I'm reading GR on http://www.bartleby.com/173/29.html" [Broken] quoting "Hereupon we introduce a hypothesis: that the influence of the gravitational field on measuring-rods, clocks and freely-moving material points continues to take place according to the same laws, even in the case when the prevailing gravitational field is not derivable from the Galileian special case, simply by means of a transformation of co-ordinates." My interpretation of "the influence of the gravitational field on measuring-rods, clocks and freely-moving material points" is : our rulers are not constant at all, because they are influenced by gravitational fields. What he wrote there seems quite different from the usual "masses curve space/time". It appears that it is nothing about space but all about mass changes (non-rigid bodies). http://www.bartleby.com/173/28.html" [Broken] quoting "The form there used (in SR) , “All bodies of reference K, K', etc., are equivalent for the description of natural phenomena (formulation of the general laws of nature), whatever may be their state of motion,” cannot be maintained, because the use of rigid reference-bodies, in the sense of the method followed in the special theory of relativity, is in general not possible in space-time description. The Gauss co-ordinate system has to take the place of the body of reference. The following statement corresponds to the fundamental idea of the general principle of relativity: “All Gaussian co-ordinate systems are essentially equivalent for the formulation of the general laws of nature.”" From those Einstein sentences I read : NON rigid-bodies. The measuring rods and clocks are then 'elastic' in a predetermined way of beeing of course (GR way). According to the way Einstein wrote, as I see it, he is not describing changes in space but changes in 'matter'. COLOR="DarkOrange"](in SR)[/COLOR] is my note because of the context of the sentence.