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> I have very high confidence that a real and effectively-correct theory of quantum gravity will remove the singularities. What gives you this confidence?

vecter 2y ago
The general belief that singularities are “unphysical” and reflect a flaw in our models than actual reality. Hard to prove definitely right now of course.
- hparadiz 2y ago
  I always thought the concept of a singularity here was just to make the math slightly simpler. That is to say that a black hole is still a spherical body with a set diameter. We just can't see it so there's no way to verify other than the fact that we can see the border of the event horizon.
  - atombender 2y ago
    As far as I know, that very much isn't the case. The singularity is a result of the math, not a trick to simplify it. My understanding is that many researchers do think it's a "placeholder" representing our lack of insight into how physics behave at those scales, and not a real physical phenomenon, and that it will one day be possible to work past it. I believe Kerr and Penrose (both of whom did some of the most foundational work on black holes) believe it's a mathematical artifact.
    - hparadiz 2y ago
      My random thoughts on this: - Is the math referring to the center of gravity as the singularity? Because even a sub black hole mass object would have that. - Why is there an assumption that just after a mass becomes a black hole the matter inside it suddenly compresses further when the actual gravity of the object has only slightly increased? - Is there a maximum density of matter in the universe and if the black hole even reaches that? - Wouldn't you need that number to be infinite if the black hole itself is infinitely small? - If the black hole does have a mass inside it... Do the light particles trapped inside the black hole form a blanket around the existing matter?
      - Dylan16807 2y ago
        > - Why is there an assumption that just after a mass becomes a black hole the matter inside it suddenly compresses further when the actual gravity of the object has only slightly increased? Yeah, that seems like an important thing to address. Black holes don't even have to be high density, or have much matter in the center at the time of formation. If you arrange enough big chunks of metal into a spherical-shell constellation, then drop them all toward their mutual center, they can reach the threshold to become a black hole before they even start colliding. What happens around that time, and what specifically does "singularity" mean (because I see people using it in very different ways). > - Is there a maximum density of matter in the universe and if the black hole even reaches that? > - Wouldn't you need that number to be infinite if the black hole itself is infinitely small? Black holes are the benchmark for maximum density. The event horizon is always exactly at the limit. By "black hole itself" do you mean something other than the event horizon? But that maximum density depends on size, smaller things can be denser and bigger things have to be less dense.
        hparadiz 2y ago
        > If you arrange enough big chunks of metal into a spherical-shell constellation, then drop them all toward their mutual center, they can reach the threshold to become a black hole before they even start colliding. When I say "black hole itself" I imagine any combination of mass at it's center that provides enough density to form a gravitational pull that will trap light.
        pixl97 2y ago
        > What happens around that time I can imagine it's something stupidly energetic. If you don't want them turning into a hot ball of neutrons first you're either going to have to spend a lot of energy keeping them apart or they are going to be orbiting a virtual center and it will take far longer for them to reach the center singularity than you expect. This will follow the laws of the 3(+) body problem so you won't be able to calculate a perfect impact, so the birth of the singularity will be shrouded in very high energy particles escaping. Nature abhors a naked singularity.
- vlovich123 2y ago
  All we know is that we’ve made a lot of crazy predictions about the structure and behavior of black holes well before we measured them and so far they’ve aligned remarkably close to the predictions. If there is a difference, it’s about the interior not how it shows up in our universe. And since we can never see inside the black hole, any alternative model would have to better explain some phenomena our existing models can’t or be even easier than relativity and explain the same things. We know string theory is hard to make consistent and it struggles to create falsifiable experiments. I would bet on relatively remaining a very very long time until we figure out how to unify quantum and relativity.
ikiris 2y ago
the dunning kruger effect
jerf 2y ago
To the best of my knowledge, none of the competing theories for integration have singularities in them. It is difficult to know what a "singularity" would look like in a universe that doesn't seem to have 0-dimensional mathematical points in it. It isn't that surprising that continuous theories have singularities in them. Reality doesn't seem to be continuous in the sense that real numbers are. It is unknown if Navier-Stokes can develop singularities in finite time, but in the real universe it won't matter because they won't lead to singularities in the real universe because it is ultimately just an approximation. "Interesting things" may happen around whatever those conditions are but nothing will be accelerated to infinite speed in the real universe. It is another theory that is a real-number-based continuous approximation made useful by the fact that real numbers are easier to do math with than physical quantities, but the real universe does not have plain real numbers in it. (This is subtly different than the controversial statement that it isn't made out of real numbers at all. But it does not have "plain" real numbers. You certainly can not expect to pull out a microscope and peer at the universe at a scale of 10^-10000 meters and see a universe that behaves exactly the same, just at a smaller scale. Our universe is definitely not scale-invariant.) I think this is likely to be a rather accurate metaphor. To be honest, I don't see a lot of positive reason to assume that the singularities are going to be "real". I think physicists initial reactions to the idea were correct and remain correct. I think the reasons why people think otherwise are emotional rather than logical. They've gotten attached to all the stories around black holes and all the science fiction and all the crazy ideas (parallel universes! white holes! wormholes!) and a general sense of "woo" that I for one do not find very appealing, and what people are reacting to is the loss of that, not the idea that the universe probably won't have any infinitely dense points... when the universe doesn't seem to have any points in it in the first place. (To forstall another common rabbit trail, I don't think the universe is continuous... but that doesn't mean I automatically think it must be discrete: https://news.ycombinator.com/item?id=38433917 https://news.ycombinator.com/item?id=38433917 )

vecter 2y ago

The general belief that singularities are “unphysical” and reflect a flaw in our models than actual reality. Hard to prove definitely right now of course.

hparadiz 2y ago
I always thought the concept of a singularity here was just to make the math slightly simpler. That is to say that a black hole is still a spherical body with a set diameter. We just can't see it so there's no way to verify other than the fact that we can see the border of the event horizon.
- atombender 2y ago
  As far as I know, that very much isn't the case. The singularity is a result of the math, not a trick to simplify it. My understanding is that many researchers do think it's a "placeholder" representing our lack of insight into how physics behave at those scales, and not a real physical phenomenon, and that it will one day be possible to work past it. I believe Kerr and Penrose (both of whom did some of the most foundational work on black holes) believe it's a mathematical artifact.
  - hparadiz 2y ago
    My random thoughts on this: - Is the math referring to the center of gravity as the singularity? Because even a sub black hole mass object would have that. - Why is there an assumption that just after a mass becomes a black hole the matter inside it suddenly compresses further when the actual gravity of the object has only slightly increased? - Is there a maximum density of matter in the universe and if the black hole even reaches that? - Wouldn't you need that number to be infinite if the black hole itself is infinitely small? - If the black hole does have a mass inside it... Do the light particles trapped inside the black hole form a blanket around the existing matter?
    - Dylan16807 2y ago
      > - Why is there an assumption that just after a mass becomes a black hole the matter inside it suddenly compresses further when the actual gravity of the object has only slightly increased? Yeah, that seems like an important thing to address. Black holes don't even have to be high density, or have much matter in the center at the time of formation. If you arrange enough big chunks of metal into a spherical-shell constellation, then drop them all toward their mutual center, they can reach the threshold to become a black hole before they even start colliding. What happens around that time, and what specifically does "singularity" mean (because I see people using it in very different ways). > - Is there a maximum density of matter in the universe and if the black hole even reaches that? > - Wouldn't you need that number to be infinite if the black hole itself is infinitely small? Black holes are the benchmark for maximum density. The event horizon is always exactly at the limit. By "black hole itself" do you mean something other than the event horizon? But that maximum density depends on size, smaller things can be denser and bigger things have to be less dense.
      - hparadiz 2y ago
        > If you arrange enough big chunks of metal into a spherical-shell constellation, then drop them all toward their mutual center, they can reach the threshold to become a black hole before they even start colliding. When I say "black hole itself" I imagine any combination of mass at it's center that provides enough density to form a gravitational pull that will trap light.
      - pixl97 2y ago
        > What happens around that time I can imagine it's something stupidly energetic. If you don't want them turning into a hot ball of neutrons first you're either going to have to spend a lot of energy keeping them apart or they are going to be orbiting a virtual center and it will take far longer for them to reach the center singularity than you expect. This will follow the laws of the 3(+) body problem so you won't be able to calculate a perfect impact, so the birth of the singularity will be shrouded in very high energy particles escaping. Nature abhors a naked singularity.
vlovich123 2y ago
All we know is that we’ve made a lot of crazy predictions about the structure and behavior of black holes well before we measured them and so far they’ve aligned remarkably close to the predictions. If there is a difference, it’s about the interior not how it shows up in our universe. And since we can never see inside the black hole, any alternative model would have to better explain some phenomena our existing models can’t or be even easier than relativity and explain the same things. We know string theory is hard to make consistent and it struggles to create falsifiable experiments. I would bet on relatively remaining a very very long time until we figure out how to unify quantum and relativity.

ikiris 2y ago

the dunning kruger effect

jerf 2y ago

To the best of my knowledge, none of the competing theories for integration have singularities in them. It is difficult to know what a "singularity" would look like in a universe that doesn't seem to have 0-dimensional mathematical points in it. It isn't that surprising that continuous theories have singularities in them. Reality doesn't seem to be continuous in the sense that real numbers are. It is unknown if Navier-Stokes can develop singularities in finite time, but in the real universe it won't matter because they won't lead to singularities in the real universe because it is ultimately just an approximation. "Interesting things" may happen around whatever those conditions are but nothing will be accelerated to infinite speed in the real universe. It is another theory that is a real-number-based continuous approximation made useful by the fact that real numbers are easier to do math with than physical quantities, but the real universe does not have plain real numbers in it. (This is subtly different than the controversial statement that it isn't made out of real numbers at all. But it does not have "plain" real numbers. You certainly can not expect to pull out a microscope and peer at the universe at a scale of 10^-10000 meters and see a universe that behaves exactly the same, just at a smaller scale. Our universe is definitely not scale-invariant.) I think this is likely to be a rather accurate metaphor. To be honest, I don't see a lot of positive reason to assume that the singularities are going to be "real". I think physicists initial reactions to the idea were correct and remain correct. I think the reasons why people think otherwise are emotional rather than logical. They've gotten attached to all the stories around black holes and all the science fiction and all the crazy ideas (parallel universes! white holes! wormholes!) and a general sense of "woo" that I for one do not find very appealing, and what people are reacting to is the loss of that, not the idea that the universe probably won't have any infinitely dense points... when the universe doesn't seem to have any points in it in the first place. (To forstall another common rabbit trail, I don't think the universe is continuous... but that doesn't mean I automatically think it must be discrete: https://news.ycombinator.com/item?id=38433917 https://news.ycombinator.com/item?id=38433917 )