166 THE ANATOMY OF SCIENCE 



there is no distinction between forward and 

 backward in time, that in the elementary proc- 

 esses occurring between atoms, even in the ex- 

 change of radiant energy, there is no dissym- 

 metry of past and future, how can we believe 

 in such dissymmetry in a so-called irreversible 

 process? What mysterious element do we intro- 

 duce when we proceed from two or three atoms 

 to a million or more? We have seen that the 

 irreversible process does not really exist and 

 that the sense of mystery is only due to our un- 

 familiar ity with large numbers. We may there- 

 fore conclude that in all physics, including 

 thermodynamics, there is no need of introduc- 

 ing a distinction between past and future, nor 

 any concept of time except what we have called 

 two-way time, which may be regarded as only 

 one mode of extension in our four-dimensional 

 manifold of kinematics. 



Whence then arises the extraordinary dis- 

 symmetry with respect to past and future which 

 we meet in everyday life? For one thing we 

 have a steady flow of energy from the sun which 

 is, as it were, constantly throwing sorted decks 

 of cards into our great shuffling machine, and 

 as we watch them pass from the describable ar- 

 rangements to the nondescript we have a sensa- 



