Astronomers say they have discovered what many consider the holy grail of their field: ripples in the fabric of space-time that are echoes of the massive expansion of the universe that took place just after the Big Bang.
Predicted by Albert Einstein nearly a century ago, the discovery of gravitational waves would be the final piece in one of the greatest achievements of the human intellect: an understanding of how the universe began and evolved into the cornucopia of galaxies and stars, nebulae and vast stretches of nearly empty space that constitute the known universe.
"Detecting this signal is one of the most important goals in cosmology today," John Kovac of the Harvard-Smithsonian Center for Astrophysics, who led the research, said in a statement.
Gravitational waves are feeble, primordial undulations that propagate across the cosmos at the speed of light. Astronomers have sought them for decades because they are the missing evidence for two theories.
One is Einstein's general theory of relativity, published in 1915, which launched the modern era of research into the origins and evolution of the cosmos. The general theory explains gravity as the deformation of space by massive bodies. Einstein posited that space is like a flimsy blanket, with embedded stars and planets causing it to curve rather than remain flat.
Those curvatures of space are not stationary, Einstein said. Instead, the gravitational waves propagate like water in a lake or seismic waves in Earth's crust.
The other theory that predicted gravitational waves is called cosmic inflation. Developed in the 1980s, it posited that in less time than the blink of an eye after the Big Bang, the infant cosmos expanded exponentially, inflating in size by 100 trillion trillion times.
The Big Bang is the explosion of space-time that began the universe 13.8 billion years ago.
In addition to making the cosmos remarkably uniform across vast expanses of space, inflation caused everything it touched to balloon exponentially. That included tiny fluctuations in gravity that, when inflated, became gravitational waves.
Although the theory of cosmic inflation received a great deal of experimental support, the failure to find the gravitational waves it predicted caused many cosmologists to hold off their endorsement.
That may change after the announcement today.
"These results are not only a smoking gun for inflation, they also tell us when inflation took place and how powerful the process was," said Harvard University physicist Avi Loeb. The strength of the gravitational waves' signal is tied to how powerfully the universe expanded during the brief era of inflation.
The measurements announced by the astronomers today are nearly twice as large as cosmologists predicted for gravitational waves, suggesting a great deal more could be learned about how inflation worked.
SOUTH POLE TELESCOPE
The gravitational waves were detected by a radio telescope called BICEP2 (Background Imaging of Cosmic Extragalactic Polarization). The instrument, which scans the sky from the South Pole, examines what is called the cosmic microwave background, the extremely weak radiation that pervades the universe. Its discovery in 1964 by astronomers at Bell Labs in New Jersey was hailed as the best evidence to date that the universe began in an immensely hot explosion.
The microwave background radiation, which has been bathing the universe since 380,000 years after the Big Bang, is a mere 3 degrees above absolute zero, having cooled to near non-existence from the immeasurably hot plasma that was the universe in the first fractions of a second of its existence.
The background radiation is not precisely uniform. Like light, the relic radiation is polarized as the result of interacting with electrons and atoms in space.
Computer models predicted a particular curl pattern in the background radiation that would match what would be expected with the universe's inflation after the big bang.
"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 statement.
Jamie Bock, a physics professor at the California Institute of Technology and co-leader of the study, added: "The implications for this detection stagger the mind. We are measuring a signal that comes from the dawn of time."
