This book is a very impressive achievement. Kennefick skillfully introduces readers to some of the most abstruse yet fascinating concepts in modern physics stemming from Einstein's gravitational theory. And he charts the often haphazard, meandering, at times contentious development of these ideas over the course of nearly a century. More than an intellectual history, this book is a kind of detective story. Amid unfolding clues, partial insights, evolving institutions, the play of personalities, and hard thinking, the reader is treated to larger lessons about how theoretical physics works. Until now, we had virtually no serious study of what happened to Einstein's general relativity after he published his famous equations. Kennefick is among the first to begin to fill in this story. -- David Kaiser, author of "Drawing Theories Apart: The Dispersion of Feynman Diagrams in Postwar Physics" In this book, Kennefick describes a seventy-year quest, by three generations of physicists, to discover relativity's predictions about gravitational waves. Combining his skills as a historian with his mastery of relativity and his powers as a storyteller, he weaves a compelling narrative of intellectual battles and mathematical struggles--and extracts fascinating insights about the roles of mathematics, intuition, analogy, and style, standards of proof, and the sociology of competing schools. -- Kip S. Thorne, California Institute of Technology This book is a very important contribution both to Einstein studies and to the history of physics in general. It is also very timely given the effort underway to detect gravitational waves. The author is in an absolutely unique position to tell this story. He is extremely well connected to the community of Einstein scholars, to the community of physicists past and present working on gravitational waves, and to the group of people working on the history of the subject. -- Michel Janssen, University of Minnesota

Since Einstein first described them nearly a century ago, gravitational waves have been the subject of more sustained controversy than perhaps any other phenomenon in physics. These as yet undetected fluctuations in the shape of space-time were first predicted by Einstein's general theory of relativity, but only now, at the dawn of the twenty-first century, are we on the brink of finally observing them. Daniel Kennefick's landmark book takes readers through the theoretical controversies and thorny debates that raged around the subject of gravitational waves after the publication of Einstein's theory. The previously untold story of how we arrived at a settled theory of gravitational waves includes a stellar cast from the front ranks of twentieth-century physics, including Richard Feynman, Hermann Bondi, John Wheeler, Kip Thorne, and Einstein himself, who on two occasions avowed that gravitational waves do not exist, changing his mind both times. The book derives its title from a famously skeptical comment made by Arthur Stanley Eddington in 1922--namely, that "gravitational waves propagate at the speed of thought." Kennefick uses the title metaphorically to contrast the individual brilliance of each of the physicists grappling with gravitational-wave theory against the frustratingly slow progression of the field as a whole. Accessibly written and impeccably researched, this book sheds new light on the trials and conflicts that have led to the extraordinary position in which we find ourselves today--poised to bring the story of gravitational waves full circle by directly confirming their existence for the very first time.