Contemporary Advances in Physics. XIV. Introduction 

 to Wave-Mechanics 



By KARL K. DARROW 



IN a period when a limited domain of physical phenomena is exciting 

 wide fervent interest and commanding intensive study, and con- 

 tinues for years to monopolize the attention of many brilliant theorists, 

 sometimes it is the fortune of an ingenious mind to express or interpret 

 or picture the already-discovered laws in a new way which makes so 

 greatly favourable an impression, that in a moment it sweeps its rivals 

 from the field. The new theory may not lead to more or better agree- 

 ments with experience than did its predecessors; it need not make 

 predictions which they were incapable of making; its mathematical 

 processes may be identical with theirs, the old symbols reappearing 

 with new names in the old equations. Contrariwise it may be born 

 well endowed with these advantages which normally decide the contest 

 between old theories and new, yet owe its victory not to them at all. 

 It triumphs because it seems natural or sensible or reasonable or elegant 

 or beautiful — words said of a theory which fulfils some deep-seated de- 

 mand or evades some deep-rooted prejudice in the minds of its judges. 

 Later its vogue may pass, not through the disclosure of any intrinsic 

 defect, but because the physicists of the rising generation do not share 

 the prejudices and the predilections of those who first applauded it. 

 The kinetic theory of gases was welcomed by a generation which wished 

 to believe in atoms; the electromagnetic theory by people prejudiced 

 against the notion of action at a distance; the quantum-theory has 

 always had to do battle against those who yearn for continuity in 

 their images of Nature, and the theory to which these pages are devoted 

 has captivated the world of physics in a few brief months because it 

 seems to promise a fulfilment of that long-baffled and insuppressible 

 desire. 



Wave-mechanics being a new way of interpreting a vast field of 

 well-known phenomena, it is unnecessary as indeed it would be 

 impossible for me to recite in this place everything which the new 

 theory is meant to explain. A few years hence, indeed, we may rec- 

 ognize in certain phenomena only newly or not yet discovered the 

 securest basis for the new conceptions; but for the present, any ade- 

 quate description of the facts on which Bohr's atom-model is based is 

 nearly sufficient. I will recall only that the cardinal and dominant 

 facts of the field which is the hunting-ground of the present generation 



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