Is the multiverse theory testable?
The idea that the universe stretches far beyond what we can see is not really a theory—it is a prediction made by certain theories of quantum mechanics and of gravity. Admittedly, it is a prediction that is hard to test. But all theories of physics force us to go beyond what we can directly see. For instance, our current best model for the origin of cosmic structure, the inflationary universe scenario, requires us to understand the conditions even before inflation.
