Multiverse theory

The multiverse (or meta-universe) is the hypothetical set of possible universes, including the universe in which we live. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy, and the physical laws and constants that describe them.

The various universes within the multiverse are called "parallel universes", "other universes" or "alternative universes".

In Dublin in 1952, Erwin Schrödinger gave a lecture in which he jocularly warned his audience that what he was about to say might "seem lunatic". He said that, when his Nobel equations seemed to describe several different histories, these were "not alternatives, but all really happen simultaneously". This is the earliest known reference to the multiverse.

The American philosopher and psychologist William James used the term multiverse in 1895, but in a different context.

The structure of the multiverse, the nature of each universe within it, and the relationships among these universes differ from one multiverse hypothesis to another.

Multiple universes have been hypothesized in cosmology, physics, astronomy, religion, philosophy, transpersonal psychology, and literature, particularly in science fiction and fantasy. In these contexts, parallel universes are also called "alternate universes", "quantum universes", "interpenetrating dimensions", "parallel dimensions", "parallel worlds", "alternate realities", "alternate timelines", and "dimensional planes".

The physics community continues to debate the multiverse hypothesis. Prominent physicists disagree about whether the multiverse exists.

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