A Clear Sign from the Very Beginning of Time

How did our universe come into existence?  It seems we are now much closer to answering the cosmic conundrum.

On 17 March 2014, a team of researchers from the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization 2) collaboration presented the first direct observational evidence to support a theory that describes the birth of our universe: cosmic inflation.

Theoretical cosmologists had predicted, back in the 1980s, that the Big Bang was followed by a period of 'inflation' - an exponential expansion of the incredibly hot, dense and tiny mass that occurred in the first 10^-34 seconds after the Big Bang.

The BICEP telescope, situated at the South Pole, has captured data that represent images of gravitational waves (ripples in the space-time fabric of the universe). Inflation makes certain predictions, including presence of indelible markers left behind by gravitational waves in the oldest light in the sky. The BICEP collaboration believes this is exactly what their data show - the characteristic twist in the oldest light that only gravitational waves moving through the universe in its inflationary phase could have produced.

For cosmologists, the result, if verified, is nothing short of spectacular. Ravi Sheth, research scientist at ICTP who works on cosmology, galaxy formation and large-scale structure of the universe, says that the BICEP data pushes our understanding of the universe to as close to the beginning as possible. "Light reaching us from far away shows us the universe when it was younger," he says. "If the light from the CMB (cosmic microwave background, presented in the Planck data published in 2013) can be likened to the first picture of a new-born baby, then the BICEP pictures should be likened to ultrasound images of the baby in the womb, taken almost at the moment of conception. We expect pictures like these to bring us a newer and richer understanding of that magic moment, just as the technology of ultrasound revolutionized our view of life itself."

The announcement came as a positive surprise for Paolo Creminelli, also a research scientist at ICTP working on early cosmology (including inflation and non-gaussianity). "To me this result, if correct, is as big, or perhaps bigger, than the Higgs boson announcement," he says. "It was not obvious that we would have observational evidence for gravitational waves in our lifetime. With the BICEP data, we not only have that evidence but their result shows that the amplitude of  gravitational waves is as large as we hoped it would be."

Creminelli says that the finding is as much a triumph for theorists as it is for the BICEP team. "In 2002, ICTP awarded the Dirac Medal to Alan Guth, Andrei Linde and Paul Steinhardt for developing this theory of inflation, and now we have the observational evidence for it," he says. "However, without this [BICEP] measurement we would have lived with the idea that the theory of inflation is very likely the correct one, but we couldn't be sure. Now, we have evidence that can be verified!"

Both Sheth and Creminelli say that at first glance the results look well-analyzed and robust, but that verification by other groups is important, and likely to happen before the end of this year. "This result shows that inflation is indeed the way to go for studying our universe," says Sheth. Creminelli agrees and adds that in view of the BICEP results researchers may abandon theories presented as alternatives to inflation.

"We can now know the energy scales, how hot and dense the universe was, in the inflationary period," says Sheth. This, he says, may define the limits of future lines of research in early cosmology. Simply put, cosmologists may now have a guide for answers to questions about life and the universe.

The press release and technical details related to the BICEP data are available on the Harvard-Smithsonian Center for Astrophysics webpage.