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What exactly is time

  1. Jul 11, 2015 #1
    I've been thinking about this general concept for months. It became relevant to me when I read in a science book that the "arrow" of time has no preference as to which direction it goes, back or forward. At least in a mathematical form.

    So I began to think about exactly what is time. Finally I reduced my question down to "what is the smallest unit of time in a practical sense?"

    My logic became: time is represented by a change to the status (of the universe or local reference frame or other) from the "instant" that frame changes as to what physically exists now to what exists later.

    My reasoning is that time is always measured by something changing. It may be the tick of Big Ben, or the rise time of a cycle of the frequency of an atomic clock, but it is always a physical change that defines time. The universe is one way now and then it is different, and there ain't no going back. I rather like the concept, it is a amusing thing to think about.

    And yes I have heard of Planck time.

  2. jcsd
  3. Jul 11, 2015 #2


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  4. Jul 12, 2015 #3


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    Staff: Mentor

    Time is what a clock measures, just like distance is what a ruler measures. Anything beyond that is philosophy and inappropriate for PF. Thread locked.
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