AND OF THE SECOND LAW 39 



requirement that entropy must be tied down to the condition of 

 " elementary chaos " (elementare-unordnung). 



We have already dwelt somewhat fully on this hypothesis of 

 " elementary chaos." 



" It follows from this presentation that the concepts of entropy 

 and temperature in their essence are tied to the condition of 

 " elementare Unordnung." Thus a purely periodic absolute 

 plane wave possesses neither entropy nor temperature because 

 it contains nothing whatever in the way of uncheckable, non- 

 measurable magnitudes, and therefore cannot be " elementar- 

 ungeordnet," just as little as can be the case with the motion of 

 a single rigid atom. When there is [an irregular co-operation of 

 many partial oscillations of different periods, which independently 

 of each other propagate themselves in the different directions of 

 space, or] an irregular, confused, whirring intermingling of many 

 atoms, then (and not till then) is there furnished the preliminary 

 condition for the validity of the hypothesis of " elementare Unord- 

 nung and consequently for the existence of entropy and of 

 temperature." 



" Now what mechanical or electro-dynamic magnitude repre- 

 sents the entropy of a state? Evidently this magnitude depends 

 m some way on the " Probability " of the state. For because 

 " elementare Unordnung " and the lack of every individual check 

 (or measurement) is of the essence of entropy it follows that only 

 combination or probability considerations can furnish the necessary 

 foothold for the computation of this magnitude. Even the 

 hypothesis of " elementare Unordnung " by itself is essentially 

 a proposition in Probability, for, out of a vast number of equally 

 possible cases, it selects a definite number and declares they do 

 not exist in Nature." 



Now since the idea of entropy, and likewise the content of 

 Second Law, is a universal one, and since, moreover, the 

 theorems of probability possess no less universal significance, we 

 may conjecture (surmise) that the connection between Entropy 



