Jens Larssen (d. 1944) was an American nuclear physicist of Norwegian descent, working on the development of an atomic bomb with the University of Chicago's Metallurgical Laboratory at the time of the invasion of the Race's Conquest Fleet. He was witness to the "High altitude bombing" on the University campus. Sam Yeager later told his son Jonathan of how he met Barbara, and Jens Larssen's end. He was ashamed for being partly responsible for ruining Jens' life. Sam also stated that Barbara also felt guilty about Jens' fate and had tried her best to forget him.