10 ms·

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as

There is a fascinating PBS Space Time video[1] about black holes that questions the very existence of whatever is "inside" a black hole. They point out that as you approach a black hole, your proper time is advancing slower and slower when compared to an observer located far away from the black hole (like us, on Earth). That means that from the point of view of this far observer, nothing happens inside a black hole until an infinite amount of time. In other words, what is inside a black hole is separated from us not by a space-like frontier, but a time-like one. Events behind the event horizon are postponed to "the end of times". Does it even make sense to say that those events exist, then? Are they any more real than fairy tales or mathematical equations? If not, we can make any speculation we want, including the existence of alien civilizations. 1. https://www.youtube.com/watch?v=vNaEBbFbvcY https://www.youtube.com/watch?v=vNaEBbFbvcY

garmaine 9y ago
No it doesn’t make sense. That explanation is privledging remote observers frames of reference to “explain” what happens in another frame of reference. That’s a violation of our modern understanding of physics.
- grondilu 9y ago
  It's not "privileging" any thing in the sense that it does not claim one point of view is more valid than the other. It's just that one of these point of view is ours, and from this point of view, the other point of view does not correspond to any event that will actually happen, like ever. In other words, the "happening of events" is a relative concept. Just like simultaneity. Not only two events can happen at the same time or not depending on who is observing them, but the very happening of an event can also depend on who is observing (or not observing) it. That "happening of events" is very close to a definition one can give to the concept of reality. So one might conclude that reality is a relative concept.
hliyan 9y ago
I imagine this as time asymptotically slowing as you approach the singularity so that the singularity is forever stuck at the time of the supernova explosion that gave birth to it. You can never reach it because you and your movements too, slow down the closer you get. Is that correct?
- grondilu 9y ago
  A traveler can reach it all right, but only from his own point of view. From the point of view of almost everyone else in the Universe, including us on Earth, it will never ever reach it. It's like the traveler has jumped into an other universe "located" in an infinitely distant future.
  - koboll 9y ago
    So let's say I fall into a black hole. And then four billion years later, someone else falls into a black hole from the same direction. From an outside perspective at a point nearly infinitely far away in time, we would seem to slow until we are right next to each other at the event horizon, correct? Does this mean everything that falls into a black hole crosses the event horizon (from their perspective) at the same moment, a moment which only exists from the crossers' perspective, as it is always infinitely far away from a perspective outside the event horizon?
    - Santosh83 9y ago
      Yup, from an outside perspective you simply cannot see something cross the event horizon no matter how long you wait, except by detecting the added mass.
    - Balgair 9y ago
      > From an outside perspective at a point nearly infinitely far away in time, we would seem to slow until we are right next to each other at the event horizon, correct? Incorrect. You would still be relativisticly separated and this would be measurable especially at infinity. You would be accelerated by 4 billion more years and would have that much more relativistic acceleration in signals you sent out. This could be monitored and the outside observers would be able to tell the difference. The second person would be more blue shifted compared to you (clock ticking faster). > Does this mean everything that falls into a black hole crosses the event horizon (from their perspective) at the same moment, a moment which only exists from the crossers' perspective, as it is always infinitely far away from a perspective outside the event horizon? No, their clocks tick away just like they always did. They cross the event horizon just as they thought they would. They do 'see' the universe's clocks accelerate along though. But they do cross it nonetheless. Note: By 'see' I mean that the rest of the universe blue shifts to infinity and the Lorentz transformation causes the incoming radiation to be directed to directly in front of you. Only when you cross the event horizon, the incoming radiation from the 'outside' turns into an infinitely energetic (infinite blue shift) beam of radiation coming directly at you. In your reference frame, you vaporize. This is my BHs are soooo crazy. When we run the numbers, the Quantum Mechanical effects really do affect things. Infinitely small wavelength light isn't something we can really handle, the Plank Length should come into play. But General Relativity don't care. This is why we really need Quantum Gravity, because nothing makes sense.
olegkikin 9y ago
That's the thing that never made sense to me about the black holes. The closer you are to the event horizon, the faster the time passes for the universe around you. So reaching the event horizon should take infinite amount of the "outside time", so right before you reach the horizon, you should see the whole future of the universe, including its end, if there's any. So how do black holes gain any mass then?
- phamilton 9y ago
  Wouldn't it just depend on your definition of the area of the black hole? By your logic, I certainly agree that black holes having mass beyond their event horizon is an impossibility from an observation perspective, but how far outside the event horizon do we include in our definition of a black hole? Far enough out, we could certainly observe them gaining mass.
- grondilu 9y ago
  > So how do black holes gain any mass then? Well, from our point of view all incoming mass gets stuck very close to the event horizon. That's not too surprising considering the amount of information of a black hole is proportional to its surface area. So from a far away observer a black hole is more like a sticky sphere than an hollow ball.
  - metaobject 9y ago
    Doesn't the surface area increase as the BH takes on more mass?
    - grondilu 9y ago
      Yes, but the mass does not have to cross the event horizon for that, does it? At that point we probably can't tell more without diving into the math, and it's beyond my abilities. Yet the gross idea does not seem absurd to me.
    - nightcracker 9y ago
      I like the analogy of a snowball, nothing ever enters it yet it grows.
wcarss 9y ago
off-topic a bit: does anyone have suggestions for paths for the layperson toward being able to reason and intuit about this stuff at one level beyond pop physics claptrap? I have heard "the theoretical minimum" suggested in the past, but I haven't heard from anyone who has actually used it to go from zero to say, general relativity, only people who think it sounds good. It also seems like a steep investment -- I just want to have a decent enough grasp to separate sense from nonsense and hold a picture in my mind. One related thing I have wished existed was a good place to ask questions about and discuss topics like this while learning them, but it seems like in theoretical physics, everyone (including myself) has an infinite number of different stupid questions and misconceptions, to the point that we drown each other out, and answers to our questions often have little cross-applicability. So, would love ideas for either!
- whatshisface 9y ago
  The only well-traveled path to understanding physics starts at "highschooler with a lot of confidence in their math skills," and it takes four years minimum. Anything else is going to be a long shot, just by virtue of the fact that nobody's doing it (for the most part). Nobody has ever discovered a way to truthfully map physics concepts into English sentences that you can understand without having to have explored the entire definition tree.
  - dictum 9y ago
    Concurrently, every attempt to map physics concepts into English is met by a barrage of "well, actually".
    - whatshisface 9y ago
      That's because the mappings always fail - not so much a concurrent thing as a consequence. (For comparison, you can say everything about Roman troop organization in English, because that's native to how the information exists in the first place. You won't get any "well, actually" about the size of a legion, because it involves words and concepts that everyone already knows.)
IntronExon 9y ago
This strikes me as an issue between understanding these events from the point of view of an external observer, and a test particle or person falling into the hole. From the POV of the observer, your statements are largely accurate, for certain types of universes. For the test particle, there is no freeze frame, all proceeds normally. The key is the Relative in Relativity. Truthfully, there is no clear answer as to what a black hole has for an interior, or if it really has one. Holographic theorists would argue that the event horizon is the black hole, String theorists would argue that there is an interior, but no singularity. We just don’t know.
- dhruvparamhans 9y ago
  Probably the most accurate comment here.
pwaai 9y ago
> https://www.youtube.com/watch?v=vNaEBbFbvcY https://www.youtube.com/watch?v=vNaEBbFbvcY This is mind blowing...shatters my misconception of blackholes....is there any more books on this?
- provost 9y ago
  It was interesting to watch, but the presenter presents everything as truth, but aren’t many of his explanations still theories? I’d like to see what other competing theories there are..
  - grondilu 9y ago
    I think most of what he said is just an interpretation of what the math of classical black-holes says (basically the Schwartzschild equation). This math is uncontroversial and there is no better theory of a black hole, at least at this level of detail. If I understand correctly competing theories disagree on more complicated descriptions, those that ask different questions or want to describe more details.
- liardiary 9y ago
  Black holes and time warps by Kip Thorne. Great book and great guy.
- Quiark 9y ago
  The most updated book I read was The Science of Interstellar by Kip Thorne
analog31 9y ago
Here's something I've wondered about black holes, related to what's inside. Simplistically, there must be mass inside, i.e., every black hole has a mass that can somehow be measured, e.g., by orbital velocities of satellites. And the mass-energy has to equal the mass-energy that has fallen in. So far so good. But the stuff that falls in is not purely described by its mass. It also has angular momentum, electrical charge, maybe a few other quantities such as charm and strangeness (speculating here). So the black hole must have a net angular momentum, electrical charge, charm, and strangeness. Electrical charge could be measured by holding an electrometer next to the black hole. And so forth. So far I've described 5 quantities that "describe" a black hole. So my question is: How many more are there? What's the total number of numbers that accompany a particle as it gets sucked in? Suppose it's a small number, like 11. Does that place an upper limit on the information content of a black hole, and hence the possibility of describing a "civilization" inside it?
- jepler 9y ago
  It sounds like your line of thinking leads to the https://en.wikipedia.org/wiki/Black_hole_information_paradox https://en.wikipedia.org/wiki/Black_hole_information_paradox
- alde 9y ago
  You have almost formulated the no-hair theorem. https://en.wikipedia.org/wiki/No-hair_theorem https://en.wikipedia.org/wiki/No-hair_theorem
  - andrewflnr 9y ago
    I never thought of that in the context of strangeness, lepton number, and other conserved quantities. I don't think strangeness is really measurable (and I don't remember if it's technically conserved), but black holes should probably preserve lepton number somehow. Is that a quantum gravity sort of problem?
    - IntronExon 9y ago
      It might be, in that a Q-ball or something similar could there instead of a singularity, or it could be that there is no interior. Remember that the Holographic Principle implies that the total entropy of the volume of the hole can be encoded in the 2D event horizon of the hole. The singularity is a prediction of GTR, but GTR breaks down there too. This is why black holes are so exciting in the context of new theories which are complementary to GTR!
dustingetz 9y ago
Between reality and maths, the maths are the more fundamental thing that is used to explain reality. What you call reality is just some circumstances that your brain got used to.
- visarga 9y ago
  On the contrary, maths are just approximations of reality, not something fundamental to it.
  - pbhjpbhj 9y ago
    I think the jury is still out on mathematical realism. Our current physics is almost certainly an imperfect description/model however.
    - visarga 9y ago
      Even if we'd know the perfect model for particle physics, we still can't apply math straight for simulation. We always prefer an approximation, all real world models are approximations.
make3 9y ago
not an physicist, but from the point of view of the thing going on the black whole, time still goes on smoothly. My understanding is that the inside of the black whole becomes like a new universe, effectively cut from the previous one from the perspective of causality
v_lisivka 9y ago
But black hole has center, where gravity forces from shell negates each other, which has zero gravity, thus normal speed.
brianberns 9y ago
Our own past (say, 1974, for example) is also “separated from us not by a space-like frontier, but a time-like one“. Would you say that the past is not real?
- grondilu 9y ago
  The frontier I was talking about is impassable. It's "infinitely in the future", aka "never". That's a whole different level of frontier, imho. Granted, there is a bit of tree falling[1] conundrum here, but that does not make the question less interesting (arguably, it even makes it all the more so). 1. https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest
hinkley 9y ago
I’ve wondered this too but I just had a thought. I ended up asking myself why any black hole is ever bigger than critical mass if this is true. Take a black hole that’s been slurping matter in and it’s all at the event horizon because as you say, it takes forever to cross. But as that mass builds and builds doesn’t the event horizon move? Take the scene to the limit. Say a black hole never absorbs anything. The amount of mass parked just above the horizon becomes so great that another black hole forms. Now you have two overlapping horizons, which can’t stay that way. What really happens is that the density of mass inside the radius near the black hole is sufficient to be a black hole of a larger diameter and then it just... is. I think that what this means is that you never get to the event horizon, but the horizon comes to you.
- computerex 9y ago
  There is so much speculation and misinformation here. One key idea of relativity is that laws of physics remain the same for all uniformly moving reference frames. Objects approaching and entering the event horizon experience time normally. For large black holes, a probe entering past the event horizon will continue to fall towards the singularity and experience time normally for a long time before being destroyed. To external observers, of course nothing can be observed as falling through the event horizon because not even light can escape past the event horizon. So no light from beyond the horizon of the probe can ever reach the observers. But that doesn't mean things can't go past the EH normally, or that here is some other magic happening like > I think that what this means is that you never get to the event horizon, but the horizon comes to you. A black hole is just another object with a very very powerful gravitational field.
  - hinkley 9y ago
    GP was talking about the passage of time from the standpoint of the external observer. About time dialation, not about the singularity. Near the horizon a heartbeat takes eons from the perspective of someone watching you fly into the black hole. Assuming of course that you haven’t already been torn to shreds by the high energy particles and gamma rays traveling perpendicular to your path...
gooseyard 9y ago
If you've not come across Lee Smolin's (speculative) writing on the Fecund Universes theory, you'll probably also love it. Don't have any links as I've only read about it in one of his books, but it's a fascinating idea.
teh_klev 9y ago
These videos are excellent, thanks for the link. Just spent the last hour or so having my mind blown over and over :) I also really need one of these: https://store.dftba.com/collections/all/products/heat-death-shirt https://store.dftba.com/collections/all/products/heat-death-...
mdpopescu 9y ago
> Events behind the event horizon are postponed to "the end of times". Thank you. To me, this has been obvious since I learned about the time slowing required by GR. Since then, I was unable to understand why people are talking about things "falling into" black holes. (There's an episode of SG-1 where a team is trapped by a black hole, and times keep slowing, but they never realize that this means that team WILL NEVER DIE.)

garmaine 9y ago

No it doesn’t make sense. That explanation is privledging remote observers frames of reference to “explain” what happens in another frame of reference. That’s a violation of our modern understanding of physics.

grondilu 9y ago
It's not "privileging" any thing in the sense that it does not claim one point of view is more valid than the other. It's just that one of these point of view is ours, and from this point of view, the other point of view does not correspond to any event that will actually happen, like ever. In other words, the "happening of events" is a relative concept. Just like simultaneity. Not only two events can happen at the same time or not depending on who is observing them, but the very happening of an event can also depend on who is observing (or not observing) it. That "happening of events" is very close to a definition one can give to the concept of reality. So one might conclude that reality is a relative concept.

hliyan 9y ago

I imagine this as time asymptotically slowing as you approach the singularity so that the singularity is forever stuck at the time of the supernova explosion that gave birth to it. You can never reach it because you and your movements too, slow down the closer you get. Is that correct?

grondilu 9y ago
A traveler can reach it all right, but only from his own point of view. From the point of view of almost everyone else in the Universe, including us on Earth, it will never ever reach it. It's like the traveler has jumped into an other universe "located" in an infinitely distant future.
- koboll 9y ago
  So let's say I fall into a black hole. And then four billion years later, someone else falls into a black hole from the same direction. From an outside perspective at a point nearly infinitely far away in time, we would seem to slow until we are right next to each other at the event horizon, correct? Does this mean everything that falls into a black hole crosses the event horizon (from their perspective) at the same moment, a moment which only exists from the crossers' perspective, as it is always infinitely far away from a perspective outside the event horizon?
  - Santosh83 9y ago
    Yup, from an outside perspective you simply cannot see something cross the event horizon no matter how long you wait, except by detecting the added mass.
  - Balgair 9y ago
    > From an outside perspective at a point nearly infinitely far away in time, we would seem to slow until we are right next to each other at the event horizon, correct? Incorrect. You would still be relativisticly separated and this would be measurable especially at infinity. You would be accelerated by 4 billion more years and would have that much more relativistic acceleration in signals you sent out. This could be monitored and the outside observers would be able to tell the difference. The second person would be more blue shifted compared to you (clock ticking faster). > Does this mean everything that falls into a black hole crosses the event horizon (from their perspective) at the same moment, a moment which only exists from the crossers' perspective, as it is always infinitely far away from a perspective outside the event horizon? No, their clocks tick away just like they always did. They cross the event horizon just as they thought they would. They do 'see' the universe's clocks accelerate along though. But they do cross it nonetheless. Note: By 'see' I mean that the rest of the universe blue shifts to infinity and the Lorentz transformation causes the incoming radiation to be directed to directly in front of you. Only when you cross the event horizon, the incoming radiation from the 'outside' turns into an infinitely energetic (infinite blue shift) beam of radiation coming directly at you. In your reference frame, you vaporize. This is my BHs are soooo crazy. When we run the numbers, the Quantum Mechanical effects really do affect things. Infinitely small wavelength light isn't something we can really handle, the Plank Length should come into play. But General Relativity don't care. This is why we really need Quantum Gravity, because nothing makes sense.

olegkikin 9y ago

That's the thing that never made sense to me about the black holes. The closer you are to the event horizon, the faster the time passes for the universe around you. So reaching the event horizon should take infinite amount of the "outside time", so right before you reach the horizon, you should see the whole future of the universe, including its end, if there's any. So how do black holes gain any mass then?

phamilton 9y ago
Wouldn't it just depend on your definition of the area of the black hole? By your logic, I certainly agree that black holes having mass beyond their event horizon is an impossibility from an observation perspective, but how far outside the event horizon do we include in our definition of a black hole? Far enough out, we could certainly observe them gaining mass.
grondilu 9y ago
> So how do black holes gain any mass then? Well, from our point of view all incoming mass gets stuck very close to the event horizon. That's not too surprising considering the amount of information of a black hole is proportional to its surface area. So from a far away observer a black hole is more like a sticky sphere than an hollow ball.
- metaobject 9y ago
  Doesn't the surface area increase as the BH takes on more mass?
  - grondilu 9y ago
    Yes, but the mass does not have to cross the event horizon for that, does it? At that point we probably can't tell more without diving into the math, and it's beyond my abilities. Yet the gross idea does not seem absurd to me.
  - nightcracker 9y ago
    I like the analogy of a snowball, nothing ever enters it yet it grows.

wcarss 9y ago

off-topic a bit: does anyone have suggestions for paths for the layperson toward being able to reason and intuit about this stuff at one level beyond pop physics claptrap? I have heard "the theoretical minimum" suggested in the past, but I haven't heard from anyone who has actually used it to go from zero to say, general relativity, only people who think it sounds good. It also seems like a steep investment -- I just want to have a decent enough grasp to separate sense from nonsense and hold a picture in my mind. One related thing I have wished existed was a good place to ask questions about and discuss topics like this while learning them, but it seems like in theoretical physics, everyone (including myself) has an infinite number of different stupid questions and misconceptions, to the point that we drown each other out, and answers to our questions often have little cross-applicability. So, would love ideas for either!

whatshisface 9y ago
The only well-traveled path to understanding physics starts at "highschooler with a lot of confidence in their math skills," and it takes four years minimum. Anything else is going to be a long shot, just by virtue of the fact that nobody's doing it (for the most part). Nobody has ever discovered a way to truthfully map physics concepts into English sentences that you can understand without having to have explored the entire definition tree.
- dictum 9y ago
  Concurrently, every attempt to map physics concepts into English is met by a barrage of "well, actually".
  - whatshisface 9y ago
    That's because the mappings always fail - not so much a concurrent thing as a consequence. (For comparison, you can say everything about Roman troop organization in English, because that's native to how the information exists in the first place. You won't get any "well, actually" about the size of a legion, because it involves words and concepts that everyone already knows.)

IntronExon 9y ago

This strikes me as an issue between understanding these events from the point of view of an external observer, and a test particle or person falling into the hole. From the POV of the observer, your statements are largely accurate, for certain types of universes. For the test particle, there is no freeze frame, all proceeds normally. The key is the Relative in Relativity. Truthfully, there is no clear answer as to what a black hole has for an interior, or if it really has one. Holographic theorists would argue that the event horizon is the black hole, String theorists would argue that there is an interior, but no singularity. We just don’t know.

dhruvparamhans 9y ago
Probably the most accurate comment here.

pwaai 9y ago

> https://www.youtube.com/watch?v=vNaEBbFbvcY https://www.youtube.com/watch?v=vNaEBbFbvcY This is mind blowing...shatters my misconception of blackholes....is there any more books on this?

provost 9y ago
It was interesting to watch, but the presenter presents everything as truth, but aren’t many of his explanations still theories? I’d like to see what other competing theories there are..
- grondilu 9y ago
  I think most of what he said is just an interpretation of what the math of classical black-holes says (basically the Schwartzschild equation). This math is uncontroversial and there is no better theory of a black hole, at least at this level of detail. If I understand correctly competing theories disagree on more complicated descriptions, those that ask different questions or want to describe more details.
liardiary 9y ago
Black holes and time warps by Kip Thorne. Great book and great guy.
Quiark 9y ago
The most updated book I read was The Science of Interstellar by Kip Thorne

analog31 9y ago

Here's something I've wondered about black holes, related to what's inside. Simplistically, there must be mass inside, i.e., every black hole has a mass that can somehow be measured, e.g., by orbital velocities of satellites. And the mass-energy has to equal the mass-energy that has fallen in. So far so good. But the stuff that falls in is not purely described by its mass. It also has angular momentum, electrical charge, maybe a few other quantities such as charm and strangeness (speculating here). So the black hole must have a net angular momentum, electrical charge, charm, and strangeness. Electrical charge could be measured by holding an electrometer next to the black hole. And so forth. So far I've described 5 quantities that "describe" a black hole. So my question is: How many more are there? What's the total number of numbers that accompany a particle as it gets sucked in? Suppose it's a small number, like 11. Does that place an upper limit on the information content of a black hole, and hence the possibility of describing a "civilization" inside it?

jepler 9y ago
It sounds like your line of thinking leads to the https://en.wikipedia.org/wiki/Black_hole_information_paradox https://en.wikipedia.org/wiki/Black_hole_information_paradox
alde 9y ago
You have almost formulated the no-hair theorem. https://en.wikipedia.org/wiki/No-hair_theorem https://en.wikipedia.org/wiki/No-hair_theorem
- andrewflnr 9y ago
  I never thought of that in the context of strangeness, lepton number, and other conserved quantities. I don't think strangeness is really measurable (and I don't remember if it's technically conserved), but black holes should probably preserve lepton number somehow. Is that a quantum gravity sort of problem?
  - IntronExon 9y ago
    It might be, in that a Q-ball or something similar could there instead of a singularity, or it could be that there is no interior. Remember that the Holographic Principle implies that the total entropy of the volume of the hole can be encoded in the 2D event horizon of the hole. The singularity is a prediction of GTR, but GTR breaks down there too. This is why black holes are so exciting in the context of new theories which are complementary to GTR!

dustingetz 9y ago

Between reality and maths, the maths are the more fundamental thing that is used to explain reality. What you call reality is just some circumstances that your brain got used to.

visarga 9y ago
On the contrary, maths are just approximations of reality, not something fundamental to it.
- pbhjpbhj 9y ago
  I think the jury is still out on mathematical realism. Our current physics is almost certainly an imperfect description/model however.
  - visarga 9y ago
    Even if we'd know the perfect model for particle physics, we still can't apply math straight for simulation. We always prefer an approximation, all real world models are approximations.

make3 9y ago

not an physicist, but from the point of view of the thing going on the black whole, time still goes on smoothly. My understanding is that the inside of the black whole becomes like a new universe, effectively cut from the previous one from the perspective of causality

v_lisivka 9y ago

But black hole has center, where gravity forces from shell negates each other, which has zero gravity, thus normal speed.

brianberns 9y ago

Our own past (say, 1974, for example) is also “separated from us not by a space-like frontier, but a time-like one“. Would you say that the past is not real?

grondilu 9y ago
The frontier I was talking about is impassable. It's "infinitely in the future", aka "never". That's a whole different level of frontier, imho. Granted, there is a bit of tree falling[1] conundrum here, but that does not make the question less interesting (arguably, it even makes it all the more so). 1. https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest

hinkley 9y ago

I’ve wondered this too but I just had a thought. I ended up asking myself why any black hole is ever bigger than critical mass if this is true. Take a black hole that’s been slurping matter in and it’s all at the event horizon because as you say, it takes forever to cross. But as that mass builds and builds doesn’t the event horizon move? Take the scene to the limit. Say a black hole never absorbs anything. The amount of mass parked just above the horizon becomes so great that another black hole forms. Now you have two overlapping horizons, which can’t stay that way. What really happens is that the density of mass inside the radius near the black hole is sufficient to be a black hole of a larger diameter and then it just... is. I think that what this means is that you never get to the event horizon, but the horizon comes to you.

computerex 9y ago
There is so much speculation and misinformation here. One key idea of relativity is that laws of physics remain the same for all uniformly moving reference frames. Objects approaching and entering the event horizon experience time normally. For large black holes, a probe entering past the event horizon will continue to fall towards the singularity and experience time normally for a long time before being destroyed. To external observers, of course nothing can be observed as falling through the event horizon because not even light can escape past the event horizon. So no light from beyond the horizon of the probe can ever reach the observers. But that doesn't mean things can't go past the EH normally, or that here is some other magic happening like > I think that what this means is that you never get to the event horizon, but the horizon comes to you. A black hole is just another object with a very very powerful gravitational field.
- hinkley 9y ago
  GP was talking about the passage of time from the standpoint of the external observer. About time dialation, not about the singularity. Near the horizon a heartbeat takes eons from the perspective of someone watching you fly into the black hole. Assuming of course that you haven’t already been torn to shreds by the high energy particles and gamma rays traveling perpendicular to your path...

gooseyard 9y ago

If you've not come across Lee Smolin's (speculative) writing on the Fecund Universes theory, you'll probably also love it. Don't have any links as I've only read about it in one of his books, but it's a fascinating idea.

teh_klev 9y ago

These videos are excellent, thanks for the link. Just spent the last hour or so having my mind blown over and over :) I also really need one of these: https://store.dftba.com/collections/all/products/heat-death-shirt https://store.dftba.com/collections/all/products/heat-death-...

mdpopescu 9y ago

> Events behind the event horizon are postponed to "the end of times". Thank you. To me, this has been obvious since I learned about the time slowing required by GR. Since then, I was unable to understand why people are talking about things "falling into" black holes. (There's an episode of SG-1 where a team is trapped by a black hole, and times keep slowing, but they never realize that this means that team WILL NEVER DIE.)