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Block universe theory

  1. Jan 13, 2012 #1
    Hi,guys,What is evidence against and for block universe theory?
     
  2. jcsd
  3. Jan 13, 2012 #2
    Did you check wikipedia? Assuming what I found is what you are talking about, this seems like philosophy not science.
     
  4. Jan 13, 2012 #3
    yes,i did some research and it says that block universe or eternalism is not compatable with relativity or quantum gravity.
     
  5. Jan 13, 2012 #4
    Well I don't know any details, but not being compatible with GR or Quantum Theory is a big no-no.
     
  6. Jan 13, 2012 #5
    This has been the subject of a number of threads here. A recent one is found here:

    https://www.physicsforums.com/showthread.php?t=561344

    However, this discussion focused also on the nature of the 4th dimension and was eventually locked for straying too far away from physics into philosopy.

    The block universe concept is actually embraced by quite a few physicists, although the issue is just not on the radar for most physicists. Einstein, Weyl, and Godel were three of the more renowned physicists who are referenced as embracing the block universe concept. I think most physicists would agree that the block universe concept is as a minimum at least consistent with special and general relativity. Weyl described the situation this way in one of his lectures:

    "The objective world merely exists, it does not happen; as a whole it has no history. Only before the eye of the consciousness climbing up in the world line of my body..."

    I don't think it would be accurate at all to claim that the block universe is not compatible with relativity. After all, it's the unusual circumstance of the different 3-D cross-sections of a 4-D universe for observers moving at different relativistic velocities that motivates the block universe concept. The sketch below shows a basic consideration in forming the block universe concept. At face value it would seem that a 4-dimensional universe would be needed for the situation depicted here to be physically possible. A 4-dimensional universe ("block universe"--it's all there at once) populated by 4-dimensional objects is implied. The 4-dimensional world lines of objects may extend for billions and trillions of miles along 4th dimensions in the rest frames of the various objects.
    BlockUniverse_Motivation.jpg
     
    Last edited: Jan 13, 2012
  7. Jan 13, 2012 #6
    so your saying that you believe in a block universe?
     
  8. Jan 13, 2012 #7
    so that is evidence for block universe,what would be evidence against?
     
  9. Jan 14, 2012 #8

    Dale

    Staff: Mentor

    This is incorrect. In fact, the block universe concept fits very naturally into the geometric interpretation of relativity.

    In principle, the block universe concept fits naturally into any completely deterministic physics theory.
     
  10. Jan 14, 2012 #9
    I think DaleSpam summed it up quite accurately. The evidence usually cited against the concept is that it runs contrary to our personal experience. Our direct experience is tied to a 3-dimensional world that evolves with time; we are deeply engaged in the development of events. Our free will is a dominant aspect of our existence, and this seems to be questioned under the block universe scenario.

    Notice that DaleSpam used the term, "in principle." And that's the appropriate way to state it, because although block universe is an interpretation consistent with special relativity, that does not mean that it is necessarily proven as the actual way the universe is--even though it may seem to be implied.

    These considerations quickly get into the philosophy of reality, a subject that most physicists begin to back away from and turn over to the philosophers. You can find papers about the block universe in the philosophy literature, but I have never seen a paper in Phys Rev on the block universe (although I've really not done an exhaustive search and haven't been following the physics literature for quite a while).

    There is a book, "Mind and Nature", which collects together selected writings of Hermann Weyl (his quotes that I have used on the forum come from this book). He writes about consciousness, etc., but I don't think that even he actually published those kinds of ideas in the formal physics journals. Other physicists have written about it in popular book form--but not in the formal physics journals.

    I personally don't really know what to make of the block universe. I do not know how to refute it on a strictly theoretical basis. I think Weyl's idea of the "...consciousness climbing up in the world line of my body." leads to a bizarre situation with zombies--4-D bodies leaving 3-D cross-sections without a consciousness for the 3-D cross-sections of other observers who do not share the same proper time (the moving consciousness is only 3-dimensional while the body is a 4-dimensional structure in his description). Notice that, in the twin paradox, each twin is a zombie for the other at the event of their world lines reuniting, because they arrived at that event at different proper times. This is such an obvious result, I can't imagine why Weyl never mentions it.

    It is for this and other reaons that I am personally repulsed by the concept--but again, do not know how to refute it. Other physicists seem to avoid Weyl's zombies by having the consciousness coupled with matter over the entire extent of the world line.

    But now we're teetering (actually, already crosssed) the boundary of appropriate discussion for this forum.
     
    Last edited: Jan 14, 2012
  11. Jan 15, 2012 #10
    bobc2, this is almost like what i asked for in my previous thread https://www.physicsforums.com/showthread.php?t=566430
    but i have a doubt if there is only one time axis for all the observers they would age the same after separating and re-uniting isn't it?you can easily prove this by calculating the resultant vector along the time axis and it will turn out to be the same for both twins however this is not the case in reality. please point out where i have gone wrong
     
  12. Jan 15, 2012 #11
    I see your point, Snip3r. However, when you do your proof, it seems like you are not using the hyperbolic calibration curves for keeping track of proper time for each observer. I had just a second to jump in here and maybe can come back tomorrow, but someone else can probably clarify that for you.
     
  13. Jan 15, 2012 #12
    bobc2,is your view towards eternalism?
     
  14. Jan 17, 2012 #13
    Your question is about external physical reality. A really good physicist, Bryce DeWitt (deceased--Univ. of North Carolina, Chapel Hill), once wrote in a Physics Today article, "There is more to reality than physics." I think that to make a complete and final statement about the reality of the block universe (eternalism), you must include a theory of consciousness as well as a more definitive concept of time at a fundamental level.

    Consciousness and a fundamental concept of time are not yet subjects of theoretical physics. I don't see how I could come to a final world view of external objective reality without an understanding of consciousness and time.

    Tentatively, the block universe concept seems to be consistent with relativity. And QM concepts such as "Many Worlds" don't seem to rid us of the block universe (we just seem to have more of them). So, technically I'm not able to refute the block universe concept; yet there are deep mysteries about reality that don't seem to have promise of resolving. And I don't think that physicists or philosophers have plumbed the depths of the full implications of the block universe--for one, it would appear to bring theology prominently into the mix.

    These are some of the reasons that pursuit of the block universe topic is probably not appropriate for this forum.
     
  15. Jan 17, 2012 #14

    Dale

    Staff: Mentor

    Thanks bobc2, that was well done.
     
  16. Jan 17, 2012 #15
    Quite a compliment coming from one of our leading contributors to this forum. Thanks.

    Please, don't anyone look to me as any kind of authority on these or any other special relativity topics. After a short stint at teaching at the undergraduate level, all of my work in industry has been in a fairly narrow niche of classical physics. Special relativity, elementary particles and QM are hobbies.
     
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