Big Bang Theory Violates First Law of Thermodynamics

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Harmonic_Subset, Aug 27, 2020.

  1. arfa brane call me arf Valued Senior Member

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    7,021
    The Laws of Physics are time-symmetric. The BB event is (was) not time-symmetric. What does that mean, exactly?
    According to Einstein, time is relative.

    If distant photons had to pass through regions of space with strong gravitational fields it would affect their paths and the apparent time of travel. Since gravity acts on spacetime it seems to be the culprit, the reason the expansion is not time-symmetric (??). Simply put, gravity is changing (warping) the spacetime and changing the paths of photons and other particles.

    Luckily, gravity has little effect on spacetime overall (the cosmos is pretty flat, for as far out as we can see). But conservation depends on being able to predict what the likes of gravity will do to some region of spacetime, indeed it requires that all sources (and sinks) of energy are accounted for, and gravity at cosmological scales just doesn't allow this.

    Or Something.
     
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  3. QuarkHead Remedial Math Student Valued Senior Member

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    proof required
    Proof required.
     
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  5. arfa brane call me arf Valued Senior Member

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    There are no proofs in physics, but there is observation.

    A law of physics actually says nothing about the direction of time, implying that experiments can be run backwards even though this isn't actually possible.
    Why isn't it possible to reverse the direction of time? Physical laws don't tell us the reason.
     
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  7. Q-reeus Valued Senior Member

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    Gravitational deflection of light is not an irreversible process. In an ideally smoothly dispersed matter universe there are no macroscopic gravitational potential gradients anywhere hence no 'gravity' in the usual sense. The sole action of gravity in the very large is to try and slow and eventually reverse Hubble expansion. Which is not a time symmetry violating process.
    Don't confuse entropy growth with purportedly time irreversible dynamics. One deals with statistics, the other with basic dynamical interactions. This article may help:
    https://academic.oup.com/astrogeo/article/46/1/1.26/253257
     
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  8. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    run backwards

    Some experiments can be run backwards and finish up at your starting place

    A different concept to making time run backwards

    Some scientists contend time cannot run backwards because it does not exist. Which is also why it does not even run forward's

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  9. arfa brane call me arf Valued Senior Member

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    If you can, please give an example of a law of physics (or theory) which defines the direction of time.
    Otherwise give an example of a physical observation which contradicts time-symmetry in physics (if you think you know what time-symmetry means).
     
  10. Q-reeus Valued Senior Member

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    3,709
    Have you bothered to read that article I linked to? The take home point is the arrow of time is not defined by the basic physical laws but by special (low entropy) initial conditions.
    As it so happens, I'm working on something that just might allow a genuine violation of time-symmetry - which is not the same concept as thermodynamic irreversibility.
     
  11. arfa brane call me arf Valued Senior Member

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    7,021
    Which supports the claim made by physicists that the laws are time-symmetric, right? Unless there's something they haven't noticed yet?
     
  12. Q-reeus Valued Senior Member

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    3,709
    Something was nagging at the back of my mind - then it popped. There IS (afaik so far only) one known physical interaction that occasionally breaks time reversibility:

    PS: Links are given to more technical articles below vid window:
    More on B-meson oscillations and time reversal violation:
    Physics World Article: http://ve42.co/TimeReversal
    Original paper: https://arxiv.org/pdf/1410.1742.pdf
    https://en.wikipedia.org/wiki/B_meson
     
    Last edited: Aug 31, 2020
  13. QuarkHead Remedial Math Student Valued Senior Member

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    1,684
    So, you want a "physics" of an impossible universe? You're welcome to it.
     
  14. exchemist Valued Senior Member

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    This link is excellent and very clearly written. Thanks for posting.

    The idea that an entropy gap opened up at the time of the surface of last scattering, because of the different dependence of the temperature of matter and radiation on the cosmological scale factor was new to me and very enlightening. Given that this gap is sustained by cosmological expansion, there must be a question as to whether we ever reach the "heat death" of the universe after all!
     
    Last edited: Aug 31, 2020
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  15. arfa brane call me arf Valued Senior Member

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    7,021
    That's actually a really ridiculous thing to say. But perhaps you've never studied any physics.

    The laws of physics are time-symmetric because, as I said, none of them defines a time direction. This is well-known, but obviously not by you.
     
  16. arfa brane call me arf Valued Senior Member

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    7,021
    What Feynman said about it in one of his lectures:

    "Next we mention a very interesting symmetry which is obviously false, i.e., reversibility in time. The physical laws apparently cannot be reversible in time, because, as we know, all obvious phenomena are irreversible on a large scale: “The moving finger writes, and having writ, moves on.”

    So far as we can tell, this irreversibility is due to the very large number of particles involved, and if we could see the individual molecules, we would not be able to discern whether the machinery was working forward or backwards.

    To make it more precise: we build a small apparatus in which we know what all the atoms are doing, in which we can watch them jiggling. Now we build another apparatus like it, but which starts its motion in the final condition of the other one, with all the velocities precisely reversed. It will then go through the same motions, but exactly in reverse.

    Putting it another way: if we take a motion picture, with sufficient detail, of all the inner works of a piece of material and shine it on a screen and run it backwards, no physicist will be able to say, “That is against the laws of physics, that is doing something wrong!” If we do not see all the details, of course, the situation will be perfectly clear.

    If we see the egg splattering on the sidewalk and the shell cracking open, and so on, then we will surely say, “That is irreversible, because if we run the moving picture backwards the egg will all collect together and the shell will go back together, and that is obviously ridiculous!”

    But if we look at the individual atoms themselves, the laws look completely reversible. This is, of course, a much harder discovery to have made, but apparently it is true that the fundamental physical laws, on a microscopic and fundamental level, are completely reversible in time!"
    --https://www.feynmanlectures.caltech.edu/I_52.html

    Richard was no dick, apparently.
     
  17. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    YES. But at the atomic level are we talking about, as an example say, a atom with a nominal left spin becomes like its mirror image, a atom with a right spin?

    That is not reversing time

    True. Watch on the screen the egg becomes whole again. But even if possible to perform such action in real life restoring a broken item back to its original state by reversing the process (the numerous stages, actions) which resulted in it changing its state

    Still not reversing time

    In this example you give, my take, to reverse time what I contend needs to occur, the ENERGY expended to break the egg needs to flow back into the egg

    ie you DO NOT use "NEW" energy to put Humphrey together again. You use the energy physics used to break the egg ie reverse it from what it turned into back to what type of energy it was (the energy which was available) to break the egg)

    If you hold the view time does not exist the situation becomes ALL situations (changes) occur in NOW - nothing to reverse

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  18. Write4U Valued Senior Member

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    IMO, it is not so much a matter of complexity (quantity), as an irreversible change on spacetime coordinates. You cannot rewind the movie, the idividual frames have changed position inside the film.....

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    Moreover, once the film is developed can it be undeveloped?

    If time is reversible on an atomic scale, can we rewind the universe back, past the inflationary epoch, to the BB event itself?
     
    Last edited: Sep 1, 2020
  19. Q-reeus Valued Senior Member

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    3,709
    Right but as Davies also writes there "(In practice, the biggest gap between the two curves opened up, not after decoupling, but during the era of nucleosynthesis,...)".
    That entropy gap was and partly remains locked up microscopically, and similarly following the other phase transitions in the early universe. The crucial BSM physics allowing a matter-antimatter imbalance is all that prevented a maximum entropy universe consisting of nothing but diffuse radiation plus maybe 'dark energy' now.
    Finding a natural explanation for all such occurrences is a huge ask and far from resolved.

    I notice no-one has commented on #49. That exotic time symmetry violating process would have no appreciable impact on cosmological evolution but nevertheless is remarkable.
     
  20. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Running a film in reverse is a piss poor analogy

    The individual frames no longer exists

    What has just occurred to me from your post

    In the case of Humpty Dumpty fallen broken egg. Trying to reverse time in / at a local, restricted region would / should be impossible due to the cause / effect effect

    If you are trying to reverse time (at a local and atomic level only) surrounding atoms (outside of the local level) will be still acting under cause and effect of atoms from past atoms

    Soooo
    • will atoms in a local region being reversed (time wise)
    • act on atoms continuing on their (time wise) forward motion
    • as per determined by actions of atoms in their past and
    • by reverse time wise atoms acting on forward time wise atoms
    • reset a previously predetermined future
    • by creating a new cause / effect time line
    OR WILL
    • reverse time line atoms in a local region
    • halt forward time line atoms
    • turning (reversing) the forward time line atoms
    • from cause / effect domino system to a
    • previous effect becoming a cause and a
    • previous cause becoming effect, the
    • ripple spreading throughout the Universe
    • until as suggested by Write4U
    • ........we rewind the universe back, past the inflationary epoch, to the BB event itself?
    Universe simple if time non existent

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  21. Write4U Valued Senior Member

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    According to Bohm you can reverse an action (not going back in time, but in space) and recreate the original pattern. (glycerine experiment).


    But if the time frames no longer exist can they then be recreated?

    I think; "you can go back in time but not in space, and you can go back in space but not in time"...
    ........... "you cannot do both simultaneously except going forward in both space and time"....

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    Last edited: Sep 1, 2020
  22. Write4U Valued Senior Member

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    Accept my apology for not taking a few minutes to check it out. This is a remarkable lecture and right up my alley of a mathematical universe. But also more questions..........

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  23. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    And if you have my belief, time does not exist, you do not move (you stipulated forward), you remain in NOW and changes occur in NOW

    With different atoms? or gather up original atoms and reassemble to make original frame?

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