Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Falling into a Black Hole

Tags:
  1. Nov 24, 2015 #1
    I was watching a video about how an observer outside a black hole would watch someone slow to a halt at the event horizon and I don't question it, as that makes sense.

    My first question to the Astrophysicists out there is what the observer falling into the black hole would see. It would make sense to me that they would observe the rest of the universe progress through the entirety of its existence.

    Does this make sense?

    My second question is about what people say would happen for a supermassive black hole, that it would be pleasant when crossing the event horizon. If the event horizon means that no world lines can travel away from the black hole, doesn't that imply that, once crossed, a person could no longer think, as impulses in the brain travel slower than light and cannot travel from place to place, but only towards the center of the black hole? Would this also apply when getting close to the black hole (i.e. within a few kilometers of the black hole's event horizon)?

    Thanks for your time!
     
  2. jcsd
  3. Nov 24, 2015 #2
  4. Nov 24, 2015 #3

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    No, it is not an accurate description of what happens. There are several threads at PF about this which you can find by the search function or by looking at the similar discussions below.

    No, this is also not accurate. As long as the observer is not subjected to large tidal forces, it will not notice anything strange. The local speed of light is also the same as everywhere else and the point of light being unable to escape is based on the geometry of space-time, not on the local speed of light changing.
     
  5. Nov 24, 2015 #4
    Thanks very much for the redirect, I'll check that out.

    I believe I'm starting to understand. Does this imply that the local spacetime distortions are not noticeable to the infalling observer?
     
  6. Nov 24, 2015 #5
    I avoided that question because there are some that think that you might run into a "wall of fire" (http://arxiv.org/abs/1207.3123). But the older notion (and the one I still subscribe to) is that, if the observer doesn't look out the window, he will notice nothing - but that will be a very short-lived experience.
     
  7. Nov 24, 2015 #6

    Orodruin

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    This depends on how large the neighbourhood of the observer which can be considered "local" is. If tidal effects become relevant over in his local neighbourhood, they will most certainly be noticeable.
     
  8. Nov 27, 2015 #7
    We could currently be falling through the horizon of some very large, yet to be formed black hole....and we are still able to think right now. As commented already, it is really the tidal forces that are important
     
  9. Dec 1, 2015 #8
    It's a very interesting question because no one really knows the answer. We can rely on the mathematical calculations but can't be sure that the laws work the same way we think they should. Anyway, according to the latest observations, a black hole:nb) can simply spit you out (as it is sometimes the case of swallowed stars) and you won't see a thing.
     
  10. Dec 1, 2015 #9

    pervect

    User Avatar
    Staff Emeritus
    Science Advisor

    Could you provide a reference for your "simply spit you out" remarks?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Falling into a Black Hole
  1. Falling into black hole (Replies: 24)

Loading...