B Are Black Holes Actually Giant Neutron Stars Cloaked in an Event Horizon?

[Jason R Carrico]

I was just wondering if there is anything to suggest that black holes are anything but giant neutron stars cloaked in an event horizon created by their own gravity. I mean if a neutron star is just on the cusp of having enough mass to be a black hole, and then gains that mass, what's to say it doesn't just gain an event horizon at that point? Or is there a huge explosion and burst of energy as the star collapses into a black hole?

 

[Drakkith]

Hmm... This paper may be of interest to you: https://arxiv.org/pdf/1307.3995.pdf

On the Maximum Mass of Neutron Stars
One of the most intringuing questions about neutron stars concerns their maximum mass. The answer is intimately related to the properties of matter at densities far beyond that found in heavy atomic nuclei. The current view on the internal constitution of neutron stars and on their maximum mass, both from theoretical and observational studies, are briefly reviewed.

 

[JLowe]

I have trouble believing there is an actual singularity inside the horizon, and much less trouble believing there is an object of some finite maximum density in its place. Perhaps one of the exotic star candidates, or even the relatively new Plank Star theory.

 

[newjerseyrunner]

I have trouble believing there is an actual singularity inside the horizon, and much less trouble believing there is an object of some finite maximum density in its place. Perhaps one of the exotic star candidates, or even the relatively new Plank Star theory.

I don't think anyone believes that there is an actual singularity. Singularities tend to not be physical things, but simply holes in mathematics.

 

[JLowe]

I don't think anyone believes that there is an actual singularity. Singularities tend to not be physical things, but simply holes in mathematics.

Yes and that means if neutron stars have a maximum mass, and that mass doesn't create a horizon, then some further compressed state of matter must exist, but while we've evidence for thousands of neutron stars, we haven't seen any conclusive evidence of "quark stars" or other exotic stars. Which could potentially mean such stars have horizons.

 

[Jason R Carrico]

A compact star with a horizon appears to me to be the most logical answer for what's inside a black hole. Just a ball of disassociated fundamental particles behaving the way models describe the core of a neutron star.

 

[Ken G]

It's funny how people kind of pick and choose the singularities they are comfortable with. There are certainly plenty of GR theorists of note, such as Kip Thorne, who do take the predictions of GR seriously enough to think there really is a singularity in there. The story goes that what we regard from our external perspective as radius is converted by the extreme curvature into what is locally regarded as time, so then anything that experiences a forward march of time must reach the central singularity (or the ring singularity). In that picture, to say that some kind of exotic matter could resist gravity would be like asserting that it could stop time. Of course we don't really know what happens in there, but people like Kip Thorne do think it's a singularity.

What's more, the acceptance of singularities is not as rare as you might think-- people seem content with certain types of singularities. For example, many QED theorists are content to imagine that the electron really is a point particle, not just that it is small. Even more common is the idea that photons really have zero rest mass, which is also a type of singularity because then they have no rest frame. So we should at least be consistent-- we should reject all singularities of any stripe, or we should accept that any theory that works which includes singularities raises the possibility of real singularities. The hybrid approach where people pick and choose out of personal taste seems a bit disingenuous to me.

 

[JLowe]

It's funny how people kind of pick and choose the singularities they are comfortable with. There are certainly plenty of GR theorists of note, such as Kip Thorne, who do take the predictions of GR seriously enough to think there really is a singularity in there. The story goes that what we regard from our external perspective as radius is converted by the extreme curvature into what is locally regarded as time, so then anything that experiences a forward march of time must reach the central singularity (or the ring singularity). In that picture, to say that some kind of exotic matter could resist gravity would be like asserting that it could stop time. Of course we don't really know what happens in there, but people like Kip Thorne do think it's a singularity.

What's more, the acceptance of singularities is not as rare as you might think-- people seem content with certain types of singularities. For example, many QED theorists are content to imagine that the electron really is a point particle, not just that it is small. Even more common is the idea that photons really have zero rest mass, which is also a type of singularity because then they have no rest frame. So we should at least be consistent-- we should reject all singularities of any stripe, or we should accept that any theory that works which includes singularities raises the possibility of real singularities. The hybrid approach where people pick and choose out of personal taste seems a bit disingenuous to me.

Well Kip Thorne is certainly smarter than me, but I don't see how anyone could be "comfortable" with singularities. They may indeed be real physical objects, but they could just as easily mean our current theories are useless at such extreme scales. And for me, its a lot easier to believe that we don't know what's going on at scales we can't probe, and may never be able to probe.

And anything that goes on inside an event horizon is unobservable to us, and any theory is potentially unfalsifiable. For all we know the "gravitational singularity" could just be Santa Clause shacking up with the tooth fairy. I suppose a singularity behind the horizon would look identical to us as any other object with a horizon, so that in some sense, its valid to call it a real singularity whether it is or isn't.

 

[MichaelMo]

I was just wondering if there is anything to suggest that black holes are anything but giant neutron stars cloaked in an event horizon created by their own gravity. I mean if a neutron star is just on the cusp of having enough mass to be a black hole, and then gains that mass, what's to say it doesn't just gain an event horizon at that point? Or is there a huge explosion and burst of energy as the star collapses into a black hole?

It is generally believed that neutron stars can only reach a certain size before they collapse into a "black hole'. Neutron repulsion studies over the years however might suggest that the size limits that are typically imposed of neutron stars may not be accurate;

https://phys.org/news/2005-12-scientist-neutron-stars-black-holes.html
http://arxiv.org/pdf/nucl-th/0511051

Neutron repulsion observations are further supported by careful studies of the structure of neutrons which suggest that while they have a net zero charge, they have an 'Oreo cookie' type structure with outer and inner negatively charged layers with a positively charged layer sandwiched in between the negatively charged layers. That might explain why neutrons tend to repulse one another.

http://www.eetimes.com/document.asp?doc_id=1167106

Cosmological studies of neutron stars also show that they can be larger than we first believed, and they can produce powerful polar jets that were previous thought to be restricted to black holes:

http://www.eetimes.com/document.asp?doc_id=1167106
http://www.telegraph.co.uk/news/sci...er-detected-is-twice-the-mass-of-the-sun.html

 

[Ken G]

Well Kip Thorne is certainly smarter than me, but I don't see how anyone could be "comfortable" with singularities. They may indeed be real physical objects, but they could just as easily mean our current theories are useless at such extreme scales. And for me, its a lot easier to believe that we don't know what's going on at scales we can't probe, and may never be able to probe.

And anything that goes on inside an event horizon is unobservable to us, and any theory is potentially unfalsifiable. For all we know the "gravitational singularity" could just be Santa Clause shacking up with the tooth fairy. I suppose a singularity behind the horizon would look identical to us as any other object with a horizon, so that in some sense, its valid to call it a real singularity whether it is or isn't.

I think it's fair to say that even Kip Thorne is a bit unclear on what he imagines a "singularity" actually is, but he certainly doesn't view it as just another kind of matter like a quark star. For example, this is the kind of thing he says at http://www.space.com/17086-bizarre-black-holes-kip-thorne-interview.html:

"The matter of which a star is made, the atoms of which a star is made, are destroyed at the center of a black hole, when the black hole is created. The matter is gone, but the mass, in the sense of mass and energy being equivalent, has gone into the warped space-time of the black hole."

But he also says:
"And when you get right to the singularity itself, the laws of physics as we know them break down and the laws of quantum gravity take hold. Since we don't understand those laws very well yet, we can't say what the nature of the very core of the singularity is."

So he seems to feel that "singularity" means that the laws we know break down, but he also thinks it is something that destroys mass as we know it and turns it into curvature. I conclude that he figures the situation is more than just a new law of physics there, but a very different behavior altogether. This probably means he is just as suspicious of the prejudice that singularities can't really exist, as he is of using GR in situations where you really need some kind of new theory.

 

[JLowe]

So he seems to feel that "singularity" means that the laws we know break down, but he also thinks it is something that destroys mass as we know it and turns it into curvature. I conclude that he figures the situation is more than just a new law of physics there, but a very different behavior altogether. This probably means he is just as suspicious of the prejudice that singularities can't really exist, as he is of using GR in situations where you really need some kind of new theory.

I can understand where he's coming from, but my perspective its a bit difficult to imagine a singularity making real physical sense when it arises from a theory almost universally considered to be incomplete. That both GR and QM break down in describing such extreme conditions make me suspicious of the singularity.

But on the other hand, GR and QM make extraordinarily accurate predictions at all other scales to an extent it becomes scary. That they would be so accurate at everything else and so "incomplete" at those scales could certainly mean that perhaps these infinities DO exist, and we simply don't have the tools to describe them in a way we can make sense of, and it could very well be impossible for us to do so. Math describes the real world almost perfectly, and infinities naturally arise from mathematics. Infinite densities could very well be a reality that we simply cannot understand.

At some point, I would suspect infinite something would have to have "existed", so why not infinite anything.

 

[rootone]

... This probably means he is just as suspicious of the prejudice that singularities can't really exist, as he is of using GR in situations where you really need some kind of new theory.

I am suspicious that going North from the Earth's North pole makes no sense,
yet at the equator you can go West or East forever, very suspicious that.
However I do think it is credible idea that what GR describes as a black hole is a form of matter which is unknown to us.

 

[JLowe]

I am suspicious that going North from the Earth's North pole makes no sense,
yet at the equator you can go West or East forever.
Very suspicious that,

Indeed, perhaps we should ourselves of longitude.

 

[Ken G]

Don't confuse coordinate singularities from essential spacetime singularities.

 

[Drakkith]

I am suspicious that going North from the Earth's North pole makes no sense,
yet at the equator you can go West or East forever, very suspicious that.
However I do think it is credible idea that what GR describes as a black hole is a form of matter which is unknown to us.

Don't confuse coordinate singularities from essential spacetime singularities.

Is that what a coordinate singularity is??

 

[Ken G]

Yes, going north from the North pole is the commonly used example of a coordinate singularity. There is nothing physical about it, it is merely a glitch in some particular way addresses are generated. For example, see https://physics.stackexchange.com/q...rdinate-singularity-and-a-physical-singularit. The Schwarzschild metric has a coordinate singularity at the event horizon, and an essential singularity at the center. There is certainly something funky about the event horizon, given the topological difference between the geodesics that cross it and those that don't, so it's not a complete coincidence that the metric in Schwarzschild coordinates puts a coordinate singularity there, but that's a global property-- there's nothing locally singular there, and a free-faller experiences nothing strange there-- unlike at the center.

 

[stefan r]

I was just wondering if there is anything to suggest that black holes are anything but giant neutron stars cloaked in an event horizon created by their own gravity. I mean if a neutron star is just on the cusp of having enough mass to be a black hole, and then gains that mass, what's to say it doesn't just gain an event horizon at that point? Or is there a huge explosion and burst of energy as the star collapses into a black hole?

It is a significant transition. A vessel that can retain water is very different from container that leaks. All outward emitted radiation coming back inward should have a profound effect on the surface. Surface emission also never gets anywhere so the "return" is prompt. That should have the drama of a "huge explosion" but IMO better called "massive implosion".

The location of the surface in nuetron stars and the origin of the particle in both the nuetron stars and black hole have uncertainty. That allows for hawking radiation. But Hawking radiation is very different from surface emission.

 

[Drakkith]

It is a significant transition. A vessel that can retain water is very different from container that leaks. All outward emitted radiation coming back inward should have a profound effect on the surface. Surface emission also never gets anywhere so the "return" is prompt. That should have the drama of a "huge explosion" but IMO better called "massive implosion".

I'm not sure what all this means. Can you elaborate?

 

[stefan r]

I'm not sure what all this means. Can you elaborate?

Suppose we have a "leak proof" container and we put a liter of water in that container. Tomorrow we can measure the volume or mass of water and it will be the same.

If you have a non-expandable and leak proof container and you add water to it the pressure inside the container increases. Also if you heat the water then the pressure increases. People have died from boiler explosions. A boiler with a safety valve has a significantly different danger level than a boiler without a safety valve.

Analogies are weak arguments. This one is pretty bad. A nuetron star can cool off by emission of photons and neutrinos. A black hole can not.

 

[Drakkith]

Sorry stefan, I still have little idea what you're trying to say except that neutron stars can cool off and black holes cannot. But I don't see how that goes back to your previous post. I'd blame myself for not understanding, but it's more fun to blame @phinds.

 

[stefan r]

Sorry stefan, I still have little idea what you're trying to say except that neutron stars can cool off and black holes cannot. But I don't see how that goes back to your previous post. I'd blame myself for not understanding, but it's more fun to blame @phinds.

My ass is interacts on my chair. My chair interacts with my carpet. If I was passing into the event horizon the carpet would not be able to send information to the chair. Thus the chair is not supported on carpet and moves down. Now my ass is unable to comunicate with the seat because of the same limit of light speed. so my ass falls in a way similar to not having a chair.

In a neutron star there is a outer crust with ions. Those ions are supported by nuetrons from below. The ability to send support is limited by the speed of light. in a black hole the ions cannot perceive the layer of ions below them. The shell would collapse.

 

[phinds]

Sorry stefan, I still have little idea what you're trying to say except that neutron stars can cool off and black holes cannot. But I don't see how that goes back to your previous post. I'd blame myself for not understanding, but it's more fun to blame @phinds.

GRRRRRrrrrrr

 

[nikkkom]

My ass is interacts on my chair. My chair interacts with my carpet. If I was passing into the event horizon the carpet would not be able to send information to the chair. Thus the chair is not supported on carpet and moves down. Now my ass is unable to comunicate with the seat because of the same limit of light speed. so my ass falls in a way similar to not having a chair.

This is simply wrong. Material objects crossing horizon certainly can interact with each other in both directions: if you press on a spaceship wall while the spaceship falls into a BH and crosses EH, the wall will continue to press on your hand, even if it is closer to the center of BH than the hand.

The key here is neither the hand nor the wall are stationary. Both are falling into the BH.

The only "peculiar" thing here is that past the horizon, your hand and the wall moves faster (in proper velocity terms) than speed of light relative to the distant observer, thus the "outward" pressure of the wall on your hand is also pointing inward, from "distant observer" point of view. But locally, everything looks ordinary.

The "chair is not supported on carpet" picture assumes a magic chair which can levitate inside BH and not move towards the center. This is physical impossibility, no such chairs can exist.

 

[JLowe]

Analogies are useless

 

[phinds]

Analogies are useless

No, they are not even remotely useless, you just have to be careful about their limitations. I suggest the link in my signature

 

[stefan r]

The key here is neither the hand nor the wall are stationary. Both are falling into the BH.

That was my impression. A nuetron star has a supported surface. The black hole does not. That is definitely not a "giant neutron star cloaked in an event horizon".

The only "peculiar" thing here is that past the horizon, your hand and the wall moves faster (in proper velocity terms) than speed of light relative to the distant observer, thus the "outward" pressure of the wall on your hand is also pointing inward, from "distant observer" point of view. But locally, everything looks ordinary.

The "chair is not supported on carpet" picture assumes a magic chair which can levitate inside BH and not move towards the center. This is physical impossibility, no such chairs can exist.

Objects in free fall do something very similar to "levitating". A spaceship falling toward a black hole and a spaceship falling toward a neutron star should have a few similar experiences. However, a spaceship could crash onto the surface of a neutron star. A spaceship could spiral into a black hole and continue spiraling after passing the event horizon.

 

[Chronos]

A black hole has no physical surface, a neutron star does. The event horizon of a BH is merely a mathematical construct devoid of any physical significance.

 

[Jason R Carrico]

How can you say with certainty that there is no physical surface beyond the event horizon? That's mostly why I asked the question. I know I veered off with my analogy, but really, how do we know it's not a super compact body? I read somewhere about the interior of neutron stars described as disassociated particle soup and that led me to this question. I've read smarter people than me (not a high bar) who refer to infinites as indications the mathematical representation of a particular phenomenon is flawed. Suggesting that different equations are needed to accurately discribe it. It all just really peaks my curiosity.

 

[rootone]

I understand that quark stars are on the table in theory.
This would represent a state of matter which is intermediate between a neutron star and a black hole.
The problem with that is that no such form of matter has ever been observed,
and if it can exist, the properties of quark soup cannot be predicted.

 

[JLowe]

How can you say with certainty that there is no physical surface beyond the event horizon

They can't. There may be no known force past the neutron degenerate stage to stop the collapse to singularity, but at that point we're getting into scales we can just barely scratch the surface of. It seems plausible to me that something exists that wouldn't be a singularity that would have a horizon, but it's also possible that exactly what GR says will happen, will happen.

But in my personal opinion, which admittedly is next to useless, there is no singularity. Until I hear an argument for singularity I'm satisfied with, I'll probably stick to believing there is none, worthless as it may be.

 

[Drakkith]

How can you say with certainty that there is no physical surface beyond the event horizon?

No one is saying with certainty that there isn't a physical surface beyond the EH. What they're saying is that according to the rules of General Relativity there shouldn't be one.

 

[MichaelMo]

How can you say with certainty that there is no physical surface beyond the event horizon? That's mostly why I asked the question. I know I veered off with my analogy, but really, how do we know it's not a super compact body?

IMO, you're definitely asking the right questions. :) You might also take a gander at the Pauli exclusion principle and consider the fact that black holes can supposedly hold a charge. We don't really know what might exist below the event horizon, but the Pauli exclusion principle should preclude anything from achieving infinite density.

I read somewhere about the interior of neutron stars described as disassociated particle soup and that led me to this question. I've read smarter people than me (not a high bar) who refer to infinites as indications the mathematical representation of a particular phenomenon is flawed. Suggesting that different equations are needed to accurately discribe it. It all just really peaks my curiosity.

Great! :) It's awesome when something in science piques your curiosity. :)

 

[MichaelMo]

No one is saying with certainty that there isn't a physical surface beyond the EH. What they're saying is that according to the rules of General Relativity there shouldn't be one.

I'm a little uncomfortable with that statement. The rules of GR only insist on extreme geometric curvature and pressure in the presence of so much mass/energy, but extreme GR curvature doesn't automatically lead us to infinitely dense objects or "points". Only if our understanding of neutrons and quarks and such is correct, and the Pauli exclusion principle does not apply, can we say with absolute certainty what GR might 'predict' in extreme mass concentration cases.

 

[MichaelMo]

I understand that quark stars are on the table in theory.
This would represent a state of matter which is intermediate between a neutron star and a black hole.
The problem with that is that no such form of matter has ever been observed,
and if it can exist, the properties of quark soup cannot be predicted.

It should be noted that neutron star material as it's presumed to exist inside of neutron stars has never been directly "observed" either, I don't see why the core couldn't even be a combo of a quark star with a neutron material around the quark star. I'll mention the Pauli exclusion principle one more time because I think it's important, as well as the fact that black holes supposedly hold a charge. How do they hold their charge?

 

[Drakkith]

I'm a little uncomfortable with that statement. The rules of GR only insist on extreme geometric curvature and pressure in the presence of so much mass/energy, but extreme GR curvature doesn't automatically lead us to infinitely dense objects or "points".

As far as I know it does.

Only if our understanding of neutrons and quarks and such is correct, and the Pauli exclusion principle does not apply, can we say with absolute certainty what GR might 'predict' in extreme mass concentration cases.

We know with near-absolute certainty what GR predicts, but we don't know with any real amount of certainty what actually happens behind the event horizon.

It should be noted that neutron star material as it's presumed to exist inside of neutron stars has never been directly "observed" either, I don't see why the core couldn't even be a combo of a quark star with a neutron material around the quark star.

It might be. From wikipedia: https://en.wikipedia.org/wiki/Neutron_star#Structure

The composition of the superdense matter in the core remains uncertain. One model describes the core as superfluid neutron-degenerate matter (mostly neutrons, with some protons and electrons). More exotic forms of matter are possible, including degenerate strange matter (containing strange quarks in addition to up and down quarks), matter containing high-energy pions and kaons in addition to neutrons,[5] or ultra-dense quark-degenerate matter.

We don't really know what might exist below the event horizon, but the Pauli exclusion principle should preclude anything from achieving infinite density.

It is unknown what happens to matter inside a black hole. The PEP wouldn't apply if the in-falling matter is converted into bosons by the immense forces. And that's assuming the PEP even continues to hold inside the black hole. For all we know, it might not.

 

[nikkkom]

I'm a little uncomfortable with that statement. The rules of GR only insist on extreme geometric curvature and pressure in the presence of so much mass/energy, but extreme GR curvature doesn't automatically lead us to infinitely dense objects or "points". Only if our understanding of neutrons and quarks and such is correct, and the Pauli exclusion principle does not apply, can we say with absolute certainty what GR might 'predict' in extreme mass concentration cases.

We do know what GR predicts. Schwarzschild solution is not at all ambiguous.

GR predicts that beyond EH, direction towards the center becomes timelike. This means that there is no way for infalling matter to avoid moving towards it, just like you can't avoid moving into tomorrow.
Moreover, GR predicts that any matter reaches the center in a finite proper time interval. (What happens next, GR can't say, since math breaks down - curvature becomes infinite, etc).

The above is what people mean when they say that "GR predicts singularity".

This, of course, does not imply that this singularity is a mathematically well-behaving object. It is not.
In my opinion, the fact that GR predicts it is a breakdown of GR. Simply put, it does not correctly describe ultra-high-energy and ultra-small-distances behavior of gravitation. In my opinion, there is a better theory which gives more sensible description.

 

[Chronos]

Whatever might be hiding inside an event horizon it almost certainly is not a neutron star for. The most massive known neutron stars to date only run about 2 solar masses and the best existing measurements yield a radius of no less than 10km. That is significantly larger than the Schwarzschild radius for a 2 solar bh - which is about 6km. Assuming 10km is some kind of low limit for the radius of any neutron star. A mass of about 3.5 solar would be necessary to achieve a Schwarzschild radius of 10km. See https://arxiv.org/abs/1505.05155, The Dense Matter Equation of State from Neutron Star Radius and Mass Measurements, for further details. This appears to pretty much rule out the mega neutron star scenario. A quark star is not yet ruled out, but would require an equation of state far beyond nucleon density. As already noted, we have no evidence to suggest any state of matter with a density exceeding that of a neutron star. Most scientists suspect the singularity is nothing more than a mathematical artifact, and nature has demonstrated great resilience in avoiding the singularity paradox when it arises in other situations. I share this suspicion, but, also suspect the way around this disaster will be surprising. The clues are probably staring us in the face - e.g., how does a point particle [electron] avoid having infinite charge density [a charge singularity]?

 

[stefan r]

how does a point particle [electron] avoid having infinite charge density [a charge singularity]?

There is an uncertainty in position and momentum.

The same uncertainty should apply to particles in black holes. Any one electron would be near the singularity give or take a bit. Same/similar to the electron's position in an atom. Black hole is a singularity because there is stellar mass packed into that small space.

 

[Drakkith]

There is an uncertainty in position and momentum.

I'm pretty sure that doesn't resolve the charge singularity.

The same uncertainty should apply to particles in black holes. Any one electron would be near the singularity give or take a bit. Same/similar to the electron's position in an atom. Black hole is a singularity because there is stellar mass packed into that small space.

That's not how a singularity in GR works. It's not simply a point in space. It's also a point in time. You can't have uncertainty when the particle's world-line literally ends at the singularity.

 

[stefan r]

That's not how a singularity in GR works. It's not simply a point in space. It's also a point in time. You can't have uncertainty when the particle's world-line literally ends at the singularity.

I thought there was a time uncertainty too. I may have misunderstood the Eintein-Bohr debate.

Also does it take forever to reach the singularity?

 

[rootone]

No it does not, an infalling something reaches the (theoretical) singularity very shortly after crossing the event horizon.
Why?, because the infalling thing is trying to go faster than light, which as we all know is banned.

 

[nikkkom]

No it does not, an infalling something reaches the (theoretical) singularity very shortly after crossing the event horizon.
Why?, because the infalling thing is trying to go faster than light, which as we all know is banned.

I think the second sentence is wrong. Where did you get it?

 

[Jason R Carrico]

Why wouldn't everything approaching the event horizon already be traveling at or near the speed of light?

 

[rootone]

Yeah. that's what I meant, as far as anyone outside can see

 

[nikkkom]

Why wouldn't everything approaching the event horizon already be traveling at or near the speed of light?

Relative to what? Velocity is relative. Superluminal velocity relative to a distant observer is not prohibited in GR. The speed of light stays constant only locally.

 

[Jason R Carrico]

You're right. So let me clarify my question.

Why wouldn't anything caught in the gravitational field of the black hole be traveling at or near the speed of light, relative to the black hole, as it crossed the event horizon?

My next question would be;

Why would any observer, from any location, measure the speed of matter caught in the gravitational field of a black hole in reference to anything other than the black hole itself?

 

[Chronos]

The reference frame of the observer is irrelevant since c is c in all reference frames. Think of the old intro SR question about 2 rockets approaching from opposite directions at .9 c wrt a ground observer. Do the ground observer and rocket passengers disagree about anything besides whose watch is right?

 

[russ_watters]

Since you guys seem bent on picking apart the question instead of correcting it and answering it, let me ask it this way and see if we can get an answer:

What is the speed a remote observer at rest wrt the black hole measures for a freely falling (from infinity or equivalent) object as it approaches the event horizon?

I would think that since the escape velocity is C at the event horizon we would see the object asymptotically approaching C as it approaches the event horizon...

...unless Relativity effects make it look slower, similar to why we see x-rays generated by infalling matter...perhaps that represents the cutoff speed?

 

[Chronos]

It just like alice watching bob fall into a BH, he never quite reaches the EH from her perspective, he just redshifts into obscurity.

 

[Jason R Carrico]

Why can I not see newer posts on this thread? I keep getting emails saying there have been newer replies but I don't see anything. Why?