Re: the basis of relativity
- From: "Ken S. Tucker" <dynamics@xxxxxxxxxxxx>
- Date: 29 May 2005 11:52:02 -0700
Studied J. Baugh's post, and stretched a few neurons:-).
Baugh wrote:
> Ken S. Tucker wrote:
> >
> > Baugh wrote:
> >
> >>Let me clearify further. My analogy with regard to electrostatic
> >>potential was aimed at the point of the relativity being broken by
> >>fixing an aspect of the theory by convention. This was in response
> >>to your claim that the theory contradicted itself in its practice.
> >>
> >>With regard to the theory of gravity as I described it. The
> >>point is that the equivalence principle states that you
> >>can either treat gravity as a "real" force or as a pseudo-force
> >>or as a hybrad of the two. You can't distinguish between
> >>a "real" gravitational force and a pseudo-force due to curvature.
> >>(curving time coordinates is equivalent to accelerating the frame.)
> >>
> >>It is not completely correct to say gravity is "just geometry" rather
> >>one should say gravity is indistinguishable from geometry.
> >>It is a subtile but possibly important distinction.
> >>
> >>Take some solution to Einstein's equations, then perturb the geometry
> >>but at the same time "add by hand" an additional field of forces in
> >>such a way that the combination predicts particles
> >>will follow the original paths. You have the same theory with
> >>slightly changed metaphysical interpertation. Since it is redundant
> >>it is just as well to only work with purely geometric form.
> >>But it is by no means an affirmation of metaphysical facts.
> >
> >
> > Just a quick input James, been following your posts
> > and I think you're quite smart!
> >
> >
> >>You can look at the perturbative analysis of gravity waves as an example
> >>of a hybrid description of both geometric and dynamic components to the
> >>gravitational field. You can also look at it as simply "all geometry"
> >>but treated perturbatively which is the usual "interpretation".
> >>The point is that neither "interpretation" is a true interpretation.
> >>The true interpretation is that test particles will go "that-a-way"
> >>in the presence of matter distributions as predicted by the theory.
> >
> >
> > S Weinberg's writes similiar to James about geometrization of
> > gravitation, and I rarely disagree with SW. however, we have
> > extreme experimental evidence that only 3 spatial dimensions
> > (by testing freedom of movement) exist. Also, that movement
> > requires a real time.
> >
>
> You've neglected some other degrees of freedom, namely rotation
> and Lorentz boosts, phase translation, boson-number etc...
> My point being that the dimensionality you so carefully verify
> from experiment is that of the group acting on the object.
> Only in the singularity of the non-semi-simple Poincare group
> do we see a distinction between translational and rotational-boost
> transformations. This singularity is lost say in a deSitter model
> and one man's translation is another man's boost.
>
> I see the space-time dimensions as simply the dimensions of a normal
> subgroup of the group of observable transformations when you choose a
> highly singular perspective. One may always add to this group and
> subtract from it. The essential question is how we classify physical
> systems and how the groups we choose transform between them.
>
> > I respect James and SW's open mindness but I regard that as a
> > dangerous philosophy. It is dismissive of operations in curved
> > 4D, as being real.
>
> I don't dismiss the operations I dismiss the *fundamental* necessity of
> a specific geometric model in which the operations must be embedded.
> Rather the operations are the primary elements of actuality. How we
> describe their relationships to each other gives us a topological
> dimension. But this is a dimension of parameters of description.
Ok, I think we're using different definitions of the word
*dimension*, ugh, a possible sematic misunderstanding.
Coming from a tensor background, I generally understand
the summation of the indexs as the dimesionality, eg.
ds^2 = g_uv dx^u dx^v where u,v sum over {0,1,2,3},
and the 0,1,2,3 are the dimensions, (I do respect Kaluza's
5D too). That's a fairly clear definition of dimension.
But I think you (James) have a different definition,
if so could you define it? I find the context alone
a little to difficult to see the re-definition.
> On a pragmatic level a four dimensional space-time model is highly
> useful and descriptive. It however invokes aprior assumptions which
> may cease to be valid when for example we consider the interior of
> the nucleii of atoms where quarks and gluons are said to swim.
>
> > We've worked hard to define spacetime and
> > we've measured carefully the effects of gravity on light, like
> > deflection, Shapiro, Pound-Rebka, etc...where light defines our
> > viewpoint.
>
> Yes but these careful measurements needn't rely on a specific
> choice of space-time geometry (or connection). The question is
> begged as to whether the hard work in defining a space-time itself
> is fruitful.
The unification of Spacetime by the Lorentz transform
and better defined by Minkowski, was the basis of the
unification of the Mass-Energy Conservation Law.
GR went further and Energy-Mass and Spacetime using
G_uv=T_uv were unified, though not as thoroughly as
many would like to see.
From that, theoreticians and experimentalists are
able to compare results, so it has been fruitful.
> > For those reasons, there is no way I'll reconsider the idea of
> > spacetime being an imaginary frame for solving physics problems,
> > spacetime is real.
>
> As a personal opinion that's fine. As a scientific debate it
> is moot. One does not observe space-time points, one observes
> events occuring to objects to which we assign space-time coordinates.
>
> > Personally, I don't buy the idea of a slow
> > divorce from reality to suck up some math, on the contrary I
> > would have the logic of math confirmed by Nature, and not the
> > other way around to fit our fantasies...keep that going and
> > we're back to the idiot Catholics who decided creation happened
> > in 4004 BC, and a lot more dummy poop the pope sells to flockies.
> >
> > I meant that paragraph to be severe, because science must retain
> > a firm foot in measureable reality. Everyone reading this post
> > has access to a clock and ruler, and thus we all share spacetime,
> > that non-negotiable.
> > Regards
> > Ken S. Tucker
>
> I don't totally disagree with your intent and severity. I think
> it is slightly off aim. I've picked up the language of my thesis
> advisor and mentor of distinguishing between *actuality* which
> consists of the events of measurement and interaction i.e. what some
> call "phenomenological reality" and the meta-physical objective
> *reality* we may imagine underneath. Empiricism cannot see beyond
> the *actuality*, we must build a *reality* from our imagination.
> That's well and good provided we recognize the source.
Interesting paragraph. I sometimes study "Occurance" in place
of "events", by defining a change in an "Occurance" as,
DO = Dx Dy Dz Ds DE ,
where Ds is a proper time increment and DE is D(Energy)
corresponding to and Energy increment like a photon.
> The crucial point I think you want to make is not to mistake mathematics
> for physics. But I would point out that this is more often done by
> presupposing that the mathematics represents a metaphysical construct
> e.g. a manifold or a "super-string" which is out. One gets into
> silly arguments about trans-finite cardinalities when the actuality
> we experience in any given experiment is finite in nature.
>
> What is measured and observed are the behaviors
> and phenomena which we associate with that object in a reality model.
> It is important to put the phenomena first so that we don't
> inadvertently cross the line of scale or scope where the objective
> reality assumptions cease to be valid. This is precisely what is
> happening in the so called paradox of Schrodinger's Cat.
>
> One mistakes superpositions of mathematical description for
> superpositions of "realities".
Yes to the above.
Thanks for your time.
((my brain hurts :-))
Ken S. Tucker
.
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