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Hawking Radiation Claimed Created In a Lab

CmdrTaco posted more than 3 years ago | from the look-what-i-can-do dept.

Education 129

eldavojohn writes "In 1974, a young newcomer to the Royal Society named Stephen Hawking predicted that black holes emit Hawking Radiation. Researchers have been looking for it in space ever since. A new paper up for publication claims to have beaten searchers by observing it in a lab. Doing it wasn't easy. They say they brought light to a standstill by drastically increasing the refractive index of the material it was being fired at, creating a 'white hole.' This horizon, beyond which light cannot penetrate (event horizon), is the same between white and black holes, which caused the team to suspect they observed Hawking Radiation when light of a different uniform wavelength than the input laser was emitted. But, before you rejoice, the Tech Review article notes, 'Of course, the big question is whether the emitted light is generated by some other mechanism such as Cerenkov radiation, scattering or, in particular, fluorescence which is the hardest to rule out.'"

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129 comments

what bs are you posting (-1, Troll)

Anonymous Coward | more than 3 years ago | (#33710272)

this was disproved a long time ago and hawking even admitted as much
it was about black holes and that they emit themselves basically to death and "evaporate"
which was later proven totally false

Re:what bs are you posting (5, Funny)

Mitchell314 (1576581) | more than 3 years ago | (#33710374)

pics or it didn't happen

Re:what bs are you posting (1)

Mitchell314 (1576581) | more than 3 years ago | (#33710462)

BTW, on a more serious note: a quick google search of "hawking radiation disproved" [google.com] doesn't seem to come up with much serious material.

Re:what bs are you posting (4, Informative)

interval1066 (668936) | more than 3 years ago | (#33711208)

'BTW, on a more serious note: a quick google search of "hawking radiation disproved" [google.com] doesn't seem to come up with much serious material.'

Well, you generally shouldn't come up with a lot of material for or against this theory; you need a black hole to really test it.

We all understand what Hawking radiation is, right? Its the run-off of actual particles created when a virtual particle pair "pops" into existence near the event horizon of a black hole; normally the two annihilate each other but in this case one of the two gets sucked into the black hole, the other shoots off into spacetime. This also gives the hole a little negative mass, leading to the other huge implication in this theory; black holes can evaporate.

Re:what bs are you posting (3, Interesting)

raynet (51803) | more than 3 years ago | (#33711462)

Why would the black hole diminish? Shouldn't the same amount of virtual particles and virtual anti-particles cross the event horizon?

Re:what bs are you posting (4, Informative)

SETIGuy (33768) | more than 3 years ago | (#33711896)

Both particles and antiparticles escaping carry positive energy away from the black hole. The consumed virtual particles carry negative energy into the black hole. Therefore the mass decreases.

Re:what bs are you posting (2, Interesting)

SlothDead (1251206) | more than 3 years ago | (#33716082)

But what about the normal particles falling into the black hole? Why don't the cancel out the antiparticles, on average? (I'm not a physicist, I never understood Hawking radiation)

Re:what bs are you posting (2, Interesting)

Mitchell314 (1576581) | more than 3 years ago | (#33714862)

This is the way I understand it (probably wrong): because of quantum mechanix hocus pocus, any point in space-time does not have zero-energy. Also, that energy state isn't perfectly stable, so occasionally it causes virtual particles to appear. Those particles are complementary matter / anti-matter particles, and under normal conditions, they quickly annihilate each other after their birth. However, very very close the event horizon, some unfortunate particle is sucked it while their siblings have the right velocity and distance away from the black hole that they run away. Remember that there's conservation of energy/mass (mass and energy can convert into each other, but you can't actually destroy or create them). So because of that conservation, and since the black hole is emitting radiation, the black hole is losing mass/energy.

I *guess* (see:not researched) that because space-time really doesn't like very low energy states that it somehow sucks energy from surroundings, ie slowly pumping energy to the event horizon from a little bit inside, and that concentric zone dips in energy and sucks some more from the space inside that, etc until you get to the singularity. But that seems to contradict the whole "point-of-no-return", so I really don't know how it works.

Black holes are fucking weird.

Re:what bs are you posting (3, Interesting)

Dragoniz3r (992309) | more than 3 years ago | (#33711576)

Although, the black holes that can currently evaporate due to this mechanism are (as I understand it) well below stellar mass. The amount of hawking radiation that larger black holes emit is below the amount of energy they receive from the cosmic microwave background, thus they cannot evaporate.

Re:what bs are you posting (2, Funny)

FatdogHaiku (978357) | more than 3 years ago | (#33713164)

So, Long story short is I'm not going to get a cool new device that replaces the microwave AND the trash compactor at the same time? I always let these headlines build my hopes for a better future... You'd think I would learn...

Re:what bs are you posting (5, Funny)

cpscotti (1032676) | more than 3 years ago | (#33710846)

Didn't you read the thing?

...They say they brought light to a standstill by drastically increasing the refractive index of the material it was being fired at...

They tried to take pics but somehow there wasn't enough light..

Re:what bs are you posting (5, Informative)

simcop2387 (703011) | more than 3 years ago | (#33710392)

OK, either you're a troll and I'm wasting my time (most likely) or you're misunderstanding something. What Hawking admitted wasn't that the radiation didnt' exist but that the radiation did not in fact violate the principle of conservation of information. Previously Hawking had believed that it must violate said principle because there was no understood way for there to be a connection between the information about the matter that had fallen in and gone past the event horizon and the radiation that would be emitted. This was challenged by another physicist, whose name escapes me since I can't look it up at the moment, who reasoned (along with a more definite proof of course) that the information gets left at the event horizon also. This is because of the fact that from the perspective of anyone outside the event horizon any matter or energy falling in will never actually reach the event horizon it'll just appear to be slowing down further and further until it for all intents and purposes stops. This allows the virtual particles making up hawking radiation to be influenced by the information left at the event horizon without there being a need to have communication between the singularity at the center and the event horizon.

Re:what bs are you posting (3, Interesting)

martas (1439879) | more than 3 years ago | (#33710686)

umm, is this [wikipedia.org] what you're talking about?

Re:what bs are you posting (4, Interesting)

simcop2387 (703011) | more than 3 years ago | (#33711118)

Not quite, i was referring to this [wikipedia.org]. i couldn't look that up earlier because i was on a really bad connection that was dropping packets left right and center.

Re:what bs are you posting (3, Funny)

SQLGuru (980662) | more than 3 years ago | (#33711318)

i was on a really bad connection that was dropping packets left right and center.

So, you're saying that your information was falling into a black hole and you couldn't retrieve it from the event horizon???

Re:what bs are you posting (3, Interesting)

Gunnut1124 (961311) | more than 3 years ago | (#33712278)

Leonard Susskind was the guy and the problem wasn't originally an "information" problem, but instead an entropy problem. The information questions came in after they sorted out the holographic principals of information representation along the surface area of the event horizon.

Sean M Carroll has a good book about what that means for time if you are interested...

Re:what bs are you posting (0)

Anonymous Coward | more than 3 years ago | (#33712462)

Looks interesting, i've added it to my list of too many things to read, i'll get to it eventually i hope.

wild analogies and guesses (1)

yyxx (1812612) | more than 3 years ago | (#33715180)

Of course, the entire reasoning is based on wild analogies and guesses. Normal physical laws may well break down at singularities entirely, meaning that normal conservation laws may also break down.

Re:what bs are you posting (0)

Anonymous Coward | more than 3 years ago | (#33710412)

BH evporation is explained on wikipedia with a lot of complicated looking mathimatical forumals, so it must exist. becuase the theory of BH evaproation is to prove itself.

However the proof of the researchers is that they did not find an other source for the ration at 1050 nm, so it must be hawking radiation.

powerful lasers are so cool!!! (or hot.. since they use IR lasers )..

Re:what bs are you posting (5, Informative)

ath1901 (1570281) | more than 3 years ago | (#33710416)

[citation needed]

As far as I know Hawking Radiation and black hole evaporation have not been ruled out. The effect is just so small that there is no experimental evidence of it.

Actually, you'd better hope black holes evaporate or the black holes the LHC might create may destroy the earth! I for one use a tin foil hat just to be safe.

Re:what bs are you posting (1)

equex (747231) | more than 3 years ago | (#33710520)

Urgh, I was confident that black holes would evaporate due to Hawking Radiation, that's why I didn't get myself a tinfoil hat when the whole LHC controversy came up. So they are actually going to make black holes at LHC without even knowing if it will evaporate? Or is there another mechanism that will make the black hole diminish that are 10000% confirmed ? Otherwise I can't believe that they are actually going to do that?! Halp? Please?

Re:what bs are you posting (4, Insightful)

radtea (464814) | more than 3 years ago | (#33710720)

So they are actually going to make black holes at LHC without even knowing if it will evaporate?

For the LHC to create black holes at all would require a whole bunch of very speculative physics to be true, and a whole bunch of very well-established physics to be false.

In particular, if the LHC can create black holes then millions of black holes are being created every day by cosmic rays, which can have twenty orders of magnitude more energy than the LHC. No evidence of those black holes is seen anywhere, not in geochemical track analysis, not in the radiation signature of cosmic ray showers, no where. Ergo, either such black holes are not being created, or they are being destroyed with incredible rapidity.

For the beam dump of the LHC to behave any differently would require physics so arcane as to be basically magic, and anyone who is worried about it should also be terrified that a herd of flying elephants will trample them to death, because that's a far more probable event.

Re:what bs are you posting (0)

Anonymous Coward | more than 3 years ago | (#33712342)

"which can have twenty orders of magnitude more energy than the LHC"

I'll be dam...... time to go double layer on that tinfoil hat.

Re:what bs are you posting (1, Informative)

Anonymous Coward | more than 3 years ago | (#33710764)

The model that predicts Hawking radiation is the only model that would let them produce miniature black holes in the first place.

Sing it with me: "you can't have one... without the other!"

Re:what bs are you posting (1)

ath1901 (1570281) | more than 3 years ago | (#33710802)

Similar energetic collisions happen in the upper atmosphere because of cosmic radiation. That's why you need the tin foil hat! (not tin foil shoes)

http://public.web.cern.ch/public/en/lhc/safety-en.html [web.cern.ch]

Re:what bs are you posting (0)

Anonymous Coward | more than 3 years ago | (#33711556)

yes, but high energy cosmic particles all have huge momentum with respect to the earth, so no matter what they do, the original particle is either gone or the thing it hit blows through the other side at about the speed of light. But because we smash beams into each other from opposite direction, many black holes (if created) would have near zero net momentum (less than escape velocity). The real evidence is that there exist very dense stars with incredible escape velocities that also get bombarded with these particles, and they don't get turned into black holes very quickly, so, in the worst case, we should be fine for at least a few million or billion years (crosses fingers).

Re:what bs are you posting (1)

interval1066 (668936) | more than 3 years ago | (#33711300)

  • No reason for anyone to be confident regarding a theory, no matter how reasonable (and this one is quite reasonable.)
  • Any black holes near enough to be of any concern for you are probably staying away of embarrassment anyway.
  • A tin foil hat coupled with a duct tape wallet accessory can be quite stylish if folded correctly.

Re:what bs are you posting (5, Interesting)

ath1901 (1570281) | more than 3 years ago | (#33710584)

By the way, even if this experiment and their conclusions hold water, it is not a proof of black hole evaporation or Hawking radiation. It would be more like a proof of concept.

In the experiment, they've created a pseudo-event-horizon from which light can't escape. It's only a light event horizon though. Shoot a bullet through their material and you will definately see it go through the event horizon without any problems.

The similarities to a real black hole is that photon pairs created on the pseudo-event-horizon should create radiation if Hawkings reasoning about real black holes is correct. So, it would show that Hawkings thought experiment had some merit but not that black holes necessarily radiate.

Re:what bs are you posting (2, Funny)

thestudio_bob (894258) | more than 3 years ago | (#33711794)

Shoot a bullet through their material...

God Bless America!. Even in science, we can solve any problem by just shooting at it.

Re:what bs are you posting (2, Insightful)

Sir_Lewk (967686) | more than 3 years ago | (#33710716)

Even if the black holes the LHC might create don't evaporate, they'd be rather harmless.

Why? Well their radius is terribly small so the chances of collisions with anything else are pretty small. Furthermore, their mass is extremely small as well and gravity is the weakest of the forces. They would have a extremely difficult time ever gaining more mass.

Not to mention, if they don't evaporate then there is a fair chance they are all over the place already, thanks to cosmic ray strikes.

Re:what bs are you posting (1)

m50d (797211) | more than 3 years ago | (#33712622)

Stupid question, but it's always bothered me:

Particles are points, right? I.e. of zero size, and therefore infinite density. So why doesn't (e.g.) an electron immediately collapse to form a black hole?

Re:what bs are you posting (3, Interesting)

russotto (537200) | more than 3 years ago | (#33713450)

Particles are points, right? I.e. of zero size, and therefore infinite density. So why doesn't (e.g.) an electron immediately collapse to form a black hole?

An electron's classical radius isn't zero, but more to the point, you can't use just classical physics at that scale.

Re:what bs are you posting (1)

dwinks616 (1536791) | more than 3 years ago | (#33714168)

No, an electron is about 10 ^-22 meters across, or at least as best we can measure something that small.

Nobody could be that thick. (-1, Troll)

Anonymous Coward | more than 3 years ago | (#33710354)

I would just love to start an inquisitive investigation to determine the source of all this peer-reviewed claims by a wheelchair-ridden creature that allegedly can't speak on his own.

I wouldn't doubt it if he was actually captured a long time ago by his arch-nemesis and enemies, forever used as their strawman to make broad unprofitable claims and assertions while the real meat of the matter is covered with actual science published to a patent. I think the latter is more evident, because no so-called King of Haw will ever name any amount of Radiation in such a way without having a good use for it: it just defies all purposes of discovery, as a s(p)oilled brat with too much attention.

Brool. Cory. Sto.

LHC will not kill us all! Future research... (2, Interesting)

Luyseyal (3154) | more than 3 years ago | (#33710358)

Yay, the LHC will not kill us all!

What I want to know is if this could be used to create a cool sort of battery or capacitor. I'm imagining layers of metamaterials to store the photons with only a certain amount of predictable Hawking radiation emitted. I doubt if it'd be better than chemical batteries but the geek cred would be way up there.

-l

Re:LHC will not kill us all! Future research... (0, Redundant)

Luyseyal (3154) | more than 3 years ago | (#33710386)

Furthermore, I dub it a "Hawking battery" or "Hawking capacitor" if it ever comes to pass!

-l

Re:LHC will not kill us all! Future research... (0)

Anonymous Coward | more than 3 years ago | (#33710660)

Sorry ... Too late ... I own an international patent issued by NPO (Nigerian Patent Office) on all electronic devices that use or utilize Hawking radiation (including batteries, capacitors, toasters, coputers, space ships, etc.)
 

Re:LHC will not kill us all! Future research... (1)

interval1066 (668936) | more than 3 years ago | (#33711340)

"Furthermore, I dub it a "Hawking battery" or "Hawking capacitor" if it ever comes to pass!"

Too late, and don't you dare. I've trademarked and patented both.

Re:LHC will not kill us all! Future research... (1)

confused one (671304) | more than 3 years ago | (#33710648)

You might want to create black holes. I'm sure you could imagine using them as an energy source... (just have to be a bit careful they don't over eat, if you know what I mean.)

I'm so white... (-1, Offtopic)

Anonymous Coward | more than 3 years ago | (#33710410)

I emit hawking radiation!

Double emission? (3, Interesting)

FalconZero (607567) | more than 3 years ago | (#33710432)

So when the virtual particle pair is created at the event horizon, one is trapped stationary beyond the horizon, and the other escapes (becoming real).

In this experiment obviously the event horizon doesn't persist indefinitely, so when the horizon collapses, do the 'trapped' photons escape? and hence is there a time delayed double emission of the hawking radiation? Would this provide a testable signature?

Any physicists know?

Re:Double emission? (5, Informative)

cb123 (1530513) | more than 3 years ago | (#33710542)

Popular visualizations and even the notion of "virtual particles" do not allow very accurate reasoning with regards to Hawking radiation. In particular, the "promotion process" from "virtual" to "real" is just a crutch for proving something to all orders in perturbation theory. Shortly after Hawking-Bekenstein, Bill Unruh proved that simply being in a uniformly accelerated reference frame creates a perception of thermal background radiation coming from the background -- at a temperature equivalent to the pseudo-event horizon of the acceleration for the duration of the acceleration. You see, while if you move at a constant rate any photon will catch you just as quickly as if you were standing still (basic special relativity) if instead you accelerate forever, you asymptotically approach the speed of light, but there are photons far enough behind you that will never catch you. How far behind they need to be depends on how fast you are accelerating. So, every acceleration corresponds to a pseudo event horizon. As soon as one stops accelerating the photons can catch up to you. Unruh's result does *not* depend on the permanence of the horizon, but works for temporary accelerations. So, the horizon does not need to be "permanent" for the "promotion" to occur. A better way to think about Hawking radiation is any gravitation field (any curved space, that is) decaying via thermal radiation, or space itself providing some "resistance to acceleration" or intrinsic acceleration-only viscosity where the energy taken away from the acceleration is converted to thermal radiation. The image of a virtual pair around an event horizon is not, ultimately, how the result holds or is proven or even what the process is "about". It's more like an "inspiration to a derivation" than something to be taken so literally.

Re:Double emission? (2, Interesting)

tgrigsby (164308) | more than 3 years ago | (#33715848)

So by your explanation, I give off Hawking radiation just by walking across the room? My understanding of Hawking radiation had to do with more of a shearing effect caused by extreme gravitational conditions parting two virtual particles to result in a single real particle. I'm not sure my ass qualifies as a sufficiently large gravitational well, nor can I picture a pseudo event horizon forming at any distance behind it while I walk.

Re:Double emission? (1)

c0lo (1497653) | more than 3 years ago | (#33710866)

TFA doesn't seem quite a novelty [st-andrews.ac.uk] - even more, the linked article contains some nice layman-term explanations, including how to create a white-hole in the kitchen sink; this may help you to guess an answer on what could happen when you shut close the tap (errr... what happens when the horizon collapses).

Re:Double emission? (0)

Anonymous Coward | more than 3 years ago | (#33715106)

If you read the *actual* article - the paper on the arXiv - you'll find that the authors acknowledge Leonhardt, which is generally done after discussions (real or by email) or some other kind of help that's been provided. The difference between what he does and the actual article is that Leonhardt works theoretically; he's been modelling this stuff for over a decade to my certain knowledge (I studied under him at St Andrews). This result is an experimental proof - and it's extremely exciting.

As an aside that might interest people, last year there was also a paper that came out of an Israeli university demonstrating the first acoustic black hole generated in a Bose-Einstein condensate. They didn't observe the Hawking radiation since the effective surface gravity of the hole (its velocity gradient) was over an order of magnitude too low, but there's every hope that that will change in the nearish future. http://de.arxiv.org/abs/0906.1337

Re:Double emission? (0)

Anonymous Coward | more than 3 years ago | (#33715204)

Hmm. In addition (that was me as AC above), I just actually read the page you linked to - I wasn't aware he'd started collaborating with experimentalists, which shows how out-of-touch I've been... Still, by the looks of that they generated an optical black hole, but it's a distance from there to observing the Hawking radiation so this is still an exciting and fascinating paper.

Re:Double emission? (0)

Anonymous Coward | more than 3 years ago | (#33716192)

im not a physicists but i stayed at a howard johnson last night, and i understand it as the virtual particle becomes real because the counter part is destroyed

Re:Double emission? (0)

Anonymous Coward | more than 3 years ago | (#33716606)

If he says he's had a double emission he's lying! ;)

Information Lost or Retained? (1)

Covalent (1001277) | more than 3 years ago | (#33710528)

IANAP, but if I remember correctly, Hawking first asserted that information was lost via Hawking Radiation but then retracted. I would be curious to see if radiation somehow gave information about the incoming light.

Science Fiction (-1, Troll)

BitZtream (692029) | more than 3 years ago | (#33710546)

Which is more or less what the article is. Yes there is SOME proof to back it up, but 99% of the 'proof' about black holes in general is really just theory.

Astrophysicists will make shit up to prove themselves right before they'll bother to look for real proof. At this point the theories are more or less freaking useless because they are based on theories based on theories based on theories based on theories. They just start making shit up so their theory fits.

They need to back up about 50 to 100 years and start proving some of those theories rather than just inventing shit to fill in the wholes where their previous theories made no sense.

When EVERYTHING you do is theoretical, its not science, its fantasy or fiction. Its not research if the only place it is confirmed to exist is in your head.

Seriously ... 'we think black holes emit a kind of radation, and we know what its like because we created it in a lab before ever actually observing it in nature.'

Thats not fucking science, its fantasy.

Magrathea (1)

txoof (553270) | more than 3 years ago | (#33710586)

So, with the advent of this new 'white hole' technology, we're really just a few short years from sucking matter through them to create our own custom luxury planets. I really want one of those rubber planets with lots of earthquakes.

Re:Magrathea (4, Funny)

dkleinsc (563838) | more than 3 years ago | (#33710674)

Well, to get a proper explanation of 'white holes', we really need to go to the experts:

Cat: So, what is it?
Kryten: I've never seen one before - no one has - but I'm guessing it's a white hole.
Rimmer: A *white* hole?
Kryten: Every action has an equal and opposite reaction. A black hole sucks time and matter out of the Universe; a white hole returns it.
Lister: So, that thing's spewing time ... back into the Universe?
Kryten: Precisely. That's why we're experiencing these curious time phenomena on board.
Cat: So, what is it?
Kryten: I've never seen one before - no one has - but I'm guessing it's a white hole.
Rimmer: A *white* hole?
Kryten: Every action has an equal and opposite reaction. A black hole sucks time and matter out of the Universe; a white hole returns it.
Lister: So, that thing's spewing time ... back into the Universe?
Kryten: Precisely. That's why we're experiencing these curious time phenomena on board.
Lister: What time phenomena?
Kryten: Like just then, when time repeated itself.
Cat: So, what is it?
[Kryten, Rimmer, and Lister stare at Cat]
Cat: Only joking.

Re:Magrathea (0)

Anonymous Coward | more than 3 years ago | (#33710908)

Oh, a magic door! Why didn't you say?

I don't understand... (1)

camperdave (969942) | more than 3 years ago | (#33710604)

I don't understand how Hawking radiation causes a black hole to evaporate. Okay, a particle/anti-particle pair gets created from the ambient energy near the event horizon. Okay, one of the particles falls in and the other escapes. With you so far. Now, either way, the black hole gains the mass of that one particle that fell in, thus it gets heavier. Even if the physics inside the black hole allowed the trapped particle to meet an anti-particle and get annihilated, that energy (and thus the mass) would still remain inside the black hole.

Granted, the escaping particle is carrying away energy (and thus mass), but that energy must have come from outside the event horizon, not inside. The outside universe got lighter, not the black hole.

What am I missing?

Re:I don't understand... (1)

ath1901 (1570281) | more than 3 years ago | (#33710738)

Put the black hole in an empty box. The particles that escape the event horizon will eventually find their way out of the box, i.e. radiation comes out of the box.

Because of energy conservation, the contents of the box must loose energy and thus mass. Since there is nothing in the box except a black hole, it must loose mass.

Re:I don't understand... (1)

vlm (69642) | more than 3 years ago | (#33710830)

Because of energy conservation, the contents of the box must loose energy and thus mass. Since there is nothing in the box except a black hole, it must loose mass.

I think whats missing is the energy transport mechanism. Convection (whats circulating, certainly nothing from inside the event horizon...) Conduction (touch the event horizon and fly away?) Radiation (the hot surface is inside the event horizon so light can't escape, right?)

Saying the energy transport mechanism is magic is no better than saying energy does not have to be magically conserved in that environment.

Re:I don't understand... (3, Interesting)

cb123 (1530513) | more than 3 years ago | (#33710926)

The process need not actually be distributed over space -- the escaping particle travels, yes, but the actual energy conversion happens when and where the escaping is first created.

Now, its creation is a quantum state transition which has a "magical" quality in the same way that, say, a photon escaping an atom's electron shell does. There is no extended energy transport process at all. The electron makes a quantum jump simultaneously with the photon field of the world gaining a new photon traveling away. Indeed, with visible light, the wavelength of the photon -- hundreds of nanometers -- can easily exceed the spatial scale of the atoms electron shell, usually a few nm. So, the photon kind of just "appears".

Re:I don't understand... (3, Informative)

cb123 (1530513) | more than 3 years ago | (#33710838)

The responder has it right. You are missing that the virtual pair has no net energy initially and one escapes. So, the outside world is getting heavier and the black hole lighter - to conserve total system energy. You are thinking of the "virtual" counterpart as having mass, but it does not. It's "virtual".

As I mentioned above, one does not need a black hole for this -- all curved space should release thermal energy, though the rate is usually immeasurably small. Google Unruh effect and read about it in relation to the Sokolov-Ternov effect which has been observed since the 1970s. There is not perfect interpretational consensus about all this, though.

Re:I don't understand... (1, Interesting)

Anonymous Coward | more than 3 years ago | (#33712384)

The explanation I've often seen is that in the virtual pair, one particle has negative mass. If the negative mass particle is captured by the black hole and the positive mass escapes, then the mass of the black hole is reduced. There are two things about this I have never understood:

1) Is the negative mass concept just a convenient analogy to explain Hawking radiation to laymen, and not a real explanation of the underlying physics?

2) Isn't it equally probable that the positive mass particle is captured and the negative mass particle escapes, resulting in no net change of mass in the black hole over time?

Re:I don't understand... (2, Informative)

cb123 (1530513) | more than 3 years ago | (#33712766)

Virtual particles are really terms in a perturbation expansion that in some respects are terms similar to real particles and in other respects are not. For example, traveling backward in time is something they get to do, having negative energy, and so on. What they can and cannot do and why is context dependent and relies upon the actual formal derivations and properties of what is going on. So, as a "reasoning device" they fail most laymen, and in my opinion are not very intuition building.

So, to answer (1), yes -- just an analogy. (2) would be correct if the answer to (1) were "no", but it isn't. :-)

As I've referred to above, "capture" and "escape" of "virtual" particles is all a bunch of highly specific visualization related to a black hole or event horizon, but the actual result pertains to all accelerating reference frames and all spacetime curvature. Though Hawking himself might disagree with me, I find it pedagogically misleading to "explain" the possibility of this thermal radition in terms of processes only happening at a literal even horizon.

This is actually an interesting case of the strong principle of equivalence -- that gravity is locally indistinguishable from an accelerating frame of reference for all physical processes. (The weak principle of equiv is only about graviational forces, but the quantum vacuum is broader physics than that.) Specifically, you can derive Unruh radiation from quantum vacuum transformations *or* you get the same numerical temperature as starting from the idea that an accerelating reference frame "event horizon" is the same as a gravitational event horizon. I derived that latter in high school in the mid 80s, actually, to prove to myself that strong P of E held in this case. It's a relatively easy exercise in hyperbolic functions and basic calculus to compute the asymptotic trajectory of uniformly accelerating frame and back out the effective accerelation event horizon. Plug that in to Hawking's formula for a black hole and you get Unruh's result for acceleration. (They really call it Fulling-Davies-Unruh since it was done three times independently after the Hawking-Bekenstein results.)

I would agree with another responder here that not mentioning the thermal character of the radiation and words suggesting its monochromicity makes this particular result a little dubious, but I have not read the arXive article.

Sounds like B.S. to me. (1)

mcmonkey (96054) | more than 3 years ago | (#33715050)

Why does the outside world get 'heavier' as the black hole gets 'lighter'?

That certainly makes sense if, in the virtual pair, the particle escapes the event horizon and the anti-particle falls in to the black hole.

But isn't it just as likely the anti-particle escapes and the particle falls in the black hole? Doesn't that mean there is no net energy gained or lost? All the particles and anti-particles escaping cancel each other out.

Now, you could say, when a particle and anti-particle meet, the energy released is equivalent to the energy lost from the black hole. Except these are particles 'born' outside of the black hole to begin with. This is just energy outside of the black hole that has moved from one place/form to another.

Where in this process does the black hole lose energy?

Re:I don't understand... (1, Informative)

Anonymous Coward | more than 3 years ago | (#33711066)

What you are missing is the laws of thermodynamics, where the universe ends up trying to "balance the books" in terms of mass and energy. Steven Hawking proposed this concept based upon the laws of thermodynamics in a broad sense, where mass and energy are always conserved.

In this case you can think of the particle falling into the event horizon from the virtual pairs as a sort of "negative mass". I know that isn't completely accurate from a pure physics perspective, but it is sufficient for mere mortals like you or I. The mass and energy to create these particles didn't come from the universe as a whole, but rather are random fluctuations that always happen in the universe on a rare occasion and generally can be ignored except in special circumstances. A black hole event horizon is such an extreme situation that such events do matter.

Perhaps another way to look at it is that on a quantum level the black hole event horizon isn't absolutely perfect and there are some "ripples" and "bumps" on the event horizon. These random bumps are where the radiation is formed and indeed it is a small hunk of the mass of the black hole that is leaving. Again, this isn't a really good explanation in terms of a formal scientific explanation, but it does get the job done for mere mortals.

Keep in mind that for most large mass black holes, the amount of radiation produced by these things from Hawking radiation is astonishingly small. For something that has the mass of our Sun, it would be measured as having a temperature that is colder than the background radiation caused by the Big Bang. In other words, simply by sitting there it is collecting more energy (hence mass) from the universe as a whole from the residual radiation of the Big Bang than it emits.

The cool thing about the LHC and some of the research that think they'll be able to create black holes in a laboratory is that these are going to be tiny, low mass black holes if they ever are created. In this case the radiation levels are going to be incredibly high and the lifetimes of these black holes are going to be very short. Short as in just a small fraction of a second or so. The large black holes like the one at the center of our galaxy are going to be hanging around for trillions of years or more... certainly longer than anything we would recognized as this universe is going to exist.

Re:I don't understand... (1)

Bengie (1121981) | more than 3 years ago | (#33713916)

My understanding is that the hole has gravity. The gravity is doing work on matter surrounding the hole and/or else where in the universe as gravity extends out to infinity. Work requires energy. Mass and energy are the same.

When the hole does work outside of itself via gravity, it loses mass/energy and will eventually disapear.

I have a question regarding micro blackholes that someone may help me with. Lets say you have your two protons in the LHC smash into eachother. A bunch of energy/mass is given off as other particles. Then you get lucky enough to create a blackhole. Now this blackhole is really just an event horizon based on the mass of the original particles minus lass mass/energy given off from the collision.

We're talking about a freaking small event horizon. From what I've read, particles act as waves on the very small scale. Would this micro black hole even be able to consume a particle if it's forced to interact with the particle as a wave because of its size?

Wait a minute (0)

Anonymous Coward | more than 3 years ago | (#33710676)

Don't you mean Fry-radiation?

Invisibility cloak (1)

ciderbrew (1860166) | more than 3 years ago | (#33710722)

If light cannot penetrate a field, does that mean that what is inside the field cannot be seen?
You'd not be able to see the other side of it, so it won't be invisible.I'm not too sure what you'd see - My mind hurts - not much pain - but enuff(sic).

Re:Invisibility cloak (0)

Anonymous Coward | more than 3 years ago | (#33710954)

Light can't penetrate walls and what you see is the light reflected by them. Objects on the other side are hidden. If a field doesn't reflect neither emits light, you'll see a black surface very much like a wall painted black.

Graviton Diode? (2, Interesting)

Doc Ruby (173196) | more than 3 years ago | (#33710746)

We also now create black holes in labs. Could we create pairs of white holes and black holes together in a lab, and study the gradient between them for gravitons? Would we be able to pair them into gravity diodes? If so, could a gravity laser be made from them?

Could we use a gravity laser to focus Hawking radiation onto "blank" quanta to reconstitute the entropic hologram of the complex structure that a black hole reduces to those "blank" quanta when it emits the Hawking radiation?

If so, could we entangle pairs photons, send each member of each pair across space in opposite directions, then work one of the pair against the Hawking radiation to encode it across to the other of the photon pair, which in turn modulates "blank" Hawking radiation at the far end through a gravity laser, reconstituting the quantum entropic state of remote blanks? If so, we'd have teleportation that could run at least double the speed of light on demand (entangled photons rushing at c to opposite points = 2c), and if prepared in advance simply instantaneous teleportation.

Will Hawking finally deserve the "greatest brain of our time" reputation that TV acts like he does?

Re:Graviton Diode? (0)

Anonymous Coward | more than 3 years ago | (#33715314)

(entangled photons rushing at c to opposite points = 2c)

I don't think relativity works that way.

Re:Graviton Diode? (1)

Doc Ruby (173196) | more than 3 years ago | (#33715518)

But quantum mechanics does - much to Einstein's consternation over "spooky action at a distance". While distributing entanglement for 2c communication has been experimentally verified only for observation, not changing state remotely, the latter will surely be tested soon. Until then, it's still theoretically possible, and we'll see how it works in practice.

white holes... black holes... (0, Offtopic)

Essequemodeia (1030028) | more than 3 years ago | (#33710828)

I can't fucking stand the racism in scientific research these days. They are ALL holes. Your momma taught you better....

great for physicists, but... (0, Flamebait)

DragonTHC (208439) | more than 3 years ago | (#33710916)

what are the practical applications for the real world? How will this help prevent our extinction?

Re:great for physicists, but... (1)

Thanshin (1188877) | more than 3 years ago | (#33711740)

what are the practical applications for the real world? How will this help prevent our extinction?

Easy. Before our extinction by blackhole impact we apply our knowledge on blackhole dissipation and dissolve it.

Paper Hole (1)

eyenot (102141) | more than 3 years ago | (#33711122)

July 22nd, 2004: ' ' Now Hawking has conceded defeat by saying that information can escape from a black hole and therefore is not lost. "It is great to solve a problem that has been troubling me for 30 years," said Hawking, "even though the answer is less exciting than the alternative I suggested." ' '[http://physicsworld.com/cws/article/news/19926]

If my calculations are correct, then you can just simulate a black hole on paper, write some formula describing information emitting from the black hole, and perform just as much as these people did with their convoluted, inverse-proof, "white hole".

Besides, none of this matters. The entire reason why the sky is so dark and has more light on one side than the other isn't "broken symmetry" and "gravity bends spacetime" and so on, it's that the planet Earth and the visible "universe" are just a small portion of what actually exists except it's been sucked into a black hole that we can't see out of (information). It's disproportionately tilted to one side because it's vortexing into the center where everything gets crushed simultaneously.

"hawking" (1)

gr8_phk (621180) | more than 3 years ago | (#33711156)

Whenever I read the term "hawking radiation" I think of the black hole hawking some radiation. Or perhaps radiation emitted in the process of hawking something else. Fortunately this mind glitch does not happen when I read this in the context of the guys name.

Coincidence? I think not. (1, Insightful)

Anonymous Coward | more than 3 years ago | (#33711170)

Isn't it a bit too coincidental that a guy named Stephen Hawking would discover something called Hawking radiation. I call BS.

Re:Coincidence? I think not. (3, Funny)

Yvan256 (722131) | more than 3 years ago | (#33711424)

Nichelle Nichols: "It's about that rip in space-time that you saw!"
Stephen Hawking: "I call it a Hawking Hole."
Fry: "No fair! I saw it first!"
Stephen Hawking: "Who is the Journal of Quantum Physics going to believe?"

Event Horizon (2, Funny)

Yvan256 (722131) | more than 3 years ago | (#33711372)

Yeah I remember now... the story was intriguing and promising at the beginning and then it all went trough hell.

Oblig. Futurama (1)

Darth_brooks (180756) | more than 3 years ago | (#33711406)

hey say they brought light to a standstill by drastically increasing the refractive index of the material it was being fired at -- creating a 'white hole.'

"I call it a Hawking Hole."

Clairvoyance (0)

Anonymous Coward | more than 3 years ago | (#33711634)

They brought light to a standstill? I'd love to see that.

oh really? (1)

ILuvRamen (1026668) | more than 3 years ago | (#33711822)

The way I remember it is Hawking radiation is when a set of virtual particles get split up, leaving antimatter on the edge of an event horizon. Then that antimatter reacts with matter and gives off all kinds of radiation including light so black holes sort of "glow." So given the estimated energy levels of antimatter and matter reactions, wouldn't one of those antimatter particles contacted some matter and blown them all the hell up?

Probably not hawking radiation. (4, Informative)

SETIGuy (33768) | more than 3 years ago | (#33712166)

It sounds like the light they see is monochromatic. Hawking radiation would be blackbody radiation. Unless they have a reason why this blackbody would only have one mode and an incredibly high effective temperature. I'm guessing that they've found an uninteresting fluorescence feature.

Technology review's arXiv blog is so difficult to get any details out of. It's hard to figure out what these people have done. "frequency of 1055 nm"? I guess I'll have to go to the full article.

Re:Probably not hawking radiation. (2, Funny)

DriedClexler (814907) | more than 3 years ago | (#33713162)

Technology review's arXiv blog is so difficult to get any details out of. It's hard to figure out what these people have done. "frequency of 1055 nm"? I guess I'll have to go to the full article.

Yeah, and you know what's even worse? Some assholes report the mass of fundamental particles using electron-Volts which is a unit of *energy*, not mass. Retards.

Re:Probably not hawking radiation. (1)

smaddox (928261) | more than 3 years ago | (#33714674)

Most likely they meant eV/c^2. This is a standard units used for mass of elementary particles (by physicists). Since E=mc^2, and eV is a measure of energy, eV/c^2 is a measure of mass.

In these units, the electron has a rest mass of 511 KeV/c^2.

What To Expect During First Contact (1)

jdgoulden (1575977) | more than 3 years ago | (#33712176)

The other day I was clearing debris from a fenceline. I turned over a rotten log to reveal a termite nest. I watched for a moment as the panicked insects scurried about with their larvae and such, then kicked their home aside and went about my business.

This is what First Contact will be like for us. If we're lucky. Note that I didn't bother to exterminate the critters.

Only an analogue (1)

bjorniac (836863) | more than 3 years ago | (#33713104)

This isn't Hawking radiation, it's only an analogue. Now, that's not to say that it isn't an interesting and cool piece of research, but it certainly is not the black body spectrum produced by the evaporation of a black hole. So all they've really seen is that IF a real black hole behaves in the same way as their system, it will emit hawking radiation in the same way.

Hawking radiation and the first law (1)

metrix007 (200091) | more than 3 years ago | (#33713736)

Can someone please explain to me why Hawking radiation does not violate the first law of thermodynamics?

As I understand Hawking radiation, two particles emerge from a black hole and circle each other, and eventually get sucked back in disappearing into where they came from. Although sometimes when they are near the event horizon, only one of the particles gets sucked back in, and the other stays behind which is known as hawking radiation.

Is this not the same as energy seemingly being created, just appearing out of nowhere? Or is it mass, and the first law does not apply?

Re:Hawking radiation and the first law (1)

MozeeToby (1163751) | more than 3 years ago | (#33715726)

In the model of Hawking radiation you're thinking of a pair is produced, a particle and an anti-particle. The anti-particle gets sucked back into the black hole (thus reducing the black hole's mass) while particle escapes in the form of Hawking radiation. As someone has pointed out in a few other comments, there are probably models that explain the phenomenon better than the virtual particle model, but if my layman's knowledge of physics has taught me anything it's that one phenomenon can have several (very, very nearly) accurate models that explain it.

Re:Hawking radiation and the first law (1)

metrix007 (200091) | more than 3 years ago | (#33716280)

Thanks for the explanation, but I am still confused in regards to my question. Is a particle coming out of seemingly nowhere violating the first law? If not, why not?

Oh yeah? (0)

Anonymous Coward | more than 3 years ago | (#33714980)

Well, I predict that they emit Anonymous Coward radiation.

Going out on a limb here (1)

fishexe (168879) | more than 3 years ago | (#33715968)

In 1974, a young newcomer to the Royal Society named Stephen Hawking predicted that black holes emit Hawking Radiation.

I'm gonna go out on a limb here and guess that in 1974 a young newcomer named Stephen Hawking predicted that black holes emit a certain kind of radiation, and somebody later named in Hawking Radiation.

Re:Going out on a limb here (1)

fishexe (168879) | more than 3 years ago | (#33715980)

...and somebody later named in Hawking Radiation.

"named it", rather. Way to shoot my own comment in the foot.

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