Guth’s Grand Guess: ‘In December 1979 Guth, then 32 and an obscure physicist at the Stanford Linear Accelerator Center, emerged as the first scientist to offer a plausible description of the universe when it was less than one-hundredth of a second old. During an unimaginably explosive period between 10-37 second and 10-34 second after its birth, Guth said, the universe expanded at a rate that kept doubling before beginning to settle down to the more sedate expansion originally described by the Big Bang theory.

Guth’s theory of inflation—the name he coined for this superfast early-universe expansion—has since vanquished every theoretical challenge and grown stronger with each new cosmological finding, including the latest, largest one: that the universe’s expansion rate, long thought to be slowing, is actually accelerating. “There’s no competition, but that’s not for lack of trying,” says cosmologist Alexander Vilenkin of Tufts University. “Many people have tried to develop a model that addresses the same problems, and they have failed.” Guth’s reputation has ascended with the theory: He has gone from an underemployed postdoc to cosmology’s leading man. In April of last year, he received the Benjamin Franklin Medal in physics, often a precursor to the Nobel Prize.’ Discover