Summary

One in this series of science documentaries. This program follows famous musician Mark Oliver Everett as he delves into the life and work of his late father, renowned physicist Hugh Everett III. Mark, founder and frontman of the rock band Eels, explains that he and his father had little to no emotional relationship, grimly noting that their only moment of "intimacy" was when a 19-year-old Mark found him dead of a heart attack in 1982. Admitting that he has no aptitude for math or science, Mark sets out to understand his father's theory of parallel universes, publicized only late in his life, and his apparent abandonment of academia later in life – observing that, according to Everett, there is another "version" of him that does not go on the trip. He first heads to his father's hometown in Virginia, where Don Reisler describes meeting his "peculiar" friend and colleague Everett in 1970. Reisler gives Mark a crash course in the basics of atomic structure, noting that Everett would have been proud of his son's musical accomplishments.

Next, Mark heads to Princeton University, where Everett switched from mathematics to quantum mechanics at the behest of Professor John Wheeler. A technician shows Mark the "double slit" experiment, which demonstrates how photons can be in two places simultaneously and prompted Everett to wonder if the same was not possible of humans. Everett came to disagree with the widely accepted Copenhagen interpretation put forth by famed scientist Niels Bohr, which essentially states that an observer is required for a quantum event to exist, and he discussed the matter with his colleagues over many "sherry meetings." Mark observes the dorm room in which his father lived and worked in the 1950s, and physicist Max Tegmark, an admirer of Everett's, explains that Erwin Schrödinger also disagreed with Bohr and formulated his famous (and strictly theoretical) cat experiment, in which an animal sealed in a box with a deadly substance is considered to be simultaneously alive and dead.

At the age of only 24, Everett determined his parallel universes theory, arguing that any significant event causes a cosmic "splitting" in which multiple possibilities are simultaneously true (meaning there is a universe in which the cat is dead and also one in which it is alive). Mark explores Princeton's archives and reads his father's 1957 dissertation, learning that Wheeler arranged for Everett to travel to Europe in 1959 and debate the matter with Bohr face-to-face. Unfortunately, Bohr did not change his mind, and the Copenhagen interpretation remained the predominant theory in quantum mechanics, with Everett's astounding revelation more or less tossed aside. Mark realizes that this huge disappointment largely contributed to his father's distant emotional state and heavy drinking and smoking habits, adding that his mother also suffered from mental illness and his older sister died by suicide in 1996, saying that she hoped to reunite with her father in a parallel world.

Mark reflects that he now feels closer to his father upon learning of his ahead-of-its-time work, though admits that he has never sorted through his father's belongings. Everett biographer Peter Byrne arrives to help with the task, and they find a quantity of handwritten notes and tape recordings, though few photos and no videos. Mark later visits the Pentagon, where his father worked in military science during the Cold War after leaving the academic world, and colleague George Pugh states that his and Everett's research into the catastrophic effect of nuclear fallout made a positive impression on Eisenhower. Everett later became the president of a private company specializing in "war games," though by the late 1970s, his parallel-universe theory became more popular in both academia and science fiction. He began giving lectures on the subject, but his validation was short-lived, as he died in 1982 at only 51 years of age.

Mark repairs some damaged audio tapes from his father's belongings and confesses his nervousness about hearing his dad's voice for the first time in decades. Noting that Everett does not sound "bitter" about the state of his career, he is amused to hear his own younger self making playful comments. He reflects on the "other him" that did not embark on the journey to find his father, deciding that he is glad to have gotten to know him better.