The concept of singularities

[Realitycheck]

Why is it emphasized that the gravity of a black hole is centered in one specific point, rather than as a whole. Gravity usually pulls things towards the surface. As far as I can tell a black hole still must have all of the similar functions of a star, only much greater, which would incinerate ANYTHING that gets too close. It seems to me that a singularity is really just a token point of reference to the center, but that the overwhelming gravity is produced by the mass of the black hole, in its entirety.

[Martin]

Why is it emphasized that the gravity of a black hole is centered in one specific point, rather than as a whole. Gravity usually pulls things towards the surface. As far as I can tell a black hole still must have all of the similar functions of a star, only much greater, which would incinerate ANYTHING that gets too close. It seems to me that a singularity is really just a token point of reference to the center, but that the overwhelming gravity is produced by the mass of the black hole, in its entirety.

 

The best way to imagine the black hole is to think of all the mass being concentrated at the center.

 

the horizon is just a mathematically defined surface from inside of which nothing can escape.

 

the surface has no mass, and it does not attract stuff

and almost all the volume inside the surface is empty vacuum

so it does not attract.

 

what is actually at the center we don't know----Gen Rel is an incomplete theory and blows up there (has a failure called a singularity).

there MIGHT be a material lump of some undiscovered sort right at the center, there might be a meltdown of space and matter where they discover they are aspects of the same thing, there might be a tunnel to somewhere else. We don't KNOW what is right at the center.

 

but according to our best models (Gen Rel itself and some proposed quantized versions) the whole thing acts as if all the mass is concentrated at the exact center

 

does that clarify anything for you? hope it helps

[Realitycheck]

It sounds like an incorrect mathematical conclusion.

 

Unless a black hole is really a completely different animal than a star. If you simply had a body of matter that had grown so massive as to disable the giving off of light, I can see how a singularity would be a more significant focal point. Could it be that black holes are not on fire at all, simply supermassive objects attracting more and more matter? That would not explain jets of hot gas coming out the side, though. Which revives the idea that a black hole is on fire, doing much of the same processes as any other star, just unable to give off light.

 

What does a black hole do with all of the matter that it draws in? That is the 60 million dollar question. Does it fuse it into heavier metals? That seems to be the only logical conclusion.

[foodchain]

It sounds like an incorrect mathematical conclusion.

 

Unless a black hole is really a completely different animal than a star. If you simply had a body of matter that had grown so massive as to disable the giving off of light, I can see how a singularity would be a more significant focal point. Could it be that black holes are not on fire at all, simply supermassive objects attracting more and more matter? That would not explain jets of hot gas coming out the side, though. Which revives the idea that a black hole is on fire, doing much of the same processes as any other star, just unable to give off light.

 

What does a black hole do with all of the matter that it draws in? That is the 60 million dollar question. Does it fuse it into heavier metals? That seems to be the only logical conclusion.

 

My view of a BH was it was a related phenomena like the rest of earthly phenomena. Simply put if you subtract out interactions any object could have what would that object still look like? Then of course you have to deal with a think a timeline then.

 

My rash view was put to rest when I started to learn about what a BH was purely from a scientific point of view. When I actually try to think of such in purely such a manner I get confused as to its position and definition. It seems that they live in a quasi state of being hypothetical and then real. As in experimental evidence can support the existence of such it seems from various studies of the cosmos, I think also various models calculate there existence into the model itself. Yet as for some statement about 100% existence and understanding though, that seems to lack or is not really put forward yet in science as far as I know.

[Realitycheck]

I think a lot of its misinterpretation is due to the fact that it is called a black hole. It's a black mass. If it is hot and runs similar to a star, then it doesn't give off any light because its gravity is too great. If that is the case, then that means that photons never escape, so fusion carries on, but energy is not released. What would happen in this scenario? The photon is recycled and the black hole just keeps getting bigger and bigger. What happens when all of the helium is spent? What could theoretically be done with all of the mostly lightest elements that get sucked into it? If it is at the center of a galaxy, then it would be easy to say that you would have a lot of hydrogen and helium available, according to the distribution of matter in a typical galaxy. The matter that it gobbles up could end up being just a fraction of the total mass of the black hole and, therefore, inconsequential to the processes that run inside of it. However, since giant stars typically don't live very long, this model still needs some editing. With all of the recycled photons thrown into the mix, who knows how this would affect the outcome.

 

Ahh. It would help if I wasn't using stone age theory. I still don't see the relevance of the singularity other than as a reference point to the center of the mass. I don't believe in the disappearance of mass and energy. It just keeps piling up.

[Severian]

I think you are right, agentchange. There is really no need for there to be a singularity in a black hole - all we know is that it is a sufficiently massive object that light can't escape the gravitational pull.

 

And frankly that is all we will ever know unless we go past the event horizon for a look, and even then we wouldn't be able to tell anyone else what we found.

[Mr Skeptic]

I think you are right, agentchange. There is really no need for there to be a singularity in a black hole - all we know is that it is a sufficiently massive object that light can't escape the gravitational pull.

 

And frankly that is all we will ever know unless we go past the event horizon for a look, and even then we wouldn't be able to tell anyone else what we found.

 

But if we found a better model of gravity, that fits in with everything else we know, could we not feel much more confident than we do now that we know what is inside the event horizon? Even if we can never go look to be sure, we might perhaps be able to solve it from outside.

[scalbers]

Yes, to recap one can have a black hole with (at least temporarily) low density material inside that has yet to further collapse. Once it does collapse, it's only an approximation of our current theories that say it would get to infinite density. Hopefully the newer theories will be more thorough and my hunch would be that infinite density will not be reached.

 

If things were slightly different and we had a cyclic universe, we could have billions of years of pleasant living inside a collapsing black hole (i.e. universe). We can even make our own measurements from our environs in the inside of this black hole. Is this too simplistic?

[Realitycheck]

Yes, to recap one can have a black hole with (at least temporarily) low density material inside that has yet to further collapse. Once it does collapse, it's only an approximation of our current theories that say it would get to infinite density. Hopefully the newer theories will be more thorough and my hunch would be that infinite density will not be reached.

 

If things were slightly different and we had a cyclic universe, we could have billions of years of pleasant living inside a collapsing black hole (i.e. universe). We can even make our own measurements from our environs in the inside of this black hole. Is this too simplistic?

 

 

But what does it mean to "collapse"? Is that supposed to mean that all fusion activity ceases and it just becomes a superdense conglomeration of any matter that it can get its hands on? Why not? I just now remembered why it does not have to be hot to give off gas jets.

 

So fusion has halted. The fire is out. There is probably no fire to see even if it could be seen. Why would there need to be a fire? The mass is simply so great that its gravity is phenomenal. Aren't there laws keeping many different atoms from being drawn together in this superdense fashion? Wouldn't some of them repel each other? I guess that at some point the pull of gravity overcomes the repulsion of the two atoms. I wonder if the black hole breaks down the chemical structure of the atom and ceases its life, simply attracting electron, proton, and neutron in a big jumble, like iron shavings on a magnet.

[scalbers]

Hi - I was thinking hypothetically of a collapsing "cyclic" universe where gravity was drawing galaxies together. This is different from the scenario of a stellar sized black hole.

 

Eventually though the collapse would overcome the atomic forces of an atom and the nuclear forces of atomic nuclei. Here is where the unknown physics would come into play to prevent an infinite collapse?

[Martin]

But if we found a better model of gravity, that fits in with everything else we know, could we not feel much more confident than we do now that we know what is inside the event horizon? Even if we can never go look to be sure, we might perhaps be able to solve it from outside.

 

I would agree. Especially if the new model predicted new phenomena outside of BH event horizons, which we could look for. If it predicted phenomena that older established theories did not, and were then looked for and found, that would increase credibility that the model was right also in areas where we can't look. That kind of thing is pretty routine.

 

In the case of black holes, suppose you had a mass equal to that of the earth which you could somehow compress.

To make a black hole you would have to compress it to a sphere less than one centimeter radius

 

so now all the atoms of rock and metal of your earthlike body are compressed down into this little centimeter-size ball.

Question, what could be in there?

 

what new PHASE of space and matter exists at that density?

 

we know about different phases----gas liquid solid---we know about neutron matter that neutron stars are made of (pretty good theory of that). but even neutron matter is much too bulky to be in this little ball. So what is?

 

I think Quantum Gravity is the research area that is aimed at answering that question, since it increasingly is concerned with geometry and matter as aspects of a single fundamental substance----with the fundamental microscopic degrees of freedom from which space and matter emerge as large-scale appearances. QG researchers will either succeed or fail. I hope they succeed. If they do we have a much better idea of what is in the little ball.

 

To some extent one can already say things about what is inside the event horizon just based on classic 1915 GR, if you accept it, which most people do.

For example in the case of a solarmass BH the eventhorizon sphere is some 3 kilometer radius and classic GR works fantastically well where it applies---it is only at very small scales that it blows up. So I am inclined to trust GR for much of those 3 kilometers in towards the center. Down right near the center something new might be going on.

that's just my take. People can vary as to how far they trust classic General Relativity.

 

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for general information:

stellar mass and supermassive black holes are extremely cold unless there is stuff falling in towards

 

when stuff falls or spirals in towards, it is the approaching stuff that heats up, not the hole itself

 

no one has ever detected JETS coming out of a BH -----that is from within the event horizon.

 

processes occuring in the surroundings can, and often do, produce jets. that's fairly routine

 

what I'm telling you is pretty standard mainstream consensus stuff. Personally I never went to a BH to see firsthand.

 

as far as I know no scientist has ever suggested that the observed jets come from the black hole itself

if anybody knows of a technical paper by a professional that claims this please give us a link to it

it would be very surprising and the guy would most likely be labeled as a nut.

[scalbers]

I would suppose that we can describe the interior of the event horizon even better with a galaxy mass black hole (about water density IIRC), or an observable universe mass one (near the critical density).

 

Getting back to the stellar mass black hole, it is interesting that we are where the densest known matter (neutrons) is close to the average density of the black hole. This might help feed into confusion in some discussions. Perhaps as a rhetorical question I'll ask if it is possible for a very massive neutron star to actually be a black hole while still resisting further collapse? If not, then why not? In other words, why is it that any object dense enough to be a black hole always has gravity strong enough to overwhelm the other forces that can repel matter?

[Norman Albers]

What messes me up is the concept of proper time: what happens when by whose clock. I think this is glossed over, though I am not studied up on interior "collapse". One can say "the infalling observer falls through at such-and-such smooth rate" as they perceive it, but certainly near the horizon this may not be meaningful to outside observers. The interior solution I can study in my text is based on a co-moving Robertson-Walker metric. Following is an exchange from a good half-year of discussion with H.Puthoff: In a message dated 10/18/2006 6:32:38 P.M. Central Daylight Time, singularities@clab.net writes:

ALBERS: As time crunches to a crawl even in your dark gray singularity we can say things are not happening at our clocking.

PUTHOFF: Absolutely.

ALBERS: It seems to me immense mistakes have been made here, by people talking about blithely going through a horizon, etc, not that you say this in particular.

PUTHOFF: I agree. Another way of saying it. As the velocity of light seen from our frame drops to zero (approaching an event horizon) we (in our frame) we'll never see a particle go thru the event horizon, since its velocity cannot exceed the local velocity of light "down there," and that has dropped to zero. (For the exponential case, we will never see a particle reach a singularity at the origin.) So even though a rider on a particle would not note anything strange in his frame, he might notice that external clocks seem to be going so fast that eons will go by "out there" while he approaches the event horizon (or singularity for the exponential case) and therefore rightly assumes that the outsider would never see him make the progress he himself considers himself making.

 

Pretty straightforward, in a way!

 

Hal . . . . . . . . . [Albers], here and now: I have several comments to add to the general discussion: The GR solution for a collapsing dustball has it going to zero, although I do not yet know how to relate the interior time coordinate to the exterior. Another observation, don't be overwhelmed by "firey" scenarios. Neutron stars have no intrinsic heat source! Fire is manifest in the matter falling into these intense fields.