Scientists believe that less than a trillionth of a second after the Big Bang, the universe began to rapidly expand as fast as the speed of light. The idea that the universe underwent a rapid expansion is called inflation. As the universe spread out and cooled down, atoms that later made gas, dust, stars and planets were formed.
But what exactly happened at the start of the universe has been unconfirmed until now. With a radio telescope at the South Pole, scientists followed gravitational waves 13.8 billion years into the past and found the first direct evidence of the universe’s rapid expansion immediately following the Big Bang.
“This is a totally new, independent piece of cosmological evidence that the inflationary picture fits together,” said theoretical physicist Alan Guth of MIT, who proposed the idea of inflation in 1980.
Watch the press conference on the discovery here:
This is the first concrete evidence of gravitational waves, a phenomenon first predicted by Einstein 100 years ago. After major cosmic events like the merging of black holes or the Big Bang, gravity makes waves in spacetime that travel like ripples on a pond. These ripples travel at the speed of light, but Einstein thought they would be so feeble, they would be undetectable.
But scientists suspected that these ripples could still be found. Billions of years later, the waves are too weak to measure directly, so scientists have been looking for imprints left on the “cosmic microwave background”, a soup of elementary particles left over from the Big Bang. A U.S.-led team, headed by scientists at the Harvard-Smithsonian Center for Astrophysics, along with the University of Minnesota, Stanford University, the California Institute of Technology and NASA’s Jet Propulsion Laboratory, used a specialized radio telescope called BICEP2 (which stands for Background Imaging of Cosmic Extragalactic Polarization) at the South Pole to hunt for the gravitational waves. The dry air, thin atmosphere and distance from cell phone and radio towers made the South Pole the ideal wave-hunting location.
Finding these primordial gravitational waves is the “smoking gun” in inflation theory, said. Chao-Lin Kuo, assistant professor of physics at Stanford University. While you can never truly prove a scientific theory, this is testable evidence, he said.
“We’re not claiming that we definitely proved the theory,” he said. “It’s the closest to a proof you will ever get.”
The results will be submitted to a scientific journal this week for review and publication, said John Kovac of Harvard, who led the research project.
It’s the most exciting discovery in cosmology for 25 years, said theoretical physicist Lawrence Krauss of Arizona State University, who was not involved with the project. If the evidence of gravitational waves is confirmed, the discovery “gives us a window on the universe at the very beginning,” when it was less than one-trillionth of a second old, he told the Associated Press.
“If you want to know where did we come from, this is it,” Krauss told NewsHour. “We are the products of that burst in empty space.”