Our July 2014 cover story was the apparent discovery of gravitational waves from the instant of inflation when the Big Bang took shape. Just as the article was printed, a serious challenge to the discovery appeared: the researchers had underestimated the amount of interstellar dust that could be contaminating their data.
Here are more links regarding what may yet be the biggest cosmology discovery of the 21st century, and its dust-contamination problems, and how soon the finding might be confirmed or disproved.
- The original BICEP2 2014 Results Release page — with the preliminary discovery papers, a public FAQ, image gallery, videos of the March 17th announcement at Harvard Observatory, and websites at the institutions involved.
- Cosmology: Polar Star. Backstory on team leader John Kovac and the BICEP project, by Ron Cowen in Nature.
- Multiverse Controversy Heats Up over Gravitational Waves, in Scientific American. Among some cosmologists, the multiverse is disreputable and politically touchy. And further evidence for inflation pushes it more into the spotlight.
- Tabitha Powledge’s review of the immediate media coverage and scientific reaction, at her PLoS “On Science” blogsite.
- BICEP isn’t the only project in the race. Here are ten B-mode searches underway in Antarctica, the Andes, the upper atmosphere, and in space, with links to their websites. Which will be the first to confirm or refute BICEP? Some of the searches will be much wider, deeper, higher-resolution, and/or multi-wavelength.
- Added May 13: As the excitement died down, on May 9th the Kavli Institute held a roundtable discussion of where things stand and what comes next. Among the cosmologists in the discussion was skeptic Paul Steinhardt as devil's advocate. Transcript.
- Added May 14: A Nature review of the picture now, and especially the future microwave-background projects that are being discussed — and their iffy funding prospects: Cosmology: First Light, by Joanne Baker (May 14, 2014).
- Added May 29: Just dust?? Nature reports on two new papers that challenge the BICEP team's claim to have ruled out dust in the Milky Way as the cause of their polarization signal: “No evidence for or against gravitational waves,” subtitled "Two analyses suggest signal of Big Bang ripples announced in March was too weak to be significant," by Ron Cowen.
The two papers are:
– 1. Mortonson, M. M. & Seljak, U.; preprint at http://arxiv.org/abs/1405.5857
– 2. Flauger, R., Hill, J. C. & Spergel, D. N.; preprint at http://arxiv.org/abs/1405.7351
Also in Nature, the story of the supposedly misapplied dust correction: Gravitational wave discovery faces scrutiny (May 16).
- Added May 30: Tabitha Powledge rounds up the evolving controversy as of May 23rd at her PLoS "On Science" news blog: Inflationary Universe data in question.
- Added June 1: The dust-contamination situation. Science magazine has published the clearest account, as far as I've seen, of the possibility that much or all of the polarization signal may come from magnetically-aligned dust in the Milky Way filtering the cosmic microwaves. Unfortunately it's behind a $20 paywall, but you may be able to get free access through a library that subscribes. It's also in the print magazine, May 23rd issue, page 790.
- Added June 5: Our own super-clear explanation: Big Bang Inflation Evidence Inconclusive, by Camille Carlisle.
- Added June 21: The BICEP team's formal publication, with a description of their mistaken application of the preliminary Planck dust map, and why they still think most of their signal is cosmological: Detection of B-Mode Polarization at Degree Angular Scales by BICEP2 (June 19). With a link to a good review article by Larry Krauss. Here's a New York Times story on the paper's publication: Astronomers Hedge on Big Bang Detection Claim, by Dennis Overbye (June 19).
- Added June 24: Does the Higgs boson rule out the BICEP claim? Two theoretical physicists say that if the inflation-era fluctuations of spacetime were as strong as the BICEP team originally announced (that is, r = 1.6 or so), the Higgs boson might have ended up in a different state that would have caused the universe to immediately recollapse: Electroweak Vacuum Stability in Light of BICEP2 (June 24). The official article is behind a paywall, but the preprint is free. Here's a press release explaining things.
- Added Sept. 11: BICEP and Planck teams are collaborating and sharing data, and in her Backreaction blog, physicist Sabine Hossenfelder gets wind that Planck is going to announce something by the end of September about dust contamination... perhaps something inconclusive.
- Added Sept. 22–24: Planck's announcement: Yes, lots of dust. But not necessarily enough to rule out a cosmological component in BICEP's signal. Clearer results may come later this year from the ongoing Planck-BICEP collaborative analysis. See our article, Dust Makes Cosmic Inflation Signal Iffy. Also, an excellent New York Times article (by former Sky & Tel staffer Dennis Overbye): Criticism of Study Detecting Ripples From Big Bang Continues to Expand. Here is the Planck team's paper. When asked for comment, Princeton cosmologist David Spergel told Sky & Telescope, "The Planck data implies that polarized dust is the dominant signal in the BICEP2 field. There could be a weaker signal from gravitational waves, but I don't think that the current data is good enough to separate out this weaker signal and make a statistically significant detection. Discovery of gravitational waves will await more sensitive measurements — fortunately, there are many groups pushing towards higher sensitivities."