In the February 2017 issue of Scientific American
an article, Pop Goes the Universe
argues against the idea of cosmic inflation in the early Universe. The authors, Anna Ijjas, Paul J. Steinhardt and Abraham Loeb argue instead for a "bouncing cosmology." Cosmic Inflation Theory Faces Challenges
The latest astrophysical measurements, combined with theoretical problems, cast doubt on the long-cherished inflationary theory of the early cosmos and suggest we need new ideas
Now there has been a response by 33 physicists and a response to the response.
A Cosmic Controversy
In Pop Goes the Universe, by Anna Ijjas, Paul J. Steinhardt and Abraham Loeb, the authors (hereafter IS&L) make the case for a bouncing cosmology, as was proposed by Steinhardt and others in 2001. They close by making the extraordinary claim that inflationary cosmology cannot be evaluated using the scientific method and go on to assert that some scientists who accept inflation have proposed discarding one of [science’s] defining properties: empirical testability, thereby promoting the idea of some kind of nonempirical science. We have no idea what scientists they are referring to. We disagree with a number of statements in their article, but in this letter, we will focus on our categorical disagreement with these statements about the testability of inflation.
There is no disputing the fact that inflation has become the dominant paradigm in cosmology. Many scientists from around the world have been hard at work for years investigating models of cosmic inflation and comparing these predictions with empirical observations. According to the high-energy physics database INSPIRE, there are now more than 14,000 papers in the scientific literature, written by over 9,000 distinct scientists, that use the word inflation or inflationary in their titles or abstracts. By claiming that inflationary cosmology lies outside the scientific method, IS&L are dismissing the research of not only all the authors of this letter but also that of a substantial contingent of the scientific community. Moreover, as the work of several major, international collaborations has made clear, inflation is not only testable, but it has been subjected to a significant number of tests and so far has passed every one.
This sort of discussion in science is one of the best things about science. This is a form of peer review that all too often the public is unaware of.
What if Eleanor Roosevelt had wings? -- Monty Python
One important characteristic of a theory is that is has survived repeated attempts to falsify it. Contrary to your understanding, all available evidence confirms it. --Subbie
If evolution is shown to be false, it will be at the hands of things that are true, not made up. --percy
The reason that we have the scientific method is because common sense isn't reliable. -- Taq