Physicist Sean Carroll gave a wonderful talk at the June 2008 American Astronomical Society meeting about his “speculative research” on what possibly could have existed before The Big Bang. (Here’s an article about Carroll’s talk.) But now Carroll and some colleagues have done a bit more than just speculate about what might have come before the beginning of our Universe. Carroll, along with Caltech professor Marc Kamionkowski and graduate student Adrienne Erickcek have created a mathematical model to explain an anomaly in the early universe, and it also may shed light on what existed before the Big Bang. “It’s no longer completely crazy to ask what happened before the Big Bang,” said Kamionkowski.
Inflation theory, first proposed in 1980, states that space expanded exponentially in the instant following the Big Bang. “Inflation starts the universe with a blank slate,” Erickcek describes. The problem with inflation, however, is that it predicts the universe began uniformly.
But measurements from Wilkinson Microwave Anisotropy Probe (WMAP) show that the fluctuations in the Cosmic Microwave Background (CMB) –the electromagnetic radiation that permeated the universe 400,000 years after the Big Bang — are about 10% stronger on one side of the sky than on the other.
“It’s a certified anomaly,” Kamionkowski remarks. “But since inflation seems to do so well with everything else, it seems premature to discard the theory.” Instead, the team worked with the theory in their math addressing the asymmetry, since one explanation for this “heavy-on-one-side universe” would be if these fluctuations represented a structure left over from something that produced our universe.
They started by testing whether the value of a single energy field thought to have driven inflation, called the inflaton, was different on one side of the universe than the other. It didn’t work–they found that if they changed the mean value of the inflaton, then the mean temperature and amplitude of energy variations in space also changed. So they explored a second energy field, called the curvaton, which had been previously proposed to give rise to the fluctuations observed in the CMB. They introduced a perturbation to the curvaton field that turns out to affect only how temperature varies from point to point through space, while preserving its average value.
The new model predicts more cold than hot spots in the CMB, Kamionkowski says. Erickcek adds that this prediction will be tested by the Planck satellite, an international mission led by the European Space Agency with significant contributions from NASA, scheduled to launch in April 2009.
For Erickcek, the team’s findings hold the key to understanding more about inflation. “Inflation is a description of how the universe expanded,” she adds. “Its predictions have been verified, but what drove it and how long did it last? This is a way to look at what happened during inflation, which has a lot of blanks waiting to be filled in.”
But the perturbation that the researchers introduced may also offer the first glimpse at what came before the Big Bang, because it could be an imprint inherited from the time before inflation. “All of that stuff is hidden by a veil, observationally,” Kamionkowski says. “If our model holds up, we may have a chance to see beyond this veil.”