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Information and black holes

  1. Mar 9, 2013 #1
    How can we know anything about black holes if nothing, not even information can escape the event horizon?

    If we can know the mass and gravity of a black hole it is because some information is being sent by the black hole, but how can this be possible if nothing, not even light, can escape once beyond the event horizon?

    Like Einstein said, if you cannot explain something in simple terms you do not understand it, so please, no ego ramblings.
  2. jcsd
  3. Mar 9, 2013 #2
    We dont know what is beyond the event horizon. We can only tell A BH' s gravity by how it affects other stellar objects. The size of theSchwarchild radius we can infer its mass. The larger the radius the greater the mass.
    We can also calculate the spin of a blackhole by examining its accretion Disk. If you want all the mathematics and understanding of what we can measure on a BH this article covers it. However its a 91 page technical article.


    In 12.2 it describes one possible methodology ti tell if a BH has a singularity or solid core. This is important to distinquish between Neutron stars and BH's.
    Essentailly the only data collectable on BH's is found by its effects on its surroundings and the types and amount of radiation we can detect from them.
  4. Mar 10, 2013 #3
    This means that either the graviton does not exist and gravity is just spacetime curvature {what are the implications under QM?} or that the graviton does exist but it must travel at a speed faster than light {what are the implications under relativity?}.

    If the graviton existed, it has to be able to escape the event horizon. Otherwise there would be no gravity effects from the black hole. Because there is gravity emanating from the black hole and if the graviton exists, then the graviton must be able to escape the event horizon and the only way to do this is faster than light speed.

    Gravity as a residual force from another membrane {dimension} cannot be a particle for the same reason mentioned above. So then string theory is compromised {does anybody care?}

    So, black holes disprove the graviton, string theory and the unification of QM and relativity. Or relativity is "incomplete" {wrong}. Already Bell's theorem proves that relativity is "incomplete".

    Just trying to make sense of it all, like all of us.
  5. Mar 10, 2013 #4


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    The idea that gravitons, if they exist, must escape the event horizon in order to mediate gravitation from the black hole is not true. They are not "real" particles, but virtual ones, and are subject to different rules than real particles. I believe there should be a thread about this already if you use the Search function at the top of the page.
  6. Mar 10, 2013 #5
    I am sorry, but are you saying that the speed of light limit does not apply to virtual particles?
  7. Mar 10, 2013 #6


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    OK, you clearly do not know what you are talking about.
  8. Mar 11, 2013 #7
    So explain then. Lower yourself to my ignorance oh mighty one.
  9. Mar 11, 2013 #8
    Try this link.

    http://burro.astr.cwru.edu/stu/advanced/stars_blackhole.html [Broken]

    As I've stated before nothing leaves the event horizon. The only way to get any information on a blackhole is through its violent effects on its surroundings.
    Gravitons may or may not exist. You wont find gravitons as part of the standard model. At least not till we prove or disprove its existence.
    Gravity is best thought of in terms of spacetime geometry.
    changes in mass changes that geometry. So in many ways gravity is an effect.
    In regards to virtual particles they can quantum tunnel Ill let others describe that. As it is something I am only starting to understand. However its not really important to understand in regards to how we calculate a BH's mass or spin. The first article I posted describes all the formulas one can measure on a BH. All of them measure the accretion disk and jets.
    From those measurements we can infer the mass and spin.
    Other related topics is the
    Schwartzchild metric and the no hair theorem.


    this link describes a bit on how to go about calxulating a BH mass without the mathematics. Its not the greatest site but should give you some idea.
    Last edited by a moderator: May 6, 2017
  10. Mar 11, 2013 #9
    I am not arguing against or in favor of a graviton. What I am inquiring about is what others are thinking {information I read in some other places}.

    The only way gravity could emanate from the event horizon is if {in the case a graviton existed} it had an escape velocity higher than the speed of light.

    The reason of me posting this was to see if any other explanation was there to this hypothesis.

    By the type of answers, it seems there is not.
  11. Mar 11, 2013 #10
    Think you missed the part where gravity is a geometric effect. It does not radiate as per se rather it changes the spacetime geometry
  12. Mar 11, 2013 #11
    I get that. The point of the graviton and gravity waves is that it would radiate and in order to do so it has to have a speed. All agree on the speed of light. The black hole shows this cannot be.
  13. Mar 11, 2013 #12
    Well as far as I know a gravity wave has never been measured. However gravity waves can also be caused by spacetime curvature/geometry changes. Gravity waves do not validate the existence of the graviton.
  14. Mar 11, 2013 #13


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    No, it does not. Just because no one has explained it to you does not mean your belief is true. Unfortunately I don't know the details, so I cannot hope to explain how virtual particles mediate forces and how it works with black holes. However, I do remember seeing multiple threads about it over the years here at PF so I am near certain that nothing about a black hole keeps gravitons from mediating gravitation. Have tried using the search function at the top of the page to look for similar threads here on PF? They may answer your question.
  15. Mar 11, 2013 #14
    I understand the rudimentaries of Hawking radiation and Unruh radiation.
    I've yet to look at virtual gravitons and how they work.
    If I recall though perturbative quantum gravity is a graviton virtual particle model that has been used to describe low level entropy at a blackhole horizon.
    However cannot say for sure.
  16. Mar 12, 2013 #15


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