Doubting the Existence of Black Holes

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.

Comments

Neutron stars

[Cally]

Would that be rather like neutron stars? My understanding is that current orthodox astrophysics models meutron stars as either a Bose-Einstein state, or as (in effect) a single, very big, neutron. (Or, er, are those the same things?) C'mon astrophysicists, enquiring idiots want to know! ;)

Re:Neutron stars

[EllisDees]

IANAAP, but they are not really the same thing. A neutron star is under so much gravitation that it has had its electrons physically pulled into the nucleus of its atoms, where they combine with the protons to form neutrons, leaving only a giant pile of neutrons. A Bose-Einstein state is when atomic motion slows down enough that the wavelike properties of matter become apparent over the particle-like properties. I suppose that in the center of a black hole, since there is theoretically no possibility of motion, something like a Bose-Einstein state makes sense over just collapsing to a point, even if we still can't 'see' it.

Re:Neutron stars

[DullTrev]

I'd guess the main problem is that the term black hole and what it represents have become fairly entrenched in the English language, and it's easier to use a different term to describe a different model.
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.

Perhaps someone could explain...

[CaptainAlbert]

...whether a theory, unifying the gravitational force with the other three fundamental forces, would be at odds with the existence of black holes?

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?

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...

[awol]

The whole inescapability of black holes is somewhat spurious. There is (and I think my source here is a book called "The Physics of Science Fiction") a fairly laymans explanation of how if one can "blow off" more than half ones mass when within the event horizon then one will escape the event horizon. This is at least what the maths shows. Clearly existence alone is pretty tricky within the event horizon, but it would seem more feasible for particles (although how one achieves the "blowing off" is unclear, although it just means projecting the mass towards the singularity) than organisms or vehicles so it might still be consistent with all of the above :-)

Re:Perhaps someone could explain...

[Cryptimus]

...whether a theory, unifying the gravitational force with the other three fundamental forces, would be at odds with the existence of black holes?

Superstring theory isn't. Indeed, black holes are said to have fundamental attributes such as charge and spin which make them sound very similar to elemental particles. Some superstring theorists have produced a model whereby a brane wrapped around a spatial tear methematically produces the kind of gravity field associated with a black hole.

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.

This is symptomatic of the fundamental incompatibility between Relativity and Quantum mechanics. Relativity relies upon smooth space-time which is true at a macro level, however at the quantum level space-time seethes with activity.

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?

IANAP (I am not a physicist) but I believe most of the messenger particles (photons, gluons and the as yet hypothetical graviton) are massless. The weak guage bosons have mass. However this is where my ignorance rears it's ugly head. Black holes supposedly trap light due to the extreme curvature of space they create. (Or their extreme gravitational field). However if light (being an electromagnetic phenomenon) is massless, how can the graviton interact with it? So which is it? Does light fail to escape a black hole because space is curved (Relativity) or because of the interaction with an extreme amount of gravitons? (Standard model).

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.

That effect's a weird quantum exchange. Basically a pair of virtual particles are created (as is normal in empty space - think of it as quantum foam), the black hole sucks one of the pair in and gives it's twin a kick out away from the event horizon. The one that is sucked in annihilates when it hits the mass of the black hole . I'm not sure if it creates a resulting photon or not, this whole quantum 'borrowing' thing is fascinating but way beyond my ken.

Which just goes to show that a little knowledge is a dangerous thing. :)

I know the feeling. The more I learn the more questions I have, however I've got this sinking feeling that I don't know anywhere near enough to ask intelligent questions.

Re:Perhaps someone could explain...

[p3d0]

Are you sure? The event horizon is nothing more than the distance at which escape velocity is the speed of light. That prevents ballistic escape from behind the black hole, but as far as I can tell, it doesn't prevent powered escape.

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.

Not a good idea to post before publishing

[Neurotensor]

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:Bose-Einstein Condensates and Black Holes

[Dances with Sheep]

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)

Brought up several weeks back

[praedor]

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:just semantics

[Anonymous Coward]

Its just semantics. And not even published semantics at that.

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

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

On the other end of theories... Article

[jpiterak]

Here is another article from ScienceNews (great layman's magazine for a weekly overview of interesting science research)...

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!