... the inflationary paradigm is so flexible that it is immune to experimental and observational tests. First, inflation is driven by a hypothetical … - Paul Steinhardt

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... the inflationary paradigm is so flexible that it is immune to experimental and observational tests. First, inflation is driven by a hypothetical , the inflaton, which has properties that can be adjusted to produce effectively any outcome. Second, inflation does not end with a universe with uniform properties, but almost inevitably leads to a multiverse with an infinite number of bubbles, in which the cosmic and physical properties vary from bubble to bubble. The part of the multiverse that we observe corresponds to a piece of just one such bubble. Scanning over over all possible bubbles in the multiverse, everything that can physically happen does happen an infinite number of times. No experiment can rule out a theory that allows for all possible outcomes. Hence, the paradigm of inflation is unfalsifiable.