After high school, Oppenheimer enrolled in Harvard University, where he studied literature, ancient Greek, and, of course, science. Unsure about what he wanted to do with his life, Oppenheimer hesitated when it came time to choose a major. Wavering between mineralogy and chemistry, he eventually settled upon the latter, taking the advice of a friend who had pointed out that a career in chemistry carried with it the promise of summer vacations.
Then, in his junior year, Oppenheimer discovered physics. And everything changed. Studying under the famous experimentalist Percy Bridgman, Oppenheimer immediately fell in love with the field. This, he decided, was what he wanted to do with the rest of his life.
Having taken ten courses per semester, Oppenheimer was able to graduate from Harvard in three years, and in 1926 he headed for England, in the hopes of pursuing a graduate degree in physics.
Most promising young physics students of this period tended to go abroad to complete their educations–the physics departments of the United States were no match for the powerhouse European laboratories. The 1920s was a particularly exciting time to practice physics, and Europe was the place to practice it.
Only a decade before, Einstein had overthrown the Newtonian conception of the universe that had reigned for centuries. His famous equation, E = mc2, was taking the world of physics–and beyond–by storm. Meanwhile, another revolutionary shift had taken place in the way scientists understood the structure of matter. A series of discoveries in the late nineteenth and early twentieth century established once and for all that all matter was made up of atoms–and that those atoms were themselves made up of a number of bizarrely acting subatomic particles. The discovery that the behavior of these subatomic particles couldn't be explained using existing models led to the formation of a new system of physics for describing the behavior of particles on this tiny scale: quantum physics. It seemed that new discoveries were being made every day, and it was understood among American physics students that the best and most exciting of these discoveries were taking place in European labs.
Oppenheimer applied for a position in the Cavendish Laboratory at Cambridge University, one of the best nuclear physics labs in the world. It was directed by Ernest Rutherford, a Nobel Prize winner who had only recently proved the existence of the nucleus of an atom and thus of an atom itself. Although Oppenheimer, with his degree in chemistry, was ill-prepared for a rigorous course of graduate study in experimental physics, Rutherford took a chance on the young scholar and admitted him to the lab.