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Black Holes' Growth Measured
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.
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]
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
I think, therefore thoughts exist. Ego is just an impression.
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. :-)
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.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.
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
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.
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.
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.
Yes, but there's a limit. When its temperature approaches zero, growth rate does not approach infinity; it approaches constant. Or so I think.
--
Industrial space for lease in Flatlandia.
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.
:-)
:-) 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.
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
Cheers,
Tim
It's official. Most of you are morons.
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
Troc's dubious podcast and blog: http://www.trocnet.net
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.
"If one is really a superior person, the fact is likely to leak out without too much assistance" -- John Andrew Holmes
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.
"If one is really a superior person, the fact is likely to leak out without too much assistance" -- John Andrew Holmes
IANAP, but I had heard that certain scientists had predicted that Blackholes could lose mass/shrink/dissappear due to microwave emissions.
/. physicists. --
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
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.
My apologies to Stephen Hawking for stealing the title (as best I remember it) of a chapter of "A Brief History of Time".
;-)
:-)
/. who appreciate the occasional change of pace from computer topics.
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 (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
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?
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
========================
63,000 bugs in the code, 63,000 bugs,
ya get 1 whacked with a service pack,
--- Grow a pair, liberals... stop letting the Republicans bully 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".
Mea navis aericumbens anguillis abundat
(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.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
-rpl
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...
Stay up hacking each weekend. Sleep is for the week.
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.
Trees can't go dancing
So do them a big favor
Pretend dancing stinks!
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.)
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....