New Interpretation of Equivalence Principle in General Relativity from   the viewpoint of Micro-Macro duality
  We propose a new interpretation of the equivalence principle underlying Einstein's general relativity: a free-falling frame with gravitational force eliminated locally in a small spacetime region shows the existence of a boundary level, below which gravity is absent and above which \textit{gravity emerges as condensation effect of microscopic motions} within each such frame and interrelates free-falling frames at different spacetime points. In this picture, gravitational field as a mediator of different free-falling frames shows a remarkable \textit{parallelism with an order parameter to specify "degenerate vacua"} in different thermodynamic pure phases due to the \textit{condensation effects} in phase transitions. As the physical basis of general relativity is found in the universality of mass point motions due to the constancy of [inertial $m$]/[gravitational $m$], the general relativistic notion of "spacetime" should be meaningful only in the validity regime of this constancy, which is \textit{of empirical nature}, contrary to the usual consensus. At the end, we comment on the impossibility to observe gravitational waves which would make gravitons and quantum gravity questionable. 
Izumi Ojima
physics.gen-ph