Towards a New Concept of Closed System: From the Oscillating Universe to the EM-Drive

The EM-Drive, as long as it is considered a closed system, explicitly violates the conservation of momentum and Newton's well-known third law: however, it would appear, according to several tests to date, that the device may concretely deliver a certain thrust without a detectable exhaust. The question is: can the EM-Drive be actually regarded as a closed system? We have elsewhere tried to provide a qualitative answer by resorting to a theory based, amongst other hypotheses, upon the existence of a further spatial (hidden) dimension. In this paper, the whole revised theory is step-by-step expounded, avoiding, for the sake of brevity, some aspects that, notwithstanding their undeniable relevance, do not concretely contribute to the achievement of our main goal. We consider a Universe belonging to the so-called oscillatory class. Firstly, we formally show that, as it is well known, a simple-harmonically oscillating Universe is fully compatible with General Relativity. Then, we carry out an alternative deduction of the mass-energy equivalence formula as well as of the Friedmann–Lemaître equations. Finally, by resorting to an opportune writing of the conservation of energy (carried out by taking into account the alleged extra spatial dimension), we implicitly obtain a new definition of closed system, so providing an answer to the question previously posed.