Slashdot Mirror
Black Holes No More -- Introducing the Gravastar
Mark Eymer observes: "From the Space.com article: 'Emil Mottola of the Los Alamos National Laboratory and Pawel Mazur of the University of South Carolina suggest that instead of a star collapsing into a pinpoint of space with virtually infinite gravity, its matter is transformed into a spherical void surrounded by "an extremely durable form of matter never before experienced on Earth."' While these objects may abound in the universe, they also say that our entire universe may reside within a giant gravastar." This new theory attempts to fill holes in the currently accepted concept of the "black hole".
An article about Grevestars showed up in Scientific American a few months back I remember...
It was an interesting article, but they seemed to be a ways off from anything solid...so to speak.
FWIW, NASA ADS returns 22 abstracts.
That search engine at http://xxx.lanl.gov/find is hard to use isn't it?
But I found these papers for Emil Mottola and these for Pawel Mazur.
Read Epic the first RPG novel.
Lee Smolin has a great book on black holes as universes and applies evolutionary theory to universe creation.
The Life of the Cosmos. Very good read.
-Shane
I love teh int4rw3b!!!!!111one1
Actually, anyone can upload papers to the archive (the main site is now at www.arXiv.org). There's no peer review involved -- that's why it's called a _preprint_ archive -- and no respectability is conferred by simply uploading a paper to it. The fact is that there's a lot of crap on arXiv (though not as much as you might expect), and there are also a lot of people who don't use arXiv.
But apart from that, your comment is irrelevant anyway since these two do have plenty of articles on the server, as seen in a previous reply to your post.
The author of this post asserts his moral rights.
For those of you with short memories, Slashdot covered the gravastar theory when it was announced last year.
See these articles:
Black Holes Disputed, 1/19/2002
Doubting the Existence of Black Holes, 3/26/2002
There must be black holes. That's how articles in the editors' database mysteriously disappear so they can be duped later.
Yes and no,
:)
IANAP either... but here it goes.
Blackholes and the like are thought to (slow and eventualy )stop time inside the Schwarzschild radius, without time theres no movement, without movement (eg excitements of atoms) you have no heat.
Bingo
Before you email me, remember: "There is no god!"
I recall reading that neutron stars are largely Bose-Einstein condensates. Yes, they have ridiculously high temperatures, but relative to the amount of matter in that tiny space, it's a very low temperature compared to what it could be. I don't understand that, I'm just parroting what I remember reading.
Allowing myself to think about that, that means that making matter denser lowers the temperature at which a Bose-Einstein condensate will form. And once you start forming it at anything over 2 degrees Kelvin, all the universe is your heat sink, so it's a stable state.
Here's another link to a similar story at Scientific American if your interested:
http://www.scientificamerican.com/article.cfm?artNo, you can't .... and for the same reason that you can't use that argument to search for black holes. The hole/gravistar itself must be very cold, but matter surrounding the hole/gravistar would be heated during infall, emitting a large amount of energy. The physics of this are quite interesting, and covered in many introductory texts in general relativity and astrophysics; search for information on "accretion disks".
They're predicting something that can't be observed. From outside the event horizon, both a point-like black hole and the sphere-like black hole will look identical. Theories that cannot be disproved are boring. Move along, nothing to see here.
From National Lampoon's Animal House amongst others.
At least I mostly forgot about this dupe before I read it.
First: Some following posts show the author didn't even do a rudimentary search of the archive let alone anything else. A place to start for example, "Where are all these zillions of states hiding in a black hole?" Mottola said in a recent article in New Scientist magazine. "It is quite literally incomprehensible." or The "unique and remarkable properties" of a gravastar "could explain several high-energy astrophysical phenomena that now are puzzling," says Marek Abramowicz, a black hole expert at Gothenburg University. Oh, and Mottola was a researcher at Los Alamos' Theoretical Division. RTFA, dude.
... yes, it was released by a very presitigious research lab.
Second: Anyone involved with the scientific community in the least, should know that peer review is actually quite a contentious issue and by no means considered as accounting for "all fault-finding".
Third: The theory itself resolves some troubling issues with black hole theory. The latter has become so fashionable that even lay men speak of them without seeming to question some of the root concepts that stretch all but a seasoned physicist's imagination. A quote from a related article: Physicists have struggled for years to account for the huge entropy of black holes, and largely have failed. Unlike their black hole counterparts, Gravastars would have a very low entropy.
Finally: This linkis to the Los Alamos release
"Consensus" in science is _always_ a political construct.
Not wanting to start any (literal) holy wars here, but the reason that Evolution is tagged as a theory is because the evidence does not provide conclusive proof. Other scientific precepts are tagged as Laws because there is consistent proof that states that this concept is always the case. Evolution and Creation are both tagged as theories. I happen to put my chips on Creation. Just remember, science cannot and does not prove or disprove the existence of God. If it did, there wouldn't be a debate. ;-)
sorry, I am a physicist and need to correct a common misconception here... time does not slow down or stop inside the event horizon of a black hole. It only APPEARS to an outside observer that this is the case. If you were to fall into a very massive black hole, you wouldn't even notice anything "different" as you crossed the event horizon and your clock would indeed still "tick". However, someone watching you fall into said hole (from the outside) would see you move slower and slower as you approached the event horizon and would observe your clock to be running "slow". At the instant you hit the event horizon, you would actually appear to "freeze", with no further updates (since you are now inside the horizon and light can not cross the boundary in the outward direction). Hope this helps!
"It takes considerable knowledge just to realize the extent of your own ignorance." - Thomas Sowell
Has he come up with anything unique? What?
Hawking came up with the idea of Hawking radiation, which is a quantum-mechanical mechanism for matter to escape from a black hole. The basic idea is this: a quantum fluctuation creates a matter/antimatter pair of particles near the event horizon of a black hole. The antiparticle falls in, destroying some of the mass of the black hole, while its partner escapes. The net effect is as if the black hole had emitted a particle.
What I don't understand about this concept is where the energy from the antiparticle annihilation gees. However, this is just limited understanding on my behalf, and I believe that Hawking radiation is a widely-accepted notion.
On a side note, it has been demonstrated that the surface area of a black hole behaves like entropy, in that it is subject to something akin to the second law of thermodynamics. Anything with entropy should have an associated temperature, and anything with a temperature should radiate. This radiation is Hawking radiation.
Tubal-Cain smokes the white owl.
Wrongo. Note that none of these preprints (dealing specifically with the gravistar concept) are peer-reviewed.
Science, like Nature, must also be tamed, with a view turned towards its preservation.
That's not Occam's Razor. Although many people make that mistake.
Occam's Razor doesn't say anything about what's likely true or not.
I don't think you understood the article. These guys are not proposing that black holes are really gravastars, without singularities; they're proposing the existence of something that is not a black hole, whch doesn't have singularities. Black holes still exist as solutions of general relativity, and any theory of quantum gravity has to deal with them (unless you quantize a theory of gravity in which black holes aren't even theoretically possible).
Besides, it's not the singularities that present a problem for quantum gravity. Even if singularities didn't exist in the theory, it would be just as hard to quantize gravity, simply because people don't know how to apply quantum theory to a gravitational theory like general relativity.
The energy from the anti-particle interacting with any matter in the black hole goes to increasing the entropy of the black hole. That's why what hawking theorized (and still works on) is called black hole entropy. Before Hawking no one thought a black hole should have entropy. But he showed how it is possible.
The black hole radiation happens exactly as you describe.
The process that you alluded to where the surface area of a black hole behaves like entropy is sort of true. The fact is, there is a direct relation to how much information that can be stored in a volume and the surface area of the volume. If you think in terms of entropy as information degradation, then the smallest unit of information equals the smallest unit of volume, which also equates to the smallest unit of entropy.
Instead of interpreting singularities to mean that black hole solutions are impossible, most gravitational physicists today interpret black hole singularities to mean that general relativity simply doesn't work on very small scales, and needs to be replaced by quantum gravity. Black holes will still exist in quantum gravity, but the singularities inside them may not.
Incidentally, it has been argued that singularities might be a desirable feature of gravitational theories.
on the subject can be found in the New Scientist journal or...here:
http://www.sciforums.com/t5376/scd6aa1f3497a9a8949 43c2c19febdb24/thread.html
You can also possibly view the Mazur and Mottola submission (preprint) at:
http://www.arxiv.org/abs/grqc/0109035
A google search on gravistars turns up several sources that are perhaps better than the space.com readers digest article.
Now people, get a hold of yourselves. Most, if not ALL, of you are fully unqualified to poo-poo the idea just as you are unqualified to critique black hole "science". It is downright stupid to poo-poo the idea and hold the classic black hole idea as sacrosanct. No one. NO ONE has seen a black hole. They are ENTIRELY ghosts of the imagination INFERRED from observations that are wholly in accordance with the idea of gravistars OR black holes.
Claiming that the idea of gravistars requires too much "hand waving" ignores the fact (stone cold fact, that is) that the idea of a black hole itself requires an incredible amount of hand waving and eye covering to get past its very real problems.
The jury is still out on black holes. If another idea accounts for the same observations while at the same time avoiding the many problems that black holes create...well, it would end up being a better theory outright. The gravistar deserves a real chance to germinate and grow on its merits and math and must not be tossed out the door on the principal that it violates the holy black hole doctrine.
In Bushworld, they struggle to keep church and state separate in Iraq as they increasingly merge the two in America.
Papers get peer-reviewed before publication (or submittal for that matter) to find flaws in them, suggest fixes for those flaws and in general serve as a check for problems large and small in the work. It doesn't always work that way in practice of course, but that's the idea. Think of it as a private beta test. Papers get peer-reviewed after publication by people who read the journal they were published in. These people will suggest/try additional experiments designed to test the hypothesis and will publicly criticize anything they don't like with widely varying degrees of politeness - "I'm underwhelmed" to "This is obviously faked data".
Also, a theory in the scientific sense is a strongly tested hypothesis that fits the data better than other models do. A lot of what people refer to as theories would, in a strictly scientific context, be considered hypotheses. Or guesses.
"Bugger this, I want a better world." - Jenny Sparks
IANAP (I am not a physicist), but another source of radiation that ive heard theorised is the it is possible/probable for a pair of particles to spontaneously form out of the vacuum of space, then collapse on themselves.
If this happens at the event horizon, one particle gets sucked in, the other particle ejected.
> I guess Steven Hawking has to cancel that Playboy subscription.
> (if you don't get it, move along. There is something to "get" and your mod points are needed elsewhere. Thank you.)
Hmmm, +2... I see we have a couple of moderators willing to pretend they get it!
Sheesh, evil *and* a jerk. -- Jade
> einstein suffered terribly in school, guess that makes him a moron too, eh?
While popular culture holds that Einstein was a drop-out, a lowly patent-office clerk, and an outsider who stood the scientific world on his head, he was in fact the equivalent of a modern PhD candidate in the last year of a PhD program. In 1900 he graduated with the equivalent of a bachelor's degree or higher, qualified to teach both math and physics at the university level. When he published his famous papers in 1905 he was what we now call an ABD ("all but dissertation"), and in fact he submitted his dissertation On a new determination of molecular dimensions that same year, earning a PhD in physics at U. Zurich.
More detail here.
Sheesh, evil *and* a jerk. -- Jade