3 Awarded Nobel Prize in Physics

A Japanese scientist and two Americans have won the 2002 Nobel Prize in physics for snatching elusive cosmic particles and bits of radiation that constantly pelt the Earth and using them to understand the basic workings of the sun and stars and to unveil the previously hidden but incredibly violent nature of our universe.

University of Pennsylvania chemist Raymond Davis Jr., 87, and retired University of Tokyo physicist Masatoshi Koshiba, 76, shared half of the $1.1-million prize for their pioneering work on detecting solar neutrinos--ghostly particles that stream out of the heart of the sun by the thousands of billions, change “flavors” as they bombard Earth and pass easily through solid rock, making them almost impossible to snare.

The two men created fantastical underground chambers--one in a South Dakota gold mine, the other in a Tokyo copper mine--to trap and study the particles. The work resolved a centuries-old controversy by proving that it was indeed nuclear fusion that made the sun shine. The work also suggested that all those neutrinos each seemed to contain a sliver of mass, meaning the universe was not as lopsided as once believed.

The other half of the prize went to Riccardo Giacconi, 71, an astronomer who was the first to detect X-rays coming from outside our solar system and the first to prove that the universe is bathed in a background glow of X-rays. The work proved the existence of black holes and established an entirely new field of astrophysics, X-ray astronomy, that has gone on to illuminate many surprisingly violent aspects of the night skies.

“It’s not just that the winners have written new sentences in the history of science, they’ve written whole new chapters,” said John Bahcall, an astrophysicist at the Institute for Advanced Study in Princeton, N.J., who worked closely with Davis on solar neutrinos and called Giacconi “a giant.”

The Nobel committee said X-ray astronomy had provided “completely new--and sharp--images of the universe” and described neutrino detection as “considerably more difficult than finding a particular grain of sand in the whole of the Sahara desert.” They credited the work with changing “the way we look upon the universe.”

The prizes did not come as a surprise to many in the physics community, or even to one winner. When the phone rang in his Tokyo home, “I said, ‘Oh, that must be it,’ ” a smiling Koshiba told dozens of reporters who clustered at his house shortly after the announcement. “Having won the prize, I can finally return to my quiet life.”

Davis, who suffers from early-stage Alzheimer’s disease and now lives in semi-retirement on Long Island, did not make public comments about his award. His reaction to colleagues was a modest one. “I don’t deserve this,” he told his University of Pennsylvania collaborator Ken Lande, saying the award should be shared among hundreds who contributed to his manpower-intensive work.

Giacconi said he was “dumbstruck” when Nobel officials phoned him at his Washington, D.C.,-area home at 5:30 a.m. and had since been fielding a steady stream of congratulatory calls. “It’s been a long day,” he said in a telephone interview, “but I’ve had worse.” He said his first thought was to use the Nobel money to pay for the education of his two grandchildren. “Given how the costs are rising, that might require the whole prize,” he joked.

Colleagues who knew the men were as quick to comment on their generosity and humanity as on their science. “My mother would have said of them: ‘They’re good people,’ ” Bahcall said. Added Lande of Davis: “He is helpful. He is imaginative. He creates excitement about everything around him.” Giacconi can be “intimidating, outspoken and demanding,” said his close collaborator Harvey Tananbaum, “but he has an incredible ability of enabling people to do the best work they’re capable of doing. I’m still thriving on it.”

The existence of neutrinos was first postulated in the 1930s. But their existence tormented the man who theorized them, Wolfgang Pauli, who at the time said: “I have done a terrible thing. I have postulated a particle that cannot be detected.”

With no electrical charge and possibly no mass at all, it seemed that neutrinos would forever remain elusive. Despite the poor odds, Davis thought he could trap them. To do so, he needed to build a detector deep underground so the experiment would not be contaminated by cosmic rays. Solar neutrinos would have no problems getting underground--interacting only weakly with matter, they pass through rock, dirt and human beings with equal ease.

To trap neutrinos, Davis and colleagues filled a portion of South Dakota’s Homestake gold mine with 100,000 gallons of dry-cleaning solvent. Neutrinos, he reasoned, would react with the chlorine in the cleaning fluid and produce radioactive argon atoms, which he could measure by releasing helium gas through the fluid to grab the argon.

The tactic worked, to the amazement of physicists everywhere. But in 30 years of collecting, the instrument detected just 2,000 argon atoms--far fewer than expected.

This led to an even greater mystery, known as the “solar neutrino problem.” Where were all the rest of the particles? Scientists theorized that neutrinos can flit between various forms--electron, muon and tau--during their eight-minute journey from the sun to Earth, and that Davis’ detector was only picking up one form of neutrino.

Koshiba and his collaborators confirmed and extended Davis’ work at the Kamiokande and later at the bigger Super-Kamiokande neutrino detectors, huge tanks of water buried beneath the Japanese Alps. When neutrinos from the sun and from supernovas passed through the tank, a tiny fraction of them interacted with atoms in the water and gave off a characteristic streak of blue light called Cerenkov radiation. The work showed that neutrinos did come in different flavors.

By showing that muon neutrinos had a different mass than tau neutrinos, they showed the particles were not massless wonders as stan- dard theories of physics had predicted. With a speck of mass each, the untold numbers of neutrinos that shoot through the universe now are thought to add heft to the big equation of what makes up the universe. They also add up to more problems for physicists trying to sort out the rest of the equation.

“That’s what we live for,” Bahcall said. “New cans of worms.”

The Italian-born Giacconi was 28 when he started working out the details of how to construct the X-ray telescope. Four decades later, X-ray astronomy is a branch of study on equal footing with traditional optical and radio astronomy.

“It’s not every day someone just starts a field from scratch,” said Tananbaum, who was in graduate school when Giacconi made his first discovery and now directs the Chandra X-ray Observatory, a powerful telescope the two men proposed in 1976.

Before Giacconi’s work, astronomers had viewed the universe as a stately, relatively quiet place. That’s largely because the violent explosions of X-ray radiation emitted from violent black holes and dying stars had been invisible.

“It gives us a different view of the universe, just as an X-ray gives a different view of the body,” said Giacconi, who still conducts research with Chandra and runs Associated Universities Inc., a nonprofit corporation that operates astronomical observatories.

X-ray astronomy allowed Giacconi to prove the existence of binary star systems and black holes, monsters that previously existed only in science fiction.

“A new, fantastic zoo of important and strange celestial bodies has been discovered and studied,” the Nobel committee said. “Today the universe seems much more remarkable than we believed 50 years ago.”