Re: the basis of relativity

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.

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.




Neil G wrote: 
Baugh wrote:

Neil G wrote:

relativity is based on the equivalent principle,
then the developed relativity shows that the equivalent
principle is wrong


You misunderstand.  The equivalence principle states that
given a dynamic gravitational field ("real force") in
a given geometry you can alter the geometry and alter the
dynamic force to yield an equivalent predictive theory.



are the "real forces" considered "dynamic gravitational fields"?

I thought that there was a huge difference between gravitational and a
Newtonian force


Given this then you can *by convention* choose a geometry
in which the dynamic force goes away and in that choice of
geometry the gravitational force is just geodesic evolution.



"geodesic evolution" means no Newtonian forces?


It is similar to saying you can set "zero electrostatic potential"
to be at any point you like.  When doing problems you set the ground
of your device to be at zero volts.  That is another "relativity
principle" namely that voltage is relative and thus it is only
meaningful to speak of voltage differences.



thanks, but I still can't see the connection between the two forces


Setting the ground to be zero volts does not mean the original
relativity is wrong, it rather relies implicitly on the relativity
principle being right.  Otherwise you'd have to worry about whether
the ground is "really at zero volts".



you sounds convincing, but I still can't understand


These choices of convention are loosly refered to as "gauge 

conditions".

There is a deep connection between "equivalence principles" and gauge 


theories.  One is effectively considering a whole class of equivalent
models with an explicit group of equivalence transformations (the


gauge

group). One then insists that physical phenomena which one may 

predict

be independent of the choice of model (choice of gauge).



I think I begin to understand, thanks


This is how Einstein formulated his field equations.

Note however that in the case of gravitation the purely geometric
formulation leads some to take geometry too seriously as a physical
quality instead of a feature of the formal language.  Hence attempts
to quantize gravitation by "quantizing geometry".  This I believe
to be the major flaw of quantum string and 'brane' models


inaccurately

refered to as "theories".

--
Regards,
James Baugh



I understand now, so the "forces" are actually the same type of forces
depending on one's point of view, thanks



--
Regards,
James Baugh
.

Relevant Pages

  • Re: Questions (Space)
    ... corrections have to be taken into account. ... It is only general relativity that posits ... As I said in the previous post, it's the simplest possible geometry. ... So what's your problem with gravity as the exchange of virtual ...
    (rec.arts.sf.composition)
  • Re: Questions (Space)
    ... It is only general relativity that posits ... As I said in the previous post, it's the simplest possible geometry. ... So what's your problem with gravity as the exchange of virtual ... Special relativity is often called a classical theory, ...
    (rec.arts.sf.composition)
  • Re: Here it is again.. Twin paradox debunking 101
    ... "distancetimemath" is the geometry of Relativity. ... distancetimemath is geometry but that is the problem ... what causes the string to hang down? ... Was the cause gravity that caused it to hang? ...
    (sci.physics)
  • Re: GR ?
    ... << Einstein discovered that there is a relationship between mass, gravity ... Mass distorts spacetime, causing it to curve. ... Special relativity destroyed classical physics view of absolute ... is described by Euclidean or plane geometry. ...
    (sci.physics.relativity)
  • Sarfatti Star Gate Chronicles March 21, 2009
    ... Einstein’s special and general theories of relativity are all about ... you are weightless in an inertial frame in Einstein’s theory. ... inward attractive gravity force of magnitude acting on a freely- ... “Think of assembling meter sticks and clocks into a cubical lattice ...
    (sci.physics.relativity)
Loading