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1 s

  1. Oct 27, 2006 #1
    c = 299,792,458 m/s

    1 s = 9,192,631,770 vibrations of the radiation (of a specified wavelength) emitted by a cesium atom (Resnick in Physics, 4th ed., p. 4).

    All our judgments in which time plays a part are always judgments of simultaneous events (Einstein in The Principle of Relativity, p. 4). If, for instance, I say that a ray of light departs from point A (in the direction of point B) at the beginning of the vibrations of the radiation emitted by the cesium atom, I mean something like this: “The departure of the ray of light from point A and the beginning of the vibrations of the radiation emitted by the cesium atom are simultaneous events.” I can say that the ray of light departed from point A when the vibrations of the said radiation began, or I can say that the vibrations of the said radiation began when the ray of light departed from point A. let’s say that the ray of light reached point B at the end of the vibrations of said radiation, such that the number of vibrations is 9,192,631,770, and the distance between A and B is 299,792,458 m. I can say that the time required by the ray of light to travel from A to B is 9,192,631,770 vibrations of the radiation emitted by the cesium atom, or I can say that the time required by 9,192,631,770 vibrations of said radiation is the distance the ray of light travels from A to B.
     
    Last edited: Oct 27, 2006
  2. jcsd
  3. Oct 27, 2006 #2
    In one second or after 9,192,631,770 vibrations light travels excactly 299,792,458 meters not 1 meter.
     
  4. Oct 27, 2006 #3
    yes, you are right. i edited the post. thanks!
     
  5. Oct 27, 2006 #4

    Doc Al

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    And your point is ...?
     
  6. Oct 27, 2006 #5
    on pages 38-39 in The Principle of Relativity, A. Einstein writes the following:

    If we wish to describe the motion of a material point, we give the values of its coordinates as a function of the time. Now we must bear carefully in mind that a mathematical description of this kind has no physical meaning unless we are quite clear as to what we understand by "time." We have to take into account that all our judgments in which time plays a part are judgments of simultaneous events. keeping this in mind, i believe that one comes to a better understanding of what is 1 s.
     
  7. Oct 27, 2006 #6

    ZapperZ

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    To repeat what Doc Al asked you: "And your point is....?"

    Everyone who studies Special Relativity is hit right on the face with such realization that the ideas that we have taken for granted (space, time) must clearly be defined.

    So were you trying to teach us Special Relativity here?

    Zz.
     
  8. Oct 29, 2006 #7
    no. just sharing what i have realized (a more flexible way of understanding time and the definition of 1 s.)

    MeJennifer states in her reply that "In one second or after 9,192,631,770 vibrations light travels excactly 299,792,458 meters."

    my point is that "In one second or after light travels exactly 299,792,458 meters the number of vibrations is 9,192,631,770" since all our judgments in which time plays a part are always judgments of simultaneous events.

    we can arbitrarily substitute 9,192,631,770 vibrations for the time required by light to travel from A to B, or substitute the motion of light from A to B for the time occupied by 9,192,631,770 vibrations. in either case, the time is defined as 1 s.

    1 m is (1/299,792,458)*AB.
     
  9. Oct 29, 2006 #8

    ZapperZ

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    Then please reply to that particular thread. If not, this looks like a pointless thread with no point. If everyone does this, we will be clutted with useless pieces of disconnected information. Physics is NOT that!

    Zz.
     
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