NOTES 91 



The pull of the sun on the sphere is 



3 H 



where p is its density, G is the gravitation constant, and 

 M is the mass of the sun. 



If light repulsion is n times gravitation pull, 



i'7S x io 6 4 GM 



A 



= n - ap x 0*59 



o 

 C* TVT 



for ~ is the acceleration of the earth in its orbit, and 

 is equal to 0-59 cm. /sec. 2 ; 



whence OP = . . nearly. 



4/z io 4 



If n = i and p = 5*5 we get 



<,-!! cm. 



10 



If n = i and p = i we get 



a = 1\ cm. 



J0 b 



We see that a would be inversely proportional to n if 

 the repulsion continued according to the same law. But, 

 as stated in the text, diffraction comes into play when a 

 is very small, and the ratio of light pressure to gravita- 

 tion pull diminishes when a is reduced below a certain 

 value. The maximum ratio is probably when a is about 



> cm. for p = i. 



