Alternate universe

An alternate universe (also called a parallel universe, alternate reality or alternate quantum reality) is a universe which differs in some way from one's own universe. Some alternate universes are classified as alternate timelines, where the differences between universes can be attributed to an alternate outcome of some past event. Others, however, differ in more dramatic ways, such as differing laws of physics, that cannot be easily explained by diverging histories. All alternate universes taken together form the multiverse.