Earth is a part of a Solar system; Solar system a part of a Milky Way Galaxy; our galaxy is just one of the galaxies in a universe; our universe is just a single system of a multiverse.
The word “multiverse” was first used in 1895 but in different context, by an American philosopher and psychologist named William James.
The various universes within the multiverse are also called parallel universes, other universes, quantum universes, alternative universes, parallel dimensions, interpenetrating dimensions, parallel worlds, alternate timelines, alternate realities, and dimensional planes.
Multiple universes have been hypothesized in cosmology, physics, astronomy, religion, philosophy, transpersonal psychology, and literature, particularly in science fiction and fantasy. And even Marvel and DC comic books also made mentioned of multiverse, where different superheroes and other cosmic super-beings existed at different timelines and realities.
In 2007, Nobel laureate Steven Weinberg suggested that if the multiverse existed, “the hope of finding a rational explanation for the precise values of quark masses and other constants of the standard model that we observe in our Big Bang is doomed, for their values would be an accident of the particular part of the multiverse in which we live”.
So imagine how very vast the space out there? And would you think there would be any life source existing from a myriad of planets out there? Come to think of it.