[jeffreyH (OP)]

To collapse below the Schwarzchild radius some of the mass is already contained within this volume. Mass outside this region, when collapsing inwards, will approach the radius with escape velocity increasing proportionally. Has anyone tried working this through during the collapse event to calculate the effects on gravity as the process evolves?

[Pmb]

Is then gravitation expressed at the event horizon of the black hole as a result of the in falling matter. If so then what part would the original mass play? Or is this looking at it wrong?

I'm sorry but I don't understand this question. Can you rephrase it for me please?

[Pmb]

To collapse below the Schwarzchild radius some of the mass is already contained within this volume.

As observed from outside the event horizon, nothing can pass through the event horizon and go inside.

Mass outside this region, when collapsing inwards, will approach the radius with escape velocity increasing proportionally.

Actually, as matter approaches the event horizon it slows down and comes to a stop at the event horison and never crosses it.

Has anyone tried working this through during the collapse event to calculate the effects on gravity as the process evolves?

I don't understand what you mean by "the effects on gravity." Can you clarify this for me please?

[jeffreyH (OP)]

To collapse below the Schwarzchild radius some of the mass is already contained within this volume.

As observed from outside the event horizon, nothing can pass through the event horizon and go inside.

Mass outside this region, when collapsing inwards, will approach the radius with escape velocity increasing proportionally.

Actually, as matter approaches the event horizon it slows down and comes to a stop at the event horison and never crosses it.

Has anyone tried working this through during the collapse event to calculate the effects on gravity as the process evolves?

I don't understand what you mean by "the effects on gravity." Can you clarify this for me please?

The effects on gravitational field strength. Does it increase or decrease overall? This is assuming a Kerr black hole.

[jeffreyH (OP)]

Is then gravitation expressed at the event horizon of the black hole as a result of the in falling matter. If so then what part would the original mass play? Or is this looking at it wrong?

I'm sorry but I don't understand this question. Can you rephrase it for me please?

I would forget this one. I need to know what I mean myself first. :-)

[Pmb]

The effects on gravitational field strength. Does it increase or decrease overall? This is assuming a Kerr black hole.

Not sure. I'm not an expert on black holes so I'd rather remain silent on questions requiring great detail like this.

[Kryptid]

Interesting...can the effect of added pressure increase gravity significantly? Does that make the "replace the Sun with a black hole" analogy I mentioned earlier wrong then?

No. That remains correct.

Each case must really be analzed individually. It's dangerous to form general conclusions. Let me give you an example; you've heard of cosmic strings, right? A straight cosmic string has an enormous linear mass density. It's extremely thin, less than the width of an atom but never ends in an open universe. It has an equally large tension too. Tesion is like pressure but is negative. They contribute equally in the case of the cosmic string. The end effect is that you could be standing right next to a cosmic string and not know it from its gravitational field. The only gravitational effect a cosmic string has is to change tghe topology of the surrounding space from planar to conical. Amazing stuff, isn't it?

A vacuum domain wall is another example. In this case the wall is a two dimensional object rather than a one dimensional object like the string. The tension contributes twice as much so the wall has a replusive gravitational field. Interesting thing about the vacuum domain wall is that the gravitaitonal field it generates has zero spacetime curvature.

In three dimensions there is even more repulsion and this is how the accelerating expansion of the universe works.

On the other hand the effective active gravitational mass density of radiation is that the (positive) contribution of the raditation pressure contributes a significant amount to the active-grav-mass.

Forgive me for taking this a bit off topic, but I find these conclusions rather fascinating. I've heard of domain walls before, but never that they were gravitationally-repulsive. If only we could prove their existence and duplicate them on a tiny, controlled scale. Then antigravity machines may prove plausible. Not that I expect this to happen any time soon.

You sound fairly confident about the gravitational repulsion that causes the Universe's expansion. Yet I've never heard of that explanation before. It does sound like a nice model, as it doesn't invoke a mysterious "dark energy" to explain it. Is this a mainstream theory?

[Pmb]

Forgive me for taking this a bit off topic, but I find these conclusions rather fascinating. I've heard of domain walls before, but never that they were gravitationally-repulsive.
 If only we could prove their existence and duplicate them on a tiny, controlled scale.

If we could create that kind of matter and control it then we could try it. That's way off in the future if you ask me though.

You sound fairly confident about the gravitational repulsion that causes the Universe's expansion.

That is what the entire cosmology community believes. Who am I to differ?

Yet I've never heard of that explanation before. It does sound like a nice model, as it doesn't invoke a mysterious "dark energy" to explain it. Is this a mainstream theory?

Yes. Please understand that the term "dark energy" is simply the name given to the cause of gravitational repulsion. See
http://news.nationalgeographic.com/news/2012/02/120215-dark-energy-antimatter-physics-alternate-space-science/# - Is Dark Energy Really "Repulsive Gravity"?

See also http://en.wikipedia.org/wiki/Dark_energy

This accelerating expansion effect is sometimes labeled "gravitational repulsion", which is a colorful but possibly confusing expression. In fact a negative pressure does not influence the gravitational interaction between masses—which remains attractive—but rather alters the overall evolution of the universe at the cosmological scale, typically resulting in the accelerating expansion of the universe despite the attraction among the masses present in the universe.

[jeffreyH (OP)]

I have often thought that collapsing systems such as black holes and neutron stars can only exist in an expanding system. If the system were collapsing we should see white holes. This is why white holes are unstable but in the collapsing system it would be black holes that were unstable.

[yor_on]

That would make traveling the astronomical 'void' a very dangerous experience me thinks when matter and antimatter meet you get radiation, does you not? Shouldn't that be measurable, or is the assumption that this only took place in some beginning never more happening? also it makes me think of a  twisted 'mirror universe' in where half of its existence finds the other half non-existing, as non measurable. A very weird concept which reminds me of Bakers SF (think it was him?) depicting a ultimate 'war of resources',  between beings of matter and anti matter, arranging the universe to a anti matter state, ultimately making it inhabitable for us of matter.
==

It is a nice idea though in the sense of explaining why we then could have a equal amount of anti matter matter, possibly? From a big Bang without those annihilating each other at the moment they emerge. But if they exist in equal proportions, and they should if they do not 'naturally meet', due to gravity/anti gravity, what exactly would make the universe expand, and accelerate? Reminds me of my old idea (my joke actually) about 'virtual particles', although I doubt that one too, it's just too simplistic. You can as easily argue that it then need a equal amount of virtual 'photons' of mass to come into existence, and then you should have no expansion I think, neither a acceleration.

I think geometry holds the answer myself, with probably more degrees of freedom, or less? Depending on how you look at it. It all depends on if we got that one right I guess? I can alternatively imagine another sort of topology, solely defined from local measurements, in where the real question becomes what allows a 'local point' to in any way being able to measure another point (connect to). That universe does have a topology (dimensions) defined by our measurements, but its consistency is ultimately a local experience. And ultimately a question of pure logic.

As if what define a universes geometry is a question of some principle allowing local points to measure on other points, a 'point like' universe if one like Such a universe, should allow for entanglements easily as our definitions of distance, and motion, would need to be retranslated to fit such a concept.

[Pmb]

I have often thought that collapsing systems such as black holes and neutron stars can only exist in an expanding system.

I can't see why? What leads you to believe this?

If the system were collapsing we should see white holes.

What system are you referring to and why would you expect to see white holes. There's no evidence that such objects even exist.

I This is why white holes are unstable ...

Do you have a source for this assertion? I can't imagine why it would be so.

Jeff - You seem to enjoy black holes. You should consider reading Exploring Black Holes - 2nd Ed by Taylor, Wheeler and Bertschinger at http://exploringblackholes.com/

I think you'd also get a great deal of satisfaction reading Black Holes and Time Warps - Einstein's Outrageous Legacy by Kip Thorne. Thorne is the worlds leading theorist on black holes.

[jeffreyH (OP)]

I have often thought that collapsing systems such as black holes and neutron stars can only exist in an expanding system.

I can't see why? What leads you to believe this?

If the system were collapsing we should see white holes.

What system are you referring to and why would you expect to see white holes. There's no evidence that such objects even exist.

I This is why white holes are unstable ...

Do you have a source for this assertion? I can't imagine why it would be so.

Jeff - You seem to enjoy black holes. You should consider reading Exploring Black Holes - 2nd Ed by Taylor, Wheeler and Bertschinger at http://exploringblackholes.com/

I think you'd also get a great deal of satisfaction reading Black Holes and Time Warps - Einstein's Outrageous Legacy by Kip Thorne. Thorne is the worlds leading theorist on black holes.

Sorry this is getting to be a personal theory and this topic isn't really the place for that. I will get the references you suggest and may pursue this further.

[Pmb]

No apology necessary. Let me know when you get the reference in a PM please. I’m curious as to what that’s all about. Thanks.

[jeffreyH (OP)]

I was wondering if the Pauli exclusion principle could be one of the principle mechanisms of gravitational interaction. Note I didn't say gravitational generation, because I still doubt that gravitation comes out of matter. The spin combinations may be a clue.

[Pmb]

I was wondering if the Pauli exclusion principle could be one of the principle mechanisms of gravitational interaction.

Yes. In some cases it plays a role. Neutron stars is a perfect example. See http://en.wikipedia.org/wiki/Pauli_exclusion_principle

Astronomy provides a spectacular demonstration of the effect of the Pauli principle, in the form of white dwarf and neutron stars. In both types of body, atomic structure is disrupted by large gravitational forces, leaving the constituents supported by "degeneracy pressure" alone. This exotic form of matter is known as degenerate matter. In white dwarfs atoms are held apart by electron degeneracy pressure. In neutron stars, subject to even stronger gravitational forces, electrons have merged with protons to form neutrons. Neutrons are capable of producing an even higher degeneracy pressure, albeit over a shorter range. This can stabilize neutron stars from further collapse, but at a smaller size and higher density than a white dwarf. Neutrons are the most "rigid" objects known; their Young modulus (or more accurately, bulk modulus) is 20 orders of magnitude larger than that of diamond. However, even this enormous rigidity can be overcome by the gravitational field of a massive star or by the pressure of a supernova, leading to the formation of a black hole.

Thanks for asking this question. I learned asomething today, i.e. a new term "degenerate matter" - an exotic form of matter!

[jeffreyH (OP)]

In my mental musings over the past few days it appears to me that the most crucial component of e=mc^2 is actually the distance c. This distance bears a direct relationship to Planck scales which is critical to the understanding of forces in the universe.

We can rewrite this as e=m(Planck length)^2.

[Kryptid]

In my mental musings over the past few days it appears to me that the most crucial component of e=mc^2 is actually the distance c. This distance bears a direct relationship to Planck scales which is critical to the understanding of forces in the universe.

We can rewrite this as e=m(Planck length)^2.

That "c" is the speed of light, which is not a distance.

[jeffreyH (OP)]

In my mental musings over the past few days it appears to me that the most crucial component of e=mc^2 is actually the distance c. This distance bears a direct relationship to Planck scales which is critical to the understanding of forces in the universe.

We can rewrite this as e=m(Planck length)^2.

That "c" is the speed of light, which is not a distance.

If you do not believe this is a distance then e=mc^2 must be telling us how fast energy is travelling rather than how much of it relates to the mass. To expand on this c is important in the relationship between energy and inertia. When viewed that way yes c is a speed.

[webplodder]

If I throw a ball, presumably the mass of the ball will increase since I have imparted some kinetic energy to it but would I lose energy? My arm would be travelling at the same speed as the ball before I let it go so the ball and arm would experience the same kinetic energy. However, I must have used up some energy in the process of throwing the ball so what is the net result of all this?

[yor_on]

Mostly transformed into heat, as I understands it, the 'thing' missing from your muscles etc, costing 'energy' for you. But if you mean that there seems to be something weird about the concept that everything just transforms, and nothing ever is lost, the universe being in a equilibrium I agree Just turn it around and ask yourself why accelerations and life exist, if there just is a equilibrium? Doesn't mean it has to be wrong though, but there is some aspect missing to it. The one explaining why accelerations and life exist.