To understand the mysteries of our universe, scientists are trying to go back as far they can to the Big Bang. A new analysis of cosmic microwave background radiation data by researchers with the Lawrence Berkeley National Laboratory has taken the furthest look back through time yet — 100 years to 300,000 years after the Big Bang..
“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 [cosmic microwave background radiation] 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.”
“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.”
Linder says the prime suspects behind these relativistic particles are “wild” versions of neutrinos, the phantomlike subatomic particles that are the second most populous residents (after photons) of today’s universe. The term “wild” is used to distinguish these primordial neutrinos from those expected within particle physics and being observed today. Another suspect is dark energy, the anti-gravitational force that accelerates our universe’s expansion. Again, however, this would be from the dark energy we observe 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.”