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Space

Black Holes' Growth Measured 100

Posted by timothy from the not-pritikin dept.
Tei'ehm Teuw writes: "In an article from NASA@Today.gov, astronomers are concluding that monstrous black holes weren't simply born big but instead grew on a measured diet of gas and stars controlled by their host galaxies in the early formative years of the universe. These results, gleaned from a NASA Hubble Space Telescope census of more than 30 galaxies, are painting a broad picture of a galaxy's evolution and its long and intimate relationship with its central giant black hole. Though much more analysis remains, an initial look at Hubble evidence favors the idea that titanic black holes co-evolved with the galaxy by trapping a surprisingly exact percentage of the mass of the central hub of stars and gas in a galaxy." This seems an affront to my simplistic understanding of black hole behavior, but heck, we're not even sure black holes exist, anyhow.
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Black Holes Growth Measured More

Black Holes Growth Measured

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  • It's not an article, it's a press release - designed to inform the public (the 'pao' in the URL is short for 'Public Affairs Office') about research projects at NASA.

    If you want peer review, I suggest attending the 196th meeting of the American Astronomical Society in Rochester, NY where the results will be presented. You can probably even pick up a hard copy of the paper while you're there.

    Oh, and that link in the original post should be 'Today@Nasa.gov'

  • I think Hawking predicted evaporation of black holes through a QM effect, there's still not much evidence for it. If black holes do exist, they will ertainly grow if you drop stuff into them.

    If black hole evaporation does happen, they will be the perfect power souce - apart from being a little dangerous, that is.

    As for those microwaves - as I recall they relied on some specially prepared gas, which certainly wouldn't exist inside the event horizon. I'd certainly pay to see someone try the experiment though.

  • Does this mean there are black holes in the center? Not really - even if they could see through the dust cloud a tiny black hole wouldn't be visible

    They can't actually prove the existence/non-existence of black holes, but they can determine whether mass exists in a sufficiently small volume in the center of the galaxy to create black holes based on the popular theories. That is, they can say "If the theories are correct, there is a black hole in the center of the galaxy."

  • Re:growing or shrinking? (Score:3)

    by ubergeek ( 91912 ) on Monday June 05, 2000 @10:36PM (#1023365)
    Black holes do in fact lose mass to Hawking radiation, but the amount of energy/mass lost to this effect is so fantastically small that any infalling objects/energy more than makes up for it. The "evaporation" of black holes through Hawking radiation doesn't become a significant effect until the hole approaches microscopic sizes, simply because evaporation time is proportional to the mass of the hole cubed. For a black hole of roughly 30 solar masses that has no infalling matter it would take 10^61 times the age of the universe to evaporate. Black holes with mass less than 10^11 kg can evaporate in less than the age of the universe. [Ref] [colorado.edu]
    Hawking radiation isn't really energy escaping the black hole as that is not allowed for by their very definition. The event horizon is defined as the point at which the curvature of space-time becomes so great that not even photons can escape its pull (not a strict definition I know, but a functional one at least).
    HR is actually something which occurs on the "surface" of the black hole, at the event horizon. It involves Heisenberg's uncertainty principle, and particle/anti-particle pairs as I undertand it, but would not venture an explanation as I am sure it would be sorely inadequate.
    As far as photons travelling at a velocity greater than c, I don't know what to say. I'm under the impression that our current understanding of physics indicates that superluminous velocities under any circumstance breaks a lot of what we think we know about the universe (especially special relativity and I think parts of general relativity). What effect that would have on black holes (their very existence in particular) I wouldn't want to guess.

  • There is only one gigantic white hole, the Big Bang itself.

    Without matter to feed it, it would be borne out of nowhere. Existence would be but a gigantic debt. That debt is being paid by black holes sucking matter out of space/time and right back into Big Bang. That's why they are so dense; they are the most true thing we'll ever meet.

    Eventually, all matter will be either consumed by black holes or left out as warmth. There is no hope for Earth. Though it will be dead and gone long before. *gives the finger downward*

    This way, Universe serves as the ultimate self-feeding heater.

    Sorry, I had to :) Thanks for the discussion, it's a great read otherwise.
  • Is it just me or does it seem like we are being fed information when NASA deems fit. I am not a conspiracy theorist in any means, although it does seem odd that regularily we are given information that perhaps I just have a feeling was found out a while back. Until Carl Sagan and Stephen Hawking many people were kept well out of the loop as to what we knew about Science and Space and now it seems more and more likely that someone is censoring just how much we can know about what is found. I'm not talking about alien lifeforms and habitable planets, but more along the lines of just basic space theories and proofs. Why do we have to wait so long for so little information. I just doesn't make any sense to me...

  • All scientific knowledge is supposed to be tentative, and if pressed I'm sure that most scientists would say, "no, we don't really know whether black holes exist, it's just the best theory that we have (and it is a very good theory)." But when statements like this "big black holes" press release come out, it doesn't even look remotely like the ideas are tentative. Here they discuss some of the finer points of the personal life of black holes -- is the reader supposed to understand this in the context that we don't actually know whether the things exist at all? Not very likely, is it?

    Now, I realise that putting a standard disclaimer on every scientific statement to the effect that "this is only the best theory we have and may in fact be a load of phlogiston," is inconvenient to say the least, but I think we could do with the occasional reminder. There seems to be a pervasive attitude that science is the single best mechanism to determine facts about the physical universe (as opposed to moral truths, for example), and thus it doesn't really matter that our theories may be wildly inaccurate because they are by definition the best knowledge that we have. Perhaps it is the best knowledge that we have, but to my way of thinking that should demonstrate that our best isn't very good at the moment. It concerns me that we talk about big bangs and black holes with such great confidence when the hard evidence is so thin. In a century from now these theories might be as credible as the tooth fairy theory of tooth to coin transformation: how much faith should we put in them?

    I'd feel a lot more at ease if we could in general be a little more honest about the amount of stuff we don't know in any particular subject. This is a pervasive issue; black holes just happen to be a case in point at the moment.

  • Big Bang is currently the ONLY theory that can plausibly explain Microwave Background and the abundance of deuterium.

    And in particular, the new inflationary model of the early universe, whereby the curvature of the universe suddenly reduces from a very high figure to the current value of almost exactly zero, in about 10^-30s starting about 10^-34s after the beginning of the universe. These times a little odd in that they're defined within the curved coordinate system of the early universe (and I might have misremembered the orders of magnitude).
  • Hell the big bang theory as initially proposed has been proved wrong many times

    Which is why the theory has been revised numerous times since it was initially proposed. That's why it's a theory. It's a "best guess" kinda thing. There are plenty of physicists who dispute the big bang. There are plenty who agree. Cosmology is not a subject physicists take lightly. The Big Bang theory is just the best-fit right now. It wasn't always the prevailing theory, and if someone offers a more plausible or reasonable explanation, over time that'll become part of the favored TOE. This stuff never happens overnight anyway. You compare to the last days of steady-state...maybe these are the last days of Big Bang and/or Standard Model.

    Personally, I think Black Holes are just a mighty-cool idea. Something so dense it messes with space-time...that just sounds neat.


    ----

  • The evidence was that space is flat. Spacetime is still curved. Furthermore, this is on average; locally dense concentrations of matter (like stars) can still bend light.

    As for Yilmaz's no-black-holes result, his work is pretty shoddy as was discussed in the comments to the article at the time, and also on the sci.physics.relativity newsgroup.

    Light can't travel faster than the speed of light; it's just poor reporting on the difference between phase and group velocities.

    The latest article didn't say that supernovae can't produce black holes, it just said that the black holes in the centers of galaxies are produced by the same mechanisms involved in producing the galaxies. This has nothing to do with individual stellar-mass black holes.

  • When I read "A Breif History of Time" I had a question about this. What makes all the negative particles fall in and the positive ones fall out? Wouldn't it work the other way around about half the time? Then wouldn't that mean that the black hole isn't really going to radiate anything at all?

    My guess is that this theory is a bit deeper than this, or that the way that S.H presented it is more of an analogy, but still, I'm curious.

  • What makes all the negative particles fall in and the positive ones fall out?

    It's one of those bizarre quantum effects, as I understand it. Basically, the pair comes into existance, and you know that one has positive energy and the other negative (note, not to be confused with positive or negative charge!), but you don't know which. Once one falls into the black hole, the probability waveform collpases such that the one with negative energy is the one that fell in, because the universe doesn't allow the reverse to happen.

    I'll confess that I'm going from memory here, though, and don't have time to reference my copy of A Brief History of Time, so if anyone can correct me, please do.

  • Note, though, that when most people talk about "black holes" they're referring to the whole shebang -- ie, not just the singularity but the region of spacetime around it, extending out to the event horizon. It makes no sense to talk about only the singularity, since it is perpetually hidden ("nature abhors a naked singularity"). Just to be picky. :-)

    Also, note that in principle one could use the bending of light around a massive black hole to estimate its mass. (You've no doubt heard all about such "gravitational lenses," but less well-known is the fact that it's possible to get a mass estimate from such objects by looking at precisely how the light "bends.") This sort of measurement has been done for, eg, clusters of galaxies, but the masses involved are far, far larger than those in even supermassive BHs -- it's also a difficult measurement, fraught with possible errors.

    just my 2 cents. :-)

  • Subject says it all. To whomever moderated the above, thoughtful post as flaimbait, I can't wait to nail your sorry ass in meta-moderation.
  • So ever since I was a little tyke, I have thought about this, it's obvious isn't it? We have seen no limits in the down size, why the up size? An atom has a center and some thingies spinning around it. A Planet has moons, a star has planets, a galexy has stars, a universe has galexies. As far as we know quarks probably have some middle part with thingies spinning around it, and the Universe probably has a very dence center part that all of these galexies are moving around. All of these nuclii seem to work around some sort of gravitational principal so it would make sense that a galexy would need a center bit. We have always seen big bright centers in galexies, and we know of the possabilities of black holes. So does it not make sense that all of those stars and all of that mass in the galexy would compress there in the middle? I want to see what is in the middle of the universe, then I want to see the other universes. Hmm... maybe I'm still dreaming and I haven't had coffee yet.

    -Effendi
  • As the photon has no rest mass, it is pure energy, and so with its energy reduced to zero, it has effectively "destroyed" itself in its efforts to escape the event horizon.

    I thought that the reason light couldn't escape the black hole's grasp was because the mass of the black hole had stretched the local space/time curvature so much, that the light was essentially going around in circles inside the black hole's event horizon, not that the gravity of the black hole was directly "attracting" the photons.

    Of course IANAP.
  • The trick is that near a black hole, sometimes these particle pairs sap energy from the black hole, and at least one of the particles becomes "real". You could imagine the other particle falls into the hole or something...

    Weelll...not exactly. IIRC, one of the virtual particles crosses over the event horizon; if it happens to be an anti-matter particle, then a matter particle "appears" near the edge of the black hole.

    I was wondering about quantum entanglement. It appears these days that two particles can be "entangled" even though they are an arbitrary distance apart, and that measuring the state of one collapses the state of the other. Now: what would happen if you started off with 2 entangled particles and one went into the black hole before you measured the state of the other. Since the masive gravitational forces at the event horizon would presumably "destroy" the first particle (i.e. strip away its identity) before you measured the second one, what would be the result? Would the second particle change in any particular way -- say, be a fermion when it started out a boson, for example? What if they were photons? This is just a Gedankenexperiment, but I'd like to hear someone speculate on this.

  • What the %&#@ hell are you thinking?!?!?!!?!?!

    Do squirrels reside in your *&^#^ skull???

    You, to clarify a bit, have stated that the Big Bang theory is incorrect, as it cannot explain everything in the entire *&@#$ universe. This is like stating that the theory of gravity is incorrect because it fails to explain the abscence of unicorns (source: Scott Adams)

    Perhaps we should throw out your argument altogether, as it does not explain the 19 separate grammatical errors in your post. (There may be more, specifically if uncapitalizing Big Bang counts as one.)

    Let me explain a tenet of science to you for the benefit of the hallucinating squirrels that run your brain. A scientific theory may be proved wrong in ONE aspect, but that does not mean that ALL aspects of the theory are invalid! This happens many times in science, especially with stuff we don't know that much about! Do you want to throw out the 'theory of evolution' as well? Scientific theories must constantly be updated to fit the new data that emerges, in contrast to the case of organized religion. (They can break whatever rules they want, because they have an omnipotent God who can smite the hell out of all of us.) Yes, aspects of the Big Bang theory have been proven false, but as with all theories, amended to fit the new data. Now stop making inane posts and go feed those squirrels before they get cranky.

  • Does this doctor type in all caps and insist that Einstein was the biggest conman of history? Okay, probably not, but there is this Dr. Amed... excuse me DR. AMED SYEN or something like that who also clutters up the String theory forum with spam.

    And I doubt it's the grant money that really bothers these guys... at worst it would be the realization that their lives' work was worthless.

    Although, it is hard to argue there isn't a 'popular' opinion in the scientific community. Big Bang works remarkably well, except that we don't know all of the ingredients yet, so it's hard to use any predicting power.

  • Generically, it is any n-dimensional space where
    n > 3. In the context of relativity, it is
    usually the four-dimensional thing also known as
    space-time.
  • Why would the organizations that provide grants
    for these things not provide grants for research
    into well-founded alternate theories? It's not
    like there's a big profit to be made by pushing
    Einsteinian mechanics on an unsuspecting populace.
  • Yes, that's correct

    If an object has a high density the gravitational field strength around it will be strong enough that there is a stable circular orbit outside the object with an orbital velocity of the speed of light, which is the exact definition of the event horizon for a nonrotating blackhole (other definitions apply for rotating blackholes).

    The existence of an event horizon means that a blackhole is present, whether or not the blackhole contains a singularity.

  • Read this:

    Black Holes: One Size Doesn't Fit All [stsci.edu]

    The actual black hole is so small that there's no way they could measure a small enough volume. A if the popular theory is correct, it's pretty much a certainty the black holes exist - large supernovas should leave enough "dead" debris behind to form one.

    AFAIK, it's just very difficult to tell the difference between a black hole and a very massive, dark object.

  • Anyone can upload a text file to a web server.

    But not onto the NASA server.
  • Not exactly. Its hard to see how the mass of a black hole could increase as the universe expanded, although as the curvature of the universe decreased the volume of the black hole would increase.

    Primordial black holes are (theoretically) local regions of space time where the expansion did not happen as quickly as for the rest of the universe, leaving a small region where the gravitational energy density was high enough for it to remain a black hole.
  • Which is what I wish schools would teach (in England they don't unless your lucky enough to have a good teacher who actually understands the philosophy of science).

    In my school education we were always taught science as absolute fact, at least until the age of 16, without any reference to the concept of theories and experimental tests of theories. Given that most people in England stop their scientific education at 16, it's not surprising that the public does not understand the methods of the way of looking at universe around us that we call science.
  • About 3 months ago I thought I was pretty advanced in my knowledge of astrophysics (for a person who has never formally studied it)

    Then they decide that the univserse is flat, ie gravity doesn't bend light (yet what about the two guys who looked at stars during an eclipse and saw them bent?)

    Then I hear that there are no such things as black holes because Albert E didn't add the energy produced by the energy into the equation. The result somehow being very dense neuron stars, but no possibility of black holes.

    Then I hear light can travel faster then the speed of light.

    And now black holes, that don't exist or bend light, and even if it could bend light the light could travel about 300 times faster then itself to get away, aren't caused by supernova's but just by gradual gas eating?

    When we've all worked out what the hell is actually happening somebody let me know, until then I don't think I'll worry about it.
  • Yes, but there's a limit. When its temperature approaches zero, growth rate does not approach infinity; it approaches constant. Or so I think.
    --
  • hear, hear... cheers patrick

  • Re:growing or shrinking? (Score:4)

    by Tim C ( 15259 ) on Tuesday June 06, 2000 @03:35AM (#1023391)
    Sorry, but that's just plain wrong. Any particle created within the event horizon must be created with sufficient kinetic energy to overcome the force of gravity and escape the potential well of the hole.

    The reason that we cannot see black holes optically, is that light does not have sufficient kinetic energy to escape the gravitaitonal field at a distance outside the event horizon. What you propose here is that particles are created that have supra-light velocity; this is expressly forbidden by relativity.

    You are on the right track, however :-)

    The theory is that, due to quantum effects, a matter/anti-matter particle pair can spontaneously be created near the event horizon. (This happens in ordinary space all the time, and is permitted by energy conservation, over short time scales).

    If the pair is created at the right distance from the horizon, then it is possible that one particle will have sufficient energy to escape, while the other (travelling in the opposite direction) is swallowed by the hole.

    It turns out (ie don't ask me to do the maths :-) that it is the particle with positive energy that escapes, and the one with negative energy that is swallowed. Thus, the net total energy of the hole is reduced, and due to energy-mass equivalnce, it's mass is reduced.

    Cheers,

    Tim

  • Re:growing or shrinking? (Score:3)

    by troc ( 3606 ) <troc@@@mac...com> on Tuesday June 06, 2000 @12:17AM (#1023392) Homepage Journal
    The theory is something like this:

    It's been postulated that just within the 'event horizon' of a black hole (that point at which even light cannot normally escape the gravitational field), a complex particle could decay into constituent particles under the forces around it...... these constituent particles will then zoom away from each other due to the energy released and it's possible for one or many of these particles to leave the black hole before its gravity has slowed the particles sufficiently to suck them back down.

    It's kinda like here on Earth - I can throw a ball up in the air and it'll fall down again and if I throw it nearly fast enough to leave the gravitational pull, it'll get hearly all the way our and then fall back again... so if I make a special ball that's designed to break in two at or near the top of it's flight and fire the two sections in opposite directions (one up and one down), then the top section now has enough velocity to escape.....

    This is partially how/why multiple stage rockets are better then single stage ones in certain circumstances.....

    troc
  • Hm, I think I would have been surprised if the opposite had been announced. After all, the dominant theory for the central engine of quasars is that they have a supermassive (larger than 10^6 solar masses (why isn't the SUP element supported by /., BTW?)) black hole in the center, and an accretion disk around it with infalling matter. This infalling matter isn't going anywhere, so as it falls into the black hole, the black hole becomes bigger. Now, this is a pretty fast process, Hawking radiation, mentioned by others here, is a pretty slow process, so that a black hole gains mass is not at all surprising.

    As for the existence of black holes, well, it is the nature (and the funny part) of astronomy that ideas come and go, some ideas havea great impact some have not.

  • Re:Black holes ain't so black (Score:3)

    by / ( 33804 ) on Tuesday June 06, 2000 @03:55AM (#1023394)
    IIRC, Hawking radiation is kept around as an explanation as to why we're not bombarded with microscopic black holes formed during the big bang, more than as an explanation of how a typical run-of-the-mill black hole should shrink over time. When you think about it, you'd have to win an unreasonable number of coin tosses for the antiparticle to get swallowed enough times for a regular black hole to evaporate completely.
  • Correct me if I'm wrong, but NASA isn't the Fount of All Cosomological Knowledge. Scientists in lots of research organisations discover lots of things about the universe all the time, and then publish in the journals and conferences. The reason that information comes through little bits at a time is that it is discovered little bits at a time. People like Hawkings aren't revealing things that are already known, but publishing new information/theories that NASA find out about at the same time. If you want to get information quicker, contribute to the discovery of it by becoming a cosmologist. Science was open-source long before software was ;)
  • Are we saying that something very, very small has a large amount of power over it's immediate environment?

    Is this not already happening on our own mother earth with politicians or companies who abuse their power?

    Maybe we could solve two problems at once here, fire all those who disregard employees/public/customers into the nearest black hole thus increasing it's mass, thus destroying it?

    -Scientifically poppycock but somehow soothing to the soul...
  • To whomever moderated the above post (the parent of this one) as "Offtopic":

    WAKE UP!!!

    Try reading the post before moderating it. Now I've had to waste one of my mod-points on modding it back up.

    Way to go.

    --
    "Give him head?" ... "Be a beacon?"

    "One World, one Web, one Program" - Microsoft Ad
  • Out of curiousity, is your thesis available online or in a journal somewhere?

    No, unfortunately not. I wrote it 10 years ago, at that time even in academic circles the IN wasn't used as much as today and it wasn't a PhD-thesis anyway. I used the universities IN-connection mainly for public domain sw for my Amiga :-).

    This brings me to one of my favorite true computer anecdotes.

    I was sitting in the computer room, besides me a Prof. This Prof used the computer very seldomly, therefore he didnt need/want his own. His assistant however had his own and was an experienced user. For example, he convinced some computers used for teaching at day to do some simulations for him at night ;-). Anyway, the Prof was swearing because the computer kicked him out again and again.
    Then his assistant came looking for him, quite excitedly, "Prof, Prof, somebody must have stolen our password! What a persistent bastard, I had to kick him out three times!"
  • Damn it all! I can't mod and post in the same thread.

    Christ, now I'm *really* pissed at whoever moderated that post down...

    I'm going to go to the local pub (The Mad Hatter, sort of like THAT MODERATOR) to eat 25 cent wings. Lots of them.

    --
    "Give him head?" ... "Be a beacon?"

    "One World, one Web, one Program" - Microsoft Ad
  • Which is exactly what I wish they wouldn't teach in school. Once you propose using morality instead of science (though it isn't absolutely objective), you then have to choose a moral theory to teach (since most people are too biased or self-righteous or just unable to teach all moral theories concurrently). Teaching morality, especially when it blurs with religion, is precisely what we shouldn't have government engaged in doing. That, and I challenge you to come up with a moral theory that predicts anything at all about super-massive astronomical objects.

    If you're just asking for them to teach Kuhn's theories and the rest, then I still think that'd be premature in most high schools. People have to develop a world view first before you can completely decimate it, or else they get turned off to the whole enterprise and all progress stops. That's what college is for.
  • For those who would like to know more about quantum mechanics:

    Pbs website [pbs.org]

    A very good book titled "Who's Afraid of Schrodinger's Cat [amazon.com]"

  • IANAP, but I had heard that certain scientists had predicted that Blackholes could lose mass/shrink/dissappear due to microwave emissions.

    I guess now astrophysicists can accept that they don't shrink after all. They get HUGE!

    I wonder if the new microwaves that travel 300x the speed of light can pass beyond the event horizon of a black hole? Since they could escape the black hole to begin with, I guess this is possible.

    Please enlighten me Oh great /. physicists. --
  • I thought that the reason light couldn't escape the black hole's grasp was because the mass of the black hole had stretched the local space/time curvature so much, that the light was essentially going around in circles inside the black hole's event horizon, not that the gravity of the black hole was directly "attracting" the photons.

    Light can orbit a black hole at the event horizon because at that radius the attraction from the black hole is exactly enough to keep a particle in orbit at the speed of light. It is no different than the much less massive Earth's gravity keeping a satellite in orbit at a much lower speed. Light inside the event horizon however does not stay in orbit, and cannot escape as the gravitational force at that distance requires an escape velocity greater than the speed of light.

    Then again, perhaps matter inside the event horizon does orbit something. The point is we cannot detect that due to the aforementioned escape velocity. Einstein postulated that information itself can travel no faster than the speed of light, so if the evidence of an orbit cannot escape, it can be argued not to exist.

  • Owwwww! That hurt my brain.

    ..and I haven't even begun to figure out how that is analogous to the microwaves thing, other than through real and perceived speed... I want a an analogy that relates to the physical process occuring....

    I never was quite clear wrt how the phase velocity could be different than the packet velocity... but it's been a while...

    You see, I'm a *visualization* person, and I mean visualization on the minute physical level. Simply presenting the calculus and saying 'see, this is how it turns out' is not what I'm asking for. I want to visualize how the physics of the system is interacting to create the behaviour described by the mathematics.

    In my 1st year physics course it took me two full hours of hard thinking about the applicatoin of linear conservation of momentum to the particle force dynamics in a spinning object in order to visualize just what physical processes created the effects shown by gyroscopes (the right hand rule) and such...

    The best description for this is "mentally integrating the physical principles" instead of mathematically doing it. It was rewarding when I finally got there. Much nicer than simply accepting the math and observation and saying "it is so".

  • Black holes do behave a bit more like ordinary objects than most know... Not only do they grow and shrink (thanks to some quantum trickery), but they also aren't black...

    In fact, the reason we know they exist is that they actually radiate energy. Their methodical evaporation causes flashes of X-rays to pulse out...

    I always thought it was a weird kind of doublethink that black holes were thought to be rather static while the universe has to come from a single point of mass and energy... but I still don't know all the math yet, so it's hard to tell for sure.

  • So do black holes then have a measurable volume and mass? I'd heard their volume shrinks to nothing as their mass continues to grow, bringing their density to infinity, although I'm certainly not a quantum-physicist.
    Anyone?



    --
  • Light can orbit a black hole at the event horizon because at that radius the attraction from the black hole is exactly enough to keep a particle in orbit at the speed of light.

    I thought light was massless, and you therefore can't treat it like a particle w/mass orbiting a gravitational source - you have to analyze it in the context of the curvature of space/time which it is traveling through (to the LIGHT, it looks like it's always traveling in a straight line, but due to the curvature of space/time due to the gravitational effects, the light might end up going in circles around the hole, kind of like one of those coin-circling-the-hole playthings @ various malls, except w/o friction).

    Of course, if I remember the basic concepts of general relativity correctly, you can treat EVERYTHING, mass or massless, in the context of curvature of space/time (and even "massless" objects kind of have mass-equivalent, by virtue of whatever energy they contain, so perhaps the whole debate is moot :)

    BTW, if a photon has "mass"-behavior by virtue of the energy it contains at a point in space/time, and photons can cross each other w/o interference, and you managed to get a whole bunch of high-energy photons to cross @ the same point in space/time, could you cause a large enough bend in space/time to rip a hole in it? :)

  • For the longest time Steven Hawking advocated the existence of white holes (so called for their inverse relation to black holes as dumping grounds of matter of which black holes feed). I wonder if there is a way to determine where exactly in hyperspace these could be traced to based on the location and growth rate of the black holes. Also isn't there a possible danger in having say the black hole in the center of our galaxy consume our own? Will the black hole evaporate before it destroys the galaxy?
  • Which isn't remotely what I said.

    Presenting science as absolute truth is wrong, and a lie. Saying that the best idea we have at the moment is so and so, and these experiments agree with it, is an accurate representation of the way that science works, and this is how it should be taught.

    Science was presented at my school in such a way that there was no way within science to discuss past and present theories, and that once a theory has been tested once it is absolutely correct. Since science at school before the age of 16 was mostly conservation/ecology this doesn't seem the correct way to go about this sort of thing.

    Helpfully, my school science teachers were so crap that I taught physics to my teacher at the age of 15.

  • Shouldn't this kind of article have evidence?

    And where's the peer review? Anyone can upload a text file to a web server.

    Oh, fine, an FTP server, but still. You get what I mean.

    I just don't see what makes this credible.

  • Now who's the one in need of mod points? -grin-

    --
  • Um... I don't think the 300-times c microwaves really exist... It's probably one of those quantum probability tricks that crops up from time to time.

  • A black hole is a singularity, meaning that all the matter/energy stuck in it is confined to a single point in space. Basically the force of gravity has become so strong in the localized area that it overcomes all other forces, squishing all of the particles into a single point in space. One can measure the mass of this singularity by observing the gravitational effect it has on nearby bodies.

    The singularity has no volume whatsoever, and as density is defined as mass/volume, the density of a black hole is undefined. One can say that the density of a black hole in formation approaches infinity as all the particles move into smaller and smaller spaces.

  • to do with the radiation. The radiation is caused by the particles fighting to escape from the gravity and expelling a great deal of their energy in the form of X-rays... Conservation of mass does enter the picture when we speak of virtual to real particles, entropy and evaporation though...
  • slowly radiate at a temperature which is inversely proportional to its surface area

    I don't know too much about this subject, but it sounds like you're saying that as it absorbs more background radiation and grows larger, its radiation temperature will actually grow cooler? So does that mean that the larger it grows, the less its radiation will counteract its growth so the faster it will grow larger?
  • Uhhhh...

    cd /dev
    ls -s null
    0 null

    Well, it looks like /dev/null is zero bytes in size. I measured it.
  • I don't know too much about this, but aren't there theories that say "if there's this much mass within this much volume or less, a black hole either exists or will form"?

  • Hey, that's where I live!

    Uh, do you have any details about stuff like location, perhaps?

    This could be really interesting. Thanks so much!

  • Black holes ain't so black (Score:3)

    by tbo ( 35008 ) on Monday June 05, 2000 @09:45PM (#1023420) Journal
    My apologies to Stephen Hawking for stealing the title (as best I remember it) of a chapter of "A Brief History of Time".

    IAAPS (I Am A Physics Student, though somewhat rusty at the moment ;-)

    Black holes can shrink (this is not to say they must shrink). While it may seem impossible, since matter and energy can not escape the event horizon of a black hole, black holes do radiate energy. Some other law of physics (pertaining to black body radiation, IIRC) requires that black holes radiate a certain minimum amount of energy, causing Hawking (and others) to ponder how this could be. Quantum mechanics provides a solution.

    Space, even a perfect vacuum, is not devoid of matter. Although a perfect vacuum has an average energy of zero, this is only an average. Quantum mechanics allows for the spontaneous creation of "virtual" particle-antiparticle pairs, which quickly annihilate each other (virtual because they are annihilated before they ever interact with other matter). I forget the details, but the more energy such a pair has, the shorter the amount of time it can exist for--there's a Planck constant in there somewhere :-)

    The trick is that near a black hole, sometimes these particle pairs sap energy from the black hole, and at least one of the particles becomes "real". You could imagine the other particle falls into the hole or something...

    As for the article about Yilmaz's version of General Relativity [washington.edu] (which predicts the non-existance of black holes), I don't yet know enough to criticize his General Relativity on the basis of the mathematics or theoretical physics. AFAIK, most of the "observations" of black holes have simply been of the motion of stars perturbed by massive, relatively dark objects, or of radiation thrown from the disk of material spiraling into a massive black hole candidate. I don't see why a small, massive (non-black hole) object as predicted by Yilmaz couldn't have been responsible for all these effects.

    Do I think Yilmaz is right? Probably not, but it would be pretty damn cool if he is. I admire the guts of physicists who do "monkey wrench physics", and dare to challenge the established theories.

    Please don't flame me if I've blown some of the details; I haven't done a physics course for over a year (I've been working on the comp sci half of my degree). I would appreciate any corrections or additions, though. I hope there are lots of other physics geeks on /. who appreciate the occasional change of pace from computer topics.
  • As far as photons travelling at a velocity greater than c, I don't know what to say.
    I know. They don't.

    It is very easy to achieve a superluminal phase velocity, but it doesn't help very much, as phase doesn't transfer energy, matter, or information.

    Here's how to make something "travel" FTL. Take a powerful laser. Aim it at the moon. Power on. Sweep across, rapidly. The lightspot will cross the moon surface faster than light. It is extremely useless.

    Here's another method. Take two sheets of metal. In one of them, drill 1000000 small holes 1 micron apart, all on one straight line. In another, drill 1000000 holes 0.999999 micron apart, all on one straight line. Now if you put these two sheets so that the two straight lines coincide, you will see one small hole. All other holes will be obscured. Now if you move one sheet relative to the other along this line, you will see a "hole" that moves 1000000 times faster than the sheet. (In reality, you will see 1000000 distinct holes open up in a rapid succession.) So if velocity of the sheet is 500 m/s, then "velocity" of the "hole" is faster than light. This is extremely useless too.

    In both cases you see phase extrema moving FTL, not real objects.
    --

  • Yes, the math does yield infinities, but it doesn't break down. A new technique needs to be created to handle this problem, much like l'hopital's rule came up in Calc I(and later if you ever had to apply anything you learned) Some times it takes a long time to manipulate math til it works. Super Strings(string theory or whatever you wish to call it) is working on new maths to make this work. We'll see what happens
  • Dr J.V.Narlikar has written numerous articles on how there exists a self serving cliche in the international astrophysics community who have a vested interest in receiving grnts for the study of black holes and the big bang theory.

    A quick search only found one such article. This seemed more to be about the grants for large technical undertakins. I would imagine there would be quite a public outcry if we poured millions into gadgets that we think will fail. I can only speak about theoretical physics in Germany. Here, when you are a Professor you can research anything you want, your money is garantied. So, you will research something that interests you and where you think you will be able to make progress, maybe breakthroughs. Lets say you believe in the general theory of relativity, but think it possible there is an alternative. Obviously finding a workable alternative (maybe even one with new predictions) gives you much more fame then improvements on the existing theories. Think about the famous theoretical physicists: Almost all found new theories and broke away from the established physics of the time.

    So the question is just: Do you believe an alternative theory is so improbable, that the huge fame you would get for it doesnt outweigh this improbability?

    they are introducing artificial quantities like dark matter and an anti gravitational effect of free space

    I dont see dark matter as artificial. Just the opposite: I would be very surprised if we could clearly "see" all the different forms of matter in the universe.

    I say scrap the Big Bang theory

    If you can, then do it.
    Its funny you bring this up, since my "Diplom-arbeit" (masters thesis?) went in that direction. As you probably know, general relativity has not yet been quantized. However, one can speculate on effects of QM on relativity. There are reasons that in a quasi-classical theory it leads to higher-order lagrangians. Since there are many possibilities and since there are anti gravitational effects, one can well believe that the universe once just was very small, but not singular. However, both theoretical arguments and computational simulation show the singularity. BTW, after I started on this, I also found an article that had done very similar things with the same conclusion in "nuovo cimento" (sp?).
    Of couse I dont say that my work prooved the big bang. But its very difficult (I believe: impossible) to scrap it. But you are, of course, welcome to try.

    **Life is too short to be serious**

    Ah, so its just a hoax that you think everything is a hoax ;-) ?
  • white holes (so called for their inverse relation to black holes as dumping grounds of matter of which black holes feed).

    I believe that this is an excellent example of the racism which pervades today's scientific community. While in many other facets of life, Blacks are the same as Whites, in science, specifically physics, you claim that Black holes are bloated consumers, while White holes are the ones producing everything. This is a very disturbing additude for a professional physicist, such as Steven Hawking, to be taking. Although he might have grown up in a time when it was 'OK' to do this, today it isn't.

    Will the black hole evaporate before it destroys the galaxy?

    This seems to be an obvious statement that Blacks are going to destroy all that we hold good unless Whites can kill all of them. I believe that this kind of statement is horrible and detrimental to the community as a whole. The entire issue is that we need to measure and accomidate for the Black holes, not just try to kill them. I think that it is outrageous that you refuse Black holes the right to survive, while you accomidate for White holes. Who do you think we are?
  • In an article from NASA@Today.gov [nasa.gov], astronomers are concluding that monstrous black holes weren't simply born big but instead grew on a measured diet of gas and stars controlled by their host galaxies in the early formative years of the universe...

    They just figured out that huge black holes aren't born, they're grown?

    Oh come on, I have a book in my library, "The Universe And Beyond", by Terence Dickinson, who describes the way in which quasars and large black holes grow in mass by consuming gas and stars. This book was first printed in 1986.

    I knew this the moment I knew quasars were thought of as large black holes. It's quite simple and logical.

    Over billions of years, monstrous black holes - either the ones at the centers of galaxies, or the quasars found in "emperor" (usually superdence eliptical) galaxies, are fed by the inward spiral of gas, rocks and stars. Quasars are obviously formed by a game of Galactic Darwinism in which one bigger black hole swallows another and adds it to its own mass, and they also feed on stars like crazy, drawing even big or fast moving stars nearby, into a degenerate orbit. Stars and gas.

    I knew this ages ago. C'mon. This ain't news :) Although the concrete evidence may be the news here, the concept is not.

    ========================
    63,000 bugs in the code, 63,000 bugs,
    ya get 1 whacked with a service pack,
  • It is just you.

    Most of the scientists involved in NASA projects do not work for NASA, they are affiliated with colleges and universities. They publish their papers through the normal academic channels. NASA does not review or control the publication of these papers.

    NASA managers like it when a project results in large numbers of published papers. They view it as a rough "figure of merit" for the science produced by a project.

    You don't read about the vast majority of the scientific results because they are too difficult for the layman or non-specialist to understand. Besides, how many people would want to read "Comparison of scintillation, spread F and electrostatic probe observations of electron density irregularities".

  • As far as photons travelling at a velocity greater than c, I don't know what to say.

    I know. They don't.

    Read Feynman's book on QED. Renormalization tends to take care of the cases where photons travel faster than light by cancelling their amplitudes with photons that travel slower than light. The result is that we observe light travelling at a fixed speed, c, in a vacuum. That dosn't mean that under very odd conditions the final probablility for a photon to travel faster than c isn't zero.

    Anomalous: inconsistent with or deviating from what is usual, normal, or expected
  • dude, just stop giving the astronomers beans for breakfast and they'll be docile.
  • I added a few more exclamation marks to your subject heading--I gather that every 6 marks is worth a moderation point.

    I knew this the moment I knew quasars were thought of as large black holes. It's quite simple and logical.

    You would have been an excellent student of Aristotle.

    In modern science one generally requires convincing evidence before incorporating a hypothesis into one's worldview. Even then, alternative hypotheses are admissible provided they also explain the data. (One simply holds both to be "possibly true" and one waits for an experiment or observation that disproves one or the other hypothesis). Disproving a competing theory--such as, for instance, evidence that disproves the notion of quasars as enormous starbursts--does not necessarily prove a theory (in this case, big vociferous black holes that gobble everything that comes near).

    I knew this ages ago. C'mon. This ain't news :) Although the concrete evidence may be the news here, the concept is not.

    By that token, if someone proved the existence of a Creator figure you would consider it to be not newsworthy as well, since the concept itself is far from new.

    I suspect that you and I disagree on the meaning of the words "to know." Just because it is printed in a book does not necessarily make it true. (I should know--I've written a book where some of my speculation has since been disproved. :) Physics would be so much easier to do if it weren't for those pesky observations and experiments...).
  • Well yeah that's what I was meaning - I was just trying to say it in a more accessible way.

    And failing I guess. Explaining things was never one of my strong points.

    Probably why I became and engineer :)

    cheers

    troc

  • I think a lot of the discussion on this article is missing some crucial evidence that we need to take into consideration. Specifically, that Black holes don't actaully have a mass, size, or "surface area."

    Most people have the idea that black holes are either large "drains" in space or some large spherical body that sucks everything in. That is not true. Black holes are singularities. What that means is still debatable. But it also means that:

    • Size
      The size of a black hole is best described as the "radius" of the event horizon. I am sure most of us have heard of the event horizon (the point where light and mass cannot escape). What is behind the event horizon is not known.
    • Surface Area
      There is no real analoge for the surface area a black hole. Consequently, there is no true volume as well. This is because singularities are thought to be infinitly small (0-dimentional, like a point) and infinitly dense.
    • Mass
      This is the main error everyone makes when talking about a black hole. Remember, Astronomy is an observational science. Astronomers cannot pick up a black hole and weight it on a scale (like a physicist may to to find the mass). Instead, in astronomy, mass is found be measuring the speed of objects flying around the black hole(the acresion disk), then determining the rotation curve of the mass around the black hole. Think of a rotation curve as graph with the distance along the x-axis and the speed of the objects along the y-axis. With the rotation curve you can try to fit the curve to a known gravitational potential. This gravitational potention allows you to find the "mass" of the object everything is rotating about.
      What this means is that the actaul object inside (if it was a star or something) would have that mass. But since we know that black holes are infinitly small and infinitly dense, that wouldn't make sense. So when we say that the "mass" of a black hole is X, then we mean that there is an object inside the acresion disk that results in the objects rotating the black hole to have such-and-such velocity curve. That object (if it were a star) would have a mass of X.

    I hope that helps clears things up.

    PS I am not a physicist or an astronomer yet. I am currently receiving my undergraduate degree in both.

  • (disclaimer) I haven't read the original paper, only the Analog precise' of it. It's been months since I read the article, and decades since I actively studied physics, so use a large crystal of NaCl. (/disclaimer)

    IIRC, Yilmaz's GR says that *singularities* don't exist because the graviational field itself will counterbalance collapse past a certain point, not that event horizons/black holes can't exist. The minimum stellar mass required to form a black hole will increase, but that's only an issue with the remnants of supernovae, not galactic black holes.

    The best analogy is probably the "speed limit" imposed by SR. Your mass increases as you approach the speed of light, so a fixed amount of extra momentum or energy gives you an increasingly smaller increase in velocity. The increase is just enough that it requires an infinite amount of energy to reach c.

    Likewise, as I understand Yilmaz's GR spacetime itself will resist further collapse with increasing force as the gravitational gradient increases. To actually pierce spacetime (singularity) requires an infinite amount of mass. This has happened exactly once - the big bang.

    Even if I misunderstood/misrecall Yilmaz's predictions and it really does prevent the phase change that occurs at the event horizon, this is a difference that has little effect outside of the traditional event horizon. You're still talking about an incredibly high gravitational field and gradient so you'll still have profound redshifts, time dilation, frame dragging, etc. The *only* difference is that your atoms won't fall through an event horizon, they'll impact the degenerate matter on the surface of the "black hole." Big whoop.
  • Black holes do emit Hawking radiation, which over time will cause them to shrink; however, they have an effective temperature of 6x10^-8/M, where M is in solar masses. For a stellar mass black hole, that translates to roughly 10^-25 erg/s emitted from the black hole. At that rate it would take about 10^70 years for the black hole to radiate away its entire mass (discounting the fact that the temperature goes up as the mass increases, that is). So, the conclusion is that for astrophysical black holes Hawking radiation is an entirely negligible effect unless you are talking about time scales vastly longer than the present age of the universe.


    -rpl

  • Well if it went for peer review it would probably not get published unless it furthered the cause of the reviewers in getting bigger grants
  • Well, I think that most would aggree that black holes do exist. There has been alot of proof that there are highly dense objects that do not emit visible light but suck up huge quantities of matter. They still do emit other forms of energy (i believe in the form of x-rays) in order to conserve mass/energy. Just because we don't have all the answers right now about what actually occurs at a singularity, doesn't mean that black holes do not exist. At a singularity (such as a black hole or the very beginning of the universe if you believe big bang theory) relativity breaks down. The mathematics simply give uninformative results (infinities and such). We've had problems like this in the past. Einstein won a noble prize (in 1903 i think) for describing the photoelectric effect. This is the emmision of electrons from metals when they are stimulated by light. Classical physics was shown to be wrong by countless experiments and no-one before Einstein could figure out the what the correct theory was. I'm rambling here, but my point is that we will eventually find an explanation that describes phenomena such as black holes. We always do.

    -Mike Bell

  • Those poor black holes... (Score:5)

    by hypergeek ( 125182 ) on Monday June 05, 2000 @09:18PM (#1023436)
    astronomers are concluding that monstrous black holes weren't simply born big but instead grew on a measured diet of gas and stars controlled by their host galaxies in the early formative years of the universe.

    Great... I can just picture a black hole support group.

    Black Hole 1: Hi, I'm Globulax, Swallower of Galaxies... I've been a black hole for billions of years.

    Rest of Black Holes (seated on uncomfortable folding chairs): Hi, Globulax!

    Black Hole 2: It's okay... we're all Black Holes here... nobody's judging you...

    Globulax: <sniffle> Well, I wasn't born big... I was raised on a measured diet of gas and stars controlled by my host galaxy...

    Black Hole 2: Don't worry... with time, you'll learn to control your cravings...go on... it's good to let these emotions out...

    Globulax: I feel so unwanted... so unloved... even light tries to escape my event horizon... <sob>... and... and... scientists aren't sure if I even exist! Waaaaaaaaaaaaahhhhhhh!!!

    Black Hole 2: There, there. It's okay, Globulax. Come on, everybody, let's all give Globulax a big group hug!

    The Black Holes sympathetically converge near Globulax. Unfortunately, their gravity is too strong, and they swallow each other into one ultra-massive Super Hole, whose gravity gobbles up everything in the vicinity and rips a large tract of spacetime to shreds...

    Black Holes (in unison): Oops!

    Black Hole 2: Great... there go our folding chairs...

  • Blackholes are theorized to have a temperature of a few kelvin. But the universe has a background temperature in the 10s of kelvin. As long as the background temp is greater than the blackhole's temp they won't shrink.

  • As far as I can tell, what they're doing is measuring the speed of rotation at the edge of the galaxy hub, and the speed further in (the "dust trapped around the black hole"). As all the physics students among us will know, the rotational speed depends only on the radius and the mass inside the containing sphere. So they can measure the mass in the hub, compared to the mass inside the center of the hub.

    Does this mean there are black holes in the center? Not really - even if they could see through the dust cloud a tiny black hole wouldn't be visible (see the third link in the article). Black holes are just the commonly held idea, this has nothing to do with proving they exist.

    This is still very interesting research - to me it seems to mean that the mass density of galaxies has a similar profile across a huge range of sizes.

  • The comparisons of rotational velocities only works in rigid body dynamics(like a spinning sheet of cardboard or something like that.) what you're dealing with here is Gravitational Waves coming out of a massive object(I'll refrain from calling it a black hole cuz it doesn't take one) that affect the objects around them.
  • Once upon a time, in a galaxy far, far away...

    There was a /. fantasy known as Natalie Portman. She was fine, perky teen specimen, and all the open-sourcers admired her...

    One fateful eve, her spaceship (running M$ 98 of course) suddenly lost control and began careening toward the mother of all black holes...

    The mighty minds of /. strove to her rescue, and the fastest, most sturdy Linux and BSD warships sped to save her from her horrible, premature teen death... Yes, their minds may have held dreams of conquest after their heroic deads, but speed there they must...

    The first of the ships there, in fact pilotted by the first /. Portman stalker, took her into its loving tractor beam and brought her aboard.

    The /.er could not resist her temptuous teenage charms, and immediately threw himself onto her. She could not resist him for long however, as he was a great man of high ordeals and open sourced fantasies. But, as they lay back against the control panel, disaster struck, and the ship took off into the hole...

    And so, like a wave of lemmings, the /. fleet followed the ill-fated life boat of young Natalie... And after, the mammoth servers and sparkling Slashcode fell silent in remembrance of the fallen...

    But soon after, as life returned to normal, a great cry went up... 'Where did all those hot grits go? Where are the musings of illogical and impossible Beowulf clusters? Why are people only using their moderation points for good?' And then they realized. The young, tender Natalie had been sacrificed to purify the soul of Slashdot...

    Okay, sue and moderate... I'm just waiting for a bus, sheesh.

  • Not only do they grow and shrink (thanks to some quantum trickery), but they also aren't black... In fact, the reason we know they exist is that they actually radiate energy. Their methodical evaporation causes flashes of X-rays to pulse out...

    Um... I don't know about you, but I can't see X-rays. If I look at something emitting X-rays but no visible light, I say it's black.
  • That is flat out wrong. A black body is an object which does not REFLECT anything. The sun is a pretty decent black body, though it is not black. (well, it would be if you shone a bright enough light on it!)

    In this sense of the word, black holes are quite black. In the lay sense of the word, black holes are not black, but instead x-ray coloured, which the eye doesn't see very well.
  • When you consider the fact that there are black holes with millions of solar masses (i.e. millions of times the mass of our sun) it's not that suprising. No star can be 300 million solar masses, so it would figure all that matter has to come from somewhere.

  • Re:growing or shrinking? (Score:3)

    by orpheus ( 14534 ) on Monday June 05, 2000 @10:06PM (#1023444)
    There are no "300x the speed of light" microwaves. This merely an effect that 'appears' to travel faster than light. Note that the article in that story [slashdot.org] specified that the effect only occurs with certain very specifically shaped waveforms. This takes the mystery out of how the far end of the apparatus can 'reconstruct the complete waveform' when only the leading edge has had time to enter the apparatus.

    Such 'apparently faster than light' effects are not uncommon in relativistic phenomena. One example is the 'superluminal fireball' from the 80's:

    Imagine a star 1000 light years from Earth gave off a 'fireball' or giant plasma burst pointed at our planet in the year 1000 AD. For the sake of argument let's say it's travelling at 99.9% the speed of light. In the year 2000, the light, we would see the light from the explosion, and could 'watch the fireball eject'. Meanwhile, the fireball itself will travel 999 light years, and be just 1 light year from Earth. Therefore the light that the fireball gives off in 2000 will reach the Earth in 2001 (followed, four days later, by the fireball itself striking the earth, possibly doing nasty things to humanity, Linux, Natalie Portman, and other things /.ers hold dear)

    To an observer on Earth, the fireball will appear to have travelled 999x the speed of light. To an observer somewhere at right angles to the fireball's path, it will appear to travel at .999 the speed of light
  • But, if the black holes formed in the good ol' days of expansion, they could have started relatively small (since galaxies came from specs of this era) and ballooned along with everything else in the universe... essentially being their present size from birth.

    Now, if a black hole is simply a collapsed star, it does beg the question of just how far it had to order out for all of those nummy stars and nebulae... it takes a lot of space to come up with 300 million solar masses of ordinary stars.

  • Most would agree that incredibly dense celestial bodies exist that have the properties we observe in black holes. This doesn't necessarily make them singularities, which is more or less the defining definition of a black hole. If instead of a singularity it is some very dense, but not infinitely dense, form of matter, it might be consistant with all we have observed thus far while not creating the singularities wherein known physics breaks down.

  • You could imagine the other particle falls into the hole or something...

    This is in fact what Hawking predicts. The pair comes into existance and you can think of it as one of them having positive energy and the other negative. If the pair is created at just the right distance from the event horizon, one of the two will fall in and the other won't- and (I believe) the waveform collapses such that the one with negative energy is the one that fell in and the positive energy escaped, as (as far as we know) negative energy particles are not allowed in the universe.

    So, we have a new particle that has been radiated away from the black hole, and the black hole has negative energy added to it- which in essense destroys some of its mass.

  • You're right - it wasn't microwaves that were measured at this speed... I don't have the URL on hand ATM, but what they measured was the behaviour of light when traversing a cesium-gas-filled chamber. It turned out the light came out the far end before it entered the near end. Microwaves so far haven't been measured at more than a scarce few percent above light speed...
  • even though there is far more evidence of the resurrection and divinity of our Lord

    Name two.

  • link is here [sunday-times.co.uk]

    A very interesting read.. I liked the comments on geeknews [geeknews.com] (which is where the story was posted) even better. 300x the speed of light=5.5 warp speed :-)

  • Eh? (Score:1)

    by Nidhogg ( 161640 )

    Not sure they exist?

    C'mon!

    What about that big one in Redmond sucking in lawyers, oodles of cash, and system resources?

  • IIRC, Yilmaz's GR says that *singularities* don't exist because the graviational field itself will counterbalance collapse past a certain point, not that event horizons/black holes can't exist. The minimum stellar mass required to form a black hole will increase, but that's only an issue with the remnants of supernovae, not galactic black holes.

    Wouldn't that suggest that as you approach the speed of light, you'd collapse into a singularity? As I recall, the addition special relativity makes to Newtonian physics is the addition of a gamma term that multiplies mass by the inverse of the difference of velocity and the speed of light (1/(c-v)^2, I think...) It's this result that requires infinite energy to approach the speed of light, but wouldn't it also imply that achieving lightspeed would render the mass a singularity?

    Not that I consider myself competant to challenge modern physics theory, but I've never found a better way to grok than to question it. Explains why I don't do well in less Rational fields of Essential Knowledge.

    Ushers will eat latecomers.

  • You misunderstand what is meant when we say that the Universe is flat. It has no relation to the topology of the universe; right now theorists think that the actual topology could be very complicated indeed, not just that the universe is like a wraparound pac-man screen or a taurus, but that space embodies a much more complicated hypergeometrical shape.
    When scientists say the universe is flat, that's a reference to its eventual cosmological fate. An open universe has a low overall energy density and will keep accelerating outward, expanding forever, as it does not have sufficient mass for gravity to counter act expansion. A closed universe has an energy density such that the universe will eventually collapse back on itself in the Big Crunch.
    A FLAT Universe simply means that as time approaches infinity the expansion of the universe approaches zero.
    Until recently, evidence has supported an open universe (there just isn't enough mass to support any other option), while theorists have argued that the universe must be flat. Recently scientists have determined, that if, in the cosmological equations, Einstein's cosmological constant is greater than zero, the idea of a flat universe can be reconcilled. I could get into a whole thing about the cosmological constant, but since no one will probably read this anyway, I'll leave that for a later discussion.

    Wombat
    3 semesters awar from a BS in Astrophysics
    (as well as a BA in Theatre.)
  • The reason that we cannot see black holes optically, is that light does not have sufficient kinetic energy to escape the gravitaitonal field at a distance outside the event horizon

    light does not have kinetic energy. also, technically, light does escape from event horizons, they are just red shifted infinitely.
  • The theory of shrinking of the black holes predicts that the black hole can behave as a conductor of antimatter - it can create "evaporate" matter/antimatter pairs and so over long periods of time the black holes would shrink. However, to completely evaporate a black hole could take 10^70 years. The black holes grow by consuming matter (gases, dust, comets, asteroids) just like planets or stars do. At some point the growing processes will slow down due to consumption of the resources but evaporation is continuous and its speed only depends on the mass of the black hole. The mass of the black hole is huge enough so that the escape speed from the black hole's surface is greater than the speed of light (that's why light can not escape) and we agree that nothing travells faster than light (space curvature theory.) Now imagine the opposite process - evaporation takes place and after 10^70 years all of a sudden the black hole 'looses enough weight' and its escape velocity falls bellow the light speed and then ALL OF A SUDDEN a black hole becomes a small size and a huge mass very fast spinning object that you can SEE AGAIN ! Imagine being right there at that time - black unpenetrable event horizon disappears and you can see a pulsar once again! (of-course in 10^30 years all protons in our Universe will decay anyway so everything will disappear much sooner...)

  • Re:growing or shrinking? (Score:3)

    by Tim C ( 15259 ) on Tuesday June 06, 2000 @07:10AM (#1023456)
    I'll concede the first point, as I'm not entirely sure, and have no Physics texts to hand (as I'm at work :-) )

    (Although, now I think of it, the photon has momentum, and so (as the two are related), probably does have KE; I'm willing to be proved wrong, however)

    The second point, however, I feel I must contest. An infinite red-shift is identical to an infinite increase in wavelength. This is, in turn, identical to an infinite reduction in energy (the longer the wavelength of the photon, the lower its energy - E = h/lambda IIRC).

    As the photon has no rest mass, it is pure energy, and so with its energy reduced to zero, it has effectively "destroyed" itself in its efforts to escape the event horizon.

    No energy means no photon; no photon means nothing escaped :-)

    (And before anyone starts shouting, no, you can't destroy energy; I'm guessing that the energy of the photon has gone to reduce the potential energy of the gravitational field)

    Cheers,

    Tim

  • Re:growing or shrinking? (Score:4)

    by anatoli ( 74215 ) on Monday June 05, 2000 @09:21PM (#1023457) Homepage
    They can both shrink and grow.

    A black hole suspended in an absolute vacuum (no matter, no radiation, nothing) will slowly radiate at a temperature which is inversely proportional to its surface area, and thus shrink.

    Now let's say we have a black hole and an external background radiation. Black hole now absorbs radiation and grows (but still continue to shrink at the same time). If the temperature of the radiation is greater than that of black hole, the latter would grow faster than it shrinks. Now throw in some matter, and the black hole will grow even faster.

    BTW microwaves don't travel 300x the speed of light. Phase velocity can be anything you like, but phase does not "travel".
    --

  • where exactly in hyperspace these could be traced

    Maybe I'm ignorant, but what exactly is hyperspace?

  • Re:Defined mass/volume/density? (Score:4)

    by OdinsEye ( 182369 ) on Monday June 05, 2000 @09:25PM (#1023459)
    Well, there is a bit of controversy on that, I believe...

    As is, black holes have a definite, but not necessarily measurable mass... it's just the mass they started with plus the mass of whatever they have eaten and minus what has been lost to Hawking radiation.

    Now, the singularity... yes it does supposedly approach infinite density (approach is an important mathematical distinction), and is even capable of shredding the very Einsteinian laws that define it. The only reason it's tolerated, physicists say (kind of a strange reason, but I don't have the tools to judge) is because the singularity is locked away, and no information can be transmitted about it. The universe doesn't know that there's this strange point at where space-time curvature (gravity) approaches infinity.

    To make things really weird, Brian Greene added a nifty component to string theory (which is what gave him credibility for his book besides being a damned good physicist). In the 6 curled dimensions, there is a transformation was allows space to remain continuous, but plants the seed for a black hole... That folding may be part of what keeps the universe from tearing itself apart during black hole formation.

    Either way, its pretty nifty how the 'weakest' force in the universe can kick the other three's asses when enough mass is involved....

  • IIRC, the cosmic background radiation is actually
    3K, not tens of K. Or are you talking about
    something else, like maybe the radiation in the
    core of a galaxy?
  • First of all, I don't think anybody ever doubted that black holes grow. It's kind of fundamental to the definition.

    Hawking showed that black holes also shrink. (The reason why is really trippy...) As long as they grow faster than they shrink, the net effect is still growth... and the rate of shrinkage is so slow that even the cosmic background radiation is sufficient to keep them, well, in the black. Black hole shrinkage and decay will happen eventually, but not for a long, long, long, long time.

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