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stutefish
2008-Sep-08, 06:56 PM
Can anybody explain to me the current ATM obsession with making Black Holes out to be these magical, mystical, metaphysical objects of wonder and stupefaction?

I mean, I get that they're stimulating to the imagination. And I get the whole thing about their gravity being greater than C, or some such.

But... How do I explain my question?

Okay.

Take a star. It's got mass, right? It's got gravity. It bends light paths in its vicinity. It probably gets pretty dense near its core--dense enough to cause fusion, anyway.

So you add mass to this star, and all its other properties stay the same, only more so, right? Light bends even more, it gets denser, etc.

You add enough mass (in a small enough volume), and light bends so much it can't escape. The acceleration due to gravity is greater than C.

So naturally, we can't see the star anymore. And I get that the mathematics of GR ends up with a singularity at that point.

But other than that, it's still (probably) a star, right? I mean, so what if it bends light a little or a lot? So what if the math breaks down? There's still a physical object in there, right? Still doing whatever really dense stars do, right? Probably getting denser, maybe maximally dense? I guess there's probably some neat physical and quantum-dynamic effects that happen at really high densities, but...

Being really dense doesn't mean it somehow becomes a zero-dimensional super-being, right? It's still there, still doing its starry thing behind its event horizon, right? Other than that event horizon, it doesn't, strictly speaking, become something else--or does it?

astromark
2008-Sep-08, 07:15 PM
Stutefish; Your understanding is as mine, but the last line 'or does it?' I would drop.

In a related thread a fellow wants to put a space craft on the spot between two BH's... He seems to have missed the point you make. All that mass that has not yet passed into or beyond the event horizon are going to be as if you were near a star. That is what a BH is. A star. There will be some who will want to argue this point. I am not listening.... I will be sitting on this fence over here.... watching.:)

JohnD
2008-Sep-08, 08:20 PM
As I understand it, the singularity is the problem. The physics that explain stars and subatomic particles, perfectly and predictably to the point of the formation of the BH, break down completely at a singularity. We cannot predict what is happening in there, seriously we cannot predict because time itself is affected and stops. Therefore causality fails and we cannot predict, not because we do not understand but because time does not exist. That does make a BH special - it is a special place in the Universe where nothing can happen.

My confusion about BHs is on the debate about information and BHs. Hawking states that "BHs have hair"! They radiate, as quantum variation creates pairs of particles and antiparticles close to the event horizon and one of the pair disappears into the BH. He calculates that negative energy particles are more likely to do so, that the other, positive energy particle appears in the Universe, as if radiated from the BH. As the disappeared one of the pair has negative energy, this represents a net loss to the BH, which will eventually evaporate.
So far so good, but whence the information? A piece of matter will be dismembered to its subatomic particles as it approaches the BH singularity. All information that made it a particular piece of matter is lost. What possible information could return by Hawking radiation?

JOhn

alainprice
2008-Sep-08, 08:24 PM
Is a neutron star a star? Sure, why not. Does it behave anything like a normal star? No.

Is a black hole a star, I personally doubt it. Could it be a star that we simply can't observe? Sure, why not.

I don't see how fusion would be possible since the BH doesn't release energy very well. The same energy released from fusion could be used for fission.

Sam5
2008-Sep-08, 09:00 PM
As I understand it, the singularity is the problem. The physics that explain stars and subatomic particles, perfectly and predictably to the point of the formation of the BH, break down completely at a singularity. We cannot predict what is happening in there, seriously we cannot predict because time itself is affected and stops. Therefore causality fails and we cannot predict, not because we do not understand but because time does not exist.

Does that mean that all atomic oscillations and vibrations completely stop inside a black hole?

JohnD
2008-Sep-08, 09:08 PM
"We cannot predict......"

A BH has only three properties; mass, spin and temperature, and the last is due to Hawking radiation, a real universe phenomenon, nothing to do with what's inside the EH.
"We cannot predict"
John

grant hutchison
2008-Sep-08, 09:19 PM
So far so good, but whence the information? A piece of matter will be dismembered to its subatomic particles as it approaches the BH singularity. All information that made it a particular piece of matter is lost. What possible information could return by Hawking radiation?Susskind writes about this in The Black Hole War (recommended!).
I think it goes like this (although you'd be much better off reading the book):

1) Entropy increases. This appears to destroy information.
2) But physical processes are in principle reversible: you can in theory recover the information that is "concealed" by entropy. You can reassemble the broken cup, reform the drop of ink that has been diluted by the bathwater, just by running the laws of physics backwards. Even quantum processes are reversible in this way, provided you haven't "collapsed the wavefunction": you just run the wavefunction backwards.
3) So information is not destroyed. It just gets hard to see, obscured by entropic processes. Entropy is hidden information, says Susskind.
4) The black hole horizon has entropy, proportional to its surface area, which increases as stuff is added to the black hole.
5) To the distant observer, under GR, stuff never crosses the horizon.
6) Eventually the hole evaporates via Hawking radiation emitted from the event horizon.
7) For the distant observer, the Hawking radiation contains the information, in a very entropic form, that went into the black hole in the first place.

This is important, because it makes black holes work like the rest of the Universe: in principle, time reversible information processors, rather than information disposal machines. It preserves the principle of reversibility, which is built into the foundations of physics. (Hence the subtitle of Susskind's book: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics.)

Or at least, that's what I think Susskind says in the book. :)

Grant Hutchison

grant hutchison
2008-Sep-08, 09:22 PM
A BH has only three properties; mass, spin and temperature ...
John[Monty Python]

Small voice: And charge.

Yes, yes, okay, and charge.
A BH has only four properties ...

[/Monty Python]
;)

Grant Hutchison

stutefish
2008-Sep-08, 09:28 PM
Thanks for all the interesting replies, everybody!

So I'm a little confused about this singularity thing: Is it a place where things like time and whatnot stop happening? Or is it just a place where the math can't describe what's happening?

And I'm also a little bit confused by the comparison to a neutron star. I mean, I understand that neutron stars don't behave much like other stars. But they do pretty much behave like dense, massive objects, right?

So what's the deal with Black Holes? They're dense, massive objects. The math has limits. But the object--the mass and density--is still there, right? I mean, that's the whole point of a Black Hole, isn't it? That the mass and density of the object are still quite thoroughly there?

grant hutchison
2008-Sep-08, 09:41 PM
So I'm a little confused about this singularity thing: Is it a place where things like time and whatnot stop happening? Or is it just a place where the math can't describe what's happening?It's a place where the maths blows up into zeroes and infinities: in this case a dimensionless point at the centre of the black hole. People who know about these things take this mathematical singularity as an indication that current theory can't handle the extreme physics in the location around the mathematical point that causes the trouble. It likely requires some sort of fusion of general relativity (for the extreme gravity) and quantum mechanics (for the small size).
Unfortunately (well, in my view anyway), some physicists also apply the name "singularity" as shorthand for the superdense, tiny little (Planck length) whatever-it'll-turn-out-to-be-that-new-physics-will-describe, right at the heart of the black hole. So the black hole singularity is both the mathematical glitch, and shorthand for some sort of small dense object that physics can't currently describe.


So what's the deal with Black Holes? They're dense, massive objects. The math has limits. But the object--the mass and density--is still there, right? I mean, that's the whole point of a Black Hole, isn't it? That the mass and density of the object are still quite thoroughly there?Well, it's an object that lacks a surface, for one thing: there's an imprint in space that's completely characterized by its mass, charge and spin. it's delimited by a horizon in space that you can cross in one direction but never come back through. And if there's anything other than a mathematical point of infinite density at the middle of the thing, it's likely to be something considerably smaller than a proton which masses more than the Sun. So it's kind of unusual.

Grant Hutchison

Digix
2008-Sep-08, 09:49 PM
from what I know there is not everything so clear, because all current modeling and calculations are based on neglecting everything that falls into black hole.
so black hole becomes just some mysterious object that sucks everything inside and gets bigger.

hawking radiation is just speculation that if some other unproven theory is correct then maybe if black hole model is correct such radiation can exist.
no experimental evidence is available.

also what about insides of black hole nothing is known and modeling is just speculative anyway.
for some possible model look here
http://casa.colorado.edu/~ajsh/schw.shtml
it is very nice model what happens when you fly into blackhole

as about singularity diameter, I suppose answer is more or less easy, because from the view of quantum mechanic singularity is usual particle or wave that has wavelength no less than h/e. if we add gravitational time dilution then size is supposed to extend significantly
of course that diameter is not usual diameter it is wavelength but result is about the same.

grant hutchison
2008-Sep-08, 10:01 PM
hawking radiation is just speculation that if some other unproven theory is correct then maybe if black hole model is correct such radiation can exist.Which "other unproven theory" do you have in mind?

Grant Hutchison

Sam5
2008-Sep-08, 10:08 PM
So does anyone here know if all atomic oscillations and vibrations completely stop inside a black hole?

Digix
2008-Sep-08, 10:14 PM
Which "other unproven theory" do you have in mind?
Grant Hutchison
theory that particles or photons can appear from vacuum.

And also I am not sure if Hawking correctly imagined horizon line, because that is not some kind of sharp razor blade that yous can orbit freely on one side but fall down instantly if you touch it, it is exponentially increasing red shift so no mater if you are a bit up or below horizon line you cant escape anyway or send any information to outside.
all photons that would somehow manage to appear (even if that another theory is correct) will just redshift so much that nothing will come out anyway.

Digix
2008-Sep-08, 10:21 PM
So does anyone here know if all atomic oscillations and vibrations completely stop inside a black hole?

nothing stops inside black hole, but if you talk about singularity then no particles except photons can exist there even if particles exist they completely overlap and form one particle with appropriate wavelength.

AndreasJ
2008-Sep-08, 10:29 PM
Can anybody explain to me the current ATM obsession with making Black Holes out to be these magical, mystical, metaphysical objects of wonder and stupefaction?
I expect most mainstream scientists working with black holes think they're objects of wonder and stupefaction. Then again, entomologists tend to feel the same way about beetles.

As has been said already, we don't know what really happens inside a black hole, but the general assumption is the mathematical singularity will disappear in some future and more accurate theory. From an outside perspective, however, black holes aren't much like stars specifically - the properties they share with stars they share with essentially any massive object.

AndreasJ
2008-Sep-08, 10:33 PM
theory that particles or photons can appear from vacuum.

And also I am not sure if Hawking correctly imagined horizon line, because that is not some kind of sharp razor blade that yous can orbit freely on one side but fall down instantly if you touch it, it is exponentially increasing red shift so no mater if you are a bit up or below horizon line you cant escape anyway or send any information to outside.
What? How does a finite redshift (which is what we're talking about from any point above the horizon) prevent escape?

JohnD
2008-Sep-08, 10:37 PM
as you say, digix, the models you link to only deal with experience outside the Event Horizon. As you, or an observer seeing you, fall in towards that EH, things get seriously relativistic. The observer sees time slow down for you - your telemetered heartbeat would slow and slow, but never stop, for to them, you would never reach the EH. You would experience either nothing at the EH, or spaghettification (! Nothing to do with the Holy Monster!) as tidal forces began to stretch you apart, depending on the size of the BH and the gradient of the gravity well. Big is better for a falling astronaut. But that only delays your awful end, as the gradient will increase as you approach the BH singularity, pulling you into smaller and smaller pieces.

And that's still what bugs me, GH. We are into analogies here, which hold water as well as the broken teacup, which may be re-assembled like a jigsaw using the information in the pieces' shapes. But what information exists on a quark, for the destruction may go as far as that, to say if it was previously part of a proton or a neutron? If you invoke reversing time in a BH singularity, then why should an astronout come out, rather than a dragon?

John
(Who whispers that he thought of charge and changed his mind)

PS. Digix, for evidence that virtual particles exist, look up the Lamb Shift. Wallis Lamb won a Nobel for that.
This may be a start: http://www.sciam.com/article.cfm?id=are-virtual-particles-rea&topicID=13 J.

grant hutchison
2008-Sep-08, 10:41 PM
Which "other unproven theory" do you have in mind?theory that particles or photons can appear from vacuum.Ah. You should perhaps Google "Casimir effect", for experimental evidence of exactly that sort of virtual pair production in vacuum.
The effect of the surrounding cloud of virtual particles also needs to be factored into the description of real particles in quantum mechanics, or the predictions are in error. So it does seem to be on a more solid footing than you suggest.


And also I am not sure if Hawking correctly imagined horizon line, because that is not some kind of sharp razor blade that yous can orbit freely on one side but fall down instantly if you touch it ...I'm reasonably confident that Hawking would have worked his way up to at least your level of understanding.

Grant Hutchison

stutefish
2008-Sep-08, 10:45 PM
Well, it's an object that lacks a surface, for one thing: there's an imprint in space that's completely characterized by its mass, charge and spin. it's delimited by a horizon in space that you can cross in one direction but never come back through. And if there's anything other than a mathematical point of infinite density at the middle of the thing, it's likely to be something considerably smaller than a proton which masses more than the Sun. So it's kind of unusual.
Thanks, Grant!

I am content. :)

grant hutchison
2008-Sep-08, 10:51 PM
But what information exists on a quark, for the destruction may go as far as that, to say if it was previously part of a proton or a neutron? If you invoke reversing time in a BH singularity, then why should an astronout come out, rather than a dragon?Because by time reversing, you reverse every single movement and interaction of the whole vast soup of particles trapped at Susskind's "stretched horizon", absolutely precisely. The quark doesn't come with a slot A to take tab B on some other quark, it comes with a worldline that runs back to the original astronaut. If you reverse its "motion" (whatever that really is, in QM) at the same instant as you reverse the motion of every other particle, they'll all blunder their way back down their worldlines to make an astronaut, constrained by physics alone.


(Who whispers that he thought of charge and changed his mind)Yeah, sorry to tease. The Monty Python analogy overwhelmed me. :)
My recollection is that the usual triad is mass, spin and charge, with the other properties, like temperature and entropy, seen as derived quantities from these three.

Grant Hutchison

Digix
2008-Sep-08, 11:10 PM
What? How does a finite redshift (which is what we're talking about from any point above the horizon) prevent escape?
in the line of horizon redshift is infinite below that line its beyond infinity.

if you still are not below horizon, mathematically you can escape but you will loose all your mass even if you have 100% efficient engine. or if you are some gamma photon emitted at 0.0001% until horizon line you will be red shifted somewhere below infra sound frequency so that is not practical escape. nobody will be able to receive that signal even if they are orbiting at 150% of horizon distance.

basically if something besides photons fall below that 150% they cant escape anymore without additional help, photons also cant escape because they are to stupid and do not care if where they fall, it is still possible to send signals they will severely redshift until you reach horizon, and then redshift will be infinite what means no communication because you cant receive infinitely low frequency.

slang
2008-Sep-08, 11:18 PM
Yeah, sorry to tease. The Monty Python analogy overwhelmed me. :)

Nobody expected it! :)

Digix
2008-Sep-08, 11:22 PM
Ah. You should perhaps Google "Casimir effect", for experimental evidence of exactly that sort of virtual pair production in vacuum.
The effect of the surrounding cloud of virtual particles also needs to be factored into the description of real particles in quantum mechanics, or the predictions are in error. So it does seem to be on a more solid footing than you suggest.
casmir effect is not so clear as you think, there are many experimental errors, basically they experimentally get much higher force that theory predicts.
so that can be something else.
also it has no obvious relation to any virtual particles.
in any case hawking radiation is not 100% proven, just look at most of LHC threads you will not find any serious physicist who is 100% confident in that theory.


I'm reasonably confident that Hawking would have worked his way up to at least your level of understanding.
that depend on black hole model he used, however I would not expect any serious stuff from inventor of time machines. since that is where all Hawking's fame came from.
he is great mathematician but mathematic is no more correct than data on which result is based.

in any case that does not matter, there is no even remote experimental evidence, and model of universe is no near to complete. even if all calculation are correct some other stuff may come out.

grant hutchison
2008-Sep-08, 11:54 PM
I'm reasonably confident that Hawking would have worked his way up to at least your level of understanding.that depend on black hole model he used, however I would not expect any serious stuff from inventor of time machines.I certainly admire your confidence, if nothing else.

Grant Hutchison

Digix
2008-Sep-08, 11:55 PM
And that's still what bugs me, GH. We are into analogies here, which hold water as well as the broken teacup, which may be re-assembled like a jigsaw using the information in the pieces' shapes. But what information exists on a quark, for the destruction may go as far as that, to say if it was previously part of a proton or a neutron? If you invoke reversing time in a BH singularity, then why should an astronout come out, rather than a dragon?
nothing will happen below horizon too, but now you are part of black hole and you also help it to keep everything inside.
as i understand if you are just above horizon you already need all your mass energy to get out below horizon you need more than you have. so you cant escape(however there is quite a lot "what if" possibilities that can help to escape) because all modeling is done in the way when you are photon that is trying to escape.

because of gravity effect your time slows down and because of that you loose even more of your energy if you are photon (but applicable to everything). so imagine that if before you fall inside you had 100km/s speed because of time dilution you only have 20km/s if you had 100L of fuel you only have 20l worth.

so nothing interesting will happen below horizon too, everything will just fall until they hit the center realyy fast becasue time goes slowly and objects fall fast. and at the center no formation can exist anymore, because everything will collapse anyway. quarks probably will just annihilate or overlap each other other particles will also overlap like photons. so you will have ultra heavy super particle

if you somehow remove gravity for short time I expect little big bang. however there is unclear if quarks annihilate when overlap or not. so that big bang may end as big gamma flash or as some supernova explosion that will end as bright shining star that formed from nothing.
time is not reversed inside of black hole and it cant be reversed anywhere unless process is completely symmetric.


John
(Who whispers that he thought of charge and changed his mind)
PS. Digix, for evidence that virtual particles exist, look up the Lamb Shift. Wallis Lamb won a Nobel for that.
This may be a start: http://www.sciam.com/article.cfm?id=are-virtual-particles-rea&topicID=13 J.
name virtual means is same as imaginary or not existing you cant prove imaginary stuff to exist by its definition, because when you prove existence imaginary becomes real.
also materialization of virtual particles creates problems with invariance, since you may hit them as you move.

grant hutchison
2008-Sep-09, 12:07 AM
name virtual means is same as imaginary or not existingNot so. It applies to particles that have real existence, but only for a period of time allowed by Heisenberg. If they didn't have real existence, they wouldn't be able to cause real things like the Lamb shift.

Grant Hutchison

alainprice
2008-Sep-09, 12:13 AM
I'm with Grant. I've seen plenty of bubble chamber tracks left by decays that show very well that a virtual particle must have existed, but it does not show up as a trail. It simply has a very well defined path(momentum) and by-products(mass-energy). Sounds like a particle to me.

For example, a miniature black hole(the kind that the LHC might produce) is not visible. It will leave an invisible track(no track, really) with particles spewing out of it in a very predictable fashion. I would take that as proof that a BH really was created, but I'll never have a poster of the BH itself on my wall because nobody will be able to see it.

Digix
2008-Sep-09, 12:31 AM
ok if you say that virtual particle can interact with real particles like in buble chamber what about reaction less drive who cares about newton laws, lets fly with helicopters in the vacuum, after all blades may be fast enough to hit few temporary particles that will be quite enough assuming that vacuum energy is infinite in that case.

even if existence is temporary it still can interact with reality then isn't it so?

in case of LCH and assuming hawkings theory is correct blackhole will not show any paths it will instantly evaporate in the about same place where it was created and bunch of random trash will be created.

that would be very good energy source if we could manage to create mini black hole which can evaporate slowly enough, just feed it with some crap and it will convert it into pure energy. just perfect for interstellar spaceship engine since you can easily fly and navigate in the vacuum using just a little hydrogen atoms that you can collect


however hawking skipped one question(or maibe i missed that): what will happen after evaporation?
assuming that no negative energy will fall into black hole nothing can annihilate singularity, so black hole does not disappear, it just generate insane amount of energy from nothing.

grant hutchison
2008-Sep-09, 01:21 AM
ok if you say that virtual particle can interact with real particles like in buble chamber what about reaction less drive who cares about newton laws, lets fly with helicopters in the vacuum, after all blades may be fast enough to hit few temporary particles that will be quite enough assuming that vacuum energy is infinite in that case.I'm not getting a reasoned argument, there. Virtual particles cannot have real effects if we can't use them to fly a helicopter?


however hawking skipped one question(or maibe i missed that): what will happen after evaporation?
assuming that no negative energy will fall into black hole nothing can annihilate singularity, so black hole does not disappear, it just generate insane amount of energy from nothing.Yeah, you missed that bit. The energy to "promote" the virtual pair comes from the black hole's tidal gravity. So the black hole's gravity field loses energy, which (since the black hole is the gravity field) is a loss of energy from the black hole, which correspondingly reduces its mass. That's why it's called "evaporation", because the hole dwindles to nothing during the process.

Grant Hutchison

Sam5
2008-Sep-09, 01:30 AM
ok if you say that virtual particle can interact with real particles like in buble chamber what about reaction less drive who cares about newton laws, lets fly with helicopters in the vacuum, after all blades may be fast enough to hit few temporary particles that will be quite enough assuming that vacuum energy is infinite in that case.

How about one like this :):

http://www.youtube.com/watch?v=9_xKfLifel4&feature=related

stutefish
2008-Sep-09, 01:34 AM
that would be very good energy source if we could manage to create mini black hole which can evaporate slowly enough, just feed it with some crap and it will convert it into pure energy. just perfect for interstellar spaceship engine since you can easily fly and navigate in the vacuum using just a little hydrogen atoms that you can collect


however hawking skipped one question(or maibe i missed that): what will happen after evaporation?
assuming that no negative energy will fall into black hole nothing can annihilate singularity, so black hole does not disappear, it just generate insane amount of energy from nothing.
You're forgetting all the energy used to create the black hole in the first place. The LHC doesn't run on sweet dreams, after all: It runs on huge amounts of electricity.

Digix
2008-Sep-09, 02:10 AM
You're forgetting all the energy used to create the black hole in the first place. The LHC doesn't run on sweet dreams, after all: It runs on huge amounts of electricity.

right, but if you manage to make black hole big enough that can be stable for long enough to accept more food you don't need any power anymore, just throw all trash you don't need inside and get photons out

also it can be that you don't need any trash at all black hole will just generate energy by itself :) like perpetual motion device.
unless you point me to the explanation how hawking is supposed to annihilate singularity and somehow to get around particle symmetry

that will be a thing worth more that whole earth :)

even if black holes evaporate in correct way with no exotic effects there is still theoretically potential way to use them as mass to photon energy converters because they can break particle symmetry i.e. they can annihilate matter without antimatter

Digix
2008-Sep-09, 02:28 AM
I'm not getting a reasoned argument, there. Virtual particles cannot have real effects if we can't use them to fly a helicopter?
of course no, if I can touch that it is useless. if helicopter blades cant touch them so how these virtual particles are going to touch black hole?


Yeah, you missed that bit. The energy to "promote" the virtual pair comes from the black hole's tidal gravity. So the black hole's gravity field loses energy, which (since the black hole is the gravity field) is a loss of energy from the black hole, which correspondingly reduces its mass. That's why it's called "evaporation", because the hole dwindles to nothing during the process. gravity field cant loose anything, it does not contain any energy, no stationary fields contain any energy.
where did you got that explanation from?
blackhole is definitely not only gravity field alone it still have center singularity that as you know concentrates all its mass and creates all that gravity. you cant, and as we know, there is no way to suck energy from remote distance just somehow consuming gravity fields.

also tidal gravity is not tidal waves as you think it is only high acceleration gradient just your head have acceleration of lets say 1g and your feet is 10000g so that will rip them away. but don't worry you will join soon inside of singularity into one quark.

grant hutchison
2008-Sep-09, 02:46 AM
unless you point me to the explanation how hawking is supposed to annihilate singularity and somehow to get around particle symmetryAny quantum gravity theory of the singularity is likely to describe a region in which "grand unification" conditions prevail: as such, we can almost expect to see particle conservation violations in there. Likewise, the temperature of an evaporating black hole will hit the same sort of exotic territory, in its last moments. So there do at least seem to be ways of accounting for any non-conservation in our particle book-keeping.


of course no, if I can touch that it is useless. if helicopter blades cant touch them so how these virtual particles are going to touch black hole?So since I am unable to fly a helicopter supported by only small furry mammals, they do not exist? I understand.


gravity field cant loose anything, it does not contain any energy, no stationary fields contain any energy.
where did you got that explanation from?Kip Thorne. His book's open next to me. The chap does seem to know what he's talking about, I'll give him that.

You don't know Occams Ghost, by any chance?

Grant Hutchison

Digix
2008-Sep-09, 03:31 AM
Any quantum gravity theory of the singularity is likely to describe a region in which "grand unification" conditions prevail: as such, we can almost expect to see particle conservation violations in there. Likewise, the temperature of an evaporating black hole will hit the same sort of exotic territory, in its last moments. So there do at least seem to be ways of accounting for any non-conservation in our particle book-keeping. I dont have any knowledge on that area so cant argue, but i wonder who has, if nobody can ever tell for sure what happens beyond horizon and that will be quite interesting math, manipulating zeros infinities + imaginary stuff

in any case these are not proven theories just speculations I cant prove neither that it is wrong or right, and nobody will untill they see evaporating blackhole or go to its center and inspect singularity with microscope :)
even you use words "expect" and "seem".
also I should not remind that quantum gravity is nowhere to complete and it is well known that relativity contradicts with quantum mechanic in that area.
all unification attempts fail as I know



So since I am unable to fly a helicopter supported by only small furry mammals, they do not exist? I understand.
what do you mean. I just say that it there is no way to touch it it does not exists. we can touch even quarks or neutrinos and we can even see photons, but we cant touch virtual particles in any way.

if virtual particles were real enough to create tracks in bubble chamber there would be little problem to violate Newtonian laws or even create perpetual motion engine.

just imagine that we have near zero temperature piece of metal or anything.
any particle that appears inside will hit surrounding atoms and increase their temperature, so it would seem that block of metal is gaining temperature by itself


Kip Thorne. His book's open next to me. The chap does seem to know what he's talking about, I'll give him that.
well if you like post question
"is blachhole composesd of gravity field?"
or "
is all black hole mass-energy held in its gravity field"
and lets see what others say but I expect that not many will support your statment.
also there are quite many theories about gravity, I found one that gravity is negative energy, and it looks reasonable if we look at calculations and logic.
if we adopt that theory black hole will stop being black hole with singularity, it will become like separate universe similar to ours. because gravity with negative energy will cancel itself


You don't know Occams Ghost, by any chance?
no, I dont. why do you ask.

grant hutchison
2008-Sep-09, 08:28 AM
what do you mean. I just say that it there is no way to touch it it does not exists. we can touch even quarks or neutrinos and we can even see photons, but we cant touch virtual particles in any way.I meant that the whole "helicopter" thing was flamboyant, but pretty much content-free.
But you're happy with quarks, neutrinos and photons, all of which we detect by their effects on other physical systems, rather than by "touching" them. By the same token, virtual particles are as real as these others, since they have detectible effects on physical systems.


well if you like post question
"is blachhole composesd of gravity field?"
It's difficult to know what else it's composed of, since our physical description is of just a gravity field, and the physical effects of the gravity field.


also there are quite many theories about gravity, I found one that gravity is negative energy, and it looks reasonable if we look at calculations and logic.
if we adopt that theory black hole will stop being black hole with singularity, it will become like separate universe similar to ours. because gravity with negative energy will cancel itselfAnd that's what Hawking radiation looks like to a distant observer: negative energy goes in, positive energy comes out. The black hole loses mass, and the energy books balance.


no, I dont. why do you ask.Just that your posting style seems similar.

Grant Hutchison

Digix
2008-Sep-09, 11:54 AM
I meant that the whole "helicopter" thing was flamboyant, but pretty much content-free.
But you're happy with quarks, neutrinos and photons, all of which we detect by their effects on other physical systems, rather than by "touching" them. By the same token, virtual particles are as real as these others, since they have detectible effects on physical systems.
you theoretically can make helicopter that flies in neutrino air. since neutrinos sometimes hit detector medium the are no less touchable than house bricks, just very small.
but virtual particles are supposed to be not so small as neutrinos and there is much more of them available, theoretically amount is infinite, so if they were real, we had problems even to walk because space density was nearly infinite

also there are invariance problems, how that particle can appear exactly same for stationary observer and another observer with some significant velocity?


It's difficult to know what else it's composed of, since our physical description is of just a gravity field, and the physical effects of the gravity field. many people prefer to view gravity as some time space curve here, but i prefer it as field like you. in any case if you analyze proprieties of gravity field you cant derive statement that it have positive energy, if you like you can derive negative energy, but that wont help in this case.


And that's what Hawking radiation looks like to a distant observer: negative energy goes in, positive energy comes out. The black hole loses mass, and the energy books balance.
in that case you are suggesting negative energy existence, that seems to be against mainstream
however positive and negative energies have same chance to fall into black hole or escape from it

in any case it is still unclear how that negative energy can cancel positive because if negative and positive energies should behave in very different way.

grant hutchison
2008-Sep-09, 12:47 PM
in that case you are suggesting negative energy existence, that seems to be against mainstream.Not really: it's just book-keeping. You can define "zero energy" wherever you like, and if you find a region with less energy than that, it has negative energy.
On the simply Newtonian level, for instance, there's a convention of setting flat space as the zero of potential energy, in which case all gravity wells have negative potential energy. If you fall from a state of zero potential energy to one of negative potential energy, then you gain positive energy in the form of kinetic energy. (That, by the way, is how you get energy out of a gravitational field: you let it do work by moving things around.)
Under GR, it seems to be conventional to mark up the Kerr metric for rotating black holes so that there is a negative energy region within the ergosphere.


in any case it is still unclear how that negative energy can cancel positive because if negative and positive energies should behave in very different wayAgain, not really: they're both measures of the same underlying concept, plotted relative to a chosen zero point. So the arithmetic of negative and positive energy is just the same as for negative and positive numbers.

Grant Hutchison

Digix
2008-Sep-09, 03:56 PM
Not really: it's just book-keeping. You can define "zero energy" wherever you like, and if you find a region with less energy than that, it has negative energy.
On the simply Newtonian level, for instance, there's a convention of setting flat space as the zero of potential energy, in which case all gravity wells have negative potential energy. If you fall from a state of zero potential energy to one of negative potential energy, then you gain positive energy in the form of kinetic energy. (That, by the way, is how you get energy out of a gravitational field: you let it do work by moving things around.)
Under GR, it seems to be conventional to mark up the Kerr metric for rotating black holes so that there is a negative energy region within the ergosphere.
that is a bit different since you re talking about independent negative energy particles


Again, not really: they're both measures of the same underlying concept, plotted relative to a chosen zero point. So the arithmetic of negative and positive energy is just the same as for negative and positive numbers.
not so fast, just use negative energy in Newtonian formulas and you will see something interesting it will behave in quite other way that it can be expected from first sight


only way to escape from black holes seems to be tunneling if we assume that singularity is made of photons of different energies they can manage to tunnel beyond horizon and then they will redshift severely and and some some part of photon will escape. No particles beside photons can escape because they are incapable to trade their mass to kinetic energy
maybe that is what supposed to be hawking radiation?

grant hutchison
2008-Sep-09, 05:03 PM
that is a bit different since you re talking about independent negative energy particlesThey're still just part of the energy budget. If you stood next to one, it would look just like any other particle.


not so fast, just use negative energy in Newtonian formulas and you will see something interesting it will behave in quite other way that it can be expected from first sightI use negative energy all the time in the context of Newtonian gravity, as I described. It works just fine. But it's certainly possible to use it inappropriately to get bizarre results: by plugging in negative masses, for instance.
That's not what is being done with the energy budget in Hawking radiation, however.

Grant Hutchison

Digix
2008-Sep-09, 05:14 PM
so e=mc is inappropriate?
maybe you should try to calculate mass of that negative energy.

grant hutchison
2008-Sep-09, 05:32 PM
so e=mc is inappropriate?
maybe you should try to calculate mass of that negative energy.That's E = mc2. And of course that's exactly what happens when the negative energy is added to the mass of the black hole: the total mass of the black hole is reduced.
But recall that the negative energy which goes into the black hole is made up of the particle's positive rest mass, and all the other energy it possesses. Negative energy doesn't necessarily imply a negative rest mass for the particle.

Grant Hutchison

Digix
2008-Sep-09, 05:52 PM
But recall that the negative energy which goes into the black hole is made up of the particle's positive rest mass, and all the other energy it possesses. Negative energy doesn't necessarily imply a negative rest mass for the particle.


that cant be correct. if we so simple math negative energy is negative mass.
it cant be in other way.

of course if you talk abioou energy difference then deltaE can be positive and engative, but we talk about absolute energies here.

if I have something that is material, if cant be negative energy but positive mass. because else e=mc will me wrong

also e=mc does not say anything about rest mass it is most universal formula in the physic applicable to everything. you can use it to calculate mass of photon which do not have rest mass to. e=mc is about total energy of particle which is applicable for your reference frame. if you use another reference energy and mass will be different

grant hutchison
2008-Sep-09, 06:05 PM
that cant be correct. if we so simple math negative energy is negative mass.
it cant be in other way.Of course it can. Rest mass energy isn't all the energy there is.


of course if you talk abioou energy difference then deltaE can be positive and engative, but we talk about absolute energies here."Absolute" relative to what standard of "zero energy"?


e=mc is about total energy of particle which is applicable for your reference frame. if you use another reference energy and mass will be differentIndeed. And if you were falling alongside one of these "negative energy" particles on its way into the black hole, you'd find it had a rest mass that was absolutely standard for its nature: zero for a photon, small and positive for an electron, larger and positive for a proton, and so on.
I've said more than once that the "negative energy" is a book-keeping convention for a distant observer.

Grant Hutchison

Digix
2008-Sep-09, 06:15 PM
Of course it can. Rest mass energy isn't all the energy there is.


there is no such thing as rest and not rest energy, it all depends on observer it is possible to convert rest energy into non rest and also it can be done in oposite way.


"Absolute" relative to what standard of "zero energy"?
zero energy is just as it is zero, so no matter exist in that place
if there is something it is non zero.


Indeed. And if you were falling alongside one of these "negative energy" particles on its way into the black hole, you'd find it had a rest mass that was absolutely standard for its nature: zero for a photon, small and positive for an electron, larger and positive for a proton, and so on.
I've said more than once that the "negative energy" is a book-keeping convention for a distant observer.
again we do not care about rest mass, since there is no principal difference between photon ant electron they behave in similar way.
there are photons that have much more mass than electron or even whole atom.

korjik
2008-Sep-09, 06:29 PM
there is no such thing as rest and not rest energy, it all depends on observer it is possible to convert rest energy into non rest and also it can be done in oposite way.


zero energy is just as it is zero, so no matter exist in that place
if there is something it is non zero.

again we do not care about rest mass, since there is no principal difference between photon ant electron they behave in similar way.
there are photons that have much more mass than electron or even whole atom.

Rest energy is defined as the energy of an object at rest. Funny how that works. It is the energy of an object outside of any field with zero kinetic energy.

Zero energy is where you define it to be zero. Any scalar can be redefined that way

Tensor
2008-Sep-09, 06:40 PM
well if you like post question
"is blachhole composesd of gravity field?"
or "
is all black hole mass-energy held in its gravity field"
and lets see what others say but I expect that not many will support your statment.

Let me jump in here and say I support Grant wholeheartedly. His explanations have been right on the mark. If you don't agree, I suggest you look it up in 'Gravitation' by Misner, Thorne, and Wheeler. Chapter 33.

Just as a side note, Grant's been right on the rest of his explanations also.

astromark
2008-Sep-09, 07:11 PM
Digex... As interesting as it is to challenge and question the mainstream opinion and to offer some ideas of proof. You have failed to convince me.
Getting personal is a mistake. Others have and are entitled to a view. You might consider that when everyone tells you you are wrong... you just might be.
I find your manor offensive and abrupt. Please consider your view?

grant hutchison
2008-Sep-09, 07:20 PM
there are photons that have much more mass than electron or even whole atom.More energy. Zero rest mass.
You're making heavy weather of this by insisting on equating mass with the total energy, whatever frame you happen to inhabit. That's useful under certain circumstances, and less useful under others.
Personally, I'm with Taylor and Wheeler (Spacetime Physics), in thinking that more insights are to be had by accepting rest mass as a useful invariant, and separating out energy and momentum as its frame-dependent components.
That would certainly help you "get" the picture of negative energy that's being described here.

Grant Hutchison

grant hutchison
2008-Sep-09, 07:22 PM
Let me jump in here and say I support Grant wholeheartedly. His explanations have been right on the mark. If you don't agree, I suggest you look it up in 'Gravitation' by Misner, Thorne, and Wheeler. Chapter 33.

Just as a side note, Grant's been right on the rest of his explanations also.Tensor, I'm most grateful for your confirmation. :)
It was beginning to be a long and lonely furrow to plough, here.

Grant Hutchison

Digix
2008-Sep-09, 07:27 PM
Digex... As interesting as it is to challenge and question the mainstream opinion and to offer some ideas of proof. You have failed to convince me.
Getting personal is a mistake. Others have and are entitled to a view. You might consider that when everyone tells you you are wrong... you just might be.
I find your manor offensive and abrupt. Please consider your view?

I have right to DOUBT mainstream theory, aI do not try to convict anyone that hawking radiation does not exist. i just say it may not exist. since that is mainstream opinion there is no 100% proof that it exists if I am wrong here please present some experimental evidence.

as for you i suppose science is some religion or something? all I see is "no", "impossible", "it cant be that way".
at least care to read what are we discussing here about.

also basically I am not much against that hawking radiation there is more discussion about its mechanism. From quantum side, there is no much problems to explain that radiation

if you have something to say about negative energy of virtual particles we are listening.

for example you it would be nice if you told us your opinion if usual particle, lets say photon or electron, can have negative energy?
my opinion is no, korjik's opinion is yes. so which one is correct according to you.

publius
2008-Sep-09, 07:28 PM
Tensor, I'm most grateful for your confirmation. :)
It was beginning to be a long and lonely furrow to plough, here.

Grant Hutchison

Dittos to Grant from me as well. He's been doing a bang up job in this and the other threads. I've had my mind on other things lately and have been too lazy/busy to help out, but Grant's doing great.

-Richard

korjik
2008-Sep-09, 08:25 PM
I have right to DOUBT mainstream theory, aI do not try to convict anyone that hawking radiation does not exist. i just say it may not exist. since that is mainstream opinion there is no 100% proof that it exists if I am wrong here please present some experimental evidence.

as for you i suppose science is some religion or something? all I see is "no", "impossible", "it cant be that way".
at least care to read what are we discussing here about.

also basically I am not much against that hawking radiation there is more discussion about its mechanism. From quantum side, there is no much problems to explain that radiation

if you have something to say about negative energy of virtual particles we are listening.

for example you it would be nice if you told us your opinion if usual particle, lets say photon or electron, can have negative energy?
my opinion is no, korjik's opinion is yes. so which one is correct according to you.

I have no opinion, I have a definition.

Digix
2008-Sep-09, 08:29 PM
I have no opinion, I have a definition.
this cant be definition because definitions are axiomatic and require no proof.

grant hutchison
2008-Sep-09, 09:02 PM
Dittos to Grant from me as well. He's been doing a bang up job in this and the other threads. I've had my mind on other things lately and have been too lazy/busy to help out, but Grant's doing great.And thanks to you for the support, too. :)

Grant Hutchison

Digix
2008-Sep-09, 10:12 PM
More energy. Zero rest mass.
You're making heavy weather of this by insisting on equating mass with the total energy, whatever frame you happen to inhabit. That's useful under certain circumstances, and less useful under others.
Personally, I'm with Taylor and Wheeler (Spacetime Physics), in thinking that more insights are to be had by accepting rest mass as a useful invariant, and separating out energy and momentum as its frame-dependent components.
That would certainly help you "get" the picture of negative energy that's being described here.

Grant Hutchison

that will only work from relativistic side, but you wont be able to connect it with quantum stuff in that way
so I prefer to keep mas relative and always think about total mas ignoring rest mass
that point of view seems to be also acceptable in mainstream.
I prefer always recalculate all time space effects into energy mass changes seems most people don't do that but it is only way to join quantum wave functions with gravity and relativistic stuff.
for example what you define as time dilution converts to wave frequency decrease, and wavelength increase

anyway i finally understood your concept of negative energy that you make virtual particle instead of real one which in reality exist in the center and instead of tunneling, hawking does math manipulations to put put it into the center instead taking real one from it because he desperately wants to follow rule "nothing gets out from blackhole".

so misunderstanding is more or lets clear now, lets say you win this discussion. :doh:

in such discussions I mostly try to test if I do relativistic to quantum conversions properly
so misunderstandings often happen when i try to force everyone to use full relativistic energy everywhere.

loglo
2008-Sep-11, 03:56 PM
Dittos to Grant from me as well. He's been doing a bang up job in this and the other threads. I've had my mind on other things lately and have been too lazy/busy to help out, but Grant's doing great.

-Richard


I agree, and he got both Monty Python and Pink Floyd references into a thread on Black Holes! Well done! :clap:

grant hutchison
2008-Sep-11, 05:27 PM
I agree, and he got both Monty Python and Pink Floyd references into a thread on Black Holes! Well done! :clap:<Bows.>
The Pink Floyd must have been entirely subliminal (and should have been "animals", not "mammals"). I downloaded "Another Brick in the Wall" and had played it a couple of times during the discussion with Digix.

I find it a little disturbing when my brain has these ideas without consulting me. :shifty:

Grant Hutchison