By John Lauerman and Robert Langreth
Ripples in ancient light form the first direct evidence of the Big Bang, the original expansion of the universe from a tiny compressed spot that led to its present size, scientists reported today.
Waves from the initial expansion still exist in cosmic background microwaves, a form of light that remains from the universe’s earliest days, a team from institutions including Harvard-Smithsonian Center for Astrophysics, Stanford University and the California Institute of Technology, said in a statement.
Scientists have theorized for decades that the universe began with a flash of rapid expansion about 14 billion years ago, and measurements of light from distant stars show it’s still expanding. Using measurements from a telescope able to detect how gravitational waves affected the cosmic background microwaves, the researchers could see the signature of the Big Bang, said John Kovac, an astrophysicist at the Harvard- Smithsonian center in Cambridge, Massachussetts.
“Detecting this signal is one of the most important goals in cosmology today,” said Kovac, who led the collaboration. “A lot of work by a lot of people has led up to this point.”
Just as the light we see is polarized, the ancient light of cosmic microwaves also has polarity, which is affected by gravitational waves, the researchers said. Using ultrasensitive telescopes, the researchers searched for so-called B-modes -- curl patterns in the polarized cosmic microwaves.
The team, whose project was called BICEP2, gathered what it said were the first images of these gravitational waves, or the “first tremors of the Big Bang.” The results show the connection between quantum mechanics, the behavior of small particles that make up the universe, and general relativity, the overall theory of how the most basic types of matter interact, the researchers said.
The finding, if confirmed, would provide strong evidence for the inflation theory, which holds that the universe underwent a period of extraordinarily rapid acceleration outwards at its very beginning.
“The experiment is incredibly impressive,” said Lawrence Krauss, a cosmologist at Arizona State University in Phoenix. It is observing “a signal from the very early universe, from the beginning of time.”
“In some sense, it is answering the question of why there is something rather than nothing,” Krauss said in a telephone interview. “If we are interested in our own origins, how the universe began and why we are here, this is addressing empirically that question.”
The new experiment is measuring light emitted when the universe first became transparent to light, roughly 378,000 years after the Big Bang, said Paul Steinhardt, a theoretical cosmologist at Princeton University. It is “roughly akin to observing a picture of yourself 10 minutes after conception,” said Steinhardt, who has worked on both inflation and competing theories about how the universe started.
“If this is true -- it’s a big if -- it eliminates certain competing models for explaining the large scale structure of the universe,” Steinhardt said in a telephone interview before the results were announced.
It will take some time for researchers to confirm the collaboration’s findings as the experiment involved making very subtle measurements, he said.
Krauss, of Arizona State University, said the BICEP2 research team appeared to have put a great deal of effort into ruling out the possibility that they saw the inflation signal by accident, as a result of dust from the galaxy or due to problems with the detector.
To help get clear pictures of these ancient waves, the researchers traveled to the South Pole, where the air is cold, dry, and stable, according to the statement.
“The South Pole is the closest you can get to space and still be on the ground,” Kovac said. “It’s one of the driest and clearest locations on Earth, perfect for observing the faint microwaves from the Big Bang.”
Other institutions collaborating on the research are the University of Minnesota in Minneapolis, the University of California at San Diego, the University of British Columbia in Vancouver, the U.S. National Institute of Standards and Technology in Gaithersburg, Maryland, the University of Toronto, Cardiff University in the U.K., and Commissariat à l’Energie Atomique in France.