Chapter IV 



THE RUNNING-DOWN OF THE UNIVERSE 



Shuffling. The modern outlook on the physical world is 

 not composed exclusively of conceptions which have 

 arisen in the last twenty-five years; and we have now 

 to deal with a group of ideas dating far back in the last 

 century which have not essentially altered since the 

 time of Boltzmann. These ideas display great activity 

 and development at the present time. The subject is 

 relevant at this stage because it has a bearing on the 

 deeper aspects of the problem of Time; but it is so 

 fundamental in physical theory that we should be bound 

 to deal with it sooner or later in any comprehensive 

 survey. 



If you take a pack of cards as it comes from the 

 maker and shuffle it for a few minutes, all trace of 

 the original systematic order disappears. The order wiil 

 never come back however long you shuffle. Something 

 has been done which cannot be undone, namely, the intro- 

 duction of a random element in place of arrangement. 



Illustrations may be useful even when imperfect, and 

 therefore I have slurred over two points, which affect 

 the illustration rather than the application which we are 

 about to make. It was scarcely true to say that the 

 shuffling cannot be undone. You can sort out the cards 

 into their original order if you like. But in considering 

 the shuffling which occurs in the physical world we are 

 not troubled by a deus ex machina like you. I am not 

 prepared to say how far the human mind is bound by the 

 conclusions we shall reach. So I exclude you — at least 

 I exclude that activity of your mind which you employ 



63 



