The explanation of inertia based on “Mach’s principle” is briefly revisited and an experiment whereby the gravitational origin of inertia can be tested is described. The test consists of detecting a small stationary force with a sensitive force sensor. The force is presumably induced when a periodic transient Mach effect mass fluctuation is driven in high voltage, high energy density capacitors that are subjected to 50 kHz, 1.3 kV amplitude voltage signal, and threaded by an alternating magnetic flux of the same frequency. An effect of the sort predicted is shown to be present in the device tested. It has the expected magnitude and depends on the relative phase of the Mach effect mass fluctuation and the alternating magnetic flux as expected. The observed effect also displays scaling behaviors that are unique to Mach effects. Other tests for spurious signals suggest that the observed effect is real.
What we need to demonstrate the validity of Mach’s principle as formulated, then, is experiments that detect effects other than simple inertial reaction forces themselves derived from the assumption that gravity is the cause of inertia. Such effects must have a unique Machian signature so that they cannot be ascribed plausibly to any other cause. Are such effects predicted? Yes. Predictions of this sort have been available in the published literature for more than a decade.7 The predicted phenomena in question arise from considering the effect of an “external” accelerating force on a massive test particle. Instead of assuming that such an acceleration will lead to the launching of a (ridiculously minuscule) gravitational wave and asking about the propagation of that wave, one assumes that the inertial reaction force the accelerating agent experiences is caused by the action of, in Sciama’s words, “the radiation field of the universe” and then asks, given the field strength as the inertial reaction force per unit mass, what is the local source charge density at the test particle? The answer is obtained by taking the four-divergence of the field strength at the test particle