Spotted! The signature of our inflationary Universe?


Image: BICEP2 collaboration

It’s a good thing we got that Higgs Nobel prize out of the way last year, as we’ve got a big new contender lined up. After a few days of rumours, the team behind South Pole telescope BICEP2 today announced their detection of the signature of inflation in the polarization of the cosmic microwave background (CMB). In case the big words coming to you from the BBC, the Guardian, Nature, the New York Times, Peter Coles, Sean Carroll, roughly 500 twittering astronomers and Andrei Linde himself have not yet convinced you, let me add to those: if (if!) it stands, this is a Very Big Deal.

The distinctive wiggles found in the CMB polarization map are the imprints of the gravitational waves that accompanied inflation, the faster-than-light expansion the Universe underwent less than one-trillionth of a second after the Big Bang (13.8 billion years ago). This expansion explains why the Universe looks so smooth and uniform in all directions, despite its vastness.

If we leave aside the awesomeness of being able to detect any signals from anything that happened at this esoteric time, let alone offer a sensible interpretation, this is a major discovery for a number of reasons. It is very strong evidence that inflation actually happened as it was thought out by the early theoreticians who pioneered the theory. This in itself is a big missing piece of the puzzle of our Universe. In addition, the observed signal lends support to the notion that gravity was unified with the other fundamental forces in the hot early Universe. Finally, this is the first direct detection – or one the first, depending on how you define “direct” – of the highly elusive gravitational waves that astronomers have hunted for decades.

This stuff is too far from my own field for me to understand the details of the data or their interpretation, but the general consensus amongst social-media-connected astronomers is that the data look good and the analysis extremely rigorous. Teasing such a faint signal out of observational data is invariably a very tough task, with lots of systematics in the measurements to account for. Some scientists seem pretty skeptical, and that is a good thing. The data and accompanying papers will still need immense scrutiny and very thorough peer review before being officially accepted as Real and True. Whatever the outcome, this has clearly been a huge effort by the BICEP2 team, and they deserve a big congratulations for these results.

If you want to learn more about the physics of the very young Universe, I can highly recommend Alan Guth’s own book on his journey developing the theory of inflation, The Inflationary Universe, which is one of my all-time favourite popular science books. More generally on gravity and general relativity, fellow Oxfordian Pedro Ferreira just published a book entitled The Perfect Theory, which I’m enjoying at the moment.

A number of cosmologists have given their (more technical) opinions and interpretations online: Peter Coles at Sussex, Phil Bull in Oslo, and I’ll add a few more as I find them. 18/03: this from Renée Hlozek at Princeton,  more from Peter Coles,

The official papers and data are publicly available here.



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