Doubting the Existence of Black Holes 338
The Good Reverend writes: "It seems that there's a growing movement that doubts the existence of black holes, going against most of the rest of astrophysics. They suggest the existence of gravastars, "star-size agglomerations of "wavelike" substance" (space-time fabric, if you will). Different scientists claim to have created the "wavelike substance" in a lab, called Bose-Einstein condensates." I understand gravastars taste terrific with cream cheese and red onion.
just semantics (Score:2)
Re:just semantics (Score:3, Informative)
No, it's not just semantics. There's actually a huge difference between gravastars and black holes. The key difference is that a black hole contains a singularity. A point at which our physics break down. This is commonly described as the point where the physics are "undefined". A gravastar doesn't have this. Physics contiue to make sense within a gravastar. I haven't studied it in detail, but that's the claim.
No alternate universes, no place to go, except a big fat heap of particle soup to go crashing into. Okay, more like a big particle rock, than a soup.
Of course, the biggest difference is that gravastar is just a much cooler name.
Re:just semantics (Score:4, Informative)
Black Holes Disputed [slashdot.org]
Sig: What Happened To The Censorware Project (censorware.org) [sethf.com]
Re:just semantics (Score:3, Insightful)
Not as far as any external observations go. What is comes down to is philosophy of science.
The definition of a black hole = singularity is a modern one. The idea that things might be so massive that light cannot escape predate Einstein by a couple of centuries. Hawking has the paper in the back of one of his books, the one that starts 'Consider a Hausdorfian Manifold of Lipschit signature...' clearly one of his pop-science efforts.
There being no observable difference from outside the black hole the issue of what happens inside is irrelevant (except to omnipotent beings). Conventional physics might as well go hang when it tries to predict what happens since the area beyond the event horizon is out of bounds.
There is a similar debate in QM (which Einstein was also on the losing side of), does God really play dice? The apparently random interactions of QM can be explained deterministically if one posits the existence of hidden variables. However a theory based on variables that cannot be observed is not empirically verifiable, let alone falsifiable and thus lies in theology rather than science.
What underlies the whole debate is the question of whether physics is a model of the universe or THE TRUTH. Theoretical physicists often fall into the belief that they are discovering the truth about everything rather than merely a theory that is consistent with empirical observations. This is what is really behind the Sokal attack on Literary criticism, he takes offense at the insistence of Derrida and others that science is a set of working assumptions rather than an absolute. Ironically Sokal appears to be enlisting Popper in his cause which is strange because Popper's entire point was that absolutist ideas were bad and that the term 'science' was being abused by the pseudo-science of Marxists and Freudiam Psychoanalysis. Later discussions between Popper and his critics (notably Khune) makes it very clear that Popper was quite consciously raising the bar of 'scientific method' above the standards science itself applies.
So the fact that the standard model and relativity fall apart in the inside of black holes does not worry me much. We know that they are both wrong since they are (currently) incompatible.
Black holes and the QM hidden variables appear to me to satisfy Broomfondle's demand for 'rigidly defined areas of doubt and uncertainty'.
Re:just semantics (Score:2)
Re:just semantics (Score:2)
Re:just semantics (Score:2)
Re:just semantics (Score:2)
In any case, this is exciting research, even though it might make some cheesy Disney flicks [imdb.com] totally obsolete...
Re:just semantics (Score:2, Interesting)
The real breakthrough will come when this kind of science is no longer publically judged by the people who make the theories. There is huge evidence pointing to the big-bang being totally wrong, i.e. the cobe background radiation measurements were 1000 times smaller than bigbang theory makes them...did steven hawking mention this in his book? did he fuck.
Having just read up on plasma cosmology, a theory that can be almost entirely proven in the laboratory, then reading up on big-bang which has only faith and ignorance to back it up, I find it hard to imagine any breakthrough will come very soon while the people that choose which papers/theories are made public refuse to choose any that disagree with their own personal agendas.
if you're interested read this book The big bang never happened [nowscape.com]
I don't think its entirely correct...it skips over the hubble expansion too quickly...but it certainly is an impressive theory, and most of it is proven.
pkm
Neutron stars (Score:3, Interesting)
Re:Neutron stars (Score:3, Interesting)
Re:Neutron stars (Score:2)
Don't let that stop you; it's never stopped anyone else on slashdot...
Re:Neutron stars (Score:3, Informative)
Re:Neutron stars (Score:2)
Neutron star guts. (Score:2)
Neutrons are fermions, as another poster pointed out, so they don't form a Bose-Einstein condensate.
Instead, they form a Fermi-degenerate system. No two neutrons can have the same quantum state, so they "stack up" from the lowest energy state on upwards (just as electrons "stack" to fill the different orbitals and shells in an atom).
A neutron star doesn't have many protons. Electrostatic repulsion between protons packed that densely would cause them to have a horrifically high potential energy, so instead they merge with electrons (at an energy cost) to become neutrons (or you could consider them to emit positrons; same net effect, different reaction path).
For the electrons bound to an atom, electrostatic forces are what cause the electrons to stay bound. For an atomic nucleus, the Strong force keeps the nucleons bound. For a neutron star, gravity keeps them bound. But you end up with the same kind of system in each case - particles that exclude each other filling up increasingly-energetic orbits because they're not allowed to have the same state.
A neutron star could be thought of as being similar to a giant _nucleus_, but it'll have many interesting features not found in an atomic nucleus (because it's big enough that the Strong force only affects parts that are really close to each other, and because you can get more ordinary material piling up on its surface, and because very high energy orbits many make other kinds of decay energetically favourable).
I hope this helps
Re:Neutron stars (Score:2)
--
Evan
Re:Neutron stars (Score:2, Interesting)
Interestingly (or not...) the Russian term for what we would call black holes is a frozen star. As a star collapses to form a black hole, the photons exiting as the mass passes the event horizon are trapped permanently at that point, hence frozen. It still looks black because they are just staying there, not getting to us.
Metatheorems (Score:3, Funny)
Re:Metatheorems (Score:2)
Metatheorems obviously have metaproofs.
The metaproof is this case is quite simple. Unfortunately it is *so* simple that I can't find a way to get it past the Slashdot lameness filter.
-
Perhaps someone could explain... (Score:4, Interesting)
I have often wondered (but never had the time, inclination or intelligence to go find out
I guess that either:
a) It can't, ergo black holes don't exist;
b) It can, and Einstein was wrong somewhere;
c) There is some effect similar to the X-ray "emissions" from black holes, whereby the particles appear to come from the black hole but actually never cross its event horizon.
Which just goes to show that a little knowledge is a dangerous thing.
Re:Perhaps someone could explain... (Score:2, Interesting)
Re:Perhaps someone could explain... (Score:2)
You can no more escape the event horizon of a black hole by doing this than you could accelerate to the speed of light...
Re:Perhaps someone could explain... (Score:2, Interesting)
Consider a Mars rocket taking off from Earth. Pick a point early in its take-off when it is travelling, say, one mile per second. Escape velocity from Earth is more like seven miles per second; since the rocket is not travelling this fast, it is tempting to say it won't escape. However, clearly the rocket does indeed escape. The reason is that the rocket is not ballistic: it is powered.
I don't see any reason that a powered rocket couldn't climb out of the event horizon while travelling slower than the speed of light.
However, I'm no expert on general relativity, so perhaps there are spacetime curvature/time dilation/whatever effects that I'm not accounting for.
Re:Perhaps someone could explain... (Score:2, Informative)
Since escape velocity is the speed of light and because relativity prevents you from accelerating to the speed of light, if you fall inside the event horizon then according to relativity you can't get back outside.
This does not mean that you will die as you pass the event horizon but it does mean that as far as the outside world is concerned the only measures that you ever existed are the changes in the mass, angular momentium, and charge of the hole which you caused.
Hawkings, using quantum theory, showed that you will eventualy make it out of the hole via the emmision of one part of a particle/anti-particle pair(Hawking radiation). But the only information about you that will be conserved will be again be your mass, angular momentium and charge, so your not coming out the way you went in.
But besides all that those of us who find ourselves trapped inside a massive event horizon can still live happy and productive lives, we just can't post on
Re:Perhaps someone could explain... (Score:2, Informative)
This is something that I hear ALL the time: that Hawking radiation lets some matter escape from a black hole. In actuallity, the particle/antiparticle pair are created (via the QM fluxuations of empty space) OUTSIDE the event horizon. One of the pair goes past the event horizon and the other (just barely) escapes. This is Hawking Radiation.
Re:Perhaps someone could explain... (Score:2)
The problem with this type of Newtonian description of an essentially non-Newtonian phenomenon is that people try to extrapolate from their understanding of Newtonian gravity (a post lower down, for instance, suggests that maybe you could climb out of the hole "slowly" without reaching escape velocity, just like you can get to the moon without reaching the escape velocity of the earth). The event horizon is, however, much more than "just the distance at which escape velocity exceeds that speed of light"; the very structure of space and time changes at the event horizon. You can prove mathematically within the confines of classical tensor theories of gravity, that the event horizon is a surface that bounds a region where all light-like and time-like trajectories are trapped, for the entire future history of the universe. In english, any piece of matter, and any photon that crosses that surface will NEVER be able to get out, no matter how hard you try (and in fact, the harder you try, the more stuck you get :-) These processes are inherently unlike gravity as you learned in high school and freshman college physics, and you just (unfortunately) can't really make the escape velocity analogy.
Re:Perhaps someone could explain... (Score:2)
I think I understand what the poster you responded to was asking. Do you necessarily have to reach escape velocity in order to leave the Earth? If I had some way to move slowly up through the atmosphere, all the way to the moon, for instance, I wouldn't be dragged back to Earth simply because I never reached escape velocity.
Re:Perhaps someone could explain... (Score:2)
v_escape = c = sqrt( 2G*M_body / ( R_body = 1 ))
=>
M_body = 2.99E22 kg (roughly 1/2 size of moon)
gravitational acceleration at surface of body is:
F=unit_mass x a = G x M_body x unit_mass / R_body^2
=>
a = 2E12 m/s^2 which is roughly 1/2c^2.
The greatest energy you could contain would be E=mc^2, but you'd have to have excess mass left over to accelerate. From this, it would be impossible for an intact body to escape the event horizon (e.g. the destructive force of a perfectly efficient matter-energy conversion imparted 100% in one direction onto a body of matter would be devistating)
This is a simple argument based on quickly running through my old physics text book... I'm sure there are other approaches that would demonstrate the impossibilities of escape.. e.g. derived equations.
There is only one wrinkle in this endeavor, as far as I'm concerned.. There is a large body of scientists that disbelieve the singularity of a black-hole. It doesn't make sence. Thus, if an event-horizon producer must have spacial geometry (other than a point), it has to have density. That density will most likely be non-uniform or have maximal density: e.g. the proposed Bose-einstein condensate occupies a set of minimal quantum states which means greater "mass" requires a greater expanse.
If there exists a max density, then eventually the radius of the body would grow until the event horizon dissapears.
If there isn't a max density then there could be undulations (density fluxuations) which warp the event horizon (thereby allowing burps like solar flares). These warps would magically allow matter towards an edge of the event horizon to suddenly be on the outside and thus could escape (given a pre-existing and nearly infinite buildup of energy).
Another interesting point of view: For a solid spherical constant-density object, the center has zero gravity and the surface has the greatest gravity (due to counter-balancing forces). Most likely density will shrink radially outwards as a warped exponential. The inside will be a bose-einstein condensate, then there will be a layer of solid, then liquid, then gasious-plasma all the way out to the event horizon (and most likely beyond). From this, there is an uneven force distribution. The bose-einstein condensate will be at zero gravity (albeit with lots of inward force). For it to achieve this state, all of the kinetic thermal energy needs to be "squeezed" outwards. Due to the different states of matter, there should be a multi-tiered set of corona's. Further, since the gravitation is zero in the center, energy from those coronas should be allowed to probagate outwards. But as we've calculated, the event horizon limits how far that energy can extend radially. Thus, there should be a massive corona somewhere mid black-body. This is because energy CAN go outwards from the center, and it can only go inwards from the edges. Each phase-layer will amass a nearly infinite amount of energy over time, which will allow it to grow outwards by tiny amounts (as the energy accumulates). At equlibrium, this energy corona should be at a relatively constant radius. I'm pulling stuff off the top of my head, so I'm sure there are forces I'm missing. I can't even comprehend the complexity when we consider a growingblack-body at the moment.
The net effect is that of a giant blender. We take matter, and literally rip it to pure randomized energy: running it through most every state of matter, compress it to hell, super-heat it (in the corona), then eventually sweat it back out again.
Personally, I believe the whole point of it [black-bodies] is to destroy information. While theoretically you can't create or destroy entropy, we're talking 99.9999999999% loss of information, and that's got to account for even God's round-off-error. (Speaking metaphorically)
Anyone have refutations, or additions?
Note, this is all based on the idea of a non-singularity (which I personally must believe). Later work is based on the artificial concept of maximumal density (extrapolated from quantum states).
-Michael
p.s. Non-singularities are described by several existing theories. While I only have a crippled lay-person's understanding of string theory, another more controversial theory (which I consider plausible) is that of Ether. Here's a sight that I've researched (aethro-kinematics [aethro-kinematics.com])
We arent sure about that (Score:2)
Others claim you get crushed out of exsistance, we really dont know anything about blackholes until we send something into one.
As far as creating blackholes in labs, do they even count?
Re:Perhaps someone could explain... (Score:2, Interesting)
The Theory of Everything (Score:2, Informative)
(http://www.fortunecity.com/emachines/e11/86/di
which talks about the universe being a single membrane, of which all matter (and energy and everything else) in the universe is part. This exists in 11 dimensional space.
M-theory is an evolution of string theory
The theory goes that gravity is seepage from another universe a small distance away (like a few mm) in 11 dimensional space.
They believe that in essence gravity is the same strength as the strong nuclear force but what we feel is the translation of that into just 3 dimensions and acting at a short distance. This would then imply that the limit on gravitational forces would be of the same order and would occur when two such universes where very close.
Incidentally M-theory also can explain the big bang as a collision of two membrane universes.
Re:The Theory of Everything (Score:2)
Re:Perhaps someone could explain... (Score:5, Informative)
I have often wondered (but never had the time, inclination or intelligence to go find out :)) how a quantum view of gravity would affect theories on black holes and the birth of the universe. Basically my question is: If gravitational attraction is carried by a particle (the graviton) as is conjectured by many scientists, then how can one of these escape from a black hole any more than another particle?
The latest theory of quantum gravity under discussion is the 11 dimensional m-theory, which models the universe as a four dimensional spacetime embedded in 10 space and 1 time dimensions. In this theory, gravity, and therefore gravitons, are the interaction between two closely seperated membranes, one of which is our universe. gravitons propagate in all 11 dimensions of the theory, and can therefore propagate out of the 4-d black holes 3-d event horizon by taking a trip through the higher dimensions.
It's not that Einstein was wrong, as his field equations still produce the correct results for large scale gravity in m theory, but just that he didn't go far enough towards a quantum theory of gravity, for which the mathematical tools just weren't available.
Re:Perhaps someone could explain... (Score:2)
I personally think that gravity is not a fundamental force, but an emergent, probabalistic "Force." I'm stying to make this result come out of the math, but it's tricky. This makes sense, given gravity's ridiculously small magnitude, and would offer at least a testable hypothesis. This hypothesis doesn't mean that things sometimes go up when they should go down--- look at the second law of thermodynamics, and show me a time an egg put itself back together.
My point is, at least promote theories which can be tested.
(BTW, I also understand that QCD has the same problem of unsolveable equations.)
Re:Perhaps someone could explain... (Score:2)
Re:Perhaps someone could explain... (Score:5, Insightful)
So far no one has produced any strong objections to m-theory, and m-theory has been used to produce a model (the Ekopyrotic model) for the instant of the big bang. The ramifications of this model are currently being worked out, by amoung others, Martin Rees, Steven Hawking and Neil Turok (in Cambridge alone). The current work is to calculate the effect the Ekopyrotic model has on nucleosynthesis, baryon fraction and primordial CMB imprints and structure formation in the early universe. With the advent of CMB anisotropy experiments such as the VSA, CBI, DASI, Planck and MAP, these predictions will be tested in the next decade or so.
M-Theory also has possible implications for results in within the reach of the LHC accelerator at CERN, which should start producing results of searches for supersymmetric particles about a decade from now.
QCD does have problems with renormalisation, and perturbation techniques at low energies, but these vanish as the energy of the particles increases.
I won't comment on you theory above until you have a working mathematical model for the theory.
Castles in the sky. (Score:2, Insightful)
Re:Perhaps someone could explain... (Score:2)
http://math.ucr.edu/home/baez/physics/Relativit
Slashdot is for some reason putting a space in the "BlackHoles" segment of the URL. There should not be one there.
Re:Graviton (Score:2)
understanding it (Score:2)
Confusing article -- read the paper (Score:5, Informative)
I couldn't make any sense out of the SFGate article, so I found the original paper [arxiv.org].
It appears that the authors are proposing that a form of Bose-Einstein condensate can prevent full gravitational collapse, though I don't quite understand why they think this is such a good idea... Avoids the information paradox, I suppose.
Re:Confusing article -- read the paper (Score:3, Insightful)
Avoids the information paradox, I suppose.
That in itself is reason enough to be looking for something better than black holes. Singularities, information paradoxes/loss of information, infinities... A theoretical object like a black hole SHOULD be suspect due to the above. It should NEVER have become a dogmatic, accepted object because it has so many problems. It boggles that some pish-posh the gravastar idea because they don't like the ideas behind it...yet they accept even more nonsensical thinking about black holes. I assume that it is merely the fact that black hole, black hole, black hole has been pounded down the collective throat for so long that it is accepted by fiat. Bullcrapola. Bad scientist! If your object leads to infinities, then there is something wrong with the idea/theoretical underpinnings of that object.
They (the astrophysicists and cosmologists) should ALL have followed their instincts which tells them "BULLCRAP!" whenever they come across the infinities, singularity, information loss problems, entropy problems of black holes. They have misled themselves into accepting as fact something that really cannot be (at least in the way it is described). Gravastars eliminate most, if not all the GLARING problems inherent in the idea of the classic singularity-containing black hole.
Re:Confusing article -- read the paper (Score:4, Informative)
I'm sorry, but that's not scientific. There's nothing about infinities that cause them to be rejected out of hand.
For example, if a cosomological theory leads to a model where there is an infinite universe, well, there's nothing wrong with the theory because of the infinity involved.
Calculus is based on infinities, and it seems to describe a wide range of real-world phenomenon.
When black holes were postulated, it was necessary for those who might refute them to come up with what would prevent the singularity from forming, what exactly in matter would withstand the crushing gravitation. Nobody did so the theory became established.
The fact that singularities lead to contradictions requires further investigation, but you need reasons to reject the singularities. The contradictions might have been resolved by revising other theories, for example. That's how science is advanced, actually. We come up with contradictions and they are resolved by revising theories. However, revising theories requires evidence and reason, not just "Nope, singularities obviously can't form because it would lead to contradictions."
Looks like someone has finally come up with some reasons why singularities don't form. That's scientific.
However, it's unscientific to reject an idea because it "feels" wrong,"seems" contradictory or instinct "tells us". What's needed is reasoning, not vague feelings.
Re:Confusing article -- read the paper (Score:3, Interesting)
Nicely summarised, although I think you are a bit too quick to suggest that the gravistar model comes with a "reason why singularities don't form". My understanding of the original paper is that if you can find a collapse mechanism that produces the needed Bose-Einstein condensate, then you can avoid the existence of singularities in the collapse of massive stellar objects. In that way, it is a very interesting suggestion. Unfortunately, I don't recall the authors having found the needed mechanism.
And that is the problem. For black holes, we think we understand quite well the collapse mechanism that leads from a massive stellar object to a black hole final state. And we also suspect that the problem of singularities may really be a non-issue: we expect that the fundamental theory of gravity must have a quantum nature, and that the quantum effects will become important long before the point of singularity is reached (in some sense, the singularity would be "dressed up" by quantum interactions, and potentially "smoothed out" such that there isn't a singularity). Let me point out that this is not such a silly expectation: classical electrodynamics, classical Newtonian gravity, classical theories of radioactivity, all suffer from the same types of singularities, and the quantized versions of those theories eliminate or mitigate many of the singularities of those theories.
Re:Confusing article -- read the paper (Score:2)
Infinities are theoretical. They, by definition, are not measurable nor understandable. No physicist can TRULY grok the idea of "infinity" (no one can). Just because the math goes stupid in some situations doesn't make it magically correct either. The math is not reality, it is our best derived MODEL of reality.
Quantum mechanics also gives us goofy particles like tachyons. Most quantum physicists give those particles a pass - they are a mere flake on a sidepath of the math. Just because the math says they're there doesn't mean they ARE there. QM physicists pick and choose which infinities or remainders or chaff to keep and which to toss depending on what they are trying to say. The numbers don't mean its true. The bulk of it acts as a good MODEL of the way things are but it is totally different than saying it IS what is. No. The math is a MODEL, a human-derived, incomplete, model. It ISN'T the reality, the reality is there inspite of the math.
Say Goodbye to QM (Score:3, Informative)
There goes quantum mechanics. The single most precisely verified theory in the entire history of science has just been rejected because the equations produce infinities. Feh! on your so-called "renormalization" techinques. It's non-mathematical handwaving. Someone call Feynman's family and get his Nobel Prize back.
Re:Say Goodbye to QM (Score:3, Interesting)
Quantum mechanics also produces superfluous nonsense that is commonly ignored or tossed out by mainstreamers (tachyons anyone?). The actual stuff that works works without implying infinite density or infinite energy. THOSE are problematic infinities. Infinite energy my ASS.
Since some of the goofy dangling math of quantum mechanics is routinely tossed out as artifactual, then so too can black holes with singularities and infinite density and infinite energy be tossed.
Choose your infinities well. Some of them are infinitely ridiculous.
Again...since cosmology uses and accepts the idea of phase changes in space during universe development, and it is tied closely into quantum mechanics, why is it suddenly and specifically ridiculous to posit such a phase change within the extreme environment of a collapsing supermassive star? Is it also bogus that cosmologist also suggest that there COULD be future phase changes in the universe of unknown type and consequence? That idea also derives from quantum physics...based on past universe phase change(s).
Re:Confusing article -- read the paper (Score:2)
Well, I could get rid of all the glaring problems by postulating that the inrushing shell of matter is kept aloft by the work of angels, too. But that doesn't make me likely to be right. The gravistar has been invented, from whole cloth, specifically to remove these difficulties. I think that extreme skepticism is justified, failing some theoretical or empirical reason unrelated to black holes to believe in gravistars.
Re:Confusing article -- read the paper (Score:2)
Until unified theory its wait (Score:3, Insightful)
Gravastar != Bose-Einstein Condensate (Score:2, Informative)
To clarify, the SFGate article [sfgate.com] points out similarities between a (theoretical) gravastar and a Bose-Einstein condensate -- it does not state that they are even remotely the same thing.
From the article:
So don't worry, those experiments across the hall are not creating the stuff that gravastars are made of.
Strange writeup for a silly article (Score:5, Informative)
"Claim" is hardly the correct word, since it is not disputed (to my knowledge). Last years Nobel Prize in physics was awarded to the first experimenters who created this sixth (depending on how you count) state of matter. The existence of Bose-Einstein condensate is not in itself any challenge to black holes.
The article states: Calculations show that a black hole would contain astoundingly more "entropy" than the matter that fell into it
If the article was less sensationalist, they would have mentioned that there are also calculations based on Hawking radiation that show the entropy of a black hole to work out perfectly. Some say the entropy is wrong, others don't. Also, referring to singularities as "paradoxes" seems strange. One would rather not deal with them, of course, but paradoxial? Nah. Since they are always hidden and cannot be reached in finite time, the philosophical question is whether they even can be said to exist in the same way as other things exist.
The article also does not increase in credibility, when it refers to the uncertainty principle as "eerie" and to black holes as "spooky" and "scary".
What about gravastars then, are they for real? Dunno... Most theories are at the fringe for a good reason, though.
There is a good reason ... it's new (Score:2)
There are tests that are possible, so it's predicting a real difference. Unfortunately, I don't know of any that are exactly practical for us to undertake (could be wrong here, I haven't been paying that much attention).
This isn't unusual. It is frequent that there are multiple theories that explain what we know equally well. Usually the simplest one is the one that people stick with, but the first one to appear has a big edge. So black holes will probably win out until we get close enough to really examine one of the monsters. Then we may rethink things.
Still, if the brane theory and it's Big Bash wins out over the Big Bang, then there won't be any need for a singularity at the start of the universe (though I believe that Hawking questioned that anyway) so it might be simpler to just beleive that there aren't any singularities, in which case the gravstar theory would win
Truth can't ever be known, only approximated. But with skill the approximations can get pretty close.
Re:Strange writeup for a silly article (Score:2)
Last years Nobel Prize in physics was awarded to the first experimenters who created this sixth (depending on how you count) state of matter
How would I count if I wanted to get to six? Solid, liquid, gas, plasma, condensate, ???
Still a hole (Score:3, Informative)
Re:Still a hole (Score:2)
True, for a stationary black hole. But a rotating black hole is a lot more complicated [syr.edu]; if it's rotating fast enough, the singularity (if there is one) can actually be exposed.
(Yeah, yeah, how can a point rotate? Well, angular momentum is assumed to be conserved. Indeed, recently NASA discovered good evidence [nasa.gov] that at least some black holes do, in fact, spin.)
Anyway, this "gravastar" model would presumably show markedly different results in the rotating case.
Re:Still a hole (Score:2)
As I understand it, the inner "space-condensate" would eactly (or nearly exactly) match the size of the event horizon. No more issues with passing the event horizion. Everything just piles up really really close to it.
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Bose-Einstein Condensates and Black Holes (Score:5, Informative)
A very massive star has a very massive gravitational field. Through its lifespan the star does not collapse under its own weight due to the ongoing fusion reaction which powers all stars. When the nuclear fuel finally runs out, the star begins to collapse inward. (For those of an astronomical bent, yes I am skipping over some details as to the various stages of fusion that grant temporary repreives to the collapse).
As a star collapses, the atoms that make up the star are packed more and more tightly together. If the star is massive enough, the electrons and protons are finally merged together to form neutrons. The neutrons then pack together more and more tightly until the repulsive force between the neutrons prevents further collapse (for stars not quite massive enough to become black holes) or the neutrons themselves crush in upon each other into even more degenerate states of matter. As far as we know, once you pass this point there is NO OTHER REPULSIVE FORCE available to keep the collapse in check. The star collapses all the way down to a single mathmatical point.
The second bit of background we need is an explanation of Bose-Einstein Condensates. First, you need to know that all particles can be described as waves. In the macroscopic world in which we live our daily lives, the waves are such tiny little packets that we don't perceive them as anything more than particles. However, on the microscopic level, particles begin to really demonstrate just how wave-like they can be. When a group of atoms is collectively cooled down to very close to absolute zero, the behavior of the individual atoms become linked together and they begin to act a single atom. (The wave functions describing the individual particles merge). It is a funky-cool state of matter that is regularly used now in a range of physics experiments.
The hypothesis in the article on black holes is that spacetime itself can undergo a "phase change" not unlike the way that matter can go from solid to liquid to gas -- or even (in labs) to a Bose-Einstein condensate.
The important thing to note here is that
(a) no one has ever seen a phase change in the fabric of spacetime (I'm not sure the concept even makes sense, personally).
(b) The authors are NOT saying that the black hole's stellar material BECOMES a Bose-Einstein condensate -- they are saying the the fabric of spacetime itself becomes the "spacetime-equivalent" of a Bose-Einstein condensate (whatever that would be!).
My feeling is that while it *could* be the case, basically they are trying to dream up a totally hypothetical new phenomenon (phase changes for spacetime) to find some way to get rid of black holes in physical theory. I don't see that the new phenomenon has any grounding in theory or observation -- it's strictly hypothesized for the end result -- and is therefore very unlikely to be true.
Now, that's NOT to say it CAN'T be true. However, I expect their may be dozens to hundreds of other such hypothetical creations designed to counter the infinite collapse that supposedly occurs in black holes -- the concept of a black hole is "offensive" in physics because you end up with a big "divide by zero" error in the universe. We do, however, have good evidence for the existence of black holes, so no matter how much physicists hate what they do to the math, we may have to simply accept them.
Re:Bose-Einstein Condensates and Black Holes (Score:3, Interesting)
s far as we know, once you pass this point there is NO OTHER REPULSIVE FORCE available to keep the collapse in check. The star collapses all the way down to a single mathmatical point.
On the other hand, there are the (relatively) recent measurements of distant galaxies moving faster than expected, suggesting a repulsive force weaker than gravity. If it does exist and is governed by some power law like gravity or electrical forces, then at sufficiently small distances it is stronger than gravity, thus creating an extremely powerful repulsive force.
Perhaps a sufficiently massive black hole would even achieve critical mass and create a really big bang :-)
(I'd use equations and references, but that might give me the illusion of credibility)
Re:Bose-Einstein Condensates and Black Holes (Score:2)
I don't think anyone doubts that quantum phenomena are going to be involved in what really happens in a star that can't be supported by nuclear forces against gravity. But that doesn't mean that any wacky theory with the word "quantum" in it is automatically better than general relativity.
Re:Bose-Einstein Condensates and Black Holes (Score:2)
Sorry to burst your bubble, but renormalization has been used in all quantum mechanics since the 50s. You can't do many meaningful calculations in QM without it.
Uh Oh, I smell a new Fox Special (Score:4, Funny)
Black holes == event horizon (Score:5, Informative)
In General Relativity, given a sufficiently large mass (say, a 10 solar mass star), there is no source of rigidity strong enough to withstand gravitational collapse, so black holes will eventually form.
Big stars exist, so avoiding black holes requires either a new theory of space time (or gravitation), or a new type of matter.
These guys have opted for a new type of matter,_analogous_ to a Bose-Einstein condensate. The existance of Bose-Einstein condensates in the lab for regular matter (routine, now), says nothing about whether this exotic matter exists out there.
This is still pretty wide open from a theory vs experiment sense. Most claims for black holes are really observations of dense collections of matter. Some would be black holes for sure in General Relativity, but this is no proof.
The best source of proof for black holes will probably come from detection of Gravitational waves from their formation, which should come in the next few years from experiments such as LIGO [caltech.edu] or LISA [nasa.gov].
Not to be confused with (Score:2, Funny)
Javastars run slower than gravastars but will work in any universe.
This is a load of shit (Score:2)
This is one of the worst science articles I have ever read. Anyone who would put the word entropy in quotation marks doesn't know a goddamned thing about how the wolrd works, let alone the universe.
SetupWeasel
Tempted to agree (Score:3, Insightful)
...
Aaaaaargh. This article reads like BBC2's _Horizon_ programme. All "these people discovered some random idea, aren't they wonderful?" BS explaining why "blue" is a colour to the clueless population never mind concentrating on the idea to hand at all - apparently Bose-Einsten condensate is somehow the "fabric of the universe"?
I said way back at Uni, and will say it again: I don't want to know whether Einsten *liked* a particular idea, I want to know the *idea* and I'll make up my own mind. Give me equations, keep the pop-psych AWAY.
Re:This is a load of shit (Score:2)
Really? And BEFORE there was an "accepted" theory of black holes the equivalent scientists would tell you something totally different. Don't hold TOO tightly to "black holes" because they could well turn out to be ephemeral.
The problem of infinities is enough to kill the idea of black holes anyway. The fact that these scientists would go for an idea that contravenes ALL the rest of physics, with impossible infinities, "break downs" of the laws of physics (my ASS!). Nope, I would say that black holes are ripe for picking off.
A gravastar behaves, observationally, EXACTLY like a black hole so there is no way to argue against them on that level. At this point it is ONLY a matter of taste - do you like mystical (and bullshit) breakdowns of the laws of physics and nonsensical singularities, naked or otherwise, or do you like maintaining all the laws of physics but allow for phase changes in space-time (which fits right in with accepted cosmology, by the way, which holds that there WERE phase changes in space-time during the development of the modern universe from the big bang...and that there could be more phase changes on the way)? I like the more reasonable gravastar to the ghostie, goblinie, magic black hole.
Re:This is a load of shit (Score:2)
There is nothing magic about a black hole. Mass is energy. Black holes are a hell of a lot of mass-energy. I have no fucking clue why the word infinity scares anyone.
The truth is that there is no pebbles in mass, and by that I mean no small unit of mass that can't be crushed under the weight of other mass. Find the fucking pebble, and I'll believe the gravitar.
SetupWeasel
Re:This is a load of shit (Score:2)
SW
Re:This is a load of shit (Score:2)
Which I could rewrite as:
All of those are theories that are in extensive use and work extremely well when you stay away from the infinities. And in Quantum Field Theories, we know how to completely remove many types of infinities. Don't be so quick to toss a theory that contains infinities; they aren't the Beast.
And, gravistars DO NOT appear "exactly like" black holes; if they did, it wouldn't be an interesting idea, because black holes are so much simpler and easier to understand. If there were no observational differences, Occam's razor would have beheaded gravistars before they were published: gravistars requires much much much more complicated and completely unspecified dynamics to generate the condensates required to support the object.
Additionally, it is not clear that any of the "problems" that gravistars try to solve are really problems in any technical sense; they may or may not be, and they are under active investigation in the case of black holes. Gravistars are interesting, but they have so many of their own problems that it is not at all obvious that they are "better" than black holes in any way. Time, more theoretical study, and observations will tell the difference.
Not a good idea to post before publishing (Score:4, Interesting)
I would like to point out that posting an article before the team concerned has published their paper is very bad news for the team.
What often happens is that the team becomes doubted initially because they haven't published the paper, or because the article writer doesn't know what he/she is writing about. Sometimes it blows up in their face, ala Cold Fusion.
I would also like to note that the technical quality of the article is poor and shows a lack of understanding of the subject matter.
For example:
"The location of a particle constantly varies according to a statistical pattern -- one moment it's here, another moment it's there"
This shows a complete lack of understanding of the uncertainty principle! The particle has no 'position', and as such it can't be here one moment and there the next. Its position-space wavefunction is the best we can get.
There are also quite a lot of claims made in the article that really deserve a reference - hence the problem if the only reference is unpublished - in particular I would like to see an argument for why spacetime undergoes a phase transition inside the black hole. What theory predicted this? Certainly not General Relativity, which is what predicted black holes in the first place. What modifications must be made? How is quantum mechanics used in this setting?
Note that quantum gravity is still an unsolved problem, so I'd be surprised if this prediction turns out to be spot-on. But I can't tell for sure since the paper is unpublished =(
Re:Not a good idea to post before publishing (Score:2, Informative)
Been through this (Score:4, Informative)
And what Bose-Einstein condensates have to do with it is murky at best. Like a BEC but made of space-time rather than atoms? What the fuck is that mealy mouthed shit supposed to mean?
Re:Been through this (Score:2)
You have a ball of atoms. As you cool the ball it gets smaller and smaller, until you hit a certain point. Then instead of getting smaller all of the atoms turn into one big ball. That is BEC.
Gravity pulls in space itself. This theory says that when you squish enough points of space together all the points of space turn into one big ball. Instead of getting smaller they turn into one big object.
It's like the wave nature of things. Like the uncertainty principle - the smaller you try to confine something down to a small point, the more it blurs out into a bigger wave.
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black holes predicted 300 years ago (Score:2)
Einstein and blackholes (Score:3, Insightful)
Einstein's equations do not predict blackholes. Blackholes are simply compatable with his equations.
This does not mean that blackholes may be incompatable with other physical laws, notably those of quantum mechanics/field theory and those of thermodynamics, which is why it is theoretically interesting to try to derive the quantum and thermo properties of blackholes to find either a contradiction or an interesting property which one might try to observe from earth.
Someone who says they do not believe in black holes either
1) does not believe Einstein's equations, of which they are solutions.
2) believes that other physical laws prevent the occurrence of these solutions.
The first paper on this Bose-Einstein condensate stuff poses another solution of the GR equations in which the point singularity is replaced with a different structure, the BEC. The math seemed all on the up and up.
(BTW the Schwartzchild solution doesn't really have a singularity. The singularity is an artifact of the coordinate system used, just like the singularity of latitude and longitude of the earth -- and we do believe in the north and south poles here, right? Kruskal exhibited coordinate systems in which there is no singularity.)
So what we have is a new analytic solution to the GR equations (and there are not many, so this will undoubtedly make it into graduate texts in the next decade).
The bad news is that the geometry around a gravastar is identicle to that around a blackhole. It is just different when close to the phenomenon, so all that business about terrible cosmic death at the hands of a gravitational giant is still there.
I find that somehow relieving (Score:2)
Of course, neutron stars kill you just as dead and almost as flat...
Re:I find that somehow relieving (Score:2)
Dude...a gravastar would kill you just as deaders as a neutron star or "black hole". They still develop accretion rings, synchroton radiation, and have huge gravity gradients. The only real diff is that you get to strike the actual surface of the gravastar and get converted into pure energy, whereas there is the problem with black holes essentially stopping time (infinite gravitational energy), event horizons, etc. Nonsense, I tell you. You can account for the same observational evidence with gravastars. In any case, a gravastar is a killer too. Put that in your pipe and smoke it.
Brought up several weeks back (Score:4, Interesting)
This story first hit /. several weeks ago. I am glad to see the astrophysics community taking it onward and upward. Me no like blackie-holes. There is that ugly problem of infinities, entropy imbalances, loss of information, and so forth - none of which appear in the gravastar model...with the added bonus that a gravastar in every other way behaves exactly like a "black hole" (gravitationally).
Cosmology DOES contain ideas of phase changes occurring during the development of the universe after the big bang, so gravastars with space-time phase changes fits in there too.
It still permits sci-fi some cool material too, so the loss of classic black holes would be no biggie on that front.
Bring REASON back and eliminate "black holes". Silly, impossible buggers they are.
Re:Brought up several weeks back (Score:2)
And I would posit that if you posit a singularity, you are positing a phantasm. You have never observed a singularity and you never will.
Anything that implies infinite energy or infinite density, infinite curvature is suspect and likely wrong. I would go with Einstein's feeling that it just makes no sense and is wrong.
Since black holes have so many undisputed problems, why the investment in keeping the idea as depicted around? What sense does it make to hold on to an idea that is loaded chock full with problems? Just because? That is a horrible reason. Black holes should in no way be considered real - they should be clearly posited as merely theoretical and provisional in recognition for their many, many problems.
Hell, these guys haven't even published yet and many here are poo-pooeing it offhand. All any of us have read are the general popular press versions. Wait until they publish and THEN commense to critiquing it. It speaks volumes that there are a growing number in the field that (provisionally) accept the idea of gravastars as possible. It also speaks volumes that it is mostly astronomers who buy black holes as is while a goodly number of astrophysicists and such are not convinced and actually dislike black holes.
Ultimately the gravastar theory may be wrong AS IS, but I'll bet my left eye and right testicle that the black hole theory is also wrong AS IS.
The 'repulsive force' inside (Score:2)
Black holes? What a horrible concept... (Score:2)
Oh, right, something sensible, then.
Schwarzschild radius (Score:4, Insightful)
If this happens when the object is less than a Schwarzschild radius in size, it would look and behave exactly like a black hole to an outside observer.
(The Schwarzschild radius is the distance inside of which not even light can escape from the object. It doesn't make a difference how the matter is distributed inside the Schwarzschild radius)
I'd also be interested to know how gravastars scale with mass. The article mentioned only stellar-mass black holes, but our greatest evidence for BHs is the supermassive black holes that are thought to exist at the centers of most massive galaxies. These have masses of millions of solar masses; can a gravastar hold up that much mass?
Re:Schwarzschild radius (Score:3, Informative)
As I understand it everything would pile up just outside the Schwarzschild radius, and would look almost the same to an outside observer. This avoids the the problem of crossing the Schwarzschild radius, it never happens.
I'd also be interested to know how gravastars scale with mass... millions of solar masses; can a gravastar hold up that much mass?
The condensate would expand the same way as the Schwarzschild radius would. I believe the forces go down as the square of the radius. The "holding up mass" effect would then be a constant.
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On the other end of theories... Article (Score:3, Interesting)
This discusses the possibility of tiny black holes created by high-energy collisions (discussed in a previous Slashdot), which the researches hypothesize happens regularly in our upper atmosphere (bit of a stretch). It also discusses a novel theory as to why gravity is so significantly weaker than other local forces -- That unlike other forces, gravity acts through all the 'extra' dimensions hypothesized in super-string theory.
One of the more interesting things about the article is that it shows that with recent developments (the new Large Hadron Collider, etc.) scientists are beginning to reach a point where they can start to prove or disprove parts of super-string theory... Interesting stuff indeed!
bad author (Score:3, Insightful)
This part right here tells me the author doesn't know much about Black Holes! First of all, they are not that big. In fact the largest, and abnormally, sized Black Hole that we can observe is about 14 magnitudes greater than our own Sun. Add to that the actual size even then is perhaps the size of the moon, or less!
So when a black hole travels though space-time, it gets near another object, the process that starts takes years to finish. IT does not gobble up handful's of stars at one sitting.
We can detect Black Holes by observing the siphoning of the starts gas from a long distance. It looks like the star grows a very thin and long tendril that extends away from the star main sphere. The tendril of star stuff isn't directly consumed by the black hole. The Tendril actually forms a swirl of gas around the black hole. As the black hole closer to the star, the tendril changes form to a more amorphous shape. At that point the black hole would be totally shielded behind a torrent of star-stuff that would totally block it out any direct observation. The Star, and the black hole would begin to revolve around one-another in a dance that would end with the black hole assuming the mass of the star.
If you can imagine what I just wrote, that is what astronomers have observed.
Not only that, the author also appears to have a gross inability to describe the Bose-Einstein Condensate [colorado.edu]. The reality is that a condensate cloud could probably never exist in nature, and to call it the actual space-time stuff is absurd. The condensate cloud is more like the 5th state of matter (solid, liquid, gas, plasma, and Condensate cloud). Think of a Condensate cloud as the extreme opposite of plasma. Where one is really hot, the other only exist at supper cold temperatures. In fact, the Bose-Einstein cloud is the coldest thing we have ever created I think. At such a cold state of matter, time almost seems to stop. A really bizarre occurrence is when photons are shot into the cloud, and they appear to slow down while in the cloud, then speed up as they exit.
This same topic was publicly introduced in the Scientific American magazine a few months ago. The article was interesting, but at the end had this part about how the universe could actually be surrounded by a giant condensate cloud. The idea sounded really good until that part.
What this seems like to me is we humans have recently discovered this cosmic snaik-oil, the cold condensate cloud, and are now looking for a place to make it fit in the universe, no matter how sensational.
No black holes? (Score:2)
Some info from someone working on the subject... (Score:4, Informative)
First, it requires that under extreme situations gravity undergoes a "phase change", which for all intents and purposes means that the region inside the gravastar posseses a positive cosmological constant, effectively a non-zero energy density inherent to space itself. The notion of a cosmological constant has been troubling relativists and particle theorists for over 70 years and we still don't understand whether there is such a thing and where it might come from. Current astronomical observations suggest that there may in fact be a very small CC, but no one knows a mechanism for how this might be "produced" inside a gravastar. The earlier work of the Los Alamos crew makes some suggestions for how this might come about, but is itself based on a field theoretic treatment of gravity, a pretty shaky proposal whose predictions are hard to identify and must be taken with a grain of salt.
Second, they propose an interface layer between their "gravitational BEC" and the world outside the gravastar, made up of "ultra-stiff fluid". In GR we often resort to desribing distributions of gravitating energy and matter as a perfect fluid with an equation of state that relates how much energy density there is to how hard it pushes out, or its pressure. There is a "stiffest possible" equation of state consistent with causality (the speed of sound of disturbances in the fluid is equal to the speed of light). This is what they use to make their interface. Such a fluid has fascinating properties and is the subject of a lot of attention right now, but no one really knows of any such substance or what its microscopic physics might be. Therefore a lot of guesswork goes into any numerical estimates they might suggest.
Third, their gravastars are extremely cold and don't seem as if they would be useful for the types of processes that astrophysicists typically invoke Black Holes to explain. Black Holes are conjectured to be responsible for a wide array of highly energetic processes that we see in the Universe, and these gravastars just don't seem as if they would even be stable in such situations.
Last, if you go to http://arXiv.org and search for this paper, you will see that it has been revised five times since it was originally submitted. It isn't unusual for papers to be revised, even that many times, but I know that some of the revisions are due to calculational errors.
The paper is entertaining and has some neat ideas, but is in all likelihood not the way things are. There is a movement among some condensed matter physicists who claim that the principles of CM physics are actually fundamental and should form the basis for any consistent model of gravity and particle physics. This paper is a nod in that direction. While some ideas from CM might find fruitful application in high energy physics, it doesn't seem likely that phenomena at the Planck scale (where quantum gravitational effects become important) will benefit from them.
Just another failure of imagination (Score:2)
Remember, the Universe is not only stranger than we image, it is stranger than we *can imagine*!
ttyl
Farrell
bunk (Score:2, Insightful)
Nobody can see inside, so it's anybody's calculated guess. The two main problems with the current theory are singularities and entropy.
Personally, I'm not a huge fan of singularities. I think it's a cop-out to say, "at some point, all the known laws of space-time break down, and that's that." Many people seem to be of the same mindset, including the authors of this paper. They suggest that at some point, the collapse of the black hole is balanced by some quantum force. Now, if I recall correctly, didn't Hawking already suggest this himself?
As for entropy, Hawking wrote that black holes emit radiation by sucking up nearby anti-particles. I've never understood why black holes should statistically acquire more anti-particles than particles, but then again, nobody understands the statistical nature of matter vs. antimatter anyway. I'll take his word that the math works.
This paper amounts to little more than a comparison between black holes and Condensate, and considering that condensate is near-absolute COLD and black holes are something akin to absolute HOT, I think it's a pretty immature analogy.
The paper isn't even published. Why are we talking about it?
taste terrific with cream cheese (Score:2)
Ok, this has got to be about the dumbest comment I've seen tacked on the end of a story.
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Re:Sighns in the heavens (Score:5, Funny)
First Corollary to Skirwan's First Law of Creationism: Skirwan's First Law of Creationism provides direct support for creationism.
Second Corollary to Skirwan's First Law of Creationism: Evidence designed to contradict Skirwan's First Law of Creationism does not exist. The nonexistence of such evidence provides direct support for creationism.
In related news:
--
Damn the Emperor!
Re:Sighns in the heavens (Score:2)
Re:Sighns in the heavens (Score:2)
Damn the Emperor!
Actually they already have (Score:2)
Re:Actually they already have (Score:2, Informative)
They are just building the new accelerator for trying to do so. Micro Black Holes, just made from two atoms. They hope that they get the Hawkins radiation detected to see that it is a black hole.
The implication to have made a black hole would be that we have several further dimensions in the scale of a millimeter(besides the standard 3 dimensions we all *see*).
There are several
Regards,
angel'o'sphere
Re:Mass of light? (Score:2)
What doubts do you have? That's one of the central results of Special Relativity, and so far we have failed to disprove it. It is also used to predict the energy yield of nuclear reactions, where m is the "mass defect" - the difference in mass between the reactant(s) and the product(s).
Einstein had a hard time convincing people because relativity was so radically different from Newtonian mechanics. In fact, it was because of this that he did not receive the Nobel Prize for relativity - he got it for his work on the photo-electric effect. Relativity was simply too radical a departure from the accepted state of Physics.
Cheers,
Tim
Re:No more wormholes? (Score:2)
Re:Singularities can't form no matter what happens (Score:2)
Re:Beware... I hunger! (Score:2)
"RUN, COWARD! HAHAHAHAHAH"
You had to "mine" stars by shooting them to collect bits of smart missiles to smack sinistar with and the movement model was like "Thrust".
I think the original is in a Williams arcade pack for the pc they made ages ago: you also got defender, some defender sequal and a lamo bonus game where you walked round as an insect/teapot/some J Random Surreal thing and avoided stuff and collected other stuff.
And yes, I've been up for 25 hours, can't type and have 50 karma, so I don't care.
graspee