Finding just three people to recognize often means looking for people who contributed just slightly more than others, Riess said. He compared Nobel-awarding to his work as a professor. At the end of the semester, he has to decide how to divide the top of the class into A and B grades. "You look for a natural break, but it doesn't always exist," he said. "This quandary isn't just in prizes. It's all facets of life." [The 9 Biggest Unsolved Mysteries in Physics]
While they might pretend otherwise sometimes, many scientists still care deeply about recognition. "Scientists are people, too," Riess said. Although each category's Nobel is worth about $1 million, Riess said, "It's not a money issue, generally. It's being able to identify yourself as being involved in work that was recognized as being important."
He would like to see more science awards that don't have a limit on the number of winners. He cited the Gruber Prize in cosmology, which has recognized groups, as an example. "It's a more modern view. That's the way science is done now," he said.
The Nobel Committee's Lidin does not think having multiple award winners is a problem. The Royal Swedish Academy of Sciences is allowed to award the science Nobels to groups, he said, just as the Nobel Peace Prize has gone to groups such as the Intergovernmental Panel on Climate Change in 2007 and the United Nations in 2001. The academy simply hasn't needed to award groups yet, he said.