Debunking the Big Bang...

[revelarts]

https://blogs.scientificamerican.com...lped-conceive/

Horgan: You were one of the originators of inflation theory. When and why did you start having doubts about it?

Steinhardt: From the very beginning, even as I was writing my first paper on inflation in 1982, I was concerned that the inflationary picture only works if you finely tune the constants that control the inflationary period. Andy Albrecht and I (and, independently, Andrei Linde) had just discovered the way of having an extended period of inflation end in a graceful exit to a universe filled with hot matter and radiation, the paradigm for all inflationary models since. But the exit came at a cost -- fine-tuning. The whole point of inflation was to get rid of fine-tuning – to explain features of the original big bang model that must be fine-tuned to match observations. The fact that we had to introduce one fine-tuning to remove another was worrisome. This problem has never been resolved.
But my concerns really grew when I discovered that, due to quantum fluctuation effects, inflation is generically eternal and (as others soon emphasized) this would lead to a multiverse. Inflation was introduced to produce a universe that looks smooth and flat everywhere and that has features everywhere that agree with what we observe. Instead, it turns out that, due to quantum effects, inflation produces a multitude of patches (universes) that span every physically conceivable outcome (flat and curved, smooth and not smooth, isotropic and not isotropic, scale-invariant spectra and not, etc.). Our observable universe would be just one possibility out of a continuous spectrum of outcomes. So, we have not explained any feature of the universe by introducing inflation after all. We have just shifted the problem of the original big bang model (how can we explain our simple universe when there is a nearly infinite variety of possibilities that could emerge from the big bang?) to the inflationary model (how can we explain our simple universe when there is a nearly infinite variety of possibilities could emerge in a multiverse?).
I have to admit that I did not take the multiverse problem seriously at first even though I had been involved in uncovering it. I thought someone would figure out a resolution once the problem was revealed. That was 1983. I was wrong. Unfortunately, what has happened since is that all attempts to resolve the multiverse problem have failed and, in the process, it has become clear that the problem is much stickier than originally imagined. In fact, at this point, some proponents of inflation have suggested that there can be no solution. We should cease bothering to look for one. Instead, we should simply take inflation and the multiverse as fact and accept the notion that the features of the observable universe are accidental: consequences of living in this particular region of the multiverse rather than another.
To me, the accidental universe idea is scientifically meaningless because it explains nothing and predicts nothing. Also, it misses the most salient fact we have learned about large-scale structure of the universe: its extraordinary simplicity when averaged over large scales. In order to explain the one simple universe we can see, the inflationary multiverse and accidental universe hypotheses posit an infinite variety of universes with arbitrary amounts of complexity that we cannot see. Variations on the accidental universe, such as those employing the anthropic principle, do nothing to help the situation.
Scientific ideas should be simple, explanatory, predictive. The inflationary multiverse as currently understood appears to have none of those properties.
These concerns and more, and the fact that we have made no progress in 30 years in addressing them, are what have made me skeptical about the inflationary picture....