Pausing to rest for a moment at New Scientist:
You might think that the universe started with a big bang. Ten years ago, that is what I thought too. But then I came to realise that the issue is far from settled. Pursuing this question prompted me to change the tack of my career and become a cosmologist, even though I had just completed a PhD in the philosophy of quantum physics. What I have discovered since then supports a radically new response to the question that irked Augustine – what came before the beginning? The answer, thrillingly, may be that there never was a big bang, but instead a universe with no beginning or end, repeatedly bouncing from an epoch of contraction to expansion, and back again.Anna Ijjas, “What if there was no big bang and we live in an ever-cycling universe?” at New Scientist (paywall)
The war on the Big Bang as an actual beginning can never stop and never will. The main question is whether the war on evidence will settle the issue by allowing whatever view would prevail most “thrillingly” to stand in for science.
Evidence isn’t really at issue; many people today need a universe other than the one we live in and they will theorize their way to it, if only in their own imaginations. But “science” will cooperate if science knows what is good for it.
Experimental physicist Rob Sheldon, our physics color commentator, writes to say,
Anna Ijjas was a post-doc for Paul Steinhardt, and in the past 5 years they have written a number of papers very critical of “inflation”. It’s ironic, because Steinhardt was one of the 3 founders of inflation theory. Just last week we had a mention of his 2017 SciAm blog describing the death of inflation. The problem is that no one knows how to solve all the designed features of the universe without inflation. Evidently Steinhardt and Ijjas came up with a solution (which turns out to be 40 years old), the “Big Bounce”. They argue that all the smoothness of the universe produced by inflation, can also be produced by repeated expansion-contraction-bouncing expansion-contraction-bouncing expansion…
Here’s their 2019 cyclic universe paper:
Abstract: Combining intervals of ekpyrotic (ultra-slow) contraction with a (non-singular) classical bounce naturally leads to a novel cyclic theory of the universe in which the Hubble parameter, energy density and temperature oscillate periodically, but the scale factor grows by an exponential factor from one cycle to the next. The resulting cosmology not only resolves the homogeneity, isotropy, flatness and monopole problems and generates a nearly scale invariant spectrum of density perturbations, but it also addresses a number of age-old cosmological issues that big bang inflationary cosmology does not. There may also be wider-ranging implications for fundamental physics, black holes and quantum measurement. (open access)More.
Sheldon also offers some thoughts on the paper:
1) What is really recycling is not the universe, but this theory.
2) None of the previous objections to a “Bouncing Universe” are addressed, rather it is now seen (by Ijjas and Steinhardt) as less objectionable than the justifications for inflation, multiverse, etc. In other words, its new-found attraction is simply by comparison to all the other badly aging theories out there.
See also: The Big Bang: Put simply,the facts are wrong.
What becomes of science when the evidence does not matter?
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