Two teams who upset everyone’s ideas about how the universe works and its future will share the $500,000 Gruber Cosmology Prize for discovering that 70 percent of the universe is nothing but a strange form of energy.
In 1998, a group called the High-z Supernova Search Team published irresistible evidence that the universe is expanding at a rate that may never slow down. Eleven of the 19 members of the High-z team are or were affiliated with Harvard University. Months later, a second team, the Supernova Cosmology Project, independently confirmed the startling finding. That team was lead by Saul Perlmutter of the University of California, Berkeley.
“We used observations of distant and nearby exploding stars [supernovae] to discover that the expansion of the universe was not slowing down, as everyone thought, but speeding up,” says Robert Kirshner, Clowes Professor of Science and Harvard College Professor of Astronomy. “This astonishing result has now been confirmed by other methods of observation and in just nine years has gone from incredible to being the standard view.”
That “standard view” is still incredible. It means that everything we can see in the universe – all the trillions of stars, billions of galaxies, and no one knows how many planets – make up no more than 4-5 percent of the universe. Another 25 percent is dark matter, mysterious “stuff” that exerts a gravitational pull but can’t be seen or heard. The rest, and most, is dark energy, the effects of which can be detected but no one knows what it is doing exactly.
Its existence is firm enough, however, for the prestigious Peter and Patricia Gruber Foundation to give both teams its 2007 Cosmology Prize. According to the foundation, such awards are given for “groundbreaking work [that] provides new models that inspire and enable fundamental shifts in knowledge and culture.”
The $500,000 will be split in four parts. One goes to Brian Schmidt, who was working with Kirshner at Harvard in 1998 and now is an astronomer at the Australian National Observatory. One part goes to Perlmutter. Two other shares will be split among members of the two teams, a total of 51 people. The winners will receive their prizes at the University of Cambridge in England on Sept. 7.
The gravity of the situation
Back in 1997 both teams were trying to measure how fast the universe is expanding by measuring the movements of certain types of supernovae. Schmidt had just earned his Ph.D. and was leading the High-z team at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
When Adam Riess, another Ph.D. student, told them what the data were saying, “I could not believe it,” Kirshner recalls. “We made the team re-do the whole analysis. That’s when the horrible truth dawned on me. We had a result that was going to turn this field upside down. Instead of a universe ruled by gravity, the most important thing in the universe was a kind of antigravity, the dark energy. The whole thing seemed crazy.”
Nine more years of study after study showed it may be crazy but it’s true.
According to astronomers, the universe has been expanding since it came into existence some 14 billion years ago. The big mystery that they have been trying to solve is, how fast? Will the gravitational pull of stars and galaxies on each other eventually stop the expansion and pull the universe together, ending it in a gigantic crunch? Or, will the universe go on expanding until it is nothing but nothing?
The discovery of dark energy doesn’t settle the question of the universe’s future because nobody knows what it really is or what it will do.
Reiss, now at the Space Telescope Science Institute in Baltimore, has an interesting take on the mystery. “We’ve never tested gravity across the whole universe,” he told a news conference last year. “It may be that there’s not really dark energy, that it’s a figment of our misperception about gravity, that gravity changes the way it operates on long ranges.”
Perlmutter is more pleased than frustrated about the condition of the universe. “You want your mind to be boggled,” he said. “That’s a pleasure in and of itself.
Kirshner is more pragmatic. He says, “We’ve got a lot of work still to do.”
For more information, see Kirshner’s book, “The Extravagant Universe, Exploding Stars, Dark Energy, and the Accelerating Cosmos,” (Princeton University, 2004).