I I don't see how a black hole's event horizon can be crossed

[Foretranimal]

TL;DR Summary

Is it possible that Eienstien's equivalence principle does not apply to the perspective of someone falling through the event horizon of a black hole, because that perspective does not and cannot exist?

OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox.

If black holes "evaporate" via Hawking radiation, then they cannot exist forever.

So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon.

Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon?

The thing I have always read is that when the in-faller crosses, they feel nothing special. But this paradox seems to assume the crossing happens. If the crossing never happens, is there an information paradox at all?

If it takes forever to cross the event horizon, and a black hole's existence is less than forever, would the black hole evaporate before that unfortunate person crosses the horizon?

It seems more like the event horizon has no "there" or "inside" the event horizon - the horizon is an asymptotic limit of what exists. There is no inside, like there is no "before" the Big Bang. If you remove the assumption, there was a crossing, is there still a paradox?

I have no expertise in this area, so there may well be something basic I am just missing.

 

[PeterDonis]

there may well be something basic I am just missing.

There is. First, read this Insights article:

https://www.physicsforums.com/insights/black-holes-really-exist/

 

[Dale]

If black holes "evaporate" via Hawking radiation, then they cannot exist forever.

So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon.

The standard Schwarzschild coordinates that you refer to in the second statement are on a different manifold than the Hawking spacetime for the first statement.

Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon?

The equivalence principle does not say your perspective is valid. The principle of general covariance says your “perspective” is valid, where your “perspective” is any coordinate chart you choose. If you choose to use a chart that doesn’t include the horizon then your “perspective” cannot make any claims, positive or negative, about what crosses the horizon.

If it takes forever to cross the event horizon, and a black hole's existence is less than forever,

There is, to my knowledge, no coordinate chart on any spacetime where both statements are true.

 

[PeterDonis]

If black holes "evaporate" via Hawking radiation, then they cannot exist forever.

True. But they can exist for a very, very, very, very, very long time. For example, the expected evaporation time by Hawking radiation for a 10 solar mass black hole is about $10^{70}$ years.

from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon.

Not if the hole evaporates. An evaporating hole is different from an "eternal" hole, which is where the "slow down, freeze, and redshift to nothing" description comes from.

If the hole evaporates, you see the person cross the horizon at the same time as you see the final evaporation of the hole.

Does the equivalence principle say my perspective is valid?

The equivalence principle has nothing to do with your scenario. The equivalence principle is local. What a distant observer sees when a person falls into a black hole and the hole later evaporates is not local.

is it possible that that person really never crossed the event horizon?

No.

The thing I have always read is that when the in-faller crosses, they feel nothing special.

That's true.

If it takes forever to cross the event horizon

It doesn't. The person falling in only experiences a finite amount of time by their clock before they cross the horizon.

It takes a longer and longer time for the distant observer to see the person getting closer and closer to the horizon. But that's because the light takes longer and longer to get out to the distant observer. It has nothing to do with what's happening to the person close to the horizon.

would the black hole evaporate before that unfortunate person crosses the horizon?

No.

It seems more like the event horizon has no "there" or "inside" the event horizon

This is not correct. There is a region of spacetime inside the horizon. This is true even for an evaporating black hole.

the horizon is an asymptotic limit of what exists.

Wrong.

There is no inside, like there is no "before" the Big Bang.

Wrong.

If you remove the assumption, there was a crossing

You can't, because that would be wrong. See above.

We've had a number of previous threads on this general topic, and the confusion you have is a common one. But it's still a confusion that you need to unlearn.

 

[Nugatory]

Does the equivalence principle say my perspective is valid?

The equivalence principle says that sitting in a box at rest on the surface of a gravitating body (for example, in a closed room on the surface of the rest) is indistinguishable from sitting in a box that is being accelerated in empty space - Google for "Einstein's elevator" for more.

And of course this is completely different and has nothing to do with has nothing to do with watching something falling into a black hole.
The "it takes forever to reach the event horizon" thing is a misleading description of what's going on. If we start a stopwatch at zero and drop it into a black hole, it will fall through the event horizon and it will read some finite value when it does - so clearly the horizon is crossed in finite time. However, the light from that crossing event will never reach us on the outside, so if we choose to define when something happens as "when light from it reaches our eyes, minus the time it took for light to get from there to our eyes" we will conclude that it never happened.

 

[Foretranimal]

There is. First, read this Insights article:

https://www.physicsforums.com/insights/black-holes-really-exist/

Thanks!
This is going to take some time, and likely re-reads, but it is spot on the question.

 

[DaveC426913]

This, in a nutshell, is usually the key that unlocks the solution to the apparent paradox, IMO:

It takes a longer and longer time for the distant observer to see the person getting closer and closer to the horizon. But that's because the light takes longer and longer to get out to the distant observer. It has nothing to do with what's happening to the person close to the horizon.

 

[Foretranimal]

There is. First, read this Insights article:

https://www.physicsforums.com/insights/black-holes-really-exist/

This one is difficult to get:

"But it turns out that there is an additional wrinkle here: there is more than one possible “infinity” in an asymptotically flat spacetime. There are five; they are called future and past timelike infinity, future and past null infinity, and spacelike infinity. Why is this? Because spacetime includes time as well as space, so there are three kinds of curves, timelike, null, and spacelike, and the first two kinds have two different directions, future, and past. (Technically speaking, the light cone at every event in spacetime has two interior regions–future and past–which are disconnected, but only one exterior region–the spacelike region.) Each of these, if extended indefinitely, ends up at a different “infinity”."

Is this related to the idea that inside the event horizon, time becomes spacelike and space becomes timelike? I have read that, but don't understand.

Source: https://www.physicsforums.com/insights/black-holes-really-exist/

 

[Foretranimal]

The "it takes forever to reach the event horizon" thing is a misleading description of what's going on. If we start a stopwatch at zero and drop it into a black hole, it will fall through the event horizon and it will read some finite value when it does

OK, but if we drop that stopwatch and don't jump in with it, doesn't that stopwatch experience a different now from the dropper's now, as it approaches the horizon? To me, it seems like that now, when the stopwatch has that finite value, isn't my now.

 

[Foretranimal]

True. But they can exist for a very, very, very, very, very long time. For example, the expected evaporation time by Hawking radiation for a 10 solar mass black hole is about years.

Even a very, very, very, very, very long time is less than infinite time. I think even a very, very, very, very, very, very, very, very, very, very long time is still less, yes?

If the hole evaporates, you see the person cross the horizon at the same time as you see the final evaporation of the hole.

For supermassive black holes, it is even mind-bendingly longer - like the last thing that can happen that has any causal relevance to anything.

Given that we are in the realm of exponential exponents, which might also be exponents. I want to know why this matters - even if it is in a simplified way.

 

[Foretranimal]

Google for "Einstein's elevator" for more.

I think I get Einstein's happiest thought: freefall in a gravitational well is indistinguishable from rest - not only are they indistinguishable, they are the same thing.

Is that right?

 

[Foretranimal]

The standard Schwarzschild coordinates that you refer to in the second statement are on a different manifold than the Hawking spacetime for the first statement.

Thank you for the response. I don't understand what a manifold is in your context. With internal combustion engines, manifolds generally serve to either merge or split air or water flows. I have read about manifolds with respect to theoretical physics - and I have no idea what that means... :)

 

[Foretranimal]

The equivalence principle does not say your perspective is valid. The principle of general covariance says your “perspective” is valid, where your “perspective” is any coordinate chart you choose. If you choose to use a chart that doesn’t include the horizon then your “perspective” cannot make any claims, positive or negative, about what crosses the horizon.

Valid is the wrong word. Let me amend that to say both perspectives are real and exist.

We have a 20-foot barn, with doors fore and aft. I have a stationary watch standard on the roof with a switch where she can instantaneously open or close the magical barn doors at the same time. We also have a stupid fast ladder-bearer with a 25-foot ladder carrier, who I am granting the ability to arbitrarily accelerate and travel at any allowed/possible speed (less than c). My super-fast-laderman is named Ernest, and the switchmaster is named Jenefer.

If Ernest stops being lazy, he can accelerate as close as he needs to with my ladder, and if he travels fast enough, distance dilation will shrink his ladder to less than the 20 feet between doors (Jenefer's perspective), and that shrinkage shrinks the length of the ladder, allowing it to pass through this impossibly long barn.

From Ernest's perspective, the nearest door opens 1st, and as he is running through the barn, he sees the exit open while the entrance is still open.

Jenefer sees a compressed ladder, and the doors open/close at the same time. Ernest sees all the ladder's length, but sees the door open and close at different times.

My understanding of this is that they do not share the same now, because Jill has so much movement in space, she has less movement in time, with respect to Ernest.

because there isn't a universal now. The only law is causality: this caused that. When this or that happened is a matter of the reference frame.

This is how I try to visualize it. I am open to better understanding.

The point I'm trying to underscore is that my understanding is that there are no universal "now" with respect to reference frames.

 

[PeterDonis]

Is this related to the idea that inside the event horizon, time becomes spacelike and space becomes timelike?

No. The five infinities I mentioned in the article aren't important for what we're discussing here. They're a more technical point that comes into play when you want to make rigorous definitions of terms like "black hole" and "event horizon". But I don't think we need that level of rigor here.

I have read that, but don't understand.

The "time becomes spacelike and space becomes timelike" is a pop science description of a feature of a particular coordinate chart, Schwarzschild coordinates. It has nothing to do with the actual physics.

 

[PeterDonis]

Even a very, very, very, very, very long time is less than infinite time.

That's true, and that's why I said that an evaporating black hole, which only lasts for a very, very, very, very, very long time, is different from an idealized "eternal" black hole that lasts for an infinite time.

I want to know why this matters

You stated it yourself, in what I quoted at the top of this post.

 

[PeterDonis]

a different now

"Now" is not a physical thing in relativity. It's a convention. Trying to think in terms of "now" will only get you very confused, particularly in a scenario like this.

 

[PeterDonis]

My understanding of this is that they do not charge the same now

If you mean that relativity of simultaneity is involved in the "barn and ladder" scenario, yes, that's true.

But relativity of simultaneity is not involved in what we're discussing in this thread.

 

[Foretranimal]

If you mean that relativity of simultaneity is involved in the "barn and ladder" scenario, yes, that's true.

But relativity of simultaneity is not involved in what we're discussing in this thread.

OK, and I don't doubt you. But I'm not trying to be right, I'm trying to get a better understanding of this.

It may be wrong, but the parallel I am seeing is that the now of viewing the infalling person is not the same now of the external observer.

 

[Dale]

Valid is the wrong word. Let me amend that to say both perspectives are real and exist.

Valid is a fine word. If you want to go beyond valid then a more clear description is that the principle of general covariance says that all “perspectives” agree on the laws of physics and the result of applying them to any given experiment.

my understanding is that there are no universal "now" with respect to reference frames.

I agree. There is no universal “now”. Causality is universal.

I don't understand what a manifold is in your context

A manifold is the mathematical representation of the geometry of spacetime. It has distances and times and angles and speeds, but coordinates are optional

The point I was making regarding manifolds is that there is not even theoretically any spacetime where both the conflicting claims you mention hold. It is not a real conflict because they are two different t spacetimes. In particular, in a spacetime with an evaporating black hole things don’t take forever to fall in.

 

[Foretranimal]

But relativity of simultaneity is not involved in what we're discussing in this thread.

It may well be that I have faulty reasoning, and I have no idea. I'm trying to figure out why.

Why do I think there is a relationship between simultaneity and the crossing of the event horizon? Back to the ladder experiment: Ernest and Jenefer experienced the exact same event. Jill sees length dilation, and Ernest disagrees about the order of events. Both perspectives are real.

 

[Foretranimal]

A manifold is the mathematical representation of the geometry of spacetime. It has distances and times and angles and speeds, but coordinates are optional

Is that related to how, within a past/future spacetime diagram, you can take any perspective in the light cone and, with a geometric transformation - skew the diagram - and get the equivalent spacetime diagram with respect to any other perspective?

My mathematical background only went up to basic calculus, and I know there is much more. I'm trying to build on that.

 

[Dale]

Is that related to how, within a past/future spacetime diagram, you can take any perspective in the light cone and, with a geometric transformation - skew the diagram - and get the equivalent spacetime diagram with respect to any other perspective?

My mathematical background only went up to basic calculus, and I know there is much more. I'm trying to build on that.

Yes. Coordinates are optionally added to a manifold, but only in a manner in which all coordinates can be used to write the laws of physics and predict the outcome of experiments.

 

[PeterDonis]

It may be wrong, but the parallel I am seeing is that the now of viewing the infalling person is not the same now of the external observer.

There is no such thing as "the" now of any observer.

Why do I think there is a relationship between simultaneity and the crossing of the event horizon? Back to the ladder experiment

I.e., for a wrong reason. The barn and ladder scenario has nothing to do with the scenario we're discussing here. You should not even be trying to draw any analogies between them.

 

[Foretranimal]

The point I was making regarding manifolds is that there is not even theoretically any spacetime where both the conflicting claims you mention hold. It is not a real conflict because they are two different t spacetimes. In particular, in a spacetime with an evaporating black hole things don’t take forever to fall in.

Heh...
I may have made conflicting claims. But honestly, I did not mean to make a claim. My understanding of spacetime and blackholes are is limited. That's why I felt compelled to find some way to ask about these concepts in a place where I might get answers from people who know.

 

[PeterDonis]

I'll comment separately on misconceptions about the "barn and ladder" scenario, but really it's off topic for this thread and discussion of it should be in a separate thread.

Ernest and Jenefer experienced the exact same event.

There are multiple events in the scenario. An "event" is a particular point in spacetime. For example, "the front door of the barn opens" is an event. So is "the front end of the ladder passes the front doorway of the barn". But the whole scenario is not an "event"; it's multiple events with particular spacetime relationships.

Jill sees length dilation, and Ernest disagrees about the order of events. Both perspectives are real.

What you are calling a "perspective" is properly called a choice of coordinates. And the key thing to understand about choices of coordinates is that they aren't real things. They're human conventions to make it easier for us to do calculations. They're not part of the actual physics.

The actual physics of the scenario is the things that both observers agree on, i.e., the things that are independent of any "perspective" (choice of coordinates):

The front door of the barn opens before the front end of the ladder enters the front doorway of the barn.

The rear door of the barn opens before the front end of the ladder exits the rear doorway of the barn.

The front door of the barn closes after the rear end of the ladder enters the front doorway of the barn.

The rear door of the barn closes after the rear end of the ladder exits the rear doorway of the barn.

The time ordering of the four events according to different coordinate charts can be different because some of the events are spacelike separated. But nobody actually experiences events happening in a different order. It's just that their abstract calculation of the "times" of events that are separated from each other give different answers. But there is no physics corresponding to that. It's just an abstract calculation.

 

[PeterDonis]

It may well be that I have faulty reasoning, and I have no idea. I'm trying to figure out why.

Because you're starting from premises that have nothing to do with the black hole scenario.

You need to start fresh, from premises that apply to the black hole scenario. Your background might not be enough to even know what those are. But that means you shouldn't even be trying to formulate questions about what you think happens, because you don't know enough yet to be able to predict what should happen. You should be asking what the correct premises are to start reasoning from.

 

[Foretranimal]

You should not even be trying to draw any analogies between them.

I respectfully disagree: There is intrinsic value in looking at a flawed analogy for the purpose of figuring out why the analogy is flawed, provided you are open to corrected understanding.

 

[PeroK]

Heh...
I may have made conflicting claims. But honestly, I did not mean to make a claim. My understanding of spacetime and blackholes are is limited. That's why I felt compelled to find some way to ask about these concepts in a place where I might get answers from people who know.

When I was learning relativity I realised that all this about "perspectives" and "observers disagreeing" was unnecessary and leading the student (me) in the wrong direction. I realised that in physics there are coordinate systems, events and measurements, and I focused on that.

If you focus on events and coordinates, something like the barn and pole paradox just isn't a paradox at all.

My advice is: there is no such thing as a "perspective" in physics. You can analyse a physical scenario using any coordinate system; and, an observer can make a local observation, by measuring something locally. Note that an observer cannot make a direct measurement anywhere other than where they are. They can, however, infer that an event took place at a different place and time, based on their local measurements.

Note that in relativity it's possible to have events that cannot be observed by all observers. These events happen, in the sense that they are in the global model. And any observer can give them coordinates in an appropriate coordinate system. But, some observers can never make a local measurement that is a direct observation of that event.

In other words, it's nice if light from an event eventually reaches you. But, if it can't ever reach you, that does not mean that the event does not take place.

 

[Foretranimal]

Because you're starting from premises that have nothing to dowith the black hole scenario.

Awesome - thank you. Please tell me how my premises are flawed, so I might learn.

Your background might not be enough to even know what those are

OK, I believe you. What are my specific background limitations you are referring to?

I'm asking so I might know where I can improve them.

But that means you shouldn't even be trying to formulate questions about what you think happens.

I should not ask questions I don't already have a specific background to ponder and ask?

Why? Are you saying I should just stop thinking about this because I am not an expert?

Is there an inherent wrongness in asking questions that push the limit of your understanding?

Should I stop asking curious questions?

I'm asking so I might know where I can improve.

because you don't know enough yet to be able to predict what should happen.

No, I am not predicting anything, I don't have the background to make predictions - that is exactly why I am asking. I'm not asserting anything; I am asking.

You should be asking what the correct premises are to start reasoning from

OK, if it wasn't clear: I am asking for exactly that. Thanks in advance if you would like to offer guidance.

 

[Foretranimal]

When I was learning relativity I realised that all this about "perspectives" and "observers disagreeing" was unnecessary and leading the student (me) in the wrong direction. I realised that in physics there are coordinate systems, events and measurements, and I focused on that.

When I say disagree, I am only referring to observations made in different referance frames. I do not see a paradox in the differeing perspective of simultaniously, and non-simultaniously in there is no universal now.

As I understand it, the only differation of simultaniously/non-simultaniously is causality, becasue there is no now.

My advice is: there is no such thing as a "perspective" in physics. You can analyse a physical scenario using any coordinate system; and, an observer can make a local observation, by measuring something locally. Note that an observer cannot make a direct measurement anywhere other than where they are. They can, however, infer that an event took place at a different place and time, based on their local measurements.

I respectfully dissagree: while it may be apocriphal, The story of Eienstien's childhood facination was trying to picture what a light wave looked like if you traveled alongside at it's speed. Would you see a standing wave?

We know now the question is an impossility - but understanding what a faulty idea is faulty, can be a path to learning.

Note that in relativity it's possible to have events that cannot be observed by all observers. These events happen, in the sense that they are in the global model. And any observer can give them coordinates in an appropriate coordinate system. But, some observers can never make a local measurement that is a direct observation of that event.

Honestly, that seems intuitve to me, too. But there is no way to demonstrate any existance outside your personal light cone experience. How can we know for sure there is anyting real there?

Is that unobsevable place there for you and me when we can never affect it?

 

[PeroK]

What you see as a "path to learning" looks like a confusion of ideas to me. That said, you have to choose your own path. Where that path leads is another matter.

 

[Ibix]

This thread has moved quite fast and I've not fully caught up, so apologies if this repeats things already said.

There are different models of black holes, and those models have different properties. The comment about watching an infalling object slow down, freeze, and redshift to "nothing," but never cross the event horizon in the OP is a statement about an eternal black hole - a model that does not include Hawking radiation. It isn't true about a model that does include black hole evaporation. It's also a statement of what an observer outside the hole directly sees - not a statement about what that observer can infer from what they see. That last bit often gets confused, because with an eternal black hole it's easy to construct coordinate systems that don't assign time coordinates at or below the horizon and then take them too literally.

With evaporating black holes you do see the horizon crossing at the same time as you see the hole explode (at least in principle - actually picking it out of the mess might be difficult). So there's no "it didn't form but now it's exploded" paradox. The mistake is mixing true statements about eternal black holes with wondering about non-eternal holes.

To be fair, physicists will often make statements about "black holes" without specifying which models they're thinking of. It's a continuing problem with science communication that general statements are always false, but precise ones are often too nitpicky (about nits the public doesn't even know need to be picked) and turn off the public.

 

[Foretranimal]

What you see as a "path to learning" looks like a confusion of ideas to me. That said, you have to choose your own path. Where that path leads is another matter.

I'm here to be wrong and corrected, and offer my thanks in advance.

Yes, I do have a confusion of ideas: when I think about this topic, there are ideas I have that don't make sense to me. I love to be wrong, and I want to have some degree of understanding where and how I am wrong. I'm sorry if I presented anything as if I knew anything - I don't. I want to understand where my mistakes are and learn.

Usually, when I hit one of these perceived paradoxes, I want to understand to some degree what I missed. My background IS going to limit what I am able to understand to the degree of an expert - I am not an expert on this topic, I am just really curious.

That said, I do not do too badly with partially getting an answer when someone explains something. I may not get it at first. I may never get it in part. I may never get it at all.

But my warm thanks to everyone responding to me, and for taking the time to engage with this question.

I registered on this site earlier today - because this has been driving me nuts, and there is just NO substitute for back-and-forth communication when you have a question.

 

[Dale]

I may have made conflicting claims. But honestly, I did not mean to make a claim.

By conflicting claims I am talking about your OP.

If black holes "evaporate" via Hawking radiation, then they cannot exist forever.

So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon.

These are indeed genuinely conflicting claims. But the thing is that they are not merely different “perspectives” (coordinate charts). They are different spacetimes (manifolds). In a spacetime where one statement holds, the other does not.

But this paradox seems to assume the crossing happens. If the crossing never happens, is there an information paradox at all?
…
It seems more like the event horizon has no "there" or "inside" the event horizon - the horizon is an asymptotic limit of what exists. There is no inside, like there is no "before" the Big Bang. If you remove the assumption, there was a crossing, is there still a paradox?

Here is the problem. What you have found are genuinely conflicting statements, but not a paradox. And no discarding of assumptions is warranted by the conflict.

What you have found is like this: Suppose a theory produces the equation $$(x-3)(x+4)=0$$ One scientist decides to write a book to make as much money as possible, so he decides to talk about this equation, but only using words and not math. He talks about the positive root and says “it is odd”.

Another scientist sees all the money he makes and decides that she wants some too. She wants her book to be different so she writes about the negative root and says “it is even”.

While “it is odd” and “it is even” are genuinely conflicting claims, there is no paradox because each statement is referring to a different “it”.

The resolution is not to suppose that maybe we shouldn’t assume there are any even numbers. The resolution is to recognize that two different solutions are being discussed.

 

[Grinkle]

I respectfully dissagree

One "B" level poster to another ....

What I read from @PeroK is not that using the word 'perspective' is objectively wrong, rather that 'perspective' not a concept that physicists would directly wrap math around to map 'experience' (another fuzzy word I'm using here, I acknowledge) from one reference frame to another; if you invest some time into what are meant by co-ordinates, events and measurements and consider how different combinations of these more fundamental elements combine to form what you are calling a perspective, that will help you mature your intuition along the lines of your questions in this thread.

 

[PeroK]

One "B" level poster to another ....

What I read from @PeroK is not that using the word 'perspective' is objectively wrong, rather that 'perspective' not a concept that physicists would directly wrap math around to map 'experience' (another fuzzy word I'm using here, I acknowledge) from one reference frame to another; if you invest some time into what are meant by co-ordinates, events and measurements and consider how different combinations of these more fundamental elements combine to form what you are calling a perspective, that will help you mature your intuition along the lines of your questions in this thread.

Yes, that's an excellent summary.

There is a further point that an observer is not obliged to anayse things using any particular reference frame. An observer on the ground, trying to calculate what happens on a moving train or aeroplane can choose to use a reference frame in which the train or plane is at rest. The observer does not actually have to board the train or aircraft in order to use that reference frame!

The observer is restricted in the direct measurements they can make; but, not they are not restricted in terms of the reference frame or coordinate system they can choose to use to analyse the problem.

And, in fact, in many problems (whether relativistic or non-relativistic), switching to and from different reference frames is an important technique. Another example is using the zero-momentum reference frame to analyse a collision (whether relativistic or not).

 

[PeterDonis]

There is intrinsic value in looking at a flawed analogy for the purpose of figuring out why the analogy is flawed

Not if the answer is "it's not even wrong". Your analogy is too far off to even be corrected. You're better off just throwing it away and starting from scratch.

Please tell me how my premises are flawed

I can't; as above, they're too far off to even be corrected. You're simply using the wrong tools for the problem. If you're trying to drive screws with a hammer, and someone tells you that's wrong, it's no good asking them how you can correct your use of the hammer so it'll work. You need to drop the hammer and get a screwdriver.

What are my specific background limitations you are referring to?

Um, the fact that you admit you have no expertise in this area?

I'm asking so I might know where I can improve them.

By taking the time to learn what GR actually says about black holes and evaporating black holes, from a textbook. That will mean taking some time to learn GR in general. From what I can see, you need quite a bit of background knowledge about GR before you can properly approach this problem, or even understand the proper approach. That's getting beyond what we are likely able to do for you in the context of a PF thread.

I should not ask questions I don't already have a specific background to ponder and ask?

Not questions based on anything you think you know about this problem now, no. As far as I can tell, everything you think you know about this problem is wrong, so it will do you no good to use that knowledge to formulate questions.

Are you saying I should just stop thinking about this because I am not an expert?

No, I'm saying that I think you are drastically underestimating the amount you need to learn--and unlearn--to properly understand the scenario you're asking about. I don't think it's a matter of tweaking one or two premises in your understanding. I think it's a matter of throwing away everything you think you know and starting fresh.

I am not predicting anything

Yes, you are:

from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon.

That's a prediction--a wrong one. It's something you think you know, that's simply wrong, that you need to unlearn.

I am only referring to observations made in different referance frames.

There's no such thing. Observations aren't made "in" a particular reference frame. Observations are concrete, invariant facts that every reference frame has to agree on. For example, in your "barn and ladder" scenario, every reference frame has to agree on the four observations I listed in post #25.

This is another example of where I don't think it's a matter of just tweaking a few of your premises. As far as I can tell, your entire understanding of how special relativity work (never mind general relativity) is wrong and you should throw it away and start fresh.

 

[Dale]

I am not so pessimistic about @Foretranimal because of their openness here. There is quite a bit to do, but they do not seem resistant to learning. I think that willingness to learn is probably more important than having mostly correct concepts to begin with.

 

[PeterDonis]

But there is no way to demonstrate any existance outside your personal light cone experience. How can we know for sure there is anyting real there?

This is a question of philosophy, not physics. In physics, we build models and use them to make predictions. Sometimes the predictions are of things that we can't directly observe even in principle, such as the predictions about falling into a black hole. But the models and the predictions they make are still perfectly well-defined, and when physicists talk about what happens to someone who falls into a black hole, that's what they're talking about. The underlying theory on which the black hole models are based, General Relativity, is extremely well confirmed everywhere we've tested it, so physicists feel pretty confident about trusting its predictions in regimes like black holes.

(There is a caveat to this, that physicists do consider alternate models, of things that look like black holes from the outside for a very long time, but don't have any actual event horizons or singularities. If you search PF for "Bardeen black hole", you'll find some threads about one such alternate model. Nobody knows for sure which, if any, of the models we currently have, in a regime like this where we have no direct tests, will end up being the right one, the one that actually occurs in our actual universe. But the key point is that, in order to discuss a scenario at all in terms of "what happens", you have to pick one specific model to use in order to predict what happens. You can't mix them.)

In the OP of this thread, as has already been pointed out, you mixed up two different models: the model of a black hole that evaporates, and the model of an idealized "eternal" black hole that lasts for an infinite time. These are two different models, and it makes no sense to mix up predictions from one with predictions from the other.

Is that unobsevable place there for you and me when we can never affect it?

You can affect the black hole; you can drop things into it. Things at or inside the horizon can't affect you (because they can't send light signals to you).

 

[PeterDonis]

I think that willingness to learn is probably more important than having mostly correct concepts to begin with.

I agree with this, but I think one also has to be realistic about just how much one has to learn--and unlearn.

 

[PeterDonis]

I am asking for exactly that.

The correct premises are the black hole models that have been built using GR. Understanding them requires taking some time to learn them, which, as I've already pointed out, means learning the underlying framework of GR that they're built from. (And, as I've also pointed out, you might need to learn SR properly first.)

For a good introduction to SR and GR, you could try Carroll's online lecture notes:

https://arxiv.org/abs/gr-qc/9712019

They discuss black holes (but not, IIRC, evaporating ones, only "eternal" ones) in one of the later chapters.

The key differences between the "eternal" black hole model and the evaporating black hole model (or at least the basic evaporating black hole model that Hawking originally used--there's been a lot of more advanced work in this area since) have been described earlier in this thread.

 

[DaveC426913]

This is worth repeating, I think, so as not to discourage the OP:

That's getting beyond what we are likely able to do for you in the context of a PF thread.

He may not be getting he answers he asks for, but it's not because people aren't bothering, it's because a forum thread is not the best place to teach the required physics and maths.

 

[sbrothy]

This is worth repeating, I think, so as not to discourage the OP:

He may not be getting he answers he asks for, but it's not because people aren't bothering, it's because a forum thread is not the best place to teach the required physics and maths.

In effect, he has to use a different set of coordinates for his choice of media.