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Can anyone make sense of this question.

  1. Nov 14, 2013 #1
    At what time was emitted CMB radiation which is detected at our time

    Can anyone makes sense of this question. Isn't CMB radiation emitted all of the time from the left over the big bang. I'm not asking for a answer I just don't understand this question or don't understand something about CMB. I would post this on the homework help but no one there seems to know anything about cosmology.
     
  2. jcsd
  3. Nov 14, 2013 #2

    D H

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    No. The CMB radiation was emitted during a rather short interval of time that occurred fairly early on in the evolution of the universe.

    I'm being a bit oblique and incomplete with my answer because this is homework. Understanding this is critical to understanding this big bang theory.
     
  4. Nov 14, 2013 #3
    Alright that clears things up enough.
     
  5. Nov 14, 2013 #4
    If it's to much would the answer then just be the current age of the universe.
     
  6. Nov 14, 2013 #5

    D H

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    No, that is not correct.
     
  7. Nov 14, 2013 #6

    phinds

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    Not quite. Look up "surface of last scattering"
     
  8. Nov 14, 2013 #7
    K got it thanks guys.
     
  9. Nov 15, 2013 #8

    Chalnoth

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    The CMB was emitted when our universe was about 300,000 years old*. That's about the time when it transitioned from an opaque plasma to a transparent gas.

    Regardless of the time we're looking, we see light that was emitted during that single event that happened everywhere. The light we see currently was emitted from matter that was, at the time, about 42 million light years away. In the future, we will see light from that same event that was emitted further away, and thus has taken longer to reach us.

    * Bear in mind that this event did not happen instantly: it took a good amount of time for the universe to go from completely opaque to completely transparent. This has the effect of making our image of the CMB a bit blurry.
     
  10. Dec 5, 2013 #9
    sir if previous universe has same law as us than can we know all the thigs in the universe?
     
  11. Dec 5, 2013 #10

    phinds

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    As far as we know, there WAS no "previous universe" so your question is pointless, but even if there were, no we would not be able to know "all the things in the universe".

    By the way, you should not hijack a thread. If you have a question that is not related to the thread, start a NEW thread with your question.
     
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