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Time Dilation From Velocity

  1. Jul 28, 2009 #1
    Simple question, but I don't expect a simple answer.

    What are the causes of Time Dilation relative Velocity? I can swallow the fact that gravitational fields can change the speed of time locally. But velocity?

    What the process behind Time Dilation related to velocity?


    I can never seem to get this question answered no matter what site I search. I'm sorry this is my one and only post but this is a burning question of mine.

    Is it just some math or are there practical reasons for Time Dilation from Velocity?

    - Thanks in Advance.
     
  2. jcsd
  3. Jul 29, 2009 #2

    A.T.

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    Relativity doesn't describe any process or cause for it. It just follows from observed empirical facts when they are assumed to hold in general. The closest you get to a cause is a geometrical interpretation, where the advance in space-time is constant, and the speeds trough space & time are just projections of it:
    http://www.adamtoons.de/physics/relativity.swf
     
  4. Jul 29, 2009 #3
    Could you elaborate please? What is this length contraction? Is this based on the observers view of the object?
     
  5. Jul 29, 2009 #4

    A.T.

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    Yes length contraction tells you how much shorter the moving object is for the observer. In this geometrical interpretation the length measured by the observer it is the proper length (measured in the objects frame) projected onto the space dimension.

    Time dilation is similar: The objects advances always at c in space-time, but only the projection of that advance onto the proper-time dimension determines how fast the object ages in the observer's frame.
     
  6. Jul 29, 2009 #5
    Could this then be a cause of sorts? It seems like a sort of mathematical property of space-time interacting with matter, but am I right to say this is the cause? Or is it the effect?
     
  7. Jul 29, 2009 #6

    A.T.

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    Would it make a difference for experiments how you call it? If not, it's not physics, just linguistics.
     
  8. Jul 29, 2009 #7
    That's what I'm asking. So right now scientists just sort of accept Time Dilation from velocity, just based on math and some experiments? Shouldn't there be some searching as to the mechanisms behind it?
     
  9. Jul 29, 2009 #8

    A.T.

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    That is sort of what scientists usually do.
    What do you mean by "mechanism"?
     
  10. Jul 29, 2009 #9
    The cause...

    If someone asks what causes gravity. We can now say, it's a massive object like a planet that warps the space-time, but what about Time Dilation from Velocity? Is it just some fundemental process we need to just learn to accept "just happens"?
     
  11. Jul 29, 2009 #10

    A.T.

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    Warped space-time is a geometrical model, just like the one I gave you for time dilation.
     
  12. Jul 29, 2009 #11
    One thing is Time Dilatation you referred is a result of math from special relativity equations. Using those equation we can explain one simple but important observation that the speed of light is the same regardless of the observer frame speed. Then you may ask can we derive the special relativity equation from more fundamental principle ?
     
  13. Jul 30, 2009 #12
    Can we?
     
  14. Jul 31, 2009 #13

    A.T.

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    Depends what you accept as a "principle" or when you stop asking "but why is that so?". If you accept geodesics in curved space-time as the "cause" of gravity, why cannot you accept a constant advance rate in space-time as the "cause" for time dilation from relative movement? I don't see any qualitative difference here. In fact both principles are part of the same geometric model.
     
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