The Three-Body Problem is a science fiction novel written by the Chinese writer Liu Cixin. It is the first novel of the Remembrance of Earth's Past trilogy, but the whole series is often referred to as Three-Body. The trilogy's second and third novels are The Dark Forest and Death's End, respectively. The series portrays a fictional past, present and future where, in the first book, Earth encounters an alien civilization in a nearby star system that consists of three sun-like stars orbiting each other in an unstable system. The title refers to the three-body problem in orbital mechanics.