Comments on the Misunderstandings of Relativity and Theoretical Interpretation of the Kreuzer Experiment
In 1966, the Kreuzer experiment set an upper limit on the difference in the ratio of active to passive mass between fluorine and bromine, and an interesting interpretation was given by Thorne et al. However, in 1976 Will, with his new parameterized post-Newtonian (PPN) approach, interpreted this experiment as providing an upper limit on his parameter combination related to electromagnetism. We show that, from the viewpoint of general relativity, Will's approach remains to be justified. Moreover, his result originates from his unphysical nuclear model, which ignores the isospin-dependent nuclear forces and is actually inconsistent with general relativity. It seems that to determine the constraint on the gravitational coupling to electromagnetism is beyond the valid application of the PPN formalism. As a further step, experimental measurement for the coupling constant to electromagnetism is recommended.