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
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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.
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 UNIVERSEis 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 TIMEThe 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 EVERYWHERENow 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 TIMEThere 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.
FLUCTUATIONAstronomers 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.
EXPANSIONReturning 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.
Stanford Professor Andrei Linde celebrates physics breakthroughVideo by
StanfordUniversity
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.
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 18, 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
A version of this article appears in print on March 18, 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
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