A determination of the ratio of mass to weight for a radioactive substance

Abstract

Experiments have been made from time to time by different observers, with a view of testing the constancy of the ratio of mass to weight for various substances. Their results have been uniformly negative so far as indicating any deviation from constancy is concerned. Several years ago an experiment of this nature was undertaken by Prof. Sir J. J. Thomson, who used a pendulum the bob of which was made of radium. The quantity of radium, however, was small, and it was found to be impossible to obtain a very high degree of accuracy. The considerations which led to the supposition that radium might differ from non-radioactive substances in the above respect were as follows:—* “The simplest electrical system we know, an electrified sphere, has attached to it a mass of ether proportional to its potential energy, and such that if the mass were to move with the velocity of light its kinetic energy would equal the electrostatic potential energy of the particle. This result can be extended to any electrified system, and it can be shown that such a system binds a mass of the ether proportional to its potential energy. Thus a part of the mass of any system is proportional to the potential energy of the system.