Stormy Weather on the Sun^ 



By Walter Orr Roberts 



Superintendent of the High Altitude Observatory, Boulder, Colo. 



[With 2 plates] 



Astronomy has come a long way from the heyday of ancient Greece 

 when Socrates admonished the astronomers to sticlv to their proper 

 business, the calendar, and advised them that "speculators on the 

 universe and on the laws of heavenly bodies are no better than mad- 

 men." Instruments to observe the sun, likewise, have progressed 

 far beyond the simple pinhole viewer with which Fabricius watched 

 the sunspots. 



But for all our progress, the sun worries us yet with the many un- 

 solved riddles of its behavior. We no longer hold, with Aristotle, 

 that the sun and moon are living beings. But we are still at a loss 

 to explain many features of its behavior, such as the fact that the 

 sun's equator rotates faster than its higher latitudes. 



To solve these diverse problems, many of our greatest astronomers 

 from Galileo's day to the present have devoted major portions of their 

 scientific careers to the study of the sun and the features of its at- 

 mosphere. The growth of our knowledge has been vastly encouraged 

 by such people as C. G. Abbot of the Smithsonian Institution, G. E. 

 Hale of Mount Wilson Observatory, Father Secchi of the Vatican, 

 Sir Norman Lockyer, Robert R. McMath, L. d'Azambuja, C. E. Saint- 

 John, Bernard Lyot, and many others. And in the course of their 

 work astronomers have given the name of the sun to a whole class 

 of new astronomical instruments, such as helioscopes, pyrheliometers, 

 spectroheliographs, heliometers, heliostats, coronagraphs. As the 

 rears pass, increasingly powerful tools of modern science are brought 

 to bear upon the sun. And the riddles of its behavior are gradually 

 yielding to analysis. 



The clues to a great number of the mysteries of solar behavior 

 seem to be locked up in the sun's atmosphere — in the phenomena that 

 become spectacularly visible during total solar eclipse. And it is 



^ Eighteenth Tnmes Arthur lecture, given under the auspices of the Smithsonian Institu- 

 tion on March 22, 1951. 



Ifi3 



