A multiverse is a group of infinite universes. In many cases, the term is used to define the hypothetical set of every single possible universe. Multiverses vary in size from 0.2ω2 ly to 5ω2 ly.
Types of Multiverses[]
Level I[]
A level I multiverse is similar to a universe but infinitely sized with infinite dimensions. Because it is infinite, a level I multiverse will contain anything that is possible under its physical laws, including infinite clones of any object or structure.
Level II[]
This type of multiverse is a collection of universes with different physical laws and fundamental constants. In the eternal inflation theory, which is a variant of the cosmic inflation theory, the multiverse or space as a whole is stretching and will continue doing so forever.
Level III[]
In a Level III multiverse, each possible state of the universe is a different basis vector in a Hilbert space, and the overall state of the universe is a vector in this Hilbert space; this state is called the universal wavefunction. Systems that are separated from their environment can be factored out of this vector, and when they interact with the environment ("are measured"), each possible state of the system leads to a different world. In a Level III multiverse, each possible action corresponds to a different universe, with some or many of the interpretation's proponents suggesting that these universes are as real as ours. Overall, Each universe is a multiverse itself because each universe contains endless branches of possibilities.
Level IV[]
In a level IV multiverse, all mathematical structures are real, and each mathematical structure corresponds to a different universe. This theory projects the fact that the ultimate type of a parallel universe opens up a full realm of possibilities. The differences in the universes are not just a result of location and cosmological properties but also of the existing laws of physics. These are mathematical universes. These very universes are abstract themselves and may be bigger than we realize.
Trivia[]
A civilization that controls all of the resources available in an entire Multiverse is called a Type 5.0 Civilization.