After learning that he’d won the Nobel Prize in Physics on October 8, James Peebles told the New York Times that the possibility had previously “crossed his mind.” If so, his was one of the few minds to have been so traversed.
That Peebles has made numerous contributions to cosmology—theories that have helped transform the field from metaphysics to physics—is indisputable. In the words of the announcement from the Royal Swedish Academy of Sciences, his half-share of this year’s physics prize “rewards new understanding of the universe’s structure and history.” That description, however, also hints at why his Nobel came as a surprise.
Usually the physics prize honors a particular achievement. Alfred Nobel stipulated, in his will establishing the prize, that the recipient be “the person who shall have made the most important discovery or invention within the field of physics” (italics mine). The other half of this year’s prize, to Michel Mayor and Didier Queloz, follows that tradition. It recognizes “the first discovery of a planet orbiting a solar-type star outside our solar system.” There it is: a singular coup of detection.
Not that the prize isn’t open to theorists such as Peebles. Peter Higgs, for instance, won the Nobel for predicting the existence of the boson that bears his name. But the honor, which came in 2013, had to wait until the validating discovery itself.
Peebles, too, has worked on theories anticipating discoveries that won the Nobel. In 1964, he was part of a team of Princeton theorists who predicted the existence of the cosmic microwave background—the present-day remnant of the primeval shockwaves emerging in a universe expanding after a so-called big bang. The simultaneous detection of that radiation was accidental; the Bell Labs astronomers Arno Penzias and Robert Woodrow Wilson didn’t know what they’d found until the Princeton theorists told them. Nonetheless, in 1978 Penzias and Wilson walked away with the Nobel for the discovery.
In the late 1960s, Peebles realized that the cosmic microwave background couldn’t be as smooth, as uniform, as Penzias and Wilson’s observations suggested. A fetal universe version of a universe full of matter and energy must have irregularities, minuscule variations that would grow into galaxies and planets and us. The principal investigators behind the 1992 detection of those anisotropies received the 2006 physics Nobel.
In the early 1970s, Peebles and his Princeton colleague Jeremiah Ostriker began investigating a mysterious anomaly that had begun appearing in observations of spiral galaxies: The gas and dust near the visible edge of the galaxies seemed to be rotating at virtually the same rate as the gas and dust near the center, as if Uranus were keeping pace with Mercury in a race around the sun. Peebles and Ostriker devised primitive computer simulations to recreate that effect, and they found that indeed they could—if they planted the galaxy inside a much larger giant halo of matter that would serve as a gravitational stabilizer. “There are reasons,” read the opening sentence of their resulting 1974 paper, “increasing in number and quality, to believe that the masses of ordinary galaxies may have been underestimated by a factor of 10 or more.”
“Just brilliant,” was how that sentence was characterized to me by the astronomer who had pioneered those galaxy detections, Vera Rubin. (When I passed along the compliment to Peebles, he answered with mock indignation, “She never said that to me!”) In the early 1980s, Peebles was among a group of theorists arguing that the existence of this “dark matter” would affect the large-scale structure of an expanding universe to such an extent that a countervailing gravitational effect would account for the universe’s stability. The discovery of that effect—the acceleration of the expansion of the universe due to a mysterious something-or-other that we call dark energy—came in 1998 and received the 2011 Nobel.
I’ve met Peebles a number of times over the past 20 years—usually in a journalistic setting (he figures prominently in my 2011 book The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality), occasionally in a social setting, and once in a somewhat amusing setting. We were in the same Amtrak car following his appearance at a “Nature of the Universe” event at the Smithsonian’s National Museum of Natural History. I introduced myself; we chatted briefly. Then I returned to my seat and marveled that the universe as we know it is so new that one of its creators could be sitting across the aisle from me, sipping a Budweiser.
Yet I’ve often left those encounters mildly lamenting that whatever in his personality had compelled him to work on so many problems would sabotage his chance at a Nobel. Peebles once described his scientific career to writer Ann K. Finkbeiner as “a random walk, no, an undirected walk, or rather a locally directed walk: As you take each step you decide where the next one is going to go”—a description that itself captures his peripatetic nature.
He has always loved identifying the next big problem, seeing where it leads, identifying that big problem, seeing where it leads: a bend-in-the-knees, wind-in-the-face rush into the future. (He is an expert downhill skier.) That approach can result in a breadth of accomplishments, but—while nobody would accuse Peebles’s work of lacking depth—that approach can also lead to the absence of one career-defining breakthrough.
The Academy of Motion Picture Arts and Sciences has a mechanism for correcting the historical record: an honorary Oscar for those who never won a “real” one—Alfred Hitchcock, or Deborah Kerr, or Peter O’Toole. The Royal Swedish Academy of Sciences does not. Or, perhaps more accurately, has not, until this year.
Prizes, of course, aren’t of paramount importance; they’re nice enough, I suppose. But if we’re going to have them, and if people are going to equate receiving one in particular with entering the scientific pantheon, then why should someone deserving to be in that pantheon not be there?
Because the guy whose money is funding it said so in his will is, I think, a reasonable response. But this year the physics committee decided it wasn’t reasonable enough—also, I think, a reasonable response: It’s their money now. I’m puzzled by it, and I’m curious to see what will happen in years to come. But mostly I’m happy for Jim Peebles.
This Bud’s for him.