MESSAGE
| DATE | 2006-03-16 |
| FROM | Ruben Safir
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| SUBJECT | Subject: [NYLXS - HANGOUT] A small marble beginning
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March 16, 2006
Scientists Get Glimpse of First Moments After Beginning of Time
By DENNIS OVERBYE
Using data from a new map of the baby universe, astronomers said today
that they had seen deep into the big bang that allegedly started the
universe and had got their first detailed hint of what was going on less
than a trillionth of a second after time began.
The results, they said, validated a key prediction of a speculative but
very popular theory, known as inflation, about the distribution of
matter and energy in the big bang. The theory holds that that, during
its first moments, the universe, fueled by an anti-gravitational field,
underwent a violent growth spurt, called inflation. It ballooned from
the size of a marble to larger than the observable universe today in
less than an eyeblink.
"It amazes me that we can say anything about the universe in the first
trillionth of a second," said Charles L. Bennett, a professor at Johns
Hopkins.
"It appears that the infant universe had the kind of growth spurt that
would alarm any mom or dad," he said. Dr. Bennett is the leader of the
group that reported its results today in a news conference and on the
Web site lambda.gsfc.nasa.gov.
The new map was produced by a NASA satellite known as the Wilkinson
Microwave Anisotropy Probe. It has been circling the Earth at a point on
the other side of the Moon since 2001, recording the faint emanations of
microwaves thought to be the remains of the fires of the Big Bang. The
cosmic microwaves paint a portrait of the universe when it was only
380,000 years old, astronomers say, but in the details of that portrait
are clues to processes that occurred when it was much, much younger.
Using the new map, the Wilkinson team has been able to revise an earlier
estimate of the time at which the first stars began to form and shine
through the primordial murk that followed the cooling of the big bang
fires. Those stars appeared when the universe was about 400 million
years old, they said today. The previous estimate of 200 million years,
based on earlier Wilkinson data, had been seen as surprisingly early by
many cosmologists and the new date is comfortably in line with
mainstream theories.
The data have also reaffirmed the suite of attributes that these days go
under the heading of the "preposterous universe," a universe that is
13.7 billion years old, speeding up its expansion instead of slowing
down and awash in mysterious dark matter.
Inflation theory, which was invented by Alan Guth of the Massachusetts
Institute of Technology in 1980, has been the workhorse of big bang
cosmology for the last 25 years. But astronomers and physicists admit
that they still have no idea what might have caused inflation, because
it happened at temperatures and energies unattainable by any particle
accelerator on Earth. As a result, there are a welter of models
describing how it might have worked.
Although inflation is not yet conclusively confirmed, it is now in
better shape than ever, many astronomers said, and many models can be
eliminated.
"We've crossed a threshold," said David N. Spergel of Princeton. "We can
now start to say something interesting about the physics of inflation."
Others, not involved in the project tended to agree.
"If this holds up to the test of time, it's a real landmark," said Max
Tegmark, a cosmologist and cosmic microwave expert at M.I.T. "I really
feel like the universe has given up one more clue," he said.
Dr. Guth, who is at a conference in the Caribbean, was said to be
walking around with a big smile.
Brian Greene, a physicist at Columbia, said that the Wilkinson team
would someday be remembered "as heroes who played a key role" in the
evolution of cosmology into a mature science.
The new map has been eagerly awaited by astronomers, who last heard from
the Wilkinson group in 2003, when it released its first map, showing the
cosmos speckled with faint hot and cool spots — the seeds from which
structures like galaxies would eventually grow.
Three years is a long time to go between baby pictures.
Dr. Bennett and his colleagues have spent the last three years making a
much more difficult measurement. In effect, they were using their
spacecraft antennas like a pair of Polaroid sunglasses to measure the
polarization of the big bang microwaves. To make these measurements,
which required 100 times the sensitivity of the previous heat
measurements, the astronomers essentially had to recalibrate their
entire spacecraft and the way they looked at the data.
"We had to rewrite the whole software pipeline — twice," Dr. Spergel
said.
The light waves from the big bang, they found, do not vibrate randomly
at all different directions as they travel from the distant past to us.
Rather, they have a slight preference to line up in one plane. Lyman
Page of Princeton compared it to the glare from sunlight bouncing off
the hood of a car. The reflection causes the light waves to want to
oscillate in a horizontal direction. In the case of the car, sunglasses
can eliminate the glare. In the case of the big bang microwaves, he
said, "We measure the glare."
What plays the role of the hood of the car in this story, Dr. Page said,
is a fog of electrons floating in space between us and the Big Bang.
This fog was produced, so the story goes, by radiation from the first
stars ripping apart atoms in space and liberating their electrons.
Measuring the polarization caused by microwaves bouncing off this fog
was key to the new results. First it allowed the Wilkinson team to
refine their previous estimate of when the stars first turned on.
Second, and perhaps more important, by correcting for this fog, the
astronomers were able to measure fluctuations in the microwaves more
accurately than they had before.
This allowed them to confront for the first time an important prediction
of inflation theory. For 30 years, cosmologists had presumed that the
waves and ripples in the early universe followed a simple pattern,
namely that their brightness was independent of their size.
But according to inflation, the brightness of the bumps should be
slightly dependent on their apparent sizes in the sky. Smaller bumps
should be slightly dimmer than big ones.
The reason, Dr. Spergel explained, is that the force driving inflation
is falling as it proceeds. The smaller bumps would be produced later and
so a little less forcefully than the bigger ones.
That, in fact, is exactly what the Wilkinson probe has measured. Dr.
Spergel said, "It's very consistent with simplest inflation models, just
what inflation models say we should see."
Michael Turner, a cosmologist at the University of Chicago, called the
results, "the first smoking gun evidence for inflation."
But Paul Steinhardt of Princeton, who has lately championed an
alternative to inflation, in which the universe begins and ends
cyclically in a collision between a pair of island universes, know in
string theory as branes, pointed out that the new data are also
compatible with his theory. Calling the results "extremely important,"
he noted that they were in agreement with the simplest models of these
theories.
"It rules out need for anything exotic," he said.
Andrei Linde of Stanford, one of the leading inflationary theorists,
noted that his own favorite model was still in the running and exclaimed
in an email message from Moscow, "Great day for cosmology!"
The stage is now set for a race to achieve the next milestone, the true
smoking gun for inflation. If inflation is right, there should be a
whole other pattern of polarization, even fainter than the one that was
announced today, due to gravity waves, the roiling of space-time by the
violent wrench of inflation.
The detection of those waves would confirm inflation and eliminate Dr.
Steinhardt's alternative.
Dr. Spergel said that if those waves were there the Wilkinson probe
might be able to see them with a few more years of accumulating data.
But in 2007 the European Space Agency is scheduled to launch its Planck
satellite, which will also search for the gravitational wave signals.
In the meantime, various balloon and ground-based telescopes will also
take aim at the cosmic microwaves, hoping to get a piece of the action.
Dr. Steinhardt said, "If you want to know where you came from, and where
you're going, that's the issue at stake."
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