240 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



nomena is reversed. The theory thus provides a bridge by means of 

 which the two extreme cases are seen to be not inharmonious, where- 

 as individual theories for each case, formuh^ted on the basis of all 

 that experiment can reveal, would appear at first sight mutually 

 antagonistic. 



However, the language of the bridge which spans electrodynamics 

 and astronomy may not be very simple when asked to speak the story 

 of either of these subjects separately. If I concentrate on the domain 

 which is astronomy, I shall tend to paint pictures and make models 

 characteristic of that end of the bridge, pictures which emphasize very 

 strongly to my intuition the salient phenomena of astronomy, but 

 pictures which would have to become more and more out of focus as I 

 walked across the bridge to the realm of electrodynamics. And when 

 I reached this realm, I would find them completely out of focus and 

 unable to convey to me any meaning at all. On the other hand, if I 

 start at the end of the bridge which is electrodynamics, and do the same 

 kind of thing, I shall paint pictures and make models appropriate to 

 the most important phenomena characteristic of that end. And these 

 pictures will, in turn, become more and more hazy as I cross the bridge 

 to the end concerned with astronomy. If I am a philosopher, and 

 willing to realize the limitations of my pictures at both ends of the 

 bridge, I shall not be disturbed by their becoming hazy as I cross from 

 one end to the other. However, if I am a nonphilosopliical astronomer, 

 the pictures which I have painted, and the models which I have created 

 to understand my subject will be very fundamental to me ; and if I 

 tamper with them my mind will protest that what I am doing produces 

 nonsense. A similar thing will happen for the nonphilosophic student 

 of electrodynamics at the other end of the bridge. He will create his 

 pictures and the elements of his creation will be for him the basis of 

 reasonable understanding. Thus while the philosopher will be able to 

 cross the bridge in contentment in either direction, adjusting himself 

 to the scenery on the way, the nonphilosophic astronomer and the non- 

 philosophic student of electrodynamics will feel that their realms are 

 quite distinct and that the laws of one subject have no connection with 

 those of the other. "\"\liile the general formulation of the philosopher 

 will extrapolate harmoniously, both ways, from one end of the bridge 

 to the other, the more specific pictures and models appropriate to the 

 two ends will not extrapolate, for the elements of these pictures and 

 models which are prominent in the phenomena at one end may be of 

 negligible importance to the phenomena at the other end. 



And yet, at each end of the bridge, the philosophically imperfect 

 pictures appropriate to that end may be more useful than the gener- 

 alized picture painted by the philosopher. Thus, 300 years ago, many 

 believed that light was composed of rays which traveled like arrows 



