This year’s Nobel Prize in Physics honors the human desire to understand both the fundamental nature of the universe and its planetary particularities. Half of the $900,000 prize goes to Princeton University cosmologist James Peebles, for laying the foundations of modern-day cosmology and predicting the basic ingredients of the universe. The other half will be split between astronomers Michel Mayor and Didier Queloz. In 1995, at the University of Geneva in Switzerland, they discovered the first planet around another sunlike star—opening the floodgates to the discovery of thousands more exoplanets of every description.
Peebles’s many theoretical predictions have proved prescient. For starters, in 1965 he predicted the big bang nearly 14 billion years ago should have left an afterglow, radiation that would have stretched to microwave wavelengths as the universe expanded. That cosmic microwave background (CMB) was discovered the same year and has proved invaluable for deciphering the universe. “He was the guy in the early days,” says Joseph Silk, a cosmologist the University of Oxford in the United Kingdom. He “put the physics into cosmology.”
Others had suggested an afterglow; Peebles laid bare the details. He showed how its temperature is pinned down by the abundance of light elements in the cosmos. He also predicted that the sloshing interplay between radiation, ordinary matter, and dark matter—the invisible stuff that was already thought to hold the galaxies together—would cause the temperature of the CMB to vary from point to point across the sky. Those tiny fluctuations were eventually spotted by NASA’s Cosmic Background Explorer satellite, which launched in 1989.