Re: What should a theory give us?


"Jeckyl" <noone@xxxxxxxxxxx> wrote in message
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"harry" <harald.vanlintelButNotThis@xxxxxxx> wrote in message
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"Jeckyl" <noone@xxxxxxxxxxx> wrote in message
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I understand it .. and in LET as put forward by O'Barr it is crushing ..
things getting physically shorter .. not just the measured 'shrinking'
of SR

Sorry but no: that's an erroneous answer. One last time: A car in a car
accident doesn't "shrink" but is crushed. And a metal rod that cools down
doesn't "crush" but shrinks.

I don't quite see the difference .. I was using shrinking to refer to the
reduction in the measured size (but not physical size), as opposed to
crushing where there is a physical change in the size.

As long as all motion is inertial (thus no change of shape), one can only
say what is being measured. And funny enough, Einstein called that
difference in state "apparent" but also "physical", while you call that "not
physical" and I call it "apparent".

That is the distinction I'm trying to make here .. and it is a very real
distinction (as O'Barr goes to great lengths (if you pardon the pun) to
point out). You seem to be making the distinction that where there is an
external force it is crushing, whereas shrinking is from 'internal'
forces.

Yes, that's basically the difference, physically (*both* words definitely
describe physical processes).

In that case, we still need a word for the change in measured size when an
object is measured from a relatively moving frame of reference (when
proper length is maintained). We can't really call both 'shrinking' as
they are very different concepts. Can you suggest a pair of words that we
can use that makes that distinction without giving you the problems that
'crushing' does :)

Apparent shrinking; in other frames the same change may appear as expansion.
Note that according to measurements in all inertial frames *something*
happens. In other words, in the valid frames for the description of physics
there is only disagreement about the description of *what* happens; there is
no disagreement about the observation that something physical happens.

However, I probably did not tell you that length contraction follows
from the Maxwell equations, although Maxwell had not realised that
himself. It was first proposed by Fitzgerald based on a paper by
Heaviside. Heaviside showed in 1888 for static fields that they shrink
by a factor gamma in the direction of motion, which made it plausible
that it should be the same for intermolecular fields.

So does that mean the 'ether' contracts, or just the waves in the ether?

Only waves and fields can change chape.

So waes and fields change shape as per lorentz transforms, and that makes
matter physically contract by the same amount and clocks run slower and
get out of sync

That's right - with the stationary ether model, relatively to the ether.

I share the opinion of Lorentz and Einstein for whom SRT is a
principle theory: on purpose there's no explanatory metaphysics
inside. Of course, everyone still plugs his/her own philosophy in, in
order to make sense of it. :-)

True :)

Have a nice day.

You too

Regards,
Harald


.

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