The Dark Forest is a 2008 science fiction novel by the Chinese writer Liu Cixin. It is the sequel to the Hugo Award-winning novel The Three-Body Problem in the trilogy titled "Remembrance of Earth's Past", but Chinese readers generally refer to the series by the title of the first novel.
Earth is under total surveillance by sophons, sub-atomic surveillance devices sent by Trisolarans, inhabitants of a planet of the stellar system Alpha Centauri. The sophons have also blocked all further research into particle physics, thus stopping any further human scientific development of fundamental principles, leaving only recombination and elaboration of existing technologies. Trisolaris orbits three stars and due to the nature of the three body problem will eventually fall into one of the stars; thus, Trisolaris seeks to colonize Earth for themselves. An invasion fleet has been launched which will arrive at Earth in 400 years.