Physics @ Berkeley
Physics in the News
Title: Scientist Discovers The Genuine Dark Side
Date: 07/03/2006
Publication: Contra Costa Times
Editor: Betsy Mason
Extended Text:

BERKELEY - Sitting in his office at Berkeley Lab, with his slight frame, thick glasses, slightly wrinkled khaki pants, short-sleeved button-down shirt and sneakers, and surrounded by unruly stacks of papers, books, folders, computers and white boards filled with equations, physicist Saul Perlmutter is one pocket protector away from fitting the scientist stereotype to a T.

But Perlmutter is not your average scientist.

"I think there's a good chance Saul will win a Nobel Prize," said Steven Chu, director of Lawrence Berkeley Laboratory, himself a Nobel Prize-winning physicist.

Perlmutter is an idea man. It's one of the first things people say about him, that he is literally brimming with ideas.

His eyes light up and a smile quickly takes over his face as he explains how one of those ideas led his team to discover dark energy, a mysterious form of energy that makes up more than two- thirds of the universe.

"This is the biggest discovery in the history of science," said Berkeley Lab physicist Bob Cahn. "They discovered more than half of the universe. Nobody can ever make a bigger discovery."

In what could be a prelude to the Nobel Prize, last month Perlmutter won the prestigious Shaw Prize in Astronomy for the discovery. He will share the $1 million prize with two other scientists who were part of a second team that followed his lead to make the same discovery at nearly the same time.

The road to the dark energy discovery was a steep climb for Perlmutter, paved with skepticism and resistance from top astronomers. It took a heap of his own energy to get there.

Fortunately, he has plenty of energy. So much, in fact, that he can barely talk fast enough to keep up with himself.

"It's a torrent of words and ideas," said his wife, Laura Nelson, a Cal State East Bay anthropologist. "It's exciting, but it's overwhelming at times. We had to work out a system where he talks and then I talk."

Nelson's theory about this is that Perlmutter has to pack as much as he can into every minute because of the nature of his chosen field of study. "The universe is really, really big," she said.

Outside of science his life is equally packed. He fits the old-school mold of the well-rounded, cultured physicist. At Harvard, he seriously considered a double major in physics and philosophy.

Until recently, Perlmutter was often singing choral music, gathering groups of musicians to join his violin playing, or heading out for an evening of Israeli folk dancing.

These days most of the singing he does is to his daughter, Noa, who is on the verge of turning 3. Many of the games and activities he plans for her are designed to encourage creativity, and he said he won't be surprised if she ends up a scientist as well.

Like Noa, Perlmutter grew up with academic parents, his father a chemical engineer his mother in social work.

"I was one of those kids who enjoyed trying to understand how the world works," he said.

The drive to understand the working

s of the universe set Perlmutter on the path to a revelation that would turn astronomy on its head.

His first steps came as a graduate student at UC Berkeley in the early 1980s. His adviser was attempting to measure the expansion of the universe using nearby exploding stars, or supernovae. Perlmutter's involvement in this project eventually sparked the idea that more distant explosions could reveal whether the expansion is constant or not.

Most scientists at that time believed the universe's expansion was slowing down. It was the logical progression: The Big Bang sent matter sailing off in all directions but, after a brief period of acceleration, the gravitational pull of all that matter would slow the expansion and perhaps even reverse it, causing the universe to collapse in on itself far in the future.

Perlmutter believed he could measure that deceleration, and consequently predict the universe's time of death by looking at light from stellar explosions in distant galaxies.

Supernovae are useful because they all give off the same amount of light. So by measuring how bright they appear to observers on earth, astronomers can deduce how far away they are. And as the light travels toward earth, it is stretched by the expansion of the universe. Stretching light gives it a longer wavelength, which makes it appear more red, a concept known as red shift.

By combining the supernova's distance from earth with the red shift, Perlmutter hoped to measure the change in the speed of expansion of the universe.

But catching supernovae would be a challenge. An average galaxy has just one or two supernovae per millennium, each visible for only a couple of weeks. So aiming a telescope at the right place at the right time to capture even one supernova, let alone the scores needed for a reliable measurement, would be tricky.

While at Berkeley Lab, where he landed after earning his Ph.D., Perlmutter's team devised an instrument that could look at a bigger slice of sky than previously possible, greatly increasing the odds of seeing a supernova. He believed he could capture as many as a dozen with just a few days of telescope time.

But the astronomy community was skeptical of this group led by a young physicist, and was not eager to grant precious time on the few telescopes that could see far enough.

"There was a general feeling at the time that it was not going to work for a number of reasons," Perlmutter said.

But he was not swayed. "It was pretty clear to me that these were all solvable problems in principle," Perlmutter said. "I didn't see any show-stoppers."

Motivated by the importance of the question he hoped to answer -- whether the universe would some day end -- he persisted. "It was such a great question to ask that the sort of result you could get if you could do this was so huge. I thought, 'Why wasn't everybody doing this?'"

Eventually, after years of pushing, he got his foot in the door of some of the less popular, less powerful telescope facilities, and by piecing together a few clear nights here and there, the team found a half dozen supernovae in 1994 and 1995. Armed with this proof of principle, they worked their way up to the best telescopes and by 1997 had collected 42 of the elusive stellar explosions.

What they learned from their trove of supernovae stunned astronomers. The expansion was not slowing down. The opposite was true: the universe was expanding at ever faster rates.

For this unexpected reality to make sense, there had to be some as yet unknown force in the universe counteracting the gravitational pull of the matter that would otherwise slow the expansion and eventually reverse it.

This unknown force is known as dark energy, a strange form of energy that has a very strong negative pressure that works against gravity. Nobody knows exactly what dark energy is, just that it is unlike anything else we know. But in order for the expansion to be accelerating as fast as it is, dark energy has to make up around 72 percent of the universe.

"Everything we know about dark energy is that it's there," said Cahn. "It's not like anything vaguely familiar. It's not like light. It's not like matter. It's something else."

The discovery changed everything and opened up a whole new field of astronomy.

"Saul is seen as somebody who has blazed the way for the modern era," said Berkeley Lab particle physicist Tony Spadafora. "Now basically everybody in cosmology is trying to understand what is the nature of dark energy."

And that includes Perlmutter. He is as busy as ever trying to convince NASA to build and launch a space telescope he designed to get a better look at the supernovae. If he succeeds, the Supernova/Acceleration Probe could get off the ground as early as 2013 and Perlmutter can begin testing more big ideas and chipping away at the mystery of dark energy.

In the meantime, his colleagues are waiting to see if the Nobel committee will recognize his biggest idea yet. "He deserves it," said Chu.

Betsy Mason covers science. Reach her at 925-847-2158 or


Name: Saul Perlmutter

Age: 46

Occupation: Physicist

Residence: Berkeley

Claim to Fame: Discovered dark energy