In several previous posts (see one here), I have argued that multiverse theories are not science, as they cannot be proven false, but rather science fiction, purely imaginative creations. Further proof of this is that the idea of the multiverse did not originally arise from science, but from science fiction. Some of my reading this summer has helped me complete the proofs for this assertion.
The most common form of the multiverse, the M-theory multiverse, appeared for the first time in science fiction literature in a short story by Clifford Simak, published in 1939, which the author later developed into a novel, Cosmic Engineers, published in 1950. In this novel, the protagonists must confront the invasion of our universe by malevolent intelligent beings from another universe, who want to destroy us. To defend themselves, Earthlings establish an alliance with a civilization made up of artificial intelligences created by long-gone extraterrestrial beings, who warn them of the threat from the other universe.