Relatively Speaking

It's reassuring to know that some things don't change; that amid the revolutions and revisions of cosmology in the last decade, nobody has repealed Einstein's theories of special and general relativity. Indeed, in Chaisson (Astrophysics/M.I.T. & Harvard), Einstein has a reverent disciple. Not only does he make use of extensive quotes and examples of Einstein's style of thinking, he devotes a chapter to Einstein's pronouncements on politics, morality, and religion. Elsewhere, Chaisson thoughtfully explicates, first, the special theory (called "special" because it deals with the special cases of frames of reference moving at uniform velocities), then the general theory. The consequences of special relativity theory lead to the well-described phenomena of shrinking yardsticks, increasing mass, and time dilation. General relativity deals with variable motion - accelerations and decelerations - and, through one of the great thought experiments, establishes the equivalence of gravity with the curvature, or warping, of spacetime in the presence of mass. Chaisson's analogy of space as a rubber trampoline serves him well when he applies general relativity theory to the concept of black holes - the hole can be considered as a bubble formed as the rubber turns in upon itself because of a superheavy point mass. Chaisson relates Einstein's theories with the still unanswerable questions of whether the universe is open, closed, or flat. In his final chapters, he weighs the evidence for the existence of black holes either at the center of the Milky Way, at the outer depths of the universe, in mysterious binary pulsars, or in the form of mini-holes. In many ways this is a satisfactory volume that reinstates the importance of Einstein's contributions and their relevance to modern cosmology - in spite of Einstein's denial of quantum theory. (Kirkus Reviews)