The principle of general covariance has physical content

Abstract

The issue of whether or not the Principle of General Covariance (GCP) has physical content has been matter of debate and confusion since the inception of General Relativity. In our view the physical meaning of coordinates is related to the question of the possible physical significance of that principle. We believe that the latter may be taken as an appropriate generalized principle of relativity with physical content. With the purpose of throwing light over the subject, after presenting our version of the GCP, we define and construct quasi‐Minkowskian coordinates associated to the word‐line of an observer who transports an orthonormal tetrad (QMCCω). We view the QMCCω as the coordinates that would be obtained by that observer by applying operational protocols valid in flat space‐time to get the Lorentzian coordinates of an event. The set of all the QMCCω is in general an infinite family all of whose members collapse to the usual Lorentzian coordinates when the observer is in free fall, his or her space triad does not rotate (ω = 0) and the curvature of space‐time vanishes. This implements the idea that the set of all the operational protocols which are equivalent —in the sense of assigning the same numerical values— to obtain the Lorentzian coordinates of events in flat space‐time split into inequivalent subsets of operational prescriptions under the presence of a gravitational field or when the observer is not inertial. Something similar must happen with all the physical quantities. Other considerations will be presented.