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Time and motion

  1. Oct 31, 2006 #1
    Is there the notion of time in a motionless world? I just feel time because things change. Is this a wrong idea? What's your opinion?
  2. jcsd
  3. Oct 31, 2006 #2


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    I suspect that this might belong in Philosophy. My personal opinion is that as long as there's space, there's time. Matter isn't necessary, but of course there's no way to detect the passage of time without matter in some organized form.
  4. Oct 31, 2006 #3
    Try to define the meaning of the word "motionless". Then you have the answer to your question.
  5. Nov 1, 2006 #4


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    It depends upon the paradigm in which you work. Clearly, we humans, have a "sense of change" which we call time. In a Newtonian view, this corresponds to some physically existing "universal time" out there: a kind of universally distributed "clock signal" which pervades the universe or something of the kind, so time (and especially its "flow") is a physical phenomenon.
    However, in general relativity, this changes: time is just a coordinate, as is x,y, and z, from the PoV of an observer, over a "block universe" in 4 dimensions, which, itself, is timeless. In other words, past, present and future are all "equally real" and it is just the observer which travels on its own world line and experiences a certain slice of this 4-dim block world as his "now". And then, there are interpretations of general relativity which refuse this "block world" view too and tend to instore a more "Newtonian" view.
    So in how much the "flow of time" is a physical phenomenon, or a subjective perception, is not clear.

    The two visions have often affronted eachother: the "dynamical" view (the time flow is a physical phenomenon) against the "geometrical" view (all times "exist" and we only subjectively wander through it)

    Of course the *time parameter* is physical in many senses.
    If you want to read about these notions, which are on the borderline of philosophical considerations and foundational physics, look at Zeh's book "Time".

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