174 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 8 



would consume a somewhat longer time and the interval between 

 periods of maximum oscillation of the solar atmosphere resulting 

 would be very different from what it is in the case of Jupiter. It 

 must be borne in mind that from the point of view of the tidal effect 

 on the sun, the tide-raising forces of Venus and Mercury and the 

 Earth are not much inferior to that of the planet Jupiter. When we 

 know more about the hydrodynamics of the solar atmosphere so that 

 it will be possible with reasonable assumptions to calculate the antici- 

 pated periods of free oscillations, we might then have a quantitative 

 method for testing the validity of such a hypothesis. 



The theory lends itself to considerable elasticity since at higher 

 solar latitudes where the tangential tidal force is greatest, the period 

 of rotation of the sun is considerably longer than at the equator. One 

 might expect on such a hypothesis that the observed sunspot period 

 would be the resultant of several oscillatory waves set up by the sev- 

 eral planets. The composite curve might, under selected conditions, 

 have a mean period between maxima equal to the known sunspot 

 period of 11.3 years, and in many instances there would be wide vari- 

 ations from the mean of this cycle. 



This theory would be consistent with the fact that the spots origi- 

 nate in the region of the 40° latitude zone where the tangential com- 

 ponent of the tidal forces tend to a maximum, and not inconsistent 

 with their subsequent migration toward the solar equator. Until a 

 mathematical treatment of free oscillations in the sun based upon more 

 information than is available at present can substantiate such a 

 hypothesis, we can but continue to speculate. 



In the space of an hour we have seen a few of the important ways 

 in which the sun and the atmosphere with a balanced nicety provide 

 the essentials of life. We find that changes in the sun find quick 

 response in this atmospheric envelope which surrounds us. Climate, 

 weather, radio communication, and perchance terrestrial effects yet to 

 be discovered may some day become predictable through cycles that 

 follow law and order. Is it possible that astronomy, the oldest of 

 the sciences, which first intrigued man's study of the sky in the hope 

 of guiding human destiny, may once more be turned again to earth 

 and, with the knowledge gained from suns and galaxies, lead mankind 

 to a more intelligent adjustment of life to its cosmic environment for 

 the betterment of all? 



If such is but a dream, it is at least a dream well worth the quest. 

 We may surmise that in our search the guiding star of human destiny 

 will be the sun. 



