The Black Cloud is work of speculative fiction written by acclaimed astronomer Fred Hoyle. This 1957 book details the arrival of an enormous interstellar cloud of gas that enters the solar system and threatens to destroy all life on Earth by blocking the Sun's radiation. In an act of desperation, a cadre of astronomers try to communicate with the cloud, which leads to surprising results.
Though the presence of a sentient cloud of gas may seem patently absurd, the basis of this story is grounded in hard science. The detection of the cloud is described using physics equations, all of which are included in the book. Hoyle was, after all, Director of the Institute of Astronomy at Cambridge, a Fellow of the Royal Society, and responsible for, among other things, the term Big Bang. In an ironic plot twist that would foreshadow Hoyle's stance on panspermia, the cloud expresses surprise that intelligent life is capable of forming on planets.