== The transition from SR thinking to GR thinking == 

 Unfortunately I have too few clues to reconstruct which version of WEP you have in mind, among the dozens of versions. You'd have to describe what you have in mind from scratch.  |   

 : It is there on the Equivalence principle page itself:  The rule for determining that one is in an accelerated frame of reference.  It does need elaboration, along the lines that you outline at the end of this message.     

 In the transition from newtonian thinking to GR thinking many things remain the same, but the concept of 'acceleration' is profoundly different in the two paradigms.  

 Recapitulating: in newtonian thinking, the concept of acceleration is anchored on the concept of the common center of mass. It is assumed that the common center of mass of an assembly of objects will always continue in inertial motion. Newtonian thinking is to assert that to maintain constant distance and direction with respect to the common center of mass is what fundamentally constitutes inertial motion. (Also uniform change of distance is defined as inertial motion.) 

 In GR context: the referencing to the 'common center of mass' must be relinquished. What remains is to define acceleration as 'acceleration with respect to the local inertial frame of reference'. The 'local inertial frame of reference' is defined as: 'the local frame that is stationary with respect to a free-falling test mass'. 

 GR asserts the following two statemens: 
 (1) Standing on the surface of a planet, you are being accelerated with respect to the local inertial frame of reference. 
 (2) Standing on the surface of a planet, your distance to the center of gravitation of that planet remains the same. 

 :The rule for determining that one is in an accelerated frame of reference.      
 You give no clues as to what concept of acceleration you have in mind. Clifford Will associates the WEP exclusively with Newtonian thinking.  

 Concepts like rest mass, center of mass, distance, time, relative velocity, energy, remain by and large unchanged in the transition from special relativity thinking to General Relativity thinking. But the concept of acceleration gets a huge make-over (along with gravitation).   |