Distortion in Universe's Oldest Light Offers Peek into the Past

For the first time, scientists have detected twisting patterns in the polarization of the universe's oldest light, or cosmic microwave background (CMB) - an observation that could hold clues to the universe's early formation, according to researchers.  

At minus 270 degrees Celsius, or just 3 degrees above absolute zero, the light particles that comprise the CMB represent the ancient afterglow of the Big Bang. Light is polarized when its electromagnetic waves are oriented in a specific direction. In the case of the CMB, light is polarized mostly due to photons scattering off of electrons during the universe's early stages. 

The new study, published in the journal Physical Review Letters, outlines the first patterns known as "B modes" in the CMB. The reason this is so intriguing, the researchers explain, is because unlike the dominant polarization pattern known as E modes, scattering alone does not create B modes.

"The detection of a primordial B-mode polarization signal in the microwave background would amount to finding the first tremors of the Big Bang," said the study's lead author, Duncan Hanson, a postdoctoral scientist at McGill University in Canada. 

For years, scientists predicted that gravitational lensing, caused when a celestial object amplifies the light emitted by one behind it, could transform E modes into B modes - a hypothesis the study's authors say they have now proven.

In order to tease out the new light patterns, the researchers used a previously devised map of the distribution of mass in the universe to determine where gravitational lensing should be taking place. They then combined this data with measurements of E modes to create a blueprint of places where the patterns were most likely being twisted into B modes.

Because of what they represent, B modes can be used to map out the distribution of the universe's mass, which can then help determine properties such as the masses of neutrinos. For this reason, the researchers behind the new study are currently busy decoding yet another year's worth of data to refine their measurements of the patterns.

"The detection of B-mode polarization by South Pole Telescope is a major milestone, a technical achievement that indicates exciting physics to come," said John Carlstrom, an astronomy and astrophysics professor at the University of Chicago.