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Is Big Bang 100% true?

  1. Dec 19, 2011 #1
    Would you bet your life on it?

    Big Bang proof supposedly came from:

    1. Redshift
    2. Cosmic Background Radiation
    3. Deuterium and baryogenesis

    what else?

    Is there no other way for them to occur without the Big Bang? but there is this Colliding Branes Theory about two branes colliding and producing the Bang everywhere. Meaning it doesn't occur at a single point but at multiple points so not really Big Bang but Multiple Bangs. Is it a leading candidate against the Big Bang theory or does the colliding branes theory produced a singular Big Bang too?

    Do you have list of all the evidences of the Big Bang in a site so any theory against it has to explain each point by point?
  2. jcsd
  3. Dec 19, 2011 #2


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    The standard big bang model does not address the moment of the bang itself. It is instead a model that describes how the universe evolved from a hot and dense state in its youth to a cooler and less dense state at the present. The standard big bang model purports that the big bang happened everywhere at once, not at a single point. This is an important misconception to straighten out. The colliding branes theory is a proposal that seeks to explain the physical mechanism for the big bang itself. Therefore, it is not in opposition to the standard big bang model; rather, it seeks to extend it. The colliding branes theory is still only hypothesis. The colliding branes theory has the rather unfortunate name of "ekpyrosis" in case you wish to read more about it.
  4. Dec 19, 2011 #3
    What I meant to say was the colliding branes just bang already existing spacetime. Whereas in original Big Bang theory, spacetime was expanded and created by the Big Bang. There's the important difference. When spacetime already exist and you bang every point of them. It's no longer Big Bang but some kind of Branes Bang (Ekpyrosis)
  5. Dec 19, 2011 #4


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    As to whether the Big Bang is 100% true, scientists now know that it is between 98.2% and 101.3% true, and it is believed that the error bar is constantly shrinking. However, philosophers keep saying, "We're gonna need a bigger error bar."
  6. Dec 19, 2011 #5


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    We got a JimmySnyder contender here!
  7. Dec 19, 2011 #6
    Q. How many galaxies can fit on the head of a pin?

    A. Billions and billions of them or all of them including billions of universes.

    Modern physics exceed any unbelievableness that maybe fewer than 3% of the public is aware of planck density. Anyone can share in a few sentences how to calculate the planck density such that billions and billions of galaxies can fit into the planck length?
  8. Dec 19, 2011 #7


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    Well, those galaxies are made of atoms. And I'm pretty sure "Pauli" would "exclude" them from fitting all on the same pin... in "principle".
  9. Dec 19, 2011 #8


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    Glyde, it sounds like you swallowed another popularization. :smile:

    You could re-read what Brian Powell said, which I think is carefully worded, and he's a pro. As I understand it, the classic BB theory does not say anything about what was or what happened right at the start of expansion. So it does not say space was "created". The classic 1915-1923 theory would not know how to say that. It just breaks down and quits as it approaches that point.

    Popularized accounts say things like that. But not to take seriously :biggrin:

    Nowadays classic BB theory has been extended in various ways, which still have to be tested. They avoid "singularity", that is they do not break down and give meaningless results. They go back to the start of expansion and further back in time before start of expansion. There's always something there, some process being described.
    I don't know any currently researched BB extension that says space or time are "created".
    There may be such but that would not be typical of the majority of the research papers that model events/conditions around start of expansion.

    In another thread you were talking about getting your ideas from Brian Greene books. One of the mods told you there that you have to choose between pop-sci and getting it straight.
    I urge you to get the pop-sci stuff out of mind and start trying to get a grounding in contemporary cosmology concepts. We are reasonably well set up to offer that here...

    For starters why don't you see what you can dig up in our local cosmo forum FAQ.

    Or try the "einstein-online" link in my signature. It helps sort some of the misconceptions and confusion about BB out. It's the straight-dope public outreach website of a German federal research institute. Not commercial sell-a-lot-of-books hucksterism, or a go-for-the-ratings Telly series.
    Last edited: Dec 19, 2011
  10. Dec 19, 2011 #9


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    You seem to be missing the idea that there weren't billions of billions of galaxies at the BB. Hell, there weren't even quarks or gluons! They only appear after inflation (at about 10^-37 s, IIRC), you only start to get hadrons at about a microsecond after the BB.

    I think you have some misunderstandings about the Big Bang.

    ETA: My mistake, inflation occurs not at 10^-43 but at 10^-37 seconds. This is what I get when I don't verify things.
    Last edited: Dec 19, 2011
  11. Dec 19, 2011 #10
    No. I mean I mentioned about Planck Density.. meaning since mass=energy.. then the potential energy of those billions and billions of galaxies are contained in planck length.. after inflation.. the energy changed to mass as electron-anti electron pair is produced. I know all about it, but don't know if the calculations are proven that the energy of billions of galaxies can really be contained in a planck length... and if so.. whether this proves the Big Bang or just an added support for it...
  12. Dec 19, 2011 #11


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    We are sure something happened. It was a long time ago.
  13. Dec 19, 2011 #12
    I've read so many references about the Big Bang from Steven Weinberg "The First Three Minutes" to Rees and other pros. So I'm well aware of the arguments. About space being created. Redshift occurs because space was being expanded.. so inflation is not an explosion inside spacetime.. it is spacetime being inflated... are you denying this?

  14. Dec 19, 2011 #13


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    Ok, it seemed from your post that you meant actual atoms.

    Well, the Planck density is the approximate density one Planck second after the big bang, not at the singularity. Approximately a microsecond of calculation, which I'm sure you could do yourself (why didn't you?), gives a Planck density of 5.1 × 1096 kg/m3 - about 1023 solar masses squeezed into the space of a single atomic nucleus. But that's not at the singularity anyway, so I don't know why you're so hung up on it.
  15. Dec 19, 2011 #14
    From the site Marcus shared at http://www.einstein-online.info/spotlights/big_bangs
    It says:

    "At ultra-high densities, with the whole of the observable universe squeezed into a volume much smaller than that of an atom"

    Of course I didn't say the atoms are squeezed inside the planck area. But since energy=mass, just the energy. So it is true that the energy of billions and billions of galaxies can fit inside the planck area. What is the calculations for it.. is it 100% true or subject to controversy?
  16. Dec 19, 2011 #15


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    I really don't see the problem with the energy densities required. It's not like energy is subject to Pauli exclusion, or takes up any space. It's energy, you could pack as much in as you want.
  17. Dec 19, 2011 #16
    No problem with pressure? It really exceeds the imagination the energy of all existing galaxies can fit into the planck area billions and billions of times smaller than an atom. So far. What experiments have showed that there is no limit to energy compression. So you are saying that it's possible billions of universes can also fit inside the planck area (as far as energy is concerned)? There is just no limit??
  18. Dec 19, 2011 #17


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    It doesn't really stretch my imagination. Perhaps that's a sign I've done too much physics. But just because it exceeds the imagination doesn't mean it's not real. Try imagining 10^23 objects, for instance!

    If I had no problem with energy density, I'd hardly have one with pressure, given that pressure is energy/volume. They're pretty much equivalent statements.

    Edited to add.

    There is no limit on energy density. To dive into some GR, local lorentz symmetry is enough to show that the energy density is not limited in GR.

    The energy density is the T00 component of the stress energy tensor. In GR the solution depends on the full stress-energy tensor, so we can't just consider T00. Because the energy density is a component of a tensor, it is coordinate dependent. So, if we begin with a non black hole solution, with some energy somewhere, we can always choose a coordinate system to make the energy density as large as we like.

    Now, how about over a finite area?

    Consider the Roberston-Walker solution with a perfect fluid (not bad as an example, a QGP is a perfect fluid)

    So, for a perfect fluid in the comoving frame:

    Tab =
    ρ 0 0 0
    0 p 0 0
    0 0 p 0
    0 0 0 p

    (sorry, don't know how to do tensors on this site)

    Now if we change to a different coordinate system, using the coordinate transformation:
    γ −βγ 0 0
    −βγ γ 0 0
    0 0 1 0
    0 0 0 1

    The energy density will transform as: ρ′=γ2(ρ+pβ2)

    So, the energy density can be as large as we like!


    (You could have googled this: http://physics.stackexchange.com/questions/7771/is-there-an-energy-density-limit-in-gr)

    Edited again: And this is with undergraduate general relativity. Not controversial.
    Edited again again: However, you'd probably want QG to understand times that close to the BB. However, local lorentz symmetry would probably stick around in QG
    Last edited: Dec 19, 2011
  19. Dec 20, 2011 #18
    Wow. Before this. I thought it was already incredible that the energy of billions of galaxies can fit in the planck area billions of times smaller than an atom. Now you are saying that an infinite number of universes can fit in the planck area because there is no limit?? Hope others can second motion or verify this (that there is no limit.. or if there is.. how many billions of universes can fit in the planck area.. of course in terms of energy of mass converted)).
  20. Dec 20, 2011 #19


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    It's right there in the maths! You don't need other peoples opinions - do you think the maths works out? If you don't, why? If you don't understand the maths, learn it!

    I am saying that in GR, an arbitrary amount of energy can exist in an arbitrary volume.

    Can I ask why you're so hung up on the Planck area thing?

    Think of it another way - if you think of energy in terms of photons, which are bosons, then you can have an arbitrary amount of them in whatever volume you want, due to Bose enhancement. (AKA the lack of Pauli Blocking)
  21. Dec 20, 2011 #20
    a book I read says the universe began as a bubble sitting in a liquid. The liquid is straight string energy at absolute zero with a quiver of waves moving through it. The first strings jumped into the bubble and went BANG and continued. This raised the temperature of the inside surface of the bubble which decayed the liquid into circular string inside the bubble forming all the particles. A black hole with lots of gravity is this energy trying to revert to it's previous liquid form. Dark energy is the gravitational pull of the surrounding liquid on all matter and is why it is accelerating. It would account for the even distribution of galaxies. Einstein's GR black hole centre defining space and energy as infinity + would also define the liquid.
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