity.
- steve_adams_86 1y ago
  Except some radiation does leave, evidently. As far as I know, no one knows how or why. I hope we find out before I die. It’s such a fascinating, confusing aspect of black holes
  - lqstuart 1y ago
    Stephen Hawking had a pretty good idea as to how and why - https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation This is not to be confused with the infrared light that’s relatively easy to detect, which isn’t leaving the black hole but is just light emitted from matter heating up due to tidal forces near the black hole. I don’t think humanity is ever really going to know what a black hole actually is, simply because they’re too far away and the energy levels required for experiments are many many orders of magnitude beyond what we can generate on Earth. But I do expect if we could get up close and study one, we’d simply discover a lot of fascinating new physics over top of some kind of matter not that far off from neutron stars. A lot of people don’t really get past the pop science articles about “singularities” to realize that those are just failures of our theories. We don’t know how anything behaves when gravity is strong enough to affect the quantum level, because QM has some kind of silly techniques for avoiding it under normal circumstances (called renormalization) that no longer work. At extremely high energy levels, my guess as a guy on the internet is that the universe looks less like magical portals to Matthew McConaughey’s bookshelf, but more like regular boring space crap that destroys our notions of stuff like time, matter, energy, causality etc. And in fairness, neutron stars already kind of do this, but nobody cares for some reason.
  - Maxatar 1y ago
    The radiation you talk about, Hawking radiation, does not come from inside of the black hole. It is caused by the black hole but it is formed from beyond its event horizon.

GolDDranks 1y ago

Nobody really knows for black holes of these sizes, because we don't have a theory of quantum gravity, but I think that answer according to general relativity would that the curvature is steep enough that escaping would require going faster than c, the universal speed limit, so it doesn't happen.

clarionbell 1y ago

Exactly. Once your object reaches the right radius it's done. It will 'evaporate' eventually. But it won't revert back. An interesting result is that you could, and this is very much beyond our engineering, manufacture black holes like this.

casperc 1y ago
Very cool. Is there a place I can read up on this?
- clarionbell 1y ago
  https://en.wikipedia.org/wiki/Schwarzschild_radius https://en.wikipedia.org/wiki/Schwarzschild_radius The principle is simple. If something crosses it's Schwarzschild radius, it becomes a black hole. So if you had a very, very, obscenely large particle collider, you could start smashing heavy nuclei with enough force to get them within that radius. Then you would have to 'trap' the new micro-black hole in some way (possibly give it a charge) and 'feed' it more matter very, very quickly, before it evaporates. The evaporation is a bit trickier, also known as Hawking radiation. It has not been observed yet, but it's one of those cases when we are pretty sure something like it must be going on. Otherwise we have even bigger hole in our understanding of the universe. Theory is more difficult, but the practical effect is relatively obvious. Once the 'surface temperature' of black hole reaches over that of microwave background, it will begin to evaporate. The process is slow at first, but non-linear. As black hole evaporates, it loses mass, but the temperature actually rises. Eventually, the process should end with a gamma ray burst. There is a lot of unknown in that. Right now we are very, very far from doing any of this. We would need to achieve much higher strength of magnetic fields before we could even consider this. It may turn out, that it's easier just to "catch" an existing micro-black hole. If they exist that is.
- GuB-42 1y ago
  One way would be to make a "Kugelblitz". It works by concentrating a huge amount of energy in a very small space. Because of E=mc2, concentrating energy does the same thing as concentrating mass, and could create a black hole from which even the photons that created it can't escape, at least in theory. In practice, probably impossible, or at least well beyond our current technological capabilities.

meindnoch 1y ago

Black holes are not held together by gravity. The geometry of spacetime inside the event horizon doesn't allow anything to move away from the singularity. All possible worldlines move closer to the singularity.

steve_adams_86 1y ago
Except some radiation does leave, evidently. As far as I know, no one knows how or why. I hope we find out before I die. It’s such a fascinating, confusing aspect of black holes
- lqstuart 1y ago
  Stephen Hawking had a pretty good idea as to how and why - https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation This is not to be confused with the infrared light that’s relatively easy to detect, which isn’t leaving the black hole but is just light emitted from matter heating up due to tidal forces near the black hole. I don’t think humanity is ever really going to know what a black hole actually is, simply because they’re too far away and the energy levels required for experiments are many many orders of magnitude beyond what we can generate on Earth. But I do expect if we could get up close and study one, we’d simply discover a lot of fascinating new physics over top of some kind of matter not that far off from neutron stars. A lot of people don’t really get past the pop science articles about “singularities” to realize that those are just failures of our theories. We don’t know how anything behaves when gravity is strong enough to affect the quantum level, because QM has some kind of silly techniques for avoiding it under normal circumstances (called renormalization) that no longer work. At extremely high energy levels, my guess as a guy on the internet is that the universe looks less like magical portals to Matthew McConaughey’s bookshelf, but more like regular boring space crap that destroys our notions of stuff like time, matter, energy, causality etc. And in fairness, neutron stars already kind of do this, but nobody cares for some reason.
- Maxatar 1y ago
  The radiation you talk about, Hawking radiation, does not come from inside of the black hole. It is caused by the black hole but it is formed from beyond its event horizon.