Later this year, NASA scientist Al Kogut and his team at the Goddard Space Flight Center in Greenbelt, Maryland, will fly a breakthrough balloon payload — the Primordial Inflation Polarization Explorer, or PIPER — to find evidence of this accelerated expansion, called cosmological inflation.
According to the theory, inflation would have generated gravitational waves, which are tiny perturbations in the fabric of space-time. These waves would have left an imprint in the polarization of the cosmic background radiation, the remnant light from the universe’s creation that bathes the sky in all directions.
Scientific results from two NASA observatories that studied the background radiation revealed tantalizing clues that inflation did, in fact, occur. They found miniscule temperature differences in the afterglow radiation that pointed to density differences that eventually gave rise to the stars and galaxies seen today. The observations also showed that the density differences were remarkably uniform in all directions and that the geometry of the universe was flat — physical characteristics attributable to inflation.
Although other theories also explain these dynamics, they do not explain the existence of primordial gravitational waves created when the universe inflated to astronomical dimensions. Despite repeated attempts, so far no one has discovered these waves or their telltale polarization signature — what cosmologists refer to as B-mode.