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Big Bang Question

  1. May 5, 2008 #1
    From my understanding, people have taken a picture of the big bang(or microwaves), and they did it by pointing whatever they took the picture with X number of light years(i forgot the the real distance). But my question was did they take a the picture from outside(like how they take pictures of stars, galaxy's, etc. or was it like taking a number of pictures from inside, like as if u were in a ball taking pictures of the walls.

    i understand that that was a bit confusing so if i can clarify please ask. But please answer thx:)
  2. jcsd
  3. May 6, 2008 #2


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    The later, i.e. viewing the Cosmic Microwave Background (CMB) is like taking a picture of 'the walls' of a ball from the inside. Very perceptive of you to realise this possibility!

    The reason for this is that contrary to what is often supposed, the Big Bang was not like an explosion that happened at some point but rather happened everywhere, so everything in the Universe is moving away from everything else. If you look far enough back in time in any direction you will see what the universe was like shortly after the Big Bang in that direction, therefore all around us if we look for the right signal we see the CMB.
  4. May 6, 2008 #3
    I dig what wallace is saying, but i'd like to add a little.

    The big bang is something that happened at a point... but more importantly you must realize that at that time - that point was everywhere.
    When you look far away, you're looking back in time; back in time (13.7ish billion years), there was very little spacial extent - so its been, kind-of, stretched out over all the sky.
  5. May 6, 2008 #4
    The Big Bang cosmological model actually predicted the existence of the microwave background radiation and its temperature over 50 years ago

    It also predicted that this radiation should NOT be uniform and actually reflect the fine detail and density fluctutions enherent in what we see today in the universe.

    Thats what was so frustrating for researchers - they knew what to look for and where and at what temperature BUT didnt have the instrument sensitivity to measure the detail. Eventually the COBE and the WMAP sattelites revealed what was there all along and gave the BIG BANG model a massive tick of approval.
  6. May 17, 2008 #5
    So the fluctuations in CMB come from quantum fluctuations amplified by inflation, right? Is inflation assumed to be part of BB model? What made inflation happen?
  7. May 18, 2008 #6


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    Inflation solves the big bang "problems", and so most cosmologists believe in it. However, whether it is included in the phrase "big bang theory" will depend upon who you talk to.
    We don't know. As I said in another thread (that you are participating in?) there are many different models of inflation, but what we really want is one with some motivation from elsewhere, say particle physics. We currently don't have such a model.
  8. May 18, 2008 #7
    " So the fluctuations in CMB come from quantum fluctuations amplified by inflation, right?


    Cristo, are you sure about this? (I am not).

    EDIT: sorry, I mean, were they really quantum fluctuations? Do the casually disconnected CMB anistrophies we see today actually correspond to a tiny space that was once only separated by ~1fm?
    Last edited: May 18, 2008
  9. May 18, 2008 #8


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    Cristo is correct, at least that is the current leading theory, which is about at 'correct' as you can be when it comes to science.
  10. May 18, 2008 #9
    okay, just making sure. That's helluva lot of expansion, in a very short space of time:)
  11. May 18, 2008 #10
    Inflationary Numbers

    Okay, so this prompts the question, "How big is a helluvalot?" If you go to this web site,


    there is a intro guide to inflation by John Gribbin. Current theory (twelve years ago) says:

    Inflation is a general term for models of the very early Universe which involve a short period of extremely rapid (exponential) expansion, blowing the size of what is now the observable Universe up from a region far smaller than a proton to about the size of a grapefruit (or even bigger) in a small fraction of a second.

    Caveats: Gribbon's page hasn't been updated for 12 years, so whatever we've learned since 1996 isn't there. But Gribbon writes very clearly, I will be spending some time perusing his material.
    Last edited by a moderator: May 19, 2008
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