CAMBRIDGE, Mass. — One night late in 1979, an itinerant young
physicist named Alan Guth, with a new son and a year’s appointment at
Stanford, stayed up late with his notebook and equations, venturing
far beyond the world of known physics. He was trying to understand why
there was no trace of some exotic particles that should have been
created in the Big Bang. Instead he discovered what might have made
the universe bang to begin with. A potential hitch in the presumed
course of cosmic evolution could have infused space itself with a
special energy that exerted a repulsive force, causing the universe to
swell faster than the speed of light for a prodigiously violent
instant. If true, the rapid engorgement would solve paradoxes like why
the heavens look uniform from pole to pole and not like a jagged,
warped mess. The enormous ballooning would iron out all the wrinkles
and irregularities. Those particles were not missing, but would be
diluted beyond detection, like spit in the ocean. “SPECTACULAR
REALIZATION,” Dr. Guth wrote across the top of the page and drew a
double box around it. On Monday, Dr. Guth’s starship came in. Radio
astronomers reported that they had seen the beginning of the Big Bang,
and that his hypothesis, known undramatically as inflation, looked
right. Reaching back across 13.8 billion years to the first sliver of
cosmic time with telescopes at the South Pole, a team of astronomers
led by John M. Kovac of the Harvard-Smithsonian Center for
Astrophysics detected ripples in the fabric of space-time — so-called
gravitational waves — the signature of a universe being wrenched
violently apart when it was roughly a trillionth of a trillionth of a
trillionth of a second old. They are the long-sought smoking-gun
evidence of inflation, proof, Dr. Kovac and his colleagues say, that
Dr. Guth was correct.
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Inflation has been the workhorse of cosmology for 35 years, though
many, including Dr. Guth, wondered whether it could ever be proved. If
corroborated, Dr. Kovac’s work will stand as a landmark in science
comparable to the recent discovery of dark energy pushing the universe
apart, or of the Big Bang itself. It would open vast realms of time
and space and energy to science and speculation. Confirming inflation
would mean that the universe we see, extending 14 billion light-years
in space with its hundreds of billions of galaxies, is only an
infinitesimal patch in a larger cosmos whose extent, architecture and
fate are unknowable. Moreover, beyond our own universe there might be
an endless number of other universes bubbling into frothy eternity,
like a pot of pasta water boiling over.
‘As Big as It Gets’
In our own
universe, it would serve as a window into the forces operating at
energies forever beyond the reach of particle accelerators on Earth
and yield new insights into gravity itself. Dr. Kovac’s ripples would
be the first direct observation of gravitational waves, which,
according to Einstein’s theory of general relativity, should ruffle
space-time. Marc Kamionkowski of Johns Hopkins University, an
early-universe expert who was not part of the team, said, “This is
huge, as big as it gets.” He continued, “This is a signal from the
very earliest universe, sending a telegram encoded in gravitational
waves.” The ripples manifested themselves as faint spiral patterns in
a bath of microwave radiation that permeates space and preserves a
picture of the universe when it was 380,000 years old and as hot as
the surface of the sun. Dr. Kovac and his collaborators, working in an
experiment known as Bicep, for Background Imaging of Cosmic
Extragalactic Polarization, reported their results in a scientific
briefing at the Center for Astrophysics here on Monday and in a set of
papers submitted to The Astrophysical Journal.
The Theory of Inflation
Astronomers have found evidence to support the theory of inflation,
which explains how the universe expanded so uniformly and so quickly
in the instant after the Big Bang 13.8 billion years ago.
THE UNIVERSE is just under 14 billion years old. From our position
in the Milky Way galaxy, we can observe a sphere that is now about
92 billion light-years across. But there's a mystery. Wherever we
look, the universe has an even temperature.
NOT ENOUGH TIME The
universe is not old enough for light to have traveled the vast
distance from one side of the universe to the other, and there has
not been enough time for scattered patches of hot and cold to mix
into an even temperature.
DISTANT COFFEE At a smaller scale, imagine
using a telescope to look a mile in one direction. You see a coffee
cup, and from the amount of steam, you can estimate its temperature
and how much it has cooled.
COFFEE EVERYWHERE Now turn around and
look a mile in the other direction. You see a similar coffee cup, at
exactly the same temperature. Coincidence? Maybe. But if you see a
similar cup in every direction, you might want to look for another
explanation.
STILL NOT ENOUGH TIME There has not been enough time to
carry coffee cups from place to place before they get cold. But if
all the coffee cups were somehow filled from a single coffee pot,
all at the same time, that might explain their even temperature.
INFLATION solves this problem. The theory proposes that, less than a
trillionth of a second after the Big Bang, the universe expanded
faster than the speed of light. Tiny ripples in the violently
expanding energy field eventually grew into the large-scale
structures of the universe.
FLUCTUATION Astronomers have now
detected evidence of these ancient fluctuations in swirls of
polarized light in the cosmic background radiation, which is energy
left over from the early universe. These are gravitational waves
predicted by Einstein.
EXPANSION Returning to our coffee, imagine a
single, central pot expanding faster than light and cooling to an
even temperature as it expands. That is something like inflation.
And the structure of the universe mirrors the froth and foam of the
original pot.
By LARRY BUCHANAN and JONATHAN CORUM
Dr. Kovac said the chance that the results were a fluke was only one in
10 million. Dr. Guth, now 67, pronounced himself “bowled over,” saying
he had not expected such a definite confirmation in his lifetime. “With
nature, you have to be lucky,” he said. “Apparently we have been lucky.”
The results are the closely guarded distillation of three years’ worth
of observations and analysis. Eschewing email for fear of a leak, Dr.
Kovac personally delivered drafts of his work to a select few, meeting
with Dr. Guth, who is now a professor at Massachusetts Institute of
Technology (as is his son, Larry, who was sleeping that night in 1979),
in his office last week. “It was a very special moment, and one we took
very seriously as scientists,” said Dr. Kovac, who chose his words as
carefully as he tended his radio telescopes. Andrei Linde of Stanford, a
prolific theorist who first described the most popular variant of
inflation, known as chaotic inflation, in 1983, was about to go on
vacation in the Caribbean last week when Chao-Lin Kuo, a Stanford
colleague and a member of Dr. Kovac’s team, knocked on his door with a
bottle of Champagne to tell him the news.
Confused, Dr. Linde called out to his wife, asking if she had ordered
anything. “And then I told him that in the beginning we thought that
this was a delivery but we did not think that we ordered anything, but I
simply forgot that actually I did order it, 30 years ago,” Dr. Linde
wrote in an email. Calling from Bonaire, the Dutch Caribbean island, Dr.
Linde said he was still hyperventilating. “Having news like this is the
best way of spoiling a vacation,” he said. By last weekend, as social
media was buzzing with rumors that inflation had been seen and news
spread, astrophysicists responded with a mixture of jubilation and
caution. Max Tegmark, a cosmologist at M.I.T., wrote in an email, “I
think that if this stays true, it will go down as one of the greatest
discoveries in the history of science.” John E. Carlstrom of the
University of Chicago, Dr. Kovac’s mentor and head of a competing
project called the South Pole Telescope, pronounced himself deeply
impressed. “I think the results are beautiful and very convincing,” he
said. Paul J. Steinhardt of Princeton, author of a competitor to
inflation that posits the clash of a pair of universes as the cause of
genesis, said that if true, the Bicep result would eliminate his model,
but he expressed reservations about inflation. Lawrence M. Krauss of
Arizona State and others also emphasized the need for confirmation,
noting that the new results exceeded earlier estimates based on
temperature maps of the cosmic background by the European Space Agency’s
Planck satellite and other assumptions about the universe. “So we will
need to wait and see before we jump up and down,” Dr. Krauss said.
Corroboration might not be long in coming. The Planck spacecraft will
report its own findings this year. At least a dozen other teams are
trying similar measurements from balloons, mountaintops and space.
Spirals in the Sky Gravity waves are the latest and deepest secret yet
pried out of the cosmic microwaves, which were discovered accidentally
by Arno Penzias and Robert Wilson at Bell Labs 50 years ago. They won
the Nobel Prize. Dr. Kovac has spent his career trying to read the
secrets of these waves. He is one of four leaders of Bicep, which has
operated a series of increasingly sensitive radio telescopes at the
South Pole, where the thin, dry air creates ideal observing conditions.
The others are Clement Pryke of the University of Minnesota, Jamie Bock
of the California Institute of Technology and Dr. Kuo of Stanford. “The
South Pole is the closest you can get to space and still be on the
ground,” Dr. Kovac said. He has been there 23 times, he said, wintering
over in 1994. “I’ve been hooked ever since,” he said.
In 2002, he was part of a team that discovered that the microwave
radiation was polarized, meaning the light waves had a slight preference
to vibrate in one direction rather than another. This was a step toward
the ultimate goal of detecting the gravitational waves from inflation.
Such waves, squeezing space in one direction and stretching it in
another as they go by, would twist the direction of polarization of the
microwaves, theorists said. As a result, maps of the polarization in the
sky should have little arrows going in spirals. Detecting those spirals
required measuring infinitesimally small differences in the temperature
of the microwaves. The group’s telescope, Bicep2, is basically a giant
superconducting thermometer. “We had no expectations what we would see,”
Dr. Kovac said. The strength of the signal surprised the researchers,
and they spent a year burning up time on a Harvard supercomputer, making
sure they had things right and worrying that competitors might beat them
to the breakthrough. A Special Time The data traced the onset of
inflation to a time that physicists like Dr. Guth, staying up late in
his Palo Alto house 35 years ago, suspected was a special break point in
the evolution of the universe. Physicists recognize four forces at work
in the world today: gravity, electromagnetism, and strong and weak
nuclear forces. But they have long suspected that those are simply
different manifestations of a single unified force that ruled the
universe in its earliest, hottest moments. As the universe cooled,
according to this theory, there was a fall from grace, like some old
folk mythology of gods or brothers falling out with each other. The laws
of physics evolved, with one force after another splitting away. That
was where Dr. Guth came in. Under some circumstances, a glass of water
can stay liquid as the temperature falls below 32 degrees, until it is
disturbed, at which point it will rapidly freeze, releasing latent heat.
Similarly, the universe could “supercool” and stay in a unified state
too long. In that case, space itself would become imbued with a
mysterious latent energy. Inserted into Einstein’s equations, the latent
energy would act as a kind of antigravity, and the universe would blow
itself up. Since it was space itself supplying the repulsive force, the
more space was created, the harder it pushed apart. What would become
our observable universe mushroomed in size at least a trillion
trillionfold — from a submicroscopic speck of primordial energy to the
size of a grapefruit — in less than a cosmic eye-blink. Almost as
quickly, this pulse would subside, relaxing into ordinary particles and
radiation. All of normal cosmic history was still ahead, resulting in
today’s observable universe, a patch of sky and stars billions of
light-years across. “It’s often said that there is no such thing as a
free lunch,” Dr. Guth likes to say, “but the universe might be the
ultimate free lunch.” Make that free lunches. Most of the hundred or so
models resulting from Dr. Guth’s original vision suggest that inflation,
once started, is eternal. Even as our own universe settled down to a
comfortable homey expansion, the rest of the cosmos will continue
blowing up, spinning off other bubbles endlessly, a concept known as the
multiverse. So the future of the cosmos is perhaps bright and fecund,
but do not bother asking about going any deeper into the past. We might
never know what happened before inflation, at the very beginning,
because inflation erases everything that came before it. All the chaos
and randomness of the primordial moment are swept away, forever out of
our view. “If you trace your cosmic roots,” said Abraham Loeb, a
Harvard-Smithsonian astronomer who was not part of the team, “you wind
up at inflation.”
A version of this article appears in print on March 17, 2014, Section A, Page 1 of the New York edition with the headline: Space Ripples Reveal Big Bang’s Smoking Gun. Order Reprints | Today’s Paper | Subscribe