Re: What is LET?


dej4 wrote:
> Joe Fischer wrote:
> > "shevek" <shevek4@xxxxxxxxx> wrote:
> >
> > [snip]
> > >How does that follow? Why would LET predict a different measured
> > >resistance of the wire?
> >
> > Is it a complication that if a wire is shorter,
> > the resistance has to decrease?
> >
> > Joe Fischer
>
>
>
> Absolutely: they expected the length and the cross-section to change.

As rotchm@xxxxxxxxx pointed out, that expectation is invalid. In
relativity, in interpretations of SR and LET, any length, as measured
in its own rest frame, remains constant irrespective of its motion with
regards to any other frames.

A meter stick is one meter long (as measured in its own rest frame),
regardless of its motion w.r.t the local quantum foam or space-time
constituents.

If the length of the wire is the same in the laboratory frame
regardless of its orientation, why should the measured resistance
change?


> Because of the changes do not cancel each other (they enhance each
> other) , the bridge was expected to become imbalanced. The galvanometer
> used was
> sensitive enough to detect the predicted change. TR detected a much
> smaller change than the one predicted based on the LF contraction.
>
> And yes, you are perfectly correct Joe, LET has no place since SR had
> been supplanted by GR. Lorentz conceded very ellegantly:
>
> "As to the ether (to return to it once more), though the conception of
> it has certain advantages, it must be admitted that if Einstein had
> maintained it he certainly would not have given us his theory, and so
> we are very grateful to him for not having gone along the old-fashioned
> roads." Hendrik Antoon Lorentz, "Problems of Modern Physics; a course
> of lectures delivered in the California Institute of Technology,"
> Edited by H. Bateman, _Ginn_, 1927.

Indeed a very elegant statement - though hardly a "concession" with
regards to the existence of a local rest frame of electromagnetic field
constituents.


And now for the literature search results. Following the paper trail
from Chase's 1927 paper "The Trouton-Noble Ether Drift Experiment", he
references his own paper from 1926 "A repetition of the Trouton-Noble
Ether Drift Experiment", which then references:

"Fitzgerald & Loretz, Scientific papers, p. 556"

Any idea where that could be found? His experimental setup seems
somewhat different from the Trouton and Rankine experiment, as he
measures a torque and not a resistance..

I was also able to download the 1908 paper from the JSTOR.ORG archive
http://tinyurl.com/dn2j2
(Proc. Roy. Soc. 80A, 420-435, 1908)

>>From that paper, page 421:

"Now suppose that the wire AR is turned tlirough a right angle, so that
its
length is perpendicular to the velocity v. According to the Fitzgerald-
Lorentz shrinkage hypothesis, the length of the wire will be thus
increased
by a srnall amount [\delta l], such that [\delta l /l = 1/2 (v/V)^2] ,
where V is the velocity of light, and all powers of v/V higher than the
second have been neglected, v being
supposed very small compared with V."

Trouton and Rankine fail to say here that this Lorentz-Fitzgerald
change of length occurs in the ether frame and not in the laboratory
frame! Why should the resistance of a wire as measured in the
laboratory depend on the length of the wire as measured in some other
frame of reference?

Also interesting to note is that Trouton & Rankine's conclusion is
nowhere near the same as the statements attributed them on the
wikipedia website, rather (p.434):

"... the specific resistance of a material is dependent upon the
direction of flow of the current, being greater to a current flowing
parallel to the velocity of the material through space than to a
current in a perpendicular direction. The magnitude of this change of
specific resistance is shown by the experiments to be certainly within
2 per cent. of being sufficient to compensate the change of length.

Note.- In view of the very general acceptance of the
Fitzgerald-Lorentz shrinkage theory, the negative results of these
experiments will probably be attributed to a dependence of specific
resistance on direction of current flow. In this connection it is
worthy of note that certain independent considerations point to the
same conclusion..."


Conclusion: The wikipedia Trouton-Rankine page misrepresents the
authors of that paper, as well as failing to point out the shortcomings
of the analysis in the paper.

Cheers- shevek

.

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