Primordial Gravitational Waves

On March 17, 2014, it was officially announced that signs of gravitational waves, or ripples in the fabric of space-time, had been discovered in the data collected from the Cosmic Microwave Background radiation as an imprint left by our Universe approximately 380,000 years after the Big Bang. This is considered to be a plausible advance towards the indirect detection of Albert Einstein's gravity waves, originally predicted to exist in his general theory of relativity of 1916. The BICEP2 team, located at the South Pole, has identified a swirling pattern throughout the light of the CMB known as B-mode polarization, believed to be the result of inflationary gravitational waves. "We’ve found the smoking gun evidence for inflation and we’ve also produced the first image of gravitational waves across the sky" (source).


A polarized light pattern in the CMB caused by early gravitational waves (Image: BICEP2).

Finding gravitational waves embedded in the CMB would reasonably support the theory of inflation, originally proposed by physicist Alan Guth, which describes an initial period of highly accelerated expansion for the Universe that smoothed out irregularities in space-time and made the cosmos look almost the same in every direction. The CMB is the oldest electromagnetic radiation we can see from after that period, thought to have emerged at a time when matter was only beginning to form structures out of a hot and dense plasma. This early light now fills every region of space and reaches us in the form of microwaves with an average temperature of 2.725 K, while it is considered to be the Big Bang's afterglow. Along with providing important information about the universe's early development, including tentative effects of ancient gravity waves, the CMB also reveals key insights into features of today's universe such as apparent composition and overall uniformity.

Special Note: Although there is new evidence suggesting that interstellar dust levels may have modified the interpretation of these results by being higher than previously determined, the theoretical basis for gravitational waves is still very strong and this latest outcome does not completely rule out their existence. 8*]