PS of course the local classical laws of physics (tensor and spinor equations) are still independent of the local coincident frames either unaccelerated LIFs or absolutely accelerated LNIFs. Note however, that the LNIF detectors see the Unruh-Hawking black body thermal photons not seen by the LIF detectors. This is a non-classical quantum effect.
On Oct 18, 2007, at 3:23 PM, Jack Sarfatti wrote:
In both Galilean relativity and 1905 Einstein special relativity non-accelerated "geodesic" motion is globally relative. The same is not true in 1916 Einstein general relativity. Non-accelerated geodesic motion means no g-force, weightless free-float. Note that a uniform motion at constant speed in a fixed direction in curved spacetime is not a local non-accelerated geodesic. For example, drive your car on a straight road at constant speed (Earth's surface curvature ignorable for small distances). You are not weightless. When you fall off a ladder you are on a locally non-accelerated geodesic motion momentarily. Your local unaccelerated motion looks "accelerated" to Bob fixed to Earth's surface, which is, in fact, an accelerated off-curved geodesic LNIF. Therefore, there is an absolute test for local geodesic unaccelerated center-of-mass (COM) motion, i.e. free-float weightlessness. In this sense acceleration is locally absolute. If you feel g-force your motion is locally accelerated relative to the intrinsic geodesic structure of the local geometrodynamic field. The key geodesics are the null geodesics ds^2 = 0 of light rays. The intrinsic local frame-invariant 1916 (zero torsion) geometrodynamic field curvature is in the relative tilt of neighboring invariant light cones as shown by Roger Penrose. Note that curvature is "geodesic deviation," i.e. nonlocal relative acceleration between two slightly separated geodesic weightless observers, neither feel local COM g-force. That is, two free-float weightless observers with zero local objective accelerations in their point centers of mass, nevertheless, detect a nonlocal relative acceleration as shown, for example, by the drift of Doppler radar signals - that is the essential operational definition of curvature.