The Meta-Universe, better known as the Multiverse, is the total of all possible universes. As it includes everything that exists, the entirety of space, time, matter, energy, information and the laws and constants that describe them, this is reality itself. Or could there be, as some philosophers have claimed, a "counter-reality" outside, or even within it?
The multiverse theory invokes infinite numbers of other universes, both in space and in time, as mechanisms for explaining the long-standing mystery of why the constants of nature appear to be fine-tuned for the emergence of life. If the deep laws of our universe had been ever so slightly different human beings wouldn't, and couldn't, exist. This exquisite fine-tuning could be explained by pointing to a multiverse where all universes exist. Obviously, the universe we are living in is a universe where life is possible.
Four levels of multiverses
According to cosmologist Max Tegmark there are four levels of multiverses allowing for progressively greater diversity. Level one is, for the most part, more space beyond the observable universe.
Cosmological inflation assumes that as soon as there was any space at all, it was infinite in size. Accordingly, an infinite universe will contain an infinite number of universe, all having the same physical laws and physical constants. In regard to configurations such as the distribution of matter, almost all will differ from our Universe. But because there are infinitely many, far beyond the cosmological horizon, there will eventually be a universe just like ours.
The level two multiverse has different regions of space that can exhibit different laws of physics (physical constants, dimensionality, particle content, etc.) corresponding to a landscape of different possibilities, like a bathtub filled with bubbles, each bubble being a single universe.
The level three multiverse is particular to the Many Worlds Interpretation of quantum mechanics: Everything that can happen in the particle realm actually does happen. Observers would only view their level one multiverse, but the process of decoherence—which describes the transition from the quantum realm to the classical realm—prevents them from seeing the level three parallel copies of themselves.
Tegmark argues that a level III multiverse does not contain more possibilities to form universes than a level I-II multiverse and that the only difference between level I and level III is where your doppelgängers reside. Similarly, all level II bubble universes with different physical constants can in effect be seen as "worlds" created by "splits" at the moment of spontaneous symmetry breaking in a level III multiverse. This implies that the multiverses of level I, II, and III are, in fact, the same thing.
Tegmark's fourth level is the all-encompassing version where mathematics produce physical existence. The mathematics of our universe is just one of an infinity of mathematical structures that should also exist physically as other universes with different fundamental equations of physics. This implies that any conceivable multiverse theory, including the idea of a Cyclic Multiverse for instance, can be described at level IV and that there cannot be, say, a level V.
In a way, level IV can be seen as Plato's ideal of a reality that emerges from numbers and mathematics. We can use human language, but this is merely a useful approximation for describing our subjective perceptions of the mathematical structures that make reality.
Who created the creator?
According to physicist Paul Davies it might not be possible to fully test the multiverse theory which would make it a "leap of faith" every bit as big as the leap to believing in a God-creator. And this idea of a God-creator poses a problem, as one question always remains: who created the creator? This quickly turns into some version of "turtles all the way down."
Maybe the question could be avoided by assuming a "reality on the other side of reality," without a beginning or an end, much like Schopenhauers concept of a "Will." An all permeating but unobservable force, responsible for creating all universes.
This idea is also reminiscent of what the Chinese call the Tao, the Hindus call Brahman and the early Gnostic Christians called Logos. But maybe it's just Father Time, or Chronos as the ancient Greeks called him.