472 



SCIENCE 



[N. S. Vol. XXXVIII. No. 979 



less at the starting point might have given place 

 to new generations. For the organism in motion 

 time was but a moment, if its speed approached 

 the velocity of light. This is a necessary conse- 

 quence of our fundamental assumptions and one 

 which experience imposes on us. 



Let us return to the experiment of Michel- 

 son and Morley with which we started. Let us 

 interpret it by means of our model. We have 

 spoken of the sun and earth in uniform trans- 

 lation through space; let us symbolize this by 

 the moving system of our model, the clock at 

 zero being the sun, and the clock at 60 repre- 

 senting the earth; let us send a light flash in 

 the direction of their common translation; it 

 starts from the sun, A^ at 12 o'clock and 

 reaches the earth, J5^ at 8 o'clock (Fig. 5), 

 thus 8 units of time have elapsed. Lf we send 

 the light flash against the sun and earth trans- 

 lation, then 5' becomes the sun and 4' the 

 earth; the light flash leaves the sun, J5^ at 8 

 o'clock and again reaches the earth, AS at 4 

 o'clock, 8 units of time having elapsed, exactly 

 as is the ease when sun and earth are at rest 

 (Fig. 3). 



The assumptions of the principle of relativ- 

 ity are : 



1. That among all fixed star systems not one 

 is unique — that as far as physical phenomena 

 are concerned it is immaterial upon what sys- 

 tem of reference we base measurement. 



2. When a light-pulse or particle travels 

 through empty space the ratio of distance tra- 

 versed to the time taken to go that distance, 

 both measured in any physical system whether 

 considered at rest or in translation, is in- 

 variant. 



These two assumptions are interpretations 

 of experimental facts, and the conclusions de- 

 duced from them as given in this paper can- 

 not be invalidated unless these primary as- 

 sumptions are shown to be misinterpretations 

 of experiment. 



To what conclusion in respect to an inter- 

 stellar ether' does the principle of relativity 



' H. A. Lorentz, PhysiTcalische Zeitsohrift, 11 : 

 1234, 1910; Max Planck, p. 110, "Acht Vorles- 

 ungem" (Columbia Lectures, 1910); Geo. B. 

 Pegrara, Educational Review, 41: 290, 1911; 



lead us? That there is no place for the 

 ether hypothesis. If the latter were correct, 

 the ether would possess uniqueness which the 

 first assumption of relativity denies to all 

 bodies occupying space. Primitive man en- 

 dowed our earth with uniqueness, but the Co- 

 pernican controversy, though long and bitter, 

 was final. The ether hypothesis has been 

 very helpful to the physicist, and like a crutch 

 to a cripple, it may yet be retained for some 

 time to come, though mathematical analysis 

 has deprived it of even the shadow of an 

 existence. 



The theory of relativity says that Michel- 

 son's experiment, far from being negative as 

 Michelson thought, was exactly what was to be 

 expected. How could an ether drift be estab- 

 lished when the ether had no physical ex- 

 istence ? 



Relativity theorists are reconsidering New- 

 ton's suggestion as to the corpuscular struc- 

 ture of light and a new theory of radiation 

 based upon the idea of quanta [discrete physi- 

 cal energy elements] is now being worked out 

 in Germany and Holland. Newton's theory 

 gave us an easy explanation of the aberra- 

 tion of light, discovered by Bradley, the astron- 

 omer royal of England, in 1727. He found 

 that in order to see a star through a telescope, 

 the latter must not be directed along the line 

 from the eye to the star, but must be inclined 

 in the direction of the earth's motion, just 

 as a sportsman aims ahead of his fleeing prey. 

 On the ether hypothesis no satisfactory explan- 

 ation for aberration can be found.' A tele- 

 scope filled with water was directed toward a 

 star :" since the speed of light through water 

 is three-fourths of the speed of light through 

 air, a large variation in the angle of aberra- 

 tion was expected ; but the variation found was 

 far from what theory had predicted. 



Albert P. Carmon, School Science and Mathe- 

 matics, 13: 1, 1913; M. Laue, FTiysih. Zeitschrift, 

 13: 118, 1912; Norman Campbell, Fhysih. Zeit- 

 schrift, 13: 120, 1912. 



' H. A. Lorentz, ' ' Electrische Erscheinungen, ' ' 

 1906, p. 1. 



''Airy, Froc. Boy. Soc. London, 20: 35, 1871; 

 21: 121, 1873; Phil. Mag., 43: 310, 1872. 



