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Why no time before the BB?

  1. Jul 16, 2015 #1
    Why is it said that time didn't exist before the BB and the creation of the universe? As I understand it, the BB is theorized to have come from a ball of something. This something had to have some kind of properties, events that occurred within whatever state it was in, and these events would have occupied time.
     
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  3. Jul 16, 2015 #2

    jedishrfu

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    Here's a quote from the wikipedia article on the BB that sums it up nicely:

    from the article:

    https://en.wikipedia.org/wiki/Big_Bang
     
    Last edited: Jul 16, 2015
  4. Jul 16, 2015 #3

    Chalnoth

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    The classical big bang is necessarily incorrect at the start. We have lots of different models that replace the mechanics that occurred very early-on to avoid the Big Bang Theory's problems at the earliest times. We still usually use the Big Bang Theory to point to a specific time and call that the start (sometimes that specific time is called the Big Bang). What happened before that specific time depends upon what model we use to replace the Big Bang Theory. There are some models where there is a beginning, but no time exists before that point. In other models, time extends infinitely far into the past, with the Big Bang just being one event along the way.
     
  5. Jul 16, 2015 #4

    Chronos

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    Devoid of energy, no physical processes transpired prior to the emergence of the universe [i.e., the classical BB], hence no measures of time [clocks] existed. We may therefore conclude time did not exist prior to the classical BB in any physically definable sense.
     
    Last edited: Jul 16, 2015
  6. Jul 16, 2015 #5
    You're saying you think there was no energy prior to the BB?
     
  7. Jul 16, 2015 #6

    phinds

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    The currently accepted theory of cosmology is that we don't know WHAT, if anything, existed prior to one Plank Time after the "t=0" time to which the math model extrapolates backwards. "Singularity" just means "the place where the math model breaks down and we don't know what was/is going on". The Big Bang Theory is a description of what happened from one Plank Time forward.
     
  8. Jul 16, 2015 #7

    Chronos

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    Allow me to add that phinds is entirely correct, the BB is a model that describes how the universe evolved after its origin. It does not attempt to explain the origin of the universe, or if it even has an origin. We are, however, fairly certain the universe is not infinitely old in the form in which it currently exists. We do not, for example, observe burnt out cinders of stars that 'died' of old age [aka black dwarfs] after exhausting their fuel supply. We also observe an inexplicable abundance of radioactive elements produced by massive stars that would otherwise have decayed to trace levels, or even beyond detectable limits, in a universe of infinite age. So the question remains open on the origin of the universe. Two major choices are available: One idea, that has gained new life over the past couple decades, is an eternal universe that periodically destroys itself and re emerges like a Phoenix from its own ashes. This is popular known as the cyclical, or bouncing model of the universe. The other model is origin via a quantum fluctuation whereby all the matter, energy, space and even time itself emerged from a primordial quantum fluctuation in the nothingness that preceeeded the BB. That is the model I was implying in my comment regarding no energy [or time] prior to the BB. This is also popularly known to as the universe from nothing model. It remains popular despite the obvious question - 'how does nothing fluctuate?' The answer to that query lies deeply buried in the recesses of quantum physics. It offends the sensibilities of practical souls who struggle with the concept of something from nothing. Irrespective of which class of models one may prefer, the question ultimately becomes, depending on your philosophical leanings - has the universe always existed in some respect or another and evolves eternally, or did it emerge from some fundamental creation event at some point in the remote past? If time is not an absolute and fundamental property of reality, it was meaningless before there was a universe.
     
  9. Jul 18, 2015 #8
    This seems true, but only if form includes scale. Before atomic structure became widely understood about 1900, I don't believe it did: A scaled-down model was considered to have the same "form" as the original it depicted, with "form" having been the equivalent of what we might be likelier to call "shape" nowadays. What the originator of this thread may want to bear in mind is that there ARE detectable limits: There is a size of object whose outlines could not be revealed visibly to us (OR "by us"), even if all the mass / energy of our universe could somehow be devoted exclusively to its magnification. Our entire universe would, likewise, remain totally and permanently undetectable to a surrounding universe larger than it by a factor sufficiently huge, although, within a certain fringe of detectability, I believe that phenomena would appear random, since, although their elements might generally be perceived, they might never be perceptible clearly enough to reveal their relations to each other.

    I'd be interested to know, from people more familiar than myself with quantum theory (-which would probably include at least half the participants in this forum) whether the "quantum tunneling from nothing" posited by Vilenkin (which does have some power of explaining why the so-called "initial" gob of matter and/or energy didn't collapse into a black hole) may simply appear possible as the result of this limitation.
     
    Last edited: Jul 18, 2015
  10. Jul 19, 2015 #9

    Chronos

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    That, i would say, is an interesting question, in which case one could argue we would not be here to pose that query. To that extent I would appeal to the weak anthropic principle.That solves the philosophic issues, the rest is left to science, imo.
     
  11. Jul 19, 2015 #10
    Sorry; I worded my inquiry a little carelessly. I didn't mean to imply that acceptance of the possibility that quantum tunneling from nothing may have occurred requires any leap of faith. I was just commenting that, as far as I've been able to tell, "nothing" means "probably closer to absolutely nothing than it is to the smallest currently observable unit of the quantity concerned", and kind of hoping that there might be some factor in the math involved that would take account of whatever that quantity might've been at the time of a conjecture. (Vilenkin himself has repeatedly compared his "quantum tunneling from nothing" with Hawking & Hartle's "wave function of the universe", which, as he doesn't hesitate to imply,would've allowed purely hypothetical beings to observe a distinction between space and time under conditions of lower energy density than are now generally considered to have prevailed in the inflationary epoch.)

    My guess is that there probably isn't any such factor, which has the interesting effect of leaving the historical context of fundamental theorizing essential in validating it. (This isn't the case for vastly less fundamental scientific observations: For instance, a weatherman seeing only a single flake of snow drift by, during the period between one observation and the next, is obligated to write "trace of snowfall" in the record, whereas, if he didn't see it, he'd write "snowfall zero", and anyone familiar with the record keeping would realize that a flake might nevertheless have landed at his post. To coin a phrase.)
     
  12. Jul 19, 2015 #11
    For Robert P who started this thread: The above question MIGHT seem to throw considerable doubt on a 'new beginning' or 'beginning from nothing'. But it's not necessarily as big an obstacle as you might think.

    On one hand it is believed via quantum mechanics the 'nothingness' of open, free space is in fact filled with vacuum energy which on balance is zero. From a general relativity [GR] perspective, if the universe we live in exactly balances negative gravitational energy with the positive mass energy, and it seems at least close to doing so, all we have now is a different state of 'nothing'...zero in total. Alas, GR does not yet have a single, firm uncontested view of the total energy in the universe.
     
  13. Jul 19, 2015 #12
    THAT's the problem with ANY "beginning" to everything....no matter (-no pun intended) how many particles of matter and energy there are, any interactions between them would, even if random only in appearance, sooner or later put them into gridlock, with a "stuck on dead center" effect that's familiar to students of steam and internal-combustion engines. That this hasn't happened yet requires a "specialness" familiar to psychiatrists studying "ideas of reference" in people suffering from schizophrenia.
     
  14. Jul 19, 2015 #13
    What is 'gridlock'?? Not stasis I hope.

    If I understand your post, that's not actually the case. Nature generally moves towards a state of maximum entropy which in the absence of gravity means, for example, a gas or photons released into a room distribute themselves rather evenly around the available space. That maximizes entropy and minimizes information. And the universe works in the same general direction. In the presence of strong gravity, clumping is the state of maximum entropy, hence stars,planets, black holes and galaxies, but few would describe any of that as 'gridlock'.
    Not even the vacuum state is in gridlock.
     
  15. Jul 19, 2015 #14
    No, sorry, I don't think I made my last post clear enough. I'm not saying that the universe is in gridlock; I'm saying that the fact that it's NOT in gridlock leaves it improbable that it had any absolute beginning. Relative "beginnings" (or relative "endings") seem plausible to me, as long as each such occurrence is on a scale different from the scale of the object concerned upon its previous ending. My post #10 in this thread was intended to show that I feel the terminology to be relative (i.e., dependent on its context), rather than absolute.

    I'm aware of the entropy problem, which is usually felt to apply even even to cyclical (or "bouncing") cosmologies, if there is a minimum size below which the temporally-reversed version of the hypothesized universes concerned cannot be extended. (I've heard that Steinhardt & Turok's "ekpyrotic" proposal of periodically colliding branes--membranes of the vibrating strings very often hypothesized as defining what had previously been seen as "elementary particles"--employs a special field to neutralize the fatal increase of entropy's density, but that seems a little too ad hoc for me.)

    What I can't understand is why there would BE any minimum scale, either of space or of time. I understand that, if there was, reliable calculations involving infinities would be easier to make, but for physicists to consequently wish that there was one is like bus drivers wishing for power steering--the wish was natural, but its connection to a larger reality is lacking, as far as I've been able to tell (-and, in the attempt to understand this mania, I've read entire books by Smolin and Bojowald).

    I'm NOT saying that reality is not divided into quanta: It probably IS, at least in all inhabited and habitable regions, and even in all regions accessible in principle. I AM saying that I haven't yet heard why the number of spatial scales, or the number of temporal scales, would have any limitation whatsoever, except "LOCALLY". In this connection, I guess I should add an assumption of mine that any difference in the set of spatial and temporal scales applicable in different regions would cause them to repel each other with extreme force and rapidity, although the only scientific basis for this assumption is the existence of some of Andrei Linde's older work, which hypothesized a universe inside a monopole. (The papers are pre-Web, and my math skills wouldn't justify harassing a librarian enough to get a hold of them.)

    Sorry for all the bold-facing; I'm just trying to get around the dullness of my convoluted writing (attempted verbal imitation of math, but not quite as concise, huh? Probably not as accurate, either, but that's why I'm posting it).
     
    Last edited: Jul 19, 2015
  16. Jul 21, 2015 #15
    "What I can't understand is why there would BE any minimum scale, either of space or of time.

    Quantum principles don't always match our classical logic. I was just watching a SUSSKIND video and apparently he likes to start most of his quantum lectures with such an explanation: Evolution did not require us to evolve quantum logic.

    Anyway, It seems we live in a quantum world. But that necessarily breaks down, or so it seems, at the Planck scale due to the uncertainty principle.

    I'd been looking for this description after not not having seen it for a long time:
    "Any photon energetic enough to precisely measure a Planck-sized object could actually create a particle of that dimension, but it would be massive enough to immediately become a black hole (a.k.a. Planck particle), thus completely distorting that region of space, and swallowing the photon. This is the most extreme example possible of the uncertainty principle, and explains why only a quantum gravity theory reconciling general relativity with quantum mechanics will allow us to understand the dynamics of space-time at this scale.

    https://en.wikipedia.org/wiki/Planck_scale


    More generally, the known laws of physics are not much help because they describe how things evolve in time not how time begins. They do not describe the big bang itself.
     
  17. Jul 22, 2015 #16
    Wow, that's terrific! I feel a little like I imagine Brian Greene may've felt, when he realized that galactic structures were the CMB 'writ large'! Given the obsession with an absolute beginning in physics (or at least in its popularizations, to which my mathematical ignorance often confines me), I'd always figured that the changes in scale I'd thought it might represent would've been dramatic, but even the possibility that some little upward kick in energy density even might have suddenly transformed an entire generation of steroidal photons (into very little more than hole-black space) was jaw-dropping! Especially since some googling inspired by your post about the possibility of a zero energy balance had, not an hour before, turned up

    https://www.sciencenews.org/article/arrow-time

    , which describes simulations of gravitational clumping being conducted (by a group led by Julian Barbour, no less). A distinct maximum in the clumping is apparently occurring with equal chances at either early or late times in each simulation, which is suggestive of dual arrows of time pointing in opposite directions. To a layman like myself, this seemed very similar to the dual-arrowed universe modeled by Aguirre & Gratton (and described somewhat favorably by Vilenkin at

    arXiv.org > hep-th > arXiv:1305.3836 ), except that the arrows in the AG scenario were thermodynamic rather than gravitational.

    The Barbour study may invalidate a lot of things about the relation between entropy and time, so that the statement answering the question, " No time before the big bang?", could turn out to be, "Time behind the BB."
     
  18. Jul 22, 2015 #17

    Chronos

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    I think that position relies on numerous unsupported assumptions. I am willing to concede entropy may be poorly defined by current science, but, so is gravity. I suspect a good theory of quantum gravity might resolve both issues. I am fond of the thermodynamic approach to both gravity and entropy, it appeals to my sense they must be fundamentally related.
     
  19. Jul 22, 2015 #18
    Having been a big fan of the dual arrows of time as formulated by Aguirre (who, when cornered by the Science News reporter, didn't seem to cotton to Barbour's approach), I am curious about a thermodynamic approach to gravity. Can you maybe provide a reference to an article or book, hopefully one that might paraphrase the main points of its QM and math with plain English?
     
    Last edited: Jul 22, 2015
  20. Jul 22, 2015 #19

    Chronos

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  21. Jul 28, 2015 #20

    ohwilleke

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    One possibility is that an antimatter dominated universe expands backward in time from the Big Bang in the same manner that our matter dominated universe expands forward in time from the Big Bang.

    In that scenario, the sole arrow of time in the universe would be entropy which flows from a peak at the Big Bang in opposite directions in time. Time basically would flow backward in the antimatter universe which fits with the conceptualization of antimatter, which flows naturally from the concept that a Feynman diagram can hold true for any rotation in space-time coordinates, that antimatter is basically ordinary matter moving backward in time. In this cosmology, causality is an emergent property of the universe, rather than a fundamental one. Forward in time operationally would mean "away from the Big Bang" and would only be well defined in systems complex enough for entropy to be well defined.

    Thus, it would be perfectly sensible in the case of entangled particles for information about how one entangled particle resolved when measured from an indeterminate state to travel back in time to the point of entanglement and then forward in time against on the path of the other entangled particle until it resolved from an indeterminate state in a correlated way without leaving the light cone, acting non-locally, or determining in advance at the time of entanglement how it would resolve from an indeterminate state.

    All of the laws of the Standard Model would apply identically at both t<0 and t>0 with the antimatter universe having particles that are CP flipped from our own. The Standard Model distinguishes through CP violation between forward in time and backward in time, but does not on its face obviously prefer one to the other. The two universes could evolve from the Big Bang differently (i.e. there wouldn't necessary be a parallel planet Earth in t<0, just a universe that evolves according to the laws of physics from the other side of the Big Bang according to the same rules making it extremely similar in a fine grained way, but not identical since there would be nothing to link events in the t<0 universe to events in the t>0 universe).

    The amount of matter-energy in any time-like slice of this universe would be the same, pursuant to the conservation of matter-energy.

    The aggregate baryon number and lepton number of our universe would be reversed in the part of the universe prior to t=0. The total baryon number in the universe over all time from negative infinity to positive infinity would be zero, as would the total lepton number of the universe. Nothing in this conception explains why the aggregate baryon number and aggregate lepton number of the universe ends up the way that it does; this would have to flow from unknown physics at Big Bang energy scales governing how pure energy condenses into particles, but could involve some scenario in which baryon number and lepton number arise from baryon number conserving pair production and from lepton number pair production that straddles t=0 (with all pairs produced exclusively on either side of t=0 quickly annihilating into energy in almost every case).

    Since this universe provides a natural explanation for matter-antimatter asymmetry and a finite B and L number for the universe without needing non-sphaleron B and L violating processes to give rise to the universe from a starting point of pure energy, B and L can be perfectly conserved and phenomena that merely conserve B-L such as Majorana fermions and supersymmetric violations of B or L separately are not needed and there is no neutrinoless double beta decay.

    If one wants to get really clever with the concept it can also be used to explain the "Bang" element of the Big Bang, with the energy that drives it all flowing from antimatter on our side of the Big Bang rushing back towards t=0, while ordinary matter on the other side of t=0 rushes forward in time, and matter-antimatter annihilation occurring in the region that is ill sorted between matter and antimatter (to a degree consistent with the uncertainty principle) as matter and antimatter try to sort themselves into the right universe an collide en route. All pair production that does not straddle t=0 contributes to the "Bang".

    Such a universe is finite with spatial dimensions identical to our own but with twice the extent in the time dimension. Philosophically, it assumes fate with free will and randomness merely being illusions (or perhaps more accurately, concepts that are only well defined from the perspective of an observer in a particular time slice that cease to have meaning in the case of a hypothetical but nonexistant "eye of God" observer). From the perspective of an "eye of God" observer, there is precisely one four dimensional universe that is like a painting always existing that only seems random from the perspective of an observer at a particular point within it who does not have knowledge of the whole. Time travel paradoxes would be prevented because there is only one consistent story of space-time - rather than many worlds or "the multiverse", there would be only one possible outcome of every event even though it would seem at the time to be perfectly random, "the monoverse"

    If the monoverse does not have a critical density necessary for the expansion of the universe to stop and start contracting instead (indeed, I'm not sure with entropy defined as it is in this universe if the laws of physics could ever permit a contraction), then the monoverse is ultimately infinite in time and space extent in every direction, even though there is a huge infinite region beyond the expanding universe's own "event horizon" in space-time at its frontier that is permanently inaccessible and effectively does not exist (which is fine because as mathematicians know, there can be different orders of infinity that are not necessarily equal in size to each other). The theory is agnostic on the question of what exists beyond its event horizon, but that event horizon boundary at its space-time frontier is far less arbitrary that the conventional Big Bang analysis with time and space starting from nothing. Instead, the Big Bang is conceptualized as basically the center of a four dimensional sphere that extends from that center in all directions to infinity, with the nothing beyond the spatial horizon only having nothing in it until enough time passes to cross that point. The speed of light boundary makes it theoretically impossible to leave the monoverse.

    This is conceptually different from a universe proposed by some theorists in which time always runs in the same direction and the universe expands, contracts to a "Big Bounce" and then expands again. Like the Big Bang cosmology, there is a point in time which is special and maybe even singular. But, unlike the Big Bang cosmology the other side of the Big Bang at t<0 exists, even if it may not be accessible because the Big Bang event forms an event horizon which cannot be crossed just like the event horizon of a black hole (unless space-time has non-local connections in which case wormholes from our universe to the antimatter universe and back could exist, at least at the Planck or fundamental particle scale).

    Using this framework, it would probably even be possible to figure out the energy scale and properties of a simple set of high energy physics rules consistent with the Standard Model that would produce the right baryon and lepton number and global charge neutrality of the universe from the known total amount of matter-energy in any time-like slice of the monoverse with sufficient rapidity (although the immense matter-energy density of the Big Bang era would make time seem to place much more slowly to observers in the first seconds of the universe).

    The charge neutrality part would be the trick and might end up linking B and L although not in a B-L conservation manner, because a single pair production crossing the t=0 boundary wouldn't naturally conserve charge. Then again, if the charge division in each pair production was random and we were talking about a number of pair productions equal to the aggregate B+aggregate L of the universe, the difference between perfect charge neutrality, and statistically average charge neutrality for a B+L number of binomial trials might be impossible to detect in practice since it would be so close to zero even if not exactly zero.

    None of this, of course, would have to contradict existing Big Bang cosmology at all. It would simply fill in some blank spots upon which existing Big Bang cosmology is silent in a manner that provides a plausible explanation of why things like matter-antimatter asymmetry exists in our universe. Inflation theories and lamdaCDM, for example, would be totally unaffected by this extension of the Big Bang cosmology.
     
    Last edited: Jul 28, 2015
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