PHILOSOPHY OF PHYSICS MILNE 225 



ferent events. Which tmie is the one indicated by thermodynamics? 

 Does thennodynaniics indeed select a special time, which we could 

 call absolute time, and if so what observer experiences this time? 

 Tliennodynaniics appears to say that the system is ageing to all 

 observers ; it does not keep company with relativity. It is not suffi- 

 cient with Eddington to say that the entropy-increasing property 

 gives a point to time's arrow. It is not merely a question of the 

 time sense, the fact that entropy distinguishes one direction of time 

 from the other ; it is that the interval between two states of the uni- 

 verse, corresponding to a given entropy dilference, may apparently 

 be different for different observers. 



Jeans does in fact conclude that there is for the world an absolute 

 time, though he derives this not from thermodynamics but from the 

 structure of the astronomical universe. His view is that absolute 

 time and absolute space exist in a wider external world than that 

 of pure physics, that this absolute space and time are found in 

 astronomical nature, and that so an escape may be found from the 

 relativity view that evolution is meaningless. 



It appears to me, however, that Jeans evades the issue. By astro- 

 nomical nature he means very large scale phenomena, the outward 

 motions of the spiral nebulae, and his conclusion would be solidly 

 based only if these phenomena disclosed something which contra- 

 dicts those conclusions to which we have been led by laboratory 

 experiments. Jeans says that absolute time and absolute space do 

 not enter into the nature we study in our physical laboratories. 

 But how? In. what sense can a large block of space be absolute 

 whilst a small one is not? If the universe contains an absolute 

 frame of reference, it must also be absolute whatever the scale of 

 the phenomena. We cannot, of course, rule out the possibility that 

 very large scale phenomena might disclose generalizations not found 

 to be valid for smaller-scale experiments. But Jeans is talking not 

 of phenomena but of time and space, elsewhere considered as " mental 

 concepts." And which large scale phenomena are in fact the cul- 

 prits? But there is another point. The second law of thermody- 

 namics y's verified for ordinary scale phenomena, so that even for 

 ordinary phenomena we have the apparent conflict between rela- 

 tivity and thermodynamics. Jeans says : " Through our conscious- 

 ness we break up the space-time product into space and time, whilst 

 electrons and radiations and protons cannot." Yet it is not sug- 

 gested that it is due to our consciousness that that aspect of evolution 

 which we call the entropy-increasing property does actually exist. 

 These same electrons and protons which cannot break up space-time 

 into its constituents are the very participants in the drama of the 

 ultimate heat death. In spite of relativity, therefore, they know 



