Written only a few years after the atomic bombs dropped on Hiroshima and Nagasaki ended World War II, Arthur C. Clarke’s “The Sentinel” contains several themes that would become common in Cold War science fiction. Reflecting a shared dread that humanity might entirely destroy itself through nuclear war, many authors viewed the advent of a nuclear era as being a universal rite of passage for any civilization. While harnessing nuclear reactions was considered necessary for scientific advancement, it also provided a means for planetary self-annihilation. All civilizations advancing to the level of nuclear weapons, therefore, must learn to transcend their base instincts. Only after successfully accomplishing this rite of passage, thus assuring the continuation of planetary life, can a race begin a new phase of space exploration and alien contact.

A second theme, first encountered in “The Sentinel” and appearing throughout much of Clarke’s later fiction, is the presence of a vastly superior civilization, one whose existence predates human civilization by unknown millennia. It is a patient race, observing the evolutionary development of more primitive species throughout the universe, presumably awaiting their maturation. Childlike humans, themselves only newly sentient, can only guess at the intention of the superior race, hoping it is benign rather than sinister. Even in their scientific investigations, humans are portrayed as childlike. When researchers cannot penetrate the protective force field, they resort to “the savage might of atomic power.” In other words, like children, they break it.

In “The Sentinel,” the intention of the superior race is unknown. Are they benevolent, or, because they are a very old race, will they be jealous of youth, as Wilson fears? The story closes forebodingly with humanity awaiting its first contact with the unknown advanced civilization.

“The Sentinel” contains the germ of an idea that would be further explored by Clarke and director Stanley Kubrick in the film 2001: A Space Odyssey (1968), and in Clarke’s novelization of the film that appeared in the same year. In 2001, not only does the superior race observe human evolution, but it also intervenes, benevolently guiding humanity to new evolutionary heights. Appearing at crucial junctures in human history, the film’s black obelisk, although vastly different from the small crystal pyramid of “The Sentinel,” is reminiscent of that earlier alien artifact. The final visual image in 2001, the human adult who turns into a fetus of a new super race through alien, god-like intervention is the ultimate expression of that metaphysical theme first suggested by “The Sentinel.”

In Against the Fall of Night (1953) and Childhood’s End (1953), considered by many to be two of his finest novels, Clarke further explores the theme of humanity awaiting guidance from an ancient extraterrestrial civilization. These novels continue a trend that began in “The Sentinel,” and would become a trademark of Clarke’s fiction.