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Do the past and future exist?

  1. Feb 27, 2009 #1
    Does time exist as a physical dimension like the spatial dimensions. And if it does are objects extended 4 dimensional (or higher if you believe the relevant theories) structures or do they move through time?

    Or is time modeled as a dimension a mathematical convenience and what we really have is spatial dimensions and the effect distortions of spatial dimensions (gravitational/from the pov of different reference frames etc) have on the passage of time?

    What is the consensus and why?
     
    Last edited: Feb 27, 2009
  2. jcsd
  3. Feb 27, 2009 #2
    Before anyone answers this question there has to be a consensus definition of exist, time, physical, and dimension. I'll take a swing:

    Exist: Shape and location
    Time: Relative motion
    Physical: Shape
    Dimension: Extent of an object in a direction perpendicular to each other mutually perpendicular direction

    Therefore time does not exist because motion does not have shape. You cannot be "in" the future like one is in a box or a room.
     
  4. Feb 28, 2009 #3
    This isn't physics. This is grammar. Though it is nice to be grammatically correct.
     
  5. Feb 28, 2009 #4

    CRGreathouse

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    Those schools of thought are, respectively, perdurantism and endurantism. (The latter has another common name, but I can't recall it at the moment.)
     
  6. Feb 28, 2009 #5

    CRGreathouse

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    It's neither grammar nor physics; it's metaphysics -- more precisely ontology.
     
  7. Feb 28, 2009 #6

    epenguin

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    Not now.
     
  8. Feb 28, 2009 #7
    Perhaps so, but when the correct verb tense is applied, most of the metaphysics vanishes.

    There is no future. There will be a future.
    There is no past. Thre was a past.
    Time does not exist. One ordinate in time exists.
     
  9. Mar 1, 2009 #8
    I agree. The words, time, past, present and future all have physical referents. TIME refers to indexes of spatial configurations. If the index is ordered using, say, the integers, then assuming an index of a set of 100 'snapshots' of some part of the universe, with each snapshot depicting a unique spatial configuration, and the members of the set numbered 1 to 99, then arbitrarily choosing some snapshot, say 43, then snapshots numbered <43 correspond to PAST, 43 corresponds to PRESENT, and >43 correspond to FUTURE.

    In real time, or psychological time, the PRESENT corresponds to the highest 'numbered' sensory data indexed by the brain, the PAST is lower in the order, and the FUTURE is imaginary, projections based on PAST and PRESENT.
     
  10. Mar 1, 2009 #9
    This is true in an epistemological sense, but it may or may not be true ontologically.
     
  11. Mar 11, 2009 #10
    If the future already exists, is that the same as saying the universe is deterministic?
     
    Last edited: Mar 11, 2009
  12. Mar 11, 2009 #11

    apeiron

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    A way out of the paradoxes here is to recognise a distinction between the crisp and the vague. So the future may crisply exist (being crisply determined by its past events). Or it may only be vaguely determined by what has gone before. So, much like our vision towards the horizon, near term, everything seems crisply predictable. Further away, it all becomes blurred and hazy. And far enough away, it is pretty much undetermined.

    Prigogine's book, The End of Certainty, is a good starting reference for this line of argument.

    The other key ingredient in the time story I believe is Cramer's transactional interpretation of QM - or simply just taking quantum eraser and other such cases seriously.

    This would argue that the future does exist in a quite concrete sense - for micro-events. The other end of an interaction has to be established for an event to "coalesce" into classical existence. So for your eye to absorb a photon from a distant star, this involves a nonlocal (or rather global I would say) interaction across both space and time.

    This crisp micro-events level story actually fits neatly into the global "it all goes vague with distance" view of the overall flow of time. It is all about scale.

    On the smallest scale, there is really "no time" as the start and end of an energy exchange "happen together" so far as we are concerned from our middleground, classical, observational scale. After all, photons travel at the speed of light and their experience of time would be "frozen".

    Then on the largest scale, a global one-way or irrevesible flow of time is being created. This is not a dimension as classically imagined (crisply linear to infinity) but instead this kind of moving cloud of certaintly/uncertainty. Close to the "now" things look fairly crisp and densely woven (either looking back to the past or forward to the future). Then further away, again in both directions, the crisp determinism gives way to vague uncertainty (and hence also, creative possibility).

    It is a kind of event horizon effect, but smudged rather than a sharp cut off. From (vague) memory, Prigogine did calculate the drop-off in visibility rate. I suspect it was powerlaw rather than exponential.
     
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