458 Messrs. Michelson and Morley on the Relative Motion 



The results of the observations are expressed graphically in 

 fig. 6. The upper is the curve for the observations at noon, 

 and the lower that for the evening observations. The dotted 

 curves represent one eighth of the theoretical displacements. 

 It seems fair to conclude from the figure that if there is any 



Fig. 6. 



— o-osX 



displacement due to the relative motion of the earth and the 

 luminiferous aether, this cannot be much greater than 0*01 of 

 the distance between the fringes. 



Considering the motion of the earth in its orbit only, this 

 displacement should be 



2D^=2DxlO- 8 . 



The distance D was about eleven metres, or 2 x 10 7 wave- 

 lengths of yellow light ; hence the displacement to be expected 

 was 0*4 fringe. The actual displacement was certainly less 

 than the twentieth part of this, and probably less than the 

 fortieth part. But since the displacement is proportional 

 to the square of the velocity, the relative velocity of the 

 earth and the aether is probably less than one sixth the earth's 

 orbital velocity, and certainly less than one fourth. 



In what precedes, only the orbital motion of the earth is 

 considered. Jf this is combined with the motion of the solar 

 system, concerning which but little is known with certainty, 

 the result would have to be modified ; and it is just possible 

 that the resultant velocity at the time of the observations was 

 small, though the chances are much against it. The experi- 

 ment will therefore be repeated at intervals of three months, 

 and thus all uncertainty will be avoided. 



It appears from all that precedes reasonably certain that if 

 there be any relative motion between the earth and the lumi- 



