Nobel-winning discovery on universe has Harvard roots
The Nobel Prize in physics was awarded yesterday for the surprising discovery that the universe’s expansion is speeding up, not slowing down, a finding that has transformed scientists’ understanding of the universe and has deep roots at Harvard University.
In the run-up to the discovery in 1998, the effort to determine the universe’s rate of expansion became a high-stakes race between two rival teams, one based at the Lawrence Berkeley National Laboratory and the other an international team with strong local ties. Two of the Nobelists - Brian Schmidt of Australian National University and Adam Riess of Johns Hopkins University in Baltimore - were graduate students at Harvard.
It is in Cambridge where they did their scientific training and got started on the work that would ultimately build to their Nobel, working with Robert Kirshner, a Harvard professor and member of the High-Z Supernova Search Team that made the discovery, though he did not share in the prize. Riess and Schmidt will each receive a quarter of the $1.4 million prize, while Saul Perlmutter, an astrophysicist at Berkeley and a Harvard graduate, will receive half.
“I think it would be great if the Nobel prize could go to entire teams of people, because it’s really a lot of teamwork that allows these projects to succeed,’’ Riess said during a press conference. “If you want to know how science is really done and how recognition is doled out - I think it should be the whole team. I wish that could be true.’’
Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics who advised both students and played a role in the then-startling discovery that the universe’s expansion was accelerating, said that he had heard from both of them already and that he hoped to attend the award ceremony.
“This is very good; now we don’t have to wait anymore,’’ Kirshner said in an interview. “It was a good choice. I want to go to Stockholm; I’m keeping December open.’’
Since 1929, scientists have known that the universe is expanding, as a result of the Big Bang nearly 14 billion years ago. But astronomers thought that the expansion was slowing down because of gravity, although there was vigorous debate about how fast that was happening.
Scientists began to use the brightness of exploding stars, called supernovae, as a measurement of the rate of expansion. Initial results from the rival team in California in 1996 seemed to square with people’s expectations: The universe’s expansion was slowing down.
“They said the universe looks like it’s slowing down, just the way everybody expected,’’ Kirshner said. “We thought we’ve worked on supernovae a lot. . . . If we only knew how to find the distant ones, we can do that. I said - the other guys have been working for five years. Brian said we could do this. . . . He said, ‘I could do it in a month.’ It was partly youthful exuberance, but also true. He did have something working in a month.’’
Over the course of the research, Schmidt, who led the team, moved to Australia, and Riess moved to Berkeley. But they continued working with other team members, on results that they initially thought could not be right. The supernovae appeared dimmer than expected, suggesting that the universe’s expansion was speeding up, not slowing down.
As a graduate student in the 1990s, Riess had written his doctoral thesis on devising ways to measure the distance and brightness of supernovae to account for whether a star was dim because it was actually that dim; because it was far away; or because its light was being obscured by dust.
“That was one of the techniques that allowed us to have the confidence in our results, that we weren’t fooled by one of the other effects, that it was the universe accelerating,’’ Riess said.
Alan Guth, a physics professor at MIT, said that the finding went against the prevailing understanding of the universe.
“It was a big shock,’’ Guth said. “We did not expect it, and it really has dramatically changed both our view of cosmology and, perhaps even more important, our understanding, or the lack of it, of fundamental physics itself.’’
Riess, who played games of “mud football’’ with some of his peers on the Perlmutter team in California, said that competition helped move the work forward because it was becoming clear in early 1998 that the rival team had concurrently been finding its own evidence that the universe’s expansion was accelerating.
Riess said many questions remain to be explored, such as understanding the nature of dark energy, the mysterious energy that has been proposed as the cause for the acceleration and is thought to make up most of the universe.
“I spent a lot of years in Boston, so I got to see a lot of collapses,’’ he said. “I think nothing ever takes the sting out of those.’’