172 THE WORLD-ENERGY 



and moon must be far greater than the velocity of 

 their approach toward the sun. And the greatest 

 velocity of all, here as elsewhere, must belong to the 

 body having least mass. 



The attractions will all necessarily be exerted along 

 straight lines. For gravitation, as we have seen, is 

 an essential property of the bodies themselves, and what- 

 ever their relative positions, it is necessarily a direct 

 connection of the one with the other. 



We may remark, by the way, too, that this (taken 

 in connection with what has already been said con- 

 cerning the really indefinite extension of even the 

 smallest "bodies") is a simple and natural explanation 

 of the otherwise mysterious fact that gravity "acts" 

 instantaneously through immeasurable distances. Grav- 

 ity is not itself a special form or kind of matter; nor is 

 it, like light or heat or electricity, a special mode of 

 motion requiring time for its propagation through space. 

 On the contrary, it is there always and everywhere in space 

 as itself a necessary aspect or mode of "whatever can 

 occupy space." 



The movements, nevertheless, must be along highly 

 complex curves. For both earth and moon approach the 

 sun at the same time they approach each other. The 

 earth will be drawn, by the moon's attraction, out of the 

 straight line joining its original position with the sun. 

 Meanwhile, the moon itself, as possessing relatively so 

 little mass, will acquire a much greater velocity. And 

 the direction of its movement will be toward the earth in 

 greater degree than toward the sun. At the same time, 

 the earth, as possessing so little mass relatively to the sun, 

 will acquire a velocity mainly in the direction of the sun. 



