Recently, there has been substantial reporting in the media about the possible confirmation of inflation theory, not the rising prices of commodities (already well established), but rather the dramatic expansion of the universe that occurred shortly after the Big Bang nearly 14 billion years ago.
Last month, researchers representing 11 academic institutions and government agencies in the United States, Canada, and the United Kingdom presented results from the nearly three-year-long Background Imaging of Cosmic Extragalactic Polarization 2, or BICEP2, experiment, which appear to be the first direct evidence of cosmic inflation. If confirmed, this finding would arguably be the most significant discovery in cosmology since the detection of the cosmic microwave background in 1965 by Arno Penzias and Robert Wilson.
The BICEP2 observations were obtained using a 26 centimeter aperture, super-cooled telescope located at the Amundsen-Scott South Pole Station. The data reveal a polarization mode (B-mode polarization) in the cosmic microwave background, the pervasive thermal radiation leftover from the Big Bang, that was imprinted by gravity waves produced by inflation.
Inflation is believed to have occurred when the universe was just ~10-35 seconds old and describes an incredibly brief period when the universe exponentially expanded from perhaps the size of an atom to the scale of the solar system. The ensuing faster-than-light expansion did not violate Einstein’s special theory of relativity given that it was space-time itself that was distending.
Inflation was the extraordinary idea of theoretical physicist and cosmologist Alan Guth, a professor at the Massachusetts Institute of Technology. Guth proposed inflation to address several critical problems with the Big Bang cosmology, foremost among them the so-called flatness problem and the intriguing horizon problem. The flatness problem describes the density of matter and energy in the universe and how it is very close to the critical value necessary to have a flat universe, i.e. neither expanding indefinitely nor doomed to collapse.
Why, though, after nearly 14 billion years of expansion, was the density of the universe so close to this critical value? Inflation answers this by removing any significant curvature during the rapid growth of the universe. Visualize yourself on the surface of a balloon that is expanding. Once fully inflated, the curvature of its surface is smoothed out, appearing flat to the local observer.
The horizon problem can be best described by a simple question: how is it that different regions of the universe have exactly the same physical properties (temperature, density, etc.) when they have not been in contact with one another since the Big Bang? Simply stated, the universe is extremely isotropic to include the thermal temperature of the cosmic microwave background radiation. Inflation addresses the horizon problem by postulating that inhomogeneities were smoothed out prior to the onset of inflation. Once inflation began, isotropy was locked in and regions of the universe were effectively decoupled from each other by the faster-than-light expansion.
The confirmation of inflation theory by the BICEP2 collaboration is an extraordinary scientific achievement and beautifully demonstrates the merger between theory and observation. The BICEP2 experiment already has a successor in line, BICEP3, which will be installed at the Amundsen-Scott South Pole Station during the summer (winter in the northern hemisphere) of 2014-2015.
This new instrument will have 2,560 bolometer detectors – five times the number installed on the original BICEP2 telescope and will begin science operations in 2015. BICEP3 will continue observing the cosmic microwave background in search of answers to some of the most fundamental questions about the early universe.