black hole and hawking radiation

[spacehugo]

when mass reaches critical point, about 4 solar masses, it can become a black hole, according to steven hawking, (hawking radiation) a black hole will (if not been feed) evaporate given the time needed ( 1 with 60 zeros behind is the number of years needed for a small or medium black hole). but what will happen when a black hole have lost so much mass that it will no longer have the mass beyond critical point, will it explode back into our "reality"?

 

[origin]

when mass reaches critical point, about 4 solar masses, it can become a black hole, according to steven hawking, (hawking radiation) a black hole will (if not been feed) evaporate given the time needed ( 1 with 60 zeros behind is the number of years needed for a small or medium black hole). but what will happen when a black hole have lost so much mass that it will no longer have the mass beyond critical point, will it explode back into our "reality"?

No not according to the theory. The high mass is needed to form the black hole, but once formed it will continue to exisist even if it has very low mass. The thing is the smaller the black hole the faster it evaportes and the hotter it gets. So a very small black hole will radiate Hawkins radiation to such an extent that it will be thousands of Kelvins.

 

[Boilermaker]

Where are you getting your information? I don't know much but I know people were talking just a few months ago about the Potential for creating mini black holes with the Large Hadron Collider when it is turned on. I remember this talk was all over the Internet, some people were worried that the mini black holes created in the Collider would swallow the Earth and this would be the end of the World, there are clips on youtube where people made animations, very good ones too, which displayed the Earth disappearing into the Black Hole created by the Collider.

I doubt very much that the Black Holes it may be possible to create in the Large Hadron Collider have anywhere near the Mass of four Suns. So, where do you get that sort of information?

then the other guy says that the Hawking radiation brings the smaller black holes to a high temperature?

Hawking radiation is what? a pair of "virtual particles" are created at the event horizon of a black hole and one is captured while one escapes which is equal to an energy loss for the Black hole which equates with radiation of energy somehow and so Hawking theorized that Black holes were actually not black but brown.

as rarely (if ever) that this might happen, how do you imagine this leading to a great heat source as if the black hole were radiating heat like a furnace?

if I eat peanuts in the shell and all shells contain at least two peanuts and that's my diet, two peanuts in one shell but then I get a shell with only one peanut in it because somehow one escaped me or fell from the shell or my mouth....do you think it would be accurate to say that I am emitting or radiating peanuts just because half of one pair escaped my mouth?

if I am on a diet of +1's and nothing but +1's but somehow I accidentally swallow a -1 does that mean I have to emit a +1? It might mean I have just added a -1 to a +1 and now contain a 0 which is less than the +1 I previously swallowed but more than the -1 I just swallowed but it does not equate with an emission of +1 or radiation of +1. Just because I missed one of a pair of peanuts I was trying to swallow doesn't mean I lost one I already had swallowed, does it?

so, where are you guys getting your information?

 

[derekmcd]

Boilermaker,

Your first question concerning the LHC and mini-black holes has to do with the amount of matter contained within a specific volume. If the density within said volume is sufficient, a black hole could form. At the LHC, two particles are collided. If the two particles are accelerated to sufficient enough speeds, they gain mass in accordance with Special Relativity. If those two particles have enough energy and are 'squeezed' into a sufficiently small volume...

As for Hawking radiation, the simplest explanation is that two virtual particles (one positive and one negative) appear out of the vacuum of empty space in accordance with the Heisenberg uncertainty principle. This is a temporary violation of the first law of thermodynamics... the conservation of energy. It is usually resolved by the two particles immediately annihilating each other.

When this happens very near the event horizon of a black hole, one particle may gain sufficient energy that they become separated and do not annihilate each other. At this point, they are no longer 'virtual'... they become real particles. Now we have energy that is essentially 'borrowed' and must be returned. This is done by one particle falling into the black hole and the other being ejected. In order to conserve energy, the particle falling in has a negative energy and the ejected particle has positive energy.

In this sense, the black hole loses mass to compensate for the now, real particle that was ejected. This returns the energy of the system to its original state.

 

[Saiph]

Moving this to SS&A forum where it'll probably get more of the appropriately interested audience.

Mini-black holes are different than the kind spacehugo mentions. He's refering to naturally occuring BH's from stellar cores, not really small ones formed form particle collisions. As for those destroying the earth...eh, not gonna happen.

Those BH's have almost no cross section, they have a very small charge, and no real gravity to speak of beyond their event horizon. And with a very small cross section, it's very hard for them to 'run into' anything in order to absorb it. They'll be traveling at high speeds, relativisticly, and will leave the area of earth in fractions of a second. So the time period they have in which to hit anything is also small.

If they do hit something..they'll absorb a single proton, neutron or electron...which isn't a big deal compared to their initial characterstics...

If hawking radiation exists, they'll also only exist for a microsecond before they burn off in an energetic, but relatively small reaction.

 

[dragon04]

when mass reaches critical point, about 4 solar masses, it can become a black hole, according to steven hawking, (hawking radiation) a black hole will (if not been feed) evaporate given the time needed ( 1 with 60 zeros behind is the number of years needed for a small or medium black hole). but what will happen when a black hole have lost so much mass that it will no longer have the mass beyond critical point, will it explode back into our "reality"?

I asked a similar question here once, and the explanation I got was that once "inside" the singularity, matter becomes disassociated. IOW, it gets broken down into its most fundamental subatomic components. As the BH "evaporates" and Hawking Radiation is released, the BH does lose mass, but can never "wink back in" to the visible Universe because the matter in the Singularity always remains disassociated as a property of any Black Hole.

 

[Boilermaker]

thanks derekmcd, but about this that you wrote to me;

As for Hawking radiation, the simplest explanation is that two virtual particles (one positive and one negative) appear out of the vacuum of empty space in accordance with the Heisenberg uncertainty principle. This is a temporary violation of the first law of thermodynamics... the conservation of energy. It is usually resolved by the two particles immediately annihilating each other.

how on Earth does the Uncertainty principle agree with the creation of virtual particles or even relate to them at all?

and its common knowledge how black holes are supposed to be created, something has to be surpassed or exceded in a way and
It's called the "swartzchild radius",

in the collider in order for energy to attain mass and form a Black hole it has to....pick up a Higg's Boson somewhere and they are hoping and maybe even expecting to find the elusive Higgs when they get the results of the high energy collisions they cause in the Large Hadron Collider. Matter doesn't just appear according to Einsteins theory either, Energy equals mass times the speed of light squared but that's not saying you automatically get matter from high energies...........there is a missing ingredient, E=mc2 gives you the energy in a mass or piece of matter but the change from energy into matter requires the Higgs which we haven't found yet, right, or wrong? wrong? oh crap!

and.....how do you figure any of that requires the violation of thermodynamics? The whole total of all matter in the Universe would have been created in this manner if there was a Big Bang, so what's the violation if a single pair of atomic particles is created? I imagine charge is spin, what do you think of that? If you look at the components of the proton and neutron, two up and one down, two down and one up.....they'd fit together and bond nicely if it's spin.


also, virtual particles appear outside the event horizon and are not created from the Energy of the B.H. if one get's captured and the other doesn't, I don't see how that can be equivalent to radiating energy.

don't you think that virtual particles are the result of E=mc2, I do, which means to me that they don't appear out of "nothing" but as the result of an energetic event which causes their creation. Since they apparently appear under special conditions such as around the event horizon of a black hole or perhaps in a collider, then I believe we are missing something obvious about space/time and energy/mass and so B.H.'s

don't you?

from what I read, space could be filled with mini black holes or it might contain no such things as black holes at all. if it is filled with mini black holes they obviously don't contain the mass of four suns either and if it is filled with them they also just as obviously can't be "special" either.

 

[Saiph]

The uncertainty principle applies to virtual particles, in such that it outlines the period of time in which such particles are allowed to exist, before they must depart through mutual annihilation again.

Matter doesn't just appear according to Einsteins theory either, Energy equals mass times the speed of light squared but that's not saying you automatically get matter from high energies...........there is a missing ingredient, E=mc2 gives you the energy in a mass or piece of matter but the change from energy into matter requires the Higgs which we haven't found yet, right, or wrong? wrong? oh crap!

It's true that matter doesn't just appear, you have to have the energy concentrated into a small area first, quite a lot of it too. This energy has to be produced somewhere and transfered, focused into the spot in question. With the Hadron collider, the energy comes from the powerplant that feeds the collider, which then accelerates particles up to really high speeds. To get the concentration of energy they want, in a single spot, they accelerate other particles in the opposite direction, then let them hit. This quadrouples the energy of the impact as the objects are on opposite vectors upon collision, and focuses in one spot, where they hit. The formation of sub-atomic particles or mini-bh's from the collision have nothing to do with needing to pick up a higgs boson. The higgs is somethign I'm not to fond of, and IIRC what a professor of mine said, Higgs himself isn't to fond of the idea either. It's worth looking for, but it just doesn't sit right with a lot of physicists.

As for why virtual particles violate thermodynamics, its the spontaneous generation of energy from a uniform background. It's like having a pot of water, then one spot just happens to be boiling for a split second. There is no violation if the duration of the event is small enough to fall under the uncertainty limit for that energetic of a particle however. I.e. it doesn't exist long enough to be observed.

Now, they are virtual particles precisely because they appear out of nothing, out of the 'vacuum energy' of any system as dictated by quantum mechanics. They appear everywehre, all the time, and disappear just as fast. It's only at the event horizon of a BH, where there is a sharp barrier where one can escape, and the other cannot, due to the discontinuity in space-time that you have these virtual particles stick around at all.

One way to look at hawking radiation is not that the captured particle is a negative mass (certainly not anti-matter), but that the mass/energy gained by the BH from swallowing half of the pair is less than the energy required to break the bonds between the virtual particle pair. I.e. it's a net loss for the BH.

 

[Boilermaker]

it seems strange to me that you should say that about the Higgs because that was the most common point that I heard them speaking of when they spoke about the LHC and how the search for the Higgs had till now been disappointing. There were many news stories last Summer talking about Colliders in General and how they had hoped with past, smaller ones, that they would have found the Higgs but they didn't and now they have their hopes raised again with the LHC.

there is an equivalence between mass and gravity and velocity, I know that, it's very simple.

so, if Space = the much maligned ether and in reality does not exist, then where is the energy which converts to virtual particles with or without a Higgs present, come from, where is it stored in the vacuum?

it can't just be that little points of energy pop in from Heaven and appear as virtual particles and disappear, your not content to swallow something like that are you? That Energy which converts can only be related to the Uncertainty principle once it exists as a particle and not before............because, there is no before, it's a virtual particle, appearing from nowhere with no energy source we can point to.........maybe it's a miracle particle, that's what it should be called.....


we can't know both the velocity and position of a particle, that's the uncertainty principle, right? But virtual particles appear from nowhere and disappear again.......the act of observing them changes their position or velocity....how does this relate to virtual particles appearing in the first place? We are uncertain where these things come from, we are not questioning their position or velocity, so our uncertainty about virtual particles is real, but its their source we are pondering, not their positions or velocities, those will be our next questions about them, but right now it's what? Zero Point Energy?

help me out here.

 

[Boilermaker]

http://www.youtube.com/watch?v=_fJ6PMfnz2E


maybe this will be interesting to everyone here, the LHC scientists are explaining their mission and their methods and their interests.

this is a link to one of three video's.

 

[Saiph]

The particles come from fluctuations in the vacuum energy. Basically you have an empty, near energy-less spot that you can observe. Problem is the heisenburg uncertainty principle bites us in the butt again. The uncertainty principle does no restrict itself to a trade off in momentum & position. It also applies to a tradeoff between energy and time. By saying and observing that there is absolutely no energy in a specific area, the time during which that is true is very small...IIRC.

Basically what happens is that there is no energy, on a large scale, but on a small scale it shifts around randomly an occassionally peaks in on spot, and a "negative!" energy in areas around it. Then the fluctuation flattens out again, and everything is peachy keen yet again.

 

[MeteorWayne]

Just to add, this has been verified by experiment. Look up the Casimir Effect.

 

[Saiph]

Hmmm, I've never been fond of the Casimir effect, though it is corroboration of the vacuum energy idea, it isn't necessarily solid proof. For instance, the observed effects could be something else (weak force perhaps?). Again, my quantum class discussed this briefly and the prof (very good quantum experimentalist in nano-tech) said it wasn't as solid as it's generally presented to be.