Can black holes merge to create larger event horizons?

[Soule]

Hi!
New here. Be gentle.

Kinda an idea that popped into my head a little while ago:

Are the tidal forces of some black holes powerful enough to separate quark groups? Google seems to be a bit iffy on the subject.

 

[Matterwave]

This is an unanswered question in physics. Quark confinement, or color confinement, is not currently completely understood. On top of that, there is no quantum theory of gravity at the moment. Add on top of that, there's no current way to experimentally test for this hypothesis. The result is, there's really no way to know at this point.

Probably some calculations can be done, but the reliability of those calculations would be suspect.

 

[Soule]

Well, if black holes do separate quark pairs... wouldn't the resulting mesons and its electons, neutrinos, and photons be the result of the gravitational energy of the black hole? Beyond that, wouldn't those particles being pulled into the black hole literally be the black hole feeding on its own gravitational energy? Doesnt that break conservation of energy?

 

[mfb]

Doesnt that break conservation of energy?

No, as the additional energy from a particle deep inside the gravity well is lower than the additional energy from the same particle far away.

The tidal forces within the diameter of hadrons are tiny for large (stellar mass) black holes, so in the region where current physics works, nothing problematic happens. Smaller black holes give larger tidal forces, but it is unclear if they exist at all.

 

[Soule]

forgive me I am somewhat of a layman.

Why is the energy lower? Are you talking about potential energy?

 

[Soule]

Cus I don't think potential energy would come into play here. New mass is created. Unless its a photon I guess XD.

 

[mfb]

forgive me I am somewhat of a layman.

Why is the energy lower? Are you talking about potential energy?

The total energy matters, and potential energy is a part of it.
As seen from far away (!), creating particles close to a black hole needs less energy. In the same way, an annihilation gives less energy - if you want to get produced photons out, for example, they get redshifted.

 

[Soule]

Isnt the red shift caused by interactions with the gravitational forces (and time dialation) of a black hole? That doesn't mean there is less energy, it just means measurement of energy over time is lower because time moves faster away from the massive body. Since frequency is a direct inverse of time, as time "speeds up", frequency slows down. No energy is removed from the system. Or is that wrong x.x

Yes. according to wikipedia this is correct. Total energy of the photon remains constant.

Oh I think I see what you are saying when it comes to less energy... huh... I have to think about it more... I still think there is a discrepancy...

Yeah. Even if the energy of particles the black hole "system" is lower for a far away observer, there is still an increase of energy caused by the black holes gravitational energy beyond potential energy. The creation of these new particles does not diminish energy from anywhere else in the system or the universe for that matter. Plus those new particles have potential energy of their own to add to the system. The black hole would still be feeding on itself. It still seems like energy is being added to the system from within the system.

Wouldnt the total mass-energy of a particle within a gravity well, correcting for th negative energy from gravity (there is probably a better way to state this), be the same as that particle far away without that negative energy? (assuming the particle did not reach the event horizon). i mean it would have to be to conserve energy...

 

[UltrafastPED]

Are the tidal forces of some black holes powerful enough to separate quark groups?

The strength of tidal forces depends upon your distance from the effective center of the mass; so for a very large black hole they would be relatively weak at the surface. The smaller the black hole, the greater the tidal forces near the surface.

Practically speaking, tidal forces appear because the force of gravity is different at one end of the object than it is at the other ... so for very small objects (like a person) you would need to be in a very situation where the force of gravity is very different at your head than at your feet - different enough that you would actually feel the difference as a stretching force.

As you look for these effects in smaller and smaller objects it becomes clear that the gravitational force must be changing more and more rapidly with distance. Classically this is 1/r^2 for the force, though a calculation shows that the tidal forces change as 1/r^3.

See http://en.wikipedia.org/wiki/Tidal_force
and http://spacemath.gsfc.nasa.gov/weekly/4Page33.pdf

At atomic scales the distances are on the scale of 10^-10 meters; the nucleus is 10^-15 meters. So given the strength of the nuclear forces it requires an immense "gravitational field gradient" to pull apart the nuclei.

Of course, this actually happens, and results in neutron stars - if an object is compressed all the way, but does not become a black hole, then it will become a neutron star.

See http://imagine.gsfc.nasa.gov/docs/science/know_l1/pulsars.html

The science fiction author Larry Niven wrote an excellent story called "Neutron Star". He helps you visualize what is going on in detail, in a very entertaining way.

 

[mfb]

The creation of these new particles does not diminish energy from anywhere else in the system or the universe for that matter.

It does, as two particles separated by some distance have a lower potential as the particles closer together (this is exactly the effect of tidal forces). This difference has to be significant (order of GeV/fm) to notice tidal effects in hadrons - if it is small (and therefore not relevant), nothing happens. Separating the quarks by a fm would give ~1 GeV of available energy.

To get those tidal forces, you would have to be extremely close to a microscopic black hole. And then you'll probably want a theory of quantum gravity.

 

[Soule]

i don't understand (repeating pattern eh?)

yes but wouldn't the total system of particles have the same potential? The differences in potential energy between the two particles directly reflected by the strong force field forming between the two (three) quarks? The energy of course being generated by the gravitational tidal forces which does not grow weaker as more energy is exerted? Thats the whole problem.

 

[Soule]

hmmmm

 

[mfb]

I don't understand your question :(.

 

[Soule]

potential energy is a direct result of gravitational energy. Even if the energy to form the new particle came from the potential energy of the particle closer to the singularity, that potential energy comes from a gravitational field which does not deminish as these new particles form, thus violating conservation, yeah?.

 

[Soule]

It is new mass created from gravitational energy. Things get even weirder if the black hole engulfs the new particle. The black hole's mass would be increasing from its own gravitational energy instead of canceling out like it would under conservation...

 

[mfb]

that potential energy comes from a gravitational field which does not deminish as these new particles form

The gravitational field does not change (significantly), but the particle positions inside change, that is enough.

It is new mass created from gravitational energy. Things get even weirder if the black hole engulfs the new particle. The black hole's mass would be increasing from its own gravitational energy...

No, its mass is always linked to its gravity.

 

[Soule]

The gravitational field does not change (significantly), but the particle positions inside change, that is enough.

but the new particle would have an equal (or greater) potential energy to the energy that was taken to create it. Plus the energy of the particle itself.

No, its mass is always linked to its gravity.

i don't understand what you mean. Of course its linked to its gravity, but its gravity (and mass) would increase when it engulfs this new mass created from its own gravity instead of canceling out the energy used to create it like it should under conservation of energy.

 

[Salvador]

interesting question I too would love to hear the answer , my take would be that the energy to form these new particles comes from the pressure and gravity of the Black hole which comes from the mass it gains. If I understand Soule correctly.

 

[Soule]

Oh uh no. When a quark is separated from its particle, two new particles are formed from the energy used to separate them. When it comes to a proton, when one of its quarks are removed, a new quark forms in the proton and a meson as well, leaving you with the original particle an the meson. Thats just how it works according to the internet rofl.

Did i misunderstand what you are asking? Cus i do that... a lot... rofl

 

[mfb]

but the new particle would have an equal (or greater) potential energy to the energy that was taken to create it. Plus the energy of the particle itself.

Potential energy is negative.

I made a mistake earlier - for the calculation I used two quarks 1fm apart and the tidal forces at a fixed distance from the black hole. That does not work, however - to get tidal forces strong enough, the whole hadron would have to be significantly closer than 1fm to the black hole. That does not work with the above assumption.

The graviational potential for quarks does not exceed their rest energy outside the black hole. For light quarks (!) any differences in this are not enough to form new particles. For heavy quarks, this could be different. But even then, it happens only at black holes with a size of at most the diameter of hadrons, and then I really think we need quantum gravity to tell what would happen.

 

[Soule]

Wow you're right it would be negative. Interesting.

So this may be a legitimate problem?

Of course under very specific circumstances...

Also, i don't know the math :(. I'm going to have to take you on your word when it comes to that.

 

[PeterDonis]

So given the strength of the nuclear forces it requires an immense "gravitational field gradient" to pull apart the nuclei.

Of course, this actually happens, and results in neutron stars

I agree with the rest of your post, but I don't think this statement about neutron stars is correct. Neutron stars don't form because of tidal forces tearing apart nuclei; they form because under sufficient pressure, inverse beta decay occurs and the protons in nuclei combine with electrons to form neutrons. This happens because the protons and electrons are pushed closer together by pressure; tidal forces tearing apart the nuclei would pull the protons and electrons further apart, making them less likely to form neutrons.

 

[PeterDonis]

Total energy of the photon remains constant.

"Energy" is frame-dependent. When we say a photon redshifts, or "loses energy", as it climbs out of a gravity well (whether the gravity well is due to a black hole or any other gravitating body--the redshift has been measured here on Earth, check out the Pound-Rebka experiment), what we mean is that the photon's energy as measured by static observers--observers who are at rest at a constant altitude relative to the gravitating body--decreases.

However, any object that is in free-fall motion in a static gravitational field, such as a photon, has a constant of the motion which is called "energy at infinity". I suspect this is what the Wikipedia article was referring to. This does indeed remain constant as the photon moves, but it's not the same as the energy that would actually be measured by an observer at a finite altitude.

 

[Dale]

Well, if black holes do separate quark pairs... wouldn't the resulting mesons and its electons, neutrinos, and photons be the result of the gravitational energy of the black hole? Beyond that, wouldn't those particles being pulled into the black hole literally be the black hole feeding on its own gravitational energy? Doesnt that break conservation of energy?

You have to be very careful how you ask these questions, because:
1) In general relativity the questions about energy greatly depend on what method you are using to measure the energy and where you are measuring it
2) There is no quantum theory of gravity, although I think that your question can be answered using QFT on a static background spacetime

I don't know enough about quarks, but if you consider, e.g. a diatomic molecule like oxygen, then tidal forces can certainly be strong enough to pull apart the molecule. The resulting separated atoms are in a higher energy state due to being separated (i.e. energy can be obtained by recombining them), but the overall energy is conserved because in order for the tidal forces to pull the molecule apart one of the atoms must descend and reduce its gravitational potential.

If the molecule were allowed to re-form then you could release photons from the process as well as increase the KE of the molecule. These photons would have a total energy less than the lost gravitational potential energy, such that the Komar mass of the whole system (black hole, oxygen molecules, photons) would be conserved.

 

[Soule]

"Energy" is frame-dependent. When we say a photon redshifts, or "loses energy", as it climbs out of a gravity well (whether the gravity well is due to a black hole or any other gravitating body--the redshift has been measured here on Earth, check out the Pound-Rebka experiment), what we mean is that the photon's energy as measured by static observers--observers who are at rest at a constant altitude relative to the gravitating body--decreases.

However, any object that is in free-fall motion in a static gravitational field, such as a photon, has a constant of the motion which is called "energy at infinity". I suspect this is what the Wikipedia article was referring to. This does indeed remain constant as the photon moves, but it's not the same as the energy that would actually be measured by an observer at a finite altitude.

Yes I understand. What i meant is the environment changes. Not the energy of the photon.

 

[Soule]

You have to be very careful how you ask these questions, because:
1) In general relativity the questions about energy greatly depend on what method you are using to measure the energy and where you are measuring it
2) There is no quantum theory of gravity, although I think that your question can be answered using QFT on a static background spacetime

I don't know enough about quarks, but if you consider, e.g. a diatomic molecule like oxygen, then tidal forces can certainly be strong enough to pull apart the molecule. The resulting separated atoms are in a higher energy state due to being separated (i.e. energy can be obtained by recombining them), but the overall energy is conserved because in order for the tidal forces to pull the molecule apart one of the atoms must descend and reduce its gravitational potential.

If the molecule were allowed to re-form then you could release photons from the process as well as increase the KE of the molecule. These photons would have a total energy less than the lost gravitational potential energy, such that the Komar mass of the whole system (black hole, oxygen molecules, photons) would be conserved.

I dint think this analogy works because a new particle forms with its own potential energy leaving the original hadron (am i using that right?) With it's original energy. Forgive me. I'll have to rethink this when i have slept. I have a night schedule and it's past bedtime and i can hardly think.

 

[PeterDonis]

What i meant is the environment changes. Not the energy of the photon.

But that's only true if "energy" means specifically "energy at infinity". It's not true if "energy" means "energy as actually measured by observers at finite altitude".

 

[Soule]

But that's only true if "energy" means specifically "energy at infinity". It's not true if "energy" means "energy as actually measured by observers at finite altitude".

Oh yes. Then I guess that is exactly what I mean. I was thinking that it was like comparing the energy of an object in a high energy environment to the energy of an object in a low energy environment. It would appear lower in the high energy environment, but in truth its energy is the same in both environments.

 

[Nugatory]

I dint think this analogy works because a new particle forms with its own potential energy leaving the original hadron (am i using that right?) With it's original energy.

It works. You start with a hadron and you end up with a hadron and a meson and some kinetic energy. In the simplest case (which is easiest to visualize) the hadron ends up further down in the gravity well so some of its gravitational potential energy has been released - and that's just enough enough to account for the mass of the meson, its gravitational potential energy, and any increase in kinetic energy.

You might want to spend some time working through the classical physics of potential energy and force before adding in the complications of general relativity and quantum particles - you really need to start with a solid foundation before you can take on the advanced stuff.

 

[stevendaryl]

The tidal forces within the diameter of hadrons are tiny for large (stellar mass) black holes, so in the region where current physics works, nothing problematic happens. Smaller black holes give larger tidal forces, but it is unclear if they exist at all.

I'm not sure if I understand that. Inside the event horizon, tidal forces grow without bound for any black hole, don't they? So are you talking about the tidal forces for something hovering outside the event horizon?