In a recent article by Lewis and Tolman[1] a non-analytical method was developed for obtaining the more important conclusions which can be drawn from the principle of relativity. Our reasoning was based only upon the first and second postulates of relativity, and those fundamental conservation laws of mass, energy and momentum which science has never in a single instance been forced to abandon. Since the method of attack avoided any use of involved mathematical analysis, restricting itself to the simplest processes of logical reasoning, and, further, made no use of the assumptions of electromagnetic theory, it may be concluded that the unexpected nature of the results of the theory of relativity is due to something unusual in the two postulates of relativity themselves.
No objections have ever been made to the first postulate of relativity, as stated in its original form by Newton, that it is impossible to measure or detect absolute translatory motion through space. In the development of the theory of relativity, this postulate has been modified to include the impossibility of detecting translatory motion through any ether or medium which might be assumed to pervade space. In support of this principle is the general fact that no "ether drift" has ever been detected, but,
- ↑ Lewis and Tolman, Proc. Amer. Acad., 44, 711-724, 1909; Phil. Mag., 18, 510-23, 1909. A novel method of proof was adopted in this article which consisted in the consideration of certain experiments which might be performed by two observers situated on similar systems which are in relative motion. The reasoning was based on the supposition that the results obtained in such experiments would not contradict either of the two postulates of relativity nor the conservation laws of mass, energy and momentum. These supposed experiments are analogous to the cyclical processes used in thermodynamic proofs, and bear the same relation to the analytical method used by Einstein in his treatment of the theory of relativity, as the "cyclical process" method bears to the more elegant considerations of the analytically inclined thermodynamist.
