A team of scientists may have detected a twist in light from the early universe that could help explain how the universe began. Such a finding has been compared in significance to the detection of the Higgs boson at the LHC in 2012.
What they detected is known as primordial B-mode polarization and is important for at least two reasons. It would be the first detection of gravitational waves, which are predicted to exist under Einstein’s theory of relativity but have never before been seen. But the thing that has scientists really excited is that it could provide the first direct evidence for a theorized event called inflation that caused the universe to exponentially grow just a fraction of a fraction of a second after it was born.
“Detecting this signal is one of the most important goals in cosmology today,” astronomer John Kovac of Harvard, who led the team announcing the discovery today, in a press release.
Though the team’s work will still need to be confirmed by other experiments, it is already generating a huge amount of interest. It would give physicists a look at the hot and violent early universe, when temperatures were 13 orders of magnitude greater than what can be achieved at the LHC. And it could help solve some lingering problems with our models of the Big Bang and the origins of the universe.
“This is literally a window back to almost the beginning of time itself,” said physicist Lawrence Krauss of Arizona State University, who was not involved with the work but who has studied inflation.
Now you might be asking yourself how primordial B-modes could be so important if you’ve never heard of them. Though not well known outside cosmologists’ meetings, primordial B-modes have been called the "first tremors of the Big Bang."
The early universe was extremely hot and dense. But about 380,000 years after the Big Bang, it had cooled enough that light waves could travel without immediately crashing into one particle or another. These photons have been traveling ever since, appearing in our telescopes as a faint radio signal called the Cosmic Microwave Background (CMB). B-modes are sort of like a ripple that has been imprinted on these CMB photons.
Light, being a wave, oscillates in a particular direction, known as its polarization. This polarization is given to each photon at the time it was created. But gravity warps everything in the universe, including light. As the CMB photons traveled through the universe past galaxies and stars, they were bent by the gravitational influence of these massive objects, and this bending produced one type of B-mode polarization.
Researchers using the South Pole Telescope might have discovered this first type of B-mode polarization last year. But there is another, more subtle B-mode polarization that cosmologists have also long searched for. In this case, the CMB light was swirled by enormous gravitational waves, which are ripples in the fabric of space-time. The new findings suggest that these gravitational waves could have come from an extremely early period in the universe’s life known as inflation.
According to the Big Bang model of our origins, when the universe was born it immediately began expanding outward. All of space-time ballooned like a stretching sheet. Scientists mostly accepted this Big Bang model in the mid-20th century but it has a few problems. Mainly, it has never made sense how distant parts of the universe could have the same temperature. A point on one side of the universe could never have exchanged radiation or any other sort of information with the other side of the universe, even way back when it was a tiny speck. Yet the CMB, which comes from all around us, is uniform down to one part in ten thousand.
To solve this conundrum, theorists in the 1980s speculated that the very early universe must have been even smaller than we presume. Approximately 0.000000000000000000000000000000000001 seconds after the Big Bang, it suddenly went through an accelerated expansion that drove it to become one thousand quadrillion quadrillion quadrillion quadrillion quadrillion times bigger than it previously was. Inflation brings the universe to the right size for the Big Bang model and all our other observations to make sense.
Using a telescope at the South Pole, a project known as Background Imaging of Cosmic Extragalactic Polarization (BICEP2) has been searching for the B-mode polarizations that would be an echo of this inflationary period. And it seems that now they finally found them. The signal they detected was surprisingly strong, even for members of the team, who have been working on their data for the last three years to rule out any errors.
On Friday, rumors began flying that the BICEP team was about to announce a major discovery. Most cosmologists correctly guessed that the announcement would revolve around B-mode polarizations, but no one was sure exactly what would be announced. Because the team has been able to keep so quiet about their findings (an almost unheard of occurrence in gossipy physics circles), some suspected the data wouldn't be enough to give more than just a hint of the existence of gravitational waves. But today's announcement has proved to be a historic one, with physicists already speculating about who might win a Nobel Prize based on the findings.
Even in the midst of excitedly celebrating, most scientists are urging caution until the results are confirmed by an independent team. "We should be skeptical," said Krauss. "Alone this finding is tantalizing, but not definitive."
In fact, BICEP's data is somewhat at odds with other experiments, such as the Planck space telescope, which have carefully mapped the CMB but not seen primordial B-modes. But it's also possible that these other teams simply missed what BICEP is seeing and, now that they know how to look for the primordial B-modes, can confirm the results fairly quickly using already existing datasets, perhaps within a matter of weeks. No doubt, other collaborations will begin taking new data to try and detect the primordial B-modes on their own.
