Can a Black Hole Not Contain a Singularity?

Fudbucker · 5th July 2012, 08:13 PM

I can't post links, but on a physicists blog (Google "black hole without singularity", it's first hit), he speculates it's possible to achieve a black hole without a singularity.

If it didn't have a singularity, could you get out? Or do all your future paths (not phrasing that right, I'm sure), still terminate in the center of the black hole, even if it doesn't have a singularity?

jasonpatterson · 5th July 2012, 08:30 PM

The post seems like a fishy argument to me. It's been about 15 years since I took courses in this stuff, but as I understand it, once you're in a black hole you're doomed to be crushed. What the blogger is proposing is that there is a force that is able to withstand the gravity involved, but I can't see how that force would be transmitted outward inside a black hole unless it propagates faster than light.

Basically, it doesn't matter how hard quarks push against each other to support the weight of the matter above them, their push can't travel faster than light, and that is what would be required for it to be transmitted outward. Also, any random downward motion in the object would be permanent, since the particles could never climb back out (again, FTL would be required.)

Someone vastly more knowledgeable about this stuff, like sol invictus, may come by and explain exactly why I'm entirely wrong, but that's my take on the thing.

RecoveringYuppy · 5th July 2012, 08:30 PM

This the link you're talking about: http://scienceblogs.com/startswithab...out-a-singula/

He seems to have neglected to consider whether his arrangement of quarks could resist the gravity well they create.

ben m · 5th July 2012, 08:34 PM

Yeah, it's pretty clear that he is wrong. He says "hey, if you make a ball of matter of mass M and nonzero radius R, and you make R small, it's a black hole!" Yes, but while you're assembling this ball it collapses into a singularity. To avoid such a collapse, it would have to have Lorentz-violating mechanical stiffness.

Dan O. · 6th July 2012, 06:10 AM

The singularity is a mathematical concept that comes from the equations we currently use to model the universe. It's possible that there are a diffent set of equations that do an equally good job of modeling the observable universe which avoids the singularity. To support this concept, consider a volume of space filled with a uniform density of matter, say one hydrogen atom per cubic meter. Now make the radius of this volume very very large. At some volume on the order of the size of the known universe this mass is within it's own Swartzchild radius and therefore a black hole. However, observation of our universe suggests that we are not collapsing but rather expanding and creating more space.

Perhaps this is the function that applies to black holes. As they reach the critical mass and begin to collapse, the space within expands even faster. There is still no way to get out of such a black hole as at the periphery, space will appear to be expanding at the speed of light.

Cuddles · 6th July 2012, 08:24 AM

Originally Posted by Fudbucker

I can't post links, but on a physicists blog (Google "black hole without singularity", it's first hit), he speculates it's possible to achieve a black hole without a singularity.

He's right. His particular proposal may not be valid, but it's certainly possible. In fact, I just posted along these lines in another thread. The thing with singularities is that they're a mathematical phenomena that don't necessarily correspond to physical reality. Most of the time when we come across one, it actually means that the theory your using breaks down and can't handle what you're asking it, not that there must be a real physical phenomenon there.

The popular view of a black hole is that you have a point with zero size but finite mass, and therefore infinite density. But we already know that general relativity doesn't give the right answers when you get down to very small scales, which is why one of the big challenges in modern physics is to get a single theory that agrees with both general relativity at large scales and quantum physics at small scales. So sure, GR gives the simplistic idea of a single point of infinite density, but it's in an area we already know we shouldn't expect GR to give us a reliable answer. So there may well not be a singularity, and most theoretical physicists will hope there isn't because dividing by zero is never a nice result to end up with, but we just don't have a theory that tells us what really is going on yet.

As for his particular solution, yeah, it's nonsense. All he's done is claim that you can take the mass of a neutron star and make it out of bottom quarks instead so it's smaller. That's not how physics works. You can't just replace a bunch of particles with different particles and expect everything to behave exactly the same. As ben m says, his quark star (note that this is not an original idea) would have to be stronger than it is possible for anything to ever be. It's essentially the same as if he said "It's possible to get out of a black hole. Imagine something that travels faster than light. See, you can get out!". Sure, if you imagine something that, as far as we know, can't exist, then you can do all kinds of crazy things. That doesn't mean they have anything to do with the real world.

Quote:

If it didn't have a singularity, could you get out?

No. Not being able to get out is pretty much the definition of a black hole. Whatever the details of what happens inside the event horizon, you can never cross back out.

Quote:

Or do all your future paths (not phrasing that right, I'm sure), still terminate in the center of the black hole, even if it doesn't have a singularity?

Even with a singularity you don't necessarily end up in the centre. Not all singularities are simply a point, they can be torus shaped, and probably various other more interesting shapes as well. GR says you'll definitely end up at the singularity though, it just won't necessarily be a single point at the dead centre.

kedo1981 · 6th July 2012, 08:54 AM

I'd bet that there will many varieties of black holes though

Cuddles · 6th July 2012, 09:06 AM

Originally Posted by kedo1981

I'd bet that there will many varieties of black holes though

It depends what you mean by "varieties". There are differences depending on angular momentum, charge and mass, but otherwise a black hole is pretty much just a black hole.

Also a slight correction to my last post - according to general relativity, it can actually be possible to avoid the singularity in a rotating black hole. However, even more so than the singularity itself these are thought to be problems with GR and aren't expected to exist in reality since they cause all kinds of problems with causality.

Belz... · 6th July 2012, 09:11 AM

Originally Posted by Cuddles

It depends what you mean by "varieties".

Strawberry, chocolate, marshmallow...

FireGarden · 6th July 2012, 10:42 AM

Originally Posted by Cuddles

It depends what you mean by "varieties".

Any colour -- so long as it's black.

Agammamon · 7th July 2012, 10:58 PM

Unless I'm mistaken, all the singularity at the center of a black hole is, is a term to describe a point where are understanding of physics breaks down. Right now we don't know what happens at the center of a hole because Relativity doesn't work well to describe phenomenon occuring at such small scales and Quantum theory doesn't work to describe phenomenon at such high energy levels.

As such, as soon as we can figure out and describe what actually happens there, then *no* black holes will have a singularity - they'll have whatever name the new physics gives to the phenomenon.

In any case - the event horizon is simply a function of density and is simply the point where escape velocity is equal to light speed. So a black hole without a "singularity" would still have an event horizon kinda by definition - if it doens't have an event horizon then it's not a hole. And if you've got an event horizon then there's no escaping from the hole once you reach that distance from the hole.

Agammamon · 7th July 2012, 11:03 PM

Originally Posted by jasonpatterson

The post seems like a fishy argument to me. It's been about 15 years since I took courses in this stuff, but as I understand it, once you're in a black hole you're doomed to be crushed. What the blogger is proposing is that there is a force that is able to withstand the gravity involved, but I can't see how that force would be transmitted outward inside a black hole unless it propagates faster than light.

This is one of the newer embellishments to theory - that the stars collapse will be stopped before infinity by an as yet undiscovered mechanism. Not completely crazy as regular stars are stopped from gravitational collapse first by thermal pressure, then electron degeneracy pressure (white dwarfs), then by neutron degeneracy pressure (neutron stars). Currently there's no known mechanism to stop collapse if the stars gravity is greater than it neutron degeneracy pressure and so it collapses into a black hole.

According to these theories, at some point collapsing object will reach the maximum possible energy density for a certain volume of space (the Planck density)where the known laws of gravity cease to be valid. There are competing theories as to what occurs at this point.

sol invictus · 8th July 2012, 05:12 AM

Originally Posted by ben m

Yeah, it's pretty clear that he is wrong. He says "hey, if you make a ball of matter of mass M and nonzero radius R, and you make R small, it's a black hole!" Yes, but while you're assembling this ball it collapses into a singularity. To avoid such a collapse, it would have to have Lorentz-violating mechanical stiffness.

Exactly. He's wrong, because once the radius is below the Schwarzschild radius, no collection of matter (or anything else) can resist the gravitational force.

At least no known matter - new laws of physics could come into play at the would-be singularity and prevent it from forming, but that's not what he's saying.

jasonpatterson · 8th July 2012, 03:28 PM

Originally Posted by Agammamon

According to these theories, at some point collapsing object will reach the maximum possible energy density for a certain volume of space (the Planck density)where the known laws of gravity cease to be valid. There are competing theories as to what occurs at this point.

The guy in the blog post is saying that if we just make a neutron star a bit more dense it would have an event horizon but would not collapse inside that event horizon. He's not proposing some sort of hypothetical collection of chunks of Big-Bang-density material clumped together in the middle of the hole.

It wouldn't surprise me at all if there were some surprises lurking in the bottom of a black hole, but I don't think that infinitely strong conventional matter is going to be that surprise.

Farsight · 9th July 2012, 01:30 AM

Google on Bose-Einstein condensate "black hole" and there's some interesting stuff.

5th July 2012, 08:13 PM	#1
Fudbucker Critical Thinker Join Date: Jul 2012 Posts: 488	Can a Black Hole Not Contain a Singularity? I can't post links, but on a physicists blog (Google "black hole without singularity", it's first hit), he speculates it's possible to achieve a black hole without a singularity. If it didn't have a singularity, could you get out? Or do all your future paths (not phrasing that right, I'm sure), still terminate in the center of the black hole, even if it doesn't have a singularity?

5th July 2012, 08:30 PM	#2
jasonpatterson Philanthropic Misanthrope Join Date: Apr 2009 Location: Space, The Final Frontier Posts: 2,180	The post seems like a fishy argument to me. It's been about 15 years since I took courses in this stuff, but as I understand it, once you're in a black hole you're doomed to be crushed. What the blogger is proposing is that there is a force that is able to withstand the gravity involved, but I can't see how that force would be transmitted outward inside a black hole unless it propagates faster than light. Basically, it doesn't matter how hard quarks push against each other to support the weight of the matter above them, their push can't travel faster than light, and that is what would be required for it to be transmitted outward. Also, any random downward motion in the object would be permanent, since the particles could never climb back out (again, FTL would be required.) Someone vastly more knowledgeable about this stuff, like sol invictus, may come by and explain exactly why I'm entirely wrong, but that's my take on the thing.
	__________________ Sandra's seen a leprechaun, Eddie touched a troll, Laurie danced with witches once, Charlie found some goblins' gold. Donald heard a mermaid sing, Susie spied an elf, But all the magic I have known I've had to make myself. - Shel Silverstein

5th July 2012, 08:30 PM	#3
RecoveringYuppy Illuminator Join Date: Nov 2006 Location: Tucson, AZ Posts: 3,846	This the link you're talking about: http://scienceblogs.com/startswithab...out-a-singula/ He seems to have neglected to consider whether his arrangement of quarks could resist the gravity well they create.
	__________________ REJ (Robert E Jones) posting anonymously under my real name for 30 years. Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.

5th July 2012, 08:34 PM	#4
ben m Illuminator Join Date: Jul 2006 Posts: 4,639	Yeah, it's pretty clear that he is wrong. He says "hey, if you make a ball of matter of mass M and nonzero radius R, and you make R small, it's a black hole!" Yes, but while you're assembling this ball it collapses into a singularity. To avoid such a collapse, it would have to have Lorentz-violating mechanical stiffness.
ben m Illuminator Join Date: Jul 2006 Posts: 4,639

6th July 2012, 06:10 AM	#5
Dan O. Philosopher Join Date: Feb 2007 Posts: 8,715	The singularity is a mathematical concept that comes from the equations we currently use to model the universe. It's possible that there are a diffent set of equations that do an equally good job of modeling the observable universe which avoids the singularity. To support this concept, consider a volume of space filled with a uniform density of matter, say one hydrogen atom per cubic meter. Now make the radius of this volume very very large. At some volume on the order of the size of the known universe this mass is within it's own Swartzchild radius and therefore a black hole. However, observation of our universe suggests that we are not collapsing but rather expanding and creating more space. Perhaps this is the function that applies to black holes. As they reach the critical mass and begin to collapse, the space within expands even faster. There is still no way to get out of such a black hole as at the periphery, space will appear to be expanding at the speed of light.
Dan O. Philosopher Join Date: Feb 2007 Posts: 8,715	__________________ Permanent solution to national fiscal problems: Collect UNDIEs from dead rich people. (link)

6th July 2012, 08:24 AM	#6
Cuddles Decoy Moderator Join Date: Jul 2006 Location: A magical land full of pink fluffy sheeps and bunnies Posts: 16,566	Originally Posted by Fudbucker I can't post links, but on a physicists blog (Google "black hole without singularity", it's first hit), he speculates it's possible to achieve a black hole without a singularity. He's right. His particular proposal may not be valid, but it's certainly possible. In fact, I just posted along these lines in another thread. The thing with singularities is that they're a mathematical phenomena that don't necessarily correspond to physical reality. Most of the time when we come across one, it actually means that the theory your using breaks down and can't handle what you're asking it, not that there must be a real physical phenomenon there. The popular view of a black hole is that you have a point with zero size but finite mass, and therefore infinite density. But we already know that general relativity doesn't give the right answers when you get down to very small scales, which is why one of the big challenges in modern physics is to get a single theory that agrees with both general relativity at large scales and quantum physics at small scales. So sure, GR gives the simplistic idea of a single point of infinite density, but it's in an area we already know we shouldn't expect GR to give us a reliable answer. So there may well not be a singularity, and most theoretical physicists will hope there isn't because dividing by zero is never a nice result to end up with, but we just don't have a theory that tells us what really is going on yet. As for his particular solution, yeah, it's nonsense. All he's done is claim that you can take the mass of a neutron star and make it out of bottom quarks instead so it's smaller. That's not how physics works. You can't just replace a bunch of particles with different particles and expect everything to behave exactly the same. As ben m says, his quark star (note that this is not an original idea) would have to be stronger than it is possible for anything to ever be. It's essentially the same as if he said "It's possible to get out of a black hole. Imagine something that travels faster than light. See, you can get out!". Sure, if you imagine something that, as far as we know, can't exist, then you can do all kinds of crazy things. That doesn't mean they have anything to do with the real world. Quote: If it didn't have a singularity, could you get out? No. Not being able to get out is pretty much the definition of a black hole. Whatever the details of what happens inside the event horizon, you can never cross back out. Quote: Or do all your future paths (not phrasing that right, I'm sure), still terminate in the center of the black hole, even if it doesn't have a singularity? Even with a singularity you don't necessarily end up in the centre. Not all singularities are simply a point, they can be torus shaped, and probably various other more interesting shapes as well. GR says you'll definitely end up at the singularity though, it just won't necessarily be a single point at the dead centre.
	__________________ I am not a little teapot.

6th July 2012, 08:54 AM	#7
kedo1981 Master Poster Join Date: Aug 2001 Location: ohio Posts: 2,078	I'd bet that there will many varieties of black holes though
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6th July 2012, 09:06 AM	#8
Cuddles Decoy Moderator Join Date: Jul 2006 Location: A magical land full of pink fluffy sheeps and bunnies Posts: 16,566	Originally Posted by kedo1981 I'd bet that there will many varieties of black holes though It depends what you mean by "varieties". There are differences depending on angular momentum, charge and mass, but otherwise a black hole is pretty much just a black hole. Also a slight correction to my last post - according to general relativity, it can actually be possible to avoid the singularity in a rotating black hole. However, even more so than the singularity itself these are thought to be problems with GR and aren't expected to exist in reality since they cause all kinds of problems with causality.
	__________________ I am not a little teapot.

6th July 2012, 09:11 AM	#9
Belz... Fiend God Join Date: Oct 2005 Location: In the details... Posts: 28,444	Originally Posted by Cuddles It depends what you mean by "varieties". Strawberry, chocolate, marshmallow...
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6th July 2012, 10:42 AM	#10
FireGarden Philosopher Join Date: Aug 2002 Location: Spannungsbogen -- without a visa Posts: 5,043	Originally Posted by Cuddles It depends what you mean by "varieties". Any colour -- so long as it's black.
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7th July 2012, 10:58 PM	#11
Agammamon Graduate Poster Join Date: Jan 2003 Posts: 1,385	Unless I'm mistaken, all the singularity at the center of a black hole is, is a term to describe a point where are understanding of physics breaks down. Right now we don't know what happens at the center of a hole because Relativity doesn't work well to describe phenomenon occuring at such small scales and Quantum theory doesn't work to describe phenomenon at such high energy levels. As such, as soon as we can figure out and describe what actually happens there, then no black holes will have a singularity - they'll have whatever name the new physics gives to the phenomenon. In any case - the event horizon is simply a function of density and is simply the point where escape velocity is equal to light speed. So a black hole without a "singularity" would still have an event horizon kinda by definition - if it doens't have an event horizon then it's not a hole. And if you've got an event horizon then there's no escaping from the hole once you reach that distance from the hole.
	__________________ It will be a great day when the US Air Force has all the bombs it needs and the NEA has to hold a bake sale in order to pay its lobbyists.

7th July 2012, 11:03 PM	#12
Agammamon Graduate Poster Join Date: Jan 2003 Posts: 1,385	Originally Posted by jasonpatterson The post seems like a fishy argument to me. It's been about 15 years since I took courses in this stuff, but as I understand it, once you're in a black hole you're doomed to be crushed. What the blogger is proposing is that there is a force that is able to withstand the gravity involved, but I can't see how that force would be transmitted outward inside a black hole unless it propagates faster than light. This is one of the newer embellishments to theory - that the stars collapse will be stopped before infinity by an as yet undiscovered mechanism. Not completely crazy as regular stars are stopped from gravitational collapse first by thermal pressure, then electron degeneracy pressure (white dwarfs), then by neutron degeneracy pressure (neutron stars). Currently there's no known mechanism to stop collapse if the stars gravity is greater than it neutron degeneracy pressure and so it collapses into a black hole. According to these theories, at some point collapsing object will reach the maximum possible energy density for a certain volume of space (the Planck density)where the known laws of gravity cease to be valid. There are competing theories as to what occurs at this point.
	__________________ It will be a great day when the US Air Force has all the bombs it needs and the NEA has to hold a bake sale in order to pay its lobbyists. Last edited by Agammamon; 7th July 2012 at 11:05 PM.

8th July 2012, 05:12 AM	#13
sol invictus Philosopher Join Date: Oct 2007 Location: Nova Roma Posts: 8,417	Originally Posted by ben m Yeah, it's pretty clear that he is wrong. He says "hey, if you make a ball of matter of mass M and nonzero radius R, and you make R small, it's a black hole!" Yes, but while you're assembling this ball it collapses into a singularity. To avoid such a collapse, it would have to have Lorentz-violating mechanical stiffness. Exactly. He's wrong, because once the radius is below the Schwarzschild radius, no collection of matter (or anything else) can resist the gravitational force. At least no known matter - new laws of physics could come into play at the would-be singularity and prevent it from forming, but that's not what he's saying.

8th July 2012, 03:28 PM	#14
jasonpatterson Philanthropic Misanthrope Join Date: Apr 2009 Location: Space, The Final Frontier Posts: 2,180	Originally Posted by Agammamon According to these theories, at some point collapsing object will reach the maximum possible energy density for a certain volume of space (the Planck density)where the known laws of gravity cease to be valid. There are competing theories as to what occurs at this point. The guy in the blog post is saying that if we just make a neutron star a bit more dense it would have an event horizon but would not collapse inside that event horizon. He's not proposing some sort of hypothetical collection of chunks of Big-Bang-density material clumped together in the middle of the hole. It wouldn't surprise me at all if there were some surprises lurking in the bottom of a black hole, but I don't think that infinitely strong conventional matter is going to be that surprise.
	__________________ Sandra's seen a leprechaun, Eddie touched a troll, Laurie danced with witches once, Charlie found some goblins' gold. Donald heard a mermaid sing, Susie spied an elf, But all the magic I have known I've had to make myself. - Shel Silverstein

9th July 2012, 01:30 AM	#15
Farsight Graduate Poster Join Date: Mar 2008 Location: Poole, UK Posts: 1,934	Google on Bose-Einstein condensate "black hole" and there's some interesting stuff.