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Pre-big bang?

  1. Nov 5, 2004 #1
    so today i was sitting in my philosophy class(dont worry this isnt really to do with philosophy) and we started talking about the universe and the "first creator." my teacher honestly believes that god is what made the universe move around and form into what it is now. but i want to proove her wrong. she understand that after the big bang theory everything was spread out because of the enormous amounts of force that followed the big bang but why was everything supposedly compacted together. like what pulled everything together in order for it to all be compacted into a gigantic ball of masses that one day exploded? how was everything pulled in together before the big bang?
    i read this article ( http://ssscott.tripod.com/BigBang.html ) but i cant really seem to find anything on the pre-big bang times. if there are any suggestions you can offer or any sites or sources that i can try tolook up and find please tell me. either post it here or msg it to me. i appreciate it. thanks guys and dolls! :blushing:
     
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  3. Nov 5, 2004 #2

    Garth

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    If the universe of space and time had a beginning then there is the question of First Cause.

    1. One person might say, "God did it, He/She made the universe" - this leads immediately to the next question, "Who made God?"

    2. Another person may say, "There is no God, the universe began as a random quantum fluctuation" - this leads immediately to the next question, "A random fluctuation in what? What/who made that?"

    3. A third person (Stephen Hawking) may say, "The only initial boundary condition is there is no boundary condition, the 'origin' is actually like the North Pole, if you continue going backwards in time (northwards) you eventually begin to come forwards (southwards) on the other side of the universe (world). No agent is required as a First cause as there wasn't a First Cause" - this leads immediately to the next question, "Does this idea make sense?!"

    4. A final person may say, "There is no 'beginning', there are an infinite number of universes, our universe was created out of, either the final crunch of a previous one or a black hole in another one" this leads immediately to the question, "Where are these other universes? Show me one!


    If you ask why was the universe so compacted in the first place, the answer is all we do know is that if you trace back the expanding universe in time you inevitably tend towards a singularity called the Big Bang, with zero volume, infinite density and temperature, at which the known laws of physics break down. - And how!

    In other words either of the above explanations may be equally considered 'scientific', there is no way of proving either one or disproving the other. You choose!

    Garth
     
  4. Nov 5, 2004 #3
    the universe is almost certainly one of an infinite number of bubbles in an ETERNAL sea of universes- a Multiverse-

    Either Existence exists or it does not- if it does not it never will becasue there would be absolute nothingness and no being-ness would ever exist- if Existence does exist [which it does!] then there ALWAYS has been some existence in which universes emerge throughout eternity

    an eternal cosmos could not have had a creator becasue it has always existed-

    therefore the idea of a Creator of all things is necissarily shown to be impossible
     
  5. Nov 5, 2004 #4
    As I understand it, inflation is an exponential expansion. And as exponentials go, you don't reach zero until you exponentiate to negative infinity. All this means is that creation came from extreme power from the infinite pass. And isn't that what is said about God: He has infinity power and exists from everlasting to everlasting?
     
  6. Nov 5, 2004 #5
    You shouldn't bring god into Physics. All Physicists can do is describe the Universe as we see it and theorise about the past and the future. If you want a 'who' or 'why' stick to Theology or Philosophy!

    As Garth put it above, there are various interpretations - You choose one that suits your personal philosophy!
     
  7. Nov 5, 2004 #6

    hellfire

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    There is one question which cannot be handled within physics: what is the origin of the existence, or why is there something at all and not nothing. Physics describes always causal transformations from one physical state to another and "nothing" is no state nor has any potentiality of being transformed. Therefore, one is faced with the necessity of postulating the necessity of existence and not the posibility of deducing it. If one remains within the realm of physics one is forced to avoid this question. If your teacher was considering this point you will not be able to prove your teacher wrong.

    On the other hand, if your teacher is arguing that starting from a given physical state, god acted to create the big-bang, then your teacher can be proven to be wrong (at least in principle). The physics to prove your teacher wrong and to describe these states and these causal transformations is still unknown today and you may only find some speculations (Hartle-Hawking model, Vilenkin-Linde model, models based on recent physics such as brane colissions, multiverses, etc.).
     
    Last edited: Nov 5, 2004
  8. Nov 5, 2004 #7

    marcus

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    I agree with lots of what you say---and how you lay out the various viewpoints---but i think this is incomplete.

    If you trace back using quantized General Relativity (any of several different alternatives) you dont get to a singularity.

    You continue tracing back though a moment of high (but not infinite) density and high (but not infinite) temperature and you keep on tracing back. As you trace back into the contracting phase, the density and the temperature get less. This takes care of the horizon problem, that Inflation Scenarios were invented to solve.

    If you use 1915 General Relativity as your model, to trace back with, then you do get to a singularity. But this is not inevitable because one is not forced to use 1915 Gen Rel. The fact that Gen Rel has singularities is widely believed to indicate that the theory is broken and people have been working for decades to fix the theory expecting that this would eliminate the singularities. It appears they now have a workable quantization, with a good classical limit, and that it has, as expected, fixed the "Big Bang" singularity. It is your choice how seriously to take the growing number of papers about this. I will get some references in case anyone wants to sample them.

    What you get when you trace back in time depends on the model used to trace back with. it is no longer inevitable that one should use classical 1915 Gen Rel, so it is no longer inevitable that one gets to a singularity and has to stop tracing back.

    A nice thing is that Loop cosmology has a good classical limit. It only disagrees for the first 10-40 second of the expansion or so, after that it converges to classical or semiclassical behavior. So the quantized version only differs right around the big bang, which is where it needs to be different in order to eliminate the singularity and let you continue tracing back into the contraction phase.

    Ashtekar and Bojowald have both discussed this convergence to the classical limit in various papers. there is, by now, a long list of papers by a lot of different researchers.

    Your main point, Garth, is something else----physics is not about why/who.
    I agree with that main point.
    This business about the singularity is different. I contend that one does not inevitably encounter it.

    If a person believes in Creator then there is no more reason for that Creator to have been around at the beginning of the observed expansion (at the socalled "Bang") than for Him to have been on hand in 1914 at the beginning of the First World War or for the first broadcast of "I Love Lucy". Theologically speaking, the classical ex-"Bang" is just another moment in history, as far as anyone knows.
    The physics laws that apply to that moment should, as you indicated, be fascinating to discover, if we are even able to discover them! Certainly present laws do not cover those extreme conditions.

    It is my feeling that the "Big Bang" should be scrubbed clean of any special theological interest so that one can study it dispassionately as one would anything else. More people are calling it the "Bounce" these days, which is probably more descriptive and less spiritually pornographic.
     
    Last edited: Nov 5, 2004
  9. Nov 5, 2004 #8

    Garth

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    I actually said "inevitably tend towards a singularity". I shall be happy with quantized General Relativity theories when they become more testable and 'hone' down to a unique experimentally/observationally verified theory. Until then just wait and you will see a tide of fashion ebb and flow around the present alternatives.
    I agree that GR is 'broken', but for other reasons!

    Garth
     
  10. Nov 5, 2004 #9

    marcus

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    good point,
    I was not as alert to what you were actually saying
    as I should have been

    GR is still the dominant model and tracing back in time
    does lead to the singularity which is present in GR

    and the quantized (LQC) version has so far not been proven better
    AFAIK it is only consistent
    your guess is as good as mine as to when some quantized version
    of the big bang will actually be subjected to experimental test
    and how that will turn out
    and the LQC version could be proven false and some entirely different quantized version of GR might then prevail----the tides of turbulent fashion that you mention.

    I gather you expect that eventually some quantized theory will prevail which will eliminate the singularity and let one trace time back past the beginning of expansion. I shall be happy also when that happens.
     
    Last edited: Nov 5, 2004
  11. Nov 5, 2004 #10

    hellfire

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    If time can be extended back or behind the big-bang, then, where should time begin? Or do this models claim that time has no beginning? But if time has no beginning, or lets say, if one can extend the causal chain back to infinity, one is faced with the problem of how handle the infinite chain of states: for any given state prior to present, one can always find a state preceding it, and, assuming a finite causal "speed" from one state to another, the question arises then how present came into being and how it is actually possible.

    To me it seams that cosmology is forced to find a theory in which causality as well as time arise or emerge from an acausal and atemporal state and some laws acting on it, may be some law of randomness leading to a fluctuation on this initial state. Time would have no meaning before this state and no other state could have been previous. In some sense this is or was one of the beautiful ideas behind the big-bang model. Some other models based on recent physics, at least the one with the colission of branes (although I do only know the models from some "high level" press articles), extend the causal chain back behind the big-bang. This leads me to think that they cannot be based on fundamental theories.
     
  12. Nov 5, 2004 #11

    Chronos

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    It is futile, if not pointless to pose a question such as 'what came before time?' and expect a scientific explanation. There is, however, an obvious answer - timelessness. Of course all known laws of physics break down in such a state. There is no causality without time and such a state is, by definition, chaotic. You can no more predict what might emerge from such a state than you can establish a causal link from what emerges to the state that preceeded its emergence.

    Proclaiming the universe to be infinite is not an answer, it is evasion. Obviously the universe is not infinite in both size and age [re: Olbers Paradox]. While the jury is still out as to whether the universe is spatially infinite, the evidence is pretty compelling it is not infinitely old. When we look out at great distances, we see a universe that looks much different than the one nearby. It is filled with exotic objects and structures nowhere to be found around our neighborhood, but, remarkably similar to predictions of what a younger version of the universe should look like. Furthermore, in a universe infinitely old, where did all the hydrogen, etc, come from that fuels the stars we see today? How can you have an infinitely old universe that still has stars forming and burning without steady-state creation of new fuel? Now you are right back where you started. Who/what/where is all that new fuel coming from?

    There is no escape from the creation issue, of something from nothing [at least nothing comprehensible to us]. You either accept that everything sprang from nothing a long, long time ago or that it has done so a little bit at a time for eternity.
     
    Last edited: Nov 5, 2004
  13. Nov 5, 2004 #12
    i think theres a theory in M theory that says we are on a giant brane, and that in a multiverse, two of these branes (one of them being ours) crash together over and over, the energy from the crash is the big bang. thats a pretty out there theory imo though lol. i've also heard it been said, and was stated above by Chronos, that it is pointless to think about the universe before the big bang because there was no time, and as chronos said, no causality.
     
  14. Nov 5, 2004 #13
    so basically no one knows the direct cause of the objects and everything in space compacting into one tight space and then exploding?

    no one knows what was before the big bang? well i guess we wouldn't. its logical to assume we wouldn't....with those kind of temperatures any evidence of anything would just be incinerated(sp?) i guess :rolleyes:
     
  15. Nov 5, 2004 #14
    Marcus is quite right, why we should use 1915 general theory of relativity. We do not know exactly what lies beyond the domain of GTR, but we are sure GTR must break somehow, because it predicts singularities. It is not difficult to guess that at the fundamental level nature of the universe must be quantum not classical. Much has been said about the LQG, string theories and quantum gravity, and these all theories avoid singularities. Just like singularities in QED were avoided by the use of renormalization, same thing could be done for the big bang also (I do not know how !). As far as time is concerned, I think time exists because we exist and we can feel the changes taking place in our environment. So the question of the birth of the time is basically the question of our existance. Time exists only there, where we can reach by any means. For example there is no way to communicate beyond our hubble volume, so I do not think there is any meaning of time in that region. In case if we assume that the big bang did happen then it is fair to say that there was no space and time before the big bang. However, we can not see the big-bang (LIGO,LISA may help to see it through the gravity waves) so in place of big-bang being the birth time of time that point should be considered as the birth time of time from which we starts to observe the universe (some very large redshift). Let me again make it clear that time is more to do with our consciousness than the physical universe.
    cosmoboy
     
    Last edited: Nov 6, 2004
  16. Nov 6, 2004 #15

    Chronos

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    Apologies for editing your reply. I thought it was important to cut to the chase. Two people who have a deep understanding and appreciation for the issues you raise: Marcus and Nereid. Marcus has deep insights and knowledge. Nereid has a way with words that makes it understandable to the rest of us [not that Marcus does not, but Nereid explains things in a way I find more appealing]. I just take what I can from them and try to make it understandable to me. I have learned much from both of them. Let me say this, as well. You are right, consciousness does obscure the issue. Unfortunately, it is the only tool at our disposal.
     
  17. Nov 6, 2004 #16
    I do not understand this problem of handeling a chain of infinite states,
    for this there are physical laws. Once causility is there then for a given past one can find a present with the help of physical laws.

    Could you please make it precise that what are the motivations for cosmolgy to find a theory in which time arise or emerge from an acausal and atemporal state. I understand this is what the big-bang model does.
     
  18. Nov 6, 2004 #17

    hellfire

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    I am not really sure, but my impression is that it is not physically possible to have an infinite time (also I think it is not possible to have an infinite space). Strictly speaking it seams to me that infinite is neither a physical time interval nor a physical distance: if you substract any time interval to the infinite past, an infinite past still remains. For every time instant in past, you can always define a previous one, and, any time interval past between this point and present can be substracted without changing the fact that it existed an infinite chain of events. If causality works "step by step" then it seams to me that this cannot lead to any definite state in present. This is the reason I think a theory has to be found in which time and causality arise from an atemporal and acausal state. I might be wrong.
     
  19. Nov 6, 2004 #18
    As I understand, infinite is a relative concept. It is true that absolute infinite in not a physical physical thing. Some thing which picks such a large value that it looses its information and can be defined as infinity. Although there are observational evidencies (OLBER'S PARADOX) that the universe was not been here in the infinte past, even then this question remain unanswered that why big-bang happed when it happened not today, finally it leads us to the anthropic principle.
     
  20. Nov 6, 2004 #19

    Chronos

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    Hellfire, for the same reasons you just stated, I agree. There is no way I can even imagine to escape any other conclusion. Footnote: The BB model does not attempt to explain what happened before time began, just what might have happened a planck moment, or two, afterwards.
     
    Last edited: Nov 6, 2004
  21. Nov 6, 2004 #20

    marcus

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    Hi hellfire, thanks for the thoughtful reply. I will make my response brief because I actually cannot comment on the philosophical questions you raise and i dont want to interrupt the interesting ongoing discussion you are having with Garth, Chronos, Cosmoboy, and others.
    All I can say is that I see signs of an increasingly informed agreement (among a small group of experts I respect) that the Loop cosmology model consistently extends the causal chain back into a contraction phase prior to the "bounce" event---and provides both a clear description of the bounce and an explanation for the subsequent inflation that does not require fine-tuning or the introduction of extra stuff "by hand".

    This does not address any of the philosophical issues---it just says that the beginning of the current expansion phase is not philosophically special. It certainly exhibits extreme and highly unusual conditions. Time may, at that junction, have been progressing in tiny planck-size jumps----not approximable by a steady-running clock, indeed I suspect that no known clock could have existed apart from the process of contraction and expansion itself (which may have been occurring, as I mentioned, in tiny jumps). But though it was an unusual moment, when physical conditions were extreme, it does not seem permanently out of reach of study. Conditions prior to that moment may have left imprints which we will observe and which will eventually support inference about the prior contraction.
     
    Last edited: Nov 6, 2004
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