The Wraparound Universe

The aim of this book is to describe a particular approach to cosmology, known as cosmic topology, that seeks to discover the overall size and shape of the universe, one of the biggest questions in cosmology for more than 25 centuries. Along with a small group of collaborators, I have tenaciously defended this approach for more than a decade against the skeptical—and, as it seemed then, “reasonable”—opinions of the majority of researchers in the field. In fact, one of the most surprising possible conclusions of our wraparound universe models is that of a physical space that is smaller than the apparent one that we explore through telescope observations of celestial objects. As a consequence, some portion of distant light sources must be nothing more than “ghosts,” their light reflected back to us from the depths of a strangely shaped space, which is folded in on itself.