As a postdoctoral researcher after completing his Ph.D. in physics at MIT in 1971, Alan Guth worked mostly on abstract mathematical problems in the theory of elementary particles. While at Cornell, he was persuaded by fellow postdoc Henry Tye to collaborate on work that would change the direction of Guth's career. The two found that standard assumptions in particle physics and cosmology would lead to a fantastic overproduction of magnetic monopoles. From the search for alternatives came Guth's modification of the big bang theory, the inflationary universe. Since returning to MIT as an associate professor in 1980, Guth has refined the inflationary model through interactions with theorists in particle physics, string theory, relativity and quantum mechanics as well as evidence from astronomy and cosmology. He has been elected to the National Academy of Sciences and the American Academy of Arts and Sciences, and has been awarded the MIT School of Science Prize for Undergraduate Teaching, the Franklin Medal for Physics of the Franklin Institute, and the Dirac Prize of the Abdus Salam International Center for Theoretical Physics. In addition to holding a named professorship, he is a Margaret MacVicar Faculty Fellow at MIT.