Published online by Cambridge University Press: 04 August 2017
In this paper, we discuss theoretical and observational aspects of an SEP violation. We present a two-times theory as a possible framework to handle an SEP violation and summarize the tests performed to check the compatibility of such violation with a host of data ranging from nucleosynthesis to geophysics. We also discuss the dynamical equations needed to analyze radar ranging data to reveal an SEP violation and in particular the method employed by Shapiro and Reasenberg.