stuff thrown into the black hole increases the horizon area and possibly modifies its geometry, and in return the horizon affects the spatial infinity (the area around the horizon).
That’s outside affecting outside, not inside affecting outside.
The same is for the cosmological horizon, which is effectively just another kind of singularity.
That’s outside affecting outside, not inside affecting outside.
Hmm… let’s taboo “outside” and “inside”. The properties of stuff within the horizon affect the properties of the horizon, which in turn affect the properties of space-matter at spatial infinity. Is this formulation more acceptable?
Horizon is not a singularity.
Right, I’ll rephrase: the same goes for the cosmological horizon, which effectively ‘surrounds’ just another kind of singularity.
The properties of stuff within the horizon affect the properties of the horizon
Wrong. There could be tons of different things going on inside, absolutely indistinguishable from outside, which only sees mass, electric charge and angular momentum. There is no causal connection from inside to outside whatsoever, barring FTL communication.
Right, I’ll rephrase: the same goes for the cosmological horizon, which effectively ‘surrounds’ just another kind of singularity.
Wrong again. There is no singularity of any kind behind the cosmological horizon (which is not a closed surface to begin with, so it cannot “surround” anything). Well, there might be black holes and stuff, or there might not be, but there is certainly not a requirement of anything singular being there. Consider googling the definition of singularity in general relativity.
Wrong. There could be tons of different things going on inside, absolutely indistinguishable from outside, which only sees mass, electric charge and angular momentum. There is no causal connection from inside to outside whatsoever, barring FTL communication.
Unless the “inside” was spontaneously materialized into existence while simultaneously a different chunk of the singularity’s mass blinked out of existence in manners which defy nearly all the physics I know, then there still remains a causal connection from the “disappearance” of this stuff that’s “inside” from the world “outside” at some point in outside time frames, AFAICT. This disappearance of specific pieces of matter and energy seems to more than qualify as a causal effect, when compared to counterfactual futures where they do not disappear.
Also, the causal connection [Inside → Mass → Outside] pretty much looks like a causal connection from inside to outside to me. There’s this nasty step in the middle that blurs all the information such that under most conceivable circumstances there’s no way to tell which of all possible insides is the “true” one, but combined with the above about matter disappearance can still let you concentrate your probability mass, compared to meaningless epiphenomena that cover the entire infinite hypothesis space (minus one single-dimensional line representing its interaction with anything that interacts with our reality in any way) with equal probability because there’s no way it could even in principle affect us even in CTCs, FTL, timeless or n-dimensional spaces, etc.
(Note: I’m not an expert on mind-bending hypothetical edge cases of theoretical physics, so I’m partially testing my own understanding of the subject here.)
I’m partially testing my own understanding of the subject here.
Most of what you said is either wrong or meaningless, so I don’t know where to begin unraveling it, sorry. Feel free to ask simple questions of limited scope if you want to learn more about black holes, horizons, singularities and related matters. The subject is quite non-trivial and often counter-intuitive.
In more vague, amateur terms, isn’t the whole horizon thing always the same case, i.e. it’s causally linked to the rest of the universe by observations in the past and inferences using presumed laws of physics, even if the actual state of things beyond the horizon (or inside it or whatever) doesn’t change what we can observe?
The event horizon in an asymptotically flat spacetime (which is not quite the universe we live in, but a decent first step) is defined as the causal past of the infinite causal future. This definition guarantees that we see no effects whatsoever from the part of the universe that is behind the event horizon. The problem with this definition is that we have to wait forever to draw the horizon accurately. Thus there are several alternative horizons which are more instrumentally useful for theorem proving and/or numerical simulations, but are not in general identical to the event horizon. The cosmological event horizon is a totally different beast (it is similar to the Rindler horizon, used to derive the Unruh effect), though it does share a number of properties with the black hole event horizon. There are further exciting complications once you get deeper into the subject.
Wrong. There could be tons of different things going on inside, absolutely indistinguishable from outside, which only sees mass, electric charge and angular momentum.
Nitpick: this is only true for a stationary black hole. If you throw something sufficiently big in, you would expect the shape of the horizon to change and bulge a bit, until it settles down into a stationary state for a larger black hole. You are of course correct that this does not allow anything inside to send a signal to the outside.
Nitpick: this is only true for a stationary black hole.
Right, I didn’t want to go into these details, MrMind seems confused enough as it is. I’d have to explain that the horizon shape is only determined by what falls in, and eventually talk about apparent and dynamical horizons and marginally outer trapped surfaces…
Wrong. There could be tons of different things going on inside, absolutely indistinguishable from outside, which only sees mass, electric charge and angular momentum.
Also entropy. Anyway, those are determined by the mass, electrical charge and angular momentum of the matter that fell inside. We may not want to call it a causal connection, but it’s certainly a case of properties within determining properties outside.
There is no causal connection from inside to outside whatsoever, barring FTL communication.
There is no direct causal connection, meaning a worldline from the inside to the outside of the black hole. But even if the horizon screens almost all of the infalling matter properties, it doesn’t screen everything (and probably, but this is a matter of quantum gravity, doesn’t screen nothing).
Wrong again. There is no singularity of any kind behind the cosmological horizon (which is not a closed surface to begin with, so it cannot “surround” anything). Well, there might be black holes and stuff, or there might not be, but there is certainly not a requirement of anything singular being there. Consider googling the definition of singularity in general relativity.
I’ll admit to not have much knowledge about this specific theme, and I’ll educate myself more properly, but in the case of my earlier sentence I used “singularity” as a mathematical term, referring to a region of spacetime in which the GR equations acquire a singular value, so not specifically to a gravitational singularity like a black-hole or a domain wall. In the case of most commonplace cosmological horizons, this region is simply space-like infinity.
That’s outside affecting outside, not inside affecting outside.
Horizon is not a singularity.
Hmm… let’s taboo “outside” and “inside”. The properties of stuff within the horizon affect the properties of the horizon, which in turn affect the properties of space-matter at spatial infinity. Is this formulation more acceptable?
Right, I’ll rephrase: the same goes for the cosmological horizon, which effectively ‘surrounds’ just another kind of singularity.
Wrong. There could be tons of different things going on inside, absolutely indistinguishable from outside, which only sees mass, electric charge and angular momentum. There is no causal connection from inside to outside whatsoever, barring FTL communication.
Wrong again. There is no singularity of any kind behind the cosmological horizon (which is not a closed surface to begin with, so it cannot “surround” anything). Well, there might be black holes and stuff, or there might not be, but there is certainly not a requirement of anything singular being there. Consider googling the definition of singularity in general relativity.
Unless the “inside” was spontaneously materialized into existence while simultaneously a different chunk of the singularity’s mass blinked out of existence in manners which defy nearly all the physics I know, then there still remains a causal connection from the “disappearance” of this stuff that’s “inside” from the world “outside” at some point in outside time frames, AFAICT. This disappearance of specific pieces of matter and energy seems to more than qualify as a causal effect, when compared to counterfactual futures where they do not disappear.
Also, the causal connection [Inside → Mass → Outside] pretty much looks like a causal connection from inside to outside to me. There’s this nasty step in the middle that blurs all the information such that under most conceivable circumstances there’s no way to tell which of all possible insides is the “true” one, but combined with the above about matter disappearance can still let you concentrate your probability mass, compared to meaningless epiphenomena that cover the entire infinite hypothesis space (minus one single-dimensional line representing its interaction with anything that interacts with our reality in any way) with equal probability because there’s no way it could even in principle affect us even in CTCs, FTL, timeless or n-dimensional spaces, etc.
(Note: I’m not an expert on mind-bending hypothetical edge cases of theoretical physics, so I’m partially testing my own understanding of the subject here.)
Most of what you said is either wrong or meaningless, so I don’t know where to begin unraveling it, sorry. Feel free to ask simple questions of limited scope if you want to learn more about black holes, horizons, singularities and related matters. The subject is quite non-trivial and often counter-intuitive.
Hmm, alright.
In more vague, amateur terms, isn’t the whole horizon thing always the same case, i.e. it’s causally linked to the rest of the universe by observations in the past and inferences using presumed laws of physics, even if the actual state of things beyond the horizon (or inside it or whatever) doesn’t change what we can observe?
The event horizon in an asymptotically flat spacetime (which is not quite the universe we live in, but a decent first step) is defined as the causal past of the infinite causal future. This definition guarantees that we see no effects whatsoever from the part of the universe that is behind the event horizon. The problem with this definition is that we have to wait forever to draw the horizon accurately. Thus there are several alternative horizons which are more instrumentally useful for theorem proving and/or numerical simulations, but are not in general identical to the event horizon. The cosmological event horizon is a totally different beast (it is similar to the Rindler horizon, used to derive the Unruh effect), though it does share a number of properties with the black hole event horizon. There are further exciting complications once you get deeper into the subject.
Nitpick: this is only true for a stationary black hole. If you throw something sufficiently big in, you would expect the shape of the horizon to change and bulge a bit, until it settles down into a stationary state for a larger black hole. You are of course correct that this does not allow anything inside to send a signal to the outside.
Right, I didn’t want to go into these details, MrMind seems confused enough as it is. I’d have to explain that the horizon shape is only determined by what falls in, and eventually talk about apparent and dynamical horizons and marginally outer trapped surfaces…
Also entropy. Anyway, those are determined by the mass, electrical charge and angular momentum of the matter that fell inside. We may not want to call it a causal connection, but it’s certainly a case of properties within determining properties outside.
There is no direct causal connection, meaning a worldline from the inside to the outside of the black hole. But even if the horizon screens almost all of the infalling matter properties, it doesn’t screen everything (and probably, but this is a matter of quantum gravity, doesn’t screen nothing).
I’ll admit to not have much knowledge about this specific theme, and I’ll educate myself more properly, but in the case of my earlier sentence I used “singularity” as a mathematical term, referring to a region of spacetime in which the GR equations acquire a singular value, so not specifically to a gravitational singularity like a black-hole or a domain wall. In the case of most commonplace cosmological horizons, this region is simply space-like infinity.