Sean Carroll in Preposterous Universe:
Major announcement coming! That much is clear, from this press release: on Monday at noon Eastern time, astronomers will “announce a major discovery.” No evidence from that page what the discovery actually is. But if you’re friends with a lot of cosmologists on Facebook/Twitter (or if you just read the Guardian), you’ve heard the rumor: the BICEP2experiment has purportedly detected signs of gravitational waves in the polarization of the cosmic microwave background radiation. If it’s true (and the result holds up), it will be an enormously important clue about what happened at the very earliest moments of the Big Bang. Normally I wouldn’t be spreading rumors, but once it’s in the newspapers, I figure why not? And in the meantime we can think about what such a discovery would mean, regardless of what the announcement actually turns out to be (and whether the result holds up). See also Richard Easther, Résonaances, Sesh Nadathur, Philip Gibbs, Shaun Hotchkiss, and Peter Coles. At a slightly more technical level, Daniel Baumann has a slide-show review.
Punchline: other than finding life on other planets or directly detecting dark matter, I can’t think of any other plausible near-term astrophysical discovery more important than this one for improving our understanding of the universe. It would be the biggest thing since dark energy. (And I might owe Max Tegmark $100 — at least, if Planck confirms the result. I will joyfully pay up.) Note that the big news here isn’t that gravitational waves exist — of course they do. The big news is that we have experimental evidence of something that was happening right when our universe was being born.
More here.