346 L. Page — A Century's Progress in Physics. 



space than twenty centuries of introspection on the part 

 of professional philosophers. Minskowski, whose prom- 

 ise of greater achievement was cut off "by an untimely 

 death, has shown that four dimensional geometry makes 

 possible the representation with beautiful simplicity of 

 the time and space relationships of this theory. The 

 one time and three space dimensions merge in such a 

 manner as to form a single whole with not a vestige of 

 differentiation between these fundamental quantities. 

 Wilson and Lewis 15 have made this representation famil- 

 iar to American readers through their admirable trans- 

 lation of Minskowski 's work into the notation of Gibbs's 

 vector analysis. 



Aberration, the Doppler effect, anomalous dispersion, 

 — indeed all known phenomena, — are found to be in 

 accord with the principle of relativity. It must be 

 borne in mind, however, that this principle applies only 

 to systems moving relative to one another in straight 

 lines with constant velocities. That there is something 

 absolute about rotation has been recognized since Fou- 

 cault performed his famous pendulum experiment in 1851. 

 This experiment (C. S. Lyman, 12, 251 and 398, 1851) 

 consisted in setting a pendulum composed of a heavy 

 brass ball suspended by a long wire into oscillation in 

 such a way as to avoid appreciable ellipticity in its 

 motion. Observation of the rate at which the ground 

 rotates relative to the plane of vibration of the pendulum 

 furnished a method of measuring the rotation of the 

 earth about its axis ivithout reference to celestial bodies. 

 The gyroscopic compass in use to-day provides yet 

 another terrestial method of detecting this rotation. 



The Future of Physics. — At times during the history 

 of physics it has seemed as if the fundamental laws of 

 this science had been so completely formulated that 

 nothing remained to future generations beyond the 

 routine of deducing to the full the consequences of these 

 laws, and increasing the precision of the methods used 

 to measure the constants appearing in them. That 

 Laplace held this view has already been pointed out, and 

 Maxwell, in his introductory lecture at the opening of the 

 Cavendish laboratory in 1871, said, "This characteristic 

 of modern experiments — that they consist principally of 

 measurements — is so prominent, that the opinion seems 



15 E. B. Wilson and G. N. Lewis, Proc. Am. Acad, of Arts and Sci., 48, 

 389, 1912. 



