Uncovering the Mysteries of Black Holes

[Frame Dragger]

In other words, there really aren't any new black holes that have formed in this incarnation of the Universe

Large Gamma Ray Bursts would argue otherwise for one. Again, you could take a styrofoam cup, and with an ungodly amount of pressure it could be compressed beyond its Shwarzschild Radiius at which point Gravity would dominate all other forces... create an event horizon, and whatever the hell is really beyond such a horizon.

If DaveC went on, he could tell you that the photons would come arbitrarily slowly, and finally not at all. The point at which photons cease to return IS the Event Horizon. Measurements of bodies believed to be rapidly rotating black holes seem to support the notion of an event horizon, and Black Holes.

Take Stephen Hawking's analogy of time as a globe. At the north pole is the big bang, which expands in space-time either in an expanding cone or a sphere that reaches maximum size and returns to collapse at the opposite pole. In that scheme, you can imagine that if you cut the universe into time and space -like slices, different slices would also represent different physical states of the BH. However, as observers outisde the Event Horizon, what is inside can only ever be of academic interest, or of interest to an unimaginaby advanced society.

 

[Frame Dragger]

Yes it does, pretty much by definition.

You have a horizon out of which light cannot escape. You have mass inside. Regardless of what's actually happening inside, that's a black hole.

Now, the issue is whether you have a singularity. Well, you do. Same way.

When we project known physics (GR) into the space inside a BH, our understanding tells us there's no force that can withstand gravitational collapse. But: it doesn't matter what actually happens, what matters is that our current physics is unable to describe it. That is the definition of singularity.

I vote for "green slime and lost socks" myself. :lol:

 

[DaveC426913]

Again, you could take a styrofoam cup, and with an ungodly amount of pressure it could be compressed beyond its Shwarzschild Radiius at which point Gravity would dominate all other forces... create an event horizon, and whatever the hell is really beyond such a horizon.

It seems he's not questioning if the physics say a BH can form; in fact, he's not even refuting that they do exist. He's simply saying that, since BHs appear (to an outside observer) to take forever to form, that none have formed since the BB. He seems unable to get past this block.

I am eager to see him deduce that, since we cannot see them from Earth, stars beyond our observable universe never actually formed.

 

[Frame Dragger]

It seems he's not questioning if the physics say a BH can form; in fact, he's not even refuting that they do exist. He's simply saying that, since BHs appear (to an outside observer) to take forever to form, that none have formed since the BB. He seems unable to get past this block.

I am eager to see him deduce that, since we cannot see them from Earth, stars beyond our observable universe never actually formed.

Maybe he's a solopist? ;)

 

[Frame Dragger]

In other words, there really aren't any new black holes that have formed in this incarnation of the Universe

Hmmm... I was just re-reading this a few times to fully soak it all in. If the BHs take an infinite time to form according to your (wrong) view... then they wouldn't exist. New, or old in ANY universe with a history like ours. You also seem to be making a "big crunch/big bang" cycle of universal history, which seems to be unlikely given the observed cosmological constant. In essence, you're wrong in every possible and meaningful way you can be.

I'm not saying any of this to taunt or tease you. I'm trying to get through to you. You have a grasp on some interesting concepts, but only in piecemeal. You need to open your mind a bit and go back to the basics of General and Special Relativity. I think when you do, the answers to your questions about the formation and evolution (including the DEATH/evaporation) of a black hole.

This is one of those entities that emerged from the math FIRST, and then observations have shown bodies which lookk and behave a LOT like Black Holes. Something superdense and massive is out there, in the center of our galaxy, and many others... and other BHs are all over the place. However... just what that is, whether objects can be crushed out of existence (Hawking view) and then radiated through a quantum process thus breaking Unitarity is open to a lot of questions.

However, based on the rotation of some of these bodies and their mass, whatever is out there is VERY like a black hole, which is why it's so crucial to see how Event Horizons (sonic in this case) behave in the lab. Do they radiate phonons (photons for Grav)? Is information encoded in the event horizon, or is it lost? Is there some kind of superdense remnant that defies the Planck Scale and Beckenstein Bound? The answer is: This is what string theorists, loop quantum gravity fans, GR theorists, and everyone else wants to know.

The entire point of studying black holes is that they represent an extreme case where gravity overwhelms the other 3 forces (EM, Strong Nuclear, Weak Nuclear) and the "edges" of GR and SQM can be studied.

 

[Dmitry67]

wofsy, in GR you can not assume the 'global time'.
Even more, in highly curved spacetime there are many different ways to 'map' events to each other. Depending on the method, the answer can be positive or negative.
Don't assume that there is a global time flow in the Universe

 

[skeptic2]

From post #16 referring to matter draining from a black hole through a wormhole.

Oddly enough we wouldn't see a mass-loss. The external field is "frozen" at the value set by infalling matter. In fact wormholes would exhibit a similar mass change with respect to inflow and outflow through them. A net negative flow would cause a wormhole to become repulsive.

But I wasn't referring to regular wormholes. Some theories - Lee Smolin's for example - have black holes producing "baby universes" from their mass.

Graal, this is an interesting concept that I wish you would expand upon. Does the theory suggest that spacetime becomes plastic at the horizon and remains permanently deformed even in the absence of matter or that matter, as it passes through the horizon, leaves its gravitational and electrical fields behind?

 

[Frame Dragger]

From post #16 referring to matter draining from a black hole through a wormhole.



Graal, this is an interesting concept that I wish you would expand upon. Does the theory suggest that spacetime becomes plastic at the horizon and remains permanently deformed even in the absence of matter or that matter, as it passes through the horizon, leaves its gravitational and electrical fields behind?

Mass and Charge are added to a black hole when matter (or matter with charge) is added. In fact, Mass, Charge, and Angular Momentum are it for what you get from a Black Hole. That.. is the problem! lol

You could in theory cause a nonrotating uncharged BH to being to rotate, gain a charge, and increase its mass by dropping in charged matter with angular momentum.

 

[skeptic2]

Since it is generally accepted that a black hole is empty except for the singularity, one would suppose that mass, charge and angular momentum would be properties of the singularity. How can properties of the singularity influence anything outside the event horizon? The short answer is they can't. This is why I suspect the hypothesis suggests that these properties are frozen into spacetime at the horizon as matter passes through. I am looking for a more detailed explanation of the basis for that assumption.

 

[wofsy]

wofsy, in GR you can not assume the 'global time'.
Even more, in highly curved spacetime there are many different ways to 'map' events to each other. Depending on the method, the answer can be positive or negative.
Don't assume that there is a global time flow in the Universe

Thanks Dmitry I understand that there is no global time. I am just asking the question from our particular frame of reference..

 

[Frame Dragger]

Since it is generally accepted that a black hole is empty except for the singularity...

Really? This isn't in line with many theories, including those predicted by virtually all QM interpretations. I would be interested to know why you believe this.

As for these properties freezing at the event horizon, who knows? HR takes place at the EH, and is separated from the inside of the BH. If the Holographic Principle is correct, then the EH contains the otherwise 'lost' Information. That said, it doesn't imply that time stop at the EH, which would of course be Relative. Whether the EH is a boundary condition or just a point of no return, it's still a brick wall for physics and the beginning of either unified GR/QM, or pure metaphysics.

 

[wofsy]

Hmmm... I was just re-reading this a few times to fully soak it all in. If the BHs take an infinite time to form according to your (wrong) view... then they wouldn't exist. New, or old in ANY universe with a history like ours. You also seem to be making a "big crunch/big bang" cycle of universal history, which seems to be unlikely given the observed cosmological constant. In essence, you're wrong in every possible and meaningful way you can be.

I'm not saying any of this to taunt or tease you. I'm trying to get through to you. You have a grasp on some interesting concepts, but only in piecemeal. You need to open your mind a bit and go back to the basics of General and Special Relativity. I think when you do, the answers to your questions about the formation and evolution (including the DEATH/evaporation) of a black hole.

This is one of those entities that emerged from the math FIRST, and then observations have shown bodies which lookk and behave a LOT like Black Holes. Something superdense and massive is out there, in the center of our galaxy, and many others... and other BHs are all over the place. However... just what that is, whether objects can be crushed out of existence (Hawking view) and then radiated through a quantum process thus breaking Unitarity is open to a lot of questions.

However, based on the rotation of some of these bodies and their mass, whatever is out there is VERY like a black hole, which is why it's so crucial to see how Event Horizons (sonic in this case) behave in the lab. Do they radiate phonons (photons for Grav)? Is information encoded in the event horizon, or is it lost? Is there some kind of superdense remnant that defies the Planck Scale and Beckenstein Bound? The answer is: This is what string theorists, loop quantum gravity fans, GR theorists, and everyone else wants to know.

The entire point of studying black holes is that they represent an extreme case where gravity overwhelms the other 3 forces (EM, Strong Nuclear, Weak Nuclear) and the "edges" of GR and SQM can be studied.

thanks. this was helpful. although I still don't see the answer I will wait until I learn more about GR.

I was just just imagining an astronomer on Earth watching a star collapse and wondered when it would be that he saw the resulting black hole if the observed time in the star slow to zero in a infinite amount of his time. And if it isn't quite right to say that he could observe the hole he would still be able to predict that it would never form in finite time - thus never completely form.

The question is not whether there are black holes - but when in his frame of reference, did they form?

 

[George Jones]

Someone once said to me that as a BH forms an outside observer will see the clocks in the forming hole slow down continually towards zero. So it would thus take an infinite amount of time on the outside observer's clock for the hole to form.

For an observer who follows a particular worldline.

If this is true how can a BH ever be observed? Put another way, how can a BH exist unless it already existed at the creation of the Universe?

By following a different worldline, i.e., you could choose to cross the event horizon. You are free to choose to see or not to see the black hole region, just as in SR you are free to follow a wordline from which you can observe all of spacetime, or to follow a worldline for which parts of spacetime are always observationally inaccessible to you, even if you live to an infinite age.

Just put enough mass together in one place; the collapse of a big star should do it. Not seeing past the horizon has nothing to do with whether it exists or not. Horizons are limits of visibility or influence; not limits of existence.

And if the volume of space is large, the density of matter needed can be arbitrarily small, smaller even than the density of our atmosphere.

i understand more than you think. think about my question.
the presence of an event horizon does not mean that there is a black hole.

The definition of the black hole region of an asymptotically flat spacetime is the region of spacetime from which it is impossible to escape to future null infinity. An event horizon is the boundary of this region.

Within ten years, black holes should be "observed" as black disks with certain properties.

[edit]Back to my day job.[/edit]

 

[skeptic2]

Really? This isn't in line with many theories, including those predicted by virtually all QM interpretations. I would be interested to know why you believe this.

Please excuse my ignorance. What is the interior of the event horizon filled with?

As for these properties freezing at the event horizon, who knows? HR takes place at the EH, and is separated from the inside of the BH. If the Holographic Principle is correct, then the EH contains the otherwise 'lost' Information. That said, it doesn't imply that time stop at the EH, which would of course be Relative. Whether the EH is a boundary condition or just a point of no return, it's still a brick wall for physics and the beginning of either unified GR/QM, or pure metaphysics.

Are you saying that the encoded information at the horizon creates the gravitational, electrical and angular momentum properties felt outside the EH?