AND Their Effects byHARLAN TRUE STETSON Research Associate at the Massachusetts Institute of Technology Author of B STARS AND THE STAJLS Yorfc WHITTLESEY HOUSE London MCGRAW-HILL BOOK COMPANY, INC. of and trireless i t tie cii Sciilt field of solar - t erTes trial FOREWARNING THE near approach of another sunspot maximum with the accompanying interest shown by the press and the general public gives the occasion for a book on sunspot s. So much has been said about the possibilities of sunspots affecting the earth and human affairs that a candid discussion of sunspots and their effects is due the general reader who would keep himself informed of trends in science. Sunspots have been blamed for calamities and misfortunes that run the gamut from Florida hurricanes to financial panics. Is there any basis whatever for such assumptions Since we are all more interested in ourselves than we are in things, the book has been written from the human point of view. While statements have been qualified, various possible hypotheses have been dis cussed which bear upon the question of solar dis turbances and affairs on the earth. Perhaps all too long has the reading public been dependent upon the technical material in textbooks on astronomy for a knowledge of sunspots. Such textbooks which must deal only with well-established facts cannot naturally try to discuss speculative questions. This book therefore departs from the usual type of book on science in that it frankly presents questionable material as well as the results of more completely Forewarning established facts from which the reader may draw his own conclusions with respect to inferences not yet fully established as weU as to those which may beregarded as beyond debate. As the book is intended to be distinctly popular, the more speculative material which intrigues the imagination has been presented in the earlier part, leaving the more well-established effects of sunspots upon the earth to the later chapters. The book undoubtedly raises more questions than it answers, and will, it is hoped, suggest attention to some of the less conventional aspects of the question concerning the influence of the sunspots on world events. So many apparently serious articles have been written concerning sunspots and the business cycle that a chapter is devoted to the more plausible hypoth eses that may be worth investigation If the author appears noncommittal in his interpretation of some of the more startling presentations, it is because a scientist cannot by nature be otherwise. On the other hand, I have refrained from condemning interpretations where evidence is still scanty, for thus to condemn appears to me as unscientific as to make positive statements where complete evidence is wanting. If the book falls into the hands of the overcredulous, perhaps a word of warning is necessary to curb hurried conclusions. One can only hope that none of the more speculative statements will be quoted except with qualifications which go therewith. Forewarning In the closing chapter I have endeavored to differ entiate clearly between the several effects well established and scientifically recognised from those which are more speculative and require much further investi gation before definite conclusions can be drawn. Only by such differentiation can the whole subject be clarified with the door still open for future progress. A scientific reader will misstechnical phraseology and numerous references quoting sources which obvi ously are out of place in so popular a presentation. If the reading of the book stimulates a consciousness of mans cosmic surroundings and opens certain ques tions for serious consideration, the answers to which are yet to come, the purpose of the book will in a meas ure be realized. HARLAN TRUE STETSON. CAMBRIDGE, MASSACHUSETTS, September, 1937...