The premise of “Oppenheimer,” Christopher Nolan’s biopic, is straightforward: tell the story of J. Robert Oppenheimer, the physicist known as the “father of the atomic bomb.” But, as with the director’s other movies, the execution is far from simple. The film skips between time periods, and it features a dizzying array of scientists, politicians and possible Communist agents amid a series of government hearings.

Here’s a guide to help you keep track of the real-life characters and events of the movie.

The American theoretical physicist (played by Cillian Murphy) spearheaded the development of the atomic bomb through the Manhattan Project.

Born in New York City in 1904, Oppenheimer spent his undergraduate years at Harvard before moving to Cambridge, England, for graduate work in physics. There, he grew frustrated with his tutor’s insistence that he focus on lab work instead of theory and is reported to have given the man, Patrick Blackett, a…