Newton's Third Law in the Framework of Special Relativity for Charged Bodies

TL;DR

This paper explores how Newton's third law is modified in special relativity for charged bodies, showing that action and reaction forces cannot be simultaneous due to signal propagation limits, leading to potential relativistic engines.

Contribution

It extends previous work by analyzing charged bodies without assuming macroscopic neutrality, investigating implications for electric relativistic engines.

Findings

Newton's third law does not strictly hold in relativistic systems.

Finite signal speed causes non-zero total force in distributed systems.

Charged bodies can potentially be used to develop relativistic engines.

Abstract

Newton's third law states that any action is countered by a reaction of equal magnitude but opposite direction. The total force in a system not affected by external forces is thus zero. However, according to the principles of relativity, a signal cannot propagate at speeds exceeding the speed of light. Hence the action and reaction cannot be generated at the same time due to the relativity of simultaneity. Thus, the total force cannot be null at a given time. In a previous paper \cite{MTAY1}, we have shown that Newt\-on'n third law cannot strictly hold in a distributed system, where the different parts are at a finite distance from each other. This is due to the finite speed of signal propagation, which cannot exceed the speed of light in the vacuum. A specific example of two current loops with time dependent currents demonstrated that the summing of the total force in the system does not add up to zero. This analysis led to the suggestion of a relativistic engine \cite{MTAY3,AY1}. As the system is affected by a total force for a finite period, the system acquires mechanical momentum and energy. Now the question then arises how can we accommodate the law of momentum and energy conservation. The subject of momentum conversation was discussed in \cite{MTAY4}, while preliminary results regarding energy conservation were discussed in \cite{AY2,RY,RY2}. Previous analysis relied on the fact that the bodies were macroscopically natural, which means that the number of electrons and ions is equal in every volume element. Here we relax this assumption and study charged bodies, thus analyzing the consequences on a possible electric relativistic engine.