black holes

[joetommasi]

Let's see how this comes up.
Black holes are not black, they are actually invisible and the only way to "see" one is to look at how the stars around it shift.
Let me explain
A black hole bends any light that gets near it. If light from a star behind it is bent, it would appear as if the light came from a different direction. That change would make the black hole disapper hence, black holes are invisible.

[GOURDHEAD]

Rather than the black hole disappearing (tha's its irrevocable state) the star would appear to experience erratic proper motion as it is occulted by the black hole as seen from earth (or anywhere else). Also the likelihood of gravitational lensing may make the star appear brighter for a short interval of time.

[setiman]

h34r: Well how about the alternative theory that Black Holes are really high-speed tunnels to another Universe? This theory says there are many Universes, but we cannot see them unless we zip through a Black Hole.

Related to this is Dark Matter which we are seeing splattered around our Universe. Actually under the theory above, these are exit points of Black Holes from other Universes.

We will know all of this is true when finally an alien in his space ship is deposited in our Universe. He was on his way to a frapple game (something like soccer) when he got nailed by a BH. By the way, he thinks we are really funny looking.

setiman

[Prime]

The opinion has been expressed by Einstiein and others that the concept of motion, although applicable molecular and corpusular fluids, is not applicable to a homogeneous and structureless medium asthe ether.
So-Called Blackholes

Any medium that is capable of supporting wave motion, should be capable of supporting vortex motion, and it seems inconsistent after recognizing light as wave motion in the medium, to refuse to regonize the elementary particles of matter as vortex motion in the same medium.

A medium that is capable of moving would necessarily have inertia, although usually refered to as a property of matter, is a primary propery of motion.

Inertia means continuity of motion, and all motion necessarily has continuity as long as the motion contiues.

If the motion is rotation, as in a closed circuit, as in the case of vortex motion (Black Holes), then the motion will be localized inertia, or momentum.

The distinguishing characteristic of all elementary particles is their localized persistense of individuality,and this is the distinguishing characteristic of vortex motion.

Wave motion is not localized like elementary particles of matter, nor does it have individuality in the full sense of the term.

As an example, a wave that is distorted, will not of its own accord revert to its originalform, but will travel in the direction normal to the new wavefront; there being no persistence of indiduality, or memory of the original waveform.

On the other hand, if a vortex ring (Black Hole) is distorted from the circular or elliptical form, it will spontaneously revert to the original form.

The Black Hole Vortex therefore does have persistencew of individuality, or memory of its original form.

Prime

[antoniseb]

One thing I've wondered about related to black holes is this:
What happens to the Heisenberg Foam inside the Schwarzchild Radius?
Does it get swept away somehow, leaving some kind of null space?

If so, what happens during that brief moment when two black holes merge, and there is a space in between them where gravity balances out, making non-collapsed space again? Could a photon or other particle travel through this space?

[setiman]

Ah ha, a worm hole!

:unsure: Seriously, until we understand more about the force of magnetism, we are speculating. Called the weakest force, it certainly appears not to be so within the context of black holes.

setiman

[antoniseb]

Originally posted by setiman@Mar 11 2004, 02:19 AM
Until we understand more about the force of magnetism, we are speculating.

That's true setiman. Not just magnetism, either... we need to know about:
- magnetism and the mechanisms supporting it [my understanding is that all magnetism associated with a black hole must be from outside the surface].
- angular momentum inside these things, and frame dragging
- gravity [saturated Higgs field?]
- other physics in the extreme.

To have a good model for what's happening, we need to build some super instruments and measure the details of what's happening around some known black holes. Until we do that, we're spinning theoretical wheels.

[VanderL]

Is there anyone out there that thinks that black holes are not singularities and not the collapsed cores of stars?
Cheers.

[antoniseb]

Originally posted by VanderL@Mar 11 2004, 04:33 PM
Is there anyone out there that thinks that black holes are not singularities and not the collapsed cores of stars?
Cheers.

I am not convinced that a rotating object can collapse to a singularity. Perhaps they eventually use up their rotational inertia through frame-dragging or something, but I don't picture them as singularities. [Note well: My knowledge of simple physics goes out the window inside the Schwartzchild radius].

I suspect that the supermassive black holes in the centers of galaxies never had to go through a stage of being a star, but may have piled up matter so fast that they collapsed faster than light could escape.

Aside from that, I think stellar-mass black holes are collapsed cores of stars.

Are you looking to see if people think they may have a more spiritual nature?

[Tiny]

I hear my teacher once talk about this thing(BH) before, he said, there are 2 different type of BH, one was a collapse core, and another one was huge nature form BH... e.g the one that once in our Milky Way galaxy.. err am I am wrong again?

[setiman]

h34r: It is very easy to assign sinister-like behavior to Black Holes and see them as the end points of the Universe. I look at the complexity of living organisms which are essentially fashioned to be self-sustaining. I think this same kind of interactivity exists in the Universe. We see a continual renewal going on some of which is brought about by the action of Black Holes. So like I sort of facetiously wrote earlier, who is to say that BHs are not vital energy transformers that contribute to the shape and vitality of the Universe.

I am not a cosmologist so I can stupidly say that I do not believe our Universe to be self-destructive. I think the contrary applies, we have just not found out how that works yet. by the way, the most significant thing cosmoslogist say about this in a finite way is - they shrug their shoulders!

:blink: Do you know that much of what we say here has been asked, answered and argued over at the very beginning of human life on this planet? Our advantage is we have more tools to use to tease our minds. Think of Gallileo's mind when he looked through the first telescope and saw the craters on the moon? Do you suppose he envisioned a Moon Mars Mission?

Ain't this fun!?!

setiman

[VanderL]

Are you looking to see if people think they may have a more spiritual nature?

Nope, my question is meant to remind us that we know very little about these black holes. They emit X-rays and they can be found al over the Universe and some are at the centre of galaxies. Stars seem to behave strangely around these high-energy sources, but basically that's it. All the rest is pure math and conjecture. Nothing wrong in itself, but it can be very misleading to believe that what formulae tell us has anything to do with reality. We should be aware that science is a long way off from really understanding the Universe. There's a lot that remains to be explained, like how jets form and why we haven't seen any stars being swallowed up.
We should be looking at ways to recreate the X-rays and try to find ways to explain (and experimentally verify) the jets. As I said in another thread, computer modelling is a dangerous tool so we're basically out on a limb and the problem is that some people think that everything is already explained and nailed down to within a margin of error of 1%.

Cheers.

[setiman]

Well said, VanderL. I think it was President Calvin Coolidge who stated that all that will ever be invented has been invented. He was President from 1923-1929. Thanks heavens nobody believed him!

setiman

[Matthew]

Black holes are not completely invisible, black holes also release energy acording Hawking Radiation. So they are technically not invisible, but they don't emit enough to be detected by anthing but very sensitive equipment.

[VanderL]

We have to differentiate between the real black holes and the theoretical explanation of black holes. Real black holes are very visible, they are X-ray sources (Chandra and XMM images are full of them) and emit all sorts of radiation and jets. If we are looking for the theoretical constructs or "naked singularities" they are indeed practically invisible. Which is the real problem here, first we had the theory predicting singularities and next we could identify objects that might fit this theoretical model. Nowadays every strong X-ray source is equated with a black hole (or it's little brother the neutron star), but we still have to prove that these extremely strong gravitational fields really exist.Our mathematical approach and the theories that followed (Einstein in front) are way ahead of the parade in my opinion.

Cheers.

[antoniseb]

Originally posted by VanderL@Mar 12 2004, 08:39 AM
We have to differentiate between the real black holes and the theoretical explanation of black holes. Real black holes are very visible, they are X-ray sources (Chandra and XMM images are full of them) and emit all sorts of radiation and jets.

I agree with vanderL, except for this:

Our instruments are detecting emissions from the effects of the real black holes, yes; but we do not know if there are black holes out there which are not part of multiple star systems, and which are simply floating around no longer collecting significant amounts of matter, and no longer blasting lots of X-Rays.

We can detect these only by their gravitational lensing. I recall reading that a few of the microlensing events seen against the LMC were thought to be 3 to 5 solar masses, and therefore likely to be quiet balck holes. [sorry for not looking up the story, I have a deadline on something else today.]

[Duane]

Just to point pout a few descepancies.

why we haven't seen any stars being swallowed up.

Yes we have, see this: http://www.esa.int/export/esaCP/SEMUPO1PGQ...QD_index_0.html

Is there anyone out there that thinks that black holes are not singularities and not the collapsed cores of stars?

According to the Theory of Relativety, yes they are singularities. They can form from massive enough stars, but these do not account for the mid or supermassive sizes ones.

I am not convinced that a rotating object can collapse to a singularity.

Why? Why would rotation have any effect on something that massive? Or more precisely, how could rotation prevent its collapse in the face of such overwhelming mass.

My knowledge of simple physics goes out the window inside the Schwartzchild radius

Yea, same with most of us I would have to say!

I suspect that the supermassive black holes in the centers of galaxies never had to go through a stage of being a star, but may have piled up matter so fast that they collapsed faster than light could escape.

Yes, and there is evidence to suggest that they were the catalyst for galaxy formation. See this: http://www.space.com/scienceastronomy/blac...y_030128-1.html for example.

There's a lot that remains to be explained, like how jets form

See this: http://news.bbc.co.uk/1/hi/sci/tech/779707.stm
Or this: http://space.mit.edu/~hermanm/ss433/AASPre...sConference.pdf
Or this: http://www.space.com/scienceastronomy/blac...ics_021111.html
Or this: http://www.nrao.edu/pr/1999/m87/

There are lots of other sites regarding the formation of black holes, their detection, how they cause weird things like gravitatinal lensing, x-ray emission, frame dragging, etc.

I like the theory of black holes because it is simple (as compared to other theories trying to explain the same phenomenum), it is observable, and it is re-creatable. Just because a theory is hard to understand doesn't mean it is wrong. If you have evidence that fits the picture of what is known already better, then present it.

A naked sigularity would be an amazing thing indeed, in a universe filled with matter. Yet it is postulated that such a thing might arise right here on earth--if a giant super-collider is built, the crashing togeather of atomic nuclei might impart enough energy to create one for a few billionths of a second.

It is very easy to say "thats wrong". Thats what everyone told Columbus, and Gallileo, and Newton, and Planck, and Darwin, etc etc, ad infinitum, ad nauseum. Which is fine, as far as it goes. Scientists should be made to explain themselves. But if you are going to say "thats wrong", then come up with at least some reason why.

As for black holes, I think that there is plenty of observational data to support their theoretical existance. Plug the words "black hole" into your favourite search engine and start reading.

[antoniseb]

Originally posted by Duane@Mar 12 2004, 02:57 PM

I am not convinced that a rotating object can collapse to a singularity.

Why? Why would rotation have any effect on something that massive? Or more precisely, how could rotation prevent its collapse in the face of such overwhelming mass.

My concern about rotation and singularities is that I have a belief I'm having trouble ignoring in the conservation of angular momentum, and this is at odds with the apparent need for faster-than-light instantaneous velocities inside the Schwarzchild radius.

I suppose, since all bets on physics are off inside there, it could simply ignore conservation and just collapse.

Regardless of what I think about rotation and singularities, you and I are both on the same page about it being a good clean way to test general relativity. The day is coming when we'll be able to observe some of these objects in enough detail that we will better know how physics is changed in their vicinity.

[VanderL]

And I'm apparently on a different page, because there still is no direct evidence (direct, as in measuring in situ, or recreating the same conditions in a laboratory)of high gravity fields. And the star that was swallowed up wasn't directly imaged, there was just a (yes, indeed) blast of X-rays detected.
The jets are only modelled on computers (which can generate anything you want it to) and there is a lot of data unexplained in even the best fitting models. It would be nice to have a better term than "black hole" because this way it looks as if there is no doubt on what it consists of, and there are other models that are trying to explain what makes an object act like a black hole, but it isn't proven yet. So in the end we need to be careful when we make statements based on mathematical concepts, it could very well be different in reality.
Cheers.

[Duane]

because there still is no direct evidence (direct, as in measuring in situ

Not true. See this: http://www.aas.org/publications/baas/v32n3...ead2000/332.htm
Or this: http://arxiv.org/abs/astro-ph/9911273
Or this: http://science.msfc.nasa.gov/newhome/headl...st24mar97_1.htm
or this: http://hubblesite.org/discoveries/10th/vau...lackholes.shtml
or this: http://www.sns.ias.edu/~dpsaltis/ASTRO541/oct2.pdf

I could list a dozen more if you like.

And the star that was swallowed up wasn't directly imaged, there was just a (yes, indeed) blast of X-rays detected.

Well ok. Hmm lets see, they have not seen the nucleus of an atom. Does that mean it's not there? They haven't seen an asteroid strike on any terrestrial planet. Does that mean they don't happen? The star involved was approximately 1 solar mass at a distance of some millions of light years. Notwithstanding that distance, the tidal disruption of the star behaved in exactly the way it was predicted. How is that for observation matching theory?

The jets are only modelled on computers

Again, not true. See this: http://universe.gsfc.nasa.gov/press/2002/021003a.html

It would be nice to have a better term than "black hole"

I agree, but not for the reasons you state. The name came from someone trying to explain the phenomenum to a layperson (I can probably find the name, but I don't have the time right now) and the name "black hole" was so compelling, it stuck. And there is no doubt of what it consists of, the doubt is what happens to the material that it is made up of once the mass necessary to trap light was exceeded.

String theory is starting to unravel even that mystery. While there is certainly more to be learned about black holes, if the evidence for or against their existance was presented to any reasonable jury anywhere, it would easily be found that the preponderence of the evidence would support the premise that they exist.

So in the end we need to be careful when we make statements based on mathematical concepts, it could very well be different in reality

I agree! But having said that, when the overwhelming bulk of evidence supports in reality was has been postulated in theory, then you have to consider that the theory was correct. The fact that our knowledge in incomplete is what drives the continued research. If we knew everything, we wouldn''t have to look anymore.

[VanderL]

I could list a dozen more if you like.

That's exactly what everyone is doing now, confirming the models, if you look carefully there are a lot of assumptions that went into the models which cannot be shown directly (the intense gravitational fields?). In every article there is a plethora of mights and maybes that should make us pause and realise that there is a lot more to do. And your questions like

they have not seen the nucleus of an atom. Does that mean it's not there? They haven't seen an asteroid strike on any terrestrial planet. Does that mean they don't happen?

Are technically speaking answered by a yes. That doesn't mean that models are untrue per sé, but if it isn't conclusively shown to be true (the closest thing is imaged or directly measured/probed) there is always the possibility that we assume wrong. The data we use to show that black holes are composed of collapsed matter with such a strong gravitational field that light cannot escape it, are circumstantial evidence, we should never forget that.
Sorry about what I said about the jets, you're right, they have been imaged. What I meant was that their behaviour is not explained using the current models (unless you count computer modelling).
And I remain very skeptic on what a black hole consists of until they can show me that matter can really collapse. And please don't start with string theory yet, let them brood on that for a while and come up with real testable predictions.

when the overwhelming bulk of evidence supports in reality was has been postulated in theory, then you have to consider that the theory was correct. The fact that our knowledge in incomplete is what drives the continued research. If we knew everything, we wouldn''t have to look anymore.

Never forget to question the underlying assumptions; can the data be explained in other ways as well. And you're right, if we knew everything we can stop looking. But we also have to make sure that we don't walk into the trap of complacency.

Assume nothing.

Cheers.

[Tim Thompson]

Originally posted by VanderL@Mar 12 2004, 03:48 PM
And I'm apparently on a different page, because there still is no direct evidence (direct, as in measuring in situ, or recreating the same conditions in a laboratory) of high gravity fields.
[ ... ]
The jets are only modelled on computers (which can generate anything you want it to)
[ ... ]
So in the end we need to be careful when we make statements based on mathematical concepts, it could very well be different in reality.

But it is impossible to reproduce the gravitational field of a black hole in situ. It is impossible to recreate the circumstances of matter falling into a black hole in a laboratory. I think this statement reveals a fundamental misconception about what science is all about. It implies that scientific theories are somehow subject to "proof" in the same sense as a theorem in mathematics. But in fact scientific theories cannot be proven, they can only be shown to be consistent with observation. Eventually, when enough consistencies are shown, scientists become convinced, and speak of a theory being "proven", but that's a scientific colloquialism more than anything.

What we should really be asking is whether or not the mathematical predictions (or retrodictions), are truly consistent with observation. In this case, the singularity is predicted by theory to be fundamentally invisible (the cosmic censorship hypothesis, which says that naked singularities cannot happen). But all black holes will have an event horizon, and that's the real key to looking for consistency.

Supermassive objects that are not black holes invariably have solid surfaces. But the general relativistic black hole is truly unique, it has no surface. The observational characteristic of a black hole is its event horizon, a true "horizon", beyond which no events of any kind can be observed. More than anything else, the event horizon is the "edge of the universe", because as far as theory is concerned, nothing that enters a black hole can truly be said to be "in the universe" at all (at least that's how I would say it).

Here are several examples where the authors set forth evidence that this difference between a real, solid surface, and the event horizon, have been observed.

Evidence for the black hole event horizon
R. Narayan
Astronomy & Geophysics 44(6): 22-26, December 2003
ABSTRACT: Astronomers have discovered many candidate black holes in X-ray binaries and in the nuclei of galaxies. The candidate objects are too massive to be neutron stars and for this reason they are considered to be black holes. While the evidence based on mass is certainly strong, there is no proof yet that any of the objects possesses the defining characteristic of a black hole, namely an event horizon. Type I X-ray bursts, which are the result of thermonuclear explosions when gas accretes on to the surface of a compact star, may provide important evidence in this regard. Type I bursts are commonly observed in accreting neutron stars, which have surfaces, but have never been seen in accreting black hole candidates. It is argued that the lack of bursts in black hole candidates is compelling evidence that these objects do not have surfaces. The objects must therefore possess event horizons.

Observing the effects of the event horizon in black holes
C. Done C & M. Gierlinski
Monthly Notices of the Royal Astronomical Society 342(4): 1041-1055, July 11, 2003
ABSTRACT: The key difference between neutron stars and black holes is the presence/absence of a solid surface. Recent attempts to detect this difference have concentrated on the quiescent luminosity, but here these sources are faint and difficult to observe. Instead we look at these sources when they are bright , and show that there is a clear difference between black holes and neutron stars in the evolution of their X-ray spectra, which is due to the presence of a surface in the case of neutron stars. We also show that there is a type of X-ray spectrum that is only seen from black holes, making it a good diagnostic for the nature of new transient sources.

On the lack of type I X-ray bursts in black hole X-ray binaries: Evidence for the event horizon?
R. Narayan & J.S. Heyl
Astrophysical Journal 574(2): L139-L142, Part 2, August 1, 2002
ABSTRACT: Type I X-ray bursts are very common in neutron star X-ray binaries, but no type I burst has been seen in the dozen or so binaries in which the accreting compact star is too massive to be a neutron star and is therefore identified as a black hole candidate. We have carried out a global linear stability analysis of the accumulating fuel on the surface of a compact star to identify the conditions under which thermonuclear bursts are triggered. Our analysis, which improves on previous calculations, reproduces the gross observational trends of bursts in neutron star systems. It further shows that, if black hole candidates have surfaces, they would very likely exhibit instabilities similar to those that lead to type I bursts on neutron stars. The lack of bursts in black hole candidates is thus significant and indicates that these objects have event horizons. We discuss possible caveats to this conclusion.

Dying pulse trains in Cygnus XR-1: Evidence for an event horizon?
J.F. Dolan
Publications of the Astronomical Society of the Pacific 113(786): 974-982, August 2001
ABSTRACT: The X-ray-emitting component in the Cyg XR-1/HDE 226868 system is a leading candidate for identification as a stellar-mass-sized black hole. The detection of an event horizon surrounding the point singularity in such a system would constitute a positive identification of a black hole as predicted by general relativity. One signature of such an event horizon would be the existence of dying pulse trains emitted by material spiraling into the event horizon from the last stable orbit around the black hole. We observed the Cyg XR-1 system at three different epochs in a 1400-3000 Angstrom bandpass with 0.1 ms time resolution using the Hubble Space Telescope's High Speed Photometer. Repeated excursions of the detected flux by more than 3 sigma above the mean are present in the UV flux with an FWHM of 1-10 ms. If any of these excursions are pulses of radiation produced in the system (and not just stochastic variability associated with the Poisson distribution of detected photon arrival times), then this short a timescale requires that the pulses originate in the accretion disk around Cyg XR-1. Two series of pulses with characteristics similar to those expected from dying pulse trains were detected in 3 hr of observation.

And here is a dissenting opinion, the only one I have found thus far.

No observational proof of the black-hole event-horizon
M.A. Abramowicz, W. Kluzniak & J.P. Lasota
Astronomy and Astrophysics 396(3): L31-L34, December 2002
ABSTRACT: Recently, several ways of verifying the existence of black-hole horizons have been proposed. We show here that most of these suggestions are irrelevant to the problem of the horizon, at best they can rule out the presence of conventional baryonic matter in the outer layers of black-hole candidates. More generally, we argue that it is fundamentally impossible to detect in electromagnetic radiation direct evidence for the presence of a black-hole horizon. This applies also to future observations, which would trace very accurately the details of the space-time metric of a body suspected of being a black hole. Specific solutions of Einsteins's equations lack an event horizon, and yet are indistinguishable in their electromagnetic signature from Schwarzschild black holes.

This paper does not, unfortunately, reference either of the two papers above, by Dolan and by Naryan & Heyl. I suspect the argument might apply to the former, but not the latter. The argument based on type I X-ray bursts does not depend on the particulars of Einstein's equations near the black hole, but rather on the more fundamental (and simple) issue of whether or not there is a hard surface in the way of the infalling material.

If the claims made hold up, and they look OK to me, then we have more direct evidence indicating the one thing that really makes black holes stand out, the event horizon. But the event horizon is a purely mathematical conjecture from general relativity, a thing which cannot ever be made in a laboratory, or directly observed "in situ" at all. Its presence can only be inferred by remote sensing, as done here. Does that make it a weak argument? I don't think so. It certainly does not make it an unscientific argument.

In fact, making statements based on purely mathematical concepts is a necessary part of doing science. The trick is to understand the relationship between mathematics and observation. Observation can be used to support (but never to "prove") a mathematical conjecture. Mathematics, on the other hand, can act as a guide to the observations that are more important to make. Science is all about inference from observation, whether the observation is made in a laboratory or mathematically is not really relevant. Its how we test the inference made from the observation, and how that observation becomes a part of the theory making process that really counts.

[damienpaul]

Wow Dr. T (sorry Tim, I kind have stuck on calling you that) you just answered 2 of my students' and my own questions. and in your final paragraph:

In fact, making statements based on purely mathematical concepts is a necessary part of doing science. The trick is to understand the relationship between mathematics and observation. Observation can be used to support (but never to "prove") a mathematical conjecture.

is exactly what we teach in class! so it is reassuring to get some reassurance such as you are reassuring...

[VanderL]

In fact, making statements based on purely mathematical concepts is a necessary part of doing science. The trick is to understand the relationship between mathematics and observation. Observation can be used to support (but never to "prove") a mathematical conjecture. Mathematics, on the other hand, can act as a guide to the observations that are more important to make. Science is all about inference from observation, whether the observation is made in a laboratory or mathematically is not really relevant. Its how we test the inference made from the observation, and how that observation becomes a part of the theory making process that really counts.

Absolutely no arguments there, the only problem I have with the concept of a black hole is that there are too many assumptions that are not directly verifiable like you say:

But it is impossible to reproduce the gravitational field of a black hole in situ. It is impossible to recreate the circumstances of matter falling into a black hole in a laboratory

this just means that we should be aware that our models rely on those assumptions.

More than anything else, the event horizon is the "edge of the universe", because as far as theory is concerned, nothing that enters a black hole can truly be said to be "in the universe" at all (at least that's how I would say it).

And there's what I see as the problem in a nutshell, we place stuff outside our ability to measure or probe directly and then build our theories around them. We should be careful when we do that, and always keep the possibility open that things might be different then we assumed (and say so in our publications, as is mostly done except for science reviewers and journalists).

Cheers.

[setiman]

One of the real delights and useful tools of science is the hypothesis. Many if not most are designed to disprove rather than prove. In the disproving process important and sometimes unrelated discoveries are made that really advance science. Keep in mind that a lot of the mathematical and physical laws we take for granted, are still really theory and so as we creep out into space we may get surprises that will change what we think we know.

Einstein was THE questing beast who remained unfulfilled in answering questions (his and ours) about the nature of things. He was happiest when he was unfulfilled. Another great questing beast was Richard Feynman, he is regarded as Einsteins successor. He was, by the way, the scientist that proved the cause of the Challenger disaster over a glass of ice water and two rubber o-rings. He died three months later of stomach cancer. He was in incredible pain during the entire investigation of the Challenger disaster.

[Algenon the mouse]

I like to refer to black holes as the "sharks" of science. Many people fear them and few people understand them.


Many physicists have felt very uncomfortable with trying to explain black holes because of the many exotic properties they exhibit that do not follow ordinary space-time and our laws of physics, especially near the event horizon of a black hole.

I believe that it was Stephen Hawking who has proposed a theory of quantum gravity to try and explain the singularites hidden behind the event horizon of a black hole. I have no idea if the research on this is finished. I read about it when it was still incomplete a few years ago.

[joetommasi]

Could a black hole be a universe or better still could our universe be a black hole in another "universe"?
Let's play with this.
Assuming the big bang is real and there was an "explosion" that created our universe, that could be considered the supernova that creates a black hole.
The universe seems to be expanding into nothing, maybe the nothing is just the "space" in the other "universe".
Because of the compression that creates a black hole, the "density" of a black hole must be very high. In our universe a wave going through it has a velocity of 186 000 miles/hour.
Like I said, Let's play with this.

[Sp1ke]

Because of the compression that creates a black hole, the "density" of a black hole must be very high

It's not just very high, it's infinite. The mass of a black hole is compressed to zero size. This is a tricky idea to get your head round

I've heard several theories that propose multiple universes. The one I like (for aesthetic rather than scientific reasons) is that every black hole in our universe has a counterpart white hole in another universe.

Another way of looking at things is at the quantum level where every possible state change spawns a new universe. So maybe all the basic constants in our universe are *just right* because we're here observing them whereas the "neighbouring" universes where they aren't quite right only existed for a very short time, because their constants weren't right.

[VanderL]

Keep in mind that a lot of the mathematical and physical laws we take for granted, are still really theory and so as we creep out into space we may get surprises that will change what we think we know.

Couldn't agree with you more, especially the part "what we think we know", bring on the surprises!

Cheers.

[Sp1ke]

Since we're doubting the existence of black holes, what is the alternative? If a star stops shining so that there is no resistance to its collapse, it will shrink to a certain size. At this point, the nuclear repulsive forces will resist any further collapse. That gives you a neutron star.

Then what if the star started out big enough that its own weight will exceed the nuclear forces? It will continue to collapse further. So what stops it collapsing into an infinitely small space? Is there some force that can resist any amount of gravitational collapse?

I can't really imagine the formation of a black hole but I find it harder to imagine any other option. Even if the star is rotating, this just adds centripetal force as another resistance to the collapse. Maybe if the centripetal force increases quicker as the object shrinks, it might always reach an equilibrium before it forms a black hole? That might avoid black holes ever forming. I presume the maths doesn't work out, otherwise the black hole theory would have been thrown out long ago.