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A Question about the formation of white holes off black hole

  1. May 29, 2015 #1
    Hello,
    I had a thought about the formation of white holes off of black holes and i wanted to ask if it is possible,
    if a massive black hole is surrounded by a lot of matter(a lot of giant stars etc.) and it consumes so much matter that even a aquasar is not sufficient enough in disposing all of that energy, is it possible that the black hole in that case will become a white hole in order to dispose of all of that energy?
     
  2. jcsd
  3. May 29, 2015 #2
    Highly active black holes with a substantial accretion disk tend to result in matter and radiation being ejected (disposed of) in the from of extremely energetic jets.
    That essentially is what is happening with a quasar.
    There is no observational evidence of white holes; of quasars there is plenty.
     
  4. May 29, 2015 #3
    First,
    thank you for your reply.
    I've seen that there was an observation of a very massive gamma ray burst that occurred for about a minute in 2006 that some think might suggest the existence of white holes,
    In theory is it possible?
     
  5. May 29, 2015 #4
    There have been a number of instances of inexplicable gamma ray bursts observed, but we can't conclude that these events are evidence of white holes.
    There are other more plausible scenarios which could explain them such as merging black holes or neutron stars,
    but basically we just don't have enough to go on to reach any particular conclusion, not yet anyway.
     
  6. May 29, 2015 #5
    Thank you very much
     
  7. May 29, 2015 #6

    Chalnoth

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    White holes are time-reversed black holes. Due to entropy considerations, this means that a white hole is just a black hole where we've accidentally gotten the time coordinate going in the wrong direction (rather like playing a video tape backwards). Thus they can't actually exist (just like you can't see in reality a bunch of water splashing into a pool, popping out a diver who then lands on a platform).
     
  8. May 29, 2015 #7
    Aww, Thank you very much it is very helpful,
    I would be very glad if you can maybe explain a little about the mathematical side of this theory.
     
  9. May 29, 2015 #8

    Chalnoth

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    Essentially it comes down to the fact that all physical laws (that we know of) are symmetric in time*. A black hole is a solution to the Einstein Field Equations that is a region of space-time that light can enter but cannot escape.

    Because gravity is time-symmetric, however, it is also a perfectly-valid solution to the Einstein Field Equations to describe a region of space-time where light can never enter.

    The question becomes: which solution is correct? The answer to that question comes down to entropy: when a black hole absorbs matter, its entropy increases. If a white hole were to spit out some matter, its entropy would decrease. The first picture makes sense: it's like seeing a diver dive into a pool and create a splash. The time reverse of this doesn't make sense.

    The question, then, is why is it that the arrow of time always points in one direction? The answer is basically that there is a point in our past that had very low entropy, which makes it so that everything in our universe has a tendency to increase its entropy.

    * Technically, they follow something known as CPT symmetry.
     
  10. May 30, 2015 #9

    Chronos

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    A white hole would tend to affirm the block universe concept, which is not terribly popular as is it tends to deny causality.
     
  11. May 30, 2015 #10
    Thank you very much it is very helpful and educational
     
  12. May 31, 2015 #11

    timmdeeg

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    Just to not misunderstand you: Would the time-reversal-symmetry include physical processes like the emission of gravitational waves, the contraction of a cloud of gas, the fall of an apple from a tree and so forth? I guess that the entropy is increasing in these cases which then gives the time the 'right' direction.
    On the other side it's hard to believe that according to the EFE in principle the apple could fall upwards were it not for the second law of thermodynamics.
    Could you kindly explain a little more in detail?
     
  13. May 31, 2015 #12

    Chalnoth

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    Yes. With the apple, what happens when it falls is its energy of motion gets turned into heat and sound on impact. The time reverse, then, is a bunch of photons and sound waves combining to give the apple enough of a kick that it hops off the ground and onto the tree, where it contacts so perfectly with the broken stem that it seals and becomes part of the tree.

    All of this is a perfectly good solution to the equations of motion but it's horrifically unlikely, so much so that we don't expect any person ever to witness such an event. That is the essence of entropy increase: is about the system moving from a less probable configuration to a more probable one.
     
  14. May 31, 2015 #13
    I'm wondering whether it might be more specific to say that the block universe concept tends to assign a temporal direction to causality, which, from our point of view, tends to be kind of geocentric if you accept the multiverse concept.
     
    Last edited: May 31, 2015
  15. May 31, 2015 #14

    timmdeeg

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    Thanks for clarifiying.
     
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