Re: LET is on shaky ground - continued

From: Trevor Morris (tedd90_at_freeuk.com)
Date: 06/18/04 

Date: 18 Jun 2004 05:06:13 -0700

"Martin Hogbin" <goatNOSPAM1@hogbin.org> wrote in message news:<c8lq18$kdq$1@hercules.btinternet.com>...
> "Trevor Morris" <tedd90@freeuk.com> wrote in message news:a98f5d4d.0405200710.1a818287@posting.google.com...
> > [Sorry for the delay - picking it up via Google]

and again ...

> >
> > "Martin Hogbin" <goatNOSPAM1@hogbin.org> wrote in message news:<c72eq9$ivk$1@hercules.btinternet.com>...
> > > "Trevor Morris" <tedd90@XXXfreeuk.com> wrote in message news:1083170866.4265.0@nnrp-t71-03.news.uk.clara.net...
> > > > "Martin Hogbin" <goatNOSPAM1@hogbin.org> wrote in message
> > > > news:c6nq7g$k0$1@sparta.btinternet.com...
> > > > >
> > >
> > > Only if the frame is Galilean
> > > There is your problem. You are insisting that the word _must _
> > > be how you imagine.
> >
> > No: I am not talking about what is *measured*, but what *is*. Only
> > one inertial frame can be literally "at rest" wrt light-isotropy.
> > Think about it.
>
> This reply shows very clearly what your problem is. When you
> talk about what *is*, you are actually referring to a model in your
> own mind of how the world must be. This is not reality. The only
> reality is the results of experiment.

And if they are in accord with the predictions of a particular model,
the model is not invalidated.
 
[...]
 
> > For example, can
> > you tell us why you prefer a measurement recipe to a definite,
> > unambiguous model of light propagation?
>
> What model?
>
> > > -------
> > > 1) There exists a special reference frame in which no information,
> > > matter, or energy can travel faster than light.
> > > -------
> > >
> > > As far as I know, from a limiting speed postulate, all the physics
> > > of SR/LET can be derived (there may be some details to sort
> > > out).
> >
> > So you at least agree on that. [!!!]
> >
> > >
> > > This postulate is essentially of a conceptual nature
> >
> > Hardly: it is a strong statement about what is possible in physics and
> > what is not possible: there is nothing I can see as "conceptual" about
> > an unbreakable speed limit.
>
> You give no reason for this speed limit or any mechanism in terms
> of pre-existing physics for it.

That is why it is a postulate - a hypothesis relating to a particular
property of space, which is not invalidated by experiments /
measurements.
 
> > ... it is very different from the light
> > postulate, which is about what will be *measured* under specified
> > circumstances.
>
> If it is not about that which can be measured it is even more
> conceptual than the light speed postulate.

It is certainly about measurements. It offers an explanation of why
the measurements turn out the way they do, which imho is better than
merely stating how they will turn out without offering any
explanation.

[...]

> > Look, there are 2 ideas - 1) a unique frame of reference in which
> > light propagation is isotropic, and 2) a speed limit wrt to that
> > frame. 1) does not contain 2), although 2 would be meaningless
> > without 1),
>
> Are you changing your postulates now?

No.
 
> >and a link between them is not entirely surprising. There
> > is certainly no redundancy, but arguably the two postulates should be
> > in the reverse order.
> >
> > > my main
> > > objection to this postulate is the use of 'really'. What can that
> > > possibly mean?
> >
> > It means that something may be going on which is not necessarily
> > revealed by a naive interpretation of "measurements" and appearances.
>
> You have just stated the same thing in different words. In
> what sense is this something 'going on'?

In the sense that they relate to a particular model of field
propagation which explains why certain measurements (e.g. of c) turn
out as they do, which otherwise are unexpected and have no
explanation.
 
> > > So, what have you achieved. You have proposed an alternative
> > > postulate to Einstein's two which results in the same physics.
> > > You are a century too late for this to have any impact. Your
> > > talk of retarded potentials is a mere diversion.
> >
> > No again: retarded potentials illuminates the physics underlying
> > Einstein's postulates, for those who want to see.
>
> This is nonsense. You are back to your old trick of trying
> to get Maxwell's equations to prove themselves valid in any
> inertial frame.

No trick. Maxwell's equations are merely those which apply to the
kinds of fields under discussion. Their relevant property is a
characteristic propagation speed for those fields, as if in a fixed
medium. If that speed turns out to be an upper limit for all speeds
(as a separate hypothesis), then the equations are indeed valid in any
inertial frame and we have LET / SR.
 
> > > > But if the SR postulates are NOT unprovable, but follow from the Lorentzian
> > > > model, isn't that a step forward in our understanding, to be welcomed?
> > >
> > > No, because your model is based on unprovable postulates
> > > as described above.
> >
> > By their nature, successive sets of postulates must eventually end up
> > at something unprovable. But for God's sake if an initial set of
> > postulates clearly has an underlying set from which they can be
> > derived, then the underlying ones are obviously proofs of the initial
> > ones.
>
> You can do it either way. You could take Einstein's postulates
> and obtain yours as a result or vice versa.
>
>
> Martin Hogbin

Yes - I have pointed that out many times! HOWEVER, following Einstein
it has become conventional to deny that his postulates could lead to
those of Lorentz - iow the reciprocity you stated is denied,
incorrectly. Now, accepting that reciprocity as you seem to do, do
you really think it is better to start as Einstein did with empirical
assertions about how the laws of physics should look to inertial
observers and how measurements of c would turn out if done in a
specific way (as if Nature gave a damn), or is it better to have a
specific model of field propagation - w.r.t. a single frame of
reference in which there is an upper speed limit (c) - if that model
then explains why Einstein's two empirical postulates are valid?

Trevor Morris

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