Seeking Evidence of Cosmological Inflation:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Apr 26, 2016.

  1. paddoboy Valued Senior Member

    Messages:
    21,225
    In the view of most reputable cosmologists they can and are......
    It can be said the further we look, the faster the universe is expanding, until we get to a point where it expands at FTL.
    But there are a couple of ways of looking at it......
    http://gizmodo.com/how-is-it-possible-that-galaxies-are-moving-away-from-u-1736224001
    and
    http://www.preposterousuniverse.com...never-expands-faster-than-the-speed-of-light/
    and this paper....
    http://arxiv.org/abs/astro-ph/0310808
    In essence,[1] Take two objects far enough apart, and the recessional velocity, due to spacetime expansion will be in excess of "c"
    [2] That in simple language means just as most professionals put it, that spacetime can expand at FTL.

    Sorry if this has confused things Alex, but you are right in what you assume, forgetting any technical pedant on semantics etc.

     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. paddoboy Valued Senior Member

    Messages:
    21,225
    ---------------------------------------------------
    p.s. @Schneibster, have perused a few pages of Thorpes' work and I am hooked.

    Please Register or Log in to view the hidden image!

    Please Register or Log in to view the hidden image!

    [/QUOTE]


    The same bloke that runs the link, Professor Hamilton also has a popular arXiv paper on what is called the river/water fall BH model:
    One I like a lot, due to the simplicity of the analogy and how it applies to msot types of BH's. It's also described at the link but here is the paper......
    http://arxiv.org/pdf/gr-qc/0411060v2.pdf
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. paddoboy Valued Senior Member

    Messages:
    21,225
    Note Alex, even in Sean Carroll's article and his assertion that the universe never expands at FTL, he does agree that two objects far enough apart, and the recessional velocity, due to spacetime expansion will be in excess of "c"

    Again, sorry for the confusion Alex: Perhaps Carroll needed an extra few bucks an decided to be controversial.

    Please Register or Log in to view the hidden image!

     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Schmelzer Valued Senior Member

    Messages:
    3,582
    Correct.

    No. It is wrong, because the universe does not have a "speed of expansion" measured in m/s, but an expansion rate measured in 1/s, which cannot be faster or slower than the speed of light measured in m/s. If a wrong message somehow may "convey successfully" something which could be also epxlained in a correct way may be of interest for cheaters, or for you, but not for me.

    (Further proofs that paddoboy is uneducable deleted.)
    Fine so far. But now:
    No. Nonsense remains nonsense even in simple language. (If spacetime can expand faster than light, please give me some information how fast light expands.) And even if some professionals use it. BTW, I have not seen such a nonsense in any of the three links. Ok, not looked very careful, but I haven't seen it. If you have a quote, please give it.
     
  8. Xelasnave.1947 Valued Senior Member

    Messages:
    2,919
    Thank you paddoboy for taking the time to help me understand things a little better.
    I suppose it is funny that at my age that I find cosmology so interesting.
    But I pick up a little here and there and frankly even now think I have a reasonable grip on most of the mainstream concepts. I do think I can detect what I would loosely term flaws in some propositions put forward here.
    There are times I feel I could answer certain questions put by others but mostly they dont seem to listern to others who clearly have a better grip than me... So I doubt they wont listern to me so I let others try to teach a d help them.

    Thank you again and I wonder if anyone will try and make things clearer again even at the risk of confusing me.
    Alex
     
  9. Xelasnave.1947 Valued Senior Member

    Messages:
    2,919
    Thank you

    Alex
     
  10. Schneibster Registered Member

    Messages:
    390
    The short answer is "Yes, pretty much."

    There is a lot of confusion inserted into the conversation due to the speed-of-light postulate in SRT and this being an apparent violation of it; what this boils down to is that recession of distant galaxies due to expansion of the universe is not motion that violates the speed-of-light postulate.

    For a much more detailed view see the paper I linked for Write4U which paddoboy has linked again above for you.
     
  11. paddoboy Valued Senior Member

    Messages:
    21,225
    That's OK, I'm not really that interested in someone who claims that he has an ether hypothetical that explains and predicts better then GR.
    And strange you use the word "cheaters"...a rather emotional baseless response I suggest.
    And even further proof in your statements that to infer Inflation was FTL means that it doesn't apply to the rest of spaetime/universe adds to your own confusion/uneducabilty...among quite a few other errors as previously listed.
    Thank you.
    Uhh!

    Please Register or Log in to view the hidden image!

    You seem rather confused.
    Light/photons have wave lengths which I'm sure you know, and the frequency/wave length determines the colour: Light/photons travel/traverse spacetime following geodesic paths. eg: In curved spacetime the geodesic path is the shortest path between the emitter and the receiver, and from the point of view of the receiver, the emitter maybe gravitationally lensed.
    The expansion of spacetime over larger scales will see light/photons cosmologically red shifted to a distant receiver, its as simple as that.
    Oh and also light/photons although having no rest mass, does have momentum, and consequently will warp the spacetime in its vicinity albeit by an infinitesimal amount.
    It could be said that light/photons use the spacetime metric as a medium in which to traverse the universe: Please note that spacetime although a non physical entity is seen as real in the eyes of many professionals, just as I see it as real.
    Back onto the subject matter and........
    ,[1]Take two objects far enough apart, and the recessional velocity, due to spacetime expansion will be in excess of "c"
    [2] That in simple language means just as most professionals put it, that spacetime can expand at FTL.
     
  12. Xelasnave.1947 Valued Senior Member

    Messages:
    2,919
    Thank you for your well considered reply.
    Fortunately I never saw any difficulty and had understood there was no conflict because it was the expansion of space not matter travelling faster than light.

    Alex
     
    paddoboy and Schneibster like this.
  13. paddoboy Valued Senior Member

    Messages:
    21,225
    No probs, and please, don't let the age thing hinder what you desire to learn or know.
    Personally, although having an interest in space and cosmology all my life, it did not really peak until I read Stephen Hawking's Brief History of Time in the early 80's
    And your 2 bob's worth is welcome anytime!

    Please Register or Log in to view the hidden image!

     
  14. Xelasnave.1947 Valued Senior Member

    Messages:
    2,919
    Thank you for your positive encouragement paddoboy.
    Mmmm two bobs worth, you give away something there, I suspect few would understand.

    Alex
     
  15. paddoboy Valued Senior Member

    Messages:
    21,225
    Couple your 2 bob's worth with my 2 bob's worth, and it certainly over rides the 2 cent's worth as offered by some.

    Please Register or Log in to view the hidden image!

     
    Xelasnave.1947 likes this.
  16. Write4U Valued Senior Member

    Messages:
    4,561
    Is it necessary that a permittive condition of nothingness (not spacetime) needs to expand (propagate) at all?

    If we envision a fundamental *infinite non-physical permittive condition*, it needs not propagate at all, it is already *infinite* . Logically, a finite *nothingness* which expands (at any velocity) is by definition *something*.

    The expansion (unfolding) of physical spacetime (geometry) is a different matter altogether, IMO.

    It seems to me that these two entirely different states (conditions) are constantly mixed up, creating an unnecessary complication of having two expanding entities, one expanding at SOL into another condition expanding @ FTL. That is just sounds bizarre.

    Can anyone answer the question, "what is it the fundamental external condition that *allows* for spacetime to expand at all?". My guess is an *infinite nothingness*.
     
    Last edited: May 3, 2016
  17. Xelasnave.1947 Valued Senior Member

    Messages:
    2,919
    Thank you for your comments.
    I did not mention nothingness and I am not sure if such a condition exists.
    In the various voids observed by astronomers I expect that even these regions would not meet a description of nothingness.
    I am not suggesting an ether but would it not be reasonable to expect that even in these "empty" voids we would expect to find many particles and or waves passing by from sourses far away.
    I expect one could argue this most "empty" region would not qualify as "nothingness".

    In any event I think the terms "space" and "space time" are understood in science.

    I really do not wish to comment upon the concepts of finite and infinite other than to say what we can observe supports the ideas that galaxies we can observe are indeed racing away from us and each other.

    Alex
     
  18. paddoboy Valued Senior Member

    Messages:
    21,225
    To the question why does spacetime expand, or if you like why there is a recessional velocity between two points in the universe, I would say we don't really know, other than some sort of connection with the CC and/or whatever the DE is.
    On the other front SR says that nothing with mass can reach or exceed "c"
    Spacetime has no mass, so is not contained by that law at all.
     
  19. Write4U Valued Senior Member

    Messages:
    4,561
    With respect, this is the crux of my argument. I was not talking about "empty space", which would still be inside the geometry of our universe, but about the ability of the universe being allowed to expand at all, changing a previous condition of nothingness into spacetime, a process which is still ongoing. Are we not nested but expanding into a prior condition of nothingness?

    IMO, there MUST exist an a priori permittive condition which allows for our universe to expand at all. The only all-permittive condition I can imagine is a condition of Nothingness.

    This a priori condition would not have any physical properties other than being abstractly permittive of an expanding spacetime geometry, even if this spacetime is full of empty space with relatively little physical stuff occupying this empty spacetime geometry.

    As I understand it separating measurable space from time is impossible. This is why IMHO spacetime is expanding not into a previously existing space, but into a prior nothingness, a true vacuum.

    I can envision a singularity expanding and creating our existing universe. But (setting aside the concept of a multiverse for this scenario), is it not logical to say that there was *nothing else* apart from the BB singularity at the moment it started to inflate?

    To say that space existed before spacetime was created seems contradictory to me, but perhaps I am missing an important "other" explanation,
     
    Last edited: May 3, 2016
  20. Write4U Valued Senior Member

    Messages:
    4,561
    I agree with you on that point, but does it answer the question why the universe (spacetime) is *able* to expand at all, regardless of velocity? Is it expanding into a prior condition of *nothingness*?
     
    Last edited: May 3, 2016
  21. paddoboy Valued Senior Member

    Messages:
    21,225
    Actually to say that anything existed before t=0 is contradictory according to the BB. The beginning of time and space, or all there is.
    Yes, quite difficult to understand I agree.
    But there certainly is talk in scientific circles re "a universe from nothing" and the universe being the ultimate free lunch, but again all speculative.
    https://www.astrosociety.org/publications/a-universe-from-nothing/

    the next one is an interesting video featuring Professor Laurence Krauss it is an hour long though



     
  22. paddoboy Valued Senior Member

    Messages:
    21,225
    And that's the whole crux of the matter Alex: You hit the nail fair square on the noggin!

    Please Register or Log in to view the hidden image!


    Sorry, I missed that earlier.
     
  23. paddoboy Valued Senior Member

    Messages:
    21,225
    Simply we havn't got all the answers as yet.
    Take the time to watch the Krauss u tube video...well worth it.
     
    Write4U likes this.

Share This Page