Solar Influence on the Earth ^ 



By John W. Evans 



Superintendent, Upper Air Research Observatory 



Air Force Cambridge Research Center 



Sacramento Peak 



Sunspot, N. Mex. 



Although the sun is the great provider of the necessities for life, 

 most of us know rather little about it simply because it is so thoroughly 

 reliable. We do not have to worry about whether we shall receive 

 our daily quota of solar energy tomorrow. A very long history of 

 unfailing performance justifies the belief that we shall. In fact, an 

 astronomer friend recently offered to bet me a dollar at odds of 10 to 

 1 that the sun would still be shining 1 billion years from now. He 

 made the proviso that he should hold the stakes. After computing 

 the interest on $1 for 1 billion years, I decided that this was a mere 

 swindle. The winning of the bet pales into insignificance compared 

 to the compound interest on a dollar for a billion years — a figure so 

 large that even our Government has not found a name for it. 



Since the sun is so reliable we devote our worries to more worthy 

 problems, such as whether it will rain in Texas, or whether the Sen- 

 ators can beat the Yankees, since these matters are highly uncertain. 

 There are, however, a few peculiar sun worshipers residing on moun- 

 tain peaks and at other odd places, surrounded by telescopes and spec- 

 troscopes and radio gadgets, who take the sun very seriously. They 

 are finding that in some things the sun is very capricious and quite 

 unreliable. Until recently this had so little effect on our daily lives 

 that we were not even aware of it. But with the rising complexity 

 of our teclinology and our dependence on delicate devices that are 

 \Tilnerable to small disturbances, we are becoming increasingly aware 

 of the effects of these minor solar variations, although most of us do 

 not recognize the sun as the root of our troubles. It is these minor 

 solar variations and their terrestrial effects that concern us here . 



I am sure you are familiar with the effect of fading on your radios. 

 Usually stations come in strong and clear from tremendous distances, 



' Twenty-first James Arthur lecture, given under the auspices of the Smith- 

 sonian Institution on May 27, 1954. 



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