The Big Bang and Inflation:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Jul 20, 2015.

  1. paddoboy Valued Senior Member

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    I have just come across an Interesting article from a science blog which suggests Inflation happened before the BB.
    I would like to get some critical appraisal on the suggestion.
    Here it is.........
    http://scienceblogs.com/startswithabang/2010/01/12/q-a-did-inflation-happen-befor/

    Last week, I started a new series on The Greatest Story Ever Told, about the origin and evolution of the Universe. In it, I asserted that inflation is the very first thing we can definitively say anything sensible about, and that it happened before the big bang. This runs contrary to a lot of statements out there by a lot of reputable people, including this “timeline” image from Discover Magazine:



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    Everything else aside, it’s very important to remember where the idea of the Big Bang comes from. What we see today, when we look out at the Universe, is that the farther away things are from us, the faster they move away from us.



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    So from that, we learn that the Universe is expanding. Using what we know about gravity, we find that the amount of matter and energy is directly related to the expansion rate of the Universe. Since the Universe is expanding, that means that in the past, the Universe was smaller, denser, expanding faster, and hotter, which means higher in Energy.




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    The Big Bang, an idea dating back to the 1940s, was a brilliant extrapolation of this idea. If the Universe was smaller, denser, and hotter in the past, George Gamow and his collaborators stated, then a few very interesting things happen.

    Far enough in the past, the Universe must have been hot enough to prevent the formation of neutral atoms. If this were true, we should see the leftover radiation that kept the Universe ionized at this time. We not only discovered this, we can measure the temperature fluctuations in thisCosmic Microwave Background, and show them to you.



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    As you travel further back in time, more interesting things happen at higher and higher energies. (A good part of the new The Greatest Story Ever Told series will be taking you through what those things are and when they happen.) When the big bang was first conceived, the extrapolation went all the way back to a singularity, when all the matter and energy in the Universe was concentrated at a single point, where the expansion was arbitrarily fast, and the temperature was practically infinite.



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    But when inflation came along, all of that changed. No longer could we extrapolate all the way back to a singularity. If we wound the clock of the Universe backwards, we would discover something remarkable. At some point, about 10-30 seconds before we would anticipate running into that singularity, the Universe instead would undergo inflation (in reverse, if we’re looking backwards), and we have no evidence for anything that came before it.



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    The Big Bang, instead of being a singularity, is the set of initial conditions of an extremely hot, dense, expanding Universe that exists immediately after the end of inflation.

    Was there a singularity before inflation? Possibly, but at this point, we have no way of knowing. Inflation is the first thing we can say anything definitive about, but it definitely comes before what we traditionally call “The Big Bang”. So maybe I should admit that Starts With A Bang isn’t really the starting point of everything, after all, just the start of where our observable Universe comes from.

    But the answer to our Q & A for today? Yes, inflation happens before the Big Bang, and ever since its acceptance, has removed the necessity of a singularity at the start.
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  3. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Awhile back I did a Youtube video with some layman critical thinking on that subject, which I posted for discussion. Several of the same images that your source used are also in my video. Take a look at it here:



    It is just ideas, but it presents a scenario that would produce the universe as we see it, with preconditions to our Big Bang, and processes that suggest that the greater universe might be a multiple big bang landscape, where parent arenas fill with galactic material, expand until they intersect and overlap with other arenas, whereupon gravity causes a Big Crunch to form at the center of gravity of the overlap space. The crunch grows by accumulating galactic material from the parent arenas until the compression of gravity reaches critical capacity and causes it to collapsse/bang. In comparison with your link, the collapse/bang would equate to the precondtions, replacing the concept of the quantum foam he refers to.
     
    Last edited: Jul 21, 2015
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  5. paddoboy Valued Senior Member

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    It's still of course entirely speculative, and that's the way I accept it.
    Still I would like some critical comment particularly on the idea of Inflation predating the BB.
    Myself, when I happen to be explaining the BB, always do so as the "evolution of space and time as we know them". suggesting possibly that what existed before was space and time as we don't know them.
     
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  7. OnlyMe Valued Senior Member

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    Doesn't that answer your own question in the OP?
     
  8. paddoboy Valued Senior Member

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    Don't think so...There's speculation, and there's speculation.
    I'm simply asking if this scenario can be in someway viable with present Inflation scenarios.
     
  9. tashja Registered Senior Member

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    It appears to be highly speculative:

     
  10. paddoboy Valued Senior Member

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    Thanks tashja......
    I would have linked him to comment on the article though, but don't worry anyway...Just a thought I had today while searching.
    Thanks again.
     
  11. tashja Registered Senior Member

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    I did provide Prof. Krauss with a link to the article. Dunno if he followed it, though. But if you're invested in the idea, I could always ask another expert on inflation.

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  12. tashja Registered Senior Member

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    OK, here's Prof. Linde's reply:

     
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  13. paddoboy Valued Senior Member

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    What can I say? How the bloody hell do you do it? Thanks muchly, Vinaka vaka levu!
     
  14. Schmelzer Valued Senior Member

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    If what you name "BB" is simply the fact that there was a state of the universe with a very high density, similar to, say, the density inside a neutron star, then, yes, inflation was "before" the "BB".

    If one names "BB" the singularity itself, then, no, simply because in this case the notion "before the BB" would be meaningless.

    The claim "inflation is the very first thing we can definitively say anything sensible about" is correct.

    "The Big Bang, instead of being a singularity, is the set of initial conditions of an extremely hot, dense, expanding Universe that exists immediately after the end of inflation." is correct too.

    "Yes, inflation happens before the Big Bang, and ever since its acceptance, has removed the necessity of a singularity at the start." is questionable. Because the standard theory of inflation, which is based on the idea of some change of the vacuum state of some scalar field, would give inflation only during some time. It would predict, therefore, that before this inflation the laws of GR would be similar, and, therefore, this would give the same standard predictions, namely a big bang singularity. So, the mainstream model of inflation does not automatically get rid of the singularity. But there are a lot of variants of inflation theory, I have not cared to consider them in detail, but remember that there are claims about some "eternal inflation", so maybe there are models without singularity. (I remember to have seen such an article, but not cared about the seriousness.)

    If one would use, instead, my theory, there would be a big crunch before the big bang, and inflation would be the process of transforming this big crunch into a big bang. So there would be no singularity.

    On the other hand, if we simply ignore theory, and look at the observable facts, there remains serious evidence for inflation, but no evidence about what was before inflation.
     
  15. tashja Registered Senior Member

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    715
    You're welcome Paddo. Prof. Steinhardt also responded to my email. Here's his reply:

     
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  16. tashja Registered Senior Member

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    Dr. Schmelzer, your theory sounds a lot like Profs. Steinhardt's & Turok's Cyclic Model. Was it developed contemporaneously? Did you consider collaborating with them?
     
  17. Schmelzer Valued Senior Member

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    It was developed independently, I was essentially following the "Relativistic Theory of Gravity" of Logunov at all, which also gives an oscillating universe, but with a completely different metaphysical interpretation and justification of the theory.

    If I look at http://arxiv.org/pdf/1312.0739v2.pdf (which is simply the first result of search for above authors on arxiv) I find as equation (1) a term containing \( \int d^4x \sqrt{-g} \frac12 ((\partial \phi)^2 - (\partial h)^2 ) \), which is mathematically similar to my Lagrangian, which also contains scalar fields - the preferred coordinates - and, in the variant which gives inflation, also with different signs for spatial coordinates and time. So, I do not wonder that this Lagrangian can give a big bounce.

    Of course, in above theories the sign of the additional scalar field is wrong, which is what allows to violate the energy conditions and to circumvent the singularity theorems. So, above theories have to worry why this is not dangerous for them. He argues that "Although the lift introduces a second scalar field φ with wrong-sign kinetic energy, it is obviously a gauge-artifact since ...". In my theory the point is that the preferred time is something different than a field. Even if the equations for small modifications are similar, big modifications are simply impossible, because they do not define valid systems of coordinates.

    In this sense, the theories seem conceptually quite different. In particular, I have a simple fallback possibility: I can simply switch to the other sign for the term for the time coordinate, so that this problem disappears - but together with the explanation of inflation and the big bounce instead of big bang prediction, and also with the stable gravastars instead of black holes. This would make the theory much closer to GR, and in this sense less interesting as an alternative, so I prefer the variant with the "wrong" sign. But this is a quite subjective preference, all the really important conceptual aspects of the theory do not depend on this choice of the sign.
     
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  18. brucep Valued Senior Member

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    That must be Prof. Steinhardt idea. There's a reason that inflation is the preferred model at this time. Guth's idea didn't involve a singularity. It was a marriage of GR and quantum field theory. What inflates in Guths model is a soliton in a quantum scalar field. Which has the ~ mass of a garden pea prior to the inflation event. Last I heard inflation was the path for cosmology to predictive science.
     
    Last edited: Jul 23, 2015
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  19. Dinosaur Rational Skeptic Valued Senior Member

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    Inflation seems a bit ad hoc. It seems to be the best explanation as of now. I wonder if it will survive.
     
  20. danshawen Valued Senior Member

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    Perhaps inflation might be a good path toward making cosmology a predictive science.

    Let's assume that it is. Part of the description of the Big Bang is that the expanding universe, run backwards in time, suggests that 13.7 b years ago, energy was HIGHLY CONCENTRATED into a high energy mixture of matter plus energy.

    What sense does it really make to decide a less voluminous universe was a higher energy one if just a zeptosecond before the Big Bang or inflation, no energy was acknowledged to exist in the universe at all? Forces and particle creation always happens in pairs, or else it is another one of those reactionless scenarios discussed in another thread. What happened to the other universe we must have collided with? Shouldn't it be termed the Big Smash, just to be consistent in terms of energy conservation?

    If a "Big Smash" is what happened, we should be able to see a faint remnant of it at 2 x 13.7 billion light years away, and it is likely that faint remnant is all we would see. It should also be the most distant object we could view, and it could be in literally any direction in the sky. The energy of the object would likewise be indeterminate, but red shifts in the case of such an object would be at the extreme low spectral limit of possible detection by any instrument. Like the James Webb telescope, for instance.

    Since the energies of such an event would be more extreme before the event, it would resemble the superforce in Guth's inflation theory for as long as inflation lasted. It would not explain the acceleration due to dark energy, but then neither does inflation theory, in actual fact.

    The fact that you term what is there immediately after the event as high energy implies an adherence, at least in principle, to the idea of the conservation of energy, does it not? Or to put it another way, does energy 'add up' or remain conserved when concentrated into a smaller volume or not?

    Or is this just another sparkling example of that other conservation law you referenced in another thread?
     
    Last edited: Aug 5, 2015
  21. paddoboy Valued Senior Member

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    Except as the model logically tells us, atoms were not formed during that first 380,000 years and the free roaming electrons, protons and neutrons, made the Universe at that epoch opaque.
    We may not know the true nature of DE, but it is there and can be used to explain inflation and the universal acceleration of the expansion of spacetime.
    [1] At the first instant after the BB, energies associated with spacetime were such that the impetus drove the period we know as inflation.
    [2]At the same time, the density of the universe, and subsequently gravity, acted as a brake to slow the expansion down to a more sedate pace.
    [3]Gradually as the DE component which acts as a constant force over all of spacetime, overcame the lessening densities and hence the lessening effects of gravity trying to halt and reverse the expansion, the opposite effect took hold, ie: The expansion started to accelerate, the phase we find ourselves in today.
     
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  22. danshawen Valued Senior Member

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    But we also know that colliders such as the LHC do a pretty good job of simulating high energy physics, and they do this by smashing existing atoms together; not by coaxing energy out of pure vacuum, out of absolutely nothing that is energy or matter we would recognize.

    So instead of trying to relate the BB to forces we already know about, we instead create a hypothesis that there is some new energy we know nothing about.

    All that remains is to test the hypothesis, and then accept or reject it. If DE were a superstition, it would be something like a DEity, wouldn't it?

    I don't often say this, but if Occam's razor were to be applied to this situation, what would it probably tell us?
     
  23. paddoboy Valued Senior Member

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    "We"didn't just create it. We invoked something that was evidenced in the data received. Same with DM. [And it appears so far that that particular guess was correct]
    As I said it was invoked on the evidence by those at the coal face, based on the data received.....no superstition, no deity, just a plain observation.
    That spacetime has an "inbuilt" inherent energy component, that maybe the CC.
    In the meantime, mainstream science continues to work on the unknown factors and use all the equipment and subsequent data available to them.
     

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