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, little bangs, or sontaneous creation?

  1. Feb 23, 2009 #1
    Broadly speaking, any new theory, (plate tectonics, origin of species etc.), on an established subject, will be greeted with howls of opposition, but with the course of time and ever more supporting evidence, the theory will gain favour, as it was with the big bang. The principal evidence was the fact that galaxies could be seen to be moving apart, to reverse would bring them together. What is the observed phenomena that has caused a move away from the notion that all was once together, to todays notion that the big bang was not at any one particular point but instead, occurred everywhere at once.
     
  2. jcsd
  3. Feb 23, 2009 #2

    Ich

    User Avatar
    Science Advisor

    There is no such move.
     
  4. Feb 23, 2009 #3
    i think it is more an understanding that the BB did not occur "within" some empty space which it then expanded in to fill. at the time of the BB, that WAS the entirity of spacetime, so it did "occur everywhere at once". since that time, spacetime has expanded carrying everything along with it, such that there is no "center" nor any particular "location" where it occurred - it is all around us.
     
  5. Feb 24, 2009 #4

    Chalnoth

    User Avatar
    Science Advisor

    Indeed. The statement that it happened "everywhere at once" was always part of the big bang theory, from the time it was first proposed.
     
  6. Feb 25, 2009 #5
    Thank you for your replies. So the term "everywhere at once" refers to all that exists within what we call the universe, including the space between all that exists, and that this has always been the case. Even when the universe was half its current size, a quarter, an eighth etc., all the way back to it's moment, and point, of origin. Everywhere at once was always inside the universe because there was nowhere outside. So, in effect, the universe is the big bang? Which was small, and got big.
     
  7. Feb 25, 2009 #6

    Chalnoth

    User Avatar
    Science Advisor

    Basically, yes. Just bear in mind that the actual point at the start in the big bang theory is incorrect: the theory breaks down before we go back to the point where our universe was that dense. Also bear in mind that the big bang theory doesn't preclude the possibility that there exist other regions out there, some of which will be very much like our own, probably most of which will be very much unlike our own.
     
  8. Feb 26, 2009 #7

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    There have been "tired light" theories proposed which attempt to provide an alternative explanation for the red shift of distant objects by means other than recession velocity...the Hubble effect being the first nail in the "steady state universe" coffin. But some form of Big Bang cosmology is the current consensus and not likely to change. The Wikipedia article is a good layman level overview of the main evidence.

    However I personally don't think the coffin is quite closed. I'm working on a paper which will (I think) at the least point out some need for corrections to current interpretations of the astronomical data. I doubt my results will overturn the BB theory but it will demonstrate a need to apply corrections to recessional velocity calculations. It isn't a new "tired light" theory but rather a relativistic phenomenon which I think has been overlooked. I've about finished the calculations and need to do more literature search before its publishable.
     
  9. Feb 26, 2009 #8
    This is more of a philosophical question surely?:smile:

    The term everywhere in Physics could only mean - All of Space. (Capital S for space)

    Since whatever the size or moment in time, the universe is All of Space.
    Therefore at its creation and the nano/microseconds after the Big Bang involved the whole universe and therefore All of space.

    i.e. it occured Everywhere


    The multiverse theory!?

    Love it - except it is unprovable and doesn't it have echoes (echoes as in Not identical) of the debunked Steady state theory in a way.
     
  10. Feb 26, 2009 #9

    "Tired light" - Interesting! Is it it - i.e. speed of light decreases with time and was faster closer to the time of the Big Bang

    Therefore the further away the galaxy the faster its speed of light at that time and the photons we receive (from that galaxy) pertain to a speed of light much faster than the speed we experience here on Earth.

    How would you go about proving that this is indeed the correct explanation for the Red Shift - not challenging you - just curious and very interested.
     
  11. Feb 26, 2009 #10

    Chalnoth

    User Avatar
    Science Advisor

    The only alternative to a multiverse theory is the statement that there is only one way a universe can possibly exist: in a way that is conducive to the formation of life. I personally find that unpalatable.

    No, I don't think it even remotely has echoes of the steady state theory. As for unprovable, that's not necessarily true. We can't do it yet, of course. But if there were a theory that we could detect through experiments right here on Earth that unambiguously predicted a multiverse of this nature, then we could say that it's been demonstrated.

    Here's an example of one way in which this might be done: consider that there is a range of the cosmological constant for life to be possible. If the cosmological constant is too high, then no structure forms. If it is too negative, then it recollapses back on itself in basically no time. So, if we are to examine any theory that has many possible values for the cosmological constant, we can only seriously consider those regions of parameter space where life is possible.

    Now, imagine that we had a theory that predicted two things. First, it unambiguously predicts that when a region of the universe forms, it undergoes a series of spontaneous symmetry breaking events. Like a pencil that you've stood on its end falling down, these spontaneous events could happen in any number of different ways. But, as it turns out, this imaginary theory specifically predicts that the cosmological constant cannot take any value, but actually predicts that it can only take one of a series of discrete values. And it just so happens that only one of these possible values is in the range where life is possible. If it were to be the case that this predicted value of the cosmological constant exactly matched the value we measure, then this would be powerful evidence of a multiverse: it wouldn't be reasonable to expect that the entire universe had settled upon the one value of this parameter capable of life, but it works just fine if it happened many, many times.

    This evidence alone probably wouldn't be strong enough to convince most scientists, of course, but if it was buttressed with a series of other, independent experimental results, then I could say with confidence that there is a multiverse of this form.
     
  12. Feb 27, 2009 #11
    Your multiverse theory is - several or alternative ways the universe might exist.

    The one I'm referring to is akin to the 'island universe' theories.

    So we're talking about 2 different things.:smile:
     
  13. Feb 27, 2009 #12

    Chalnoth

    User Avatar
    Science Advisor

    You mean just the idea that the universe is much larger than the horizon scale? Well, we already knew that.
     
  14. Feb 28, 2009 #13

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Why is beyond observational range an issue? That is not science.
     
  15. Feb 28, 2009 #14

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    No not variable speed of light. Rather dissipation so that wavelength gets stretched. For details and variations go google 'tired light'. Note that the "speed of light" is now a mathematical constant defining the unit conversion between time units and distance units. In relativity varying the speed of light is equivalent to varying distance relative to time so we leave c constant and consider variation of the geometry of space-time.
     
  16. Feb 28, 2009 #15

    Chalnoth

    User Avatar
    Science Advisor

    Well, if you mean a changing speed of light since the distance of last scattering, well, that's ruled out by experiment. There have been some other varying-speed-of-light theories that have been proposed that may potentially work as alternatives to inflation, but they seem to me to be rather less appealing, as they require not a smoothly-varying speed of light, but instead a speed which changes quite suddenly at a specific point in time. There's also no mechanism for the beginning that is built into these theories, while inflation offers a relatively easy one (beginning as a quantum fluctuation).

    Actually, it's not that easy. A simple coordinate transformation doesn't change anything in General Relativity. It simply changes what you mean by the numbers. You have to be really careful to actually change the speed of light in General Relativity. Most authors on this subject haven't been careful enough.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Big bang, little bangs, or sontaneous creation?
  1. The Big Bang (Replies: 2)

  2. The Big Bang (Replies: 38)

Loading...