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Alternative to the Big Bang

  1. Aug 17, 2010 #1
    hey all,

    i'm going to be doing a presentation for my astronomy module, and i was thinking that i should talk about the idea of the universe being in an eternal cycle of expansion and rebirth.

    i'll compare the expansion of a universe to a spring and harmonic motion. if the rate of the expansion is being reduced, then that may mean that there is a force which is decelerating this expansion. eventually the speed will be reduced to zero, from which point the bodies will then start moving in the opposite direction, with a negative acceleration. i believe that the "centre of the universe" may act as the point of equilibrium, meaning that the speed of the bodies will be at its peak.

    the issue which i can see is what would cause the bodies in the universe to slow down and contract? what mutual force is there to cause everything to decelerate in the first place? will it be something to do with the Energy and energy density? a friend of mine also mentioned that the expansion/contraction will not be in a perfect sphere, which i neglected in my thought process. now i've come to the conclusion that instead of one large collision, there are smaller collisions throughout the universe.

    this link will explain what i mean if i haven't made myself clear;

    http://www.princeton.edu/pr/pwb/02/0506/0506-cyclicuniverse.htm

    please point me out in the right directions if you have any opinions on this subject

    thanks :D
     
  2. jcsd
  3. Aug 18, 2010 #2
    I remember reading somewhere that the most probable shape for the universe is a donut. Actually I think there was a 1 million dollar prize to whoever figured it out, but the person who figured it out declined the prize. I can't remember many specifics on the whole situation though.

    As for what causes it to accelerate and decelerate? Who knows, maybe we we'll understand if we ever get interdimension travel (:P). Isn't that kind of like asking, why do quarks randomly disappear from existence then reappear a short time later? As far as we know, it's the fundamental nature of them. What governs that? We could never know.

    Also, I think I may have interpreted what you said wrong because you said "what would cause the bodies in the universe to slow down and contract". Is it not the fabric universe itself that will soon slow down and contract? Not the bodies?
     
  4. Aug 18, 2010 #3
    I would look into vacuum energy or dark energy for it’s speculated this energy is the cause of the universe's accelerated expansion and I believe inflation as well.

    Additionally, researching the latest cosmological constant may shed light on to why the universe is expanding and not contracting and when if ever it will collapse into the big crunch.

    Also in theory the Universe is Euclidian due to its isotropic uniformity and its shape(unlike a donut) should not violate elementary geometry( angels in a triangle add up to 180 degrees)
     
  5. Aug 18, 2010 #4

    cepheid

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    It sounds like you're talking about the so-called "big-bounce" scenario. For what level of schooling are you creating this presentation?

    The equations that govern the expansion are not those of a simple harmonic oscillator, although that's not a bad guess. I'm not sure what your math background is, but you might consider looking up the Friedmann equations in order to learn more. Very roughly speaking, these equations describe how the 'scale' of the universe evolves with time. One of the implications of the Friedman equations is that this evolution depends upon the different components that contribute to the energy density of the universe, such as matter, radiation, etc. The component that seems to be dominant at this point in time is something whose nature is not understood at all. It has simply come to be called, The Dark Energy. More on that below.

    That depends. The force that wants to slow down the expansion is just gravity. Therefore, the ultimate fate of the universe depends (partly) upon how much matter is present within it. This dependence is a direct result of General Relativity (which is where the Friedmann equations come from in the first place). It is simple to explain what the ultimate fates of universes without dark energy would be. There are three possibilities. If the density of matter in such a universe is less than some critical value, then that universe will continue to expand forever, and the expansion rate, although decreasing, will always be positive. If the density of matter happens to be exactly equal to the critical density, then that universe will also continue to expand forever and will once again be decelerating with its rate never quite reaching zero (but approaching it asymptotically). If the density of matter in the universe is greater than the critical value, then the expansion rate will decrease until it becomes zero, and then negative. In other words, the expansion will slow down, stop, and then reverse. The universe will begin to recollapse. This third possibility is essentially the same as the scenario you outlined, with one key difference. Without dark energy, there is no 'bouncing back.' Everything collapses down to a singularity and that's it. This is the so-called 'big crunch.'

    I should emphasize that all of these scenarios have been ruled out by observations, which strongly favour the presence of dark energy. The dark energy makes it a bit more complicated to sort out what the ultimate fate of the universe will be (as compared to the neatness of the three cases presented above). However, in all reasonable models that include dark energy, the universe will continue to expand forever, and the rate of that expansion just gets faster and faster (i.e. the expansion is accelerating).

    The universe has no centre and no edges. Please don't ask me to explain this. There are numerous discussion threads on this topic in the Cosmology sub-forum. In fact, this thread should probably be moved to the Cosmology section (since that's what it is about).

    Again, it's called...gravity.

    Yes. As I've alluded to above, General Relativity says that anything that has energy gravitates. That includes "mass-energy."

    Your final paragraph doesn't make much sense at all. What do you mean by the expansion "being in a sphere?" What collisions are you referring to? From what I can gather from this paragraph, you seem to be thinking of the "Big Bang" as an explosion of matter outwards from some "central point" in space, which is not correct at all. The big bang is a bit of a misnomer in that sense. Whatever it was, it happened everywhere in the universe, all at once. Rather than thinking of the expansion as being an expansion of matter outward through space (which is wrong), you might find it helpful to think of it as an expansion OF space itself. However, there is considerable controversy on these forums as to whether that's a good way to think about it, or whether it can be misleading (i.e. give the lay person wrong ideas about Cosmology). You have only to look at the numerous threads in the Cosmology section in which the merit of the so-called "balloon analogy" is debated in order to see what I mean.
     
    Last edited: Aug 18, 2010
  6. Aug 18, 2010 #5
    Also I forgot to add, isn't the moment it collapses and restarts a "big bang" in itself. It's not really an alternate to the big bang, they're the same thing, just different names... at least that would be the most rational conclusion
     
  7. Aug 18, 2010 #6
    I thought that this theory was already proven wrong--or so I heard in a lecture I attended at CU.

    Don't forget intelligent design as an alternative. The Big Bang is only a theory.
     
  8. Aug 18, 2010 #7
    The thing I don't understand with intelligent design, and I don't understand why people don't understand this... in all religious books it doesn't say any detailed specifics. You think if a designer was intelligent, he would be intelligent enough to set it up in a scientific way.

    I don't see what an intelligent designer has to do with it. Since with or without one, the "big bang" still could have happened, whether it was by nature, or by an intelligent designer. Which means discussing it here doesn't matter. Debating about dogma here is not allowed anyway.

    A lot of science is only theories, but we can see the radiation from the big bang. We know something of similar to the description of a big bang happened because we can see the early traces of it.
     
  9. Aug 18, 2010 #8
    I was just suggesting Intelligent Design as an alternative to the Universe is being Eternally Reborn thory. I'm not out to prove it (well at least not in this thread:biggrin:)

    The OP asked for my opinion on the subject, so...

    I gave it.
     
  10. Aug 18, 2010 #9
    I would like to interject with this question if I may : Just after the (A) Big Bang, super massive amounts are in extremely close proximity, right? If so, why wasn't all this mass immediately returned to a great singularity, due to massive gravity fields? I find this paradoxical to say the least.
    This paradox would pertain to a Big Bounce too, no?
     
  11. Aug 19, 2010 #10

    Borek

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    It all depends on the Universe density and initial speed of expansion - please reread cepheid's post (three scenarios).
     
  12. Aug 19, 2010 #11

    Chronos

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    Bah, blaming it on God is a copout, not an answer. Divine intervention [God] is the court of last resort. There are still far more questions than answers. I believe God is amused, yet fascinated, by our fumbling efforts to solve the puzzles set before us - thus explaining why God tolerates our existence.

    Expansion is the current favorite to explain why the universe did not immediately recollapse after forming. But, hey, it doen't even make sense for it to come into existence out of a singularity. Injecting bizarre initial conditions is the only apparent explanation. Adding bounces does not 'cure' this conundrum, it merely assigns 'first cause' to some inherently unobservable pre-universe state [i.e., oblivion]. Pushing it under this rug is just a bit too evasive, clean and convenient for my taste.
     
  13. Aug 25, 2010 #12
    Chronos, it sounds like you find the Big Bang scenario to be less than credible or am I misinterpreting your meaning here?
     
  14. Aug 27, 2010 #13
    Hi to all,
    I also agree with the sentiments of Chronos, science should not become science fiction where unrealistic ideas are arbitrarily inserted into scientific speculations. New ideas should have some scientific proof or evidences or must be based on good theories. To speculate a Big Bang at the beginning of the universe, originating from a singularity, seems to me, to be too speculative. Leaving religion and meta physic out of our discussion, what we know is that at the beginning of the universe there existed finite energy and the universal laws that govern the evolutionary process according to which the universe evolved. We also know that all the energy, dark or light, which composes the universe, is eternal according to Einstein theory that energy can not be created or destroyed. We also know that energy consists basically of quanta particles, and thus I find it hard to understand that all this cosmic energy, all these quanta particles could exist in a singularity. Each quanta particle has space and consists of a definite quantity of energy eg. E = h f, where h is the Planck constant and f stands for the frequency of the photon. I am more inclined to believe that the first structure of the universe was huge big blob of energy, may be even a huge black hole, when its evolutionary process began forming first subatomic particles, atoms, molecules, galaxies and etc.
    Yours Cosvis.
     
  15. Aug 27, 2010 #14

    Chronos

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    I am totally on board with the big bang theory - after the first trillionth or so of a second. Of course time = zero is the juiciest part of the mystery. In my mind, not only physics, but, logic breaks down at that point. I consider 'branes' and 'bounces' as equally unlikely and unprovable as a creation event.
     
  16. Aug 28, 2010 #15
    How does the fanciful **** that is ID, in any way conflict with a BB event? A god could dictate any initial conditions it wants... it's people who feel the need for that to conform to their particular religious flavor. As for the "it's just a theory"... you just described all of theoretical physics, congrats. You then need to examine observational and other support for a given theory, and compare it to ID, which isn't even a theory, just a religious postulate with NO support.
     
  17. Aug 28, 2010 #16
    We can't really imagine infinite cycles, nothingness, or infinity as a natural state, so pick your poison and it's going to kill human capacity for logic. That doesn't mean it cannot be modeled however, and that those models can't be a functional approximation of nature. I think that's the best anyone can realistically hope for.
     
  18. Aug 28, 2010 #17
    I have a problem with current BB theory. One of the big ideas about BB is that it is that the whole 'cosmic egg' started out as an infinitely compressed (or almost infinitely compressed) body that was composed of nothing but energy. There is a very big problem with that. Infinitely compressed would mean the gravity would all but stop photons/gluons/mesons to a stop. Whether it would do it through relativistic effects (that has gigantic implications I can talk about later) or through "potential energy". But potential energy is not an energy associated with zero rest mass [ZRM] particles. It is in the gravitational position of MATTER. Or the compression of MATTER. Even leaving that as too absolute, what potential energy does a particle have at the bottom of a gravitational distortion? If all the zero rest mass particles are brought near a stop, where does their energy go?
     
  19. Aug 28, 2010 #18

    bcrowell

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    And next time you want to make a lightbulb light up, don't forget voodoo as an alternative to Ohm's law. Ohm's law is only a theory.
     
  20. Aug 28, 2010 #19
    :rofl:

    My lightbulbs work by harnessing the energy of sleeping elves!
     
  21. Aug 29, 2010 #20
    Hi Chronos and all,
    I find the idea of zero time understandable from Einstein's relativity theory where he speculates that at the speed of light its time dimension has become zero (time dilation). Light or quanta particles travel at the speed of light thus they must exist in a special structure where time is zero. This connects also with Einstein theory that energy can not be created or destroyed. Thus, from a scientific point of view, energy is eternal and physical time only began when particles where formed that travelled slower than the speed of light.
    Yours Cosvis.
     
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