Monday, February 2, 2015

Dust in our eyes?

It appears that the latest Planck satellite data is conducive to the conclusion that the discovery of gravitational waves claimed by the BICEP2 collaboration last year, is not yet one to get starry eyed about. The latest data which measures the concentration of dust in the region where the BICEP2 measurements are carried out indicates that the quantum of dust is sufficiently large that it could be responsible for about half the B-wave polarisation observed in the BICEP2 signal. This has led to wide-spread disavowal of the BICEP2 results, and caused some dismay in circles that have been heartened by their support for inflationary scenarios. Those that went overboard in the opposite direction even said `Big Bang theory disproved' ! (The Times of India should really get some proper science reporters).

However, these reports of the demise of the theory are also highly premature (as in the case of Mark Twain!). The European Space Agency, which manages the Planck satellite,  puts it more soberly, “Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves”.

 This null result does not disprove the existence of gravitational waves, nor does it rule out inflation. It merely indicates that BICEP2 has not detected gravitational waves yet, with a high degree of certainty. The gravitational wave signal may still exist in the observed BICEP2 data, but may be obscured by the noise, so this new result can place an upper limit on the possible strength of the B-mode polarisation caused by gravitational waves. The search for gravitational waves still continues, and we look forward to more conclusively established results in the near future.

This blog post is by Neelima Gupte and Sumathi Rao.

BTW: Speaking of science reporting, this is a good place to draw attention to the  IIT Madras science magazine brought out completely by IITM students on some of the research done at IIT Madras, including research on inflationary scenarios carried out at the Physics Department. Do have a look.