Inflation’s two main criticisms, that it can predict anything and that the “measure problem” remains unsolved, can’t erase its successes.
In the 1920s, we first measured the distances to objects beyond our own Milky Way, and swiftly discovered that the Universe was expanding: consistent with how Einstein’s General Relativity tells us the Universe would evolve. If the Universe was expanding today, that implies it was smaller — and hotter, and denser, and more uniform — in the past, leading to the idea of the hot Big Bang. Starting in the 1960s, the Big Bang’s greatest predictions were confirmed, leading to widespread acceptance of the theory. However, a few unexplained puzzles remained, leading scientists to question whether the most extreme predictions of the Big Bang, including arbitrarily high temperatures and an origin from a singularity, were actually correct.
In the early 1980s, a revolutionary new theory was proposed, intending to solve those puzzles: cosmic inflation. Theorists rushed to work on inflation, figuring out which “flavors” of inflation successfully led to a hot Big Bang and then making a series of predictions that could be compared and tested against the differing predictions of the Big Bang without…
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