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Black Hole matter

  1. Jul 4, 2011 #1
    What happens to it or where does it go after being sucked into a Black Hole?
     
  2. jcsd
  3. Jul 4, 2011 #2

    bcrowell

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    It gets compressed to infinite density and remains permanently at the singularity at the center of the black hole. From the outside, you can still tell that its mass-energy went in there, because you can detect its contribution to the black hole's gravitational field.
     
  4. Jul 5, 2011 #3
    Thank you for your response. I hate to say that I still don't know where the matter is stored. Does the Black Hole act as a portal and send this material into another Universe (as in a multi-verse) or is it a Cosmic sack with an angry mouth? I understand Black Holes suck in and compress any unfortunate matter that comes too close, however, I'm having trouble visualizing the final process. What is on the backside of the Black Hole? Can we "see" all the way around them? And what is the end game for a Black Hole? Sorry for being so darn dense.
     
  5. Jul 5, 2011 #4

    bcrowell

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    Are you visualizing it sort of like a flat circle or a pit in the ground? It's more accurate to visualize it as a sphere with a point at the center. The point at the center is where all the mass is. (There are some oversimplifications in this image, but I'm trying to get across the general idea.)
     
  6. Jul 5, 2011 #5
    I have seen many artistic renderings of a Black Hole. I would describe it as a huge vortex sucking anything and everything that comes too close. I see this darkened space with glitttering matter being sucked in as it circles the mouth of the Black Hole. I understand the basic concept but want to know the overall shape of a Black Hole and what it will eventually do with all the matter it has ingested?
    Thanks.
     
  7. Jul 5, 2011 #6

    Drakkith

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    Compression of the matter should result in the matter converting into another form correct? Just like how a star collapses into a neutron star, with the protons and electrons being converted into neutrons. And if it turns into a black hole, is it reasonable to expect matter to be converted into, say, photons? Wouldn't they have to be converted into a form that doesn't obey the Pauli Exclusion Principle?
     
  8. Jul 5, 2011 #7

    bcrowell

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    Basically the overall shape is a sphere, and the matter gets compressed to zero size at its center.

    GR doesn't describe the singularity as a point in spacetime. Therefore I don't think there is any meaningful sense in which you can ask questions like whether the exclusion principle applies. You can't state the exclusion principle without using the notion of space. The no-hair theorems say that the singularity's only observable properties are its mass, charge, and angular momentum.

    Assuming that Hawking radiation acts as conjectured, it will consist of some arbitrary mixture of particles, including both bosons and fermions, hadrons and leptons. Photons are just the most copiously produced particle because they have zero mass, so thermodynamically there are more available photon states. In this sense, the matter loses all "memory" of its character. All the usual conservation laws of particle physics, e.g., conservation of lepton number, are violated. There's a nice discussion of this in Wald.
     
  9. Jul 5, 2011 #8

    DaveC426913

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    Artistic impressions can be misleading.

    1] The BH itself is a sphere, symmetrical from all viewpoints.

    2] It is often portrayed with an accompanying accretion disc of infalling matter. This accretion disc is not actually part of the BH itself. The infalling matter forms a disc as it falls, similar to (but not the same as) how a star's planets tend to form a disc around the star.

    3] BHs do no more sucking than anything else of the same mass. If the sun were magically turned into a BH without changing its mass, the Earth and all the planets would happily continue orbiting it with no immediately discernable change.

    What makes a BH (and other ultra-dense objects) so powerful is that they are physically small. Gravity falls off as the square of the distance. The corollary is that gravity increases exponentially the closer you get. Standing on the surface of the Sun, you will experience 28g's. But you are 400,000 miles from the centre. If the sun shrunk to the size of a BH, you could now get muuuuuuch close to the centre without making any other changes. At 200,000 miles from the centre (half the distance), g's quadruple - 114g's. Halve it again - you're still 100,000 miles from the centre, and g's go up to 442.

    Considering BH's might be only a few miles or even less, you can get up into millions of g's. But way out at 400,000 miles, the g's are identical to the Sun, and the planets will happily orbit it at their distances.

    Not a lot of things get close enough to the sun to get eaten, so likewise, not a lot will get close enough to a black hole except under specific conditions.,
     
    Last edited: Jul 5, 2011
  10. Jul 5, 2011 #9

    Drakkith

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    So matter in the singularity being infinitely dense and occupying no volume isn't similar to multiple particles occupying the same point? I thought that seeing as how each increase in pressure (Star-White Dwarf-Neutron Star) causes the matter to change, it was just another step. And seeing as how the increase in pressure is effectively infinite, the matter would have to be converted into a form that doesn't obey the exclusion principle.

    What do you mean by GR doesn't describe the singularity as a point in spacetime? I'll have to look up more on this.
     
  11. Jul 5, 2011 #10

    DaveC426913

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    Well 'singularity' means 'our rules stop working'. So trying to describe it with current ideas is kind of meaningless.

    Certainly the matter must change. And certainly the PEP will no longer meaningfully apply.
     
  12. Jul 5, 2011 #11

    Drakkith

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    I see. Is it possible to calculate what happens to the matter between the start of collapse and the point where our math starts to break down?
     
  13. Jul 5, 2011 #12

    DaveC426913

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    Collapse of the matter?

    I think our models end at neutronium - where electrons and protons are pushed together forming neutrons that pack together, touching. If we increase gravity further, we don't know what happens to them.
     
  14. Jul 5, 2011 #13

    Drakkith

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    Alright. Thanks dave!
     
  15. Jul 5, 2011 #14

    DaveC426913

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    Last edited by a moderator: Apr 26, 2017
  16. Jul 5, 2011 #15
    If you are lucky enough, you would not feel anything special passing through the event horizon of super massive black hole, but later you would be torn up. And when you are acceterated to certain velocity close to the singularity point, your atoms, electrons would fall apart.
     
  17. Jul 5, 2011 #16

    bcrowell

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    Or maybe quark matter, but basically, yeah, I think you're right that we don't know the answer.

    In fact, fergeddabout the singularity -- semiclassical gravity even behaves badly way out at the event horizon! http://arxiv.org/abs/0902.0346 There was a nice popularization of this in the Oct 2009 Scientific American by Barcelo et al. They spin it as Exciting New Physics, but IMHO as a nonspecialist the exotic behavior of their model simply means that their model isn't to be believed.

    It would be cool if we could find out empirically what happens, but it would be sort of like the joke about astronauts going to the sun -- they have to go at night when it's not too hot.
     
    Last edited: Jul 5, 2011
  18. Jul 5, 2011 #17

    Drakkith

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    Last edited by a moderator: Apr 26, 2017
  19. Jul 6, 2011 #18

    DaveC426913

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    Tired out, gave up, threw in the towel, raised the flag.

    We were in a marathon there for a couple of hours, bouncing back and forth between the two threads. Someone had to break the cycle or we'd never get any sleep. :biggrin:
     
  20. Jul 6, 2011 #19
    In relation to quark matter http://qgp.phy.duke.edu/ might add some insight to part of the answer without having to go there (the BH) to find out.

    mathal
     
  21. Jul 6, 2011 #20

    Drakkith

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    Lol I see.
     
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