UPDATE: My big article about the BICEP2 results is up at Ars Technica, so you should probably read that instead of this post.
Rumors have percolated throughout the cosmology community, surrounding today’s press conference at the Harvard-Smithsonian Center for Astrophysics (CfA). So far, the rumors appear to be substantiated: researchers with the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) observatory at the South Pole are announcing a potentially very exciting measurement, albeit one that involves some complicated concepts.
In brief, BICEP2 is designed to measure the polarization of the Cosmic Microwave Background, light left over from when the Universe became transparent, about 380,000 years after the Big Bang. However, that light conveys information from an even earlier epoch, and could show signs of inflation: the hypothetical rapid expansion of the cosmos during its first moments. If it happened — and we aren’t sure it did, though we have some strong hints — inflation would have left gravitational waves, which polarized light in a characteristic fashion, known as B-mode polarization. That’s why today’s announcement is very intriguing: if BICEP2 data contains the right kind of polarized light, it’s a sign of those gravitational waves, which in turn could be a clue about inflation. (For a lot more information, see Sean Carroll’s blog post.)
Now I’m using all the weasel words for a reason! Measuring B-mode polarization is hard, and plagued with a number of systematic difficulties. Trust me when I say that cosmologists will be scrutinizing the BICEP2 paper when it’s released in about two hours, probing all its weaknesses, and trying to determine if its claims are as strong as hinted. Obviously the BICEP2 researchers believe it’s significant, or else they wouldn’t be holding a big press conference and building up this much excitement, but (to quote Carl Sagan), extraordinary claims require extraordinary evidence. That’s not a bad thing — it’s how science works, at least ideally.
Given that I’m already seeing headlines proclaiming that this means we’ve detected gravitational waves (no, and we know they exist already) or that Einstein is vindicated (Einstein died long before inflation was predicted), I realize I’m already “behind” on this story. However, I would much rather wait until I can read the paper and see what the scientists say before I write my article. I suspect that the story will be more complicated than it appears on the surface, but again: that’s the way of science. When my actual article appears later today, I’ll try to to explain what’s going on to the best of our knowledge in a clear way.
In the meantime, if you want to watch the press conference, it begins at 11:55 AM, US Eastern Time. You can watch at this link.