sci.physics.relativity

On Sep 12, 11:36 pm, stevendaryl3...@ (Daryl McCullough)
wrote:
> Alen says...
>
> >It would be nice if you people could make your position clear
> >one way or another. Do spacetime rotations of inertial
> >frames really exist, from your perspective, or not?
>
> Your question doesn't have any meaning. There are two
> different things involved in a (rigorous) scientific
> theory, a mathematical model, plus a mapping from that
> model to physical observables. Minkowsky spacetime is
> a mathematical model. It "exists" in exactly the same
> sense that the natural numbers exist, or the real
> numbers exist. Minkowsky spacetime is *used* in the
> theory of relativity to make predictions about the
> results of experiments.
>
> Asking whether a mathematical abstraction exists
> makes no sense. Asking whether a testable prediction
> is born out by experiment is the only test of a theory.

This is a modern departure from the original concept
of science as an attempt to understand how reality
works. It seems to me to be virtually a nice way for
physicists to admit that they don't know what the reality
behind SR is. Such a difficulty didn't exist in the
Newtonian era.

>
> >Or do you admit to having no explanation at all for the
> >existence of length contraction?
>
> Whether something counts as an "explanation" or not is
> a *psychological* question. One can explain how an effect
> follows from other basic assumptions, but if someone
> asks what those assumptions follow from, eventually
> your explanations must end somewhere. In Newtonian physics,
> the end of explanations is captured by Newton's laws of
> motion, together with the implicit assumption that spacetime
> is Galilean. In Special Relativity, the explanations end
> with a different set of assumptions, that spacetime is
> Minkowskian rather than Galilean. There is no more an
> explanation for why spacetime should be Minkowskian than
> there is for why spacetime should be Galilean.
>
> Ultimately, physics is concerned with what *is* the
> case, not why it is the case.

[...]

> Daryl McCullough
> Ithaca, NY

In terms of the original aim of understanding nature,
there is clearly a vast difference between the Galilean
era, and that of SR. At the velocities we are familiar with,
we encounter spacetime as Galilean. We can virtually
'see' Galilean transformations with our eyes. Nothing
about it is obscure, and it all makes perfect sense
When it comes to the Minkowski era, however, the
whole picture is radically different. Nothing is really
explained, or makes sense, by comparison with the
Galilean. Minkowski spacetime therefore deserves a
far more critical examination than the Galilean or,
failing that, an admission that, in the Minkowskian
environment, we really don't know what we are talking
about, and must therefore retreat to a position of clinging
to a mathematical model, far more divorced from a
'real' explanation than ever before, and throw the whole
reality itself into a 'too hard' basket.

If that has to be the current status of physics, it
might, perhaps, help to explain why physics courses
are apparently experiencing an ever declining number
of new applicants. People want to understand, not
just calculate. That, at least, is my view.

Alen