The theory of cosmic inflation was proposed by MIT physicist Alan Guth in 1980, because simpler models of the Big Bang could not explain some features of the universe as it appears today, such as its uniformity.
Inflation proposes that there was an initial exponential expansion of the universe caused by a repulsive form of gravity — opposite the normal way of thinking about gravity as an attractive force.
As the universe continues to expand today, “what we see now is still a coasting expansion, originating from the Big Bang,” Guth said in an interview.
As Guth’s initial idea has been refined and developed by other scientists over the years, its predictions seemed to be borne out. But there was still no direct evidence for inflation and it was unclear whether the theory would ever have proof to bolster it. The energy needed to re-create the conditions of the early universe in a particle accelerator — 10 trillion times higher than what is produced at the Large Hadron Collider in Switzerland — were so high that it was unfeasible.
The Harvard-led team took a different approach. One prediction of the theory is that the rapid expansion would have left behind a fingerprint — a particular pattern of polarized light in the cosmic microwave background. This faint light all across the sky is the afterglow of the Big Bang, emitted 380,000 years after the explosion, and the telltale pattern was created when the light interacted with gravitational waves.
Using a telescope called BICEP2 at the South Pole, the team claims to have detected that swirly polarization pattern, called B-mode polarization. If confirmed by other experiments, it will be strong evidence of inflation and help guide scientists to which particular version of inflation is the correct one.
