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Author Topic: Why do people think Relativity predicts event horizons?  (Read 19292 times)

Offline AndroidNeox

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The current model of black holes depicts infalling objects appearing to slow to a virtual halt outside the event horizon and to never reach the event horizon in finite time. But, this is supposed to be an illusion and in reality matter passes through and on to the singularity.

What bothers me is that this violates Relativity which requires that observations from all frames be equally valid.

While I concede that event horizons might form in finite time and the contemporary model could be correct, it’s not possible to use Relativity to justify the model. Any model that violates one of the fundamental assumptions Einstein relied on to develop Relativity is inconsistent with Relativity and no conclusion that depends on such a violation can be valid, under Relativity.

I might not be good enough at math to solve the GR equations to describe this but I got an A in all  my logic classes and I know that no logical argument is valid that depends upon violating one of its premises.

What I don’t understand is why people disregard the requirements of Relativity when using it to model physical systems. It wasn’t until about a decade after Einstein’s death that the general consensus changed from the “frozen star” model to one with event horizons and singularities but I’ve not been able to find a single justification for this belief.

Can anyone here explain why the accepted model changed?


 

Offline Pmb

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Re: Why do people think Relativity predicts event horizons?
« Reply #1 on: 12/11/2013 00:22:03 »
Quote from: AndroidNeox
Why do people think Relativity predicts event horizons?
The laws of physics predicts them.

Quote from: AndroidNeox
The current model of black holes depicts infalling objects appearing to slow to a virtual halt outside the event horizon and to never reach the event horizon in finite time. But, this is supposed to be an illusion and in reality matter passes through and on to the singularity.
It’s not an illusion. In relativity what is reckoned to happen depends on the observer. What each observer reckons is not an illusion.

Quote from: AndroidNeox
What bothers me is that this violates Relativity which requires that observations from all frames be equally valid.
Relativity has no such requirement. Observations need not be the same for all observers. For example; one observer might be able to rightly say that that he reckoned a moving rod to be entirely inside a barn while another observer can also say that there was no time at which the rod was entirely inside the same barn. In another example one observer might reckon that a charged object is radiating EM waves while another observer might also reckon that at no time the same charged object never radiated EM waves. The list goes on. In fact that’s why it’s called relativity because what’s observed is observer dependant.

Quote from: AndroidNeox
Can anyone here explain why the accepted model changed?
No accepted model changed. But what model is it that you are claiming changed and where in the above did you make this statement.
 

Offline Pmb

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Re: Why do people think Relativity predicts event horizons?
« Reply #2 on: 12/11/2013 01:06:51 »
One more thing -

Quote from: AndroidNeox
I might not be good enough at math to solve the GR equations to describe this but I got an A in all  my logic classes and I know that no logical argument is valid that depends upon violating one of its premises.
Where in your use of logic did you arrive at this assertion … Relativity which requires that observations from all frames be equally valid.

What do you think “observations from all frames” means and what does it mean to for them to be “equally valid” in your interpretation? I’ll tell you what it doesn’t mean. It doesn’t mean that all observations from all frames of reverence are identical.

Pleas use your skills in logic to go from the postulates of relativity to your assertion - … Relativity which requires that observations from all frames be equally valid.

Thanks
 

Offline Ethos_

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Re: Why do people think Relativity predicts event horizons?
« Reply #3 on: 12/11/2013 01:23:21 »
The current model of black holes depicts infalling objects appearing to slow to a virtual halt outside the event horizon and to never reach the event horizon in finite time. But, this is supposed to be an illusion and in reality matter passes through and on to the singularity.


What we see at the event horizon is information left there in the form of electromagnetic radiation. Think about it like this: The images we see across vast distances of the universe, some coming to us from about 13.7 billion light years distant are actually events that occurred 13.7 billion years in the past. It's not exactly the same at the event horizon because gravitational energies have actually slowed the advance of time itself. But in both cases, the events we are seeing are real and not illusionary. Just because they appear to be current to our frame of reality does not mean that they are current to the process unfolding in that particular frame.
« Last Edit: 12/11/2013 01:25:14 by Ethos_ »
 

Offline Pmb

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Re: Why do people think Relativity predicts event horizons?
« Reply #4 on: 12/11/2013 01:58:38 »
Quote from: Ethos_
What we see at the event horizon is information left there in the form of electromagnetic radiation. Think about it like this: The images we see across vast distances of the universe, some coming to us from about 13.7 billion light years distant are actually events that occurred 13.7 billion years in the past. It's not exactly the same at the event horizon because gravitational energies have actually slowed the advance of time itself. But in both cases, the events we are seeing are real and not illusionary. Just because they appear to be current to our frame of reality does not mean that they are current to the process unfolding in that particular frame.
Nice response! :)
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #5 on: 13/11/2013 19:16:39 »

1) The requirement that Relativity requires causal consistency across all frames:

The “Principle of Relativity” requires that all frames of reference must exhibit the same rules. Observations of events in one frame must be compatible with any other frame. By compatible I mean that the observations from any frame can be translated to those of any other frame by using the equations of Relativity.

Another way of saying this is that, “no physical observable can depend on how you choose coordinates… And a lot of things you  might detect are not frame invariant--- the energy of a photon for example” I use quotes because that’s the exact phrase used in a recent email to me by one of the physicists from Fermilab who was also involved in the LIGO gravity wave project.

2) “What we see at the event horizon is information left there in the form of electromagnetic radiation.”

Electromagnetic radiation doesn’t hang around. It always moves at the speed of light.

Regarding your comparison to the observable horizon… just as it’s not possible for any object to reach the observable horizon, because it moves away at the speed of light, nothing can fall to an event horizon because spacetime stretches without bound as the concentration of mass approaches the Schwarzschild radius (for the simplest black holes).

It might help with your confusion to consider that the time rate for an infalling object/observer is exponentially related to that of a distant, inertial observer. By the time the infalling object has run out of time and reached the event horizon, an infinite amount of time will have passed for the external observer.

If the idea of the object disappearing into an infinite redshift is bothering you, just imagine the infalling object to be a mirror and the radiation you use to see it to be from a light beam coming from the distant inertial observer. This way the gravitational redshift is eliminated from observations.
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #6 on: 13/11/2013 19:20:24 »
Quote from: AndroidNeox
Why do people think Relativity predicts event horizons?
The laws of physics predicts them.

No. General Relativity makes black holes inevitable but event horizons are impossible.
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #7 on: 15/11/2013 01:47:42 »
A event horizon is where a observer find 'reflected light' from a object to cease to exist for him, as I think of it. You can take a look at https://en.wikipedia.org/wiki/Event_horizon for a description. There will be a real event horizon as defined relative a universe, and then apparent event horizons, as defined relative a observer.

"The definition of an absolute horizon is sometimes referred to as teleological, meaning that it cannot be known where the absolute horizon is without knowing the entire evolution of the universe, including the future. This is both an advantage and a disadvantage. The advantage is that this notion of a horizon is very geometrical, and does not depend on the observer, unlike apparent horizons, for example. The disadvantage is that it requires the full history (all the way into the future) of the spacetime to be known. In the case of numerical relativity, where a spacetime is simply being evolved into the future, only a finite portion of the spacetime can be known."

So what we see is apparent horizons, which on the other hand doesn't invalidate your observations of no light being reflected any more.
 

Offline spartaman64

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Re: Why do people think Relativity predicts event horizons?
« Reply #8 on: 15/11/2013 03:23:38 »
Because infinities when we get to black holes arrrg relativity why do you fail us
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #9 on: 15/11/2013 13:55:34 »
Now that depends on how you define relativity. Trying to define it versus a universe, is in a way a assumption of a container, containing us all. Defining it as a relation between the observer and the observed avoid this assumption. Using the last one relativity does not fail anywhere, it will always be about you, 'relative' another frame of reference, in where your definitions of time, distance, constants, principles, ad infinitum will define what time dilations, Lorentz contractions, etc etc you find. From that point of view an apparent event horizon is a real 'event horizon' ..... For you.
 

Offline JP

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Re: Why do people think Relativity predicts event horizons?
« Reply #10 on: 15/11/2013 14:04:28 »
Quote from: AndroidNeox
Why do people think Relativity predicts event horizons?
The laws of physics predicts them.

No. General Relativity makes black holes inevitable but event horizons are impossible.

No, what would be impossible is not to have an event horizon.  If a black hole exists, there must be some region from within which light can't escape to the rest of the universe.  Outside that region, light can escape from the gravitational pull of the black hole.  So clearly there's a boundary between those regions.

That boundary can't depend on the observer, either, since if one observer can view light escaping to the universe and the other can't, that's not only a huge paradox, but means that different observers see different laws of physics!

What we can't observer, from our perspective outside a black hole, is anything falling through the event horizon, but that's got nothing to do with whether it exists or not.
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #11 on: 15/11/2013 14:45:42 »
Don't agree there JP. A apparent event horizon should be able to be defined as that 'boundary' you refer to, from where no light can be reflected as all light, from your measurements, is gone, into that black hole. And if I stop defining the universe as a 'objective container' observer dependencies are real. And they are, each time you measure them, as  'real' as can be, for you.

That is what we live by JP, our measurements.
==

You need local constants and principles, shared by all frames of reference, to define such a 'universe'. And you need 'communication' between those frames of reference, resting/building on/from those constants and principles. And it should give you infinites when that 'communication' breaks down. It's not about the universe we see being an 'illusion', as much as it is about defining it from local principles, shared by all 'frames' possible to measure.


It creates a same universe as the one we measure on, but it defines it locally, thereby avoiding the discussion about what is 'more real' in two different measurements, getting different answers. From that point of view both are as real as they can become, from each observers frame of reference.
« Last Edit: 15/11/2013 15:30:14 by yor_on »
 

Offline JP

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Re: Why do people think Relativity predicts event horizons?
« Reply #12 on: 15/11/2013 15:25:58 »
Don't agree there JP. A apparent event horizon should be able to be defined as that 'boundary' you refer to, from where no light can be reflected as all light, from your measurements, is gone, into that black hole. And if I stop defining the universe as a 'objective container' observer dependencies are real. And they are, each time you measure them, as  'real' as can be, for you.

That is what we live by JP, our measurements.
==

You need local constants and principles, shared by all frames of reference, to define such a 'universe'. And you need 'communication' between those frames of reference, resting/building on/from those constants and principles. And it should give you infinites when that 'communication' breaks down. It's not about the universe we see being an 'illusion', as much as it is about defining it from local principles, shared by all 'frames' possible to measure.


It creates a same universe as the one we measure on, but it defines it locally, thereby avoiding the discussion about what is 'more real' in two different measurements, getting different answers. From that point of view both are as real as they can become, from the observers frame of reference.

The fact is, a point inside the black hole cannot send information to a distant star outside the black hole.  This has to be true independent of your reference frame.
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #13 on: 15/11/2013 15:38:12 »
Yes, that one must be true for all frames of reference, sharing those constants and principles. And that one I would define to the fact that there exist local constants, being equivalent for all frames of reference.  Like a security net, keeping our universe together, but it also need some mean for communicating, and what that one should be? You have 'c' naturally, but then again, would that be a propagation from such a point of view? Or would it just be a limit of communication, as what it suggest is that my measurement is as good as the next persons, none lying. Meaning that it is the one that fit my universe, even if yours measurement states something different to you.
=

The other point is that, assuming a black hole to exist, it have a presence even when defined as a singularity, impossible to measure on past that event horizon. There it won't matter what apparent event horizon I find, it will still be impossible to measure past it as I understands. And the presence of it, even when unable to measure, should then be able to be defined as it not sharing those local limits our 'commonly same universe' builds on. Meaning that something still can 'exist' for us, even though not sharing our local definitions? A weird thought, isn't it? We can pass a event horizon, but we can't get back.
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Like a bubble in a bubble somehow, as you as me JP, I think? Still expect the inside of it resting on the same physics we find outside it, that is if I remember it right?
==

The universe we find us able to measure on is defined by 'two way communications'. It doesn't matter for this if your definition of a distance of propagation A to B differ from mine measurement. We can still define it as communicating both ways, and we can make it make sense using Lorentz transformations. As you point out, a black hole does not use a two way communication, unless we would refer to Hawking radiation, From our own time limited frames, it won't communicate though. And that becomes the 'surface' of that bubble. But if I assume that past it I would find the same physics as outside it I have two options. Using Hawking radiation it's no problem, it still 'communicates', even though not measurably for us. Using a 'time limited' definition though, it does not. The first places it inside our 'commonly same universe', even when impossible to measure on for us. The other?

In the first my 'bubble in a bubble' disappear, doesn't it?
=

And that bring us to the concept of 'meaningful communication'. Is Hawking radiation a meaningful communication? If I define something meaningful as something able to decipher by the recipient (us). Would Hawking radiation tell us anything about the inside of that black hole? I don't think it would, but I'm willing to listen.

What you referred to JP, was, as I think :) just that concept, right? Like sending a radio transmission from inside a event horizon, describing that inside. And we wouldn't get it (outside that EH), ever.
« Last Edit: 15/11/2013 16:32:55 by yor_on »
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #14 on: 17/11/2013 22:18:19 »
I'm afraid people aren't understanding the point of this thread. I'm not asking for the contemporary model of black holes. I know what it is and I agree with Einstein that it's wrong. What I asked is why people think event horizons can form.

People are just assuming they do, even though that violates general relativity by violating one of the assumptions GR is based on.
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #15 on: 18/11/2013 00:15:21 »
The problem is that Einstein, in the end, did agree on black holes existing, I think he reversed his thoughts several times on that one. And if they do, there must be a point of no return for infalling mass and energy, as light. You can either define that point relative the full life of a universe, as described above, or you define it relative the observer in each case. In both cases the measurements you 'may be able to' make (the first case is very theoretical, and I can't see how you should construct a experiment there?) should give you the same answer though, no light (mass energy) reflected/returned from that point on. What exactly makes you doubt a event horizon? there are some mathematical hypothesis's over a black hole without a event horizon being possible but? That would be a very strange thing to me, as everything only should have one path, to its center, no matter how you turn it around. Anyway, here you go. See if it makes more sense to you. Destroying black holes with test bodies.

=

I think that question might depend on the physics of a black hole. I assume the same physics inside as 'outside its event horizon', but if there isn't? Then maybe you can make an assumption in where you can bypass the mass (gravity) by angular momentum for example? Quite strange idea. It's like one infinity meeting another, a infinite mass (or 'infinite gravity' might be better here?) meeting a infinite angular momentum, where the angular momentums 'infinity' then need to be of a greater magnitude than the mass? And if you use a 'one to one' correspondence to define what a infinity is, I find big problems imagining the possibility of defining one infinity as bigger than any other?
« Last Edit: 18/11/2013 00:43:09 by yor_on »
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #16 on: 18/11/2013 19:57:09 »
The problem is that Einstein, in the end, did agree on black holes existing, I think he reversed his thoughts several times on that one.
I'm not familiar with his changing his opinion. That's surprising since until about a decade after his death the consensus in physics was that the "frozen star" model was correct. In The Trouble With Physics, Smolin claims Einstein always insisted that event horizons cannot form. I'd be interested to know if that's not correct.

But, despite my tremendous respect for Einstein, even if he did change his mind on the subject that wouldn't change anything since the reality of physics is independent of our opinions. My point, which I maintain, is that it's not possible to use Relativity to demonstrate the existence of event horizons. This is because if there is a point of no return then Relativity is wrong. Perhaps it is wrong under extreme circumstances but you can't use Relativity to prove an outcome that depends on Relativity being wrong unless Relativity itself is inconsistent.

If it has been demonstrated that G.R. is wrong regarding event horizons, that's a separate issue. I'd be fascinated to learn about that but I don't believe it to be the case.
Quote
And if they do, there must be a point of no return for infalling mass and energy, as light. You can either define that point relative the full life of a universe, as described above, or you define it relative the observer in each case. In both cases the measurements you 'may be able to' make (the first case is very theoretical, and I can't see how you should construct a experiment there?) should give you the same answer though, no light (mass energy) reflected/returned from that point on. What exactly makes you doubt a event horizon? there are some mathematical hypothesis's over a black hole without a event horizon being possible but? That would be a very strange thing to me, as everything only should have one path, to its center, no matter how you turn it around. Anyway, here you go. See if it makes more sense to you. Destroying black holes with test bodies.
The important thing to remember is that the relationship between the total time experienced by an infalling observer as they fall into a black hole and the time experienced by an external inertial observer is exponential. Though the time remaining for the infalling observer will be finite and maybe even brief, that time will not elapse until an infinite amount of time has passed for the external observer. These two perspectives are mutually consistent.

Regarding how to construct the experiment: Drop a mirror into the black hole. Illuminate it with a light beam. If the contemporary model of black holes is correct, the mirror will appear to remain outside the event horizon forever even though it passes through the event horizon and stops reflecting light. At that point, Relativity would break down because not all frames would be consistent for observations.

Quote
I think that question might depend on the physics of a black hole. I assume the same physics inside as 'outside its event horizon', but if there isn't? Then maybe you can make an assumption in where you can bypass the mass (gravity) by angular momentum for example? Quite strange idea. It's like one infinity meeting another, a infinite mass (or 'infinite gravity' might be better here?) meeting a infinite angular momentum, where the angular momentums 'infinity' then need to be of a greater magnitude than the mass? And if you use a 'one to one' correspondence to define what a infinity is, I find big problems imagining the possibility of defining one infinity as bigger than any other?
The problem I see is that you are beginning with the assumption that event horizons exist when that is the question being considered. Relativity doesn't predict their existence so I'd be interested to know what physical theory you're using to arrive at (or, rather not arrive at but begin with). There are no problems with infinities unless the event horizon exists, in which case not only does causality get violated but infinite energies are involved... and infinite time passes within a finite period.

No, I can't accept that model. The contemporary model of black holes is nonsense. The frozen star model is self-consistent, entails no infinities, and doesn't violate causality... besides being the model required by Relativity.
 

Offline yor_on

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Re: Why do people think Relativity predicts event horizons?
« Reply #17 on: 18/11/2013 21:14:27 »
Got to admit that black holes are one of the most confusing as well as interesting ideas I know of. As for how Smolin defines it I don't know, would be nice to see the citation. But I know that Einstein changed his mind on Black holes. When it comes to a event horizon specifically? Well, I haven't seen any discussion about that one when it comes to Einstein and history, possibly Smolin is correct in arguing that Einstein didn't like that idea, as it could be read as relativity breaks down at a event horizon. But as far as I get it the event horizon has nothing to do with that, presuming that there is a center of 'infinite mass'.

"The simplest answer is that the curvature of space-time is a smoothly changing function of distance up to, and through, the event horizon. There is no indication from the curvature (Riemann's Curvature Tensor, or even Ricci's for that matter) that anything serious is happening just inside the event horizon. Einstein's 'equations' work just fine so long as the local curvature of space-time (the strength of the gravitational field) does not become singular. This does not happen just inside an event horizon, but only happens as you approach the 'r=0' singularity itself.

What all of this means is that the mathematical properties of spacetime that matter (its curvature) change smoothly through the event horizon, much like a ride in a sled down a snow-covered hill. Now, to prove that this is in fact the case will probably not be possible because we can never extract information from inside a black hole withough dying, or never being able to return! "

As for me I would expect the physics inside a Event Horizon to be the same as outside, I do not expect 'time' to become 'space' and 'space' become 'time' for a infalling observer. To the observer the local arrow should be 'as always', his ride toward the singularity's center taking a, for him, measurable time.

What experiment are you referring to? Not the first example over a whole space-times history, right? That's the one I wouldn't know how to define. As for the one with a 'apparent event horizon'. The whole idea of that, is that it for the observer becomes his 'limit of observation'. Meaning that wherever he finds it to be, that also will be the place of 'no return' for his experiments, and as far as I understands it, no more reflections observed, from his frame of reference. That should mean that your mirror will 'disappear' for the observer at that point. And there will also be a 'dimming' of that mirror, due to the redshift of that reflected light as it propagates 'uphill', getting 'stretched out' by the Black holes gravity if described as waves. So it will probably just dim out and disappear as it falls in. To that you can add a time dilation, making it 'slow down' for the observer as it closes in on that event horizon.

As for why a event horizon is needed? It's just a place where all geodesics starts to lead to a same place, relative the observer, or a 'whole SpaceTime'. And that should be the center of its singularity. And light follows those geodesics. A reflection can only be seen if that geodesic leads back to you. A event horizon is defined from the way light, (energy), gravity and mass interacts. But a black hole is truly weird, as it do contain a infinity at some point, if the mathematics are correct. And there is no way to describe what happens there, as far as I know. And it's GR that describes a black hole. Karl Schwarzchild used Einstein's theory of general relativity to define a non spinning black hole 1916.

"An object whose radius is smaller than its Schwarzschild radius is called a black hole. The surface at the Schwarzschild radius acts as an event horizon in a non-rotating body (a rotating black hole operates slightly differently). Neither light nor particles can escape through this surface from the region inside, hence the name "black hole". The Schwarzschild radius of the (currently hypothesized) supermassive black hole at our Galactic Center would be approximately 13.3 million kilometres." from Schwarzschild radius.
=

I wrote ' A event horizon is defined from the way light, (energy), gravity and mass interacts.' But I don't think you need to add 'time' to that. Time is to me locally invariant, its arrow of time always ticking at a same rate for you. And as I define it as equivalent to 'c', also a local invariant, I therefore will assume that this will hold true for accelerations/decelerations too. 'c' must be 'c' at all kinds of 'motion' for the equivalence to hold. And that goes for the inside of a black hole too.
« Last Edit: 18/11/2013 21:53:12 by yor_on »
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #18 on: 19/11/2013 17:28:38 »
Got to admit that black holes are one of the most confusing as well as interesting ideas I know of. As for how Smolin defines it I don't know, would be nice to see the citation. But I know that Einstein changed his mind on Black holes. When it comes to a event horizon specifically? Well, I haven't seen any discussion about that one when it comes to Einstein and history, possibly Smolin is correct in arguing that Einstein didn't like that idea, as it could be read as relativity breaks down at a event horizon. But as far as I get it the event horizon has nothing to do with that, presuming that there is a center of 'infinite mass'.
The quote is something like, Einstein always insisted that event horizons cannot form and continues by saying but he was wrong. I think it's in chapter 1 of The Trouble With Physics.
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"The simplest answer is that the curvature of space-time is a smoothly changing function of distance up to, and through, the event horizon. There is no indication from the curvature (Riemann's Curvature Tensor, or even Ricci's for that matter) that anything serious is happening just inside the event horizon. Einstein's 'equations' work just fine so long as the local curvature of space-time (the strength of the gravitational field) does not become singular. This does not happen just inside an event horizon, but only happens as you approach the 'r=0' singularity itself.
Spacetime is stretched by concentrations of mass. As the concentration approaches the Schwarzschild limit, the stretch approaches infinity. It is no more possible for matter (including light) to reach an event horizon than it is to accelerate a particle of non-zero rest mass to the speed of light.
Quote
What all of this means is that the mathematical properties of spacetime that matter (its curvature) change smoothly through the event horizon, much like a ride in a sled down a snow-covered hill. Now, to prove that this is in fact the case will probably not be possible because we can never extract information from inside a black hole withough dying, or never being able to return! "
It's simple to present a thought experiment to study the problem, though. The simplest is to drop a mirror into the black hole and shine a beam of light off of it and observe the reflection. Because the beam retraces its path into the gravity well, any gravitational redshift is eliminated. Perhaps you can describe what the contemporary model of black holes would predict. I know Einstein would say that the mirror will, from the perspective of the external observer, slow to a virtual halt and the light beam reflection could be observed forever.

Another thought experiment is based on the one Hawking used in calculating the thermodynamics of event horizons in which he lowers a box full of light via a rope down to the vicinity of the E.H. and then dumps the light in. Using the same setup, replacing the box with a mirror, lower the mirror toward the event horizon. Now, measure the distance down to the mirror as it's lowered by bouncing a laser beam off of it and feeding the return beam into an interferometer... counting each dark-light transition would give the distance in terms of wavelength of light. Before the mirror passes through the event horizon, an infinite number of such transitions will be counted, an infinite amount of rope would be payed out.
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As for me I would expect the physics inside a Event Horizon to be the same as outside, I do not expect 'time' to become 'space' and 'space' become 'time' for a infalling observer. To the observer the local arrow should be 'as always', his ride toward the singularity's center taking a, for him, measurable time.
Since the path length from every point in spacetime to any event horizon is always infinite, the potential conditions inside the event horizon never arise. Not even the matter that initially collapsed to form the black hole can reach it.

I might have figured out where the problem is. People might be calculating the instantaneous path length to the event horizon instead of taking into account that spacetime continues to stretch indefinitely as the matter that has fallen into the black hole continues toward the unreachable Schwarzschild limit.
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What experiment are you referring to? Not the first example over a whole space-times history, right? That's the one I wouldn't know how to define. As for the one with a 'apparent event horizon'. The whole idea of that, is that it for the observer becomes his 'limit of observation'. Meaning that wherever he finds it to be, that also will be the place of 'no return' for his experiments, and as far as I understands it, no more reflections observed, from his frame of reference. That should mean that your mirror will 'disappear' for the observer at that point. And there will also be a 'dimming' of that mirror, due to the redshift of that reflected light as it propagates 'uphill', getting 'stretched out' by the Black holes gravity if described as waves. So it will probably just dim out and disappear as it falls in. To that you can add a time dilation, making it 'slow down' for the observer as it closes in on that event horizon.
I think I've addressed these concerns in the experiment I describe, above, where gravitational redshift is cancelled out.

Relativity requires that observations made in any reference frame can be translated (via the equations of Relativity) to those of any other frame. The insurmountable problem is that, if there is an event horizon, if it's possible to do as Hawking suggests and have a reference frame that's in the E.H.'s vicinity, then it is impossible to reconcile observations of matter passing into the E.H. with observations of distant observers.

The error isn't in Relativity. The error is in misapplying it.
 

Offline Bill S

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Re: Why do people think Relativity predicts event horizons?
« Reply #19 on: 19/11/2013 23:39:42 »
Quote from: yor_on
I do not expect 'time' to become 'space' and 'space' become 'time' for a infalling observer.

Now, there’s an interesting thought!  If space and time changed places, would we notice any difference?  I think not.

What could it possibly mean?
 

Offline jeffreyH

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Re: Why do people think Relativity predicts event horizons?
« Reply #20 on: 20/11/2013 01:37:43 »
Oh dear it's controversy time. I do believe in the frozen star hypothesis and for this reason. The matter at the surface of a star that is collapsing towards the schwarzschild radius will itself undergo time dilation as it nears this point. The total gravitation below the surface will be increasing and must induce time dilation on matter nearer the surface. Otherwise time dilation just fails totally. As this matter at the surface approaches the horizon it to will take an ever longer time to get there. You can't have one rule for matter off the surface and another for the infalling surface itself. It too is effected by the gravitation from its own centre of gravity.

As an update, you can take this dilation all the way to the centre of the mass. If you take as your measurement half the radius of the collapsing mass then as this collapses internally it will also approach its own event horizon. As before the mass at its assumed surface will also take an infinite time to reach its own event horizon.

I have been asking questions such as what will fit inside a Planck volume to see if anyone else was thinking along these lines but few took that one up. There is usually a reason for the strange questions I ask.
« Last Edit: 20/11/2013 02:12:14 by jeffreyH »
 

Offline Bill S

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Re: Why do people think Relativity predicts event horizons?
« Reply #21 on: 20/11/2013 02:27:10 »
Quote from: AndroidNeox
Since the path length from every point in spacetime to any event horizon is always infinite, the potential conditions inside the event horizon never arise. Not even the matter that initially collapsed to form the black hole can reach it.

Hopefully JP will not mind if I quote from another thread.  Proves I took notice.  :) 

Quote from: JP
Infinity is used in physics as a stand-in for "very large," and it comes into play with "very small" (infinitesimally small) and we can use the mathematical tools for handling infinity in these cases to produce useful results, often with much less work than would be involved if we tried to plug in large or small numbers.

If this is right, the stretching of spacetime is not really infinite, it’s just so large that it is convenient to refer to it as infinite. 

I would be the last to argue with anyone who maintained that it is impossible to reach a point that is infinitely far away, such would not be the case if the point were simply an unthinkably long way away. 

Surely all we are saying when we talk of finite things going to infinity is that they reach a point where our finite calculations are unable to cope, whether those calculations involve relativity, or not.
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #22 on: 20/11/2013 02:29:05 »
Oh dear it's controversy time. I do believe in the frozen star hypothesis and for this reason. The matter at the surface of a star that is collapsing towards the schwarzschild radius will itself undergo time dilation as it nears this point. The total gravitation below the surface will be increasing and must induce time dilation on matter nearer the surface. Otherwise time dilation just fails totally. As this matter at the surface approaches the horizon it to will take an ever longer time to get there. You can't have one rule for matter off the surface and another for the infalling surface itself. It too is effected by the gravitation from its own centre of gravity.

As an update, you can take this dilation all the way to the centre of the mass. If you take as your measurement half the radius of the collapsing mass then as this collapses internally it will also approach its own event horizon. As before the mass at its assumed surface will also take an infinite time to reach its own event horizon.

I have been asking questions such as what will fit inside a Planck volume to see if anyone else was thinking along these lines but few took that one up. There is usually a reason for the strange questions I ask.

Right. I imagine a neutron star on the verge of collapse to a black hole having that last little bit of matter dropped onto it like the straw that broke the camel's back. The nucleation point (where the collapse begins) will be at the surface, where gravity is most intense. As the matter begins falling together and approaches the Schwarzschild limit, spacetime stretching will hold it apart, almost frozen.

Can you explain more about your thinking regarding Planck scale?
 

Offline AndroidNeox

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Re: Why do people think Relativity predicts event horizons?
« Reply #23 on: 20/11/2013 02:38:20 »

Quote from: JP
Infinity is used in physics as a stand-in for "very large," and it comes into play with "very small" (infinitesimally small) and we can use the mathematical tools for handling infinity in these cases to produce useful results, often with much less work than would be involved if we tried to plug in large or small numbers.

If this is right, the stretching of spacetime is not really infinite, it’s just so large that it is convenient to refer to it as infinite. 

I would be the last to argue with anyone who maintained that it is impossible to reach a point that is infinitely far away, such would not be the case if the point were simply an unthinkably long way away. 

Surely all we are saying when we talk of finite things going to infinity is that they reach a point where our finite calculations are unable to cope, whether those calculations involve relativity, or not.

Sometimes infinity really is infinity. Relativity has some. For example, if you apply some finite acceleration to an object with non-zero rest mass, like a bowling ball or a proton:

Question: How long will it take to accelerate the object to the speed of light?
Answer: Infinitely long

Question: How much energy will be required to accelerate the object to the speed of light?
Answer: Infinite energy
 

Offline Ethos_

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Re: Why do people think Relativity predicts event horizons?
« Reply #24 on: 20/11/2013 02:55:07 »



Sometimes infinity really is infinity. Relativity has some. For example, if you apply some finite acceleration to an object with non-zero rest mass, like a bowling ball or a proton:

Question: How long will it take to accelerate the object to the speed of light?
Answer: Infinitely long


That position sounds all well and good but what about the inflationary period following the big bang? It is surmised that during this event, the speed of light was exceeded, and it didn't take eternity or infinitely long to reach.
 

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Re: Why do people think Relativity predicts event horizons?
« Reply #24 on: 20/11/2013 02:55:07 »

 

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