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The Big Bang

  1. Oct 27, 2014 #1
    Hi guys.
    Newby here. And not all that educated physics wise. But have a question that you likely get all the time.
    Is there any theories pertaining to BEFORE the Big Bang? As to how this infinitely dense point came into being?
  2. jcsd
  3. Oct 27, 2014 #2


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    First, it was NOT an infinitely dense point. That is popularization nonsense that you see everywhere on TV but nowhere in physics books. The big bang is a theory that discusses the expansion of the universe from a hot dense state without ever saying what it was like at t=0 except that it was NOT a point. You may hear the term "singularity" but this does not mean point, it just means "place where the math models break down".

    Yes, there are theories about pre t=0 but they are not big bang theories and they have zero premedical evidence to back them up.
  4. Oct 27, 2014 #3
    I apologise. I am not highly educated in these matters. However I am infinitely curious. After reading the guidelines I am not sure if this is the best place for my questions, I am sure many of them are erroneous and have been gathered from Sri-fi rather than actual science.
    Please don't mistake me, I am well aware that it is fiction and the respective authors may or may not have any credible scientific background but a lot of the stuff in science fiction does have some roots in real science. I want help to see where the line between fiction and fact is.
    Thank you for the clarification on the the early universe, I was indeed mistaken. Could you explain the most popular theory ( if there is one) about how this hot dense state could come into being?
    I will stipulate I in no way wish to turn this back into a "it must have been God" discussion. I truly want a scientific answer if there is one.
    Whether there is evidence or not.
    Thanks again.
  5. Oct 27, 2014 #4


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    You might want to try this thread from the FAQ in the Cosmology section here:
    https://www.physicsforums.com/threads/where-did-the-big-bang-happen-would-that-be-the-center-of-the-universe.506991/ [Broken]

    Also, check out the list of "similar threads" at the bottom of this page, and try searching here for more on this topic.
    Last edited by a moderator: May 7, 2017
  6. Oct 27, 2014 #5


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    Hi megapyab,

    Have a look at this here section for a very basic primer:
    Follow the links for a more extended discussion. The "chaotic inflation" the link mentions is often refered to as eternal inflation. I believe there are also more cyclic cosmology models than just those mentioned there.
    A forum search using such keywords should net you extended, and perhaps more up-to-date discussion about these models.
  7. Oct 27, 2014 #6

    Doug Huffman

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    Watch Stanford University's Leonard Susskind and his wonderful lectures on YouTube. There are 165 to choose from and ranging from basic classical mechanics to cutting edge M-Theory and cosmology.
  8. Oct 27, 2014 #7
    It already is pretty blurry, but things get totally myopic prior to about 380,000 years after the Big Bang.

    So, everything before that epoch (the Epoch of Recombination) is pretty much a mystery and any theories are (at least at this stage) untestable. However, there are things we can do inside particle accelerators to recreate what we think conditions were close to T0, but these are just small pieces in a very large puzzle.

    Therein also lies the problem with theories prior to T0; they are untestable. Some theories have more potential than others, but if you can't test them they are little more than science fiction in their own way.

    For example, M-Theory is popular (and so far untestable), but while the math is most elegant, the problem with math is it can be made to support just about any claim you want.

    Bottom line is that there are still far more questions than answers.
  9. Oct 27, 2014 #8


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    That's no problem at all. It's one of the great things about this forum to dispel misconceptions, so just ask away. DO, however, start off with the assumption that if you saw it on TV or read it in sci-fic there's a good chance it's wrong, possibly VERY wrong. They get a lot of stuff right, but you never know which is which without looking at some actual science.
  10. Oct 28, 2014 #9


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    So are you suggesting that we have no empirical evidence supporting Big Bang Nucleosynthesis? Why are we wasting billions of dollars on satellite missions to study the temperature and polarization anisotropies in the cosmic microwave background if we won't be able to use this data to test theories of the early universe? Even though the universe was opaque prior to recombination doesn't mean that we cannot study physical processes prior to this time. That's a little myopic, no?
  11. Oct 28, 2014 #10

    Thanks for the reply. I am suggesting that going back beyond the epoch of Recombination is a much harder nut to crack empirically due to that opaqueness, but that does not mean we should quit trying. However, just how does one scientifically prove what happened behind the veil of Recombination? There is a difference between proof and theory, no matter how good the theoretical reasoning is.

    Big Bang Nucleosynthesis is a theory that is inferred by, among other things, work in colliders. Theoretically, everything ticks and ties with the Standard Model, but once again it is not something that is directly or empirically observed. We can't directly observe nucleosynthesis during the first few minutes of the birth of the universe, so we postulate that based on other indirect methods.

    As for the CMB, that data is only empirically available from the point where photon decoupling began, which is about the same point where Recombination occurred. At least that is my understanding of it and if you have something to add, feel free to correct or embellish.

    I don't find the expensive studies we are performing wasteful. There are a lot of things we don't know and we are still spending large sums of money to confirm Einstein's theories, which to date have proven resilient to all that poking and prodding, as expensive as it has been. It is all good science from my point of view.
  12. Oct 28, 2014 #11


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    First, it's important to recognize that science does not prove theories, it falsifies and corroborates them.

    The CMB photons that began to free stream after decoupling bore witness to the early universe prior to this time. The temperature and polarization anistropies that we observe today were imprinted on the CMB radiation prior to recombination. These imprints provide evidence of physical processes occurring prior to recombination. Is this direct evidence? Define direct evidence.

    You seem to be hung up on the fact that we cannot do science (or that it is somehow weakened) when it involves evidence of things past. This is a deep fallacy. Can we not test the theory of evolution because the fossils of interest might be hundreds of millions of years old?

    Science begins with a hypothesis, perhaps a prediction. Take the simplest inflationary universe models. These predict that the temperature anisotropies measured in the CMB today should be of a certain pattern. This is something we can go out and measure, and thereby place constraints on the inflation model space. How is this any different than doing a collider experiment?
  13. Oct 28, 2014 #12


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    Loren, you're painting the case of pre-recombination as special in its disconnect from direct observation, when such disconnect is ubiquitous in natural sciences. Everything that's beyond the direct reach of our human senses falls into that category.
  14. Oct 28, 2014 #13
    Good arguments.

    What I was trying to stress when Megapyab wrote, "I want help to see where the line between fiction and fact is...", was that there is no resolute point between critically focussed and fuzzy. It is more of a fuzzy line between them.

    This is where the definition for a proof differs from a theory, which there are good theories, weak theories, and incomplete theories. I guess you can make a case for false theories, too, but they all straddle a fairly wide spectrum.

    I wholeheartedly agree with you that we simply can not dwell in the realm of 'proofs only' and to do meaningful science we must work extensively in the domain of theories - which is that fuzzy zone between facts (proofs) and fiction.

    It seems I did not do a very good job of initially presenting my case and we spent a lot of time getting sidetracked, but that was my fault.
  15. Oct 28, 2014 #14


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    Loren, it is your belief that science EVER "proves" theories? As bapowel has already pointed out, that's just not the way it works. Science can DISprove a theory but anything that is subject to an absolute proof is not physics, it's either math or theology.
  16. Oct 28, 2014 #15
    I am not sure how we got here, but I think my answer to your question is that I believe in the scientific method, which never really arrives at a "proof", but it is sort of like an asymptote where a theory can sometimes be pretty darn close to a proof. Again, there is a broad range for theories from falsified to those with a very good foundation of supporting evidence.

    As far as theology goes, I don't think anything in theology is arguably provable, except, as my girlfriend likes to say, to oneself.
  17. Oct 28, 2014 #16


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    I agree w/ all of that, pretty much, except about "close to a proof". I DO understand, and agree, w/ what I think you mean, but in the case of physics proofs, it's "close but no cigar" or "a miss is as good as a mile", and other folksy sayings indicating that you either have it or you don't and in this case you don't.
  18. Oct 28, 2014 #17
    Well, there are established theories that are pretty close to a gold standard like Relativity, which is testable and so far has withstood the rigors of that testing pretty well.

    Then there are theories like M-Theory, which so far is untestable. It's a likable theory, but no where on the same footing as Relativity. Neither being a proof, but some theories may be close enough for a good whiff of that cigar. :)
  19. Oct 28, 2014 #18


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    And, again, I DO understand and agree w/ that, I'm just being dogmatic about "proof". Hey, we all like to do what we're good at and I'm good at being dogmatic, and I'm perfectly willing to do it whether I know what I'm talking about or not ! :p
  20. Oct 28, 2014 #19


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    The expression I have come to prefer is "a preponderance of evidence".

    eg. "There is a preponderance of evidence that the universe is billions of years old."

    BBT is not proven, it is simply the only serious model that explains what we see. It is enough to build more research and discoveries upon with the confidence that it will not likely crumble beneath us - though that's not to say it won't be shorn up and improved incrementally, as with all good science.

    No! Weren't you paying attention?

    You are simply very hot and densely curious!
  21. Oct 28, 2014 #20
    That gave me a good laugh! :)
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