Their discovery raised a question: What is pushing the universe apart? Scientists have labelled it “dark energy,” but nobody knows what it is.
It's “an enigma, perhaps the greatest in physics today,” the Nobel committee said.
.... But Robert Kirshner, a Harvard astronomer who was part of the team that included his former students, Dr. Schmidt and Dr. 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, Dr. 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.”
Dr. 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.
Dr. 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 any more. I tell people it's the longest ‘Aha!’ experience that you've ever had.”