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From: glird on 20 May 2010 13:09
On Apr 22, 11:43 am, Tom Roberts <tjrob...(a)sbcglobal.net> wrote:
>
>< The apparatus was constructed so the arms have the same length in the rest frame of the apparatus. That is implicit in the phrase "identical legs", which inherently means comparing them when they are at rest in the same frame. >

To do that one uses a measuring rod. The measuring rod's length will
change exactly as the length it is measuring. Therefore the lengths of
identical rods measured that way will remain constant, even though
they are not.

>< The words "in this frame ... the leg ... is shorter than the other leg" are mildly ambiguous -- rather than saying "is shorter" you should say "is measured to be shorter". >

T R(ex) is the one who is being ambiguous here.

>< The word "is" implies this is an aspect of the legs themselves, which is not correct; the phrase "is measured to be" captures the relationship here.. After all, it is the MEASUREMENT of their lengths that occurs in this frame, not the legs themselves. >

In the M&M experiments, the pre-measured lengths of the arms were
identical. Regardless of any change in the velocity of the apparatus,
the null result occurs whether or not anyone measures the length of
each leg then or later.

>< "Length contraction" is INSUFFICIENT -- you need to apply the full Lorentz transform between frames. "

Length contraction IS fully sufficient. The Lorentz transforms didn't
even exist until 30 years AFTER the null results happened.

>< For instance, when considering a short light pulse, the reflections at the ends of the arms are not simultaneous (except in the rest frame of the apparatus). >

So what? The arms canchange length by any amiunt at all, s long as
those in the direction of the systems motion end up q shorter than
those in the perpendicular directions. If - as Lorentz wrote in his
1904 paper - the legs shrink in X,Y,Z by Q,q,q (Q = q^2 = c^2-v^2), no
rate changes and no LTE are needed to explain the null results and the
Lorentz transforms are inapplicable, So are T R's mythical "rotations"
of the X' axis of a viewed system.

glird
>
>         OK, in other frames there are two discrete orientations of the
>         apparatus for which those reflections are simultaneous.
>
> Tom Roberts

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