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tommac
2010-Jan-25, 09:26 PM
Could we theoretically configure a setup of high energy lasers that all point to a certain point where the energy in that point would be a black hole?

I was thinking about an a laser beem itself being a black hole but then I thought that in order to do that the fuel itself would have to be a black hole itself to produce that laser ...

01101001
2010-Jan-25, 09:37 PM
Wikipedia: National Ignition Facility (http://en.wikipedia.org/wiki/National_Ignition_Facility)


The National Ignition Facility, or NIF, is a laser-based inertial confinement fusion (ICF) research device located at the Lawrence Livermore National Laboratory in Livermore, California. NIF uses powerful lasers to heat and compress a small amount of hydrogen fuel to the point where nuclear fusion reactions take place.

Just scale it up a few dozen orders of magnitude...

grant hutchison
2010-Jan-25, 09:58 PM
The technical term for such a black hole is a kugelblitz, which may be a useful search term.
(The word translates literally as "ball lightning"; maybe a German speaker can tell us if it is also used in that sense.)

Grant Hutchison

slang
2010-Jan-26, 12:39 AM
(The word translates literally as "ball lightning"; maybe a German speaker can tell us if it is also used in that sense.)

I'm not German but we're neighbors.. [Insert usual caveats about Wiki]:

http://de.wikipedia.org/wiki/Kugelblitz

forrest noble
2010-Jan-26, 12:56 AM
Tommac,


Could we theoretically configure a setup of high energy lasers that all point to a certain point where the energy in that point would be a black hole?

I was thinking about an a laser beam itself being a black hole but then I thought that in order to do that the fuel itself would have to be a black hole itself to produce that laser ...

There are a number of theoretical/ hypothetical ideas on this. Some think it's theoretically possible. If it were possible I think one idea would be similar to the above. Focus a number of high frequency LASERS on a single point of matter of some kind.

I think there is a better chance with high speed particle collisions but that too I think is very unlikely.

If an experiment was ever able to produce a black hole in some way it would only have the gravitational potential of the matter that it was created from (probably no more than a few atoms) which couldn't gravitationally attract anything more than it did before it became a black hole. It, however, would be very dense if it had dimensions to it at all, and might sink through the floor unless it was contained by energy to control its gravitational descent downward. Matter alone probably could not contain it. At a very small size it also might be unstable and exist for only a minuscule amount of time (billionth(s) of a second).

The general idea of it, I believe, is improbable speculation -- but still fun for some.

korjik
2010-Jan-26, 01:15 AM
Yeah, you could, but it is pretty hard. The power levels you are talking about are on the order of 'blow a hole through the moon'.

Generally, by that time, it is more efficient to just extort the world's governments than it is to do physics.

:D

publius
2010-Jan-26, 02:27 AM
There is a solution to the EFE, known as the Vaideya(sp?) Null Dust solution which is essentially a spherical collapse of a "shell of EM radiation" to a Schwarzschild black hole. The initial conditions to set it up are highy unlikely to say the least, but this is a valid solution to the EFE.

What's interesting about this is to imagine you're inside at the center of the collapsing shell. Since the shell is coming at you at light speed, the information that you're about to be trapped in a black hole could not get to you before it's too late.

So, one would be floating around in what appeared to be flat Minkowski space-time until BOOM! one was consumed into a singularity. There would be no warning. At some point in your own proper time, you are doomed. There is no escape. Yet you wouldn't know anything was wrong until a bit later in your own proper time until the singularity consumed you.

-Richard

Swift
2010-Jan-26, 02:36 AM
Yeah, you could, but it is pretty hard. The power levels you are talking about are on the order of 'blow a hole through the moon'.

Generally, by that time, it is more efficient to just extort the world's governments than it is to do physics.

:D
So you're saying that this (http://www.stardestroyer.net/Empire/Tech/Beam/DeathStar3.jpg) is just a little physics experiment? ;)

publius
2010-Jan-26, 02:42 AM
The spelling is "Vaidya", turns out.

Interestingly, in turns out that local naked singularities crop up in some of these Vaidya collapse solutions. Don't ask me to elaborate, it's well beyond me.

There is another crazy one, I forget what's it called formally, but it's a gravitational "wave of death" solution. It's a propagating curvature singularity that rolls through the whole space-time. That would make a good plot for some sci-fi movie, I think.

-Richard

korjik
2010-Jan-26, 05:44 AM
So you're saying that this (http://www.stardestroyer.net/Empire/Tech/Beam/DeathStar3.jpg) is just a little physics experiment? ;)

I think they already got Swift!

p.s. link didnt work for me.

WaxRubiks
2010-Jan-26, 06:52 AM
well if all black holes are really incipient black holes, then an event horizon wouldn't really exist, so I think that if lasers, of enough power to make an incipient black hole, were pointed at a position in space, then you would get a huge warping of space, and then the EM radiation would just disperse again, quite quickly.

tommac
2010-Jan-26, 04:24 PM
well if all black holes are really incipient black holes, then an event horizon wouldn't really exist, so I think that if lasers, of enough power to make an incipient black hole, were pointed at a position in space, then you would get a huge warping of space, and then the EM radiation would just disperse again, quite quickly.

However once the BH was created ... it wouldnt need the lasers to continue to be turned on as the BH would exist with whatever equivalent mass was used to create it. Keeping the lasers on would only serve to make the black hole more massive.

WaxRubiks
2010-Jan-26, 04:36 PM
However once the BH was created ... it wouldnt need the lasers to continue to be turned on as the BH would exist with whatever equivalent mass was used to create it. Keeping the lasers on would only serve to make the black hole more massive.

personally, I think the light would stay outside the apparent event horizon, and the light wouldn't be slowed down, so the incipient black hole would appear and disappear pretty quickly.

tommac
2010-Jan-26, 04:51 PM
personally, I think the light would stay outside the apparent event horizon, and the light wouldn't be slowed down, so the incipient black hole would appear and disappear pretty quickly.

Please explain why you would think this. Why wouldnt the black hole just absorb the energy from all of the lasers.

WaxRubiks
2010-Jan-26, 05:37 PM
Please explain why you would think this. Why wouldnt the black hole just absorb the energy from all of the lasers.

well, if the BAUT server will letme explain, :)

I think that the event horizon is an illusion product of gravitational magnification...light won't end up trapped in it, but fly through the illusion and out the other side. Maybe a bit ATM..

Anyway it would take a lot of energy to make a big one and a small one would evaporate really quickly via HR, so it would be difficult to tell..

Swift
2010-Jan-26, 05:54 PM
Maybe a bit ATM.

More than a bit. Don't post ATM answers in Q&A.

forrest noble
2010-Jan-30, 05:00 AM
Tommac,


................Why wouldn't the black hole just absorb the energy from all of the lasers.

I think mass containment and mass-equivalence containment (retaining LASER energy) is a function of the size of the black hole. The mass equivalence of a number of LASERS focused on a single point would be countless times greater than the mass of any minuscule black hole that hypothetically might be created from a few atoms of compressed matter so that the amount of LASER energy retained by such a minuscule black hole might not be either measurable or retainable on such a small scale.

A somewhat different hypothetical idea that accordingly might permit more LASER absorption can be seen here: http://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)

DrRocket
2010-Jan-30, 05:42 AM
There is a solution to the EFE, known as the Vaideya(sp?) Null Dust solution which is essentially a spherical collapse of a "shell of EM radiation" to a Schwarzschild black hole. The initial conditions to set it up are highy unlikely to say the least, but this is a valid solution to the EFE.

What's interesting about this is to imagine you're inside at the center of the collapsing shell. Since the shell is coming at you at light speed, the information that you're about to be trapped in a black hole could not get to you before it's too late.

So, one would be floating around in what appeared to be flat Minkowski space-time until BOOM! one was consumed into a singularity. There would be no warning. At some point in your own proper time, you are doomed. There is no escape. Yet you wouldn't know anything was wrong until a bit later in your own proper time until the singularity consumed you.

-Richard

That is pretty neat.

So, since "they" are doing it to "us", how do we set up the proper conditions around the capitol building when congress is in session ?

Is it possiblle to make a black hole out of what already appears to be a black hole ?

publius
2010-Jan-30, 05:51 PM
That is pretty neat.

So, since "they" are doing it to "us", how do we set up the proper conditions around the capitol building when congress is in session ?

Is it possiblle to make a black hole out of what already appears to be a black hole ?


This is what it will look like. At some point, they'll raise the debt limit past its Schwarzschild radius and collapse will be certain.

-Richard

tommac
2010-Feb-01, 02:44 AM
Not sure if I am reading this right ... but are you stating that a black hole has a maximum absorption rate?

Otherwise I dont get what you are stating.





Tommac,



I think mass containment and mass-equivalence containment (retaining LASER energy) is a function of the size of the black hole. The mass equivalence of a number of LASERS focused on a single point would be countless times greater than the mass of any minuscule black hole that hypothetically might be created from a few atoms of compressed matter so that the amount of LASER energy retained by such a minuscule black hole might not be either measurable or retainable on such a small scale.

A somewhat different hypothetical idea that accordingly might permit more LASER absorption can be seen here: http://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)

tommac
2010-Feb-01, 03:04 AM
Not sure if I am reading this right ... but are you stating that a black hole has a maximum absorption rate?

Otherwise I dont get what you are stating.

I may be able to understand if a laser's amplitude is greater than the size of the black hole then maybe the BH would not absorb all of the photons but rather cause an interference pattern ??? Does that make sense?

forrest noble
2010-Feb-02, 06:21 AM
Tommac,


Not sure if I am reading this right ... but are you stating that a black hole has a maximum absorption rate?

Otherwise I dont get what you are stating.


According to a number of theoretical/ hypothetical models of black holes they can come in all different sizes. If a black hole was just the gravitational equivalent of just a few molecules, for instance, it would have no more gravitational influence than the few molecules it was created from -- which is essentially nothing. Just because it is a black hole doesn't make it gravitationally stronger than its mass equivalence. It accordingly would just be very dense or dimensionless (depending on the model).

A tiny black hole according to most hypothetical models that I have read, could not absorb anything more than its mass equivalence would allow (which is the same for the largest black holes), which for a tiny black hole would be very little, which was my point. Whether a small black hole could exist, build up its mass equivalence, or whether it would eventually "evaporate" (Hawking radiation), depends upon the theory/ hypothesis.

The other link I posted involved lasers creating and feeding a newly created black hole which is another hypothetical model. That was this link:
http://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) -- which was closer to your OP question.

tommac
2010-Feb-02, 03:56 PM
See the question I have for this is that the black hole doesnt really need to use its gravitational influence to feed. The laser is force feeding the black hole. You shoot the laser right into the event horizon. Wouldnt that be just a merge of energy?

Also since this stream is constant there really would be no time for evaporation as you would be feeding the black hole at a rate much quicker than it could evaporate.



Tommac,



According to a number of theoretical/ hypothetical models of black holes they can come in all different sizes. If a black hole was just the gravitational equivalent of just a few molecules, for instance, it would have no more gravitational influence than the few molecules it was created from -- which is essentially nothing. Just because it is a black hole doesn't make it gravitationally stronger than its mass equivalence. It accordingly would just be very dense or dimensionless (depending on the model).

A tiny black hole according to most hypothetical models that I have read, could not absorb anything more than its mass equivalence would allow (which is the same for the largest black holes), which for a tiny black hole would be very little, which was my point. Whether a small black hole could exist, build up its mass equivalence, or whether it would eventually "evaporate" (Hawking radiation), depends upon the theory/ hypothesis.

The other link I posted involved lasers creating and feeding a newly created black hole which is another hypothetical model. That was this link:
http://en.wikipedia.org/wiki/Kugelblitz_(astrophysics) -- which was closer to your OP question.

Grey
2010-Feb-02, 04:46 PM
See the question I have for this is that the black hole doesnt really need to use its gravitational influence to feed. The laser is force feeding the black hole. You shoot the laser right into the event horizon. Wouldnt that be just a merge of energy?As long as your laser beam is narrow enough that it actually hits the black hole, yes, the energy of the laser gets absorbed, and the mass of the black hole goes up by an equivalent amount. Note that this sounds like an easy thing to do, but it's trickier than it you might think. For example, a black hole with a mass of a million tons is about 1000 times smaller than a proton. Better make sure that beam is tightly focused. :) In particular, remember that light is unlikely to interact with anything that is much smaller than its wavelength, so your laser had better be operating in the (unbelieveably) high energy gamma region of the spectrum for this to work at all.


Also since this stream is constant there really would be no time for evaporation as you would be feeding the black hole at a rate much quicker than it could evaporate.Again, in principle, there's no problem with that. As long as you're feeding in energy faster than the black hole is losing it, it will gain mass. But again, this might be harder in practice than it sounds. For our hypothetical million ton black hole, its luminosity is something like 350 terawatts. That's something like 20 times the total world power consumption. And you have to be putting that much in just to break even. And remember that the luminosity is higher for a smaller black hole, so to have gotten it up to a million tons in the first place, your lasers would have to have had an even higher power output. For example, when you're just getting started, and the black hole has a mass of about a ton, the power output is on the order of 1026 watts, which is something like the total luminosity of the Sun.

So, yes, if you can take the entire output of the Sun, and focus it down to a region a billion times smaller than a proton (and remember, for it to be localized in a region that small, it needs to have a wavelength that small, so visible light won't do; you'll need to convert it to high energy gamma radiation), and then keep that going for a while, you can build up your own black hole from scratch. Remember that until it gets up to a decent size, it's going to be putting out just about as much energy as you're putting in, so you'll want to make sure not to get too close. :)

tommac
2010-Feb-02, 08:01 PM
For example, a black hole with a mass of a million tons is about 1000 times smaller than a proton. Better make sure that beam is tightly focused. :)

As this whole example is theoretical an could probably never be tested, lets assume that we can perfectly focus the beam.

tommac
2010-Feb-02, 08:11 PM
For our hypothetical million ton black hole, its luminosity is something like 350 terawatts. That's something like 20 times the total world power consumption. And you have to be putting that much in just to break even.

But remember we are talking about multiple lasers hitting a specific spot and forming a black hole ... by definition, since we have had enough energy to create a black hole, we will have enough energy to make up for the 350 terawatts, assuming that all of that energy was focused enough.


However, I now hoave a different question. If we create a black hole with a series of lasers, and the bh is illuminating 350 terawatts, then isnt this sort of reflecting or distributing the energy that we are feeding it?

Like say we create the black hole then turn down the lasers to a state of equalibrium, where we feed in exactly the amount of energy into the black hole as it is illuminating. At that point we are really just redistributing the energy from the lasers.

Grey
2010-Feb-02, 09:28 PM
As this whole example is theoretical an could probably never be tested, lets assume that we can perfectly focus the beam.Of course. My concern here was mostly to discuss the theoretical limit. Remember that you can't localize a photon any more precisely than roughly its wavelength, so to be able to focus it that tightly, you need photons with an energy about as high as the famous "Oh my God" particle, the most energetic single particle we've ever seen. So you can't use any kind of conventional laser; you'd have to use a hypothetical gamma ray laser or something. Or, you can choose to concentrate the energy in a larger region, but then you need even more of it to give you enough mass to make a black hole.


But remember we are talking about multiple lasers hitting a specific spot and forming a black hole ... by definition, since we have had enough energy to create a black hole, we will have enough energy to make up for the 350 terawatts, assuming that all of that energy was focused enough.Sure. I just wanted to make it clear just what kind of power level we were talking about. Remember that the 350 TW is just to maintain the black hole once it reaches a million tons. To offset the Hawking radiation from a one gram black hole will be about 1038 watts, which is like the power output from a couple dozen galaxies. You don't have to maintain that power level long, because the amount of Hawking radiation drops steadily as the mass increases, but you'll have to be able to produce it for at least an instant.



However, I now hoave a different question. If we create a black hole with a series of lasers, and the bh is illuminating 350 terawatts, then isnt this sort of reflecting or distributing the energy that we are feeding it?

Like say we create the black hole then turn down the lasers to a state of equalibrium, where we feed in exactly the amount of energy into the black hole as it is illuminating. At that point we are really just redistributing the energy from the lasers.Absolutely. As long as the Hawking radiation and the energy from your lasers is roughly equal, the black hole maintains its mass, and you're pretty much converting laser energy into thermal energy. For a small black hole, that's a huge amount of energy. For a larger black hole, it would be a relatively tame amount.

tommac
2010-Feb-03, 12:38 AM
Of course. My concern here was mostly to discuss the theoretical limit. Remember that you can't localize a photon any more precisely than roughly its wavelength.

If the BH was smaller than the wavelength ( do you mean amplitude? ), then I would assume that only a percentage of the light would be absorbed, this percentage would be based on the ration of BH diameter / Amplitude ... is that a correct assumption?

Grey
2010-Feb-03, 02:33 AM
If the BH was smaller than the wavelength ( do you mean amplitude? ), then I would assume that only a percentage of the light would be absorbed, this percentage would be based on the ration of BH diameter / Amplitude ... is that a correct assumption?Sort of. And I definitely mean wavelength, not amplitude. The "amplitude" of light would be measured in the varying strength of the electromagnetic field, not any kind of distance. My point is that waves (of any kind) really will only interact with objects that are at least comparable in size to the wavelength. If the wave passes by some object that is much smaller, the wave just doesn't even really notice the smaller object. You can see that with water waves. A wave coming in to shore that has a wavelength significantly larger than a person splashing around in the water won't be significantly affected by the person. Similarly, the reason that you need to use an electron microscope to see really tiny things is that it's the only way to get something with a short enough wavelength without using x-rays or gamma rays.

Even though high energy photons seem very particle-like, that's just because none of the things high energy photons are usually interacting with are that small. Oh, sure, maybe electrons are point particles, but they often behave as though they are "spread out" due to quantum effects, because they have such a tiny mass.

So, if you want your radiation to interact with some object (like our black hole) that's really, really small, you need to make sure the wavelength of the radiation you're using is similarly small, or it just won't notice the object. I imagine that you might be right; occasionally a photon might get absorbed just by chance, and the interaction cross section probably goes something like the ratio of the size of the black hole to the wavelength. But for ordinary light, that's going to be a really astonishingly small.

Ken G
2010-Feb-05, 07:19 PM
I think I see yet another anthropic principle forming here. If tiny black holes did not evaporate by Hawking radiation, then nature might have made them, and by now they might have consumed pretty much everything (the timescale to add mass is very long when the hole is very tiny, but exponentials have an inevitable way of sneaking up on you if the holes are gravitationally bound in high density environments...). Perhaps you wouldn't get gravitationally bound end products given the energies required, so maybe there are a lot of those little guys around. Or maybe Hawking is right.

tommac
2010-Feb-05, 09:46 PM
I think I see yet another anthropic principle forming here. If tiny black holes did not evaporate by Hawking radiation, then nature might have made them, and by now they might have consumed pretty much everything (the timescale to add mass is very long when the hole is very tiny, but exponentials have an inevitable way of sneaking up on you if the holes are gravitationally bound in high density environments...). Perhaps you wouldn't get gravitationally bound end products given the energies required, so maybe there are a lot of those little guys around. Or maybe Hawking is right.

Could this be dark matter?

Ken G
2010-Feb-06, 12:03 AM
Could this be dark matter?I don't see why not. Once the everyday kinds of possibilities are ruled out (neutral hydrogen, neutrinos, etc.), dark matter is normally thought of as either being starlike massive dark objects (MACHOs, for massive compact halo objects), like brown dwarfs or garden variety black holes (ponder that phrase), which we can't see except by gravitational lensing but are otherwise not terribly exotic, or some new type of particle (WIMPs, for weakly interacting massive particles). Particle-sized black holes that did not Hawking radiate would be some kind of hybrid of both camps. It doesn't seem like dark matter is going to be baryonic, but other things make black holes too so I don't know how one could rule out that dark matter particles are black holes that are very numerous and rather tiny, except perhaps by playing out the argument of the timescale for their mass to change. That depends on whether they Hawking radiate and the density they are in, and if they are in low density gas (like intergalactic gas), I'll bet it's a really really long time to grow if they don't evaporate. Inside a neutron star it would be a lot shorter time to grow, yet we still have neutron stars, so that's another constraint also.