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Light from the big Bang/Inflation

  1. Sep 5, 2011 #1
    Okay, so here's my questions:

    1. Why can't we see the light from the big bang? If it happened 14 billion years ago, shouldn't we be able to see the light from the big bang by now? Or is the earth and everything else moving away from the spot of the big bang faster than or at the speed of light? (Space itself can move at rates that are technically faster that light, right?)

    2. If the universe where spherical, then the universe could be bigger than 13-14 bil. LY in diameter, right?

    3. What do we think the singularity was "Made out of"? Dark matter/Energy, strings, energy, etc.


  2. jcsd
  3. Sep 6, 2011 #2


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    We can see nothing beyond the surface of last scattering. Period.
  4. Sep 6, 2011 #3
    Light is emitted form the centre of the sun, yet we cant see the centre of the sun. This is becuase the plasma is opaque, so one can only see the surface. Similarly the CMB was emitted 380,000 years after the big bang. This is known as the era of recombination. The CMb at the time of recombination is an opaque plasma like the surface of the sun , hence we cannot get any lights from the big bang.
    However the structure of the CMB can give us clues as to what happened before the era of recombination. But it is not a direct observation of the light.
  5. Sep 6, 2011 #4


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    We can! It's called the cosmic microwave background. This is the radiation that decoupled from matter as soon as the universe cooled to the point where neutral hydrogen could form. It has since been streaming across the cosmos...

    It's important to point out that the observable universe is ~ 28 Mpc -- the actual universe is likely much larger -- perhaps infinite. The observable universe is, however, very nearly flat. If the universe is in fact spherical, then it has a comparatively large radius with our observable universe occupying only a small, locally very nearly flat, portion of this sphere.

    Most think the singularity simply disappears when a more complete theory of gravity is implemented.
  6. Sep 6, 2011 #5
    Great explanations here:

    Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe

    Davis, Tamara M.; Lineweaver, Charles H.
  7. Sep 7, 2011 #6
    Good article that gives physical feel to what is going on.
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