Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Big bang , physical constants , possibilities

  1. Dec 15, 2013 #1
    Hello , so the question is basically like that , I did some thinking about evolution and so I came to this question.

    Now the universe today with it's proton size and mass and particle charges , gravitational constant and all other things we know and yet don't know about , seems kinda precise and evolved , so here is the thing (according to our best understanding) the universe came into existance in an event dubbed the big bang, now before that very moment no space-time no mass and no physical laws existed, no fields as we know them no nothing, and now out of nothing the universe is born , yes way different than we know it these days , much hotter much denser and other stuff being different yet still it was " born" so to speak with a given set of rules for that moment , so these rules must have come together with the birth itself , otherwise how would the universe ,as it was,known to evolve further second by second ? I assume it had to follow some physical laws , some constants that it could fall into and so on and on until the present day.

    To not make this so long and phylosophical I will try to narrow it down to a few quesions.

    a) If we say taht the current state of the universe with all the current constants and laws is B , then many billions of years ago , while the universe was still in it's early stages, it had to be A which as time passed settled (evolved) down to the current state B.
    Now even though back in the day the universe was in a state " A" that still is a given definite state of something with some fixed rules and possibillities , and those arose together with the universe , so that begs the question how could those rules evolve right on the spot?

    In biology we are used to say that a given organism may and does evolve over a given period of time and it can happily do so because it has the environment around it and many things present for doing so , but the very fundament the very basic laws which govern the universe itself came together with the universe, so how did they assembled themselves right on the spot?

    b) Did the universe in the moment or before the moment of the big bang (if we can even talk about before the big bang) had some degrees of freedom in terms of states into which it could fall into , I mean like given the same event what are the chances the physical laws could have been different back then so they would evolved to different ones at the current situation also.
    I guess this last question is kinda off because we can neevr say that because we operate from a given universe with given laws and so we only have this framework.


    P.S. If somebody reading this gets an angry feeling of me trying to push a set of beliefs or opinions of some religious or any other kind of thoughts , be assured this is just my own naive interest and doubt to know , so if you can please help with a healthy open discussion.
    Thank you:)
     
  2. jcsd
  3. Dec 15, 2013 #2

    Drakkith

    User Avatar

    Staff: Mentor

    All I can say is that the origin of the universe is unknown. It may have come from nothing or it may not have. Perhaps it has always existed.
     
  4. Dec 15, 2013 #3
    All you're really doing here is saying things that may or may not be true. Assigning a universe a "state" A or B is really not scientific unless you have evidence to support this. These statements are just philosophical contemplation. I think this forum is better suited to well-defined questions about things we know (or don't know) rather than wishy washy conjecture.


    Your understanding of the big bang theory is not correct. Nowhere is it maintained that it was the birth of the universe, just that stuff used to be much hotter and denser than it currently is. There is a lot of evidence of the latter, and none of the former, so grouping them both into a single theory just creates confusion.
     
  5. Dec 15, 2013 #4
    Ok I agree that there is no actual physical evidence or even physical speculation as of earlier than the so called " Planck Epoch"

    By state B and state A I was just reffering to the fact that the universe back then used to be (not entirely) but different than today in terms of it's density , expansion and other things , Im not saying in any way that these states don't logically follow or are just one big state which continues to evolve.As it seems so.

    I do believe the question is phylosophical just because we don't have access or don't know yet the things and facts about this period of the universe.

    P.S. this I believe is just as much speculation as that of many known people like Hawking , dawkins and others because atleast in the popular media and in their interviews and books they too assert definite scenarios and then build their opinion on them.I'm not saying that they say that these scenarios are a pure fact like before the big bang nothingness and others but they do talk about them.
     
  6. Dec 15, 2013 #5

    BruceW

    User Avatar
    Homework Helper

    I'm going to avoid anything philosophical. In the very early universe, yes it was so hot and dense that all our known laws break down. This is because we don't have a quantum theory of gravity. And so, our universe was initially in that super-hot 'quantum foam' as it is sometimes called. And when it cooled out of that foam, it got the laws that we know about. So can we say anything about the foam that would explain what possible laws could have emerged, once the universe came out of the foam? I don't think so. Not without a quantum theory of gravity.

    Slightly related, is chaotic inflationary theory, that Andrei Linde talks about. In this model of the universe, there are continually new parts of the universe, being created out of the foam (or being created from regions with energy close to the Planck density, I'm not sure). anyway, in this model, it is possible that the universe has no big bang as such. And a possible reason for why our laws are the way they are is because we are in a region that just happened to fall out of the foam with the laws that make life a possibility. since in each region that falls out of the foam, presumably, the laws that we know about will take on a different value. This is still quite speculative, and I don't know much of the mathematics of it, so I can't really say much about it, but it's pretty interesting.

    But anyway, if we ever do get a quantum theory of gravity, or something similar, then our new laws will be different. They wold hopefully be 'better' in the sense that there are less laws, and explain more different phenomena. But still, I doubt we will ever get to the point where we have completely described the universe as one unified principle. It seems likely there will always be more problems where our theories don't quite match observation, and we must make adjustments to the theory, or introduce unexplained parameters. Even currently, our description of the universe that is below the Planck energy is still very incomplete.
     
  7. Dec 15, 2013 #6
    Ok , I guess the question then is , out of what the physical laws are " born" ?

    Do they exist before something happens ,like the universe cools down and expands, and determine what can happen and what cannot and if it can then do a certain degree , or are the laws that govern each new era of matter, created on the spot together with the process starting itself, like the one from the hot dense foam you were talking about which later settled down to a more "evolved" universe?

    If the first is true then that basically means that no matter how many times one would recreate the start of the universe he would get the same or a few (out of possible many) universes , if the second one is true then we can get pretty much anything out of a primordial universe.

    Now I dont intend this as some kind of speculation or self invented theory , it's rather a question about your opinion to which is the most likely answer given the current understanding that we have obtained through observation?.
     
  8. Dec 15, 2013 #7

    BruceW

    User Avatar
    Homework Helper

    I'm not 100% sure what you mean, so I'll give an example that I think might help. OK, in the Higgs mechanism, at very high temperatures, the universe exists in a state of symmetry. In this state, electromagnetism and the weak force are both the same thing. But, when the universe cools down, the universe spontaneously drops into a specific vacuum state which breaks the symmetry. You can effectively say that the laws of the universe have changed, since now electromagnetism and the weak force are two separate things. And also, the vacuum field has taken on some specific value which is completely arbitrary. The 'true' laws of our universe don't tell us what that value is, because the true laws are symmetric, but the universe had to drop down into some specific value, so it chose some arbitrary value. There were many possible values that it could have dropped down into.

    And about quantum gravity, they are not even close to such a theory (I think). But I would guess there would be a similar idea there. i.e. our current equations describe gravity and quantum as separate things, but if we had a quantum theory of gravity, then we would have equations uniting the two.
     
  9. Dec 15, 2013 #8
    While the universe cooled and dropped down so to speak could electromagnetism and the weak force not turn into seperate things ? That is what I mean.
     
  10. Dec 15, 2013 #9

    Drakkith

    User Avatar

    Staff: Mentor

    To answer this I'd say we need to recreate the conditions where the EM and Weak forces are united. Wiki says the energy range is above 100 GeV, which is well within reach of modern particle colliders. Since the particles we collide together come out of the collision acting normally, I'd say that the two forces must split at lower energies.
     
  11. Dec 15, 2013 #10

    BruceW

    User Avatar
    Homework Helper

    not in the current theory, I don't think so. But yeah, good point, so the guy Andrei Linde is saying that from a (very) hot state with energy density above the Planck energy, when the universe cools down from that, electromagnetism and the weak force could have turned out differently, for example, the masses of the particles could have turned out differently. But that is still mostly speculation I think. Also, it is only useful in the chaotic inflation scenario. And that is not the most accepted model of the universe, so we shouldn't really be talking about it here on physicsforums.

    Anyway, in the most accepted theory (with energy density less than the Planck energy), for the electroweak theory, the Higgs field contains the information about how the electromagnetic and weak forces will work once the universe has cooled down, and the two forces become separate. For example, the Higgs field contains the information about the masses of the various particles. So really, there is only one possible way that electromagnetism and the weak force could have turned out. There is a certain amount of arbitrary choice as to which vacuum state the universe settles down in. But, these different vacuum states are essentially the same. Our universe would still seem the same in any of these states, but it is important that these states are not the same, because that is the symmetry breaking which brings about the electromagnetic and weak forces that we experience today.
     
  12. Dec 15, 2013 #11
    thansk for the input drakkith , okay so assuming if this is the way you just said it kinda looks like the universe even though still was at a previous state (at that time) it was predetermined by some physical rules ,that may or may not have came into existance together with the universe ,to evolve into these states.

    Now please don't take this as speculation , I'm just trying to follow the logic (if there is one).
    My logic goes like this - if something was in a state A at some time , like the hot dense universe soon after big bang then that state was with some physical laws and constants which came together with that state or explained that state or just governed the universe at the time (choose which you like best), Now given some set of rules , the universe cannot evolve later on into something chaotic or totally unrelated to the previous state and set of rules would you agree on this one?

    Edited , I didn't see you were posting also Bruce, so basically it would be fair to assume that the universe to be logic must be somehow like a tape that can be (if it would be possible) rewind back to some point and then if played again from that place do exactly what it did the time before ? Because the laws and rules wouldn't have changed so as long as the " info " is the same the playback should be also right?

    And then comes the question which I meant from the very beginning , if we would to rewind to the very start , no matter how exact years ago but the very moment (assuming the universe really did came into existance from nothing) then how would we be able to explain the reason and the way some laws which seem to work on the spot came into existance just like that , even with the proposed theory of Quantum gravity and all other still yet to come stuff?
    I mean no matter how precisely we could explain all the phenomenon around us both present and past , I guess it still would not answer the question , how come it assembled itself in a working manner.
     
    Last edited: Dec 15, 2013
  13. Dec 15, 2013 #12

    BruceW

    User Avatar
    Homework Helper

    more or less, I think so, yes, In the case of symmetry-breaking via the Higgs mechanism, the universe will generally jump down to a different vacuum state, but I don't think it affects the system. A good analogy is spontaneous magnetism in a ferromagnetic material where there is no external field. To begin with, the spins are in all different directions, then the spins will all start to align in one direction. So we have spontaneous symmetry breaking, since now there is one special direction. The particular direction that the spins align in doesn't matter, the physics is still the same. The important thing is that a direction is chosen, and that breaks the symmetry of the system.

    yeah, it doesn't matter if the universe started at a specific time, or if the universe has always existed. The problem is that we have unexplained parameters and physical laws that are not unified. This problem is ongoing. Maybe one day we will have the answer to every question, maybe we won't. We just have to keep going, and finding more unified theories and trying to reduce the number of unexplained parameters.
     
  14. Dec 16, 2013 #13
    Okay , nice answers can I ask one more question,

    Now if we assume one of the possibillities that the universe has always been here , then how would we explain the current universe coming from a very hot and dense (as far as we have " seen" ) state?
    I mean if it would have been always here then that would imply that after a certain point in space and time it somehow turned into a hot ultra dense singularity and then evolved to it's current state, why would it do so , because to the best of my knowledge our universe is expanding at an accelerating rate , is there any evidence or even doubt that it could somehow suddenly " turn around" and start to shrink until it becomes a singularity? Because that is how our universe started.

    Also , if the universe was as you say , always here then does't that raise the question of infinities?
    because as if the universe would have been always here that would imply a infinite amount of time but for that the universe would need an infinite amount of energy because we observe there is energy left in this universe just by looking at the em radiation coming from the sun , but if it would have been always here would it have enough enegy left to form a shining sun at all?
     
  15. Dec 16, 2013 #14

    Drakkith

    User Avatar

    Staff: Mentor

    We don't know. These are unanswered questions in cosmology.

    Of course. We observe that there is still usable energy left in the universe, so it must be true no matter what the previous states of the universe were. Note that we have only been able to observe a small part of the universe as a whole, in both space and time. We have no idea what will happen in the far future. If the cyclic model of the universe is accurate, then eventually the universe will collapse and eventually turn back into a universe similar to the one we see today. Evidence doesn't support this, but we cannot see the future. Or perhaps the truth is far stranger than what we've even imagined.
     
  16. Dec 16, 2013 #15
    " " Or perhaps the truth is far stranger than what we've even imagined. "

    Kinda feels this might be right :D
     
  17. Dec 17, 2013 #16
    I think the universe is cyclic; black holes pulling in not just matter but space-time itself then reeling in each other in the end and creating a new big bang singularity and regenerating itself over and over. Weather comes in cycles why not the universe? How did it begin? I think space and time are infinite. It didn't begin by our understanding of begining.
     
  18. Dec 17, 2013 #17

    phinds

    User Avatar
    Gold Member
    2016 Award

    This is unsupportable personal speculation and against the forum rules. Your number of posts indicate you have been here long enough to know that.
     
  19. Dec 18, 2013 #18

    Drakkith

    User Avatar

    Staff: Mentor

    This is not correct. Black holes do not behave like this.
     
  20. Dec 18, 2013 #19

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    It has been suggested the universe may, in the vastly distant future, be solely inhabited by super massive black holes. Due to Hawking radiation, the universe may then become devoid of matter after another few hundreds of trillions of years. That would result in a very strange initial condition - from which another big bang has been suggested as plausible.
     
  21. Dec 18, 2013 #20
    There are cyclic models of the universe that do not involve a recollapse, Examples include Penrose CCc, Baum/Frampton model, Higgs instability models and VSl based models.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook