Currently, science fiction is a cultural obsession. Franchises like Star Wars and Alien—and, on television, Star Trek and Doctor Who—have millions of devoted fans who attend conferences, run websites, and feel passionate about their favorites. The purpose of this book is not to list the greatest or the most popular sci-fi titles, but to highlight some of the movies that have embedded themselves in the depths of our minds, coloring our view of day-to-day reality and fueling a few dreams—and nightmares—along the way. The visual exploration of innovative ideas in these films has shaped our pop-culture past and informed our contemporary society. The hauntingly beautiful metallic android tied to a burning stake in Metropolis (1927). The lumbering silver robot carrying Patricia Neal into the spaceship in The Day the Earth Stood Still (1951). The hypnotic yellow pupil in the center of HAL 9000’s unblinking red light in 2001: A Space Odyssey (1968). A bald Keanu Reeves waking up in a fluid-filled pod in The Matrix (1999). These are the images that remain fixed in our minds after the screen fades to black. These are the films that confront us with questions, answer a few, and prompt us to ask ourselves even more when the end credits roll. These are the essentials.

As you read about and watch these fifty movies, try to seek out their common threads. It can be a challenge, but I believe you’ll discover, as I did, that they are all similar in one way: once seen, they cannot be forgotten.