In the beginning, the universe got very big very fast, transforming itself in a fraction of an instant from something almost infinitesimally small to something imponderably vast, a cosmos so huge that no one will ever be able to see it all.
This is the premise of an idea called cosmic inflation -- a powerful twist on the big-bang theory -- and Monday it received a major boost from an experiment at the South Pole called BICEP2.
A team of astronomers, including one from the University of Minnesota, said it had detected ripples from gravitational waves created in a violent inflationary event at the dawn of time.
"We're very excited to present our results because they seem to match the prediction of the theory so closely," team leader John Kovac of the Harvard-Smithsonian Center for Astrophysics said in an interview.
"But it's the case that science can never actually prove a theory to be true. There could always be an alternative explanation that we haven't been clever enough to think of."
The reaction in the scientific community was cautiously exultant. The new result was hailed as potentially one of the biggest discoveries of the past two decades.
Cosmology, the study of the universe on the largest scales, already has been roiled by the 1998 discovery that the cosmos is not merely expanding but doing so at an accelerating rate, because of what has been called "dark energy."
Just as that discovery has implications for the ultimate fate of the universe, this new one provides a stunning look back at the moment the universe was born.
"This discovery gives us direct insight into the birth of the entire universe in which we find ourselves," Clem Pryke, a physics and astronomy professor in the University of Minnesota's College of Science and Engineering and a member of the research team, said in a statement. "It's a holy grail and incredibly exciting."
"If real, it's magnificent," said Harvard astrophysicist Lisa Randall.
The astronomers chose the South Pole for BICEP2 and earlier experiments because the air is exceedingly dry, almost devoid of water vapor and ideal for observing subtle quirks in the ancient light pouring in from the night sky.
They spent four years building the telescope, and then three years observing and analyzing the data. Kovac, 43, who has been to the South Pole 23 times, said of the conditions there, "It's almost like being in space."
The BICEP2 instrument sorts through the cosmic microwave background (CMB), looking for polarization of the light in a pattern that reveals the ripples of gravitational waves. The gravitational waves distort space itself, squishing and tugging the fabric of the universe. This is the first time that anyone has announced the detection of gravitational waves from the early universe.
There are other experiments by rival groups trying to detect these waves, and those efforts will continue in an attempt to confirm the results announced Monday.
The fact that the universe is dynamic at the grandest scale, and not static as it appears to be when we gaze at the "fixed stars" in the night sky, has been known since the late 1920s, when astronomer Edwin Hubble revealed that the light from galaxies showed that they were moving away from one another.
This led to the theory that the universe, once compact, is expanding. Scientists in recent years have been able to narrow down the age of the universe to about 13.8 billion years. Multiple lines of evidence, including the detection of the CMB exactly 50 years ago, have bolstered the consensus model of modern cosmology, which shows that the universe was initially infinitely hot and dense, literally dimensionless. There was no space, no time.
Then something happened. The universe began to expand and cool. This was the big bang.
Cosmic inflation throws gasoline on that fire. It makes the big bang even bangier right at the start. Instead of a linear expansion, the universe would have undergone an exponential growth.
In 1979, theorist Alan Guth, then at Stanford, seized on a potential explanation for some of the mysteries of the universe, such as the remarkable homogeneity of the whole place.
Perhaps the universe did not merely expand in a stately manner but went through a much more dramatic, exponential expansion, essentially going from microscopic in scale to cosmically huge in a tiny fraction of a second.
Staff writer Mila Koumpilova contributed to this report.