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Misunderstanding about the Foucault Pendulum

  1. Jul 6, 2011 #1
    Dear members,

    I have a misunderstanding about the Foucault pendulum. In early 1851, Foucault had an insight that led to his famous discovery. This bit of serendipity occurred during construction of a pendulum clock to regulate the drive of a telescope. Foucault had secured a rod in the chuck of a lathe. Perhaps accidentally, the rod was disturbed so that it vibrated. Foucault noticed that the plane of oscillation of the vibrating rod remained fixed in orientation even as he slowly turned the chuck. This observation inspired him with the notion that the vibrating motion of a freely suspended pendulum might somehow be related to the earth’s rotation.

    Foucault noticed that the plane of oscillation of the vibrating rod remained fixed even if the chuck rotated. In the Pantheon's experiment, the earth is the rotating chuck and the rod is the pendulum. So, why the plane of oscillation of the pendulum revolves and why the plane of oscillation of the vibrating rod do not ? I don't understand the logical link between : "the plane of oscillation" and "necessarily it is due to earth's spining".

    Another question :
    According to some articles, the Pantheon experiment occurred on March 31st, 1851 but in other articles we can find March 26th, 1851. Somebody knows ?

    Best regards,
    Jeff
     
  2. jcsd
  3. Jul 6, 2011 #2
    The logic behind that effect is best imaginable if you think about a pendulum stationed on the north or south pole (with regards to earth's rotation). As the earth rotates so does the chuck. But plane of oscillation remains fixed. This is how an inertial frame observer would see it. But from our point of view it seems like chuck is fixed and plane of oscillation rotates (we are observing the pendulum from chuck's frame of reference). I hope this helped.
     
  4. Jul 16, 2011 #3
    Thanks !
    Your explanation helped me !

    Another question :
    According to some articles, the Pantheon experiment occurred on March 31st, 1851 but in other articles we can find March 26th, 1851. Somebody knows ?


    Best regards,
    Jeff
     
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