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I What is time?

  1. May 10, 2017 #1
    First of all, it's not intended to be a philosophical question, but rather a physical one.

    So, what can we say about time? Maybe, it's a human way of measuring how things evolve in space?

    Suppose there are a room with objects within it, where nothing ever happens. There's no need to talk about time, because things don't evolve. Now if YOU, or whatever real physical object is inside that room, it probably would be convinient to you to talk about time.

    Note that I'm not trying to restrict what time is in the above, just wondering if this could be accepted as a way of defining what time is.

    Is there anything wrong with the above argument?
  2. jcsd
  3. May 10, 2017 #2


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    It's hard to keep this apart from philosophy.

    As soon as you have "something" in that room, you have energy and motion. Even the definition of the room is already such a something. So time is physically what a clock measures, or mathematically a dimension of the universe. In return this means, you can under certain circumstances do physics with only spatial dimensions as you can deduce certain properties of a geometric object from a projection alone. This might not be satisfactory from a philosophic point of view, but for the exploration of nature it is, in my opinion.
    Last edited: May 10, 2017
  4. May 10, 2017 #3


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    As a physical question, it's hard to improve on Einstein's "Time is what a clock measures". Although you may dislike this answer, it's a good idea to try to understand exactly what Einstein meant by it - even if you don't come to appreciate it more, the effort will clarify your own thinking no end.
  5. May 10, 2017 #4


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    This sentence is incompatible with this one
    How can you claim you want to have a physical discussion when in the very next sentence you posit that time is "a human way...".

    Which do you want to discuss, the physical or the philosophical?
  6. May 10, 2017 #5


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    Quarter past five. :wink:

    I think, given that we generally model time as a length or an extent in one dimension, it might be instructive to think about "what is distance" as well. I have nothing better than the obvious analogue of Einstein - what rulers measure. But if you think about what you might consider an acceptable answer to that question, it might help inform your thinking.
  7. May 10, 2017 #6
    I dont understand why this is problem. We define time by the way we measure it. Why is not physical?
  8. May 10, 2017 #7


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    Time is the thing measured by a clock. A clock is human made, the thing measured by a clock is not.
  9. May 10, 2017 #8


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    Closed pending review

    Edit: upon review the most recent post has been deleted and this thread will remain closed
    Last edited: May 10, 2017
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