When you train a telescope on outer space, you can see luminous galaxies, nebulae, stars, and planets. But if you add all that together, it constitutes only 15 percent of the matter in the universe. Despite decades of research, the nature of the remaining 85 percent is unknown. We call it dark matter. Physicists have devised huge, sensitive instruments to search for dark matter, which may be unlike anything else in the cosmos-some unknown elementary particle. Yet so far dark matter has escaped every experiment. It is so elusive that some scientists are beginning to suspect there might be something wrong with our theories about gravity or with the current paradigms of cosmology. Govert Schilling interviews believers and heretics and paints a colorful picture of the history and current status of dark matter research. The Elephant in the Universe is a vivid tale of scientists puzzling their way toward the true nature of the universe.