For purchase of this item, please read the instructions.
Volume 12: Pages 131-145, 1999
Beyond the Equivalence Principle
Departamento de Fisica, Universidade Federal do Paraná, CP 19081, CEP 81531-990, Curtiba, Paraná, Brazil
After a historic review of different points of view on the equivalence principle (EP), we analyze the concepts related to the interpretation and the confrontation of experimental results with theoretical predictions. In order to debate the EP, we examine the processes of interaction of electromagnetic radiation with matter in the light of this principle, and the issue of whether or not the weak equivalence is in conflict with Mach's principle. In spite of the fact that the EP holds for purely mechanical processes, we propose gedanken and feasible experiments, which suggest that in the processes of emission or absorption of electromagnetic radiation by matter the strong version of this principle is not valid in certain circumstances. However, as a γ‐ray source falls from a height h toward a detector on the ground, a change occurs in the gravitational shift of the frequency of the photons emitted by this source. The decrease in h is the cause of this change, which is equal, in absolute value, to the corresponding change in the transverse Doppler effect caused by the increase in the source's velocity with respect to the detector. Invoking the fact that, dynamically, the transverse Doppler effect is related to the increase in the inertial mass of the source due to its motion with respect to the detector, we interpret the equality between inertial mass (attribute of inertia) and gravitational mass (attribute of “gravitational charge”) as a consequence of Einstein's principle of the inertia of energy.
Keywords: electromagnetic interaction and equivalence principle, gedanken and feasible tests of the equivalence principle, gravitational shift of frequency and transverse Doppler effect, gravitational mass and Einstein's principle of the inertia of energy, gravitational redshift and inertia of gravitational potential energy, weak equivalence and Mach's principle
Received: August 4, 1998; Published online: December 15, 2008