Re: the basis of relativity

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.

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.


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.

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".

PS: Once again I think Mr. Baugh posts well. 

Thank you.

--
Regards,
James Baugh
.

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