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The edge of the universe

  1. Aug 14, 2015 #1
    Dear PF Forum,
    I have a simple and cliche question.
    What is the edge of the universe?

    1. We live on the surface of the earth. It's 2 dimensions against earth 3 dimensions.
    If we start from Equador which lies on the equator to the east, we'll reach Columbia then Brazil then Atlantic ocean, continue on then Congo, then Kenya, then Indian Ocean, accross Maldives then, my country Indonesia (the only Asian nation in equator :smile:) then go on to the east, Papua, then Pacific ocean, then some small islands in Pacific, continue on then we arrive back to Equador.
    Does the universe look like that? 3 dimensions against 4 dimensions. So if we travel "east" from earth, we'll go back to earth again?

    2. Consider this simple drawing
    B <-------- 46 gly ------------ earth ---------------- 46gly -------------> A
    If we travel east from earth and on and on, and we reach Galaxy A, 46 giga light year "east" from eart.
    What would that be?
    Earth ----------------- 46 gly ------------------> A ------------------->?
    Can we reach back to B?
    Earth ----------------- 46 gly ------------------> A ------------------ n distance ----> B

    3. Or this model
    I choose 46 gly because it's the time of big bag adjusted by Hubble law.
    B <-------- 46 gly ------------ earth ---------------- 46gly -------------> A
    Earth ---------------- 46gly -------------> A --------------- 46 gly -------------> C
    A --------------- 46 gly -------------> C ---------------- 46gly -------------> D
    C ---------------- 46gly -------------> D ---------------- 46gly -------------> E
    And no end of it?

    If we come up 46 gly by the age of the universe 13.8 billions light year adjusted by Hubble law,
    4. Are there any galaxies beyond A to the "east"?
    5. Supposed there are galaxies beyond A that we can't see. Are the distance of those galaxies still conform with Hubble law, but they are already too fast that we can't see their light?
    6. If there are other galaxies beyond A to the "east", did they come from "our" big bang?

    Thanks for any answer to fullfill my curiousity.
  2. jcsd
  3. Aug 14, 2015 #2


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    There is no known answer to this question. As far as we know, there is no higher dimensional space.

    You are here talking about the observable universe. There is no indication that the Universe should do anything but continue on outside of that. Of course, there is no way of knowing that.

    It is not about the galaxies moving, it is about space expanding.

    According to the standard model of cosmology at the present time, the big bang happened everywhere in the universe at once.
  4. Aug 14, 2015 #3


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    Staff: Mentor

    There is no known edge to the universe.

    We don't know. It is certainly possible that the shape of the universe leads to a 'closed' universe, where traveling in one direction eventually causes you to loop back around to your starting point, but it could just as likely be that the universe is either 'open' or 'flat', both of which may mean the universe is infinite in size. Note that even a universe that is closed is not required to be embedded within a 4th spatial dimension. There is a difference between extrensic curvature (measured with respect to a higher dimension) and intrinsic curvature (measured within existing spatial dimensions).

    See here for more: https://en.wikipedia.org/wiki/Shape_of_the_universe

    As you said, it would be a galaxy.

    Yes they did.
  5. Aug 14, 2015 #4


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    I don't mean to be picky, but... is that quote modification alright with you?
  6. Aug 14, 2015 #5
    That makes sense, at least for me.:smile:
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