The South Pole Telescope and the BICEP (Background Imaging of Cosmic Extragalactic Polarization) Telescope at Amundsen-Scott South Pole Station. REUTERS/Keith Vanderlinde/National Science Foundation
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
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
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
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."