Long‐Term Solar Variability: Evolutionary Time Scales

Abstract : Galileo, who played a central role in the modern discovery of sunspots, may have wondered whether the Sun varies. Certainly, his 17th century contemporaries did. The Sun itself all but answered this question a few decades later when it nearly stopped forming sunspots as it entered what is now known as the Maunder Minimum. Herschel's speculation that the price of wheat might be related to the number of sunspots indicates that the possibility of solar variability was firmly established in the scientific thought of the late 18th century (Eddy, 1983). In the mid-19th century, the approximately 11-year variation in sunspot number was recognized, apparently first by Schwabe.