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Black Holes

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JRoberts,

The PM (Personal Message) mechanism is the right one to use for personal questions. If you put your question at the begining of a discussion thread, please do not limit it to someone specific.

I edited the title of this thread to reflect the general topic.

Depending on how this discussion develops, I may merge it with other threads about Physics/Astrophysics.

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I was curious to know why you do not believe in Black Holes, and what you think exists in the areas currently considered to be Black Holes.

I am not sure who "you" is meant to be, but I will answer anyway. Black holes are a mathematical prediction of general relativity, and the central singularity is part of a generic feature of solutions to the field equations in relativistic cosmology, and gravitational collapse in general. But physical singularities cannot exist, period. General relativity has made many startling predictions that have been experimentally confirmed, but not all mathematical predictions are, of necessity, real.

As to "what you think exists" where black holes are now posited to be, that is a somewhat complicated scientific question. I will just briefly indicate two issues.

First, some of what you hear of as being "observations" are not observations at all, but rather are inferences drawn from other data. Those inferences are only as good as the theory upon which they are based, and what we may, in fact, be "observing," is nothing more than a theory trying to explain something which the theory itself, not reality, created in the first place.

But, second, if we grant that certain of these effects are real, such as rotation speeds of galaxies, then the proper approach is to seek some understanding of possible, not fanciful, physical processes that would explain such phenomena. A few others who, like myself, grant absolutely no validity to the notion of physical singularities, have begun to explore much more reasonable processes to explain the behavior.

For instance, a new solution to Einstein's field equations was recently discovered, one which has a very small, but nevertheless finite thickness of ultracold matter with ultra-relativistic energies, all of this surrounding an interior region that has certain quantum properties similar to what you may have heard referred to as a Bose-Einstein condensate.

The solution removes both the event horizon and the central singularity of the black hole solution -- the part which is not only scientifically objectionable to me, but philosophically objectionable -- which in and of itself should qualify this "gravastar" as being more worthy of consideration. However, this is just an initial step -- it is a static solution and a dynamic solution must also be found. The authors are confident that this can be done, but ultimately this new approach will rest on their attempt to unify quantum field theory with gravity.

There also exists evidence for the possibility of gravitational collapse, not as complete collapse to a singularity, but as a process supporting a density not previously considered. A fairly recent measurement by the Chandra X-ray Observatory space telescope indicates that the star RX J1856, that was thought to be a neutron star, appears to be more compact than a neutron star would permit. This suggest that the neutrons may have degenerated into their constituent quarks, resulting in a more dense object than had ever been previously observed. This may be an intermediate state that provides the density to explain observations, yet supports against complete gravitational collapse to a singularity.

To sum up: There is a growing body of evidence which, if taken to be something other than mere inferences from a failed theory, indicates the existence of extremely dense objects in the cosmos. One can, and should, reject the notion of the existence of a central singularity, and search instead for physical processes which actually make sense in explaining this phenomena. Unfortunately, theoretically, we are at but the very beginning stages of such an investigation, and the sooner invalid notions such as physical singularities are purged, the sooner meaningful explanations will be found.

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  • 9 months later...

I see four very speculative possibilities for dealing with the central singularity of the Schwarzschild solution:

1. The in-falling particles all combine together into one monster elementary particle.

2. Some unknown state of matter is created at extremely high densities which has a very high negative pressure creating anti-gravity which slows or stops the collapse.

3. Gravity slows time inside the black hole preventing the creation of the singularity until the black hole evaporates due to Hawking radiation. This still leaves the problem of what happens at the last moment when the black hole disappears.

4. The extreme densities force the creation of tachyons (particles moving faster than light-speed) which carry away enough energy to stop the formation of the singularity.

- - - - - - - - - -

However, the event horizon cannot be removed by such devices. A black hole with a large enough mass (larger than a galaxy) would have only a small tidal effect at its event horizon so that conventional physics would have to apply, not allowing for any escape.

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I see four very speculative possibilities for dealing with the central singularity of the Schwarzschild solution:

1. The in-falling particles all combine together into one monster elementary particle.

2. Some unknown state of matter is created at extremely high densities which has a very high negative pressure creating anti-gravity which slows or stops the collapse.

3. Gravity slows time inside the black hole preventing the creation of the singularity until the black hole evaporates due to Hawking radiation.  This still leaves the problem of what happens at the last moment when the black hole disappears.

4. The extreme densities force the creation of tachyons (particles moving faster than light-speed) which carry away enough energy to stop the formation of the singularity.

- - - - - - - - - -

However, the event horizon cannot be removed by such devices.  A black hole with a large enough mass (larger than a galaxy) would have only a small tidal effect at its event horizon so that conventional physics would have to apply, not allowing for any escape.

Or 5. Everything you just wrote is just a rationalistic endeavor to evade the fact that a singlarity can not exist.

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My opinion of black holes is that, obviously something exists, since we have observed something's existence. But they deal with advanced physics that are beyond our current comprehensions. Something like ancient men trying to integrate the movements of celestial bodies into their geocentric theory. There is nothing wrong with being incorrect, so long as we are using our reason as our only absolute.

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What do you guys mean by "singularity?"

A singularity is a phenomena predicted by Einstein's physics in which a large amount of matter is compressed into an infitely small, infinitely dense entity. Einstein himself had trouble with this part of his theory because he believed nothing in nature could ever be this weird.

Such a phenomena would exert gravity so great that nothing, not even light, can escape. When scientists observed such "dark areas" in the centers of galaxies, they theorized that singularities were the cause and named the phenomena black holes.

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Here is what I think about Black Holes, Existence Exists. Black Holes exists, what compound of materials they are made up off is not known at the present time. A is A, since black holes do exist then they, too, have an identity and must act according to the nature of their existence, we do not yet know what this nature currently consists off though. Will this nature and the matter of their existence ever be known in my lifetime, who knows. Do I really care about this phenonmena, not really. I have more important matters to think about and discuss than worrying about a black hole millions of light years away.

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This is incorrect, if it exists, it must be some form of matter. Existence exists and matter cannot be created or destroyed.

Just because something exists doesn't mean it has to be composed of matter. Consciousness, for instance, or concepts. I jumped on your statement about black holes because it seemed to imply that black holes had some kind of chemical structure ("what compound"). If that isn't what you meant, I have no qualms with your statement.

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dondigitalia said "A singularity is a phenomena predicted by Einstein's physics in which a large amount of matter is compressed into an infinitely small, infinitely dense entity. Einstein himself had trouble with this part of his theory because he believed nothing in nature could ever be this weird.".

Einstein's theory of gravity (with the somewhat confusing name "General Theory of Relativity") assumes that the Special Theory of Relativity holds to a first approximation at every event (place and time) in a free-falling frame of reference.

A singularity would be an event where that is not true, in other words, the existence of a singularity would contradict the basic assumptions of General Relativity.

So if General Relativity actually predicted a singularity, then it would be contradicting itself. Thus it would be false. Fortunately, it does not predict a singularity.

The singularity in the Scharzschild solution arises from the fact that the solution is defined in a contradictory way, IF you try to extend it all the way to the very center. The Schwarzschild solution assumes that there is no stress-energy in the region it covers, but there must be stress-energy somewhere in the central region to generate the non-trivial curvature of space-time outside.

General Relativity says that Einstein's tensor (a function of the metric (distance) of space-time and its first and second derivatives) is equal to the stress-energy tensor (mass-energy, momentum, shear, and pressure). It is consistent with any smooth geometry of space-time provided that an appropriate kind of matter exists to produce the equivalent stress-energy.

Theorems about the "inevitable" formation of black holes and their central singularities are based on additional assumptions about the kinds of matter that are generating the stress-energy.

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This was covered in another thread somewhere....

Most every physical theory makes disturbing predictions in some extreme limiting cases. The fact is that every theory should be linked to a domain of applicability. In this domain the theory is a fair approximation of observation. Outside the domain the theory breaks down. A disturbing prediction like a singularity just means that the theory has broken down in this limit, and its results are no longer meaningful.

In fact our contemporary knowledge of physics dictates that the prediction of a singularity be taken as outside the domain of applicability of General Relativity. A singularity by definition exists within a domain that requires appeal to Quantum Mechanics (small scales and high energies). General Relativity doesn't include Quantum Mechanics, so any predictions at quantum scales and energies is outside the domain of applicability.

Basically there is no point in getting to deep into what is going on at the core of a "black hole" until there is a theory unifying General Relativity and Quantum Mechanics.

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