PDA

View Full Version : What happens to matter in the singularity of a black hole?



cjackson
2012-Oct-25, 03:58 PM
Does what goes in still exist, or has it been crushed out of existence?

Noclevername
2012-Oct-25, 04:15 PM
Does what goes in still exist, or has it been crushed out of existence?

Since black holes have measureable mass, and that mass increases when matter enters the black hole, it's still there, just maybe not in a form we can recognize.

cosmocrazy
2012-Oct-25, 05:00 PM
The problem with singularities (http://en.wikipedia.org/wiki/Black_hole#Singularity) is that they are a mathematical construct predicted by GR. In physical reality we are not really sure exactly what this may mean. It's difficult for us to imagine all that matter & energy being crushed into a dimensionless point, but that is what is predicted by the math. QM may prove that beyond a certain miniscule size, perhaps below the Planck scale (http://en.wikipedia.org/wiki/Planck_scale), that a different set of laws might apply and singularities just don't exist in the way the GR predicts.

The bottom line is we don't know for sure, there are theories out there about BH's including the likes of Hawking radiation (http://en.wikipedia.org/wiki/Hawking_radiation) which offer explanations about how a BH may eventually lose its mass. But what happens to the mass at the point of the predicted singularity will most likely be solved by QM.

glappkaeft
2012-Oct-25, 05:09 PM
An interersting point is that since the event horizon is "one way" we will never be able to verify any theory when it comes to the inner workings of a black hole, unless we figure out a way to side step the event horizon. In a very real sense there can only be speculation, not science.

Shaula
2012-Oct-25, 05:17 PM
In a very real sense there can only be speculation, not science.
Not really true. If we came up with a theory then it is perfectly possible it could be testable outside a black hole. Kind of like we didn't have to go to the centre of the Sun to find out about fusion.

glappkaeft
2012-Oct-25, 06:42 PM
Not really true. If we came up with a theory then it is perfectly possible it could be testable outside a black hole. Kind of like we didn't have to go to the centre of the Sun to find out about fusion.

But with the sun we can still measure the amount of neutrinos created and the energy output and compare that with what our models say. That part is impossible to do with the inner workings of a black hole, we simply have to trust that our assumptions are correct.

Shaula
2012-Oct-25, 07:14 PM
Theories work everywhere is what I am saying. If we come up with a model for what happens in the BH then the same rules will work everywhere. The odds are we will find some way to test the difference between these rules and the previous set.

Cougar
2012-Oct-25, 07:23 PM
Since black holes have measureable mass, and that mass increases when matter enters the black hole, it's still there, just maybe not in a form we can recognize.

I agree. Whatever goes in still exists because its gravitational effect is still there. But the form of the matter that falls in definitely does not remain in a form we know anything about. We know white dwarfs stop the inward pull of gravity by electron degeneracy pressure. We know that neutron stars stop the inward pull of gravity by the Pauli exclusion principle. Personally, I figure there must be something that finally stops the inward pull of gravity of a black hole, but we just don't know what it is. Again, the infalling matter doesn't just disappear - its gravitational effect is still there.

glappkaeft
2012-Oct-25, 08:35 PM
Theories work everywhere is what I am saying. If we come up with a model for what happens in the BH then the same rules will work everywhere. The odds are we will find some way to test the difference between these rules and the previous set.

But what values should we use in those calculations? This we cannot know. The entire question is however not very relevant to our understanding of the universe since the inner workings off a black hole has no relevance to the rest of the universe, only the interaction between them has an actual effect.

Shaula
2012-Oct-25, 10:18 PM
But what values should we use in those calculations? This we cannot know.
That we might be able to know. Which is the entire point I am making. Sometimes you don't have to look inside the box to know what is in the box.

caveman1917
2012-Oct-26, 05:20 PM
I agree. Whatever goes in still exists because its gravitational effect is still there. But the form of the matter that falls in definitely does not remain in a form we know anything about. We know white dwarfs stop the inward pull of gravity by electron degeneracy pressure. We know that neutron stars stop the inward pull of gravity by the Pauli exclusion principle. Personally, I figure there must be something that finally stops the inward pull of gravity of a black hole, but we just don't know what it is.

The problem with that is that it requires infinite force to keep stuff from being crushed together inside a black hole, this is not the case with your other examples. So while there may be forces that stop contraction such as electron degeneracy pressure, it would be hard to think of an actual infinite force that does so. The problem isn't so much that we don't know which force that might be, but that it needs to be infinite. At least in so far as GR itself works at that level.

cosmocrazy
2012-Oct-29, 08:59 AM
The problem with that is that it requires infinite force to keep stuff from being crushed together inside a black hole, this is not the case with your other examples. So while there may be forces that stop contraction such as electron degeneracy pressure, it would be hard to think of an actual infinite force that does so. The problem isn't so much that we don't know which force that might be, but that it needs to be infinite. At least in so far as GR itself works at that level.

Yes, and since we don't know the answer to this the very fact that Bh's exist tells us that GR may not be the final say on the matter (no pun intended). Or at least GR is incomplete, which seems to be the case when we consider quantum mechanics. So Cougar is quite correct to suggest some sort of mechanism preventing the "stuff" inside a black hole from being crushed out of existence. It may turn out not to be a "force" in the sense of the word but my guess is it will have some thing to do with quantum principles.

One thing I thought about was our perception of time and effects regarding black holes and anything falling into one.

Xibalba
2012-Oct-29, 12:40 PM
I'd like to add a part to the OP question : what happens to the black hole matter when it eventually evaporates? And in which form does it evaporate?

NEOWatcher
2012-Oct-29, 03:14 PM
I'd like to add a part to the OP question : what happens to the black hole matter when it eventually evaporates? And in which form does it evaporate?
Hawking Radiation (http://en.wikipedia.org/wiki/Hawking_radiation).
(That would have been simple enough to find by searching "black hole evaporation")

caveman1917
2012-Oct-29, 11:23 PM
Yes, and since we don't know the answer to this the very fact that Bh's exist tells us that GR may not be the final say on the matter (no pun intended). Or at least GR is incomplete, which seems to be the case when we consider quantum mechanics. So Cougar is quite correct to suggest some sort of mechanism preventing the "stuff" inside a black hole from being crushed out of existence. It may turn out not to be a "force" in the sense of the word but my guess is it will have some thing to do with quantum principles.

One thing I thought about was our perception of time and effects regarding black holes and anything falling into one.

Or quantum mechanics is incomplete and stuff really does get crushed into a singularity. The very fact that BH's exist doesn't tell us either way, IMHO it even points a little more to that since (for a BH) in order to have an event horizon form you have to have a singularity form. The event horizon is a bit like a signpost saying "singularity over there", so if you're going to change the singularity from existing you'll still have to explain how you actually get the signpost saying there's a singularity there without there actually being one. In any case, the question is fully open, and my response was more to what i perceived as Cougar putting unduly too much weight on the "GR must be wrong" side.

Strange
2012-Oct-29, 11:42 PM
An interersting point is that since the event horizon is "one way" we will never be able to verify any theory when it comes to the inner workings of a black hole, unless we figure out a way to side step the event horizon. In a very real sense there can only be speculation, not science.

Apart from also disagreeing with the principle (that we can only know it if we see it) there is also the possibility of naked singularities (without an event horizon). If we could find/create one, then we could, in principle, have direct observation.

cosmocrazy
2012-Oct-30, 11:03 AM
Or quantum mechanics is incomplete and stuff really does get crushed into a singularity. The very fact that BH's exist doesn't tell us either way, IMHO it even points a little more to that since (for a BH) in order to have an event horizon form you have to have a singularity form. The event horizon is a bit like a signpost saying "singularity over there", so if you're going to change the singularity from existing you'll still have to explain how you actually get the signpost saying there's a singularity there without there actually being one. In any case, the question is fully open, and my response was more to what i perceived as Cougar putting unduly too much weight on the "GR must be wrong" side.

Yes I agree in part.

But lets consider what makes a BH black? In simple terms its a region of space where the gravity is so strong the escape velocity is greater than the speed of light.

A singularity is predicted from the math postulated by GR. It predicts that the gravitational force becomes so strong that any matter is crushed in on itself until it becomes a "singularity". But in classical terms a singularity as an inanimate physical object cannot exist.

So there are a few possibilities:- our understanding of physical reality is flawed or incomplete. QM or some other function prevents a singularity from developing. Or there are extra dimensions where the matter can still continue to exist in some form.

Either way, BH's are a reality, there are regions in space where the gravitational effects are so strong the escape velocity is faster than C. Our understanding of them is a long way off complete.

caveman1917
2012-Oct-30, 02:04 PM
Yes I agree in part.

But lets consider what makes a BH black? In simple terms its a region of space where the gravity is so strong the escape velocity is greater than the speed of light.

A singularity is predicted from the math postulated by GR. It predicts that the gravitational force becomes so strong that any matter is crushed in on itself until it becomes a "singularity". But in classical terms a singularity as an inanimate physical object cannot exist.

So there are a few possibilities:- our understanding of physical reality is flawed or incomplete. QM or some other function prevents a singularity from developing. Or there are extra dimensions where the matter can still continue to exist in some form.

Either way, BH's are a reality, there are regions in space where the gravitational effects are so strong the escape velocity is faster than C. Our understanding of them is a long way off complete.

The problem is that what basically happens is that as the matter crosses the event horizon it leaves it gravitational field "behind" on the event horizon so to speak. So in order for the matter to not enter a singularity (and basically removed from the universe) you'd have to have a theory that can seperate matter from its own gravitational field. That's not to say that there cannot be a theory that can do such a thing nicely, but immediately saying that GR must be wrong on that count is jumping to conclusions. True singularities may be pathological, but there is nothing saying that nature cannot have pathologies, no matter how much we dislike them.

cosmocrazy
2012-Oct-30, 05:32 PM
The problem is that what basically happens is that as the matter crosses the event horizon it leaves it gravitational field "behind" on the event horizon so to speak. So in order for the matter to not enter a singularity (and basically removed from the universe) you'd have to have a theory that can seperate matter from its own gravitational field. That's not to say that there cannot be a theory that can do such a thing nicely, but immediately saying that GR must be wrong on that count is jumping to conclusions. True singularities may be pathological, but there is nothing saying that nature cannot have pathologies, no matter how much we dislike them.

Yes agreed.

No one as far as I'm aware has stated that GR is wrong. On the contrary we know GR is correct it's been tested and proven. GR predicts nicely what we observe so it would be madness to dismiss it.