Event Horizon expands or objects fall in?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Dinosaur, Jun 10, 2005.

  1. Dinosaur Rational Skeptic Valued Senior Member

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    From the point of view of a distant observer, it is supposed to take an infinite amount of time for an object to pass through the event horizon of a black hole.

    I have no intention of disputing the above claim. I trust General Relativity as described to me by those who know a lot more than I do.

    Due to gravitational red shifting, a distant observer would never see an object pass through the event horizon, so it really does not matter how much time is required. An object gets dimmer and dimmer and and fades from view as it approaches the event horizon.

    It occurred to me that some explanation is required since I think there is reason to believe that black holes get more massive and the event horizon gets bigger in finite time.

    My explanation is as follows.
    • Assume a black hole with MassA And a spherical event horizon at distance RadiusA from the center.

      Further assume a more massive Black hole with (MassA + M) has an event horizon at (RadiusA + R)

      As a lot of matter swirls toward the event horizon at RadiusA, it seems possible that M amount of mass might get inside (RadiusA + R), without reaching RadiusA. If this happens, the conditions exist for a black hole with (MassA + M) and horizon at (RadiusA + R).
    It seems to me that in finite time the event horison of a black hole can expand due to matter falling toward the original event horizon.

    Thus, from the point of view of a distant observer, nothing is seem passing through an event horizon, but the observer can see the event horizon expanding in finite time.

    Does the above seem reasonable?
     
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  3. superluminal I am MalcomR Valued Senior Member

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    I have the same question.

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  5. NO1 I Am DARKNESS Registered Senior Member

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    absolutely - that would be evident with the existance of sister galaxies where there are multiple event horizons
     
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  7. halucigenia Registered Member

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    Dinosaur, It may seem odd that you can never see anything falling past the event horizon but that the event horizon still expands. But I think that you are forgetting the relative in relativity, though an observer outside the black hole may never see anything ever passing the event horizon an observer that was actually passing through the event horizon may not actualy notice anything if the black hole is large enough. It's not that matter never actually falls through the event horizon, only that external observers never actually see it.
    Does that solve the problem?
     
  8. blobrana Registered Senior Member

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    Hum,
    Yeah,
    Easy when you know…
    But, what meaning would an object falling into a blackhole have, if the universe outside had, by that time, ceased to exist…???

    Is it like the sound of one hand clapping?
     
  9. halucigenia Registered Member

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    No, its more like - if a burning tree falls into a black hole and there is no one there to see it does it still emit light.

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  10. Novacane Registered Senior Member

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    Your guess is as good as mine on that one. One way to find. The next time you're passing by the core of M-87, toss in a burning tree and find out.

    Novacane
     

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