Cosmologists ready to rumble over new challenges to "Big Bang" Cosmic Inflation paradigm

[astro]

So three scientists wrote an article for Scientific American

Cosmic Inflation Theory Faces Challenges

where they said the current "“Big Bang” Inflation model of the origin of the universe was not as powerful, predictive or even coherent as it’s supporters claimed. And after slapping it around a while they ended by saying

NONEMPIRICAL SCIENCE?

Given the issues with inflation and the possibilities of bouncing cosmologies, one would expect a lively debate among scientists today focused on how to distinguish between these theories through observations. Still, there is a hitch: inflationary cosmology, as we currently understand it, cannot be evaluated using the scientific method. As we have discussed, the expected outcome of inflation can easily change if we vary the initial conditions, change the shape of the inflationary energy density curve, or simply note that it leads to eternal inflation and a multimess. Individually and collectively, these features make inflation so flexible that no experiment can ever disprove it.

Some scientists accept that inflation is untestable but refuse to abandon it. They have proposed that, instead, science must change by discarding one of its defining properties: empirical testability. This notion has triggered a roller coaster of discussions about the nature of science and its possible redefinition, promoting the idea of some kind of nonempirical science.

Well … that got the other Cosmologists doing the scientific equivalent of neck rolling and … well then it was on!

A Scientific American article about the theory of inflation prompted a reply from a group of 33 physicists, along with a response from the article’s authors

[Snowboarder_Bo]

That argument you quoted is bunch of horseshit.

It smacks of the Creationist argument that there must be God because if even one little thing was different, life as we know it could not have happened.

It’s a stupid argument on it’s face, but combined with the monumentally foolish assertion that inflation cosmology is, by nature, untestable elevates the argument to “vapid”.

ETA: Their rebuttal was weak, too.

[astro]

@Snowboarder_Bo

That argument you quoted is bunch of horseshit.

It smacks of the Creationist argument that there must be God because if even one little thing was different, life as we know it could not have happened.

It’s a stupid argument on it’s face, but combined with the monumentally foolish assertion that inflation cosmology is, by nature, untestable elevates the argument to “vapid”.

ETA: Their rebuttal was weak, too.

I think the general point of the article was that after 3 decades the various inflationary hypotheses that have been put forward do not seem to have gained appreciable traction in terms of being a solid predictive paradigm. I think they also have a point that the points in the letter from the 30 cosmologists defending inflationary theory as a work in progress does have more of it’s share of authoritative arm waving vs specific examples of the predictive power of the theory.

What about the statement that the “well-defined” models have already made successful predictions? This is not true for the reasons described above – you cannot say what any inflationary model predicts unless you can first resolve the problems of initial conditions and the multimess.

It should also be noted that the so-called well-defined examples are being set by the authors after the fact – that is, after the observations have been made. Was the flurry of inflationary models designed in the early 1990s by Linde and others to give an open universe “well-defined”? Or were those authors sloppy and indefinite? What about the many authors that thought they had inflationary models that predict large non-gaussianity? Large tilt? Or deviations from isotropy? Or bumps and wiggles in the microwave background power spectrum? - All features that the WMAP and Planck Satellite experiments have ruled out.

And how about all the textbook models that were thought to predict B-modes with amplitudes that should have been detected by the WMAP and Planck satellites? The same models celebrated by many of the respondents when they thought that cosmic B-modes had been discovered? Are we supposed to assume that all these other models were poorly-defined and only those that turned out to agree with current observations were well-defined? Or could this possibly be an exercise in 20-20 hindsight?