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

Are we in a black hole?

  1. Dec 6, 2011 #1
    I was just reading the thread "Dark matter and black holes" started by Tanzanos and in a reply our PF Mentor, Janus, mentioned that the more mass a black hole has, the less dense it needs to be.

    This reminded me of an idea I read in a book on black holes in the 1970s that as the universe contained enough mass and was of sufficient density, there was a possibility that it could actually be inside one!

    Well, a lot of matter has passed through the event horizon since then so can anyone tell me if this possibility has been explored further, or if research has uncovered data that has proved it to be impossible?
  2. jcsd
  3. Dec 6, 2011 #2


    User Avatar
    Science Advisor

    I am in the middle of reading a book "Cosmic Numbers" by James D. Stein. In it he makes the same point, that is the event horizon for the universe, as we know, is much greater than 13.7 billion light years.
  4. Dec 6, 2011 #3

    Thanks for that, I'd forgotten all about it until the thread I was reading jogged my memory,
    nice to know it wasn't just a figment of my aging imagination!
  5. Dec 6, 2011 #4
    The book you may be thinking of is The Collapsing Universe by Issac Asimov, where he makes that same point in the last few pages.
  6. Dec 7, 2011 #5


    User Avatar
    Science Advisor
    Gold Member

    If the universe were a black hole, it should have a cauchy horizon. This is not observed.
  7. Dec 8, 2011 #6
    Does that necessarily limit the volume of the universe, at least the volume that contains matter?
  8. Dec 8, 2011 #7


    User Avatar
    Science Advisor
    Gold Member

    Technically not, just the observable portion.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook