© Levi Brown
In this view, not only is our planet one among many, but even our entire universe is insignificant on the cosmic scale of things. It is just one of countless universes, each doing its own thing.
The word "multiverse" has different meanings. Astronomers are able to see out to a distance of about 42 billion light-years, our cosmic visual horizon. We have no reason to suspect the universe stops there. Beyond it could be many - even infinitely many - domains much like the one we see. Each has a different initial distribution of matter, but the same laws of physics operate in all. Nearly all cosmologists today (including me) accept this type of multiverse, which Max Tegmark calls "level 1."
Yet some go further. They suggest completely different kinds of universes, with different physics, different histories, maybe different numbers of spatial dimensions. Most will be sterile, although some will be teeming with life. A chief proponent of this "level 2" multiverse is Alexander Vilenkin, who paints a dramatic picture of an infinite set of universes with an infinite number of galaxies, an infinite number of planets and an infinite number of people with your name who are reading this article.
One of the first personages to speak of a Multi-Verse was the Buddha. The Diamond Sutra, The Vajrachedikka Mahapranaparamita Sutra, the Buddha's crucial teaching on the nature of Reality.
Amazingly - the Buddha discusses sub-atomic particles, infinity, paralel realities, supra-beings....making the concept of the brane within the bulk almost approachable.