On a clear night, the celestial vault resembles a motionless tapestry. But if you observe it through the eyes of an astrophysicist, you'll see that the universe is not only expanding but, thanks to gravity, forms something similar to the watersheds that shape the landscape. Like the intrepid explorers who sailed seas and oceans to map the Earth, Hélène Courtois has dedicated herself to drawing dynamic maps of the position and movement of galaxies and other agglomerations of stellar matter, in a ceaseless effort to describe space and its evolution. This book chronicles the collective effort that led to the discovery of Laniakea, the colossal supercluster 500 million light-years across and home to some 100,000 galaxies like our own. You'll need to hold on tight to imagine the movements of the universe, understand the challenges facing skywatchers today, and experience the blend of ingenuity and rigor required for science to advance steadily. Entertaining and exciting, Courtois's work is at the same time a personal account, with tours of today's leading telescopes in France, Australia, and Hawaii, and a description of one of the most exciting discoveries in contemporary astronomy. Traversing the seas of the cosmos in this way will give you a new appreciation for our home in the universe.