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Does the Type of vaccum matter?

  1. Oct 2, 2007 #1
    If light can travel through a vacuum, whats to keep it from traveling out of the "boundaries" of the universe?

    If it can, Why doesn't it?

    If it can't, what is out their must be something other than a vacuum, or the light can't travel in a vacuum.

  2. jcsd
  3. Oct 2, 2007 #2


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    According to present theory, the universe has no boundaries.
  4. Oct 2, 2007 #3


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    We don't really know about the boundaries of the universe, or if there are or are not boundaries, or if the physical laws as we understand them even apply at the boundaries.
  5. Oct 3, 2007 #4


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    If light travels there, it is in our universe.
  6. Oct 4, 2007 #5
    But still, what keeps light from "escaping" our universe? Is it the fact that their is no true vacuum in which we can prove light does travel?
  7. Oct 4, 2007 #6

    I was under the immpresion that for something to grow in size, it had to have prevu=iuos boundaries to grow past.
  8. Oct 4, 2007 #7


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    The usual picture is the two dimensional analog, the surface of a balloon, which can get bigger with no boundary.
  9. Oct 9, 2007 #8
    Wouldn't that still imply something to grow into?
  10. Oct 9, 2007 #9


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    It likely would, yes. One example is a fourth dimension. But that doesn't mean light can travel through it.

    The easiest way to think about a finite boundaryless universe is to think of it curving back on itself in 3D, like the balloon does in 2D. If a light beam heads in a straight line long enough, it simply arrives back at its starting point. It has not left our universe, nor has it encountered any sort of boundary.
    Last edited: Oct 9, 2007
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