One of the recent fads in scientific circles is the idea of multiple universes, or what’s commonly referred to as the multiverse. One of the several problems with this hypothesis is in finding a way to experimentally test such a hypothesis (predictions that are experimentally testable are what distinguishes a scientific theory from speculation, hypothesis and POT or plain-old-theory). There are several models of what a multiverse might look like. One is the soap bubble model, which I liken to envisioning a jar of marbles, each marble representing a different universe so that they nestle together surrounded by their neighbors. This particular model predicts that evidence might be found at the outermost edge of our universe of collisions with other adjacent soap bubble universes. A team of researchers led by physicist Stephen Feeney claim to have found such evidence in late 2010 in the form of large concentric circular structures in the cosmic background radiation (CMB), which according to them is evidence of collisions with neighboring universes. A mathematical algorithm was applied to various observable structures to find those that would be consistent with the proposed model. Of course, the sensationalist press at the time trumpeted this report as evidence proving the existence of multiple universes.
Now here comes The Rest of the Story. The scientists themselves called it a preliminary finding needing further study, and that it was relatively easy to find many kinds of statistically significant in a dataset as huge as the CMB. Subsequent researchers have opined that the statistical significance of these findings are too small by which to draw any conclusions other than the CNB contains many different kinds of structures within it, none which would be necessarily attributable to a collision between adjacent universes as a likely or preferable answer.
Then there are other logical problems that are often simply ignored. Since our universe is still expanding, one would presume that the adjacent ones are as well. They should then all be pushing up against each other so that rather than a couple of possible collision bruises, we’d have huge indentations around the entire perimeter of our space, crushing it in with increasing pressure. And speaking of space, what kind of ‘space’ do these universes occupy, and what kind separates them? As far as I know, even multiverse proponents have no sensible clue of this. Additionally, it still tells us nothing about how our own universe came into being, but instead adds a collage of other universes requiring their own explanations as to their origins. In truth, it is difficult to foresee any kind of testing experiment that might elevate the concept of a multiverse beyond the philosophical speculation it has always remained.