Science: A Problem with Cosmic Inflation Theory

The Story: 

A recent analysis of astronomical data indicates that the cosmic microwave background (CMB) doesn’t contain something that a reigning theory (cosmic inflation theory, an elaboration of Big Bang theory) postulates that it ‘should’ have. This is going to send a lot of physicists back to their blackboards.


The original form of the Big Bang theory, developed by Georges Lemaitre in 1927 working from the theories of Albert Einstein and Willem De Sitter, raises a problem: why is the universe as uniform as it is? For example, why do astronomers who look deeply into space from the earth’s northern hemisphere see more-or-less the same density of galaxies as astronomers who look just as deeply from the southern hemisphere?

Cosmic inflation theory, proposed in 1980 by Alan Guth, offers a way to reconcile observation with theory. It postulates an incredibly fast expansion in the early moments of the universe, so fast that the rest of the ride has been relatively sedate.

There is another observational problem, though. Given an inflationary start, the CMB radiation ought to include both B-mode and E-mode polarization. The B-mode polarization would have been caused by the gravitational waves of a universe engaged in such expansion. They would have been “locked in” by it, detectable still.

Yet the recent analysis of data, by a Dutch scientist, appearing in the Oct. 4, 2021 issue of the journal Physics, indicates that there is virtually no B-mode presence in CMB. It is all (or nearly all) E-mode. This has astrophysicists confused.

Strange New Worlds:

This does not mean that astrophysicists are about to abandon the Big Bang. There are many solid lines of reasoning and evidence that support it, including importantly the very existence of CMB. Nor does it mean that many are going to abandon inflation. Some might, and they might propose alternatives to Guith’s theory to explain uniformity. But many will take another tack and create variations of cosmic inflation.

As the author of the article in Physics puts it, “If … future measurements continue to find no gravitational waves, we will need to abandon some of the most popular models for inflation and consider further modifications. And while the inflationary paradigm cannot be falsified from these observations alone, a non-detection could contribute to a paradigm shift towards noninflationary models.”

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