Exposition is the use of explanatory information to inform the reader about details concerning character, setting, etc. that are important to the literary work. In science fiction, authors often portray realities that are significantly different from everyday life, making exposition a necessity. Clarke incorporates exposition in two ways: by describing places and objects that Marvin witnesses and by recounting the story that Marvin himself hears from his father. For instance, Clarke lets the reader know the story is set in the future by describing key features of the lunar colony such as the agricultural level, where food is grown in sealed domes.

Such exposition leaves much about the nature of life in the colony mysterious, which is in keeping with the narrative’s focus. The story is not ultimately about life on the Moon but rather about the loss of life on Earth and the desire to return to the planet, which is described in much more vibrant terms than the Moon even in its devastated state. Consequently, Earth is the subject of much more explicit exposition when Clarke summarizes the story that Marvin’s father tells to him.