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B Why is the CMB relatively uniform?

  1. Mar 22, 2016 #1
    This might be a stupid question due to a simplistic under standing of the Big Bang. But why is the CMB uniform across the sky. Why is it not sognificantly higher on one side from the other. Surely if the Big Bang was a point then everything would eminate from that point resulting in one side that was closer having higher reading. Thanks for any answers. Sorry if it is a stupid question.
  2. jcsd
  3. Mar 22, 2016 #2


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    It's not just a good question, but an exceedingly important one in cosmology.

    One popular notion is that very shortly after the birth of the universe, it entered an inflationary period of unimaginably rapid expansion so that by the time gravity could have a significant effect, things were already spread out pretty uniformly.

    As far as where the big bang happened, it kind of happened everywhere. Space itself just got really big really quickly.
  4. Mar 22, 2016 #3
    Thanks for the quick response
  5. Mar 22, 2016 #4
    Just thinking though for this to out run gravity wouldn't things have had to move faster than the speed of light.
  6. Mar 22, 2016 #5


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    Yes, but there's no cosmic speed limit for the expansion of the universe. The only speed limit is on how fast things can move through space.
  7. Mar 22, 2016 #6


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    This is by far the most common misconception is the early study of cosmology and is promulgated by pop-science making exactly that false statement. The "big bang singularity" was NOT a point. It happened everywhere at once. The "big bang theory" doesn't even include the singularity but instead is a discussion of what happened from about one Plank Time after the singularity to today. Contrary to the totally incorrect statements you see everywhere in pop-science, "singularity" does not mean "point" it means "the place where our math model breaks down and gives nonphysical results and we don't know WHAT is/was going on"
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