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I How does time work?

  1. Oct 31, 2016 #1
    Let's consider freezing time and plotting all the information in a 3d space, with an imaginary (not related to complex numbers) fixed metric. For this we need a reference frame. In this coordinate system we will have all the information about the universe.

    Then we go plot the next snapshot of the universe , in which we get the slightest change possible from the previous snapshot . We can imagine storing these snapshot as they are. Then once every a certain number (can be infinite) of snapshots we can define fixed intervals that correspond to time, intervals. These fixed intervals can be treated as absolute time intervals. This way, time would be an absolute dimension.
    If we go to different frame of reference and do the same thing , will we find a different number of snapshots ? If yes, it means that the frame in which we got a lower number of snapshots was not able to describe the universe. We can find a reference frame that gives us the highest number of snapshots. This frame would be absolute, and all other frames will have less information.
    This frame if reference, I understand would not possible to be found since the real metric space expansion should be infinite.
    Does this make sense ?
     
  2. jcsd
  3. Oct 31, 2016 #2

    Ibix

    User Avatar
    Science Advisor

    You are trying to describe the block universe model. The only problem is that there is no minimum interval of time - it is a continuous thing.

    Basically, choosing a frame in the block universe is analogous to choosing a direction through a solid block of wood and calling it forwards. Perpendicular to that direction is "now" (or sideways in the wood analogy). Someone else is free to pick a different direction and call it time (or forwards) and they have a different definition of now (or sideways).

    The point is that the two people are (conceptually) slicing up the same block in two different ways. Either is fine because spacetime is continuous and they can slice it as finely as they like in either direction. There is no "atomic lattice" that picks out a preferred direction.
     
  4. Oct 31, 2016 #3

    Dale

    Staff: Mentor

    You will not have all the information about the universe. In terms of the Lagrangian you would have all the generalized positions but none of the generalized velocities.

    There is no next snapshot. That idea is incompatible with time being a real number. There is no next snapshot for the same reason that there is no smallest positive real number.
     
  5. Oct 31, 2016 #4

    fresh_42

    Staff: Mentor

  6. Oct 31, 2016 #5
    Velocity looks something artificial. Particles seem to have momentum and continue their motion. We can determine it based on history.
    That is simply basic newtonian motion. But if we take an electromagnetic wave, and analyze the way it propagates, can we tell what is going to happen next, without knowing the velocity ? Anyway the velocity is always known because it never changes. Is momentum the thing that creates time ?
     
  7. Oct 31, 2016 #6

    Ibix

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    Science Advisor

    The speed of light is always known. Velocity, no. A snapshot of a light wave propagating in the +x direction is indistinguishable from one moving in the -x direction
     
  8. Oct 31, 2016 #7

    Dale

    Staff: Mentor

    It doesn't matter if you use Lagrangian mechanics and the generalized velocities or Hamiltonian mechanics and the canonical momenta. Either way you cannot know he state of a system from a single snapshot and there is no such thing as the next snapshot. Your idea simply doesn't work.

    In any case, this thread needs some scientific references before it can proceed further.
     
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