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Alignment of axis

  1. Apr 18, 2010 #1
    In Einstein's 1905 paper he says that, by reasons of symmetry, we can assume the coordinate axis of the stationary and moving frame are aligned.

    If the y and z axis rotate towards/away from the x axis in the moving frame in a way dependent upon the velocity, how does this break the symmetry of the problem?

  2. jcsd
  3. Apr 19, 2010 #2


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    Einstein's stationary and moving frame are both inertial … the axes cannot rotate.
  4. Apr 19, 2010 #3


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    If instead you are saying that I have 2 frames which are not aligned (e.g. the x-axis doesn't point where the x'-axis points), what happens? The math gets a lot more complicated, but the physical results stay the same. There's no reason to construct 2 coordinate systems which don't align in SR.
  5. Apr 19, 2010 #4
    You get a set of transforms that look very similar to Lorentz , see for example :

    H. Nikolic,
    "Proper co-ordinates of non-inertial observers and rotation",
    gr-qc/0307011, invited contribution to the book "Relativity in Rotating Frames", editors G. Rizzi and M. L. Ruggiero, Kluwer Academic Publishers, Dordrecht (2004)
  6. Apr 23, 2010 #5
    I wasn't implying that they rotate continuously with time.

    If a set of axis are at right angles in their proper frame, why should they remain at right angles when viewed from a moving frame?

    Einstein suggests they must remain so for symmetry reasons and i think i can see why now, partly.

    The y and z axis can be flipped with the negative to give another stationary frame with the moving frame travelling along the same x axis in the same direction. This means the transformation at (x,-y,z) = (x,y,z) and likewise (x, 0+dy, z)= (x, 0-dy, z), for example. So there is no variation of the moving axis y' wrt x and likewise with z'.
  7. Apr 23, 2010 #6
    Then, what you want is this. This is the most general form of the Lorentz transform.
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