August 8, 2013
Looking Back At The Big Bang Using Cosmic Microwave Background Radiation
April Flowers for redOrbit.com - Your Universe Online
The best way to solve a mystery, as any detective can tell you, is to revisit the scene where it began and look for clues. Scientists, searching for the mysteries of our universe, are trying to go back as far as they can to the Big Bang. Researchers at the Lawrence Berkeley National Laboratory (Berkeley Lab) conducted a new analysis of cosmic microwave background (CMB) radiation data to take the furthest look back yet. This look - 100 years to 300,000 years after the Big Bang - provides tantalizing new hints of clues as to what might have happened.
"We found that the standard picture of an early universe, in which radiation domination was followed by matter domination, holds to the level we can test it with the new data, but there are hints that radiation didn't give way to matter exactly as expected," says Eric Linder, a theoretical physicist with Berkeley Lab's Physics Division and member of the Supernova Cosmology Project. "There appears to be an excess dash of radiation that is not due to CMB photons."
The knowledge we have of the Big Bang and the early formation of the universe comes almost exclusively from measurements of the CMB - primordial photons set free when the universe cooled enough for particles of radiation and particles of matter to separate. The CMB's influence on the growth and development of the large-scale structure observed in the universe today are revealed by these measurements.
Linder worked with visiting scientists Alireza Hojjati, from the Institute for the Early Universe in South Korea, and Johan Samsing, of the DARK Cosmology Centre in Denmark, to analyze the latest satellite data from the European Space Agency's (ESA) Planck mission and NASA's Wilkinson Microwave Anisotropy Probe (WMAP). This data pushed CMB measurements to higher resolution, lower noise and more sky coverage than seen before. The findings of their analysis were published in a recent issue of Physical Review Letters.
"With the Planck and WMAP data we're really pushing back the frontier and looking further back in the history of the universe, to regions of high energy physics we previously could not access," Linder says. "While our analysis shows the CMB photon relic afterglow of the Big Bang being followed mainly by dark matter as expected, there was also a deviation from the standard that hints at relativistic particles beyond CMB light."
The prime suspects behind these relativistic particles, according to Linder, are "wild" versions of neutrinos. Neutrinos are the phantom-like subatomic particles that are the second most populous residents - after photons - of the current universe. Scientists call these particular neutrinos "wild" to differentiate the primordial particles from those expected within particle physics and being observed today. Scientists also suspect dark energy - the anti-gravitational force that accelerates our universe's expansion - though this suspicion is based upon what is known of dark energy today.
"Early dark energy is a class of explanations for the origin of cosmic acceleration that arises in some high energy physics models," Linder says. "While conventional dark energy, such as the cosmological constant, are diluted to one part in a billion of total energy density around the time of the CMB's last scattering, early dark energy theories can have 1-to-10 million times more energy density."
Early dark energy, says Linder, could have been the driving force that caused the present cosmic acceleration seven billion years later. Actually discovering dark energy would provide new insight into the origin of cosmic acceleration, as well as providing new evidence for string theory and other concepts in high energy physics.
"New experiments for measuring CMB polarization that are already underway, such as the POLARBEAR and SPTpol telescopes, will enable us to further explore primeval physics," Linder says.