Is the Evidence for Inflation and Gravity Waves Just Dust?

One of the strengths of science and the scientific method is that it is self-correcting. As new evidence is found, old ideas are tested against that evidence. Should they fail, they are either modified or discarded and new ideas take their place. In such ways we improve our knowledge and better understand our Universe.

Back in March, I wrote about new evidence for cosmic inflationand gravity waves from the Backgroun Imaging of Cosmic Extragalactic Polarization (BICEP2) project. BICEP2 analyzed the cosmic microwave background radiation looking for a specific kind of polarization called B-mode polarization. At the time, the data from this project was strong and looked to be supporting the inflationary model of universe expansion, moments after the Big Bang.

Well, wouldn’t you know it, but it appears that this evidence wasn’t quite as good as hoped and, perhaps, such announcements were a bit premature. Several articles came across my news feed in the last few days discussing the BICEP2 data and the claims made by the team based upon that data.

The article “Ripples from dawn of creation vanish in a puff of dust,” in New Scientist by Jacob Aron, does a good job of covering the details. The light polarization which was used by the BICEP2 team could have been caused by inflation and gravity waves, but cosmic dust can also polarize light in the same way.Aron writes:

But other cosmic objects, like the dust that litters the Milky Way, can also polarise light, masking any patterns created by inflation. Initially the BICEP2 team claimed to have eliminated this possibility by pointing their telescope at one of the cleanest regions of the night's sky, accessible only from the South Pole.

The BICEP2 team did attempt to control for the effects of the dust, however, Jo Dunkley of the University of Oxford notes, "The BICEP analysis gave a degree of confidence that I think people agree was based on an over-optimistic estimate of what the dust could have been, and not based on data."

Dr. Dunkley is part of a team working with the data from the European Space Agency’s Planck spacecraft, which collected polarization data over the entire sky from 2009 to 2012. Aron continues, "In a paper published this morning the [Planck] team say it is very likely that BICEP2's signal was just down to dust."

Happily, the Planck and BICEP2 teams will be sharing data and collaborating on re-analyzing the combined data to see what can be learned. This is science in action, folks. Not always pretty or simple, but it’s still the best tool we have for learning about our Universe.

Be well.