This is a book about universes, a story that revolves around a single unusual and unappreciated fact: that Einstein´s famous theory of relativity describes universes -- entire universes. Not many solutions of Einstein´s tantalizing universe equations have ever been found, but those that have are all very remarkable. Some of them describe universes that expand in size, while others contract, some rotate like a top and others are chaotic. Some are perfectly smooth, while others are lumpy, or shaken in different directions by tides of energy; some oscillate forever, some become lifeless and cold, while others head towards a runaway future of ever-increasing expansion. Some permit time travel into the past, and others allow infinitely many things to happen in a finite amount of time. Only a few allow life to evolve within them; the rest remain unknowable to conscious minds. Some end with a bang, some with a whimper. Some don´t end at all.
Our story will encounter universes where the laws of physics can change from time to time and from one region to another, universes that have extra hidden dimensions of space and time, universes that are eternal, universes that live inside black holes, universes that end without warning, colliding universes, inflationary universes, and universes that come into being from something else -- or from nothing at all.