Interpretation of GR: Einstein vs. Contemporary Physicists

[humanino]

There exists some confusion, as evidenced in the literature, regarding the nature of the gravitational field in Einstein's General Theory of Relativity. It is argued here the this confusion is a result of a change in interpretation of the gravitational field. Einstein identified the existence of gravity with the inertial motion of accelerating bodies (i.e. bodies in free-fall) whereas contemporary physicists identify the existence of gravity with space-time curvature (i.e. tidal forces). The interpretation of gravity as a curvature in space-time is an interpretation Einstein did not agree with.

Please take a look at
http://xxx.lanl.gov/abs/physics/0204044
and post your comments/opinions.

 

[humanino]

I have not been able to delete the thread by myself. Pete requested me to do so. I will post the same thread in the special&general relativity forum. Please somebody with the ability delete this thread for me.

 

[geometer]

I admit to not having read your paper, but I find your premise hard to believe. Einstein's Field Equation explicitly relates the curvature of space-time to the mass present. Einstein used the priniciple of equivalency as an argument to show that gravity wasn't really a force.

 

[humanino]

I admit to not having read your paper, but I find your premise hard to believe. Einstein's Field Equation explicitly relates the curvature of space-time to the mass present. Einstein used the priniciple of equivalency as an argument to show that gravity wasn't really a force.

I did not say I agree with the paper ! I am currently shaked in my convictions, so I need other people's advice. I would have many comments on what is weird/missing in the article. I would appreciate if other do it first, because I already began a discussion with Pete in the nuclei/particle forum.

 

[humanino]

The paper by itself is really short. It is written big, and there is a huge space beween lines. It takes really about 5 or 6 true pages, that is about 15 fifteen for me (which is slow, but english is a foreign langage in my referential )

 

[humanino]

Please continue the discussion in the special & general relativity forum as requested by Pete.

 

[pmb_phy]

I admit to not having read your paper, but I find your premise hard to believe. Einstein's Field Equation explicitly relates the curvature of space-time to the mass present.

So? The point is that Einstein identified the presence of a gravitational field with gravitational acceleration (affine connection) and not with tidal acceleration (Riemman tensor). Einstein's equation's related the spacetime curvature at point P with the matter at point P. This means that where there is matter there is spacetime curvature. I'm referring to the field the matter generates. That does not require spacetime curvature. E.g. take a point outside the matter distribution and there can be gravitational acceleration and yet no spacetime curvature.

Relate this to what you know of Newtonian gravity. Laplaces equation is

$$\nabla^2 \Phi = -4\pi G \rho$$

Recall the definition of the Newtonian tidal force 3-tensor (see - http://www.geocities.com/physics_world/mech/tidal_force_tensor.htm)

$$t_{jk} = \frac{\partial^2\Phi}{\partial x^j \partial x^k}$$

with this tensor Laplace's equation can be expressed as

$$t^j_j = -4\pi G \rho$$

This means that where there are tidal forces there is mass and where there is mass there are tidal forces. But consider a spherical body with uniform mass density which has a spherical cavity cut out of it for which the center of the cavity is not colocated with the center of the sphere. Then there will be no matter in the cavity and yet there will be a gravitational field. This field will be uniform, i.e. the tidal force tensor will vanish. See - http://www.geocities.com/physics_world/gr/grav_cavity.htm

Einstein used the priniciple of equivalency as an argument to show that gravity wasn't really a force.

Einstein showed that gravity is an inertial force and as since gravity is a real force then so aren't inertial forces. But that's a whole different topic.

Pete