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Time and Change

  1. Jun 12, 2009 #1
    Is change possible without time? Also is time possible without change? What is the correlation between the two and how does time dilation affect change?
     
  2. jcsd
  3. Jun 12, 2009 #2
    Your question is quite vague... what precisely do you mean by "change"?
     
  4. Jun 13, 2009 #3
    By change I mean a state that differs from its previous state.
     
  5. Jun 13, 2009 #4
    Well, yes... but then it depends what you mean by "state".
    Classically, change is something that can only occur over time. The "state" of a system is something you'd describe in terms of the values of fields, or the position of particles, all of which would vary smoothly with time. In a relativistic setting, each spacetime point would have a precise specification of field strengths, particles present at that positon, etc. Time dilation wouldn't really have much to do with it; it's more of a statement about the co-ordinates a person is using to describe spacetime.
    In QM, however, things are different, as we don't have the same causality in operation. State becomes a technical term, and can vary either smoothly with time- as when a system evolves in time as prescribed by the Schroedinger eqn- or instantaneously, as when a system in a superposition of eigenstates of some observable is measured. Schroedinger's description of "these dammed quantum jumps" refers to instantaneous transtions between atomic energy levels, which is not without empirical support.
     
  6. Jun 13, 2009 #5
    A convenient way to think about time and change is from the famous quote

    In general, change is not possible without time; another way to think of that is that space and time and energy apparently emerge from quantum vacuum together...and as soon as they do "change" is also born...

    Time dilation does affect change. For a fast moving space traveler, her time is slowed and that means she actually ages less (her metaBOLISM IS SLOWED) as observed from another reference frame; radioactive decay also slows in such circumstances as does radioactive decay in a strong gravitational potential, say close to a black hole horizon, relative to a weak gravitational potential, say out in relatively empty space.

    But also note that since general relativity and quantum theory are in some circumstances two conflicting theories it's quite possible we have a lot more to learn regarding time....and all the other variables as well for that matter.
     
  7. Jun 13, 2009 #6

    disregardthat

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    "At once" is meaningless without the concept of time, so the quote is ironic. But it hits the spot nevertheless. Change from one state to another can be seen as a series of events. Time is the concept of the order of these events. Change is meaningless withouth the concept of time. Just as shape is meaningless without a concept of space. These are not facts which needs scientific proof; time and space is part of the definition of change and shape respectively.
     
  8. Jun 14, 2009 #7
    If it is a series of events then would I be correct to state that change is stepped? And if so then what defines the boundary between one state to another?
     
  9. Jun 14, 2009 #8

    disregardthat

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    We define the boundary. If we can observe a difference in a situation from one time to another we can say there has occured change.
     
  10. Jun 14, 2009 #9
    How does time affect the boundary? what is the boundary?
     
  11. Jun 14, 2009 #10

    disregardthat

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    I believe your question itself is flawed. How can the necessary medium for the order of any series of events define the difference between the events?

    The boundary is most likely relative to the human observer. A person who looks at a metal plate would not observe any change. (given that the plate doesn't change color) Now, if the person held his hand on this metal plate he would observe a change. The state of the plate would be considered different from what it earlier was. This could be put in rigourus context like the physical definition of temperature and its quantification.

    The perspective of these two events (a cold plate and a hot plate) in a certain order like "the plate was cold, then it became hot" requires a concept of time. This ordering of events is fundamental to our understanding of the world.
     
  12. Jun 14, 2009 #11
    What is any boundary? All energy is bound in the present, if you can think of time not just as the number generated by counting changes as in a clock (local), but more as the function of the changes themselves (global).
     
  13. Jun 15, 2009 #12
    So basically you are saying that change is not stepped because time is not stepped? How do we know that a change has occurred if change is not stepped? If it is then there has to be definitive boundaries between each state of change. Now what is that boundary; and how does time effect that boundary?

    PS: I am not thinking of time as a number but as the "operator"
     
  14. Jun 15, 2009 #13
    Stepped?:confused:
     
  15. Jun 15, 2009 #14
    Well how else can I put it? If change has boundaries between each differing state then change is stepped! Change cannot be analogue!
     
  16. Jun 15, 2009 #15
    Our common accelerated frame earth, dilates relative to all of our proper frames, at a rate of 9.8 meters per second, time like motion? Every part of me knows this except in my mind's eye the photons from all ages that I am processing now denies it. Is this stepped time, I think of it as dilation because it is one thing changing form, larger? The earth appears to be static in my present, but I like to lay out on the lawn and look up sometimes just to see where I am going.:cool:
     
  17. Jun 18, 2009 #16

    baywax

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    It may only be that our view of change is analog and that the change (itself) is a simultaneous collection of events we can only view as being in transition or transformation.

    From our biological stand point it would be fitting (in the survivalist's sense) that we are capable only of perceiving and conceiving of change as a series of transformations with beginnings and outcomes. This could be because the emergent phenomenon of our biological nature is a fragile development that has naturally selected a type of perception that lends itself to our survival.
     
  18. Jun 22, 2009 #17
    You defined change as, "... a state that differs from its previous state", which might be paraphrased as "change refers to an incongruency between two or more recorded spatial configurations of some set of objects", or something like that.

    Anyway, I think I understand what you mean by change, and you seem to be using the word in the standard way -- wrt both ordinary and technical language.

    Time and change are logically related. Time is change (recording time is recording change), but it's also something more. Time is the index(es) of change.

    Time dilation is symmetric. Differential aging is asymmetric and is evidence that accelerations affect the periods of oscillators.
     
  19. Jun 22, 2009 #18

    baywax

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    If my foot is 2 weeks older than my leg does that describe asymmetric time dilation?
     
  20. Jun 27, 2009 #19
    I don't understand your question. :uhh:
     
  21. Jun 28, 2009 #20
    I agree with Muppet and others who say that change and time are inseparable.

    But if it were possible for change to occur "instantaneously", as you suggest is the case for state reduction, or energy-level transitions, then this makes change and time separable. There's a conflict here. Or does "instantaneous" in this context just mean "snap, very fast"?

    There are of course many theorists who claim that time itself is an illusion (See Julian Barbour's The End of Time and also an article rubbishing this claim, namely The Unique Universe by Lee Smolin in the June 2009 issue of Physics World, at physicsworld.com).

    But if time and consequently change were just an illusion, how come life is so much fun to experience?
     
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