Here is another sidebar from my article which discusses an additional argument in favor of multiple universes. This argument comes from Inflationary theory, whose key ideas are illustrated by the graphic below. The theory of Inflation exists to explain mainly why distant regions of the universe could be at basically the same temperature, even though they are so distant that a light signal could not have traveled between them in the finite age of the observable universe. The temperature of causally disconnected regions is so strikingly similar that it would be as if two completely independent island civilizations just happened to develop exactly the same language, never having communicated in all of their history. As such, Inflationary theory asks how could two regions of space both "know", to be at the same temperature, if they could never have communicated this fact to one another through some signal in the time allotted? Inflationary theory claims that the two relevant regions were originally close together and in mutual communication, but in the first instant of the universe after the Big Bang, they underwent an exponential expansion of space (i.e. inflation) that actually went faster than light and separated them out of causal contact. It should be noted that, while no objects within space-time can be accelerated past the speed of light, General Relativity does not have a problem with space itself being created at a rate faster than light. This naturally leads to regions or "bubbles" that are separated so far from each other that they are completely out of causal contact with one another, where the light travel radius between them is larger than the light travel radius of each of them individually. Picture each point in space defining a finite sphere or bubble around it, then envision two such equally sized spheres with centers separated by a distance larger than their diameter. Many of these bubbles will overlap, but you can always find two points with corresponding bubbles that do not overlap. These regions are none other than the previously discussed multiple universes.