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Universe started from a cosmic singularity

  1. Nov 13, 2008 #1
    It is a widely accepted theory that the universe started from a cosmic singularity and eventually through many years and processes gave us what we have today. But here's one question I ponder: how did the singularity get there in the first place? We know what the singularity caused, but what caused the singularity? Can something come from essentially nothing? I have been doing much reading lately, but am no expert on cosmology or physics. I am just curious about which physics or mathematical premise can explain this?? Thanks.
     
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  3. Nov 13, 2008 #2

    marcus

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    Re: Singularity?

    What is a singularity? Do singularities actually exist in nature? Do you have any online source where a qualified scientist says that the universe started from a singularity?

    I don't believe that this is actually a known fact, Cyhan. My understanding is that a singularity is a breakdown in a man-made theory. A place where a given mathematical model fails to compute. That is, it depends on what model you are using and does not necessarily exist in nature. One can use the breakdown point of a theory as a landmark or time-marker, however.

    General Relativity gives us a classical math model of the universe called the Friedmann model (or by other names with Friedmann). This classical model breaks down at a certain point as you use it to work back. That breakdown point (call it t=0 if you like) is a good time-marker that people use a lot in discussing early universe stuff.

    But there are other models that fit the data equally well (so far) and which don't break down. They run smoothly back to before t=0. In future we may, by making precise tests using more data, be able to eliminate some of these models and narrow down the possibilities. However for now we have no scientific reason to believe that the universe began at a point 13.7 billion years ago. Some models continue back further into the past.

    Also there is no conclusive evidence that the state of the universe at the beginning of its current expansion was small. I doubt that any reputable scientist would claim that as a known fact. That state is generally assumed to be very dense, but not necessarily infinitely dense. And simply because it is very dense does not mean it has to be small.

    So you may be laboring under some misconceptions about what the professional literature on cosmology actually says (as opposed to popular journalistic accounts.) Please tell us your sources so we can see where you get your ideas from.

    I have some links to better-than-average popular accounts in my signature at the bottom of the post----if you wish, try the princeton.edu link and the einstein-online link. If you want links to professional research papers, ask.
     
    Last edited: Nov 13, 2008
  4. Nov 13, 2008 #3

    marcus

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    Re: Singularity?

    If the scientific community does not accept it, if it is only uninformed members of the public who accept it, then do we have to worry about it? My point is, you have no reason to believe there ever was such a thing as a cosmic singularity in nature, so the question of "how did it get there?" is vacuous. The short answer is "probably it didn't".

    Have a look at the page called "A Tale of Two Big Bangs" at einstein-online. This may help clear up the problem. Here's the link:
    http://www.einstein-online.info/en/spotlights/big_bangs/index.html

    Sample quote:
    "...Whether or not there really was a big bang singularity is a totally different question. Most cosmologists would be very surprised if it turned out that our universe really did have an infinitely dense, infinitely hot, infinitely curved beginning. Commonly, the fact that a model predicts infinite values for some physical quantity indicates that the model is too simple and fails to include some crucial aspect of the real world. In fact, we already know what the usual cosmological models fail to include: At ultra-high densities,...."

    Check it out. Easy to read and may clear up a lot for you!
     
    Last edited: Nov 13, 2008
  5. Nov 13, 2008 #4

    Chronos

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    Re: Singularity?

    An analogous situation in science arose a couple centuries ago. It was called the ultra violet catastrophe. That one was not easily solved either.
     
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