Parallel universes. Conceptual artwork of parallel universes that may have formed along with our universe, or that form part of a hypothetical set of possible universes. These theories are collectively referred to as multiverses. Multiverse theories include the inflationary bubble theories where inflationary periods in the early universe produce universes with different physical laws. Another theory is the many-worlds interpretation of quantum theory. Yet another theory is the ensemble theory where different mathematical equations and physical laws apply. Versions of the anthropic principle state that life exists in our universe only because conditions allow life to exist. In other universes, life may not be possible.