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Universe of calculation

THE BALTIMORE SUN

For an astronomer, Adam Riess would make a pretty lame tour guide to the night sky.

He didn't grow up glued to a backyard telescope. He rarely gives the stars a second look after dark. And he's more likely to spot a Ford Taurus on the street than its namesake in the heavens.

"I can find the Big Dipper. I can find Orion," he says, ticking off the stellar geography he knows. "After that, I would be struggling."

But for answers to the big questions - What's the universe made of? How will it end? - this rising young star of astronomy is the guy to see.

Many scientists spend a lifetime quietly probing the cosmos without making a dent. Riess, a 31-year-old astrophysicist at the Space Telescope Science Institute in Baltimore, has made a discovery so profound it upends nearly 70 years of thinking on how the universe ticks.

It sounds like something straight out of "Star Trek": a mysterious invisible force out-muscles gravity, propelling galaxies and other matter outward at an accelerating clip. Baffled scientists dub it "dark energy."

Yet last month, three years after he and others first discovered hints of it, Riess delivered the strongest evidence yet that dark energy is no science fiction.

The findings have sent theoretical physicists into a tizzy and spawned an inflating universe of books and TV documentaries probing its implications. "If it's true," says Alex Filippenko, an astronomer at the University of California at Berkeley, "it's one of the major discoveries of the century."

That a discovery this significant could be made by a scientist who is more comfortable with computers than his constellations shows how astronomy and its practitioners are changing.

Until not too long ago professional stargazing was a tough business, demanding as much physical stamina as scientific know-how. Curled up inside their frosty mountain-top telescopes, astronomers pulled all-nighters photographing the heavens, struggling to suppress the slightest shiver lest it throw off their sensitive instruments.

Later, eyeballing these hard-won snapshots, astronomers struggled to achieve even basic insights: how swirly galaxies looked, for example.

But computers are changing all that. Much as they have revolutionized fields from biology to meteorology, digital technology is making astronomy much less physical and far more precise.

"People don't realize what a high-tech endeavor astronomy is today," says Don Figer, an astronomer at the Space Telescope Science Institute.

At the prestigious Keck Observatory in Mauna Kea, Hawaii, for example, astronomers gaze at the stars on TV screens, in an air-conditioned control room 13,000 feet below the frigid peak.

Astronomers have also abandoned old-fashioned film. Now photons of light dribbling in from the heavens are captured by light-sensitive silicon chips, which have vastly improved how much detail astronomers extract from the sky.

That's where people like Riess come in. He is among the growing number of scientists attracted to what some consider the dirty side of astronomy: mining the growing avalanche of digital data for heavenly secrets.

"I think that's where the next generation of discoveries will come from," Riess says.

He probes the cosmos in a cluttered office with a leafy view of the Johns Hopkins University campus, surrounded by blow-ups of exploding stars (his specialty), tomes on astrostatistics and a whiteboard awash with Ph.D.-level graffiti.

Since he rarely treks to telescopes himself, the photos on his wall are usually as close as he gets to his research subjects. His discoveries, he says, have hinged on his PC and lots of "high-powered" math and statistics.

As far back as he can remember, Riess says, he has been drawn to puzzles and finding out why things are the way they are. As a kid growing up in Warren, N.J., for example, he noticed that people often pass by pennies left on the ground.

Seeding his high school with pennies, nickels, dimes and quarters, he decided to find out how much change it would take to entice someone to pick it up. (His conclusion: His classmates were far too well off, because a teacher was the first to pocket a quarter.)

Chatty and quick with a joke, Riess comes across more like a salesman than a stereotypical science nerd.

He works hard to paint himself as a normal guy who's into pro football, knocking back a few beers, collecting rare coins. Almost as an afterthought, he'll mention that he just happened to study physics at MIT, get his doctorate in astrophysics at Harvard - and, oh yeah, finished his doctorate in four years instead of the typical six.

It was his fascination with puzzles - and a dash of luck - that helped Riess nail one of astronomy's deepest mysteries: How will the universe end?

At the start of the 20th century, most astronomers thought the universe was static, its heavenly bodies like a mobile in a child's bedroom.

Then, in 1929, astronomer Edwin Hubble analyzed the light emanating from several distant galaxies and determined that galaxies were actually roaring away from Earth - the first evidence the universe was growing.

The discovery later gave birth to the modern Big Bang theory - that all space, time, matter and energy exploded outward from an infinitesimally small seed.

But, just as important, Big Bang theory also implied that gravity should be putting the brakes on the ballooning universe, gradually halting its expansion.

So for more than half a century, astronomers have been struggling to pin down this "deceleration parameter." Know how the universe is slowing, astronomers said, and one would know its fate.

If, for example, it turned out the universe was braking hard, the cosmos might slingshot back upon itself in a cataclysmic maneuver delicately referred to as "The Big Crunch." If the slowdown was gradual, the cosmos would die gently, petering out to infinity.

"There was no question the universe was slowing down," Riess says. "It was a question of how much."

How much they were mistaken, that is.

Riess remembers the exact day he and he alone knew the likely fate of the universe. It was late in 1997, and Riess was analyzing data from a new batch of exploding stars in his new office at the University of California at Berkeley.

At the time, exploding stars - or supernovae - were attracting a lot of attention, especially a particular species known as Type Ia. Riess had written his dissertation on them and joined a squad of astronomers at Berkeley and elsewhere hunting the rare objects.

Because those supernovae explode with consistent brightness, astronomers can calculate how far away they are. By comparing the distance of several Type Ia supernovae with their velocity, Riess and his colleagues figured they could pin down the universe's expansion rate at different times in its history (the farther away an object is, the more ancient its light).

But as Riess was analyzing a new batch of supernovae roughly 5 billion light-years away, his computer kept showing him something weird. A key number - the mass of the universe - was coming up negative. "It's a bug," he recalls thinking.

The negative number implied that the universe was speeding up, not slowing down - and that, as everyone knew, was impossible.

After having another astronomer double-check his calculations, Riess finally phoned Robert Kirshner, a collaborator at Harvard. When he heard Riess' results, the implications started to sink in.

"It made me sick to my stomach," recalls Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "I thought we did something wrong. You know, left out pi, or added when we should have subtracted."

But after Riess and his colleagues learned a competing group of supernova hunters was getting strange results, too, they decided to take the risk and tell the world.

Science named dark energy and the accelerating universe its discovery of the year. Between limo rides to the McNeil-Lehrer studios and interviews with the New York Times, Riess called his mother and fretted: "I've peaked early."

But soon after arriving in Baltimore in September 1999 Riess caught wind of another exploding star some of his new colleagues had discovered with the Hubble Space Telescope. Officially known as SN1997ff, today some astronomers simply call it "Adam's lucky supernova."

After six bleary-eyed months staring at pinpricks of light and crunching numbers, Riess determined this supernova was the most distant ever found - 10 billion light-years. More important, it was slowing down.

Together, the two discoveries helped nail the existence of dark energy. When the universe was still young, dark energy hadn't yet become prevalent enough to overpower gravity. That's why SN1997ff was slowing. But later, dark energy filled enough of the universe to overcome gravity and nudge galaxies and other matter outward ever faster.

Now, thanks to Riess and his colleagues, astronomers are getting a clearer picture of the cosmic end game.

Instead of a Big Crunch, scientists now think the universe could balloon out forever. Eventually, speculates astronomer Brian Schmidt of the Australian National University, galaxies will drift so distant from one another that only our own Milky Way will be visible in the night sky.

"It'll become an island universe," says Schmidt. "Your galaxy is it."

Riess, meanwhile, is trying to adjust to all the changes in his own universe.

The discovery of dark energy has turned Riess into a mini-celebrity. Time last fall recognized him as one of the country's hundred rising stars of science. Since last month his phone has been ringing with job offers, book deals and lunch dates with eminent Nobel laureates.

But perhaps the most powerful sign of his newfound fame is that he now has groupies who flood him with their grand theories of how the universe works.

His favorite so far arrived on the back of a Florida public library card.

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