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Time doesn’t magically freeze inside of a black hole. That is a misunderstanding of what happens to light rays carrying the image of the infalling diver as they

by db48x 2y ago

Time doesn’t magically freeze inside of a black hole. That is a misunderstanding of what happens to light rays carrying the image of the infalling diver as they approach the event horizon. From the perspective of an outside observer, those light rays are slowed down more and more and light from the instant of crossing the event horizon never actually arrives; it appears to take an infinite amount of time to do so. The mistake is to think that the object is still there, hovering at the event horizon, for an infinite amount of time. The reality is that the diver notices nothing unusual as they cross the event horizon; they may not even be able to tell exactly when it happens. They certainly do not freeze in place forever.

Jensson 2y ago
> The reality is that the diver notices nothing unusual as they cross the event horizon That doesn't mean that he actually crosses it from our reference frame. Relativity is all about understanding that time is relative, that applies here as well, except that there is no connection between the two reference frame unlike regular space, so we can't say anything about how time flows inside of a black hole from our perspective. Basically what I am saying is, you can't say whether the singularity has actually formed, since your reference frame is just as connected to the instant anything fell into the black hole as it is connected to the end state of the singularity. That makes it just as valid to say that things freeze the instant they touch the black hole as to say that they merge with the singularity the instant they touch it, since both are equally valid viewpoints from our perspective.
- db48x 2y ago
  There is no disconnection between the interior of the black hole and the exterior. They are smoothly and continuously connected, and the “normal” axis of time blends seamlessly with the “bent” axis of time inside the black hole. That’s why orbits are so weird outside the black hole. You’re simply wrong about this.
  - Jensson 2y ago
    So how long does it take for a thing to enter the singularity as seen from our reference frame? If you say there is no way to answer it, then you say that I am right, so I'd like to see a link to a formula saying how long that takes from our point of view. I studied up to a masters in physics, I've seen the math, I don't believe there is a way to calculate that, there is no way to compare time inside with time outside. Edit: I'd love to see such a formula if there is one btw, so if you know there is one please link!
    - qubitcoder 2y ago
      I'm not sure what you mean by "enter the singularity". Once an object has crossed the event horizon, its light rays can no longer reach us. From an outside perspective, the time required would be based on the object's orbit and when it intersected with the event horizon. When you say "thing", it's more like photons. While thought experiments of a diver falling into a black hole are fun to ponder, nature isn't so gentle. The corona, tidal forces, magnetic fields--and other factors--would obliterate matter into a stream of subatomic particles and light before crossing the event horizon. So the concept of a "thing" moving inside a black hole is likely misguided. It’s been called one of the most extreme physical environments in the universe. Strong magnetic fields threading the inner accretion disk extend out of it, creating a tenuous, turbulent, billion-degree cloud. Particles in the corona orbit the black hole at velocities approaching the speed of light. It’s a source of X-rays with much higher energies than those emanating from the accretion disk, but astronomers are still trying to figure out its extent, shape, and other characteristics. [0] NASA provides a fantastic overview here [0]. A few resources to check out: Sean Carrol, PBS Space Time, Ask a Spaceman, and Why this Universe are all great resources--and frequently do deep dives into this topic. [0] https://science.nasa.gov/universe/black-holes/anatomy/ https://science.nasa.gov/universe/black-holes/anatomy/
- MaxikCZ 2y ago
  You are correct that we just dont know what happens behind event horizont, from our perspective at least. Currently our best theory says nothing from inside can leak out, so in that spirit saying infalling matter ends up in singularity is as based in reality as it transforming into unicorns. Regardless, its important to keep in mind that this is valid _only_ from our perspective, that from the perspective of infalling matter something _real_ happens, and that real thing that happens is probably not completely disconnected from rules we perceived in our own universe. Throwing hands up and saying "we cant tell whats inside, so why are we even arguing about what we think happens there" is certainly a way to look at things if your only motivation is to find out whats happening inside, but that is not all we are after. We are trying to use all we currently know to reason about how the inside might look, any possibility, and try to work out backwards what unforseen implications it might have for our reality. We are not saying that inside blackhole is sigularity, we are saying that, given our understanding of how outside looks, there might be a singularity inside. We also know the math that yields us this singularity is probably wrong (infinite), and actively are trying to figure out whats wrong with it. We are using this imaginated realoty to work backwards what we might have gotten wrong, and perhaps in this case its not even the roght way of thinking to solve this mystery; it just worked for us before, so we trying. If you figure out whats actually happening there, and find some way to connect it to rules of our universe, everyone will cheer. If its by first discovering new effect in our universe that would elegantly fit into blackholes, or in the stroke of genius come up with a pure theory enlighting some real observations, nobody would care. Its just when we throw a mass, it keeps going. It makes more sense to think that it goes the same inside blackhole, but maybe not. We just dont know..
  - Jensson 2y ago
    > Its just when we throw a mass, it keeps going You wouldn't feel going through the event horizon of a large black hole, so I see no reason why that mass would somehow just collapse into a singularity. Also the math for a black hole states that when the black holes density reaches below the density of the universe, the black holes event horizon will expand and encompass the whole universe, meaning matter doesn't even have to fall into the black hole, the black hole could just grow into the matter and then you don't even have a velocity you just have matter entering the black hole. We know the two above are how the math for black holes work, none of those produce likely singularities, because there is no force compressing that into a singularity. So if singularities exists in black holes, it would just be some of them, and not all parts of the black hole would have to be a part of that singularity.
- db48x 2y ago
  > That doesn't mean that he actually crosses it from our reference frame. This specifically is an incorrect understanding. All events happen in all reference frames. There are no situations where an event that happens in one reference frame fails to happen in another. At worst (or best, depending on how you view it) we can disagree about the _order_ of events, but not which events actually happened.
  - rbanffy 2y ago
    It’s not that the crossing fails to happen. It’s just that, from the outside it takes an infinitely long time to happen and, for the diver’s perspective, it’s the universe outside that ended really quickly.

by db48x 2y ago

Jensson 2y ago

> The reality is that the diver notices nothing unusual as they cross the event horizon That doesn't mean that he actually crosses it from our reference frame. Relativity is all about understanding that time is relative, that applies here as well, except that there is no connection between the two reference frame unlike regular space, so we can't say anything about how time flows inside of a black hole from our perspective. Basically what I am saying is, you can't say whether the singularity has actually formed, since your reference frame is just as connected to the instant anything fell into the black hole as it is connected to the end state of the singularity. That makes it just as valid to say that things freeze the instant they touch the black hole as to say that they merge with the singularity the instant they touch it, since both are equally valid viewpoints from our perspective.

db48x 2y ago
There is no disconnection between the interior of the black hole and the exterior. They are smoothly and continuously connected, and the “normal” axis of time blends seamlessly with the “bent” axis of time inside the black hole. That’s why orbits are so weird outside the black hole. You’re simply wrong about this.
- Jensson 2y ago
  So how long does it take for a thing to enter the singularity as seen from our reference frame? If you say there is no way to answer it, then you say that I am right, so I'd like to see a link to a formula saying how long that takes from our point of view. I studied up to a masters in physics, I've seen the math, I don't believe there is a way to calculate that, there is no way to compare time inside with time outside. Edit: I'd love to see such a formula if there is one btw, so if you know there is one please link!
  - qubitcoder 2y ago
    I'm not sure what you mean by "enter the singularity". Once an object has crossed the event horizon, its light rays can no longer reach us. From an outside perspective, the time required would be based on the object's orbit and when it intersected with the event horizon. When you say "thing", it's more like photons. While thought experiments of a diver falling into a black hole are fun to ponder, nature isn't so gentle. The corona, tidal forces, magnetic fields--and other factors--would obliterate matter into a stream of subatomic particles and light before crossing the event horizon. So the concept of a "thing" moving inside a black hole is likely misguided. It’s been called one of the most extreme physical environments in the universe. Strong magnetic fields threading the inner accretion disk extend out of it, creating a tenuous, turbulent, billion-degree cloud. Particles in the corona orbit the black hole at velocities approaching the speed of light. It’s a source of X-rays with much higher energies than those emanating from the accretion disk, but astronomers are still trying to figure out its extent, shape, and other characteristics. [0] NASA provides a fantastic overview here [0]. A few resources to check out: Sean Carrol, PBS Space Time, Ask a Spaceman, and Why this Universe are all great resources--and frequently do deep dives into this topic. [0] https://science.nasa.gov/universe/black-holes/anatomy/ https://science.nasa.gov/universe/black-holes/anatomy/
MaxikCZ 2y ago
You are correct that we just dont know what happens behind event horizont, from our perspective at least. Currently our best theory says nothing from inside can leak out, so in that spirit saying infalling matter ends up in singularity is as based in reality as it transforming into unicorns. Regardless, its important to keep in mind that this is valid _only_ from our perspective, that from the perspective of infalling matter something _real_ happens, and that real thing that happens is probably not completely disconnected from rules we perceived in our own universe. Throwing hands up and saying "we cant tell whats inside, so why are we even arguing about what we think happens there" is certainly a way to look at things if your only motivation is to find out whats happening inside, but that is not all we are after. We are trying to use all we currently know to reason about how the inside might look, any possibility, and try to work out backwards what unforseen implications it might have for our reality. We are not saying that inside blackhole is sigularity, we are saying that, given our understanding of how outside looks, there might be a singularity inside. We also know the math that yields us this singularity is probably wrong (infinite), and actively are trying to figure out whats wrong with it. We are using this imaginated realoty to work backwards what we might have gotten wrong, and perhaps in this case its not even the roght way of thinking to solve this mystery; it just worked for us before, so we trying. If you figure out whats actually happening there, and find some way to connect it to rules of our universe, everyone will cheer. If its by first discovering new effect in our universe that would elegantly fit into blackholes, or in the stroke of genius come up with a pure theory enlighting some real observations, nobody would care. Its just when we throw a mass, it keeps going. It makes more sense to think that it goes the same inside blackhole, but maybe not. We just dont know..
- Jensson 2y ago
  > Its just when we throw a mass, it keeps going You wouldn't feel going through the event horizon of a large black hole, so I see no reason why that mass would somehow just collapse into a singularity. Also the math for a black hole states that when the black holes density reaches below the density of the universe, the black holes event horizon will expand and encompass the whole universe, meaning matter doesn't even have to fall into the black hole, the black hole could just grow into the matter and then you don't even have a velocity you just have matter entering the black hole. We know the two above are how the math for black holes work, none of those produce likely singularities, because there is no force compressing that into a singularity. So if singularities exists in black holes, it would just be some of them, and not all parts of the black hole would have to be a part of that singularity.
db48x 2y ago
> That doesn't mean that he actually crosses it from our reference frame. This specifically is an incorrect understanding. All events happen in all reference frames. There are no situations where an event that happens in one reference frame fails to happen in another. At worst (or best, depending on how you view it) we can disagree about the _order_ of events, but not which events actually happened.
- rbanffy 2y ago
  It’s not that the crossing fails to happen. It’s just that, from the outside it takes an infinitely long time to happen and, for the diver’s perspective, it’s the universe outside that ended really quickly.