142 THE ANATOMY OF SCIENCE 



be irreversible; not that its initial condition 

 cannot be restored, but if it is, it is always at 

 the expense of something else that is running 

 further down. In technical language, the en- 

 tropy of one system may become less, but only 

 if that of other systems increases by at least as 

 much. 



Thus all things are supposed to be moving 

 toward a final state of equilibrium where all 

 happenings cease. Even though it is not claimed 

 that this changeless Nirvana would ever be 

 reached in finite time, this picture of a universe 

 moving toward old age and ultimate death has 

 seemed to many a gloomy one. I am therefore 

 glad to express the belief to which I have re- 

 cently come, that there is no evidence for the 

 hypothesis of continual degradation. 



Astronomy seems to show no cosmic running- 

 down. Some stars fade but others grow brighter. 

 The sun is constantly pouring upon the earth a 

 great flood of energy and apparently without 

 recompense. The source of this energy is still 

 a complete m^^stery, but there is no evidence 

 that it is giving out. Many geologists now be- 

 lieve that as far back as the history of the 

 earth's crust can be traced, perhaps a thousand 

 million years, during which great climatic flue- 



