writes: Cosmic inflation is alternately talked about by serious scientists as either the definitive beginning to our Universe, the thing that happened before and set up the Big Bang with absolute certainty, or a speculative fiction that can never be falsified, leading to nothing but untestable predictions and things that only mattered after-the-fact of their discovery. But inflation has five unique predictions that it made intrinsic to all (reasonable) models back in the 1980s, before any of them were known:
- A Flat Universe,
- A Universe with fluctuations on scales larger than light could’ve traveled across.
- A Universe whose fluctuations were adiabatic, or of equal entropy everywhere.
- A Universe where the spectrum of fluctuations were just slightly less than having a scale invariant (n_s
- And finally, a Universe with a particular spectrum of gravitational wave fluctuations.
Four of the five have been confirmed, and that's why we're way more confident in it than most people realize!