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  1. #1
    Aunt Buffy's Avatar
    Aunt Buffy Guest

    Default !!! Black Hole Gravity - speed of gravity



    How can black holes have gravity when nothing can get out because escape
    speed is greater than the speed of light?



  2. #2
    CeeBee's Avatar
    CeeBee Guest

    Default !!! Black Hole Gravity - speed of gravity

    "Aunt Buffy" <C@t.astrophy> wrote in alt.astronomy:


    This is called cause and effect.

    You just asked "How can the Sun produce photons when it's constantly
    shining so bright?"

    Nothing can get out of a black hole because of the gravity, responsible
    for escape velocities higher than the speed of light.



    --
    CeeBee


    EMH Mark I: "Stop breathing down my neck."
    EMH Mark II: "My breath is merely a simulation."
    EMH Mark I: "So is my neck. Stop it anyway."


  3. #3
    Llanzlan Klazmon The 15th's Avatar
    Llanzlan Klazmon The 15th Guest

    Default !!! Black Hole Gravity - speed of gravity

    "Aunt Buffy" <C@t.astrophy> wrote in news:9z5Ac.261$Mx.8@newsfe2-
    gui.server.ntli.net:


    Physics FAQ:

    http://math.ucr.edu/home/baez/physic...lack_gravity.h
    tml

    LK

  4. #4
    Starlord's Avatar
    Starlord Guest

    Default !!! Black Hole Gravity - speed of gravity

    Because it is their GRAVITY that pulls everything into the Black Hole.


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    "Aunt Buffy" <C@t.astrophy> wrote in message
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    escape


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  5. #5
    Bill Sheppard's Avatar
    Bill Sheppard Guest

    Default !!! Black Hole Gravity - speed of gravity

    From Aunt Buffy:


    Good question. Many researchers believe gravity "propagates" from its
    source at the speed of light. If this is so, how does a black hole's
    gravity 'get out' of the event horizon, apparently with total ease? oc


  6. #6
    Aunt Buffy's Avatar
    Aunt Buffy Guest

    Default !!! Black Hole Gravity - speed of gravity

    A recent experiment measured gravity and concluded that it travels at the
    speed of light. Thus if the sun disappeared Earth would continue in its
    orbit for a 8 minutes before going off on a "tangent".

    So if the speed of gravity is "the speed of light" how can it escape (and
    e.g. force an accompanying star to shed its material to feed the black
    hole)?

    Llanzlan Klazmon The 15th pointed me to
    http://math.ucr.edu/home/baez/physic...ack_gravity.ht
    ml

    My interpretation is: "Gravity waves" that we see outside of the blackhole
    were generated before the formation of the black hole and that due to the
    time dilation effect take "a long time" to emerge and become noticable to
    us( outside of the event horizon). Thus the gravity we are seeing outside of
    the black hole now could well have been generated 10000years ago (more
    likely longer ago). The gravity waves since the creation of the black hole
    are not able to escape.

    Am I out of my depth?



    "Aunt Buffy" <C@t.astrophy> wrote in message
    news:9z5Ac.261$Mx.8@newsfe2-gui.server.ntli.net...



  7. #7
    Paul Lawler's Avatar
    Paul Lawler Guest

    Default !!! Black Hole Gravity - speed of gravity

    "Aunt Buffy" <C@t.astrophy> wrote in message
    newsU8Ac.4$wS4.2@newsfe6-win...

    Yes, but you're in good company. <g>



  8. #8
    Double-A's Avatar
    Double-A Guest

    Default !!! Black Hole Gravity - speed of gravity

    "Aunt Buffy" <C@t.astrophy> wrote in message news:<9z5Ac.261$Mx.8@newsfe2-gui.server.ntli.net>...



    One answer might be that because gravitons are virtual particles, like
    their cousins the virtual photons that mediate the electrostatic
    force, they might not be affected by the gravitational field they
    create.

    The thing that I wonder about is since time slows to a near stop at
    the event horizon of a black hole, how is it that the black hole
    itself can move through space and change directions as it interacts
    with other objects. In many cases black holes are in orbits with
    stars or neutron stars. If the companion star is massive, the black
    hole must move and change direction constantly as it reacts to its
    companion and traces out an elliptical orbit.

    Now how can the black hole, and objects that are supposedly suspended
    in almost infinitely slow time on its event horizon, be at the same
    time moving and changing direction in seemingly real time as the black
    hole moves through space on its orbit?

    Double-A

  9. #9
    Bill Sheppard's Avatar
    Bill Sheppard Guest

    Default !!! Black Hole Gravity - speed of gravity


    in almost >infinitely slow time on its event horizon,
    through space

    And, how come a stellar mass black hole will still express exactly the
    same gravity as it did prior to the collapse? That is to say, any
    planets orbiting the star will be unaffected in their orbits after the
    collapse... how coom ???
    oc


  10. #10
    Bill Sheppard's Avatar
    Bill Sheppard Guest

    Default !!! Black Hole Gravity - speed of gravity

    From Aunt Buffy:


    Yeah, that was the Fomalant-Kopeikin experiment. Touted as measuring the
    "speed of gravity", it was a unique, roundabout way of measuring the
    speed of light, nothing more, nothing lass. See-
    http://www.space,com/scienceastronom...ed_030116.html

    http://math.ucr.edu/home/baez/physic...k_gravity.html

    Hoo boy. "Fossil fields" no less. And 'virtual gravitons' (!), virtual
    photons, and what else.. angels, imps, and Sky Pixies.. all to explain
    how gravity 'gets out' of a black hole. Hmm..

    blackhole were

    A bit out of your tree, perhaps. But you're certainly not alone. The
    mainstream does not grasp the clear distinction between gravity and
    'gravity waves'. The latter should more correctly be defined as _spatial
    acoustic pressure waves_ in the fabric of space, analogous to sound
    waves in air (jb's protestations notwithstanding). And these mis-named
    'gravity waves' DO propagate at c.

    They are _related_ to gravity, and are generated by massive
    gravitational events (such as a supernova detonation or a binary BH
    coalescence), but they are NOT gravity.
    The mainstream's void-space paradigm(VSP) precludes the
    understanding of gravity as the FLOW of the spatial medium into a
    gravitating mass. Whether the mass is a normal star or a black hole is
    irrelevant. The VSP precludes understanding that gravity's influence is
    _instantaneous irrespective of distance_ just as Newton originally
    observed. And it's instantaneous with or without an intervening event
    horizon.
    While this may be at odds with the interpretation of GR
    on the "speed of gravity", it is a fact. If it's not, and space is a
    "void", then we're stuck with "fossil fields", 'virtual gravitons',
    virtual photons, angels, imps, and Sky Pixies. oc


 

 
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