The Multiverse Is Inevitable, and We’re Living in It

The phrase "Multiverse" has become overloaded. Max Tegmark thinks that there are at least four different kinds of "Multiverse", which he organizes into levels. This article corresponds to level 2: post-inflationary bubbles. The four levels are:

1. Space beyond the cosmic horizon. 2. Post-inflationary bubbles (this article). 3. Quantum multiverse, i.e. Many Worlds interpretation. 4. Platonic multiverses. i.e. Other mathematical structures that "are" universes.

It helps to know about the idea of different kinds of multiverse, and how they are not mutually exclusive, when reading articles like this which use the term Multiverse without disambiguating it.

See: http://space.mit.edu/home/tegmark/crazy.html