Like a biography with a missing first chapter, the story of our universe has always left a big question unanswered about how it all began.
Observations that probe the farthest reaches of space have taken scientists nearly 13.8 billion years back in time, but no farther. Before then, light could not travel freely, and so the earliest moments of the universe are opaque to astronomers.
Now, a team of researchers says it has filled in the missing part of the story. By looking at a pattern frozen into the most distant part of the universe that can still be observed directly – a boundary known as the cosmic microwave background – the scientists say they have gained a crucial insight into what is going on still deeper, at the threshold of creation.
The find has electrified cosmologists, who are eager to confirm it and to understand its deeper implications.
"If it is verified, this measurement is astounding, and a great leap forward," said Richard Bond, director of the cosmology and gravity program for the Canadian Institute for Advanced Research, who was not a member of the team.
The measurement revealed on Wednesday is the product of an experiment called BICEP2, which is at the South Pole, where the cold, dry air is ideal for observing the cosmic background. The experiment spotted swirl-like patterns buried in the background that are thought to contain information from when the universe was less than one second old.
"The most reasonable interpretation of the signal is that it is gravitational waves," said Marc Kamionkowski, professor of physics and astronomy at Johns Hopkins University.
Gravitational waves, first predicted by Albert Einstein in 1951, are ripples in spacetime, something like what happens when a stone is tossed into a pond. Theorists suggest that if the universe began with a period of rapid expansion, called cosmic inflation, it should have produced such ripples aplenty.
The BICEP2 results imply that gravitational waves were generated by inflation and then subtly affected the distribution of matterin the very early universe. The pattern they left was imprinted in the microwave background.
If correct, the new find would be the oldest information ever obtained about the early universe. And while it appears, at least at face value, to bolster the inflation hypothesis, it does not yet rule out all other contenders.
Neil Turok, a cosmologist and director of the Perimeter Institute of Theoretical Physics in Waterloo, Ont., is among those who have championed a cyclic theory of the universe, in which the Big Bang is just the start of the latest in a series of recurring episodes of expansion. Dr. Turok acknowledged that such a universe would be ruled out by the new result (if confirmed), although more recent modifications of the theory "might still be viable."
The pattern observed by BICEP2 is also stronger than many expected, which may improve prospects for verifying the new discovery relatively soon. "There's a whole bunch of experiments that in the next few years are either going to confirm or deny these results," said Barth Netterfield, a University of Toronto researcher involved in several of the experiments.
"The great thing is that it's much easier to design experiments to measure these things if you know where to aim at," said Duncan Hanson, a McGill University cosmologist involved with a similar experiment, the South Polar Telescope, located next to BICEP2.
An earlier online version of this story incorrectly identified Marc Kamionkowski as a member of the BICEP2 team. This online version has been corrected.