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sunnsm
2013-Sep-24, 07:16 PM
This is my second question on the forum...Why cant black hole actually be dead star which has burned out all the fuel and had a huge mass at the time of it death..Since there is no more fusion and gravity being the only dominant force...it just accumulates everything that comes near it...
It probably is a super dense object with density at infinity...

antoniseb
2013-Sep-24, 07:57 PM
... Why cant black hole actually be dead star which has burned out all the fuel and had a huge mass at the time of it death...
I'm not sure what you're getting at. We think that stellar mass black holes are more or less exactly what you are suggesting. Did you read somewhere that they aren't?

sunnsm
2013-Sep-24, 08:41 PM
Well , the question actually was what happens beyond the event horizon. You become part of the singularity ...There is so much unknown what exactly is beyond the event horizon and or on the actual surface of the black hole.....Most of the equations fail to what beyond.. But looking at it logically...isnt it one big dead rock for which there is no escape velocity. I do not come across this explanation of what might actually be inside of the black hole.

antoniseb
2013-Sep-24, 09:02 PM
...isnt it one big dead rock for which there is no escape velocity. I do not come across this explanation of what might actually be inside of the black hole.
It could be one big rock ... except we are pretty sure that it must at least collapse into neutron star material, and the lack of neutron stars above about 2 solar masses also strongly suggests that there must be some further collapse brought on by gravity. Now, if it were to only collapse just so far, and then be a big dense object inside the horizon, you'd expect it to have a strong quadupole and octupole component to its gravitational field, which we should be able to detect in its effect on the accretion disks or any close orbiting companions, but so far it hasn't been observed.

WayneFrancis
2013-Sep-25, 01:08 AM
Well , the question actually was what happens beyond the event horizon. You become part of the singularity ...There is so much unknown what exactly is beyond the event horizon and or on the actual surface of the black hole.....Most of the equations fail to what beyond.. But looking at it logically...isnt it one big dead rock for which there is no escape velocity. I do not come across this explanation of what might actually be inside of the black hole.

There is no "surface" that we know of. There can be no "rock" to be on the surface of. The gravitational pressure is so great that matter as we know it couldn't hold up if it tried to stay any distance from the very centre of the black hole.

For example a neutron star has a surface but because of the gravity there anything you throw at it changes. Gold becomes neutrons. Carbon becomes neutrons. Lead becomes neutrons. It is slightly more complicated then that but that is the basic idea. Take a carbon atom that falls on the neutron stars surface. A carbon atom has 6 protons, 6 neutrons and 6 electrons. When it is on the surface of the neutron star the gravity is so strong it overwhelms the electron degeneracy pressure of the atom that keeps the electrons from getting to close to each other and the nucleus of the atom. The nucleus breaks down and normally free neutrons would decay into a proton and electron and release a little bit of energy in the process. But here gravity takes over as the force that stops the neutron from decaying. It also provides the force to combine an electron & proton into a neutron.

So matter changes in a neutron star because of the extreme gravity. With a black hole that gravity is even greater. It is so great that now even the neutrons can't hold up against each other. As the neutron degeneracy pressure is over come all those neutrons essentially will break down. Into exactly what? I don't know. Could be just be a form of energy. But since the gravity is so great that energy can't escape. The energy still has the same gravitational influence as the matter did but it has essentially folded that space around it back in on itself. This means that energy has no where to go but to the centre. Because it is some type of energy an not matter as we know it there is no "size" constraint to it.

In reality our equations don't fail at the event horizon. We can model what is going on far past that point. It is only near the singularity that our models really start to break down. The caveat to this is while our models seem fine just beyond the event horizons there is no way of actually verifying them. We believe our models are correct because they are very accurate up to that point and we don't really expect a drastic change in physics at that point.

There is some speculation that there could be a intermediate object between Neutron Stars and Black holes. But those objects would have a very small range of mass. Balancing a razors edge. Others, much smarter then me, probably could describe what happens when neutrons break down.

sunnsm
2013-Sep-30, 06:25 PM
Thank you Wayne and Antoniseb for your explanations.
Are there any good links on what might exist beyond the event horizon since most of the sites dont seem to explain much.
To further the discussion, assuming the neutron degeneracy pressure being the greatest for the atomic level, the black hole is basically a soup of sub atomic particles ...where the higgs field is concentrated at the center...causing the immense gravity. Since no atomic based structures exist fusion does not occur...which is the basis for all the stars .

WayneFrancis
2013-Oct-02, 02:43 AM
Thank you Wayne and Antoniseb for your explanations.
Are there any good links on what might exist beyond the event horizon since most of the sites dont seem to explain much.
To further the discussion, assuming the neutron degeneracy pressure being the greatest for the atomic level, the black hole is basically a soup of sub atomic particles ...where the higgs field is concentrated at the center...causing the immense gravity. Since no atomic based structures exist fusion does not occur...which is the basis for all the stars .

I'm not sure if it would even be sub atomic particles any more because they obey the Pauli exclusion principle in that no 2 fermions can exist in the same quantum state at the same time. Atoms are ultimately made of fermions but after neutron degeneracy pressure is over come I think, someone can correct me if I'm wrong, that those fermions would have to change into things link Bosons that are not restricted by the Pauli exclusion principal. In layman's terms the neutron star is the most compact configuration of atomic particles we know of. When gravity exceeds this pressure all those neutrons would have to change into something that doesn't have this restriction. Bosons, A.K.A. thinks like photons A.K.A. energy has no upper limit with regard to spatial location. So it would just be some sea of energy falling to the centre of mass of the object.

And yes so since no atomic structures exists no fusion occurs. The reality is something probably much more complex with space time warping in on itself. Someone passing the event horizon wouldn't instantly turn into energy because our mass wouldn't have been at a point where it was breaking even electron degeneracy pressure and tidal forces would probably be responsible for ripping us apart. I've never really even thought about the differences of what might go on before.

I probably made it more confusing now :/

Jeff Root
2013-Oct-02, 07:18 AM
It pleases the FSM that every thread on the subject of what
happens to stuff that falls into a black hole should mention


S P A G H E T T I F I C A T I O N .

Everything falling in gets stretched radially and squeezed
circumferentially as it nears the center. It is spaghettified.

-- Jeff, in Minneapolis

WayneFrancis
2013-Oct-02, 08:05 AM
Agreed and sorry for displeasing the FSM. :)
But this does make me think that what happens to the matter that the BH was initially made up of would undergo a very different process then matter that was later deposited into the BH. I know we've had posts before on how the EH would propagate out from the centre of a forming BH and envelope matter but I never really considered what actually happens to matter when the neutron degeneracy pressure is over come. What is the standard model prediction for what will happen at that point?

Jens
2013-Oct-02, 08:11 AM
It pleases the FSM that every thread on the subject of what
happens to stuff that falls into a black hole should mention


S P A G H E T T I F I C A T I O N .


Hmmm. Let us note some interesting coincidences.

1. CERN is near Italy.
2. CERN's LHC is supposed to produce mini black holes.
3. Italy has a lot of spaghetti.

Does this lead to some conclusion?

Hornblower
2013-Oct-02, 03:49 PM
Here is a thought exercise, based on my admittedly incomplete grasp of the pertinent physics.

Suppose we could somehow assemble 20 billion solar masses of hydrogen and helium into a spherical globule slightly larger than the Schwarzschild radius while keeping it cold, and then let it contract under its own gravity. (In the real universe we do not know of a possible means to create such a scenario.) As seen from afar it would just fade out from view as it fell in, and we never would know anything further but the mass as shown by its gravitational signature, along with charge and angular momentum, if any. We would see only a circular black spot surrounded by a gravitationally lensed view of whatever is beyond it.

Shortly after the mass drops below the critical radius, a hypothetical observer would find that it still is just ordinary gas. In that frame of reference it would collapse into a singularity in a finite amount of time, while getting blazing hot from adiabatic compression. During that time I would expect fusion into heavier elements, followed by continuing collapse beyond what can be supported by electron and neutron degeneracy. After the latter it is transformed into a state that can undergo unlimited compression until our best available body of theory breaks down.

Once again, don't take this as gospel. It is an educated guess.

sunnsm
2013-Oct-02, 05:32 PM
Not sure if anyone watched this recent webcast. I was planning to watch it soon.
http://www.space.com/19195-night-sky-planets-asteroids-webcasts.html

Jeff Root
2013-Oct-02, 05:54 PM
Shortly after the mass drops below the critical radius,
a hypothetical observer would find that it still is just
ordinary gas.
I think you forgot to say that the observer is located
in the gas cloud.

-- Jeff, in Minneapolis

Strange
2013-Oct-02, 07:54 PM
Are there any good links on what might exist beyond the event horizon since most of the sites dont seem to explain much.

Much as I like Hornblower's description, there are some fun but more speculative ideas, such as: https://en.wikipedia.org/wiki/Fuzzball_%28string_theory%29


To further the discussion, assuming the neutron degeneracy pressure being the greatest for the atomic level, the black hole is basically a soup of sub atomic particles ...where the higgs field is concentrated at the center...causing the immense gravity.

Although the inside of neutron stars is not "just neutrons" it wouldn't be right to think of it as a soup of particles: http://www.astro.umd.edu/~miller/nstar.html#internal (although, Jeff will be pleased to see that spaghetti feature on the menu). Assuming a singularity doesn't actually collapse to infinite density, whatever is there must be denser than nuetron-star stuff.

Also, I may be wrong but I don't think the Higg's field would be any denser because of the density of the matter (and the Higg's field doesn't itself cause gravity).

Hornblower
2013-Oct-03, 12:29 AM
I think you forgot to say that the observer is located
in the gas cloud.

-- Jeff, in Minneapolis

Yes, I meant to say that. Serves me right for writing and posting in haste. This observer would get roasted and spaghettified as the collapse progresses.

sunnsm
2013-Oct-03, 05:36 PM
I like the fuzzball string theory. I've been watching "FRINGE" lately and its quite interesting with the alternate universes that exist.
What would be the temperature inside of a black hole? There must be immense heat trapped due to gravity. I suppose there is a limit to the absolute minimum mass ..e.g. beyond neutron degeneracy pressure when all the subatomic particles are so densely packed..there is no more compression even due to gravity. If this isnt the case then all black holes might have had a similar size. But we do see a black hole and then super massive black holes..


Much as I like Hornblower's description, there are some fun but more speculative ideas, such as: https://en.wikipedia.org/wiki/Fuzzball_%28string_theory%29



Although the inside of neutron stars is not "just neutrons" it wouldn't be right to think of it as a soup of particles: http://www.astro.umd.edu/~miller/nstar.html#internal (although, Jeff will be pleased to see that spaghetti feature on the menu). Assuming a singularity doesn't actually collapse to infinite density, whatever is there must be denser than nuetron-star stuff.

Also, I may be wrong but I don't think the Higg's field would be any denser because of the density of the matter (and the Higg's field doesn't itself cause gravity).

caveman1917
2013-Oct-03, 08:28 PM
Yes, I meant to say that. Serves me right for writing and posting in haste. This observer would get roasted and spaghettified as the collapse progresses.

So black holes would be ready-to-eat pasta machines? Not only turned into spaghetti but cooked as well.

caveman1917
2013-Oct-03, 08:33 PM
Now, if it were to only collapse just so far, and then be a big dense object inside the horizon, you'd expect it to have a strong quadupole and octupole component to its gravitational field, which we should be able to detect in its effect on the accretion disks or any close orbiting companions, but so far it hasn't been observed.

If it's inside a horizon (to be exact an event horizon with a surface gravity associated - there are different sorts of horizons) then the exterior field cannot contain any >2-pole moments, independent of what form it may be inside the horizon - you can't carry the necessary degrees of freedom through the horizon. Or perhaps better stated, it's the horizon itself that determines the exterior field and those degrees of freedom don't exist on an event horizon - at least not long-lived ones, they'll immediately radiate away if you would induce them somehow.

It's of course possible that it just collapses to a big dense object, but then it can't be inside a horizon.

Strange
2013-Oct-03, 08:51 PM
It's of course possible that it just collapses to a big dense object, but then it can't be inside a horizon.

That is interesting. Can you explain that?

caveman1917
2013-Oct-03, 09:11 PM
That is interesting. Can you explain that?

I should have emphasized the word "possible" a bit more. It's not possible in general relativity for an object contained within its own schwarzschild radius to not collapse to a singularity. I was responding to antoniseb's statement in the sense that if such objects are really just big dense objects with detectable multipole moments that they cannot be encompassed in an event horizon - however this still requires new physics.

Essentially the fact that we don't detect multipole moments doesn't say anything about the state of matter inside the event horizon, since it doesn't matter what that state is given that the multipole moments don't "bleed through" the event horizon anyway. So it's perfectly possible (with the word "possible" here taking the most literal meaning - against the predictions of general relativity) that inside the event horizon are big dense objects. However what i think he was alluding to was that if we were to detect multipole moments around black holes that this would point us to new physics about black holes, my point was just that if that were true then these "new objects" would not be enclosed in an event horizon. It's an either/or here: either you have detectable multipole moments or you have an enclosing event horizon, not both.

Cougar
2013-Oct-03, 11:09 PM
I should have emphasized the word "possible" a bit more. It's not possible in general relativity for an object contained within its own schwarzschild radius to not collapse to a singularity.

Well, right, due to the Penrose-Hawking Singularity Theorems. But since these essentially show that GR is incomplete at this point, cannot we then abandon GR and say that it is possible1 that it just collapses to a big -- no, a small dense object that is inside a horizon? (Yes, there would have to be a currently unknown fifth force of nature keeping such object from further collapse. In fact, why isn't such "force" simply Heisenberg Uncertainty?)

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1 Oops, I guess you said that.