By Cheryl Pellerin
Washington File Staff Writer

Washington – Scientists from the NASA Goddard Space Flight Center in Maryland and the U.S. Department of Energy (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab)/University of California-Berkeley won the 2006 Nobel Prize in physics October 3.

The Royal Swedish Academy of Sciences announced the award of the prize to John Mather, 60, and George Smoot, 61, for “work that looks back into the infancy of the universe and attempts to gain some understanding of the origin of galaxies and stars,” according to a Nobel Foundation statement.

The work was based on measurements made with the help of the Cosmic Background Explorer (COBE) satellite, launched by NASA in 1989.

The COBE results provided increased support for the Big Bang scenario for the origin of the universe, the only scenario that predicts the kind of cosmic microwave background radiation measured by COBE. The measurements - of faint signatures of the early universe left behind in the form of background radiation - also marked the inception of cosmology as a precise science.

It was important to observe the background radiation from space, Mather said in an October 3 telephone interview with Adam Smith, editor in chief of the Nobel Foundation Web site, because Earth’s atmosphere absorbs the radiation.

“Even at wavelengths where the radiation does come through,” Mather added, “the atmosphere emits its own radiation, which confuses matters quite a lot. So it really was important to get up into space where it’s cold and quiet.”

When the scientists used the COBE satellite to observe the earliest galaxies, Smoot said during his telephone interview with Smith, they were looking back in time 300,000 to 400,000 years after the Big Bang that created the present universe.

“In human terms,” Smoot said, “it’s like looking at an embryo that’s a few hours old. That’s how far back we’re looking.”

“ACCUMULATED TRACE OF EVERYTHING”

The Big Bang theory says the universe began billions of years ago with the explosion of a superdense atom and has been expanding ever since.

In the first submicroseconds of the early universe, Mather said, all of the cosmic particles - protons, electrons, unstable nuclear particles, neutrinos and photons and background radiation - were all hot and all together.

Then, as the universe expanded, he added, each kind of particle either disappeared, because it was unstable, or annihilated another kind of particle, and they all cooled down. The cosmic microwave background radiation is actually a remnant that traces back to those very earliest moments.

The Nobel laureates’ calculations, according to Mather, say “that the radiation [called blackbody radiation] really did come from the Big Bang. There really is not a good alternative explanation for having such a perfect blackbody spectrum. Many people looked, but no good explanation was found, and so the Big Bang theory is confirmed by that spectrum.” He added, “I think of [the cosmic microwave background radiation] as the accumulated trace of everything.”

COBE’s success was the outcome of prodigious teamwork involving more than 1,000 researchers, engineers and other participants. Mather coordinated the entire process and had primary responsibility for the experiment that revealed the blackbody form of the microwave background radiation measured by COBE. Smoot had main responsibility for measuring the small variations in the temperature of the radiation.

Extremely small differences in the temperature of the cosmic background radiation – in the range of a hundred-thousandth of a degree – offer an important clue to how the galaxies came into being.

The variations in temperature show how matter in the universe began to “aggregate.” This was necessary if the galaxies, stars and, ultimately, life were to be able to develop. Without this mechanism, matter would have taken a completely different form, spread evenly throughout the universe.

BIG BANG

Smoot has been an astrophysicist at the DOE Berkeley Lab since 1974 and a University of California at Berkeley physics professor since 1994.

At a May 1992 meeting of the American Physical Society, Smoot made an announcement that silenced all the scientific critics of the Big Bang theory and helped change the course of future investigations into the origin and evolution of the universe.

Smoot and his research team, after analyzing hundreds of millions of precision measurements in the data they had gathered from an experiment aboard NASA's COBE satellite, produced maps of the sky that showed "hot" and "cold" regions with temperature differences of a hundred-thousandth of a degree.

These temperature fluctuations, produced when the universe was smaller than a single proton, were consistent with Big Bang predictions and are believed to be the primordial seeds that produced the present universe.

"At the time, captured in our images, the currently observable universe was smaller than the smallest dot on your TV screen," Smoot said, "and less time had passed than it takes for light to cross that dot."

Theorists had predicted temperature variations in the ancient universe since the Big Bang theory was first developed in the 1940s. But until Smoot and his team announced their discovery, the cosmic background radiation - microwaves left over from the Big Bang that have taken some 15 billion years to reach Earth - had appeared to be persistently uniform.

“You never prove anything completely,” Smoot said. “but [the Big Bang theory] is the accepted theory of cosmology.

Smoot said his group would continue its investigations, along with other international research groups. These include NASA’s Wilkinson Microwave Anisotropy Probe, a mission launched in 2001 to measure the temperature of the cosmic background radiation over the full sky with unprecedented accuracy, and the European Space Agency’s Max Planck Surveyor Satellite, to be launched in 2008, which is designed precisely to image small differences in the temperature of the cosmic background radiation field.

“The better we measure,” Smoot said, “the more precisely we’re going to know the general parameters of the universe.”

The 2006 Nobel laureates will gather in Stockholm, Sweden, December 10 to receive their Nobel Prize medal, diploma and monetary award from King Carl Gustav XVI of Sweden.

More information about the Nobel Prizes is available on the academy’s Web site.