Cosmologists say they've accomplished the most precise and sensitive measurements yet of the polarization in the cosmic microwave background, the universe's oldest light.

The accomplishment marks an initial success for a project known as POLARBEAR, collaboration among some 70 scientists who are using a telescope in Chile's Atacama desert built to capture the universe's most ancient illumination.

POLARBEAR is designed to measure the oldest leftover radiation from the Big Bang, which has since cooled and stretched as the universe has expanded until it exists only at microwave wavelengths, researchers said.

Called the cosmic microwave background, it yields insights into the universe's large-scale structure and its cosmic history, the researchers say.

"It's a really important milestone," Kam Arnold, corresponding author of the report in the Astrophysical Journal, says of the POLARBEAR results. "We're in a new regime of more powerful, precision cosmology."

The researchers say they've found distinctive twists in the background radiation's polarization patterns, evidence of its having been bent and warped by structures in the universe including dark matter, neutrinos and dark energy.

The POLARBEAR team is measuring the polarization of light that dates from an era 380,000 years after the Big Bang, "when the early universe was a high-energy laboratory, a lot hotter and denser than now, with an energy density a trillion times higher than what they are producing at the CERN collider," says principle investigator Adrian Lee, a professor of physics at the University of California, Berkeley.

Following the Big Bang 13.8 billion years ago, the universe's temperature and density were so high light bounced endlessly from one particle to another, tearing apart any atoms that formed.

Only after 380,000 years was it sufficiently cool to allow electrons and protons to form stable hydrogen atoms that weren't immediately torn apart.

At that moment, all the universe's light particles -- photons -- were set free and the universe illuminated.

"The photons go from bouncing around like balls in a pinball machine to flying straight and basically allowing us to take a picture of the universe from only 380,000 years after the Big Bang," Lee says. "The universe was a lot simpler then: mainly hydrogen plasma and dark matter."

Those photons, today cooled to just to a mere 3 degrees Kelvin above absolute zero, still hold information that can yield clues to their last interaction with matter, the researchers say.

"Think of it like this: the photons are bouncing off the electrons, and there is basically a last kiss, they touch the last electron and then they go for 14 billion years until they get to telescopes on the ground," Lee says.

The light of these primordial photons allows scientists to probe large-scale gravitational structures in the universe such as clusters of galaxies arising from what were at first just tiny fluctuations in the density of the universe.

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