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Block Universe / Godel's Paradox / Free Will

  1. Dec 1, 2006 #1
    Hello there,

    Relativity implies that we live in a block universe where both the past and the future are pre-defined--they are alreay out there.

    Time is a fourth dimension, just like space, so it means it exists in both directions--both the past and the future.

    Has the paradox of "frozen time" ever been resolved?

    Do we live in a block universe?
     
  2. jcsd
  3. Dec 1, 2006 #2

    Chris Hillman

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    Hi, autumnwests,

    I am not sure what you mean by "block universe", or precisely what "paradox" you have in mind, but I can recommend some books which I think you will enjoy. First, try Space, Time, and Spacetime by Lawrence Sklar, and second, try Spacetime Physics by Taylor and Wheeler.

    Chris Hillman
     
    Last edited: Dec 1, 2006
  4. Dec 1, 2006 #3
  5. Dec 1, 2006 #4

    Chris Hillman

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    Citations to Wikipedia?

    Hi, autumnwests, did you see my recent post beginning as follows?:

    Notice that last year I was one of the 1000 most voluble contributors to Wikipedia, so it seems safe to assume that I know what I am talking about!

    You might be interested in various recent threads on closed timelike curves (CTCs), which appear in (some regions within) various exact solutions in gtr, These are generally thought to be "unphysical", but this is controversial and some prominent researchers believe that such things might be possible without creating paradoxes. Discussion of this kind of idea tends to be very speculative, however, particularly in popular forums.

    Chris Hillman
     
    Last edited: Dec 1, 2006
  6. Dec 1, 2006 #5
    These paradoxes are well known and talked about in many prominent books.

    I'm not here to debate wikipedia.

    Thanks!
     
  7. Dec 1, 2006 #6

    pervect

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    While it unfortunately requires a visit to the library, "Time in special relativity and its philosophical significance" by Dennis Dieks, is one of many papers that argues against "block time".

    http://www.iop.org/EJ/abstract/0143-0807/12/6/002

    Another paper I stumbled across.

    http://philsci-archive.pitt.edu/archive/00000638/00/kant,_goedel_and_relativity.PDF

    Philosophy isn't really one of my main interests, and these issues are basically philosphical. (You might want to try the philosophy forum for more discussion, but I don't know how much luck you'll have there - I don't read it.)

    I would guess that if you printed them out, the collected philosphical papers on time and relativity would weigh about a ton. I've picked out a couple of semi-random examples, with a visit to the library you can probably do just as well.

    As far as my personal philosophy goes, I think that "simultaneity" is basically an artifact of consciousness. Like most aspects of perception, the preception of simultaneity can be fooled - one can "trick" the brain into assigning events into happening in a different order than they actually occurred.

    People sometimes (often) hang onto this notion of simultaneity well beyond the point where it serves any useful purpose. I think the notion is easily discardable. Basically, I think that light cones describe the causal structure of the universe. I'm not sure exactly which philosopher best represents this position - somewhere in that ton of papers, I'm sure someone has written something close to my own views...

    My meta-philosophical views are that philosphy by defintion doesn't make any testable prediction, so that any non-flawed philosphical position is as good as any other.

    The usual sign of a flawed philosophy is when it makes an actual testable prediction. At this point, something has generally gone wrong - especially when the philsophy is in conflict with scientific observations.
     
    Last edited: Dec 1, 2006
  8. Dec 1, 2006 #7
    I thought that relativity was physics?

    Why are you calling it philosophy?

    Was not Godel a mathematician? Were not his solutions to Einstein's equations math? Is not relativiy a physical theory?
     
  9. Dec 1, 2006 #8

    pervect

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    If you can come up with an experiment or thought experiment that will test for the existence or non-existence of block time, it is a physics problem.

    If you can not come up with a way to resolve the question by experiment, it's a philosophical problem.

    If you look at the title of your post, the words "free will" ought to be a largish clue that you are interested in philosophy, not physics.
     
  10. Dec 1, 2006 #9
    So simply, if as physicists we (currently) trust relativity, we are bound to assume (for now) that we do indeed live in a block universe.

    There shouldn't be any "frozen time" paradox, since we are beings inside the universe (rather than observing the manifold from outside). Perhaps you should check Huw Price's Time's Arrow book, for philosophical block-universe references.

    As for free will.. relativity, like classical mechanics, implies everything is deterministic. No new issues, so you should be able to find resolutions in plenty of texts written since Newton.

    I've never heard the grandfather paradox attributed to Godel; he has much more interesting issues attached to his name. Nonetheless..

    Pure GR theory permits wormholes and closed timelike loops. (Admittedly, the nature of available matter-energy, or some better theory - perhaps quantum gravity - is quite likely to forbid time travel.) Therefore we might be able to experimentally observe situations where, for example, a bowling ball spontaneously falls out of the (uh..) tail of a wormhole with exactly the right velocity to knock a nearby (suspiciously identical) bowling ball into the mouth of the wormhole.

    You could disprove block-time by travelling back to prevent your father's conception, whereas block-time predicts that you would change your mind, or be foiled somehow, or even turn out to be your own grandfather.
     
  11. Dec 1, 2006 #10

    Chris Hillman

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    Hi, Cesium,

    It seems that I commented on this even before you posted it--- how appropriate! See
    Similar caveats apply to "warp drives"/"wormholes" and to such classical "predictions" as the "wave of death":

    Chris Hillman
     
    Last edited: Dec 2, 2006
  12. Dec 1, 2006 #11

    vanesch

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    There is a thread going on about this issue in the philosophy forum:

    https://www.physicsforums.com/showthread.php?p=1176709#post1176709

    (it is of variable quality, but I think that the OP's subject is exactly the one of that thread).

    BTW
    Thanks, pervect, for the great article you provided a link to. I think I'll throw it in on the other thread...
     
  13. Dec 2, 2006 #12

    pervect

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    I don't think everyone would agree with that statement. Certainly Dieks argues against block time in the first reference I quoted - you can see that from the abstract.

    Time travel is still being debated within the literature of GR. I don't think its yet been proven to definitely arise from "pure GR". I think the best one can say is that it hasn't been ruled out yet, that it remains a possibility.


    OK, this is at least testable, so it is to some extent physics and not pure philosophy, though its far out enough that it is in no danger of actually being tested in the near future :-).

    One thing that I think is interesting is to view the situation from the viewpoint of the other people on the Earth. They are going to see either a "quantum vacuum flucutation" or "someone froma parallel world" (your choice as to the best description) come out from the time machine, and commit murder.

    It would seem that a lot of strange things and possibly dangerous things could come out of a time machine in such a world, if this model is correct.

    Of course, if they realized this, there might be security on the other end of the portal (assuming there is a portal). So perhaps the experiment wouldn't be so clear-cut after all - if you go through a portal, with the intention of mudering your grandfather, and get stopped by security on the other end, you haven't either proved or disproved block time.

    A few more observations in general:

    If time travel is humanly possible at some time in the future, where are all the time travelers?

    If you could go back anywhere in time (and not just through some wormhole), why isn't the present (their past) clogged up with time travellers?

    It's possible that time travel is possible, but the human race wipes itself out before it achieves it (which is rather a bummer). It's possible that time travel requires a specific receiving terminal (as in the wormhole model) that hasn't been built. It's possible that time travel is occurring, but that the people from the future are just being very careful not to reveal themselves, I suppose. It's possible that time travel is not possible.
     
    Last edited: Dec 2, 2006
  14. Dec 2, 2006 #13

    pervect

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    Thanks! Did you like the Dieks paper ("Time in special relativity and its philoophical significance") or the Dorato paper (Kant, Godel and Relataivity)?
     
  15. Dec 2, 2006 #14
    Someone somewhere put forward the interesting suggestion that all of the Biblical prophets were time-travellers.

    How else could Jesus heal the sick? Moses cross a river? Joseph predict the famine? etc. etc.

    N.B: I do not currently have any opinion on the validity of time travel.

    edit: Sorry, I realised that this is completely non-physics, and apologise for that, but still feel it is a relevant comment on a part of the post.
     
    Last edited: Dec 2, 2006
  16. Dec 2, 2006 #15

    selfAdjoint

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    Magic? Power of the Most High? Fakery? Phoney story? Any or all seems more plausible than time travel. After all, soimeone who could do a fair selection of those things, and really do them, over and over again to prove it, would be treated as a wonder-worker even today. And so your sources are not just positing time travel, but also a future civilization where those things are 'science" or maybe "technology". That's an improbability two-fer.
     
  17. Dec 2, 2006 #16
    If you accept that these stories were most likely highly exaggerated, then they wouldn't necessarily be seen as wonder-workers. Modern medicine, predicting astronomical events etc. would appear as magic to most ancient peoples.

    Anyway, this is definitely non-physics, and I don't propose this as a real hypothesis anyway, so this is my last post on the matter.
     
  18. Dec 4, 2006 #17

    Demystifier

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    I still do not understand what do you find paradoxical about frozen time and block universe.
    According to this paradigm (which I strongly support) the flow of time and free will are illusions. I see nothing paradoxical about that. Can you specify by your own words what exactly do you find paradoxical?
     
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