Hidden Black Holes Discovered

mknewman wrote to mention a Space.com article discussing the discovery of a large group of hidden black holes. From the article:"Black holes cannot be seen directly, because they trap light and anything else that gets too close. But astronomers infer their presence by noting the behavior of material nearby: gas is superheated and accelerated to a significant fraction of light-speed just before it is consumed. The activity releases X-rays that escape the black hole's clutches and reveal its presence. "

Comments

Kessel Run

[Xac]

They found the Kessel system. http://www.atombender.de/swgwiki/index.php/Kessel_ System

chicken and egg..

[rd4tech]

what was there when it all started: galaxy or a black hole?

Re:chicken and egg..

[Shadowlore]

what was there when it all started: galaxy or a black hole?

Duh, a galaxy's black hole. Where do you think the term "big bang" came from?

Geek explanation required.

[pwnage]

OK, can one of you physics geeks explain to me why x-rays are able to escape the gravitational clutches of a black hole when light cannot? I've never understood this.

Re:Geek explanation required.

[Mick Ohrberg]

I think they don't really escape the black hole per se. They're just very high-frequency/high-energy radiation that leaves the super-heated gas BEFORE it 'falls over' the event horizon.

Re:Geek explanation required.

[gardyloo]

Light and x-rays are the same things (as you imply), just at differing frequencies. Visible light can escape from outside black holes' event horizons, just as easily as x-rays.
      Any electrical charge undergoing an acceleration emits radiation, if it can couple to its environment. Charges which are accelerated more emit radiation at higher frequencies, and accelerations near a black hole's event horizon are very large, so x-rays are emitted preferentially over visible light. There is also an effect of higher frequency emissions from any finitely-sized source being more "focused" than lower frequencies. This leads to more concentrated "beams" of emission from finite sources.
        Finally, one of the methods of radiation from black holes is that of spontaneous particle-antiparticle production in the tremendous gravitational gradient outside a black hole. Normally, these particle-antiparticle pairs recombine quickly. However, if one travels nearer a black hole than the other (they're emitted going in opposite directions relative to their center of mass, to combine linear momentum), it can get sucked down the gravity well, and the other escapes.

Re:Geek explanation required.

[gardyloo]

I forgot to mention one of the most imporant effects: matter which is around a black hole tends to form accretion disks. It forms disks because it tends to have a net angular momentum about the black hole's center, and so spins. The fact that differing parts of the accretion disk move at different speeds means that there is a lot of rubbing going on -- not unlike with slashdot readers. This leads to heating of the accretion disk, often up to a very high temperature; the accretion disk is just like a very hot oven, which doesn't emit (much) in the visible region, but a lot in the x-ray region of the spectrum. There are also tremendous focusing effects of magnetic field lines (accelerating charges again), and so the emitted radiation tends to get focused along opposing "jets".

Re:Geek explanation required.

[drxray]

Nothing can escape from "inside" a black hole, from within inside the event horizon. But as matter falls into the black hole it heats up, the gravitational potential energy gets turned into heat through friction-type processes (this also happens in waterfalls, the bottom is warmer). Hot stuff glows, and the gravity near a black hole is so strong that the matter does not just get red or white hot, it gets X-ray hot. And a lot of the X-rays, since they're generated outside the event horizon but still very near the black hole, escape so we can see them.

Most stuff doesn't generate much in the way of X-rays, so it's very easy to pick out the X-rays coming from the quasar. That's not so true of visible light - no doubt visible light also escapes from right next to the black hole, but it's drowned out by the outer regions of the quasar (which are visible-light hot instead of X-ray hot) and the galaxy the quasar is in.

Re:Geek explanation required.

[Tibor the Hun]

yeah, i think you're right. i may be completely wrong, but i think these are the x-rays emmited by the gas on its way to the event horizon.

Re:Geek explanation required.

[gardyloo]

Very nice explanation. You've read up on your ancestry?

Re:Geek explanation required.

[poopdeville]

If you look at Einstein's (or Newton's even) equations for gravitation, you'll see that it is an inverse square law. This means that the further away you are from an object, the weaker the gravitational force is. Indeed, if you move twice as far away from an object, the force is four times weaker.

Black holes have an associated event horizon. This is more or less the closest light can get without being sucked in. Obviously, the force of gravity is monumentally strong here. It is stronger still inside. But if you're outside of the event horizon, light can escape. If we're 2 event horizon units away from a black hole, the gravitational force is a fourth of what it is at the event horizon. Still a tremendous force, but light can escape.

What's going on here is that xrays are being produced as an object moves towards the event horizon. I'm not sure the mechanism that causes this. I'm a math guy, not a physicist. Perhaps someone else can enlighten us both.

You could also have Hawking Radiation in mind. I don't know anything about that. In fact, I'll click that linky myself.

Re:Geek explanation required.

[MillionthMonkey]

OK, can one of you physics geeks explain to me why x-rays are able to escape the gravitational clutches of a black hole when light cannot? I've never understood this.

Those x-rays you're seeing are coming from hot gas outside the event horizon. Undoubtedly much more radiation is emitted inside it than outside, but any photon inside the horizon has a world-line ending at the singularity and not your eye. And the photons you do see have lost a lot of energy in the trip up from the horizon's edge. They could have started out as gamma rays, but they get redshifted and softened as they climb up out of the field as they lose energy. Or here's a different way to look at it. Just as a clock near the event horizon will appear to a distant observer to be ticking slowly, a photon emitted with a given frequency near the horizon will have a lower frequency as measured by a distant observer.

Re:Geek explanation required.

[gardyloo]

I meant, um... drxray

Re:Geek explanation required.

[qbwiz]

Not at all. This x-ray radiation is due to the fact that the matter falling in is heated by compression. That matter adds to the mass when it finally arrives. If no matter were in the area, none of these x-rays would be produced.

Hawking radiation is completely different. What happens is that due to quantum fluctuations, random particles pop into being all the time. They pop into being in pairs, a particle and antiparticle, and normally soon annihilate each other. When they pop into existence near a black hole, sometimes the negative particle falls into the black hole, and the positive particle escapes.

The particle that goes into the black hole annihilates some of the hole, and decreases its mass. The escaping particle cannot reach its antiparticle, so it can't be annihilated. It goes out as radiation, increasing the mass of the rest of the universe.

The end result is that matter has (in effect) jumped out from the black hole into the rest of the universe.

Re:Geek explanation required.

[The_Wilschon]

Wrong in part.

The X rays emitted have essentially nothing to do with the heat of matter falling in, and everything to do with acceleration of charged particles. In fact, it'd be nearly impossible to actually get any substance "xray hot" as you put it.

When you heat a substance, it radiates, of course. This occurs due to electrons changing energy levels. These energy levels are very precisely defined, and thus the emission spectrum consists of sharp lines (they are not perfectly sharp due to perturbations like spin-orbit coupling, etc.). Then, in a macroscopic situation, many of the emitted photons will scatter off of other atoms, losing some energy in the process. By this mechanism, the sharp spectral lines get very blurred, and we see an essentially continuous spectrum (as long as you restrict it to middle range frequencies) with bright lines at the spectral emission frequencies.

The reason that this process doesn't produce xrays, no matter how hot you get the substance is that the energy levels an electron could be in do not range from 0 to infinity. In fact, in the case of a hydrogen atom, suppose we take an electron in the lowest energy shell to have 0 potential energy. Well then, now we move that electron to an infinite distance from the proton. At this point, it will have lost ~13.6 electron volts of energy. Thus, the highest energy photon that a hydrogen atom can emit due to an electron changing energy levels is just 13.6 eV. This falls in the ultraviolet range. And then, by scattering off other atoms, photons only lose energy, rather than gaining it.

Now, strictly speaking, as we increase the nuclear size, the difference in the energy levels will increase, and the energy of the emitted photons will be higher. So, if we used heavy enough elements, we could conceivably get them "xray hot". But by that point, we would very likely have reached the ultra-unstable elements that have only been created for very brief periods of time in the lab before decaying. Obviously, these are not found in great quantity in nature.

So, now that we know that heat isn't the culprit, how do we get xrays from black holes?

Well, I could be mistaken, and if so, I hope someone less mistaken than me happens on this post to correct me, but I believe that it primarily occurs because first, the atoms are ripped apart by tidal forces (they are "spaghettified"), leaving the electrons and the nuclei separated. Then, obviously, these particles are accelerating, and accelerating charged particles generates electromagnetic radiation. The greater the acceleration, the higher the frequency of the radiation generated. And since the gravitational force of the black hole increases as you get closer, the acceleration will proceed at a higher and higher rate, so the frequency of emitted radiation from one individual particle should slide upwards. Of course, that doesn't take into account gravitational redshifting, so perhaps the two effects cancel each other out nicely, leaving us with xrays.

Re:Geek explanation required.

[saskboy]

So a black hole is like nature's garberator, and it's a good thing our solar system isn't charted to become part of one of their accretion disks?

Re:Geek explanation required.

[The_Wilschon]

It is NOT due to heat, or friction, or any sort of thermal radiation. Hydrogen (the most common thing approaching a black hole, and due to tidal forces, anything larger would get ripped apart anyway (the hydrogen gets ripped apart too)) simply cannot ever emit radiation of that frequency due to thermal effects. The highest frequency thermal radiation of hydrogen is in the ultraviolet, nowhere near xrays. Furthermore, due to redshifting, the actual frequency emitted in the hydrogen atom's frame of reference is much much higher than xray range, making it even more implausible that the xray emissions are due to thermal radiation.

Most of the replies to this post have assigned it to some form of thermal radiation, whatever the cause of the heat, but this is simply wrong. See my other post for details why.

If we assume that almost exclusively extremely heavy elements are falling in to most black holes, then thermal radiation could be the source, but this is simply ridiculous for 2 reasons: 1) elements that heavy are ridiculously unstable, and thus do not occur in nature (at least not for long) and 2) tidal forces from the proximity of the black hole would actually increase their instability, so that even if there were large clouds of these elements drifting around, they would not survive to get close enough to the black hole to begin emitting.

Disclaimer: IANAPhysicist... yet. I am about to start my senior level undergrad classes as a physics major, and have worked for the last two summers at Fermi National Accelerator Labratory.

Re:Geek explanation required.

[Quadraginta]

Well, this is silly: ...if we used heavy enough elements, we could conceivably get them "xray hot". But by that point, we would very likely have reached the ultra-unstable elements that have only been created for very brief periods of time in the lab before decaying.

The lowest electronic energy level goes like Z, and X-rays start at about 100 eV. So you could easily get a soft X-ray out of something as small as oxygen or neon, which while not common are hardly the unstable transuranics you're talking about.

But the larger point is that a plasma, which is that of which an accretion disk is made, is perfectly capable of absorbing and emitting throughout the X-ray region. There's nothing strange about a plasma at 10^6 K, and it emits quite ordinary black body radiation with a peak in the X-ray.

So I think the parent was perfectly reasonable in saying the simplest way to think of this process in a general way is the conversion of gravitational potential energy to thermal energy (i.e. the kinetic energy of the the plasma) and then to radiation in the usual way.

I suspect any radiation produced by the direct gravitational acceleration due to the hole is miniscule. The acceleration required to keep a particle in an orbit of radius 10 km or so is trivial compared to the accelerations during an inelastic collision with another particle at (say) 60% of the speed of light.

Re:Geek explanation required.

[syntaxglitch]

Something like that. Also, our sun is far too puny to turn into a black hole itself.

Re:Geek explanation required.

[unixbugs]

im no scientist, but i do like to gamble, so i know a little about 'probability'.

for each set of 'spontaneous' particles that pop into existence, for each set that gets split up by the gravitational force of the black hole, it stands to reason that for each anti-particle to get absorbed, there would most likely be another 'spontaneous' particle set creation that would lose the particle to the black hole, thereby adding to the mass of the black hole.

so hawking's radiation killing a black hole would be a is a 35 - 1 payoff, am i right?

Re:Geek explanation required.

[sillybilly]

Why is it that an electron orbiting the hydrogen atom doesn't accelerate? Acceleration into a different dimension - i.e. perpendicularly - is still acceleration, and normal electrons going circularly in a cyclotron do radiate. Yeah, it would mean an energy catastrophe, sooner or later it would have to give up juice, either potential or kinetic energy, and run out of it. So these day we just say - postulate - that it goes in circles but it's forbidden to accelerate thus radiate, but could we say "it doesn't go in circles", or more precisely, it doesn't accelerate at all? It doesn't shift dimensions?

Re:Geek explanation required.

[unixbugs]

it also stands to reason that hawking's radiation could destroy the entire universe if enough anti-particles escaped into space....

Re:Geek explanation required.

[mcrbids]

Nothing can escape from "inside" a black hole, from within inside the event horizon.

This is not entirely correct. For all intents and purposes, you are right, but.... this covers a bit of the "Information Paradox" surrounding black holes, and Hawkings' admission that he was wrong - information DOES escape from a black hole - eventually.

Re:Geek explanation required.

[sillybilly]

Nothing can escape from Heaven either. However, listen to the following story:

St. Peter goes opens the gates of Heaven, because someone is knocking. A guy stands there, says "Aaaaa..." and puff, disappears, like magic. St. Peter doesn't understand it, he just shrugs his shoulders, closes the door back, and goes on his business. Soon, there is knocking again. Same thing all over, same guy there, about to say "Aaaa.." and puff, disappears again. This repeats a few times, until St. Peter loses his temper, and next time he opens the door, before the guy even gets a chance to open his mouth, yells at him: "What the hell are you doing man??" The guy finally able to catch his breath, and utter a full sentence says: "Aaai'm sorry, I can't help it when they are trying to use the defibrillator on me."

See? You can escape even from Heaven, with correct technology. If you can escape from there, then black holes should be a piece of cake too, IF you got the right technology. Commercials in 6549AD: Tourist trips to the depths black hole #XX9 near Polaris - guaranteed to rock your brains! Roundrip fare only $9999.999 denars.

Re:Geek explanation required.

[gardyloo]

http://vega.bac.pku.edu.cn/~wuxb/nstar.html

    The problem with your reasoning is that high magnetic fields (and, yes, this is one reason that perfectly spherical -- without net angular momentum -- black holes are basically impossible) really screw up the 13.6eV ionization energy for atomic hydrogen. In fact, strong enough magnetic fields (and you easily get them near black holes) raise the ionization energy of atomic hydrogen well into the thermal x-ray range.

Re:Geek explanation required.

[gardyloo]

Although I don't necessarily think that your wording was very accurate, you've essentially hit one of the nails of strangeness in quantum mechanics quite squarely on the head.
    One of the reasons that it took Bohr so long to come up with the (admittedly extremely simple) orbital model of the atom is that, hey, charges should radiate extremely fast at those accelerations (based on all sorts of measurements, most notably by Rutherford), and all matter should basically collapse very quickly. He eventually just sort of waved his hands and said that one of this postulates was that electrons simply can't radiate unless they're in transition from one "allowed" state to another, and then derived various neat consequences from that.
      I could give various hand-wavy arguments based on such things as eigenstates and Wilson-Sommerfeld quantization rules (or, in more modern terms, show a bunch of stuff from quantum electrodynamics) but it's basically a lot of nomenclature and rules which have been shown to work exceedingly well and make awesome predictions... and not make a damned bit of sense from an intuitional standpoint. Seriously.
      If you can dream up some way to connect the nonradiation of a point charge which is undergoing accelerations to everyday language which makes sense, I'm willing to bet you'd get a Nobel in record time.
      (Incidentally, invoking smeared-out charge distributions only sweeps the problem under the rug, as it were.)

Re:Geek explanation required.

[gardyloo]

Incidentally, my statement about finite-sized sources and "focusing" of radiations from it is correct... only not in this case (as far as I know). The beam formation from finite sources is due to monophase (or almost-monophase) emissions, and this sort of thing can't be expected from a black hole, even accounting for the finite speed of light. Mea culpa.

Re:Geek explanation required.

[MillionthMonkey]

This is the classical "white death" of the universe predicted by classical physics. An electron in a hydrogen orbital does go in circles. But it can only radiate to a lower energy state. As it becomes more localized around the proton, the uncertainty in position goes down and the uncertainty in momentum goes up. The electron eventually "floats" on this uncertainty in momentum, since radiating more photons does not get rid of it and can only increase it. This process is what forbids further radiative transitions to even lower states closer to the nucleus (which is why they do not exist, to crudely sum up a lot of math).

Sometimes the ground state electrons do fall in, but only if they are destroyed in the process. In nuclei that decay via electron capture, an electron in the innermost shell is captured by the nucleus in a p+e -> n+neutrino interaction. As it moves from the innermost shell into the nucleus, the electron emits an X-ray photon. The energy of this photon can be used to distinguish between K-capture and L-capture (from the lowest and second lowest shells), although I think they use Auger electron spectroscopy for that.

Re:Geek explanation required.

[0x0000]

Finally, one of the methods of radiation from black holes is that of spontaneous particle-antiparticle production in the tremendous gravitational gradient outside a black hole. Normally, these particle-antiparticle pairs recombine quickly. However, if one travels nearer a black hole than the other (they're emitted going in opposite directions relative to their center of mass, to combine linear momentum), it can get sucked down the gravity well, and the other escapes.

So there are anti-particles being emitted from black holes?

Re:Geek explanation required.

[sillybilly]

Perhaps you could tackle your idea of "undergoing acceleration." After all, based on the correspondence principle, when you're inside an elevator, you have no clue whether you are sitting in a gravity field, or you're "undergoing acceleration." I'm asking for some kind of intuitive understanding of the structure of space, why inertial reference frames don't matter - Galileo's flies don't accumulate in the back of the ship, because they get tired trying to keep up with it, you don't feel motion - but as soon as you accelerate, press the pedal down, you can physically feel it, nature tells you. What's up with nature, like that? One way was to call it D'Alembert's law, or Galileos inertia law, or Newton's. It just is. Then came relativity theory, pivoting on a single concept of having a maximum speed, the speed of light, came up with all kinds of neat space-curvature math, but it shouldn't end there. When they tackled the pardox of constancy of speed of light, that arose from Maxwell's equations - because, unlike with everything else mechanical, electrodynamics and electric induction from magnetic fields depends on simply moving magnetic fields, not just accelerating ones (F=q(v x B) - note v, velocity, not a, acceleration), so to bring velocity and acceleration under one hat, the speed of light c enters every formula to compensate. The shape of the laws didn't change, you still have Galileos relativity, but you had to twist something else to make it work. It's like you got extra insight, but you're not done. Then the elevator insight came to tackle general relativity. That's all general relativity is, the elevator box, not knowing the difference between gravity, and acceleration, therefore they must be the same thing as far as nature manifests them to you - curved spacetime. Everything else logically follows, but that's where it all ends, you get no further. You have to seek out these paradoxes, and just because a Bohr came up with some 'ether' theory that works, it doesn't mean there can't be something more. You can toss the rule at it, - no radiation in quantum states, only during jumps - and say it just is, it's a law, suck it up. Or you can pick at it, but you have to find the handle where to start.
Perhaps the electron really doesn't undergo acceleration in the physical sense - I'm not claiming I have an intutitive idea, or an answer to this, but it's some point you can start chiseling away at the issues, that seems to be ignored these days. Naive off-the-wall ideas are that, perhaps the electron doesn't feel acceleration because it has its own compensating antigravity field. Perhaps at the length scales in question, the amount of antigravity, antiacceleration generated, is compensated by the external gravity we call Newton's law, so in the end the total sum of negative plus positive gravities is 0. Another off the wall idea could be, that perhaps space has some kind of fine structure, tiled of some imaginary-number sided polygons/3d objects, and when you define motion as "something" changing space-cells, jumping to neighbours, like a dot on a computer screen, some funky math works out that under these "dx" measuring conditions, with imaginary numbers stirring in the soup, the acceleration doesn't exist in some conditions, like some "eigenvalues" misbehave with matrices. I'm not trying to make sense here, these are blow-smoke-up-your-ass-theories, but it's something to think about. What is acceleration? What is motion? What is space? These concepts are taken for granted, but that's where the key lies. We take teh basics for granted, as a foundation, we "know(consider)" spacetime is curved, consider that there are quantum states, and then off we go with these tools on head-hurting analyses and complexity that's awesome predictive - imagine a computational solution to chromiums orbital jumps - but we don't really care, as long as we know the fundamentals, the methods, it doesn't shock us if someone goes on a computational quest. Like calculating pi - when someone goes and gets 35 decimal places via Archime

Re:Geek explanation required.

[GuyWithLag]

No, the black hole eats the antiparticles, and it looks like it's emitting real particles.

Re:Geek explanation required.

[wjsteele]

There are two reasons why you would see x-rays from a black hole.

The first source and most obvious to the observer is that they don't come from the black hole at all, but rather the accretion disk of hot gas around the black hole. As the accretion disk is heated by the black hole (as it approaches) all wavelengths of light are given off, x-rays being one of the "last" based on the spectra.

The second source of x-rays is from what is called Hawking Radiation, named after Stephen Hawking. Hawking Radiation is a Quantummechanical radiation, as opposed to a "visible" radiation, is a very "rare" type of radiation in that such a small amount of the black hole is reradiated back out that it would be very hard to detect - but none the less, it is there. The wavelength of the Hawking Radiation depends on the mass of the black hole.

Bill

Re:Geek explanation required.

[BigDogCH]

"6549AD: Tourist trips to the depths black hole #XX9...Roundrip fare only $9999.999 denars."

So, if I put a penny in the bank now, and resist spending it until then, I will be able to afford to go?

Re:Geek explanation required.

[wackywendell]

In other words, the x-rays/light gets emitted not by the black hole but instead by all the stuff falling into the black hole. Think of it as seeing the screams of billions of particles as they fall into an abyss never to be seen or heard from again...it brings tears to my eyes.

Re:Geek explanation required.

[JDevers]

Some would argue that our solar system very much IS charted to become part of the accretion disk at the center of our galaxy. Now that won't happen until after the sun burns up all of it's fuel, but you have to keep the big picture in mind when you get afraid of the small stuff ;)

Re:Geek explanation required.

[Goeland86]

I'm not going to bother detailing the rest, as others have already answered this thoroughly.
What I will add however is that saying that only X-rays escape is a total mistament.

The rays escaping the Black hole's event horizon (basically the critical radius which is considered radius of no return) escape constantly. However, because of the gravitational strength of the black hole, the photons are redshifted. A redshift means their frequency is lowered. Their speed does not slow down, but their frequency is lesser as the gravity pulls. That's because the energy of a photon is it's frequency multiplied by it's velocity. You cannot slow a photon in empty space, therefore the only variable that can give in to compensate for the gravity force of the black hole is the frequency.
By redshifting while escaping the black hole, photons lose their visibility, because they get redshifted to infinity (or close enough that we can't detect them because of the cosmic background radiation).
If you have a chance and want to learn more, get the book "Cosmology: Science of the Universe", it's what my class used and it's very thorough, but still easy to grasp (I took the class as a freshman).

Re:Geek explanation required.

[drxray]

Well, that was my explanation for 16 year olds, it glosses over a lot. Quadraginta is entirely right that there are plenty of emission lines from atoms and ions in the X-ray band - neutral iron for instance is at 6.4 keV (kilo-electron-volts) which is quite a high-energy X-ray.
You're quite right that atomic emission isn't the whole story, emission from plasma (seperated electrons and nuclei) often dominates the spectrum. This emits by synchrotron radiation, Compton up-scattering of ultraviolet light from further out in the disc, and plain thermal emission. Thermal emission from a plasma doesn't involve emission lines, it's just electrons scattering off each other therefore accelerating and radiating in the process. X-ray hot plasmas are perfectly possible.
The gravitational tidal forces aren't what cause the plasma, it's all the heating from friction/compression. Tidal forces (outside the event horizon) are really small on the scale of atoms - you can approximately calculate it without too much difficulty comparing Newton's and Coloumbs laws.

Re:Geek explanation required.

[The_Wilschon]

mkay. I suppose I hadn't considered that. Of course, it would have to be raised quite far into the thermal x-ray range in order to make up for the gravitational redshift.

Re:Geek explanation required.

[The_Wilschon]

The lowest electronic energy level goes like Z, and X-rays start at about 100 eV. So you could easily get a soft X-ray out of something as small as oxygen or neon, which while not common are hardly the unstable transuranics you're talking about.

True. I failed to bother to figure out what atomic number it takes to start radiating x-rays. However, it is still true that anything much heavier than hydrogen or helium does not account for much of the mass falling into most black holes. Additionally, in order for us to detect even a soft xray here on earth, far from the black hole, a very very hard xray indeed would have to be emitted near the black hole, due to the redshifting.

Also, I do not know nearly so much about plasmas, so I suppose you might be right. I'm a bit puzzled by the black body radiation bit though. I wouldn't imagine (just based on intuition) that a plasma would be a black body. Then again, thinking about it some more, I suppose it would be.

Forgive me for things I didn't think out thoroughly, it was 1:30 am.

Re:Geek explanation required.

[jcorno]

An electron in a hydrogen orbital does go in circles.

No, it doesn't. s orbitals are spherical, not circular; that's why they don't have orbital angular momentum. It would be closer to observed behavior to say it spreads out and fills the space around the nucleus.

Re:Geek explanation required.

[QuarterDollar]

When you heat a substance, it radiates, of course. This occurs due to electrons changing energy levels.

I beg your pardon, but you're wrong on this point.

Check out the Wikipedia article on blackbody radiation.

Blackbody radiation, also called thermal radiation, is not an electronic process. Rather, it is radiation emitted by any substance with a nonzero energy density.

You hinted earlier that the material around a blackbody might be stripped of electrons (i.e., ionized). This must certainly be the case, since the temperature of infalling material around a blackbody is much higher than the ionization temperature of hydrogen. Given that all the energy levels are empty, shouldn't an electronic emission from this material be impossible anyway?

The remarkable thing about thermal emission is that the spectrum doesn't depend on what kind of material is emitting. Check out this equation for the wavelength of peak emission of a blackbody spectrum:

T lambda_max = 0.002898 Kelvin meters

This equation suggests that getting X-rays from thermal emission is just a matter of getting the temperature high enough. To get 100 eV emission, for example, you need a temperature of about 250,000 Kelvin.

Re:Geek explanation required.

[MillionthMonkey]

Yeah, forgot about them. The s electrons move in linear paths back and forth through the nucleus and the angular orientation of the path is indeterminate yielding the spherical distribution. Always have to be on guard for nitpickers around here.

Re:Geek explanation required.

[jcorno]

I wasn't nitpicking. I just disagreed with a small part of your comment and felt the need to point it out. OK, maybe that's nitpicking, but the description was misleading in a way that lead to the original misunderstanding. None of the orbitals, s or otherwise, are circular. There is no "path." The translational momentum of an electron in a stable orbital is always zero, which means it isn't technically moving. Like I said, it just spreads out to fill the orbital (which is also a misleading term, but it's a little late to change the convention) in a way that makes movement a useful analogy.

Re:Geek explanation required.

[aprilsound]

Matter pops into and out of existance all the time. When a matter particle pops into existance, its equivalent anti-matter particle pops into existance with it, and they obliterate each other almost immediately.

At the even horizon of a black hole, matter sometimes pops into existance, but with the antiparticle on one side of the even horizon, and the particle on the other, the antiparticle (or particle) gets sucked into the black hole, but its "other half" is able to escape.

This is believed to be Hawking Radiation

Re:Geek explanation required.

[MillionthMonkey]

Hmmm. Well, I seem to have forgotten my smiley I guess. I hate typing those things though- they look so juvenile.

I'm not sure I agree with you, but this level of physics is open to many interpretations, as it were, and a lot of smart guys have been struggling with them for a long time and trying to come up with better ones. The rule seems to be that any given interpretation can be equally valid for predicting experimental results as long as you stick with it consistently. The problem is coming up with one that appears to make sense in all circumstances.

The electron's translational momentum has an expectation value of zero. If you take multiple measurements you get a distribution of momenta centered around zero, but all the individual measurements will not be zero. The momentum cannot be determined to be zero at all times or we wouldn't know anything about its position. That wave function doesn't just smear out the position- it smears the momentum out a bit too. That would imply a limited motion of some sort.

Re:Geek explanation required.

[master_p]

But none of the above posts have explained why the particles generated outside of the black hole do not fall into the hole. Heated or not, how do these particles escape the gravitational pull of the black hole?

Re:Geek explanation required.

[sploxx]

I think you are entirely correct and the GP is wrong.
But maybe if the GP knows so much, he/she could describe what's wrong with the following (which I remember from the thermodynamics lessons I took): ?

Planck blackbody radiation simply describes the energy spectrum of bosons for any temperature T.
If you have ordinary matter (fermions) in thermal equilibrium with photons, it means that both have the same temperature. As you can heat matter to any temperature you wish, so you can produce a spectrum of photons with the peak at any wavelength (Wien's law) - for example xrays.

Re:Geek explanation required.

[qbwiz]

Random luck, as far as I have heard. Stuff like that happens in a quantum mechanical universe. As for why it's more likely that the negative particle is more likely to be pulled in, I haven't heard a really good explanation. One explanation is that the negative particle has less energy and is therefore more likely to be pulled in, but I'm not certain about that.

Re:Geek explanation required.

[0x0000]

No, the black hole eats the antiparticles, and it looks like it's emitting real particles.

Hmmm. So why would the black hole attract only anti-particles? How do we know anti-particles aren't being emitted near the black hole? According to the previous explination, both are formed, and some escape.

If I understand particle/anti-particle correctly, then there's no particular reason the black hole should prefer one over the other - they should have identical "mass", right?

Re:Geek explanation required.

[Old Wolf]

This is explained by Stephen Hawking in 'A Brief History of Time' (although I can't remember the details offhand), and is the same reason that the Big Bang produced more matter than antimatter, instead of equal quantites of each. I think it is to do with whether the particle and antiparticle are spinning left or right (P-symmetry).

Re:Geek explanation required.

[hde226868]

I am sorry, but your explanation is completely wrong. I am an X-ray astronomer working mainly in the area of black hole radiation processes, so I claim some credibility here...

First of all, accretion disks produce what is called thermal radiation ("black body radiation"). That radiation is produced by all material in thermal equilibrium (for example, our Sun's spectrum looks like a black body). In the inner regions of accretion disks around black holes, the typical temperatures are such that soft X-rays with energies of about 1keV are produced, i.e., temperatures of a few million kelvins. At these temperatures the radiating material is almost fully ionized. A large fraction of the primary radiation is produced by a process called bremsstrahlung, where electrons are accelerated in the electric fields of nuclei.

In addition to this primary radiation, harder X-rays are produced by secondary processes. The most important process for accreting black holes is most likely the process called Comptonization. The general picture is that the strong turbulence in the inner region of the accretion disk will result in magnetic reconnection, which is a very efficient process to convert magnetic field energy into kinetic energy. As a result there is a thin plasma of VERY hot electrons surrounding the inner region of the accretion disk. The emission of that plasma itself is negligible, however, X-rays entering the plasma from the accretion disk can be Compton scattered to energies up to those corresponding to the electron temperature, which is a few billion degrees. We can observe these photons with satellites such as NASA's Rossi X-ray Timing Explorer or ESA's INTEGRAL observatory.

So, no, "ripping apart nuclei" is not the process producing the observed X-rays at all, good old atomic physics is all that is required (and, yes, one can compute model spectra for the radiation emitted in such a system and these explain the observations extremely well).

Re:Geek explanation required.

[The_Wilschon]

Thank you for your correction... I feel rather ashamed for not having really thought out my post beforehand. It was 1:30 am, and I read everyone's "well, it gets really hot, not red hot, not white hot, xray hot!" and thought "That's not right! I know better than that!" without considering the issue very thoroughly. Please accept my apology and allow me to retract my statements as best I can. I am about to post a sibling to my post retracting it as well.

Re:Geek explanation required.

[The_Wilschon]

Well, please ignore the sibling post by me. It was not well thought out, it was at 1:30am, and others have corrected me. My apologies for any confusion I may have caused, and please allow me to (as best as one can on Slashdot) retract my statement.

Re:Searching..

[TildeMan]

Hey, their job got them posted on Slashdot! Probably kicks your job's ass any day. :-)

Even X-rays isn't enough sometimes

[Mick Ohrberg]

Here's a Journal entry about previously unseen quasars (black holes, really) that was found by Spitzer, just by looking for infra red signatures instead of X-ray.

Nanoscule Macroscopes

[Doc Ruby]

Black holes bend space in every direction. Their effect on space is strongest closest to them, especially within their event horizon. But they bend all of spacetime, in every dimension, infinitely. At least to the distance in lightyears of the duration since their forming, and even before, when their spread-out mass still bent space, just not all in one place, and without the counter-intuitive effects within the event horizon.

So it seems that relying on detectors which detect only the behavior of light between the Earthly observer and the unobstructed black hole is pretty crude. How long before we have nanodetectors that detect the miniscule (nanoscule?) deflection of a laser within a small space on Earth, away from the "straight" path we'd expect from the influence of the space matter that we can see? Maybe we have to account for the "dark" matter also bending space in the Universe. But such a detector seems like a lot more reliable mapping instrument, for all these cosmic masses, than just waiting for some gas to drift across the view of our traditional scopes. How long until we can start to use really sophisticated Einsteinian relativity detectors?

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

There is no ``dark matter'' (i.e. exotic matter) and ``dark energy'' seems unlikely.

Re:Nanoscule Macroscopes

[Solder Fumes]

When we're talking about the miniscule types of deflections you're hoping to detect, things like the size of individual atoms start to get in the way. To detect things far away, you need macroscale detectors, not nanoscale. For some observations we use the orbit of the Earth itself to expand the size of a virtual detector.

Re:Nanoscule Macroscopes

[Gabrill]

you're talking about mapping the activity of an olympic sized swimming full chock-full of kindergardeners from the observations of a bobbing cork. There is way too much affecting it to factor out the individual stimuli.

Re:Nanoscule Macroscopes

[Doc Ruby]

I suppose the inverse square law means that a black hole's effect on a given nearby space is b/d^2, where b is the black hole's mass, and d is the distance to its center. While a nearby object, even an atom, has the effect a/n^2, where a is the nearby object's mass (and d is the distance to its center). So if b/a > d^2/n^2, the black hole has greater effect. How far is the nearest black hole, in Astronomical Units? And how many times, say, does it mass than the Sun? Better yet, how about its mass compared to the Moon, and how many AU is the Moon from the Earth?

Re:Nanoscule Macroscopes

[Doc Ruby]

I dunno, it's too hard for me and my Pentium4 with its desktop calculator. But is it too hard for the latest supercomputer, and NASA's astrophysics software team, with ringers from MIT, CalTech and maybe CERN, or their local brain tank?

Re:Nanoscule Macroscopes

[The_Wilschon]

Actually... dark energy is one of the hottest fields in physics right now... I'd sure like to see the source for your statements.

Re:Nanoscule Macroscopes

[syntaxglitch]

I'd sure like to see the source for your statements.

He can't see it... therefore it doesn't exist? :)

Re:Nanoscule Macroscopes

[syntaxglitch]

Better yet, how about its mass compared to the Moon, and how many AU is the Moon from the Earth?

Think of it this way:

Most black holes are for obvious reasons of stellar mass, i.e, less than 20 times the mass of our sun. 20 AU doesn't even get you out of this star system--Pluto is 30 AU or so out. So the contribution of those black holes is going to be completely swamped by the sun.

The supermassive black hole at the center of the Milky Way is thought to be in the neighborhood of a 10^6 solar masses; the galactic center lies about 2x10^9 AU in the general direction of Sagittarius, so any contribution from it will also be swamped by the sun.

Nothing outside our solar system is likely to have any measureable gravitational effect on anything inside it other than the entire system orbiting the galactic center.

Re:Nanoscule Macroscopes

[Solder Fumes]

I was referring to the distance of deflection, assuming that our detector's finest level of resolution would be limited to the distance across an atom. Also assuming that we could detect a change in energy level from one atom to the next, and somehow compensate for normal spontaneous motion of the atoms.

As for the other concerns about swamping gravity readings with nearby stars and other objects, I would say that your idea has a chance of working if you can find some way to focus, reflect, or shield from gravity. But if you could do that, detecting black holes would probably be one of the last things we'd get around to applying your invention.

Re:Nanoscule Macroscopes

[gardyloo]

Have you noticed the jets that black holes produce?How could they be that long and strait without breaking the maximum speedlimit?

  Duuude. They're just going out to fight the Sharks and maybe dance a bit. They'll be back.

Re:Nanoscule Macroscopes

[Gabrill]

If it were possible, do you think we'd still be using telescopes to find new planets?

Re:Nanoscule Macroscopes

[gardyloo]

Two points to be made:
          1) NASA can EXTREMELY accurately predict the motion of coasting space probes. One of my favorite diagrams is in Marion and Thornton's _Classical_Dynamics_ book (Chapter 8, pg. 316 in my 4th edition copy). The diagram shows an approximation of the International Sun-Earth Explorer 3's orbit, and eventual rendezvous with comet Giacobini-Zinner. There were (I'm copying from the text here) two close trips by Earth and five flybys of the moon (within 75 miles of the lunar surface once). The text states, "The entire path could be planned precisely because the force law [the inverse-square law for macroscale -- and, now, mesoscale -- gravitational force] is very well known." That satellite traveled for 3 years, and used almost no fuel because its orbit was so precisely calculated far in advance.
      2) You're right -- every mass bends spacetime. Even energy (equivalent to mass via E=mc^2) bends spacetime. The coolest thing ever: GRAVITY ITSELF PRODUCES GRAVITY. My gen. relativity prof. did a riff on this in class for a couple days, and was able to show that at the level of a black hole, the "extra" gravity produced by the energy of a strong gravitational field basically leads to a runaway situation, and this is what happens at (or just "inside") an event horizon.

      Much research has been done on this recently, and, if it weren't so late, I could give you the names of some of the experiments to measure this "self-gravity" effect. Erdos?

Re:Nanoscule Macroscopes

[imsabbel]

Because if it _had_, your solar system wouldnt be stable...

The "bending" the greatparent speaks of is nothing mor than the normal workings of gravity... it wont be _any_ different from a star with a black hole from a ly away. Only closer than a stars radius it will be prominent, because of the singular nature of a black hole. Outside nothing will change.

The only way we can hope to detect those "bendings" are when stuff _really_ gets hot, i.e. creation of black holes. The gravity waves should momentarily be strong enough to be detectable even very far away (if one has EXTREMELY precise instruments)

Re:Nanoscule Macroscopes

[marcosdumay]

"How long before we have nanodetectors that detect the miniscule (nanoscule?) deflection of a laser within a small space on Earth, away from the "straight" path we'd expect from the influence of the space matter that we can see?"

Maybe not that long, but we will need a very long time to wait for our laser to pass by the black hole, reflect somewhere and come back to Earth.

Re:Nanoscule Macroscopes

[zippthorne]

I thought Dark Energy/matter was like UFOs. A self limiting field: as soon as you know what something is, it's not unidentified any more. For instance, you can't be abducted by a UFO, because then you'd know what it is and it wouldn't be a UFO anymore.

Re:Nanoscule Macroscopes

[The_Wilschon]

Not really. It is not just being unidentified that makes it "dark", it really is dark. We can estimate from large scale observation of various cosmological trends (not sure exactly how, cosmology and astronomy are not my fields) how much matter/energy is in the universe. We can also count up how much matter we can see (because it is luminous, like stars or quasars). The two numbers don't match up. Not even remotely. The latter is something like 30% of the former. So, we conclude that there is a great deal of matter/energy out there that we simply cannot see, hence it is "dark". The problem is that nobody knows exactly what form it takes. But knowing that form doesn't necessarily make it no longer dark, it just means that we know what it is that is out there not emitting light.

Re:Nanoscule Macroscopes

[Doc Ruby]

In fact, we've been finding new planets in our own solar system through gravitational deflection since Pluto was "Planet X". And we continue to find distant stars and other objects through gravitational deflection. While our computing power, and further articulations of Relativity, grow faster than we apply them to astrophysics. Yet we also use telescopes to find new planets. In short, "yes".

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

Dark energy is one explanation for certain observations (e.g. apparent increased acceleration at great distances). Certain string theories/M-theories offer alternative explanations for these observations; the correct theory may be completely different from string theory or dark energy. Right now dark energy is a "shot in the dark" which happens to be popular. It might be correct; everyone loves the cosmological constant. Although it has flaws, this Wikipedia article contains some information. I hope that The_Wilschon knows the difference between "one of the hottest fields in physics right now" and "the truth."

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

Doc Ruby: Sorry but you are in error. For hundreds of years, scientists have speculated about the existence of additional planets based on perturbations, etc. in the orbits of observed planets but the discovery of a planet required direct observation. There is lots of indirect evidence for solar and extrasolar planets (plus the direct observation of some, perhaps all, solar planets). We find perturbations in luminosity, etc. and hope this indicates the existence of a planet. This article, last revised in 2001, states
On the other hand, the major premise, and certainly the most important, is to ascertain the existence of extrasolar planets by direct astronomical observations. Speculation is easy, scientific endeavors are not. During the past several years the astronomical techniques used for observations have become more and more sophisticated leading to precise indirect methods of detecting planetary bodies orbiting stars other than our Sun. Although the evidence is compelling for the existence of extrasolar bodies, there has been no direct observation of an extrasolar planet; i.e., a viewing of a planetary body via a telescope and/or a photograph. A number of these astronomical techniques are discussed in Section 2 and 3 of this paper.
I have not been following this closely lately; perhaps direct observations of planets has occurred by now. There is no reasonable doubt that extrasolar planets exist; the only question is the standard of proof one requires to claim "discover" of a new planet.

Re:Nanoscule Macroscopes

[Doc Ruby]

The only "direct" observation of a planet is that of Earth: by smell, taste and touch our bodies directly experience molecules of the planet directly. Even the Moon we experience only indirectly: reflected sunlight, tidal effects on our seas. With the exception of extremely rare, tiny moon rocks that have dumped the gap, and of course the direct experience of the handful of astronauts who have felt the lunar surface through the deformations of their thick spacesuits.

Optical confirmation of other planets, whether in the visible band, radio band, or other electromagnetic disturbances modulated by the planets' interfering matter, is still the most reliable confirmation of their existence. Cross-reference with relativistic gravity data is still mostly detailing the relativity models. But relativity is extremely consistent. And it's bound to be much more reliable in sensing distant objects, as the power of gravity is much greater than the power of electromagnetism, in the same mass.

So discounting gravitational discovery of planets is, at best, premature, (really, it's visual discovery that's obsolescent). Gravitational detectors are just as indirect as visual. In fact, they're even more direct, because the gravity is actually "emanating" from the objects, while light is reflected from the planets (stars are only one degree closer to direct, in the light radiated from their masses). Relativistically, the gravity nearby us is actually the outer portion of the object itself, its matter merely the dense core of its extant manifestation in the universe, only the densest region of all spacetime in which the planet exists in full extension.

Re:Nanoscule Macroscopes

[Doc Ruby]

" within a small space on Earth "

The gravity from the black holes has already reached the Earth. Why send out the lasers to them, when we can watch the lasers twist through spacetime already bent nearby?

Re:Nanoscule Macroscopes

[The_Wilschon]

Yes, I do know the difference between a hot field and something which eventually turns out to be accepted theory.

And no, I don't think that being a hot field would mean that there were no flaws. In fact, if there were no flaws, it would far more likely be what is known as a dead field, at least when it comes to theory. Experimentalists could still be checking it for ages, of course.

The OP claimed dark matter and dark energy were dead fields already due not to them being absolutely correct, but due to them being unequivocably wrong. My point was that this is not the case currently. I never claimed that it was "the truth" or even implied that I believed it to be "the truth". So, I fail to understand the cause for your last statement.

Re:Nanoscule Macroscopes

[The_Wilschon]

No, it is termed dark because as you say, it does not radiate. Although, depending on how quantum mechanics and gravity get reconciled, it might be determined to be emitting gravitational force particles. After all, the way that we know about it is due to its gravitational effects. The fact that we manage to detect it more directly would have no effect on whether or not it radiates, thus it would still be dark. Of course, if we determined what it was because we found that it was emitting some previously unknown form of radiation, then it might lose the "dark" moniker.

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

Either you are a serious guy or not; for the sake or argument, I will assume you are a rational "scientist". (My PhD is in mathematics; if you have one, in what area is your PhD?)

So discounting gravitational discovery of planets is, at best, premature,
I was not discounting evidence from gravitational studies, etc.; rather I was asking what standard should be applied in order to be able to claim the discovery of a planet and applying the historical standard of (optical) observation. I believe this is a reasonable standard to apply; in order to meet this standard and (optically) verify the discovery of nearby planets, humans should invest more resources in astronomy and "analysis". Certainly distributed telescopes which depend on multiple instruments, precise timing, strong mathematical and statistical support, etc. offer the potential for great improvements in optical (and other areas of) astronomy. I think most people would agree that the optical verification of a new planet is the gold standard.

Re:Nanoscule Macroscopes

[Doc Ruby]

I am a serious guy. I don't have a PhD. You don't have a PhD in astrophysics. What is your point? Either you take my discussion seriously, as I expect, or don't.

I have not entered into any "argument" about what event counts as the "discovery of a planet". There's enough silly semantic arguments about whether Pluto is a "planet", or are the various other distant objects orbiting the Sun. Such an argument is only more irrelevant when discussing black holes, which can't be seen, by definition: only their gravitational effects on interposed light can be seen, and other indirect modulation of radiation consequent from their interactions with matter/energy.

I raised only the possibility of detecting black holes with newly possible devices on Earth, which can be read as they change in interaction with the nearby gravitational effects of black holes. I'm interested in talking about things like signal:noise problems, or perhaps gravity wave research, or anything else constructive on the topic. Arguments about when someone can claim to plant a flag on a planet in a faraway system are not the kind that I take seriously.

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

So, I fail to understand the cause for your last statement.
I said There is no ``dark matter'' (i.e. exotic matter) and ``dark energy'' seems unlikely.
You seemed to object to my statement; you said "Actually... dark energy is one of the hottest fields in physics right now... I'd sure like to see the source for your statements.". Perhaps I was incorrect as viewing this as an objection to my comment; for the sake of argument, let us assume you were objecting. If you propose a new "mechanism" in physics (scalar field, whatever), you should have some reasonable explanation of how it works. Does "dark energy" arise from quantum mechanical effects? Is this a new "Higgs Field"? Right now "dark energy" is just a ad hoc theory for explaining observations, one form of which happens to bring back Einstein's cosmological constant. The history of physics includes many instances of ad hoc theories (e.g. steady state cosmology) which are proposed and later discarded. Based on this history, I would guess that the probability "dark energy" is correct (in the appropriate sense in physics) is less than one-half. (It is also my personal view that dark energy is not the correct explanation for current observations.)

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

You replied to the statement "If it were possible, do you think we'd still be using telescopes to find new planets?" by talking about the detection of planets using gravitational measurements; thus your statement "I raised only the possibility of detecting black holes with newly possible devices on Earth" is incorrect. Earlier in this thread you did discuss the detection of black holes but here you were talking about planets.

I have not entered into any "argument" about what event counts as the "discovery of a planet".
Such discussions can go on forever; however, I believe any claims of discovery of planets should include at least some basic information. How many planets do you claim to discover? What are their properties (e.g. mass, orbital period, orbital radius)? (I picked some easy properties for you.) ETC.

I think the political and public benefit (i.e. more support for research) of the first good "photo" from our solar system (or from an unmanned probe "near" the extrasolar planet) of an extrasolar planet will be huge. I would love to see such a "photo" and I imagine humans will eventually travel to other solar systems (but not in my lifetime); I would also love "to plant a flag on a planet in a faraway system."

You don't have a PhD in astrophysics. A number of top cosmologists are essentially mathematicians (e.g. differential geometers) and astrophysics is becoming more and more "mathematical"; your criticism has little validity. You certainly don't need a PhD to post here but having experience doing published research in a "scientific field" (I include math here) does give one a valuable perspective.

Re:Nanoscule Macroscopes

[Doc Ruby]

Your first comments, disagreeing with my characterization of black holes, concentrate only on the "accretion disk" around the event horizon. Black holes, like any other mass locus, bend space in every direction around them, not just in the plane of the disk. That's simple gravitational attraction, by which any mass in the Universe attracts all the rest, the definition of relativistic matter.

So distant black holes (neglecting the theoretical boundary condition of an "infinitely distant" black hole) are distorting spacetime here on Earth, however tiny (though not "infinitesimal") the effect. I propose a nanoscopic detector that projects a laser to an array of nanodetectors. The deflection of the actual path to a detector, away from a theoretical model of the shape of space without a given black hole, shows that a black hole (or some other mass locus) is deflecting the beam. By distorting spacetime, which the detector can show.

The effects are tiny, but so are the detectors. Maybe nanoscale isn't small enough. Probably the signal:noise problems of nearby masses, however smaller than distant black holes, are prohibitive. But of course we're both engineering smaller devices (picoscale is probably predictable within our lifetimes), and tackling much more complex signal processing math/software all the time. I expect quantum computing signal filters to reduce many "drop in the ocean" problems to merely "needle in a haystack" problems as manageable as purifying uranium.

So it's really a matter of time, unless I've missed some controlling factor in my postulation. For example, gravity wave detectors have remained fruitless. I think they're just working in the wrong direction, trying to get larger detectors to trigger regular-sized sensors. But perhaps they're obstructed by some other phenomena that would also render my little light-compass unuseable.

Re:Nanoscule Macroscopes

[The_Wilschon]

By "last statement", I meant the last statement in the post I was directly replying to, ie where you questioned my ability to distinguish between "hot field" and "the truth". I was merely asserting that a) I did understand the difference, and b) I did not see any reason in what I had previously posted for you to suspect that I did not know the difference. I think this is a perfectly reasonable thing for me to object to, as the thing a scientist (which I am studying to become) relies upon most is his/her reputation. When my reputation is called into question with no apparent cause, I will object.

In the first post I made in this thread, I was replying to your claim that there is no "dark matter" and "dark energy" seems unlikely. My response was that a) I don't think that there is anywhere near sufficient evidence to conclude that there is no "dark matter", rather, there is a great deal of evidence to suggest the existence of matter which does not emit electromagnetic radiation (hence "dark") and b) most professional cosmologists appear to currently disagree with you when it comes to "dark energy". So, you have shown some source (ie vague, but reasonable philosophical arguments) for the "dark energy seems unlikely" portion. I'll accept that.

As I am not a cosmologist, I cannot be considered an authority on the matter, but I think that one of the theories of "dark energy" involves the fact that in quantum field theory, the ground state energy of a perfect vacuum is not zero, as you might expect. This "vacuum energy" would then be the "dark energy". So in that case, yes, it does arise from quantum mechanical, or rather, quantum field theory effects.

Re:Nanoscule Macroscopes

[Phragmen-Lindelof]

The term "dark matter" usually refers to "exotic" matter (e.g. WIMPs (= weakly interacting massive particles) were one candidate for exotic dark matter).
This "vacuum energy" would then be the "dark energy".
Were you, perhaps, thinking of the Casimir effect? This has nothing to do with proposed theories of "dark energy."

ouch

[cente]

Gee, doesn't that make you feel oh-so-safe for our upcoming space travel (many lifetimes ahead of us)... "a large group of hidden black holes." pot holes of the universe? You think driving is bad *now*...

Re:ouch

[Mick Ohrberg]

Compare an interstellar bumpy ride to a ride down I-35 around Kansas City, MO...

Re:ouch

[aussie_a]

But the article makes us realize, they're not really that hidden..

Re:Hidden black holes ??

[steelfood]

Black holes are called that because even light particles cannot escape its gravity. Color is caused by the reflection (or production) of light on a surface. If no light gets reflected, then it is black.

Interestingly enough, there was an article some time back about turning things invisible by painting them with a black paint that absorbs almost all light. Because the paint does not reflect light for your eyes to see, you effectively cannot see the object.

The principles are the same. For all intents and purposes, the black hole is the blackest of all black colors (imagine that, there are different shades of black!), and is quite aptly named.

I could be wrong about this.

[mcc]

Those X-rays don't "escape" the black hole because they aren't coming from inside the black hole. The idea is that as stuff falls into the black hole, it gets ripped apart at the atomic level. As it gets ripped apart, it emits x-rays. Because the matter hasn't quite reached the event horizon yet when this starts to happen, these x-rays are able to make it away from the black hole.

So in other words those x-rays aren't coming from the black hole. They're coming from just outside the black hole, the dying screams of the matter falling in. So no "escaping" is involved, not exactly.

Then there's Hawking radiation but that's different, I don't think those are X-Rays.

Re:I could be wrong about this.

[roadrunnerro]

The original meaning was probably something like "escape from being sucked into the black hole", but it didn't escape contraction ;>

dark matter

[80 85 83 83 89 33]

they must get mass estimates for these black holes, then multiply by the estimated number of them, and see if it makes up the missing mass. there is a good chance that dark matter has been answered.

Re:dark matter

[syntaxglitch]

That was actually one early theory about dark matter, but it's since been discarded--for instance, we've since mapped the distribution of dark matter, and it is both rather diffuse and not in locations where one would expect to find black holes. Sorry, it's not that simple.

Re:dark matter

[DMUTPeregrine]

Dark matter is far, far too large an error (around 90% of the universe's mass is "missing") for it to be accounted for by these few black holes.

Many scientists believe that there is no missing matter, and that the theory which predicts it is simply wrong.

Ob. CowboyNeal joke

[proverbialcow]

astronomers infer their presence by noting the behavior of material nearby: gas is superheated and accelerated to a significant fraction of light-speed just before it is consumed.

...whereas gas is superheated and accelerated to a significant fraction of light-speed just before it is expelled from your average CowboyNeal.

Re:i found a blackhole too

[steelfood]

At the end of the wikipedia article is a remark along those lines. It's somewhat amusing that the term "Black Hole" was not always the name for these things, as translating "Black Hole" to other languages sometimes produced something obscene. I'd hazard a guess that the objectable translations were probably along the lines of your comment.

Re:Hidden black holes ??

[DrunkenTerror]

Dude, are you goth or what?

It'll probably turn out...

[dysprosia]

It'll probably just turn out to be specks of grit on the scanner-scope.

Re:It'll probably turn out...

[Dimensio]

You can't blame them if it turns out to be the case. You see, the thing about grit is, it's black...

Re:i found a blackhole too

[steelfood]

Whoops, meant to write the first section of the wikipedia article.

Re:Hidden black holes ??

[Darkshot]

Even if you painted it with a black that absorbed every part of the visible spectrum, it would still block light from other sources which would allow you to see it. It would just look like a very... very black object... The only way it would be invisible would be like in space and thats more of a camoflague.

I thought...

[VegeBrain]

the biggest black hole in the universe was the United States national debt.

Colours of black.

[nephrita]

(imagine that, there are different shades of black!)

Of course there are different shades of black. Anyone who has owned an all-black wardrobe can tell you that the colours still clash.

Right.

[Mostly Harmless]

As the gas falls toward the black hole, it speeds up, creates friction, an releases the energy in the form of x-rays.

Re:Right.

[Mozk]

Off-topic, but about your sig. In the book(s) I have, Arthur says, "Ford, you're turning into an infinite number of penguins. Stop it." I know each version from different publishers are different, but I find that one more amusing. Meh. :)

Re:Hidden black holes ??

[steelfood]

I'm not entirely certain of the specifics of the application of the paint. However, last I heard, it was being researched as a means to invisibility. I'd imagine that it would work amazingly well at night, though that's a no-brainer.

The question is whether the human brain will trick a person into seeing beyond the object. I believe the article in question used the term "shrinking the object" to create the invisibility, which might imply an optical illusion rather than real invisiblity (absolute transparency, camera/projection system, light bending, etc.).

Re:i found a blackhole too

[MillionthMonkey]

Why didn't you just edit the wikipedia article to match your comment?

Re:Hidden black holes ??

[tloh]

Oddly enough, it's been predicted that small black holes may not be so black. All black holes are thought to emit hawking radiation. This process is supposed to reduce the mass of the black hole through kind of an evaporative process by bleeding "information" from the black hole. In addition to the fact that radiation intensity is inversely proportional to the size of the black hole, it is thought that sufficiently small black holes would exponentially radiate themselves out of existance with a brilliant explosion. Some have suggested somewhat tongue in cheek that they ought to be called "white holes".

Re:UNINFORMED CRACKHEAD COMMENT FOLLOWS

[Gabrill]

No, because the "Dark Matter" effect is seen EVERYWHERE, not just where these new quasars are being found.

Obligitory Rush quote

[Zaphod-AVA]

In the constellation of Cygnus
There lurks a mysterious, invisible force
The Black Hole
Of Cygnus X-1

Six Stars of the Northern Cross
In mourning for their sister's loss
In a final flash of glory
Nevermore to grace the night...

Re:i found a blackhole too

[eight and a quarter]

good idea. im gonna put uranus on there.

Let's bring people up to date

[Tibor the Hun]

Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes?

Also, once that happens will the black holes (as the only remaining objects in spacetime) start attracting each other? I'm hoping they don't reach some sort of a gravitational status-quo where our universe just becomes a universe of complacent singularities.

Nothing better to think about at 1:30 am on a Sunday morning than the death of the universe...

Re:Let's bring people up to date

[kale77in]

In a 'cold death' scenario, where gravity is too weak to pull the expanding universe back together (this seems to be the majority opinion, and people even talk about the expansion accelerating), I've heard the final distribution of matter estimated at: 9% black holes, 90% dead stars, and 1% dust and gas at 1030 years. I can't find a reference for that online now though; so obviously look it up if it interests you. Maybe some astrophysicist type can confirm or deny this?

Re:Let's bring people up to date

[Shadowlore]

Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes?

If the universe is expanding or constant, then no. If the universe is expanding the distances involved would prevent this from happening. If the universe is constant, then again not likely due to the distances invovled. That I remember at the moment, I've not heard of any credible theories that would say that a given volume of space with a given amount of matter would create a higher net gravitic effect if the matter were concentrated at a singularity in the center. Since gravity diminishes quickly over great distance, there is a limit to how far a black hole's "pull" is.

If the Universe is shrinking (or becomes so), then probably not. Of course, if the universe is shrinking, it doesn't matter what matter is left when it compresses to infinite non-space.

That said, the idea of black holes consuming other black holes has always been interesting. At least to me.

Anyway, you asked for speculation, so you got it. Grains of salt you'll have to provide on your own. ;)

Re: Let's bring people up to date

[Black Parrot]

> Can anyone explain if the curent theories still speculate that eventually all the matter in the universe will be sucked up by black holes? Also, once that happens will the black holes (as the only remaining objects in spacetime) start attracting each other?

Here is the most interesting thing I've ever read about the fate of the universe.

Re:UNINFORMED CRACKHEAD COMMENT FOLLOWS

[Quadraginta]

Good God, quasars are anything but dark. They emit energy on the same scale as a galaxy. The only sense in which these were "dark" is that you couldn't see them in the visible spectrum from Earth. But as the article notes, their presence was inferred by X-ray radiation reaching us, and confirmed by IR radiation.

Re:ARTICLE TEXT

[aussie_a]

Dude, it's space.com. They're not going to get slashdotted anytime soon. This is simply copyright infringement. By doing this, you deny Imaginova the revenue they would otherwise get, and stop people from seeing links in the article that may lead to pages they find interesting. Well done on harming someone who is providing a service you obviously think is worth viewing. If you don't think it's worth viewing, next time don't infringe on their copyright and simply skip the article.

I'm sorry, I said you did it for no reason. I just thought of the reason. You're also a Karma whore. My mistake.

I'm lost

[soundsop]

Beware, the article is quite technical:

If you extrapolate our 21 quasars out to the rest of the sky, you get a whole lot of quasars.

Re:ARTICLE TEXT

[sillybilly]

Nature tolerates no infinites. Now blackholes may not be a place with division by zero, but stop before reaching infinity, and inside them exist a noninfinite, but different, mystical kind of world where obviously our laws of physics don't operate. However we're still dealing with black holes, big bangs, and such, like people 500 years ago dealt with the sky - if you get a really long ladder, you can surely climb up to that ceiling, and knock on heaven's door? What happens when you walk to the edge of Earth/World? Do you fall down?

As opposed...

[SensitiveMale]

to the visible ones?

Re:Timely articles

[aussie_a]

If you don't like the service, stop checking the articles and posting. All you achieve by doing either activity is increasing the ad revenue Slashdot receives. So you're rewarding slashdot for (what you apparently consider to be) a sub-par service.

Re:Blackholes as dark matter

[Galahad2]

Could things like this be part of the explanation for that "dark matter" that scientists are always talking about? Maybe there are more and we just haven't found them.

Well, yes, but only a small part. We can put a pretty good upper bound on the amount of dark matter that can be in black holes based on gravitational lensing data. Black holes most famously absorb light that is incident inside their event horizons, but they also cause light traveling outside to curve around it. (As does all matter.) Thus, a star that is behind a black hole looks to be in a different place than it should, or even at two different places at once (more info). We can measure how much light is bent and infer how much matter is contained in high-density regions.

Obviously, gravitational lensing only happens where matter is compact. Uniformly distributed stuff won't do it. Thus, we know about how much dark matter there is, and from this, roughly how much can be in black holes. The punch line is that only a small fraction of dark matter (I don't remember the statistic off hand) can come from black holes.

The question is obviously, then, where's the rest of this matter? Some could be in other "normal" matter, like dwarf stars, but again, for various reasons that can't account for very much. Some could be in neutrinos (weakly interacting particles which are almost impossible to detect). This still leaves a whole lot of matter unaccounted for though. Maybe it's so-called WIMPs (weakly interacting massive particles) which theoretically could be very massive but interact with normal matter very little. Read more at Wikipedia.

Good question, though.

Re:Timely articles

[Anonymous Coward]

Hook line and sinker. If you don't like trolls you should stop feeding their ego by replying to them.

Mod parent up

[Galahad2]

They're right.

Re:old paradigm

[syntaxglitch]

Ha ha ha, that's pretty funny. It looks like you're trying to write science fiction--you probably don't want to quit your day job, though. ;)

Typical!

[Skiron]

You spend ages looking for one black hole, and then a whole bunch of them come along at once...

Sorry, that was 10^30 years...

[kale77in]

I missed the SUP tags being deleted... :(

is it wrong....

[firephreek]

that when I clicked on the link to the article, I was honestly expecting this

Other Stories

[zaguar]

http://physicsweb.org/articles/news/8/6/1
http://www.universetoday.com/am/publish/spitzer_fi nds_hungry_black_holes.html
http://www.nasa.gov/home/hqnews/2005/aug/HQ_05211_ Spitzer_black_hole.html
http://www.esa.int/esaCP/SEMPHV1P4HD_index_0.html
http://www.msnbc.msn.com/id/8812911/

More information of hidden black holes and their discovery.

Re:ARTICLE TEXT

[Eightyford]

I don't even know what karma is in relation to slashdot... is it to get mod points? Take it east buddy.

The article's errors...

[jd]

The gas is not "superheated". Superheating specifically refers to the process of heating something to above the point where it should transition from a lower energy state to a higher energy state. eg: From solid to liquid, liquid to gas, gas to plasma, etc. The reverse is called "supercooling", where something maintains a particular state despite being below the temperature at which it should move to a lower energy state.

Example: It is possible, at room temperature and pressure, to have pure water at 105 degrees celcius and NOT have it boil. It is very unstable and will generally boil vigorously the moment you get any kind of circulation within the water.

Second, Quasars (Quasi-Stellar Objects) are, as yet, undefined. Nobody knows what drives them, so to call them super-active Black Holes is blatantly absurd. They are also frequently at the very edge of the visible Universe, making it very unlikely anything large enough to collapse into a super-massive Black Hole could have existed - let alone existed long enough to actually undergo gravitational collapse.

Besides which, such objects are not near. This is important. Black Holes evaporate, but they don't evaporate THAT quickly. A Black Hole the size of a typical Quasar would need to be absolutely gigantic and would not have evaporated in this time even if no other matter had fallen in.

Indeed, there are NO quasars closer than 5 billion light-years away - a distance referred to as the "red-shift cutoff". If Quasars were galaxy seeds, you would expect them to fade into the age of galaxies, not dramatically and suddenly cut off entirely.

The idea that Quasars then formed into galaxies is improbable - the diameter of a Black Hole is a direct function of the mass of the Black Hole (which includes the mass and effective mass of everything it consumes). It is unlikely that there are any galaxies large enough to have a Black Hole of the kind of mass implied by the output of a typical Quasar.

If a Quasar were powered by a Black Hole, it would be typically 100,000 times more massive than the Black Hole at the Black Hole at the center of our own galaxy. Given that the presence of a galaxy implies that the Black Hole is still being fed matter and energy, it would be quite impossible for a Black Hole to evaporate to 0.00001% of its original size in the time available.

Remember, Earth is 4 billion years old, the Universe is only 15 billion years old. And of those 15 billion years, the Black Holes would only start to really evaporate relatively late on as the density of matter and energy declined. Actually, you don't even get all 15 billion years of that. Quasars peaked at about 12 billion years ago and as already noted, vanished entirely at 5 billion years ago. This gives you a paltry 7 billion years to shrink to the required size.

Now we get into a real mess. The Milky Way galaxy is ALSO estimated at 12 billion years old, based on the ages of known structures. There are no structures around Quasars. They'd be blown to bits. For the Milky Way to have formed around a "dead" Quasar, the Quasar must have formed considerably earlier. There are a LOT of galaxies out there as old as, or older than, the Milky Way. If all of them formed around Quasars, there would have needed to have been more of these really early starters than existed at the height of the reign of Quasars.

There is another problem. The Milky Way belongs to a local cluster of galaxies. If they ALL had formed around dead Quasars, the Quasars would have fallen into each other from their gravitational pull LONG before there was any possibility of a galaxy forming.

Nor are Black Holes strictly "hidden". They always emit Hawking Radiation, although there are no good detectors for this at present. That is hardly the fault of the Black Holes, though - if they're not seen, it's because the observers aren't looking.

As for the number of Quasars - there are only 39 known Type II Quasars

Re:The article's errors...

[Rich0]

You seem knowledgable and forgive me if my questions seem amaturish, but I'm curious about:

1. Has your analysis taken into account the possibility that quasars could be directional emitters - that would imply that their energies are lower, and their numbers are greater, than if they were omnidirectional?

2. Would it matter if you assumed that the Mikly Way once was a quasar a long time ago, but that matter stopped falling in (perhaps the rest took up orbit around it)? Could it conceivably evaporate enough in that time (my understanding is that black holes evaporate very slowly at those sizes, and that this might be a trillions-of-years process and not billions, but I had to ask)? The presence of a galaxy alone doesn't always imply fuel for a black hole - after all, if everything is just in orbit around the galactic center, nothing will actually fall in despite being close.

I must admit I was a bit disappointed by this article. They were just talking about quasars obscured by dust. I was hoping for black holes floating in the middle of intergalactic space where nothing is there to consume. That could represent a form of dark matter.

Re:The article's errors...

[niktemadur]

First off, you made me realize I'm at least five years behind, which breaks my heart, but I can only thank you for letting me know. I've gotta get on the ball. (In case you've all forgotten what a geek is).

Second, from paragraph 14 to 15 (out of 22), you went from theory to workshop to politics.

I agree with your optimistic ideas in what we, as a species, must do. I agree with your ideas as to how to go about it at first. I'm worried about the long-term factor: People who think opposite of science have so far waxed and waned in power, and may (will) surface again.

Democracy (with a Capital D) depends on You (and me) tolerating the existence (yet resisting the ideas) of fools.

Re:The article's errors...

[marcosdumay]

I may be able to answer your question number 2: A galaxy irradiates on all directions, thus feeding the black hole. You don't need much energy to compensate the evaporation of a very massive black hole.

But I also have another question: Why does the GP says that if the near galaxies have formed around quasars they would have fallen into each other? The long distance effect of the gravity of a galaxy is the same of the one of a black hole, and those galaxies orbitate now. Why wouldn't the black holes orbitate?

Re:The article's errors...

[drxray]

3: ...blatantly absurd...
No, it's a theory which fits all the facts we have.

...at the very edge of the visible Universe...
quasars from Nasa Extragalactic Database, these are quite close as the visible universe goes.
3C 405, redshift 0.056
3C 273, redshift 0.158
Not to mention that the distinction between quasar and active galactic nucleus is essentially one of luminosity, and Centaurus A is only at redshift of 0.001825, ~4 megaparsecs.
How the most distant quasars (redshift 6.4 = 1 billion years after the big bang, unless I'm out of date) formed so quickly is not yet known, but I don't know any reason why it'd be impossible to make one in a billion years.

4: ...evaporate...
Yes, they don't evaporate that quickly. That's irrelevant. The energy we observe from quasars comes from infalling matter.

...the size of a typical Quasar would need to be absolutely gigantic...
A typical quasar mass is 10^8 or so Solar Masses, as has been measured quite accurately by reverberation mapping, gas kinematics and water maser studies. The event horizon of a quasar of this mass is comparable in size to the Solar System. Yes, it won't evaporate.

5: ...NO quasars closer than 5 billion light-years away...
See above.

...If Quasars were galaxy seeds...
How would you make a galaxy out of a Black Hole? You certainly wouldn't manage it in the lifetime of the Universe. The formation processes of quasars and galaxies is complicated and the two can interact in interesting ways. Quasars form in the centre of galaxies.

7:...If a Quasar were powered by a Black Hole, it would be typically 100,000 times more massive than the Black Hole at the Black Hole at the center of our own galaxy...
Sagitarrius A* mass: 2.6*10^6 Solar Masses
Typical quasar: 10^8 Solar Masses
So it's more like a factor of 100. A few quasars have masses up to 10^10, so at most a factor of 10,000.

I think I'll stop here, you're making up numbers that are easy to find in google.

Re:The article's errors...

[stevelinton]

I think some of your information is quite seriously out of date:

The gas is not "superheated". Superheating specifically refers to the process of heating something to above the point where it should transition from a lower energy state to a higher energy state.....

True but pedantic. colloquial usage also allows "superheated" simply meaning "very hot", or "unusually hot".


Second, Quasars (Quasi-Stellar Objects) are, as yet, undefined. Nobody knows what drives them, so to call them super-active Black Holes is blatantly absurd.

Ten years ago this was the case. There now seems to be a great deal of consensus that quasars are the early stages of large active galactic nuclei. They are large black holes in the centre of large young galaxies, which are accreting large amounts of material, quickly and emiting very powerful axial jets.

They are also frequently at the very edge of the visible Universe, making it very unlikely anything large enough to collapse into a super-massive Black Hole could have existed - let alone existed long enough to actually undergo gravitational collapse.

Remember that the whole universe was denser then. I believe current simulations do support multi-million solar mass black holes forming quite quickly, at the same time as, or even earlier than, the formation of "regular" galaxies.


Besides which, such objects are not near. This is important. Black Holes evaporate, but they don't evaporate THAT quickly. A Black Hole the size of a typical Quasar would need to be absolutely gigantic and would not have evaporated in this time even if no other matter had fallen in.


Sure, but if nothing is falling into it, it's just sitting there being black. We do see very large (billion solar mass) balck holes at the centres of some relatively nearby galaxies (more accurately, we see stars orbiting them).

The idea that Quasars then formed into galaxies is improbable - the diameter of a Black Hole is a direct function of the mass of the Black Hole (which includes the mass and effective mass of everything it consumes). It is unlikely that there are any galaxies large enough to have a Black Hole of the kind of mass implied by the output of a typical Quasar.

As I say, we see billion solar mass black holes (which are still only a few light years across at most) by their gravity in some nearby galaxies. I'm not sure what the problem is.

If a Quasar were powered by a Black Hole, it would be typically 100,000 times more massive than the Black Hole at the Black Hole at the center of our own galaxy. Given that the presence of a galaxy implies that the Black Hole is still being fed matter and energy, it would be quite impossible for a Black Hole to evaporate to 0.00001% of its original size in the time available.

Don't understand this one. Sure not all galaxies have very large black holes in them, but no one is claiming that all galaxies were once quasars. Only the biggest ones.

Now we get into a real mess. The Milky Way galaxy is ALSO estimated at 12 billion years old, based on the ages of known structures. There are no structures around Quasars. They'd be blown to bits. For the Milky Way to have formed around a "dead" Quasar, the Quasar must have formed considerably earlier. There are a LOT of galaxies out there as old as, or older than, the Milky Way. If all of them formed around Quasars, there would have needed to have been more of these really early starters than existed at the height of the reign of Quasars.

There is another problem. The Milky Way belongs to a local cluster of galaxies. If they ALL had formed around dead Quasars, the Quasars would have fallen into each other from their gravitational pull LONG before there was any possibility of a galaxy forming.


I think the Milky Way is considered too small to have been a quasar. Only the biggest elliptical galaxies will have been quasars.


Nor are Black Holes strictly "hidden". They always emit H

Re:The article's errors...

[jd]

Precisely because the local cluster of galaxies is reasonably stable. A Quasar is 100,000 times more massive than the black hole at the center of the galaxy, so the gravitational field must have been considerably greater. Not only for our galaxy, but for EVERY galaxy in the cluster.

If what we have now is stable, then multiplying the gravitational field strength by 100,000 should have caused the quasars to collapse inwards.

Now, here's the killer part. It is possible to have a solution to this - the quasars are moving apart at some speed S, are pulled towards each other sufficiently to halt that outward motion AND evaporate sufficiently fast that, by the time the motion is largely halted, the system has become relatively stable.

This is such an improbably complex scenario (it's not impossible, just very very improbable) that we can conclude that EITHER Zaphod Beeblebrox was visiting the area at the time, OR it didn't happen this way. My money's on the latter.

Linux Black Hole?

[zaguar]

What about /dev/null?

Re:Linux Black Hole?

[kihjin]

[frozen@frozen ~]$ echo `cat /dev/null`
 
[frozen@frozen ~]$

Nope, nothing.

Smoke me a kipper!

[NanoGator]

When asked why it took this long to discover the nature of the strange space phenomenon, Mark Lacy of the Spitzer Science Center at the California Institute of Technology replied:

"Well, the thing about a Black Hole, its main distinguishing feature, is it's black. And the thing about space, your basic space color, is black. So how are you supposed to see them?"

Cue Ignorant slash dot comments

[blackpaw]

There is nothing more guaranteed to expose the embarrassing ignorance of the basic slashdotter re physics than black holes.

Nothing to see here...

[kihjin]

Is this actually one of the few moments in Slashdot news when "Nothing to see here, please move along" is literally true?

Re:Nothing to see here...

[trapvector]

Perhaps, but...

you *can't* move along.

Re:Searching..

[Walt Dismal]

Well, one starting place might be former dot-coms. A lot of them imploded into black holes. See, you just start with their former URL and look for evidence of nearby routers from which no packets can escape.

Re:ARTICLE TEXT

[Fussen]

Wow. Way to pull off a rant about CTRL + C CTRL + V.. somebody needs to walk away from the computer and .. walk.

Re:Who's the X-ray's daddy?

[Quadraginta]

I think you look for short-period variations in the luminosity. These give you an upper limit on the size of the object, since the luminosity can't vary in a time less than it takes light to travel across the object.

Then you start considering ways to get an object of that (small) size putting out the observed amount of energy, and you find that only matter falling into a hole will do the trick.

Re:Hidden black holes ??

[TapeCutter]

"Interestingly enough, there was an article some time back about turning things invisible by painting them with a black paint that absorbs almost all light. Because the paint does not reflect light for your eyes to see, you effectively cannot see the object."

That explains why the Mafia drive around in black limo's.

Holly...

[Black.Shuck]

"It's always the way, isn't it? We've been in space for three million years and there hasn't been one. Then all of a sudden, five of them turn up at once."

Theory

[Elitist_Phoenix]

BlackHole == Windows == Holes being found all the time... what am I missing?

Gravitational lensing

[Itchy Rich]

Just think, if you can find a straight line near our solar system that passes through two black holes, with a bit of work you might be able to create the biggest telescope ever... assuming the lens geometry works. Okay, okay, there's loads of impracticalities and the issue of lens geometry, but it's a nice idea.

Re:Gravitational lensing

[wackywendell]

That and it can only look in one direction...

Re:Timing

[grimJester]

I love my (x^.5, x=(-|x|-1)) friend.

AAAGH! neither "one" nor "imaginary" works! x=1 gives 1 = -2, x=-1 gives -1 = -2!

In fact, since
x=(-|x|-1) gives x + |x| = -1, 2x = -1 for x >= 0 and 0 = -1 for x less than 0, there is NO SOLUTION for your equation!

Now, x = -2|x| + 1 would work JUST FINE!

I hate you.

A large group of hidded black holes...

[nastro]

Well, hidden compared to the obvious ones in the quarterpanel of your Corvair.

Are there any obvious black holes in outer space? There must be. Rush wrote a song about one.

ISEE 3

[dan of the north]

"One of my favorite diagrams is in Marion and Thornton's _Classical_Dynamics_ book (Chapter 8, pg. 316 in my 4th edition copy). The diagram shows an approximation of the International Sun-Earth Explorer 3's orbit, and eventual rendezvous with comet Giacobini-Zinner."

This is pretty impressive too:
http://heasarc.gsfc.nasa.gov/Images/misc_missions/ isee3_traj.gif
Mmm... Pretty colours... Mmm...

--

Re:ARTICLE TEXT

[luna69]

God I hate the writers at Space.com. I stopped writing them with corrections early on when I realized that they don't care about accuracy, and weren't going to bother to improve. It's predigested space-oriented pabulum for the masses...but it's often incorrect or misleading.

Case in point, from TFA:
  "The most active black holes eat so voraciously that they create a colossal cloud of gas and dust around them, through which astronomers cannot peer."

This is kind of true, but it's also more correct when reversed: the black hole is "active" BECAUSE there is gas and dust in the vincinity for it to 'eat'. The BH doesn't create the cloud of gas and dust in any sense.

Another:"A few quasars have been identified"
Well, ok, it you count well over two thousand of them 'a few'.

This is just sloppy work on the author's part, and is typical of the schlock they produce on a regular basis. I've seen them make patently false statements as well, in addition to simply misleading or incomplete ones. Sigh..

Minor nitpick

[techno-vampire]

...the diameter of a Black Hole is a direct function of the mass of the Black Hole (which includes the mass and effective mass of everything it consumes).

If you want to be accurate, the circumference is a direct function of the mass; the diamater may well be infinite.

Can We Reject the Null Hypothesis?

[PingPongBoy]

where obviously our laws of physics don't operate

I don't see it is so obvious that the laws of physics are not usable to discuss the inside of a black hole. Newton's 3 laws (inertia, F = ma, and equal and opposite reaction), for instance - can you explain why they have no validity in a black hole? Well, to start with, there ought to be mass in the black hole due to the gravitational effects we feel on the outside, right?

The laws of physics are the null hypothesis (statistics). Although we cannot accept the null hypothesis in our world, we don't reject it. I am not a black hole scientist, so I need to ask what evidence do we have to reject the laws of physics for the inside of a black hole?

Re:Can We Reject the Null Hypothesis?

[sillybilly]

What is mass? What is gravity? There ought to be mass because there is gravity? - when we don't even know what the terms "mean," we just have a shallow, temporary understanding of them? That's like asking what is the temperature, if I stuck my finger in it, it's surely cold because if it were hot then it would glow? Or it's surely hot because it glows except the glowing can't escape, together with my finger, or finger-sensation-nerve-currents? Does it have no temperature if the measurement can't escape? What's the definition? As opposed to mass and gravity, at least we know that hotness and coldness comes down to something else, something more basic, the atomic/molecular motion, and then we don't have a problem describing temperature inside a black hole, which can be hot, or cold, depending how the atoms move, and what the statistical entropy states are. But still, if you can't get information out of a black hole, how do you measure anything? Science is pitted on empiricism. In fact, how come gravity escapes a black hole? Are these mystical gravitons "lighter" than photons, using the term lighter losely because the very definition of light gravitons depends on gravitons, making it a circular definition.

Basic Grammar people

[Zerbey]

"Hidden black holes discovered". That's just not possible, if something is hidden then by definition it hasn't been discovered yet. Unless, some hitherto unknown alien intelligence discovered them first and hid them.

Otherwise, it's just your basic newly discovered black hole.

uh...

[cfx666]

Scientific articles with a headline like this give my spam assassin a headache...

Cfx