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      Johns Hopkins professor Adam Riess shares Nobel Prize in physics

      WASHINGTON (AP) A Johns Hopkins University professor was one of a trio of scientists awarded the 2011 Nobel Prize in physics Tuesday for discovering that the universe is expanding at a faster and faster rate, contrary to science's conventional wisdom.

      The Royal Swedish Academy of Sciences announced that Adam Riess, an astronomy and physics professor at the university, won the prize with fellow American Saul Perlmutter and U.S.-Australian citizen Brian Schmidt. Perlmutter heads the Supernova Cosmology Project at the University of California, Berkeley. Schmidt is the head of the High-z Supernova Search Team at the Australian National University in Weston Creek, Australia

      The trio was honored "for the discovery of the accelerating expansion of the universe through observations of distant supernovae."

      Riess, 41, said he got a phone call around 5:30 a.m. Several Swedish men were on the line, at which point he "knew it wasn't Ikea," the Swedish furniture retailer. His "jaw dropped" when he heard the news, he said.

      "I'm dazed," he said in a telephone interview, adding that he couldn't believe he had won.

      The work Riess is being honored for stems from a 1998 discovery that the rate at which the universe is expanding is speeding up, a discovery Riess called "truly startling."

      The discovery contradicted conventional scientific wisdom that the universe's expansion would be slowing down as a result of what Riess calls the "gravitational glue" of the rest of the universe. The work led to the discovery of what's called dark energy, which is believed to be responsible for the universe's accelerating expansion, though researchers still don't know much about it.

      Riess, who has an undergraduate degree in physics MIT and a doctorate in astrophysics from Harvard, said he spends the last two classes of his introductory astronomy course at Johns Hopkins talking about the discovery. He tells students in his "Stars and the Universe" class that they are fortunate to have such an "exciting mystery" to help solve.

      "I sort of turn to them at that point and say I hope many of you continue on in this field and help us understand this mystery," he said.

      Riess said that as a child he loved science and wanted to study dinosaurs. He didn't use a telescope until graduate school, he said. He says he finds looking through a telescope awe inspiring.

      "Most of it's a mystery," he said of looking out at the universe. "If we very carefully study this ancient tired light we can get some clues as to what really is the universe."

      Riess said his "jaw dropped" when he got an early morning call at his home in Baltimore from a bunch of Swedish men and realized "it wasn't Ikea," the Swedish furniture retailer. "I'm dazed," he said.

      Working in two teams, with Perlmutter heading one, they had raced to measure the universe's expansion by analyzing light from dozens of exploding stars called supernovas. They found the light was weaker than expected, signaling that the expansion of the universe was accelerating.

      It was "one of the truly great discoveries in the history of science, and one whose implications are not fully understood," said Paul Steinhardt, a physics professor at Princeton University.

      One consequence of the finding is that in a trillion years, galaxies will be spread apart from each other by more than the current size of the universe, he said. And the ever-greater expansion rate means the light from one galaxy will no longer be visible from another as it is today, he said.

      "It's like changing from New York City to suddenly where everyone is spread out across some huge desert and there's nothing around to view," Steinhardt said.

      The rapid expansion also implies that the universe will get increasingly colder as matter spreads across ever-vaster distances in space, said Lars Bergstrom, secretary of the Nobel physics committee.

      The committee, citing the Robert Frost poem that pondered the world ending in fire or ice, suggested that "if the expansion will continue to speed up, the universe will end in ice."

      But Robert Kirshner, a Harvard astronomer who was part of the team that included his former students Schmidt and Riess, said scientists don't know enough about dark energy to predict what will happen to the universe hundreds of billions of years from now.

      One possibility is that the expansion will continue to accelerate, he said, "sort of like compound interest gone mad." It could even speed up so much that not only will galaxies fly apart from each other, but "stuff will really rip apart," even planets and atoms, he said. That's called the "big rip," "and I hope that's not our fate."

      On the other hand, Kirshner said, the expansion could halt and go into reverse, so the universe collapses back into itself, a fate sometimes called the "big crunch."

      With such uncertainty, he said, "it seems very important to learn more about what the dark energy is."

      Schmidt said he was just sitting down to have dinner with his family in Canberra, Australia, when the phone call came from the academy.

      "I was somewhat suspicious when the Swedish voice came on," Schmidt said. "My knees sort of went weak and I had to walk around and sort my senses out."

      Perlmutter said his team made the discovery in steps, analyzing the data and assuming it was wrong. "And after months, you finally believe it," he said. "It's not quite a surprise anymore. I tell people it's the longest `Aha!' experience that you've ever had."

      Fred Dylla, executive director of the American Institute of Physics, said the discovery confirmed an idea from Albert Einstein called the cosmological constant. Einstein included this in his general theory of relativity, a cornerstone of modern physics.

      The Nobel Prizes were established in the will of Swedish industrialist Alfred Nobel and have been awarded since 1901. The prizes are presented to the winners every year on Dec. 10, the anniversary of Nobel's death in 1896.