For Newton the equivalence between gravitational and inertial mass was an empirically decidable question that he answered with the experimental resources at his disposal. The experiment carried out by Eötvös, Pekár and Fekete (EPF) is conventionally interpreted as supporting the principle of equivalence in the sense that gravitational attraction is independent of the composition of the bodies involved in the gravitational interaction. Despite the conventional interpretation of EPF’s results, about 25 years ago in the context of a search for the so-called fifth force, Fischbach and his group (FG) revisited the EPF experiment and claimed that there was evidence for a variation of the Newtonian gravity constant G with the chemical composition of the two interacting bodies. After reviewing empirical results obtained during the last part of the 20th century, in 1999 the FG gave up the search for their fifth force. Regarding this decision by FG, Nieto, Hughes and Goldman wrote in 1989 that “even though the original analysis of Fischbach et al. had been corrected and their proposed coupling to hyper charge is ruled out ..., the correlation with baryon number is present in the Eötvös data” (emphasis in the original). The purpose of the present paper is to briefly report on a Le Sagian gravitational model of our authorship that is fully consistent with EPF’s results, and with many other anomalous observations, some of them mentioned here. Since the sagionic fluid may be identified with dark matter, and the sagion energy identified with dark energy, there is no significant difference with current ideas. What is different is that the Newtonian G is not a constant, and depends on the region of the universe, and on the experimental arrangement and chemical composition of masses used for its determination. Additionally, there is a new background force.
