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B Material for black hole travel

  1. Nov 27, 2016 #1
    So I have been watching COSMOS of late and in the 4th (I think) episode it states the possibility that other universes exist inside of black holes. I am aware of the immense strength of a black hole's gravitational pull so my question is this: Is there a material strong enough to resist it and go through in one piece? If so is there a chance that something like say a droid or robot built from this material can make it through?
     
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  3. Nov 27, 2016 #2

    Drakkith

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    There is not, and the idea that other universes exist within a blackhole is extremely speculative. I wouldn't take it seriously.
     
  4. Nov 28, 2016 #3
    Larger mass black holes have smaller tidal forces at the event horizon. Super-massive black holes don't require any special material to survive passing through. Getting out again is impossible, though.
     
  5. Nov 28, 2016 #4

    Nugatory

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    Not only is getting out impossible, but once through the event horizon it is impossible to avoid traveling (rather quickly) to the singularity at the "center" - and the forces there are strong enough to destroy anything. So even though you can survive entering a supermassive black hole, you don't get much time to look around.

    (Khashishi already knows this, of course - but others following the thread may be interested)
     
  6. Nov 28, 2016 #5

    OCR

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    Do you define forces as anything ... ?
     
  7. Nov 28, 2016 #6

    Drakkith

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    Not in this context, no. Forces cannot be destroyed. They are simply descriptions of the interactions between objects.
     
  8. Nov 28, 2016 #7

    OCR

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    :ok: ... that works for me.
     
  9. Nov 29, 2016 #8
    Normal matter (as in atoms) disintegrates even in the less outrageous conditions of a neutron star.
    Even if such a material could exist, you would never find out what happened to your droid after it has crossed a BH event horizon as it could not transmit any signal to the outside.
     
    Last edited: Nov 29, 2016
  10. Nov 29, 2016 #9
    Tell me if I am wrong, but isn't it once a person gets Close to the event horizon or passed it. from anyone else's view point they are infinitely "frozen". So my question is if we see the person frozen in time, but he actually feels time move on will he be moving through the black hole in a normal time or will infinite amount of time pass before he falls in. Are we seeing him frozen in time just a side affect of the gravitational distortion near a black hole. Sorry if my question doesn't make sense.
     
  11. Nov 29, 2016 #10

    jbriggs444

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    The answer to the question you are asking depends on a choice of coordinates. You are, in effect, asking what sequence of events for an outsider are judged to be simultaneous with the events of the traveler falling closer and closer to the event horizon. Simultaneous means "has the same time coordinate". There is a choice of coordinates which arrange things so that a sequence of events leading up to the traveler passing the event horizon is simultaneous with a sequence of events where an outsider lives forever. If one uses this set of coordinates, the description of "frozen in time" makes a certain amount of poetic sense.

    But these (Schwarzchild) coordinates do not extend continuously through the event horizon. They become invalid (aka "singular") at the horizon. So they are of limited value in describing the traveler's complete fall.
     
  12. Nov 29, 2016 #11
    As seen by an external observer, the infalling person appears to be moving ever more slowly due to time dilation.
    In principal they would appear to slow to a standstill (frozen) when they reach the event horizon ... but ...
    the time dilation also causes them to appear increasingly redshifted.
    So some time before the horizon is reached, any light they emit would fade away into radio wavelengths, eventually to the point of being undetectable.
     
    Last edited: Nov 29, 2016
  13. Nov 29, 2016 #12
    Makes sense thank you!
     
  14. Nov 29, 2016 #13

    Nugatory

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    From the point of view of an outside observer, the falling person never reaches the event horizon - but that doesn't mean it didn't happen, it just means that the outside observer didn't see it happen. Just because I don't see something doesn't mean it didn't happen.

    The falling person moves through the event horizon in a perfectly ordinary fashion, feeling no time dilation, no slowing time, nothing strange going on around them.

    And even though I as an outside observer never see the infaller pass the horizon (as rootone suggests, they fade to invisibility as the outgoing light is redshifted down to nothing) or reach the event horizon, two important times do come up quite quickly. First, there is the last moment that I can send a radio message to the infaller and receive a reply; and a bit after that there is the last moment that, if I send a message, the infaller will receive it. Miss that deadline and the infaller will have died at the central singularity before the message gets to them.
     
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