This book argues that time travel fiction is a narrative "laboratory," a setting for thought experiments in which essential theoretical questions about storytelling--and by extension, about the philosophy of temporality, history, and subjectivity--are represented in the form of literal devices and plots. Drawing on physics, philosophy, narrative theory, psychoanalysis, and film theory, the book links innovations in time travel fiction to specific shifts in the popularization of science, from evolutionary biology in the late 1800s, through relativity and quantum physics in the mid-twentieth century, to more recent "multiverse" cosmologies. Wittenberg shows how increasing awareness of new scientific models leads to surprising innovations in the literary "time machine," which evolves from a "vehicle" used chiefly for sociopolitical commentary into a psychological and narratological device capable of exploring with great sophistication the temporal structure and significance of subjects, viewpoints, and historical events.