A theory that attempts to account for the fine tuning of the universe for life may be “deeply flawed,” we learn in Paul J. Steinhardt’s “The Inflation Debate.” Steinhardt is one of the theory’s creators, nevertheless asks, “Abstract: Is the theory at the heart of modern cosmology deeply flawed?
Cosmic inflation is so widely accepted that it is often taken as established fact. The idea is that the geometry and uniformity of the cosmos were established during an intense early growth spurt.
But some of the theory’s creators, including the author, are having second thoughts. As the original theory has developed, cracks have appeared in its logical foundations.
Highly improbable conditions are required to start inflation. Worse, inflation goes on eternally, producing infinitely many outcomes, so the theory makes no firm observational predictions.
Scientists debate among (and within) themselves whether these troubles are teething pains or signs of a deeper rot. Various proposals are circulating for ways to fix inflation or replace it.
– Scientific American (April 2011), 304, 36-43 | doi:10.1038/scientificamerican0411-36 (Paywall)
Rob Sheldon notes,
Inflation adds a whole bunch of really unlikely metaphysical assumptions — a new force field that has a never-before-observed particle called the “inflaton”, an expansion faster than the speed of light, an interaction with gravity waves which are themselves only inferred– just so that it can explain the unlikely contingency of a finely-tuned big bang.
But instead of these extra assumptions becoming more-and-more supported, the trend went the opposite direction, with more-and-more fine-tuning of the inflation assumptions until they look as fine-tuned as Big Bang theories. At some point, we have “begged the question”. Frankly, the moment we add an additional free variable, I think we have already begged the question. In a Bayesean comparison of theories, extra variables reduce the information content of the theory, (by the so-called Ockham factor), so these inflation theories are less, not more, explanatory than the theory they are supposed to replace.
On the other hand, no one expects the first formulation of a theory to be the best, or the most concise, or even the most informative, so we should cut some slack for novel theories. But after 20 years of work, if we haven’t made progress, but have instead retreated, it is time to cut bait.