Hawking Radiation

day07 · Aug 26, 2005

What exactly is Hawking Radiation? I know this principle details the time (by mass) that it will take for a black hole to evaporate and fade into nothing. When researching papers and articles detailing Hawking Radiation, the math is usually far too complex for me to form a mental image of the described phenomina. This leaves me with many questions.... - What is Hawking Radiation? - How is it Proven? - Is there any relation to the TimeScales described and the overall evolution of the Galaxies or even the Universe? - What does Hawking Radiation tell us about the Black Hole Information Paradox?

vogon13 · Aug 27, 2005

Virtual particle and anti-particle pairs are continually created throughout the universe (quantum fluctuations). The particles come and go, and usually that's the end of it. Except near a black hole. In the fleeting instance the pair is around, it is possible for one of them to fall into the black hole. This 'frees' the other particle, to escape the vicinity of the black hole. Since you don't get something for nothing, to make the books balance, the escaping particle is considered to have 'evaporated' from it. The energy of these particles is related to the mass of the black hole. The smaller the black hole, the more energetic the escaping particle. Converse is also true. So really big black holes 'evaporate' very slowly. Like 10^90 years slow. (IIRC, the whole thing) <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

day07 · Aug 27, 2005

Thanks Again <img src="/images/icons/smile.gif" />

igorsboss · Aug 27, 2005

Virtual particle and anti-particle pairs are continually created throughout the universe (quantum fluctuations). The particles come and go, and usually that's the end of it. ... Since you don't get something for nothing, to make the books balance, the escaping particle is considered to have 'evaporated' from it. I had an idea the other day, and this is a perfect introduction to explore it, so here it goes. If the particles and anti-particles appear and disappear at precicely the same rates, then it is reasonable to say that these two rates result in an equlibrium condition. Further, we observe that even in a vaccuum, there seems to be some kind of energy, which we call dark energy, which shows up in Einstein's equations as a nonzero cosmological constant. Now, suppose that rates of particle appearances and disapearances were not precicely the same? Would the observed macroscopic effect mimic dark energy? Perhaps the quantum fluctuation construction/desctruction rates are ever-so-slightly out of equilibrium, possibly due to the expansion of the universe, and we observe the disequilibrium as dark energy. Comments?

Saiph · Aug 27, 2005

except that could very well cause the opposite reaction, as it's a net energy loss, and creates matter, it may slow expansion. Anyway, as for why virtual particle pairs cause "evaporation". When the BH captures one of the pair, it must supply an amount of energy equivelant to the binding energy of the pair...which is basically the energy stored in two particles. By supplying this energy, it strips the pair apart, loses two particles worth of energy, but only absorbs one particle. As such, there is a net energy loss for the BH, and it is independent of whether it was the regular or anti-particle being absorbed. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

siarad · Aug 27, 2005

By what means is this energy supplied as it can't be e/m energy as it can't escape BH

vogon13 · Aug 27, 2005

You're putting negative energy in the BH. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

Saiph · Aug 27, 2005

Siarad: Gravity is doing it, specifically tidal forces. The BH pulls on one harder than the other, due to proximity, tearing the system apart. steve's method of tunneling is another way for hawking radiation to occur. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

frobozz · Aug 27, 2005

Question on QM here, I apologize for going slightly off topic, but isn't the probabilitic nature of QM based on the effects of what we can and cannot observe and not the actual laws themselves? Specifically, I always understood (perhaps naively) that it was based on the idea that if knew position you would not be able to pinpoint momentum and vice-versa. If that's the case, then we are only describing what can be observed probalistically, which does not make the laws themselve probalistic.

Saiph · Aug 28, 2005

That is an important point in quantum mechanics. Are we merely limited to a probabilistic description, or is the reality truely probabilistic. This question isn't ignored, and you should be able to find all sorts of references to it in the literature. Hawking, Feynman, and others all discuss it in their works. Hawking, IIRC, takes the stance of the math being reality. Whatever the math (if valid) says is occuring, really is occuring. The math isn't just a tool to create one of many possible interpretations. The math describes what is really happening. Some support for this is that there are two or three different mathematical underpinnings in quantum mechanics. One is the wave nature of matter, using differential equations (a.k.a. the shroedinger equation). Another is using matrices and their mathematical properties (Bra-ket notation). There are a few others that have been created and also work. The catch is, all these mathematical constructs, whose rules of mathematics from different fields are used to describe what is going on, all give the same answers. The matrix mathematics give the same answers as the wave equations. From what i've picked up, the general consensus of the field is tending towards a truely probabilistic reality, due to various observations and experiments (details are vague in memory, due to the time since I've looked at it). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

frobozz · Aug 29, 2005

Well, I'm not sure I'm any more comfortable with the concept of a probabilitic reality then Einstien was, but then again, I do math not physics, so I'm really not qualified to make that decision. Returning to the subject at hand, has anyone managed to experimentally show the existance of this virtual particles?

vogon13 · Aug 29, 2005

IIRC, detailed explanation of brehmstrahlung (sorry for spelling!) seems to ~confirm all this? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

Saiph · Aug 29, 2005

The cassimir effect may also be explained by the presence of virtual particles. Then again, it may just be a manifesation of the weak force. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

frobozz · Aug 30, 2005

Hmm, not to be a repeative pain as I admit my physics is very much limited to what turned up in my math, but I fail to see how you could prove that the universe is probabilistic on a Quantum level. If you're willing I would like to see where you saw this or if you can explain it briefly I'd be happy. If it helps the reason why I am skeptical is from an observers stand point, if you don't know the rules, how do you tell the difference between a purely probabilitic universe and one generated by a chaotic dynamical system? I conceed that QM describes the universe well, as I am not in the position not to, nor do I have reason to believe it doesn't, but you could describe the output of a chaotic system equally well using probabilistic methods, so how can we tell the difference?

mrmux · Aug 31, 2005

Does that mean the final 'pop' of an evaporating black hole should look exactly the same as for any other? Would seem to be a possible marker for distance calculations (if it's energetic enough). The thought of the tiniest possible black hole being finally 'sealed' by the last half-a-particle-pair just blows my mind. Has there been enough time for this to actually happen?

Saiph · Aug 31, 2005

The final pop is energetic, but not nearly energetic enough for any real distance calculation. For instance i don't believe it would outshine a faint star. And it's very short in duration too. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

mrmux · Sep 1, 2005

Well, I've finally just put a call to Manchester University's Physics and Astro dept. I'm applying to be a mature student. Should have done this years ago.

yevaud · Sep 1, 2005

Vogon: Bremstrahlung and external Bremstrahlung - Ionizing and non-ionizing radiation. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

Saiph · Sep 1, 2005

Congrats MrMux. I hope you enjoy it as much as I did. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

mrcurious · Jun 19, 2007

Hawking Radiation happens.... If one particle of a pair of virtual particles falls into a black hole and the other one doesn't they can't react back to energy and the escaping one becomes a real particle leaving behind a lack of energy in the vacuum. Somehow this "hole" in the vacuum energy has to be filled again - even in quantum physics the law of energy preservation can't be disobeyed for a longer time. So this "hole" draws energy from that black hole. But what kind of energy does a black hole without any spin or charge have? It's mass! Thus a black hole loses some of its mass after Einstein's famous formula E = mcÂ². Maybe you have noticed that that's no proof that the energy has to originate from the black hole. In fact we can't really prove it without a lot of quantum physics (It depends on the tunnel-effect). You just have to swallow it as being true. Another, yet similar, way to explain the black hole's loss of mass is that the particle that gets sucked into the black hole gains a negative mass and thus the mass of the black hole decreases... excerpt from http://library.thinkquest.org/C007571/english/advance/english.htm If one particle of a pair of virtual particles falls into a black hole and the other one doesn't they can't react back to energy and the escaping one becomes a real particle leaving behind a lack of energy/i> Why does the escaping particle become the real particle? What removes the ability from the infalling particle of becoming a real particle? Why can't the infalling particle become the real particle?

mrcurious · Jun 20, 2007

Uhhh...........are these stupid questions?

Saiph · Jun 20, 2007

absolutely not...it appears my last response got consumed by the aether... <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

Saiph · Jun 20, 2007

basically the black hole seperates the two "virtual" particles the same way we seperate paired magnets...by overcoming the binding energy of the pair. In doing so the black hole irreversiblly seperates the two "virtual" particles (that are very real, they just don't last any significant, and observable lenght of time). One gets consumed...and we still can't interact with that one, and one goes free, to affect our instruments (thus is "real"). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

mrcurious · Jun 20, 2007

But, that other particle is also real as well, correct? We just can't say whats happening to it because we can't see inside of a black hole, correct? One gets consumed...and we still can't interact with that one, and one goes free, to affect our instruments (thus is "real"). But, aren't both particles, real? The infalling particle we can't describe whats happening to it because its in the black hole. Isn't hawking assuming that all the infalling particles are negative mass particles? Is he not giving rise to the possiblity that the lack of vacuum energy that needs to be "filled in" would come from particles outside the event horizon? Wouldn't this effect present a loss of mass to the surroundings of the black hole...ie...gas, dust, & clumps of matter? Wouldn't this also alllow the black hole to grow because the infalling particle would be positive mass?

mrcurious · Jun 20, 2007

So the black hole gains a little mass due to the infalling particle but looses more energy due to splitting the pair. It gains mass and loses energy? I thought it looses mass due to the infalling particle having negative energy. So both particles are real? So, then would it be more appropriate to state that the escaping particle becomes visible while the infalling particle becomes hidden? This process allows black holes to radiate away. So can the opposite happen which would cause black holes to grow?

Hawking Radiation

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