Detection of B-mode polarization confirms inflation theory
Last November, astrophysicist Alan H. Guth — Victor F. Weisskopf professor of physics and a Margaret MacVicar fellow at the Massachusetts Institute of Technology — discussed the theory of inflation in his lecture “Inflationary Cosmology: Is Our Universe Part of a Multiverse” at Carnegie Mellon. The presence of such a world-renowned physicist on campus caused quite a flurry of excitement, but now Guth’s lecture has an added significance: Evidence for the theory of inflation, which Guth first proposed in 1980, was finally confirmed this past Monday.
When our universe was approximately 380,000 years old, the Cosmic Microwave Background (CMB) came into existence. In its earliest stages, long before the formation of stars and planets, the universe was a very hot and dense place, where protons and electrons moved around freely in plasma.
As the universe expanded and cooled, protons were able to combine with electrons to form hydrogen and photons began to decouple from the matter, leaving behind the CMB — a faint radiation echo of the Big Bang that permeates the entire universe.
However, according to physicsworld.com, the CMB showed that the universe is homogeneous, flat, and isotropic, which is contrary to the highly curved and heterogeneous structure suggested by the Big Bang Theory. It was this disagreement which prompted Guth to propose the theory of inflation.
Inflation is the idea that fractions of a second after the Big Bang — within 10-34 seconds — the universe underwent a period of exponential expansion in which it increased at a rate faster than the speed of light. According to PBS, the universe expanded by at least a factor of 1025 during this minuscule period of time. This rapid expansion accounts for the smooth and flat appearance of the CMB.
So how can an event that occurred 13.8 billion years ago be confirmed? According to CNN Tech, there are tiny ripples in the fabric of spacetime called quantum fluctuations that were blown up during inflation, launching gravitational waves that can be observed in the CMB today. As the waves pass through spacetime, they will squeeze the fabric in one direction and stretch it in another, creating two types of polarization known as E-modes and B-modes.
While E-modes have already been detected in the CMB, they can also be a result of other mechanisms. This past Monday, however, the Background Imaging of Cosmic Extragalactic Polarization telescope (BICEP2), which scans the sky from the south pole, finally detected B-mode polarization.
According to universetoday.com, other teams will continue to verify these results from their own measurements in the next year. The confirmation of the theory of inflation not only validates the origin of the structure of the universe, but also predicts the existence of a multiverse — an entire collection of multiple universes.