Evaporation Of A Black Hole

[jeremyb]

Hi, new here still, been doing some reading about black holes here and what you all have to say about them. One question popped up for me while reading about black holes and the event horizon paradox stuff.

 

If a black hole evaporates, where does its mass go?

 

Say for example our own galaxies black hole, once it is done eating up everything it can in our galaxy, science says it will start to evaporate correct...but where will the mass go?

This black hole will contain so many elements, what happens to these elements? Are these elements all fused into something that slowly turns into nothing?

 

I have no schooling past high school, so all I can go on are theory's of my own. I once came up with an idea that mass had a limit, the same way speed has a limit and cold has a limit. The theory is that once an objects mass reaches this limit, it either explodes or disintegrates, I just cant choose what works best for the theory, but I am also fairly certain that the theory is incorrect, so that makes it irrelevant.

 

Thanks and looking forward to your replies.

[Qfwfq]

If a black hole evaporates, where does its mass go?

Hawking radiation.

[Cyberia]

How Hawking radiation works. You have a steep slope a thousand miles long. At the 750 mile mark, you place two balls next to each other. One rolls down hill (so falls into the black hole) and the other rolls uphill (so escapes the black hole).

 

Sound likely?

 

Matter cannot escape a black hole so what is in there will stay there.

 

Some say black holes have a limit of mass (I don't see why they should) but the most massive so far, discovered a few years ago, is 18 billion solar masses.

[CraigD]

How Hawking radiation works. You have a steep slope a thousand miles long. At the 750 mile mark, you place two balls next to each other. One rolls down hill (so falls into the black hole) and the other rolls uphill (so escapes the black hole).

 

Sound likely?

 

Matter cannot escape a black hole so what is in there will stay there.

Says who, besides you, Sexton? By which I mean, can you cite a peer-reviewed scientific paper supporting the description of Hawking radiation you give here?

 

I believe you misunderstand the basics of the theory of Hawking radiation.

 

The key flaw I see with your explanation of the impossibility of Hawking radiation is that it appears to assume that the radiation – one of the two balls in your description – originates inside the black hole. This is an incorrect statement of Hawking’s theory. It states that the radiation originates, in the form of virtual particle pairs, near but outside the black hole. Rarely, one particle falls into the black hole, the other escapes it, as any body with the necessary velocity can do outside a black hole. Thus, the virtual particle pair can’t interact with one another to “cease to exits as real particles”, and the one that escapes as a real particle carries energy, which is called Hawking radiation.

 

So, as you, and Hawking’s theory, state, “matter cannot escape a black hole”. Hawking’s theory, however, states that this doesn’t guarantee that “what is in there will stay there”.

 

How this results in the black hole losing mass-energy, and the universe outside it gaining exactly the same amount, involves physics beyond my (but not beyond Hawking’s and other professional and serious amateur physicists’) normal ken, by which the captured particle, as it cannot interact with the universe outside the black hole, has negative mass-energy, but this is not important to the explanation of how Hawking radiation occurs, only to the hypothesis that it reduces the mass of black holes, allowing them in extraordinary circumstances to “evaporate.”

 

It’s important to understand, I think, that Hawking radiation is mostly useful as an explanation for why very small black holes, which theory predicts can be created by such events as the collision of high-energy cosmic radiation with matter in places such as space or Earth’s atmosphere, aren’t formed constantly in large numbers, growing bigger by capturing matter and EM radiation, until they eventually become detectable, most dramatically by “eating the Earth” and pretty much all the rest of the matter in the universe. Because the physics-derived formulae give the power (rate of energy radiated per unit time) of a black hole’s Hawking radiation as inversely proportional to the square of its mass, very small black holes have very high power, so evaporate very quickly. Hawking radiation, therefore, provides a widely accepted explanation within the framework of well-accepted physics for why we don’t see a universe consumed by or in the process of being consumed by every growing tiny black holes.

 

Some say black holes have a limit of mass (I don't see why they should) but the most massive so far, discovered a few years ago, is 18 billion solar masses.

That mass is about right, though more massive ones are being discovered constantly. To the best of my (and wikipedia’s) knowledge, the largest known, as of December 2011, is at the center of NGC_4889.

 

I know of no theoretical limit to the mass of a black hole. I believe calculation of their maximum possible mass are based on how much mass-energy, at this time and in the visible universe, any single one could have captured.

[Cyberia]

Craig D. There are many peer reviewed scientific papers on superstrings. Give me any evidence that they exist?

 

The great Stephen Hawking:

 

He even hinted at regrets in his personal life after being asked about his biggest mistake.

 

He said that thinking information was destroyed black holes was his biggest blunder - 'or at least my biggest blunder in science.'

 

http://www.dailymail.co.uk/news/article-2082440/Stephen-Hawking-Women-complete-mystery-says-Quantum-physicist.html

 

He also gave up on singularities in his book "A brief history of time."

 

 

Can you show where I said that the balls originate inside the black hole?

 

I specifically said "One rolls down hill (so falls into the black hole)".

 

If you have two sub atomic particles next to each other in a black hole's gravitational field at the point where one will fall in, it is stretching credibility to claim that the other will not fall in too. Remember the kind of separation distances we are talking about here.

 

You miss the point. How can a black hole lose energy from inside itself? It can only lose energy from outside and it cannot lose gravitational energy because that comes from the mass inside and gravity from mass is "endless" so to speak. The Moon does not lose mass because it has gravity.

 

To quote the wikipedia before it builds castles on clouds:

 

The power emitted by a black hole in the form of Hawking radiation can easily be estimated for the simplest case of a nonrotating, non-charged Schwarzschild black hole of mass M.

 

 

Which is like talking about if pigs could fly. Black holes spin. Black holes have charges. Full stop.

 

And the wiki again:

 

In theoretical physics, negative mass is a hypothetical concept of matter whose mass is of opposite sign to the mass of normal matter.

 

 

Which must be how pigs can fly. Amazing what you can do with a good imagination, as in purely theoretical physics with no real world basis.

 

It was said decades ago that you would need maybe 1600 tons of matter to create a stable black hole. So if you have masses less than this created as you say by high energy cosmic ray collisions, they vanish almost as fast as they form. There is not sufficient gravitational force to hold them together.

 

Is the idea of a universe in "heat death" based on ever larger black holes or just lots of "small to fairly large" ones?

[Qfwfq]

Craig D. There are many peer reviewed scientific papers on superstrings. Give me any evidence that they exist?

You have this somewhat backwards. Craig did not mean that peer reviewed articles make a theory real, he only means that if you don't back yourself up with them you need an argument with better grounds than "Sound likely?", which also assumes the Hawking mechanism relies on gravity to eject one of the particles. It doesn't, the computation simply counts the probability of one of the two having sufficient momentum in the outward direction. Your rejection is based only on misunderstanding.

 

Black holes spin. Black holes have charges. Full stop.

Apart from the fact that they aren't guaranteed to have spin and charge, zero spin is not a requisite of the mechanism but a simplification, I imagine some dude has worked it out for the Kerr metric too; I can go as far as imagining ejection will be favoured for particles with orbital angular momentum concording with the BH's spin. As for charge, the case is more trivial; it is only an obstruction to ejection of opposite charged particles whereas it helps eject those with like charge and this very dissymmetry means the BH will radiate its charge away.

[maddog]

Can you show where I said that the balls originate inside the black hole?

I specifically said "One rolls down hill (so falls into the black hole)".

If you have two sub atomic particles next to each other in a black hole's gravitational field at the point where one will fall in, it is stretching credibility to claim that the other will not fall in too. Remember the kind of separation distances we are talking about here.

You miss the point. How can a black hole lose energy from inside itself?

Actually Sexton, it looks like you miss the point, and if were you I wouldn't deliberate it further.

 

These virtual particle pairs look as time reversed version of annihilation pairs - thus according to

Newton's Second Law have equal and Opposite momentum.

 

As you call it "one falls in" then in the opposite direction "one does fall out". True depending on angle

of first particle falling isn't necessarily in same direction as pointing to the center. So one may consider

a counter example where one goes instead tangential to the event Horizon (or just outside). The

other would go in the opposite direction. In this case there may not sufficient momentum for either.

 

This would be a small set of possible created pairs thus a significant loss of mass over time due

to Hawking Radiation would be likely.

 

This isn't that complicated. <_<

 

Now as to jeremyb's other remarks: I don't think there is (AFAIK) a mass limit to a BH (cold is actually the

loss of heat which does have a limit called 0 Degrees Kelvin or Absolute Zero -- maybe this is what you

are referring to). It is thought that BH at the center of galaxies have about 10^9 solar masses or so.

B)

 

maddog

[Cyberia]

Qfwfg. Probability? Zero. As I said, these particles are next to each other on a quantum level. What affects one will affect the other, and a zillion other particles around them. Why should one particle have so much more momentum than the other particle since they had a common origin?

 

A misunderstanding? A meaningless term unless you can explain what it is.

 

It is said that black holes are "messy eaters" and can lose maybe 90% of the mass heading towards them.

 

Anything a black hole loses will be this side of the event horizon.

[Cyberia]

CQA. But you are not me and even if I believe something I will still question it to death. That is what science is about rather than saying "Accepted science is this, this and this. That's good enough for me." Thinking is allowed.

 

"time reversed version of annihilation pairs"?

 

Annihilation pairs, other than matter-anti matter have considerable energies. Why would two particles that have suddenly come into existence have more than ground energies?

 

There is also the magnetic field of the black hole. I think Hawking radiation would require a quiet place whereas anywhere near a black hole, even one that is not digesting material is anything but quiet. It has been found that the magnetic fields around the SMBH at the centre of our galaxy can give particles energies of a hundred trillion electron volts. That is not a casual; one falls in, one escapes scenario.

 

The SMBH at the centre of our galaxy is relatively small, at 3.6 million solar masses.

 

We can stop all molecular motion at 0.K but atomic motion continues (as in atoms don't literally fall apart) suggesting that there are possible temperatures below that.

[sigurdV]

CraigD says:

 

 

#How this results in the black hole losing mass-energy, and the universe outside it gaining exactly the same amount, involves physics beyond my (but not beyond Hawking’s and other professional and serious amateur physicists’) normal ken, by which the captured particle, as it cannot interact with the universe outside the black hole, has negative mass-energy, but this is not important to the explanation of how Hawking radiation occurs, only to the hypothesis that it reduces the mass of black holes, allowing them in extraordinary circumstances to “evaporate.”#

 

Until Lee Smolin explained negative gravitation I didnt accept it,

here we have "negative mass-energy"...

It seems to be a "loan" from the quantum foam...

The BH has to pay for both particles so there is mass lost... Right or wrong?

[CraigD]

The great Stephen Hawking:

 

He even hinted at regrets in his personal life after being asked about his biggest mistake.

 

He said that thinking information was destroyed black holes was his biggest blunder - 'or at least my biggest blunder in science.'

http://www.dailymail.co.uk/news/article-2082440/Stephen-Hawking-Women-complete-mystery-says-Quantum-physicist.html

I can see how the brief (and missing a word!) paraphrasing of Hawking in this article could give one the mistaken impression that he considered his prediction of Hawking radiation to be a blunder. However, this more complete paraphrasing of this part of his recent 70th birthday interview, from a 4 Jan 2012 Guardian News article

As for his greatest mistake, Hawking said: "I used to think information was destroyed in black holes", a belief he later revised. "This was my biggest blunder, or at least my biggest blunder in science." But his work in the field led to the theoretical breakthrough, so far unconfirmed by experiment, that black holes leak information back into the universe through quantum mechanical effects.

seems to me less prone to lead one astray.

 

Rather than being what Hawking considers his biggest blunder, Hawking radiation is the mechanism he believes allowed him to find a resolution to the “black hole entropy paradox” his earlier blunder posed.

 

I think a short summary of this paradox would be helpful here. The following is only as best I understand it, and likely as deficient as my understanding of the underlying physics.

 

The second law of thermodynamics concludes that, almost certainly, the average entropy a measurement of disorder and/or information, of the universe increases with time. This should hold true for any system, including one with black holes in it. However, because in theory no information about matter-energy that has fallen into a black hole, other than 3 data, its total mass-energy, net charge, and total angular momentum, black holes appear, when one considers the universe to consist of only the domain of it that’s in principle measurable, to remove information from the universe, reducing entropy, violating the 2ndLOTd.

 

It appears (I don’t know the history of his ideas well enough to cite specific evidence of their evolution, so rely on the impression from quotes like the above) Hawking once accepted this conclusion, then later, realized that Hawking radiation, being random-like, allows information/entropy from within a black hole to reenter the universe, so he reversed his position and called his previous one “his biggest blunder in science.”

 

Can you show where I said that the balls originate inside the black hole?

 

I specifically said "One rolls down hill (so falls into the black hole)".

I was guessing, since you didn’t state specifically where the balls started relative to the BH’s event horizon. I guessed wrong. Please accept my apology.

 

Qfwfq and madddog have already given this explanation, but I’ll give it again, if for no other reason than the thought exercise. This is essentially just a restatement of the basic mechanism of Hawking radiation:

 

The virtual particles in the vacuum consist of a juxposition of all possible particles that can exist, then annihilate with their antiparticle before they can be measured, including particles with velocities requiring that a particle to escape from any location outside of a given BH, and particles with velocities that require that they are captured. If one of the particles enters the BH before it annihilates with its antiparticle, the interaction which assures their annihilation ends, and that annihilation doesn’t happen. The surviving particle is Hawking radiation.

 

In your original post, you said

You have a steep slope a thousand miles long. At the 750 mile mark, you place two balls next to each other. One rolls down hill (so falls into the black hole) and the other rolls uphill (so escapes the black hole).

This is a reasonable metaphorical description of how Hawking radiation theoretically works, but omits the key feature of virtual particles: that they have different non-zero velocities relative to one another and the BH. Your “place two balls” appears to assume that the balls must have zero relative velocity. If you modify it to remove this assumption, you now describe possible pairs of balls where one begins with a velocity uphill great enough that it can roll up the steep, thousand miles long slope.

 

It was said decades ago that you would need maybe 1600 tons of matter to create a stable black hole. So if you have masses less than this created as you say by high energy cosmic ray collisions, they vanish almost as fast as they form. There is not sufficient gravitational force to hold them together.

Do you have a source for this, Sexton? Or can you give such a solution mathematically?

 

I’ve not read of any explanation, prior to Hawking’s, for why very small black holes that then increase by capture all the mass-energy they encounter, are not formed. If you know of one, I’d be very interested to, too.

[sigurdV]

I WAS wondering why the BH had to pay the bill, but if the virtual particles start from the inside there is no one else to bill...

 

"The virtual particles in the vacuum consist of a juxposition of all possible particles that can exist, then annihilate with their antiparticle before they can be measured, including particles with velocities requiring that a particle to escape from any location outside of a given BH, and particles with velocities that require that they are captured. If one of the particles enters the BH before it annihilates with its antiparticle, the interaction which assures their annihilation ends, and that annihilation doesn’t happen. The surviving particle is Hawking radiation."

 

But since light cant escape, i suspect the origin of the particles is at the borderline.

Is it vague or razorsharp?

[maddog]

But you are not me and even if I believe something I will still question it to death. That is what science is about rather than saying "Accepted science is this, this and this. That's good enough for me." Thinking is allowed.

You're right, I wouldn't want to be you. You appear to "wear logic on your sleeve"

rather than use it from reading your posts. At the moment and from now on, I am

going to ignore your "questioning" or denying Hawking Radiation as soo awhile

ago as to not worth bothering with.

 

"time reversed version of annihilation pairs"?

Reversing time is a thought problem construct. You can view of a series of events

and then in your mind run them in reverse by reversing time. It is not difficult, just

visualize.

 

Annihilation pairs, other than matter-anti matter have considerable energies. Why would two particles that have suddenly come into existence have more than ground energies?

It was just an example. Virtual particle pairs are because of Heisenberg's

Uncertainty principle.

 

There is also the magnetic field of the black hole. ...

Irrelevant actually, unless you are considering how a particle falling into a BH is

influenced in it's path to the center.

 

...I think Hawking radiation would require a quiet place whereas anywhere near a black hole, even one that is not digesting material is anything but quiet. It has been found that the magnetic fields around the SMBH at the centre of our galaxy can give particles energies of a hundred trillion electron volts. That is not a casual; one falls in, one escapes scenario.

Never implied casualness regarding Hawking Radiation. Blazars for example

are definitely not a quiet environment. Such an object now are considered

BH that have acquired enough charge in the accretion disk to create two huge jets

flowing out the poles of a spinning BH. Obviously these highly excited charged

particles are just outside. It is there a lot of magnetic flux.

 

We can stop all molecular motion at 0.K but atomic motion continues (as in atoms don't literally fall apart) suggesting that there are possible temperatures below that.

I am not sure why you went here with this reference. At Zero Degrees Kelvin there will

still be residual energy fluctuations. It doesn't just all stop. Thinking that way is

very classical.

 

maddog

[Cyberia]

Craig D. Third time of trying. I have had my last two tries vanish without trace so Microsoft Word first this time.

 

I looked through the wiki article on Black hole entropy and some of the links are doubtful. Notably No.2, proof of Hawking radiation. Not.

 

If you have a metal block at sea level and then take it and place it on a floor one hundred feet up., energy has been used to do this and now the block has more (potential) energy. But it sits there on the floor seemingly the same as before. A little more mass in a black hole produces a little more gravity, so just a change of forms of “energy“. Nothing lost.

 

Virtual particles come and go almost instantly. The fact that they go suggests that no only do the particles not move far apart but that they may not move at all since how else could particle and anti particle annihilate each other?

 

1600 tons was from a book or science journal I read decades ago. Someone’s workings. No idea where now. Maybe he was wrong?

 

A singularity inside a black hole says that everything is crushed to a point source or nearly so. But we have no evidence fundamental particles like electrons and quarks can be crushed. If they can, we would have a neutron star where gravity, so escape velocity would be 2/3 c. More mass and this would collapse into an intermediate stage made of fundamental particles. And even more mass and we would have our black hole where even these particles have been crushed out of existence. No evidence of any intermediate stage.

[Cyberia]

Maddog. We are all different.

 

Read what I just wrote on Hawking Radiation.

 

Are you saying use imagination instead of experimentation? I can imagine elephants flying but that does not mean that science allows it.

 

Heisenberg's Obvious Principle. Blindfold someone and let them loose in a field. They keep kicking till they kick a ball that has been placed there somewhere. Now they know where the ball was and what direction it is moving in, but not where it is now. I can’t see that this has anything to do with HUP other than the very general uncertainty about particles which come and go almost instantly so are not easy to measure.

 

Magnetic fields of the sun heat particles to a million degrees where the surface is maybe 6,000.C. So we come to black holes where trillions of gauss whips streams of particles off into space at almost light speed, as in the jets from their poles. How is that irrelevant?

 

Yes, outside the event horizon because that is where everything happens.

 

At 0.K it is not “residual energy fluctuations”. Matter still exists as matter with electrons around protons and neutrons, etc. Back in 2003, MIT recorded temperatures as low as half a billionth of a degree above absolute. If temperature affected say electrons, slowing them down, then at very low temperatures, matter would begin to collapse in on itself.

 

My thinking is anything but classical.

[Cyberia]

SigurdV. The pair particle in Hawking radiation are said to be caused by (extreme) gravitational forces so I would think that they were made over a very wide area outside the event horizon, with more of them as you approach the EH.

[freeztar]

I haven't read the whole thing yet, but this paper by Adam Helfer seems to have a good overview as well as addressing some of the possible kinks in the arguments for Hawking radiation.

 

http://xxx.lanl.gov/pdf/gr-qc/0304042v1.pdf