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Thread: Where does all that matter go?

  1. #31
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    Quote Originally Posted by Tensor
    You need energy to have gravity (remember mass-energy equivilance or E=Mcc). Normally, pairs (particles and antiparticles) of virtual particles borrow energy from space, become real particles, and almost immediately anihilate each other, returning the energy back. This is allowed by the Uncertainty Priciple of Quantum Mechanics. Near the black hole, when the particles are created, one can fall into the black hole and the other 'escapes' from the black hole. Since they can't anihilate each other as they normally would, they have to stay as real particles. But the escape of the real particle reduces the mass of the black hole (because the particle "borrowed" the energy from the black holes gravitational field).
    Wow, that's very facinating stuff. I remember reading about virtual particles a couple days ago. But the concept that the event horizon could seperate the particles and antiparticles, and in turn reduce the mass of the black hole is so neat! This really helps my understanding of black holes now. Thanks Tensor!!

    This must go against the laws of energy conservation to right?

  2. #32
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    Quote Originally Posted by dvb
    Thanks Tensor!!
    You are quite welcome.

    Quote Originally Posted by dvb
    This must go against the laws of energy conservation to right?
    No, why? The emitted radiation is balanced by the loss of mass. Mass/energy is still conserved.

  3. #33
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    Got it!

  4. #34
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    Actually, hmm. I'm still a little bit stumped. I think I may have been refering to the first law of thermodynamics. I'm not sure if energy conservation is the same thing. At least in the first law of thermodynamics, it states that energy cannot be created or destroyed. This holds up under normal circumstances with virtual particles, but since both the particle and antiparticle don't anihilate each other in this instance, the borrowed energy remains to exist and isn't given back.

    Maybe there's something else I'm not understanding here. #-o

  5. #35
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    Quote Originally Posted by dvb
    At least in the first law of thermodynamics, it states that energy cannot be created or destroyed. This holds up under normal circumstances with virtual particles, but since both the particle and antiparticle don't anihilate each other in this instance, the borrowed energy remains to exist and isn't given back.

    Maybe there's something else I'm not understanding here. #-o
    Hmmmmm, ok try this. WARNING the numbers used here are not the actual numbers. They are extremely simplified to (I hope) make it clearer.

    One particle does not fall into the BH

    Starting Energy/mass
    Particle Pair = 0
    BH mass = 10
    Total mass/energy = 10

    Create particle pair by borrowing energy/mass from BH
    Particle pair = 2
    BH mass = 8
    Total mass/energy = 10

    Particle pair anihilates, giving energy/mass back to BH
    Particle pair = 0
    BH mass = 10
    Total mass/energy = 10

    One particle falls into BH

    Starting Energy/mass
    Particle Pair = 0
    BH mass = 10
    Total mass/energy = 10

    Create particle pair by borrowing energy/mass from BH
    Particle pair = 2
    BH mass = 8
    Total mass/energy = 10

    One particle falls in, the other escapes
    Particle pair = 1
    BH mass = 9
    Total mass/energy = 10

    Notice that the total energy never changed, just the location. And also notice that the BH mass was reduced.

  6. #36
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    Ok, I'm sorry, I was confused. lol

    I understand that perfectly. I was under the impression you were talking about particles that just pop up at random in the universe. Energy that appears litterally out of no where and then anihilates itself. I read about this type of energy the other day, but I can't remember where. They say that because it only appears for a brief moment that the conservation law still holds true since it anihilates itself right afterwords.

    I didn't realize this energy was borrowed from the black hole itself. Thanks once again for unconfusing me. lol

  7. #37
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    Quote Originally Posted by dvb
    Ok, I'm sorry, I was confused. lol


    I didn't realize this energy was borrowed from the black hole itself. Thanks once again for unconfusing me. lol
    Remember, that this is an extremely simplified explanation to help you picture what is happening.

  8. #38
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    So you're saying that the energy isn't borrowed from the black hole?

  9. #39
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    Quote Originally Posted by dvb
    So you're saying that the energy isn't borrowed from the black hole?
    No-no... More like it is, but that's an extremely simple way to consider it.

  10. #40
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    Quote Originally Posted by freddo
    Quote Originally Posted by dvb
    So you're saying that the energy isn't borrowed from the black hole?
    No-no... More like it is, but that's an extremely simple way to consider it.
    Thanks freddo and Tensor

    I'll take your words for it.

  11. #41
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    ...

    Great read! More!!

    I'd like to hear more about the possibilities of White Holes and their relation to Worm Holes. Are these just mathematical possibilities? I remember reading a while back that White Holes couldn't exist because the second they interacted with matter they were destroyed. Also, in theory, White Holes could only have existed early in the Universe. If memory serves, this was a possiblity introduced in "Brane Theory" because of the initial titanic collision of branes. Is this a fairly accurate interpretation or am I out in left field? 8-[

  12. #42
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    I have a question.

    Why can't we calculate a volume for the black hole using the space confined by the event horizon?

    This isn't to be confused with the volume of space contained by the matter (which goes to zero), but a volume with the event horizon distance as the diameter. As far as I know, we can roughly estimate the diameters of the black hole, couldn't we just calculate the volume using that?

  13. #43
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    Quote Originally Posted by Alex W.
    I've always had the problem with the singularity being a mass with zero volume... is this just a simplification for the equations? Because I can't imagine the mass reaching zero volume in anything less than infinite time. :-?

    Hell, it's meant to be confusing, it's a black hole, it messes with relativity in crazy ways.
    Infinite time is exactly what you may have at the "center" of a black hole!

  14. #44
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    Re: ...

    Quote Originally Posted by MoMo
    Great read! More!!

    I'd like to hear more about the possibilities of White Holes and their relation to Worm Holes. Are these just mathematical possibilities? I remember reading a while back that White Holes couldn't exist because the second they interacted with matter they were destroyed. Also, in theory, White Holes could only have existed early in the Universe. If memory serves, this was a possiblity introduced in "Brane Theory" because of the initial titanic collision of branes. Is this a fairly accurate interpretation or am I out in left field? 8-[
    One would think that if a White Hole is the exact opposite of a Black Hole (its repulstion is so strong, nothing can reach it), then the instant it forms it will "explode" an disappear.

    Quote Originally Posted by Alex W
    I've always had the problem with the singularity being a mass with zero volume... is this just a simplification for the equations? Because I can't imagine the mass reaching zero volume in anything less than infinite time.

    Hell, it's meant to be confusing, it's a black hole, it messes with relativity in crazy ways.
    I don't think it's actually 0 volume. At some point there has to a form of matter (or something) that just cannot be broken down any smaller, at least not by the Black Hole's gravity. However, this level could be smaller than a Planck Length and thus for our purposes it has a volume of 0 since anything smaller than a Planck Length is meaningless.

    Quote Originally Posted by constible
    have a question.

    Why can't we calculate a volume for the black hole using the space confined by the event horizon?

    This isn't to be confused with the volume of space contained by the matter (which goes to zero), but a volume with the event horizon distance as the diameter. As far as I know, we can roughly estimate the diameters of the black hole, couldn't we just calculate the volume using that?
    You could do that, in fact it's fairly simple. You just have to calculate the distance where the force of gravity is equal to c and use tha as you diameter. For example, I believe if Sol collapsed into a black hole right now, its event horizion would extend out 3 miles.

    However, this doesn't work for spinning black holes. If a black hole spins fast enough, the singularity starts to form a ring. This in turn starts to alter the shape of the event horizion. In fact, the faster the spinning, the closer you can get to the singularity without being sucked in.

    What's even cooler is when the rotational energy of a black hole exceeds the mass energy. Spinning (Kerr) black holes actually have two event horizions. In addition to the normal EH that flips space and time, there is an inner EH that flips them back to normal. As a black hole spins, the outer EH stays the same, but the inner EH grows larger. When the rotational energy exceeds the mass energy, the event horizions actually vanish (according to theory) and you are left with a naked singularity.

    Another weird theory is that due to strange space warping, nothing can fall into a spinning black hole unless it approaches along the plane of the spin. Otherwise the warpage of space actually repels you.

  15. #45
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    I thought it had something to do with the Planck Length.

  16. #46
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    Re: ...

    Quote Originally Posted by wedgebert
    When the rotational energy exceeds the mass energy, the event horizions actually vanish (according to theory) and you are left with a naked singularity.
    And if you think singularities covered decently with an event horizon really mess with physics, naked singularities are really bad.
    At night the stars put on a show for free (Carole King)

    All moderation in purple - The rules

  17. #47
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    Quote Originally Posted by Kaptain K
    Quote Originally Posted by informant
    Layman speaking: am I mistaken in saying that given enough time - a long, loooong time - the matter that falls into a black hole eventually gets out, in the form of Hawking radiation?
    Yes and no! As Hawking said; "A black hole has no hair", meaning that all we know about a black hole is its mass, charge and spin. Anything that enters a black hole loses all individual identifuing characteristics. The particles of Hawking radiation are created at the event horizon from the gravitational energy of the black hole. So, while a black hole loses mass by Hawking radiation, technically, it is not the same matter that went in.
    (Emphasis mine.)
    If everything that enters a black hole loses all identifying characteristics, how do you know that it isn't the same matter that gets out?

  18. #48
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    Re: ...

    Quote Originally Posted by Alex W.
    I've always had the problem with the singularity being a mass with zero volume... is this just a simplification for the equations? Because I can't imagine the mass reaching zero volume in anything less than infinite time. :-?
    [layman speaking] About the infinite density/zero volume question, my guess is that that is a good model for what happens at "large" scales, but when the volume actually goes to zero quantum mechanics must step in at some point, and things may be a little different. (This is a bit like discussing the Big Bang, isn't it?) [/layman speaking]

    Quote Originally Posted by Alex W.
    Hell, it's meant to be confusing, it's a black hole, it messes with relativity in crazy ways.
    As if relativity needed the craziness...

    Quote Originally Posted by Swift
    And if you think singularities covered decently with an event horizon really mess with physics, naked singularities are really bad.
    Must… fight urge… to make… silly joke.

  19. #49
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    Quote Originally Posted by wedgebert
    What's even cooler is when the rotational energy of a black hole exceeds the mass energy. Spinning (Kerr) black holes actually have two event horizions. In addition to the normal EH that flips space and time, there is an inner EH that flips them back to normal. As a black hole spins, the outer EH stays the same, but the inner EH grows larger. When the rotational energy exceeds the mass energy, the event horizions actually vanish (according to theory) and you are left with a naked singularity.

    Another weird theory is that due to strange space warping, nothing can fall into a spinning black hole unless it approaches along the plane of the spin. Otherwise the warpage of space actually repels you.
    Facinating!!!

    That's the first I've heard of a dual event horizon, or a naked singularity for that matter. Thank you for your knowledge!

    *steals wedgebert's brain*

    Edit: Woops spelling

    Quote Originally Posted by informant
    Quote Originally Posted by Kaptain K
    Quote Originally Posted by informant
    Layman speaking: am I mistaken in saying that given enough time - a long, loooong time - the matter that falls into a black hole eventually gets out, in the form of Hawking radiation?
    Yes and no! As Hawking said; "A black hole has no hair", meaning that all we know about a black hole is its mass, charge and spin. Anything that enters a black hole loses all individual identifuing characteristics. The particles of Hawking radiation are created at the event horizon from the gravitational energy of the black hole. So, while a black hole loses mass by Hawking radiation, technically, it is not the same matter that went in.
    (Emphasis mine.)
    If everything that enters a black hole loses all identifying characteristics, how do you know that it isn't the same matter that gets out?
    That's pretty much the same question I asked in this thread earlier. lol[/quote]

  20. #50
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    With emphasis on same, this time.

  21. #51
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    The particles of the Hawking radiation are created outside of the event horizon, so they can hardly be the same particles that fell past the event horizon into the black hole.

  22. #52
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    Normally, the particle and antiparticle of a pair which spontaneously form recollide immediately, so there's not net gain of matter. Near a black hole, one particle (the antiparticle, for example) falls into the black hole, and the other escapes, so there's going to be one extra particle, and the black hole will have absorbed an antiparticle, "losing" mass.

    IIRC.

  23. #53
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    Quote Originally Posted by Alex W.
    Normally, the particle and antiparticle of a pair which spontaneously form recollide immediately, so there's not net gain of matter. Near a black hole, one particle (the antiparticle, for example) falls into the black hole, and the other escapes, so there's going to be one extra particle, and the black hole will have absorbed an antiparticle, "losing" mass.

    IIRC.
    The black hole doesn't lose mass because it absorbs an antiparticle. Sometimes the antiparticle is the one that escapes while the regular particle is caught, however there is still a net loss to the black hole.

    What happens is that the energy to create the particles comes from the gravitational energy of the black hole. When one particle escapes, it means that the black hole lost 50% of the energy required to make the virtual particle pair and thus you have a net loss in energy, and since e=mc^2 is also m=e/(c^2), you have a net loss in mass as well.

  24. #54
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    Quote Originally Posted by Alex W.
    Normally, the particle and antiparticle of a pair which spontaneously form recollide immediately, so there's not net gain of matter. Near a black hole, one particle (the antiparticle, for example) falls into the black hole, and the other escapes, so there's going to be one extra particle, and the black hole will have absorbed an antiparticle, "losing" mass.

    IIRC.
    Antimatter has positive mass.

  25. #55
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    I can understand that. But the original question was:

    Quote Originally Posted by informant
    Layman speaking: am I mistaken in saying that given enough time - a long, loooong time - the matter that falls into a black hole eventually gets out, in the form of Hawking radiation?
    Not individual particles, but ‘matter’ in a broad, collective sense.

  26. #56
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    Right, I think I've got it now.

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