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How many Hubble Spheres are in the universe?

  1. Jul 25, 2015 #1
    From what I understand, our Hubble's sphere is just relative to earth and has a diameter of 93 billion light years putting the edge of the observable universe at 46-47 billion light years away.

    So every object in space will essentially have it's own Hubble's sphere and objects near the edge of our universe will have there own Hubble's sphere relative to their point in space. Wouldn't that make the universe infinite and it's simply filled with Hubble sphere's?

    Also, if the configurations that matter can be in is finite wouldn't that mean there's infinite versions of you and of earth especially after what NASA said Thursday about earth size planets being quite common vs say Jupiter sized planets.

    Thanks
     
  2. jcsd
  3. Jul 25, 2015 #2

    marcus

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    The basic idea is right: unless it loops around back on itself some how it looks like the universe would be spatially infinite.

    there is a confusion of language, though, that you get in the popular media and maybe in professional research writing sometimes too.

    the currently observable region of the universe does have a radius of around 46-47 billion LY, like you say,
    but the Hubble distance is something else.

    Technically the current Hubble radius is a way of keeping track of the expansion rate. It is the size of those distances which are currently expanding at speed c.
    It is currently about 14.4 billion LY.

    This causes no end of confusion because science journalists and other people speak of it as a limit to what we can see and talk as if this 14.4 billion LY is the radius of the observable region.
     
    Last edited: Jul 25, 2015
  4. Jul 25, 2015 #3
    Hi

    The second part of your question. NASA's statements isn't connected in any way. However, there may be a few billion Earth like planets in our galaxy and there are a hundred billion or so galaxies. Not an infinite number but 'a lot'.

    1,000,000,000 x 100,000,000,000. Or 100,000,000,000,000,000,000 earth like planets.
     
  5. Jul 25, 2015 #4

    Chronos

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    The short answer is one for each obsrerver
     
  6. Jul 26, 2015 #5
    I don't know - never really liked that arguement.
    It depends upon which increases faster - the number of configurations or the number of spheres.
    And infinity is difficult to work with.

    Just suppose that each sphere does not overlap but is edge on edge,
    And that we have only 2 objects to choose from. One object, M , to be the observer, at O. and the other, N, the observed.

    If sphere S0 has an expanse from A to B, then just linearly, M can observe N at an infinite number of locations in the interval AB. Thus, an infinite number of spheres is already needed, to ensure a repetition, ( if we keep M as the observer in all spheres, but I am not sure if that condition is necessary ).

    Of course, one can say that N at a certain distance R from M is the same whether on the left or right and is just a spacial orientation. In which case the number of orientations has decreased by a factor of 2 - ie infinity/2 !

    Similarly, that can be extended to the 2-D and 3-D, and the number of objects to choose from, say for elements N could be set at 100. Or add in photons, quarks, and all the other particles, and determinig combinations and permutations, which ends up as a realy large number. A really large number = X.

    So we need X x Infinity numbers of spheres.

    Then one can ask, in this X x Infinite number of spheres is there an interval where the likelihood of a another sphere exactly the same as sphere S0 can occur. Are there many intervals and what is the probability of occurance, or none?

    The final question then, is,
    In an infinite universe, of Infinite x X x Infinite number of spheres, how many times is sphere S0 repeated, if ever?

    My mathematical skills for infinity breakdown for a solution, and that is assuming the logic makes sense also.

    Cheers!
     
  7. Aug 13, 2015 #6

    Chronos

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    Each observer in the universe has their own Hubble sphere that is constrained by the age of the universe at the time they observe it. This does not suggest an infinite set of overlapping Hubble spheres. Each Hubble sphere is unique in the sense remote regions appear as they were in the past of that unique location in the universe.
     
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