Quote:Original post by taby
In fact, I have written papers that are currently under review which rely on the idea that the singularity at the centre of a black hole is fictitious. If you're saying that the equations are bogus, or that black hole's don't exist, please read Oppenheimer's work. "Pressure is a source of gravitation" might be an important thing to remember when considering stellar collapse.

Interesting. Do you provide arguments that they should be fictitious or are you simply exploring "what if" they are?

Quote:And for what it's worth, every single physicist knows that an infinite mass-energy density at the singularity cannot possibly be correct. Regardless, all of general relativity's other predictions match observation in EVERY SINGLE TEST we've thrown at it. The theory is not bogus because of a single problem.

I'm afraid you're wrong here. I'd say that mass energy density could possibly be something like a Dirac delta like the charge density we use to model the electron (and I'm a physicist).

Ok, you know what, after reading several material about all this, I think I have some *slight* idea of what is this all about. I think that I didn't say anything particularly wrong, neither did any of the people in this thread that are talking how black holes work. I think the problem is that I thought that Hawking and Penrose didn't actually know basic deductive logic(!), and the the other people think Hawking and Penrose are so focused in black holes because they claim that they can predict what will happen when a star collapses.

What triggered this, is what I read what is a "solution to GR". If I understand correctly, this means that you consider some arrangment of matter/energy and other values, and try to use GR(10 equations if I'm not mistaken) and mathematics in order to give you some idea of how it will behave. The shocking thing is this: The solutions for the system of a solid sphere mass, and a point mass took the man that did it *much* hard work, and Einstein was highly impressed. If *that* over-over-over-simplifying thing took such work, how on Earth would anyone find the solution to what happens when a star collapses? I mean, to me it seems that it would be so unbelievably hard to work out the math for even some rough estimates, that it would be an impossibility. I don't think *any* of the scientists that does work on GR believes anything other than we'll know what happens to a collapsing star when we see one collapsing(well ok, or observe something that could be a collapsed star).

Now, what I'll say I don't know if it's true, but it's what I understand from the fact that GR is 'open theory' and of what is a 'GR solution'. It's like GR, at least the bits of it where those guys are focusing) is an 'area' where exist solutions to some forms that suspect they could reveal any interesting new properties about GR itself, not the universe necessarily. It's like having an uknown material with only *some* idea of its composure, and the only thing you can do is a kind of 'stress-testing' the parts you think would be more useful to know something about it. So, I don't know, it seems to me that Hawking *is* interested in 'black holes', not because he thinks they exist in the real world, but because by examining the solution of those constucts he will find something useful that will help him reach a solution about something which *is* physical. Because that is the only thing they can do with the tools they have. Now, Hawking is a very popular scientists, people heard he was working on 'black holes', which he is, and thing everything he says is physical. I think Hawking examines the solution to 'black hole forms' in order to discover something which *could* have a physical appearance due to the properties of GR, which does not mean that this physical thing is a result of a physical black hole. It's like why they take such liberties; they are performing heuristics, not solving infinitely long equations.

At least that's what I get, the more probable thing is I'm again entirely incorrect, but since I don't have any job with GR(and neither 99% of the people who claim they do), at least I'm content that this whole thing made some sense to me; my conclusions are most probably wrong, but it gives me the feeling I understood why any 'attack' I made on the past on this thing, the scientists already knew that when they were, like, 8; I was just poking holes very near of the bits they are intersted in, but still outside ;)

Anyway...well, suprise! I don't know the first thing about GR(and I think most people here and generally most people that talk about it don't either). So...yeah :P

I don't believe the Universe has a place for "infinity", or for "infinite forces".

No matter how big things seem to get, they are and will always be finite. To me infinity equals magic, and there is no place for magic in reality.

Latest research seems to indicate that Black Holes are *not* singularities, but simply super-massive celestial bodies, very much like neutron stars (matter super-compression). Where a Neutron star is a soup of neutrons, a Black Hole might be a soup of Quarks, or a new state of matter that allows it to be super-imposed.

This seems to be in-line with Quantum Mechanics calculations, that prove that yes, it is possible to achieve the matter compression of BH without the need for a singularity, without the need for "infinite mathematics".

Also Hawking Radiation has proved that BH aren't the Gods of the Sky. They have flaws, and as is the rule for everything, even they have an End.

The possibility has also been put forward that Gravity might be a modulated force. For "very high values" of gravity, it might not be an attractor, but instead, a repulsive force. That would help explain the Big Bang, a moment where Gravity was so strong, that instead of acting as an attractor, it acted as a repulsor.

Even time seems to work with "discrete steps", and not "infinite smoothness".

Everything "that is" seems to come in discrete quantum packets, and if true, that proves there is no place for infinity.

I conclusion, Infinity, for me, is just another representation of God, of a superior force that we can't fully explain. Calling it Infinite, or calling it Zeus is the same to me, and the more science peels away the layers, the more we'll find out that nothing is infinite, for infinity is simply the absence of an explanation.

Well, I think that this thread is about the validity of the GR. And GR has infinity/singularities etc.
Am I wrong?
Well, I'm bored, that's why I write in the topic, about which obviously I don't know a shit

Hm. One last thing.

I'm thinking what happens with the analogy of Newtonian laws being correct in 'low' speeds, and become increasingly incorrect in relativistic.

For example: We consider a rocket that is scheduled to move towards a direction until it reaches a relativistic speed, and starts to decelerate until it stops.

This is what I see happening: When the rocket speed is small, Newtonian predictions are match what actually happens. When we are past relativistic speeds, they are starting to have major errors. However, we can still calculate its trajectory with Newtonian laws; we just know our predictions won't be what will happen. However, with Newtonian we will still predict that the ship decelerated and sometime again dropped into 'low' speeds, in which time again our predictions start to match again with reality.

Is this what could happen in a "black hole"? If we suppose that something "falls" into it, the prediction of its state close to the horizon will be accurate, inside the horizon won't match what really happens because by definition we admit we have no idea; it's just that we continue our calculation about its state which now makes sense only in theory, until it gets out of the hole, where GR predictions again match reality. Technically, we didn't claim we know what happens inside a horizon in *reality*, just in GR theory. Which means, inside the horizon GR is not "wrong", in the sense that the situation is unsolvable, we just can't say anything about how those "weird" values manifest physically. That is, if the GR is consistent, when the particle enters the horizon we get results which we *cannot* describe with physical terms, but when that GR-only-"particle" gets "out", again its values, like mass,speed,etc make sense again. Can that happen?

Quote:Original post by davepermen
that's ALL there is to that fancy "you'll never see him fall in". you'll see something else, as described by me and those: you see him spread around the blackhole, getting redshifted and darker and darker till he fades away.

Actually, we wouldn't see him spread around fade away etc. at all. We would see the image of him spread around fade away etc. As you wrote, he's long gone. Extruded is one word Neil deGrasse Tyson likes to use to describe what likely happens to bodies that fall into black holes. Another is "spaghettification". (See Death by Black Hole, Feb 13, 2007). At any rate, it seems to me that we run up against the limits of language when we try to describe events in this realm of physics.



Check this out: Is Everything Made of Mini Black Holes?

Quote:
By investigating quantum gravity at the horizons of black holes, a new model suggests that black hole evaporation might appear identical to elementary particle decay.

In trying to understand how gravity behaves on the quantum scale, physicists have developed a model that has an interesting implication: mini black holes could be everywhere, and all particles might be made of various forms of black holes.

The scientists, Donald Coyne from UC Santa Cruz (now deceased) and D. C. Cheng from the Almaden Research Center near San Jose, are cautious about the idea, but say that it's worth investigating with the Large Hadron Collider (LHC) and other high energy physics experiments. Cruz and Cheng have presented their idea in a study posted on arxiv.org, "A Scenario for Strong Gravity in Particle Physics: An alternative mechanism for black holes to appear at accelerator experiments."

As the physicists explain, gravity is considered an astronomical-scale force; its effects on smaller scales seem to be virtually nonexistent. However, as the scientists write, "it has often been assumed that near the Planck scale, gravity would somehow assert itself and become comparable in strength to the other forces of nature, likely as a product of some grand unification picture." Coyne and Cheng approach the problem of small-scale gravity by presenting a new model of black hole evaporation. As black holes lose energy, they slowly evaporate, shrinking in size down to the quantum scale - where they may be identical to elementary particles.
...
When the physicists investigated what these mini black holes would act like, they found that the quantization of space at this scale would mean that mini black holes could turn up at a wide variety of energy levels, and in large numbers. They predict that these black holes might be so common that all particles could essentially be various forms of black holes at different energy levels.
...

Also check out the "The Schwarzschild Proton" paper here. It generated a buzz last year.

Quote:Original post by LessBread
Actually, we wouldn't see him spread around fade away etc. at all. We would see the image of him spread around fade away etc. As you wrote, he's long gone. Extruded is one word Neil deGrasse Tyson likes to use to describe what likely happens to bodies that fall into black holes. Another is "spaghettification". (See Death by Black Hole, Feb 13, 2007). At any rate, it seems to me that we run up against the limits of language when we try to describe events in this realm of physics.

Actually, I really start to think that it's not possible that 'he' is 'long gone'. That implies that we know that there is an austronaut inside the horizon. Actually no, more like inside the horizon, are the real particles, electrons,protons and such. I think they're saying that inside the horizon there are some values that are valid in GR, but we have no idea to "translate" those values into something that we can understand. As an analogy, it's like encrypted information for which we haven't still discovered the key. It's still information, but without the key all that information doesn't mean absolutely anything. As in, in GR theory, values inside the horizon are completely random, they just obey the only thing that still works in there, which is math. If there was a way to "translate" those values into things we know, like particles, energy, or even nothing more than sensible space&time in a shape that is not predicted by GR, then we would know what those random values *mean*. That is, when we have this Unification Theory, which is that thing they are looking for. Until then, those values, the whole of them, from statements to units to values, are just values that continue to obey math. "When time tends to reach infinite seconds" could be translate to be..."when mass is larger than 5g". Just like in cryptography we can translate sdlkfjsldkfjsdlkfjsdlkfj to "Hello Gentlemen". sdlkfjsldkfjsdlkfjsdlkfj is a word as much as those values that GR predicts are physical.

Quote:Original post by Prozak
Even time seems to work with "discrete steps", and not "infinite smoothness.

Well, if this were literally true then anything that moves, ever, would go from one place to another instantaneously from one step to the next. So really, you're substituting "infinite speed" for "infinite smoothness."