Time

Discussion in 'Physics & Math' started by rustyw, Feb 15, 2010.

  1. rustyw Writer Registered Senior Member

    Messages:
    42
    Hello,

    The Big Bang supposedly set matter and energy (the four known forces) in ‘motion’ causing ‘events’. A simple example: elements of the electroweak force holds an egg on the surface of a table while the mass of the Earth warps space and accelerates the egg while pulling it towards the center of the Earth. The sun warms the air which causes wind which pushes the egg off the table and it splats on the floor. Or something like that… you get the idea. These events take place because of physics.

    The longer I study cosmology and quantum physics and despite reading a growing amount of material on the subject… the more that I see… no reason, value, proof or purpose for overlaying what seems more and more like an imaginary construct over the natural procession of events. Perhaps someone can help me out here for I’ve lost my belief in ‘time’. Now wait… there’s more…

    I’ve read that ‘time’ proceeds slower and faster depending on speed or the warping of space – no, the physical events of the universe proceed at different speeds. I’ve read that physics is transparent to the ‘arrow’ of time – that if the atoms of that spattered egg could be sent back at the exact reversed angle and speed that the egg would come back together, rise to the table edge and roll back to where it started. This is probably mostly a true statement but what physical law would launch those atoms (or does ‘gravity’s force reverse with the so called reversal time’s arrow) and what law of physics would bind the broken shell back together?

    In fact it seems to me that if ‘time’ did exist, then physics would not exist because if time does exist that means that there is the possibility that it can stop and what physical laws and forces would we have then? None! It means that there is the possibility that times direction can reverse and as discussed above, that means that our physical laws go whacko and broken symmetries can rebind -- not to mention that the 2nd law of thermodynamics is reversed and broken.

    The physical forces move forward on their own, they don’t need time. However…

    Every ‘far better mind’ than my own absolutely believes that ‘time’ exists so, I must be missing something. Help me out here. Give me one reason, test, or principle that indicates that there is such a thing as TIME.

    Cheers,
    Rusty
     
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  3. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Time is scalar. Motion involves vectors like distance, direction, speed, etc. Space and time are coupled in the relativistic coordinate system so motion is a sequence of events in spacetime. If there is motion like you describe then time is passing in spacetime.
     
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  5. Stryder Keeper of "good" ideas. Valued Senior Member

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    The usual statement is "Time Doesn't Exist".

    Time is a construct or function created by measuring change, change is the only thing that gives time meaning. I mean if you had an empty box that was sealed, time would only march on because an observer outside the box noted how long he kept the box sealed, if there was no observer then their would be no measurement of time passage. Time would therefore cease to exist. (I guess the old metaphor "If a tree falls in a forest and no one is around to hear it, does it make a sound?" could be queried.)

    As for the measurement method, there is no limit to the subdivisional size that can be made of time, so there is therefore no technical instance. This is for the implied reasoning of it being "Scalar".
     
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  7. prometheus viva voce! Registered Senior Member

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    None of these things are vectors. You are thinking of displacement and velocity. Direction is one property of a vector. Other examples of vectors are force and acceleration.


    Space and time are not "coupled." Together they form a 4 dimensional pseudo Riemannian manifold we call spacetime. Also, one does not require motion to define time.
     
  8. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    6,677
    http://www.grc.nasa.gov/WWW/K-12/airplane/vectors.html

    Vector quantities include direction and magnitude, i.e. velocity, acceleration, momentum …

    http://en.wikipedia.org/wiki/Spacetime

    "In physics, spacetime (or space–time; or space/time) is any mathematical model that combines space and time into a single continuum."

    And BTW, motion requires time.
     
  9. cosmictraveler Be kind to yourself always. Valued Senior Member

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    If time doesn't exist then why do we make these?

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  10. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    This is certainly not right from the standpoint of general relativity. This is the same as saying ``space doesn't exist''.

    Again, this is not quite correct in the general relativity sense of the word. Time is a component of a four-vector, not a scalar. We measure distances in space-time:

    \(ds^2 = c^2dt^2 - dx^2-dy^2-dz^2\).
     
  11. MikeO Registered Senior Member

    Messages:
    46
    From what I understand, Einstein's first big SR breakthrough came
    by insisting on this OPERATIONAL definition for time:

    Time is that which is measured by clocks.

    No clock; no time.
     
  12. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    Fortunately for us, Einstein didn't quit doing physics in 1905.
     
  13. MikeO Registered Senior Member

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    46
    Fortunately for us, the "No clock; no time." line was mine and not Einstein's.
     
  14. alinko Registered Senior Member

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    44
    and what about the sun dosent that also measures time, and as the moon too, isnt it always in cycle?
     
  15. rustyw Writer Registered Senior Member

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    42
    LOL, well that's what I meant or, more specifically 'time as a dimention which has a real and substance entity of its own--i.e. which can be ran backwards --doesn't exist' (speed and warped space can slow down the speed of events).

    I believe that I agree with all of that (except I personally believe that 'the tree still falls and that it still generates sound waves'... the interaction of the physical forces continues whether someone is there with a watch or not -- atoms move with in the box and so on.

    Do you believe that this is all that Einstein meant? Its been 34 years since I read his S/GR... perhaps I need a refresher.

    r
     
  16. rustyw Writer Registered Senior Member

    Messages:
    42
    I guess a lot depends on one's definition of time--if your definition of time is the continued (and past) interactions between the physical forces then I agree. Anything beyond that... I don't see the logic in your statement (but I'll listen).

    Same reply.

    r
     
  17. rustyw Writer Registered Senior Member

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  18. rustyw Writer Registered Senior Member

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    So your definition of time is motion... and one might just as well say that 'Space and motion are coupled in the relativistic coordinate system so motion is a sequence of events in spacemotion. Sorry, I'm not trying to be funny. Actually 'time is scalar' is going over my head -- I see another reply to you and your response, let me look more at these and get a handle on that statement.

    r
     
  19. prometheus viva voce! Registered Senior Member

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    Yeesh, that doesn't give me too much confidence in NASA's ability to perform it's function. As it says at the top of the page, "A vector quantity has both magnitude and direction," so direction on it's own is not a vector. You can think of a direction as an angle and an angle is a scalar.

    NASA is plain wrong about distance too (not the first time NASA has been caught in a very embarrassing elementary mistake.) Check out this page. If you're too lazy to read that page let me quote the relevant sentence:
    • "Let's clarify by defining each of these words more precisely. Distance is a scalar measure of the interval between two locations measured along the actual path connecting them. Displacement is a vector measure of the interval between two locations measured along the shortest path connecting them."
    Also, you said previously speed, not velocity. Velocity is a vector and speed is it's magnitude (ie a scalar).

    You didn't say combines, you said couples. Coupling is an entirely different thing in physics, for example, the electron couples to the photon. You're misusing the terminology in an effort to look like you know what you're talking about when you're hopelessly out of your depth.

    In fact, what you're calling motion (the idea of a trajectory) doesn't require a spacetime construction (otherwise Newtonian mechanics would not work at all) If it doesn't require spacetime and merely space with an external parameter you're calling "time," then time is simply a parameter that changes along the trajectory - it can be redefined however you like. Calling it time is something semantic rather than a physical truth.
     
  20. Pete It's not rocket surgery Registered Senior Member

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    • A direction in three dimensions is not a simple angle.
    • A vector with magnitude 1 (a unit vector) is a useful representation of a direction.

    You're asserting that "distance" always has to be straight line distance?
     
  21. AlphaNumeric Fully ionized Registered Senior Member

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    No, he said the shortest distance, which may not be a straight line. Distance depends on your 'metric', the measure by which you provide a number when given two points in a region. You can define infinitely many different consistent notions of 'distance' between any two points but the one used in physics is the extension of the standard Euclidean one.
     
  22. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Yes, and thank you for correcting me. Speed is not velocity so I was wrong.
    Thank you again. I'm glad there are people like you around to toss me a tube when I try to fool everyone into thinking I know what I'm talking about

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    . That is how we learn but I wouldn't go so far as say I was trying to look like I know what I was talking about, just trying to participate, keep the discussion moving, and learn as I go, like you.
     
  23. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    This isn't true at the quantum mechanical level.

    What other definition of time do you know of?
     

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