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Time's arrow, or what universal property is asymmetric, anyway?

  1. Mar 20, 2004 #1
    "Time's arrow, or what universal property is asymmetric, anyway?"

    A lot has been made of time's arrow not appearing in the equations of Newton, statistical mechanics, relativity and quantum mechanics - none preferring that past precedes the future or vice versa. Some very specific particle processes do seem to follow an asymmetry of time, but they are the far greater exception for interactions in general.

    We ask if time as a universal property has a preferred direction. I ask if any cosmological phenomenon has been shown to obey an overall physical vector.
     
  2. jcsd
  3. Mar 20, 2004 #2
    That's like asking whether or not centimeters have a preferred direction. Time does not exist , just as centimeters do not exist .
     
  4. Mar 21, 2004 #3
    Can we then conclude that physics does not exist, or just that vectors ultimately have no global meaning?
     
  5. Mar 21, 2004 #4

    Actually, time really does exist. There is a reason why we use the term "spacetime"

    Time is a element of the universe, just as our 3 physical dimentions.
     
  6. Mar 21, 2004 #5
    That's what some people think, but I really don't believe it at all. Time is something humans invented, just like any measurement system.
     
  7. Mar 21, 2004 #6
    Think quick! The Temporal Conspiracy has been uncovered!
     
  8. Nov 22, 2008 #7
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    What are you saying? If BasketDaN thinks that time or centimeters do not exist, than don't you think that giving evidence that these things have physical existance as independent units that exist on their own would be a more appropriate response?

    What you did say really did not clear up the issue. Don't you agree.

    As for the existance of time, I too agree with BasketDaN. Time is not a physical thing, it is a human concept.


    Every measurement of time is based on what man decided that measurement to mean. Seconds, minutes, hours and so on are all man made. Time did not come pre-packaged in these units, man agreed on what to call these durations. Clocks measure how much of a pre-determined man made unit passed for a given motion. If something takes a minute of time, then that activity lasted for what man determined to be a minute. Time is the concept of man.

    If you disagree with this please feel free to provide evidence of the physical nature of time.

    Some observation or scientific reference that provides proof beyond a reasonable doubt that time is a physical thing would be nice.

    Thank You.
     
  9. Nov 22, 2008 #8
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Exists in what form?



    When you say time is an element of the universe do you mean time is one of the chemical elements? Can you be more specific in what you mean by element.

    As for dimensions, are you saying that these too are chemical elements?
     
  10. Nov 22, 2008 #9
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    The one thing people will agree on is that most current theories use time or space-time somehow. Now time/space/space-time may exist or may not, but nonetheless these are useful in these models. This is all we really can agree on at this time.

    If you have an idea like "time does not exist" check out the consequences of that hypothesis and form a testable theory (the term "Testable theory" is a bit redundant I suppose).
     
  11. Nov 23, 2008 #10
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    That's incorrect. A random variation is statistically more likely to produce a less ordered state rather than a more ordered state. This can be proven mathematically, and from it the third law of thermodynamics (the arrow of time) follows. (The remaining mystery is only why the universe should have been destined for so improbable a state at what we call its beginning, since it seems a much less improbable one would have sufficed to produce agents such as us.)
     
  12. Nov 23, 2008 #11
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    It does appear in statistical mechanics as entropy. It also seems to make an implicit appearance in quatum mechanics. Edit: btw, I left out CPT symmetry.

    As for the rest of these posts, existance is a philosophics topic, and as argued here, one in need of symmantical help.
     
    Last edited: Nov 23, 2008
  13. Nov 23, 2008 #12
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    John 8,

    Remember your Planck units, of which Planck time (=1.616... x 10^-33 cm) is one. It is not man made as much as a massless, radiative, natural measurement.
    _________

    For you statistical mechanics, time as you describe it would seem not absolute, but according to Clausius have a nonzero (albeit diametrically unequal) probability of either going "forward" or "backward." At least that's how I interpret it.
    __________

    Phrak,

    What is the take on CPT asymmetry, anyway? Is it a local or global property?

    How about this time asymmetry in quantum mechanics you mention?
     
  14. Nov 23, 2008 #13
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"


    Max planck was a man. This man established a measurement. Planck time would be man made.

    Do you think time is a physical thing of some sort?
     
  15. Nov 23, 2008 #14
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    If time is not exist, how can it will be twin paradox phenomena? Gravity can changes times, so why shouldn't time is physical?
     
  16. Nov 23, 2008 #15
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    I don't see much discussion following the original question.

    Can any cosmological phenomenon be shown to obey an overall physical vector?
     
  17. Nov 23, 2008 #16
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Going back to the OP:

    I think time's apparent asymmetric nature was locked in at the moment of the big bang, and therefore; time is not reversible. To turn the clock back one would have to somehow overcome the force and direction to which symmetry broke at the BB. However i dont think time exists in any objective form other than it being a "sense" of our reality. To me it appears as a sort of directional bias of which we are aware because - after all - we too are products of this same universe. Our sense of time is deeply affected by the movement of large astronomical bodies like the sun and moon etc..So it serves a handy way to measure the interval between various movements, and as we've evolved we use "time" to organise our lives in a more efficient manner.

    There is no way to keep time unless there is a physical universe which contains things that are moving to which we can set our time.
     
  18. Nov 23, 2008 #17
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Yes, the cosmological phenomenon we call gravitation.
    All mass gravitates and all mass gravitates in the same direction - toward mass.
    If you are looking for a vector that is a universal physical constant, that would be it.
    If you are looking for an absolute vector, there are none, as gravitation is a three
    dimensional force.
    The day any mass moves away from another without being persuaded to do so by some force other than gravity, will be the day the gravity vector reverses and time will be reversed.
     
  19. Nov 23, 2008 #18
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Unfortunately, gravitation is time symmetric. Eliptical orbits are still eliptical orbits with t is replaced by -t. To make things easy, just think of running the film backwards. You still see the Earth orbiting the sun and nothing appears amiss.

    Though, orbital decay is the result of friction. Friction is a thermodynamic process.
     
  20. Nov 23, 2008 #19
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    You bring up a valid question. So why don't you start by tell us in your own words what your idea of time is, I think this will help answer your question.

    I say time is actually a consideration based on our perception of the movement of objects. There is a distance, there is a velocity of the objects travel, and that movement of that object or particle in relationship to its starting point and in relationship to its ending point is what gives us the idea of time. Time is a manifestation which has no existence beyond the idea of time brought about by the motion of objects, where an object may be either energy or matter. Time is not a thing that flows. Time does not move or cause things to move. It is this perception of motion which gives us the idea of time.


    What do you think?
     
  21. Nov 23, 2008 #20
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Hi Coldcall. After reading the above post I thought that I would see if you can sort out what you are trying to say about time. I will just take your statement and handle one section at a time.

    Here you seem to sugest that time was created by a supernatural explosion, the Big Bang.


    Here you say time does not exist in any objective form. It is some sense. So what is it? Something created? Or some concept or sense?

    I only ask you this so that I can understand what you are trying to say.

    I will agree with your idea that our concept of time is due to the motion of things around us.


    Time is actually a consideration based on our perception of the movement of objects. There is a distance, there is a velocity of the objects travel, and that movement of that object or particle in relationship to its starting point and in relationship to its ending point is what gives us the idea of time. Time is a manifestation which has no existence beyond the idea of time brought about by the motion of objects, where an object may be either energy or matter. Time is not a thing that flows. Time does not move or cause things to move. It is this perception of motion which gives us the idea of time.
     
  22. Nov 23, 2008 #21

    Dale

    Staff: Mentor

    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    :rolleyes: following this same train of thought:

    "Every measurement of mass is based on what man decided that measurement to mean. Kilograms, slugs, tons and so on are all man made. Mass did not come pre-packaged in these units, man agreed on what to call these amounts. Balance scales measure how much of a pre-determined man made unit balances a given object. If something is a kilogram of mass, then that object balances what man determined to be a kilogram. Mass is the concept of man."

    Do you really think that mass is not physical? If not, then how is your logic plausible for time if it is so obviously not plausible for mass?
     
  23. Nov 24, 2008 #22
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    John8,

    "Here you seem to sugest that time was created by a supernatural explosion, the Big Bang"

    Supernatural? No I dont think i classed it as supernatural. But yes, as it stands at the moment, it appears the BB started off the universe. Or at least its the best theory that fits in with our current observations about the state of the universe.

    "Here you say time does not exist in any objective form. It is some sense. So what is it? Something created? Or some concept or sense?"

    No I dont think its been created as such; more like an emergent property or by-product of a universe in motion. I think Einstein's take on "time" is probably the most accurate we have at the moment in that space and time are sort of a combined property. Without "space" there cannot be "time", as there would be no measurable intervals in a universe with no space for movement to occur.

    Basically without the properties of physical velocity and position there would be no "time". But "time" as we understand the phenomenom plays a vital role in biological complexity, and human ability to self-organise. So while "time" is a by-product of the physicality of the universe or our reality, we as intelligent animals have used that emergent property as a useful tool to organise.
     
  24. Nov 25, 2008 #23
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    While I understand you're efforts to understand, and I've gone over this same emergent idea as you have, you have to be careful.

    How can time emerge? Was it absent at one time, to appear later after some previous cause? The argument doesn't really hang together well.

    It's rather frustrating in the English language doesn't provide the verb structure required to made concise and definitive statements about these things, that don't sound meaningless.
     
    Last edited: Nov 25, 2008
  25. Nov 25, 2008 #24
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    Phrak,

    Well I am of the school that believes "time" did not exist before the universe was created. Without any "space" for things to move around in there is unlikely to be "time".

    So in essence "time" emerged with the birth of the universe.

    It may not hang together all that well but it beats the idea that "time" existed before the birth of the universe.
     
  26. Nov 25, 2008 #25
    Re: "Time's arrow, or what universal property is asymmetric, anyway?"

    The physical processes that equations of motion are applied to are, for the most part, afaik, irreversible. Nature, afaik, isn't rewindable. An equation of motion is just a mathematical template that can be applied to the evolution of any physical system that it's appropriately associated with. And, insofar as it describes the evolution of a system, then it is, in that instance of use, describing an arrow of time.

    Afaik, all natural processes evolve asymmetrically. The arrow of time might be a bit easier to see in some than in others.

    Yes, there seem to be some good reasons to believe that the universe is expanding, that its contents are dispersing and dissipating, and that it is evolving toward equilibrium.

    I think so, but you should ask the astronomy and cosmology people about this.
     
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