Inertial and Gravitational Mass In Relativistic Mechanics

Abstract

In several recent papers in the field of relativistic mechanics, the concept of the mass of bodies plays a very subordinate role. The reason is easy to understand. As Laue1 and Herglotz2 have shown, one can develop the entire mechanics of extended bodies without exploiting the concept of inertial mass in any way. Thus the concept of mass is not absolutely essential for mechanics, and on the other hand, if one considers bodies subject to arbitrary elastic stresses, this concept is also not sufficient to describe all inertial phenomena of matter. But the question of the mass of matter is nevertheless of considerable importance for the theory of relativity, especially for the assessment of the way in which the theory of gravitation is to be integrated into the theory of relativity. In any case inertia and gravity Schwere of matter must stand in close relation to each other, and it would be easiest to account for this unity of essence Wesenseinheit via the mass underlying these two phenomena. One would attempt to retain such a concept of mass, even though it is known that according to relativity theory there exist inertial phenomena which cannot be traced back to mass in any way. In such cases, one must make use of a specially defined momentum, which depends, for example, upon the state of elastic stress of a body rather than upon its mass.