In the next few years, one of science's grandest speculations will be put to the test of observation as new labs and space observatories begin to gather data on the Big Bang theory. Science writer Riordan ( The Hunting of the Quark ) and Schramm, science professor at the University of Chicago and the Enrico Fermi Institute, focus on the critical search for ``missing mass'' in the observable universe, the so-called dark matter that today's body of theory requires to provide for a stable, yet expanding universe begun with a Big Bang. Their analogies and explications of the theory serve the lay reader well, though they rely entirely on the deductive cosmology that has held sway for the last 20 years. The next 20 may hold more surprises than the Big Bang can account for; recent satellite measurements of large structures in the nearby galaxies directly contradict many of Big Bang's assumptions. The debate itself will be exciting to watch. This book is a good place for readers to catch up on the terms and theories that will be catching the public's attention in the coming decade. (Apr.) .