For the first time, scientists have found direct evidence of the expansion of the universe, a previously theoretical event that took place a fraction of a second after the Big Bang explosion nearly 14 billion years ago.
The clue is encoded in the primordial cosmic microwave background radiation that continues to spread through space to this day.
Scientists found and measured a key polarization, or orientation, of the microwaves caused by gravitational waves, which are miniature ripples in the fabric of space.
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Gravitational waves, proposed by Albert Einstein's General Theory of Relativity nearly 100 years ago but never before proven, are believed to have originated in the Big Bang explosion and then been amplified by the universe's inflation.
"This detection is cosmology's missing link," physicist Marc Kamionkowski, at Johns Hopkins University, told reporters during a webcast press conference on Monday.
"It's something that we thought should be there, but we weren't really sure. It has been eagerly sought now for close to two decades," he said.
Because gravitational waves squeeze space as they travel, they imprint a specific pattern in the cosmic microwave background. Like light waves, gravitational waves have "handedness" that correlates to left- and right-skewed polarizations.
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Using a special telescope located at the South Pole, scientists not only detected gravitational waves in the universe's fossil radiation; they also found that the telltale polarization signals are much stronger than expected.
"This has been like looking for a needle in a haystack, but instead we found a crowbar," team co-leader Clem Pryke, with the University of Minnesota, said in a press release.
In addition to providing the first direct evidence of the universe's inflation, the measurements can be used to date the process and determine how much energy it took.
"This is not something that's just a home run, but a grand slam. It's the smoking gun for inflation. It hints at unification of the fundamental forces at energies 10 trillions of times higher than those accessible at the Large Hadron Collider at CERN," Kamionkowski said.
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Computer models indicate that the universe expanded by 100 trillion trillion times in .0000000000000000000000000000000001 (10 to the minus-34) seconds after the Big Bang explosion 13.8 billion years ago.
The telescope used to detect the gravitational waves is called Bicep, short for Background Imaging of Cosmic Extragalactic Polarization.
"These results are as extraordinary as they get, and they will require the most extraordinary scrutiny," Kamionkowski said.
"If these results hold up ... then we've learned only that inflation has sent us a telegram, encoded on gravitational waves and transcribed on the cosmic microwave background sky. It will be essential in the years to come to follow through with more detailed and precise measurements to infer fully what this telegram is telling us," he added.