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I "Black" holes and "White" holes

  1. Jul 13, 2016 #1
    What makes black holes "black" and white holes "white" ? :cool:
  2. jcsd
  3. Jul 13, 2016 #2


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    Black holes absorb all radiation and matter that falls within the event horizon, and hence they are "black" (non-emitters). White holes emit radiation and matter from within, and thus are "white".
  4. Jul 13, 2016 #3
    With a black hole, space is curved so much inwards that there is no path that leads anywhere but deeper into the hole. With a while hole, space is curved so much outwards that there is no path that leads anywhere but further away from it. White holes would require a negative energy density, and hence are thought to be physically impossible, just a mathematical curiosity.
  5. Jul 14, 2016 #4


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    We cannot be certain either entity actually exists, but, we have solid evidence for black holes and virtually zero evidence favoring white holes.
  6. Jul 14, 2016 #5
    "Black holes" so called because the light that goes through it has a lower speed than the gravitational force of black holes that's why light can't get out of it, and we can't see it, so these holes called "black."
    About the "white hole", as I know, the scientists they have not yet found, but according to the law of conservation of energy, this energy that enters a black hole should get out of the white hole, and if the light is in a black hole can not escape, the white hole It acts with a repulsive force, and we see a bright light that's why "white holes" so called.
    I hope I could help you.
  7. Jul 14, 2016 #6
    Not quite, it means that light speed is slower than the escape velocity caused by gravity. Gravity is also radiating at the speed of light.

    Black holes and white holes are not related. Energy going into a black hole simply gets stuck there and then radiated away as Hawking radiation. Black holes are not wormholes to white holes, they are simply inescapable gravity pits.
  8. Jul 14, 2016 #7


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    Per GR gravity propogates at a speed of exactly c - the same as light. While we do not know what goes on inside the EH of a black hole, a wormhole appears unlikely. If light, or anything else, had a wormhole escape route, the black hole would lose mass equivalent to the escape rate. A white hole powered by a black hole would suck the black hole dry in short order. There is no evidence suggesting this happens.
  9. Jul 14, 2016 #8
    • Poster has been reminded that wikipedia is not a valid scientific reference for making assertions
    Yes, I had that in mind but incorrectly expressed

    Some footnotes from Wikipedia
    "Theoretically, it is assumed that white holes can be formed at the exit from the horizon of the black hole event substance which is in the opposite direction of the thermodynamic arrow of time. It should be understood that the full space-time map contains both black and white holes, and a separate entity only "pure" black or only "pure" white hole to complete the map of the space-time can not be in principle."
  10. Jul 17, 2016 #9


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    Not unheard of for wiki to spout unsupported bs such as this.
  11. Jul 18, 2016 #10
    I just translated this quote from russian on english.
    If you want I can give you a link on original's language and if you understand russian you can read this.
  12. Jul 18, 2016 #11
    "Theoretically" probably means "mathematically theoretically." Sure, you can have a white hole if you can have negative energy density. We've seen no indication that such a thing is physically possible.
  13. Jul 19, 2016 #12
    yes white hole is the theory as well as Hawking radiation, think you will agree that in the universe are lot of theories and few facts, so it remains to wait for confirmation from scientists
  14. Jul 19, 2016 #13
    If a black hole draws in everything within it's event horizon, and keeps drawing it deeper, does that mean the black hole is infinite? And what about white holes? Since they emit matter, could they be the other side of a black hole (assuming there is one)? I'm curious as to what kind of studies have been done on this subject.
  15. Jul 19, 2016 #14
    No white hole has ever been observed. unsurprising since this would involve exotic matter having negative gravity.
    Black holes, or at least the gravitational and other effects of black holes (eg quasars) have been observed.
    It is indeed a conundrum that this implies infinities (a singularity) at the centre of a black hole.
    We don't actually know what happens there, but the fact that the math leads to infinities is most likely an indication that whatever is going on is physics of which we currently have no idea.
    Last edited: Jul 19, 2016
  16. Jul 20, 2016 #15
    Is there any evidence [what would such evidence even look like] that the creation of a black hole is the 'big bang' of an new universe or is that just a pretty science fiction idea?
  17. Jul 20, 2016 #16
    The idea has been suggested before but as far as I know it's pure speculation.
  18. Jul 22, 2016 #17


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    What makes you think it "keeps" drawing it deeper? It draws it to the center and that's it. Black holes are finite.
  19. Jul 26, 2016 #18
    How you are saying that blackhole is finite?Is that singularity is the end??
  20. Jul 26, 2016 #19
    The singularity is simply where the math breaks down and produces nonsense results.
    It is NOT a description of a physical object.
    We DON'T KNOW what physically is going on at the center of a back hole.
    We do know that the infalling stuff is by this time no longer in the form of atoms, because atoms disintegrate before that point.
    Neutron stars, (very massive objects which are not quite massive enough to be black holes), are known to exist by observation, and what we observe IS consistent with GR math.
    The star has become mainly a soup of neutrons with other subatomic fragments mixed in.
    Last edited: Jul 26, 2016
  21. Jul 26, 2016 #20
    I know that.I am asking that without knowing the end how we can conclude blackhole is finite???
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