THE EXPLANATION OF I'AWS 



bodies on the earth, tnat the planets were subject to 

 forces, and had determined what those forces were. 

 What more could he do ? What explanation of his result 

 could be offered or even demanded. He had ordered the 

 solar system, and who could be so foolish as to ask why 

 the order was that which he had found and no other ? 

 But after his morning's work which finally completed his 

 forthcoming treatise on the matter, he sat in his orchard 

 and was visited by some of his friends from Cambridge. 

 Perhaps they too were natural philosophers and he talked 

 to them about what he had been doing ; but it is more 

 likely that they sat idle, talking the thin-blooded intel- 

 lectual scandal that must have always flourished in 

 academic society, while Newton played with the historic 

 kitten. 



And then the apple fell from the tree. Newton was 

 suddenly silent in a reverie ; the kitten played unheeded 

 with the fallen fruit ; and his friends, used to such sudden 

 moods, laughed and chattered. After a few moments he 

 must have paper ; he rushes to his desk in the house ; 

 scribbles a few hasty figures ; and now the theory of 

 gravitation is part of the structure of the universe. The 

 falling apple, a trivial incident which he had seen a 

 thousand times before, had loosed a spring in his mind, 

 set unconsciously by all his previous thought. He had 

 never consciously asked himself why the moon was pulled 

 towards the earth until, in an instant of revelation, the 

 apple appeared to him not " falling " (the meaningless 

 word he had always used before), but pulled towards the 

 earth. The idea flashed on him quicker than it could 

 be spoken. If both the moon and the apple are pulled 

 towards the earth, may they not be pulled by the same 

 force ? May not the force that makes the apple " fall " 

 be that which restrains the moon in its orbit ? A simple 

 calculation will test the idea. He knows how far the 

 moon is from the earth and how the force on it varies 



