Understanding the Universe's Dark Matter

James Trefil is well known as a science writer who can explain complex physics in simple ways. In "The Dark Side of the Universe" he has used his unusual talents to describe one of the latest of the problems that confront astronomers—the nature of the dark (invisible) matter, which many astronomers believe comprises the bulk of the mass and energy of the universe, and the way in which it bears on the structure and evolution of the universe. In a nutshell, his theme is that we all now believe that the universe started in a hot big bang (he quotes a 99% probability); that there is just enough mass in the universe so that it does not expand forever (that is, to close it); that most of this matter is not normal baryonic matter (protons, neutrons, and heavier nuclei); that we do not understand how galaxies of stars formed but are on the way to ...